1 /* Global common subexpression elimination/Partial redundancy elimination
2 and global constant/copy propagation for GNU compiler.
3 Copyright (C) 1997, 1998, 1999 Free Software Foundation, Inc.
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GNU CC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
23 - reordering of memory allocation and freeing to be more space efficient
24 - do rough calc of how many regs are needed in each block, and a rough
25 calc of how many regs are available in each class and use that to
26 throttle back the code in cases where RTX_COST is minimal.
27 - dead store elimination
28 - a store to the same address as a load does not kill the load if the
29 source of the store is also the destination of the load. Handling this
30 allows more load motion, particularly out of loops.
31 - ability to realloc sbitmap vectors would allow one initial computation
32 of reg_set_in_block with only subsequent additions, rather than
33 recomputing it for each pass
37 /* References searched while implementing this.
39 Compilers Principles, Techniques and Tools
43 Global Optimization by Suppression of Partial Redundancies
45 communications of the acm, Vol. 22, Num. 2, Feb. 1979
47 A Portable Machine-Independent Global Optimizer - Design and Measurements
49 Stanford Ph.D. thesis, Dec. 1983
51 A Fast Algorithm for Code Movement Optimization
53 SIGPLAN Notices, Vol. 23, Num. 10, Oct. 1988
55 A Solution to a Problem with Morel and Renvoise's
56 Global Optimization by Suppression of Partial Redundancies
57 K-H Drechsler, M.P. Stadel
58 ACM TOPLAS, Vol. 10, Num. 4, Oct. 1988
60 Practical Adaptation of the Global Optimization
61 Algorithm of Morel and Renvoise
63 ACM TOPLAS, Vol. 13, Num. 2. Apr. 1991
65 Efficiently Computing Static Single Assignment Form and the Control
67 R. Cytron, J. Ferrante, B.K. Rosen, M.N. Wegman, and F.K. Zadeck
68 ACM TOPLAS, Vol. 13, Num. 4, Oct. 1991
71 J. Knoop, O. Ruthing, B. Steffen
72 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
74 What's In a Region? Or Computing Control Dependence Regions in Near-Linear
75 Time for Reducible Flow Control
77 ACM Letters on Programming Languages and Systems,
78 Vol. 2, Num. 1-4, Mar-Dec 1993
80 An Efficient Representation for Sparse Sets
81 Preston Briggs, Linda Torczon
82 ACM Letters on Programming Languages and Systems,
83 Vol. 2, Num. 1-4, Mar-Dec 1993
85 A Variation of Knoop, Ruthing, and Steffen's Lazy Code Motion
86 K-H Drechsler, M.P. Stadel
87 ACM SIGPLAN Notices, Vol. 28, Num. 5, May 1993
89 Partial Dead Code Elimination
90 J. Knoop, O. Ruthing, B. Steffen
91 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
93 Effective Partial Redundancy Elimination
94 P. Briggs, K.D. Cooper
95 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
97 The Program Structure Tree: Computing Control Regions in Linear Time
98 R. Johnson, D. Pearson, K. Pingali
99 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
101 Optimal Code Motion: Theory and Practice
102 J. Knoop, O. Ruthing, B. Steffen
103 ACM TOPLAS, Vol. 16, Num. 4, Jul. 1994
105 The power of assignment motion
106 J. Knoop, O. Ruthing, B. Steffen
107 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
109 Global code motion / global value numbering
111 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
113 Value Driven Redundancy Elimination
115 Rice University Ph.D. thesis, Apr. 1996
119 Massively Scalar Compiler Project, Rice University, Sep. 1996
121 High Performance Compilers for Parallel Computing
125 Advanced Compiler Design and Implementation
127 Morgan Kaufmann, 1997
129 Building an Optimizing Compiler
133 People wishing to speed up the code here should read:
134 Elimination Algorithms for Data Flow Analysis
135 B.G. Ryder, M.C. Paull
136 ACM Computing Surveys, Vol. 18, Num. 3, Sep. 1986
138 How to Analyze Large Programs Efficiently and Informatively
139 D.M. Dhamdhere, B.K. Rosen, F.K. Zadeck
140 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
142 People wishing to do something different can find various possibilities
143 in the above papers and elsewhere.
153 #include "hard-reg-set.h"
156 #include "insn-config.h"
158 #include "basic-block.h"
160 #include "function.h"
164 #define obstack_chunk_alloc gmalloc
165 #define obstack_chunk_free free
167 /* Maximum number of passes to perform. */
170 /* Propagate flow information through back edges and thus enable PRE's
171 moving loop invariant calculations out of loops.
173 Originally this tended to create worse overall code, but several
174 improvements during the development of PRE seem to have made following
175 back edges generally a win.
177 Note much of the loop invariant code motion done here would normally
178 be done by loop.c, which has more heuristics for when to move invariants
179 out of loops. At some point we might need to move some of those
180 heuristics into gcse.c. */
181 #define FOLLOW_BACK_EDGES 1
183 /* We support GCSE via Partial Redundancy Elimination. PRE optimizations
184 are a superset of those done by GCSE.
186 We perform the following steps:
188 1) Compute basic block information.
190 2) Compute table of places where registers are set.
192 3) Perform copy/constant propagation.
194 4) Perform global cse.
196 5) Perform another pass of copy/constant propagation.
198 Two passes of copy/constant propagation are done because the first one
199 enables more GCSE and the second one helps to clean up the copies that
200 GCSE creates. This is needed more for PRE than for Classic because Classic
201 GCSE will try to use an existing register containing the common
202 subexpression rather than create a new one. This is harder to do for PRE
203 because of the code motion (which Classic GCSE doesn't do).
205 Expressions we are interested in GCSE-ing are of the form
206 (set (pseudo-reg) (expression)).
207 Function want_to_gcse_p says what these are.
209 PRE handles moving invariant expressions out of loops (by treating them as
210 partially redundant).
212 Eventually it would be nice to replace cse.c/gcse.c with SSA (static single
213 assignment) based GVN (global value numbering). L. T. Simpson's paper
214 (Rice University) on value numbering is a useful reference for this.
216 **********************
218 We used to support multiple passes but there are diminishing returns in
219 doing so. The first pass usually makes 90% of the changes that are doable.
220 A second pass can make a few more changes made possible by the first pass.
221 Experiments show any further passes don't make enough changes to justify
224 A study of spec92 using an unlimited number of passes:
225 [1 pass] = 1208 substitutions, [2] = 577, [3] = 202, [4] = 192, [5] = 83,
226 [6] = 34, [7] = 17, [8] = 9, [9] = 4, [10] = 4, [11] = 2,
227 [12] = 2, [13] = 1, [15] = 1, [16] = 2, [41] = 1
229 It was found doing copy propagation between each pass enables further
232 PRE is quite expensive in complicated functions because the DFA can take
233 awhile to converge. Hence we only perform one pass. Macro MAX_PASSES can
234 be modified if one wants to experiment.
236 **********************
238 The steps for PRE are:
240 1) Build the hash table of expressions we wish to GCSE (expr_hash_table).
242 2) Perform the data flow analysis for PRE.
244 3) Delete the redundant instructions
246 4) Insert the required copies [if any] that make the partially
247 redundant instructions fully redundant.
249 5) For other reaching expressions, insert an instruction to copy the value
250 to a newly created pseudo that will reach the redundant instruction.
252 The deletion is done first so that when we do insertions we
253 know which pseudo reg to use.
255 Various papers have argued that PRE DFA is expensive (O(n^2)) and others
256 argue it is not. The number of iterations for the algorithm to converge
257 is typically 2-4 so I don't view it as that expensive (relatively speaking).
259 PRE GCSE depends heavily on the second CSE pass to clean up the copies
260 we create. To make an expression reach the place where it's redundant,
261 the result of the expression is copied to a new register, and the redundant
262 expression is deleted by replacing it with this new register. Classic GCSE
263 doesn't have this problem as much as it computes the reaching defs of
264 each register in each block and thus can try to use an existing register.
266 **********************
268 A fair bit of simplicity is created by creating small functions for simple
269 tasks, even when the function is only called in one place. This may
270 measurably slow things down [or may not] by creating more function call
271 overhead than is necessary. The source is laid out so that it's trivial
272 to make the affected functions inline so that one can measure what speed
273 up, if any, can be achieved, and maybe later when things settle things can
276 Help stamp out big monolithic functions! */
278 /* GCSE global vars. */
281 static FILE *gcse_file
;
283 /* Note whether or not we should run jump optimization after gcse. We
284 want to do this for two cases.
286 * If we changed any jumps via cprop.
288 * If we added any labels via edge splitting. */
290 static int run_jump_opt_after_gcse
;
292 /* Bitmaps are normally not included in debugging dumps.
293 However it's useful to be able to print them from GDB.
294 We could create special functions for this, but it's simpler to
295 just allow passing stderr to the dump_foo fns. Since stderr can
296 be a macro, we store a copy here. */
297 static FILE *debug_stderr
;
299 /* An obstack for our working variables. */
300 static struct obstack gcse_obstack
;
302 /* Non-zero for each mode that supports (set (reg) (reg)).
303 This is trivially true for integer and floating point values.
304 It may or may not be true for condition codes. */
305 static char can_copy_p
[(int) NUM_MACHINE_MODES
];
307 /* Non-zero if can_copy_p has been initialized. */
308 static int can_copy_init_p
;
314 /* Hash table of expressions. */
318 /* The expression (SET_SRC for expressions, PATTERN for assignments). */
320 /* Index in the available expression bitmaps. */
322 /* Next entry with the same hash. */
323 struct expr
*next_same_hash
;
324 /* List of anticipatable occurrences in basic blocks in the function.
325 An "anticipatable occurrence" is one that is the first occurrence in the
326 basic block, the operands are not modified in the basic block prior
327 to the occurrence and the output is not used between the start of
328 the block and the occurrence. */
329 struct occr
*antic_occr
;
330 /* List of available occurrence in basic blocks in the function.
331 An "available occurrence" is one that is the last occurrence in the
332 basic block and the operands are not modified by following statements in
333 the basic block [including this insn]. */
334 struct occr
*avail_occr
;
335 /* Non-null if the computation is PRE redundant.
336 The value is the newly created pseudo-reg to record a copy of the
337 expression in all the places that reach the redundant copy. */
341 /* Occurrence of an expression.
342 There is one per basic block. If a pattern appears more than once the
343 last appearance is used [or first for anticipatable expressions]. */
347 /* Next occurrence of this expression. */
349 /* The insn that computes the expression. */
351 /* Non-zero if this [anticipatable] occurrence has been deleted. */
353 /* Non-zero if this [available] occurrence has been copied to
355 /* ??? This is mutually exclusive with deleted_p, so they could share
360 /* Expression and copy propagation hash tables.
361 Each hash table is an array of buckets.
362 ??? It is known that if it were an array of entries, structure elements
363 `next_same_hash' and `bitmap_index' wouldn't be necessary. However, it is
364 not clear whether in the final analysis a sufficient amount of memory would
365 be saved as the size of the available expression bitmaps would be larger
366 [one could build a mapping table without holes afterwards though].
367 Someday I'll perform the computation and figure it out.
370 /* Total size of the expression hash table, in elements. */
371 static int expr_hash_table_size
;
373 This is an array of `expr_hash_table_size' elements. */
374 static struct expr
**expr_hash_table
;
376 /* Total size of the copy propagation hash table, in elements. */
377 static int set_hash_table_size
;
379 This is an array of `set_hash_table_size' elements. */
380 static struct expr
**set_hash_table
;
382 /* Mapping of uids to cuids.
383 Only real insns get cuids. */
384 static int *uid_cuid
;
386 /* Highest UID in UID_CUID. */
389 /* Get the cuid of an insn. */
390 #define INSN_CUID(INSN) (uid_cuid[INSN_UID (INSN)])
392 /* Number of cuids. */
395 /* Mapping of cuids to insns. */
396 static rtx
*cuid_insn
;
398 /* Get insn from cuid. */
399 #define CUID_INSN(CUID) (cuid_insn[CUID])
401 /* Maximum register number in function prior to doing gcse + 1.
402 Registers created during this pass have regno >= max_gcse_regno.
403 This is named with "gcse" to not collide with global of same name. */
404 static int max_gcse_regno
;
406 /* Maximum number of cse-able expressions found. */
408 /* Maximum number of assignments for copy propagation found. */
411 /* Table of registers that are modified.
412 For each register, each element is a list of places where the pseudo-reg
415 For simplicity, GCSE is done on sets of pseudo-regs only. PRE GCSE only
416 requires knowledge of which blocks kill which regs [and thus could use
417 a bitmap instead of the lists `reg_set_table' uses].
419 `reg_set_table' and could be turned into an array of bitmaps
421 [however perhaps it may be useful to keep the data as is].
422 One advantage of recording things this way is that `reg_set_table' is
423 fairly sparse with respect to pseudo regs but for hard regs could be
424 fairly dense [relatively speaking].
425 And recording sets of pseudo-regs in lists speeds
426 up functions like compute_transp since in the case of pseudo-regs we only
427 need to iterate over the number of times a pseudo-reg is set, not over the
428 number of basic blocks [clearly there is a bit of a slow down in the cases
429 where a pseudo is set more than once in a block, however it is believed
430 that the net effect is to speed things up]. This isn't done for hard-regs
431 because recording call-clobbered hard-regs in `reg_set_table' at each
432 function call can consume a fair bit of memory, and iterating over hard-regs
433 stored this way in compute_transp will be more expensive. */
435 typedef struct reg_set
{
436 /* The next setting of this register. */
437 struct reg_set
*next
;
438 /* The insn where it was set. */
441 static reg_set
**reg_set_table
;
442 /* Size of `reg_set_table'.
443 The table starts out at max_gcse_regno + slop, and is enlarged as
445 static int reg_set_table_size
;
446 /* Amount to grow `reg_set_table' by when it's full. */
447 #define REG_SET_TABLE_SLOP 100
449 /* Bitmap containing one bit for each register in the program.
450 Used when performing GCSE to track which registers have been set since
451 the start of the basic block. */
452 static sbitmap reg_set_bitmap
;
454 /* For each block, a bitmap of registers set in the block.
455 This is used by expr_killed_p and compute_transp.
456 It is computed during hash table computation and not by compute_sets
457 as it includes registers added since the last pass (or between cprop and
458 gcse) and it's currently not easy to realloc sbitmap vectors. */
459 static sbitmap
*reg_set_in_block
;
461 /* For each block, non-zero if memory is set in that block.
462 This is computed during hash table computation and is used by
463 expr_killed_p and compute_transp.
464 ??? Handling of memory is very simple, we don't make any attempt
465 to optimize things (later).
466 ??? This can be computed by compute_sets since the information
468 static char *mem_set_in_block
;
470 /* Various variables for statistics gathering. */
472 /* Memory used in a pass.
473 This isn't intended to be absolutely precise. Its intent is only
474 to keep an eye on memory usage. */
475 static int bytes_used
;
476 /* GCSE substitutions made. */
477 static int gcse_subst_count
;
478 /* Number of copy instructions created. */
479 static int gcse_create_count
;
480 /* Number of constants propagated. */
481 static int const_prop_count
;
482 /* Number of copys propagated. */
483 static int copy_prop_count
;
485 /* These variables are used by classic GCSE.
486 Normally they'd be defined a bit later, but `rd_gen' needs to
487 be declared sooner. */
489 /* A bitmap of all ones for implementing the algorithm for available
490 expressions and reaching definitions. */
491 /* ??? Available expression bitmaps have a different size than reaching
492 definition bitmaps. This should be the larger of the two, however, it
493 is not currently used for reaching definitions. */
494 static sbitmap u_bitmap
;
496 /* Each block has a bitmap of each type.
497 The length of each blocks bitmap is:
499 max_cuid - for reaching definitions
500 n_exprs - for available expressions
502 Thus we view the bitmaps as 2 dimensional arrays. i.e.
503 rd_kill[block_num][cuid_num]
504 ae_kill[block_num][expr_num]
507 /* For reaching defs */
508 static sbitmap
*rd_kill
, *rd_gen
, *reaching_defs
, *rd_out
;
510 /* for available exprs */
511 static sbitmap
*ae_kill
, *ae_gen
, *ae_in
, *ae_out
;
513 /* Objects of this type are passed around by the null-pointer check
515 struct null_pointer_info
{
516 /* The basic block being processed. */
518 /* The first register to be handled in this pass. */
520 /* One greater than the last register to be handled in this pass. */
522 sbitmap
*nonnull_local
;
523 sbitmap
*nonnull_killed
;
526 static void compute_can_copy
PROTO ((void));
528 static char *gmalloc
PROTO ((unsigned int));
529 static char *grealloc
PROTO ((char *, unsigned int));
530 static char *gcse_alloc
PROTO ((unsigned long));
531 static void alloc_gcse_mem
PROTO ((rtx
));
532 static void free_gcse_mem
PROTO ((void));
533 static void alloc_reg_set_mem
PROTO ((int));
534 static void free_reg_set_mem
PROTO ((void));
535 static int get_bitmap_width
PROTO ((int, int, int));
536 static void record_one_set
PROTO ((int, rtx
));
537 static void record_set_info
PROTO ((rtx
, rtx
, void *));
538 static void compute_sets
PROTO ((rtx
));
540 static void hash_scan_insn
PROTO ((rtx
, int, int));
541 static void hash_scan_set
PROTO ((rtx
, rtx
, int));
542 static void hash_scan_clobber
PROTO ((rtx
, rtx
));
543 static void hash_scan_call
PROTO ((rtx
, rtx
));
544 static int want_to_gcse_p
PROTO ((rtx
));
545 static int oprs_unchanged_p
PROTO ((rtx
, rtx
, int));
546 static int oprs_anticipatable_p
PROTO ((rtx
, rtx
));
547 static int oprs_available_p
PROTO ((rtx
, rtx
));
548 static void insert_expr_in_table
PROTO ((rtx
, enum machine_mode
,
550 static void insert_set_in_table
PROTO ((rtx
, rtx
));
551 static unsigned int hash_expr
PROTO ((rtx
, enum machine_mode
,
553 static unsigned int hash_expr_1
PROTO ((rtx
, enum machine_mode
, int *));
554 static unsigned int hash_set
PROTO ((int, int));
555 static int expr_equiv_p
PROTO ((rtx
, rtx
));
556 static void record_last_reg_set_info
PROTO ((rtx
, int));
557 static void record_last_mem_set_info
PROTO ((rtx
));
558 static void record_last_set_info
PROTO ((rtx
, rtx
, void *));
559 static void compute_hash_table
PROTO ((int));
560 static void alloc_set_hash_table
PROTO ((int));
561 static void free_set_hash_table
PROTO ((void));
562 static void compute_set_hash_table
PROTO ((void));
563 static void alloc_expr_hash_table
PROTO ((int));
564 static void free_expr_hash_table
PROTO ((void));
565 static void compute_expr_hash_table
PROTO ((void));
566 static void dump_hash_table
PROTO ((FILE *, const char *, struct expr
**,
568 static struct expr
*lookup_expr
PROTO ((rtx
));
569 static struct expr
*lookup_set
PROTO ((int, rtx
));
570 static struct expr
*next_set
PROTO ((int, struct expr
*));
571 static void reset_opr_set_tables
PROTO ((void));
572 static int oprs_not_set_p
PROTO ((rtx
, rtx
));
573 static void mark_call
PROTO ((rtx
));
574 static void mark_set
PROTO ((rtx
, rtx
));
575 static void mark_clobber
PROTO ((rtx
, rtx
));
576 static void mark_oprs_set
PROTO ((rtx
));
578 static void alloc_cprop_mem
PROTO ((int, int));
579 static void free_cprop_mem
PROTO ((void));
580 static void compute_transp
PROTO ((rtx
, int, sbitmap
*, int));
581 static void compute_transpout
PROTO ((void));
582 static void compute_local_properties
PROTO ((sbitmap
*, sbitmap
*,
584 static void compute_cprop_avinout
PROTO ((void));
585 static void compute_cprop_data
PROTO ((void));
586 static void find_used_regs
PROTO ((rtx
));
587 static int try_replace_reg
PROTO ((rtx
, rtx
, rtx
));
588 static struct expr
*find_avail_set
PROTO ((int, rtx
));
589 static int cprop_jump
PROTO((rtx
, rtx
, struct reg_use
*, rtx
));
591 static int cprop_cc0_jump
PROTO((rtx
, struct reg_use
*, rtx
));
593 static int cprop_insn
PROTO ((rtx
, int));
594 static int cprop
PROTO ((int));
595 static int one_cprop_pass
PROTO ((int, int));
597 static void alloc_pre_mem
PROTO ((int, int));
598 static void free_pre_mem
PROTO ((void));
599 static void compute_pre_data
PROTO ((void));
600 static int pre_expr_reaches_here_p
PROTO ((int, struct expr
*,
602 static void insert_insn_end_bb
PROTO ((struct expr
*, int, int));
603 static void pre_insert_copy_insn
PROTO ((struct expr
*, rtx
));
604 static void pre_insert_copies
PROTO ((void));
605 static int pre_delete
PROTO ((void));
606 static int pre_gcse
PROTO ((void));
607 static int one_pre_gcse_pass
PROTO ((int));
609 static void add_label_notes
PROTO ((rtx
, rtx
));
611 static void alloc_code_hoist_mem
PROTO ((int, int));
612 static void free_code_hoist_mem
PROTO ((void));
613 static void compute_code_hoist_vbeinout
PROTO ((void));
614 static void compute_code_hoist_data
PROTO ((void));
615 static int hoist_expr_reaches_here_p
PROTO ((int, int, int, char *));
616 static void hoist_code
PROTO ((void));
617 static int one_code_hoisting_pass
PROTO ((void));
619 static void alloc_rd_mem
PROTO ((int, int));
620 static void free_rd_mem
PROTO ((void));
621 static void handle_rd_kill_set
PROTO ((rtx
, int, int));
622 static void compute_kill_rd
PROTO ((void));
623 static void compute_rd
PROTO ((void));
624 static void alloc_avail_expr_mem
PROTO ((int, int));
625 static void free_avail_expr_mem
PROTO ((void));
626 static void compute_ae_gen
PROTO ((void));
627 static int expr_killed_p
PROTO ((rtx
, int));
628 static void compute_ae_kill
PROTO ((sbitmap
*, sbitmap
*));
629 static int expr_reaches_here_p
PROTO ((struct occr
*, struct expr
*,
631 static rtx computing_insn
PROTO ((struct expr
*, rtx
));
632 static int def_reaches_here_p
PROTO ((rtx
, rtx
));
633 static int can_disregard_other_sets
PROTO ((struct reg_set
**, rtx
, int));
634 static int handle_avail_expr
PROTO ((rtx
, struct expr
*));
635 static int classic_gcse
PROTO ((void));
636 static int one_classic_gcse_pass
PROTO ((int));
637 static void invalidate_nonnull_info
PROTO ((rtx
, rtx
, void *));
638 static void delete_null_pointer_checks_1
PROTO ((int_list_ptr
*, int *,
639 sbitmap
*, sbitmap
*,
640 struct null_pointer_info
*));
641 static rtx process_insert_insn
PROTO ((struct expr
*));
642 static int pre_edge_insert
PROTO ((struct edge_list
*, struct expr
**));
643 static int expr_reaches_here_p_work
PROTO ((struct occr
*, struct expr
*, int, int, char *));
644 static int pre_expr_reaches_here_p_work
PROTO ((int, struct expr
*, int, int, char *));
646 /* Entry point for global common subexpression elimination.
647 F is the first instruction in the function. */
655 /* Bytes used at start of pass. */
656 int initial_bytes_used
;
657 /* Maximum number of bytes used by a pass. */
659 /* Point to release obstack data from for each pass. */
660 char *gcse_obstack_bottom
;
662 /* We do not construct an accurate cfg in functions which call
663 setjmp, so just punt to be safe. */
664 if (current_function_calls_setjmp
)
667 /* Assume that we do not need to run jump optimizations after gcse. */
668 run_jump_opt_after_gcse
= 0;
670 /* For calling dump_foo fns from gdb. */
671 debug_stderr
= stderr
;
674 /* Identify the basic block information for this function, including
675 successors and predecessors. */
676 max_gcse_regno
= max_reg_num ();
677 find_basic_blocks (f
, max_gcse_regno
, file
, 1);
680 dump_flow_info (file
);
682 /* Return if there's nothing to do. */
683 if (n_basic_blocks
<= 1)
685 /* Free storage allocated by find_basic_blocks. */
686 free_basic_block_vars (0);
690 /* Trying to perform global optimizations on flow graphs which have
691 a high connectivity will take a long time and is unlikely to be
694 In normal circumstances a cfg should have about twice has many edges
695 as blocks. But we do not want to punish small functions which have
696 a couple switch statements. So we require a relatively large number
697 of basic blocks and the ratio of edges to blocks to be high. */
698 if (n_basic_blocks
> 1000 && n_edges
/ n_basic_blocks
>= 20)
700 /* Free storage allocated by find_basic_blocks. */
701 free_basic_block_vars (0);
705 /* See what modes support reg/reg copy operations. */
706 if (! can_copy_init_p
)
712 gcc_obstack_init (&gcse_obstack
);
715 /* Record where pseudo-registers are set.
716 This data is kept accurate during each pass.
717 ??? We could also record hard-reg information here
718 [since it's unchanging], however it is currently done during
719 hash table computation.
721 It may be tempting to compute MEM set information here too, but MEM
722 sets will be subject to code motion one day and thus we need to compute
723 information about memory sets when we build the hash tables. */
725 alloc_reg_set_mem (max_gcse_regno
);
729 initial_bytes_used
= bytes_used
;
731 gcse_obstack_bottom
= gcse_alloc (1);
733 while (changed
&& pass
< MAX_PASSES
)
737 fprintf (file
, "GCSE pass %d\n\n", pass
+ 1);
739 /* Initialize bytes_used to the space for the pred/succ lists,
740 and the reg_set_table data. */
741 bytes_used
= initial_bytes_used
;
743 /* Each pass may create new registers, so recalculate each time. */
744 max_gcse_regno
= max_reg_num ();
748 /* Don't allow constant propagation to modify jumps
750 changed
= one_cprop_pass (pass
+ 1, 0);
753 changed
|= one_classic_gcse_pass (pass
+ 1);
756 changed
|= one_pre_gcse_pass (pass
+ 1);
758 alloc_reg_set_mem (max_reg_num ());
760 run_jump_opt_after_gcse
= 1;
763 if (max_pass_bytes
< bytes_used
)
764 max_pass_bytes
= bytes_used
;
766 /* Free up memory, then reallocate for code hoisting. We can
767 not re-use the existing allocated memory because the tables
768 will not have info for the insns or registers created by
769 partial redundancy elimination. */
772 /* It does not make sense to run code hoisting unless we optimizing
773 for code size -- it rarely makes programs faster, and can make
774 them bigger if we did partial redundancy elimination (when optimizing
775 for space, we use a classic gcse algorithm instead of partial
776 redundancy algorithms). */
779 max_gcse_regno
= max_reg_num ();
781 changed
|= one_code_hoisting_pass ();
784 if (max_pass_bytes
< bytes_used
)
785 max_pass_bytes
= bytes_used
;
790 fprintf (file
, "\n");
793 obstack_free (&gcse_obstack
, gcse_obstack_bottom
);
797 /* Do one last pass of copy propagation, including cprop into
798 conditional jumps. */
800 max_gcse_regno
= max_reg_num ();
802 /* This time, go ahead and allow cprop to alter jumps. */
803 one_cprop_pass (pass
+ 1, 1);
808 fprintf (file
, "GCSE of %s: %d basic blocks, ",
809 current_function_name
, n_basic_blocks
);
810 fprintf (file
, "%d pass%s, %d bytes\n\n",
811 pass
, pass
> 1 ? "es" : "", max_pass_bytes
);
814 /* Free our obstack. */
815 obstack_free (&gcse_obstack
, NULL_PTR
);
816 /* Free reg_set_table. */
818 /* Free storage used to record predecessor/successor data. */
820 /* Free storage allocated by find_basic_blocks. */
821 free_basic_block_vars (0);
822 return run_jump_opt_after_gcse
;
825 /* Misc. utilities. */
827 /* Compute which modes support reg/reg copy operations. */
833 #ifndef AVOID_CCMODE_COPIES
836 char *free_point
= (char *) oballoc (1);
838 bzero (can_copy_p
, NUM_MACHINE_MODES
);
841 for (i
= 0; i
< NUM_MACHINE_MODES
; i
++)
843 switch (GET_MODE_CLASS (i
))
846 #ifdef AVOID_CCMODE_COPIES
849 reg
= gen_rtx_REG ((enum machine_mode
) i
, LAST_VIRTUAL_REGISTER
+ 1);
850 insn
= emit_insn (gen_rtx_SET (VOIDmode
, reg
, reg
));
851 if (recog (PATTERN (insn
), insn
, NULL_PTR
) >= 0)
862 /* Free the objects we just allocated. */
866 /* Cover function to xmalloc to record bytes allocated. */
873 return xmalloc (size
);
876 /* Cover function to xrealloc.
877 We don't record the additional size since we don't know it.
878 It won't affect memory usage stats much anyway. */
885 return xrealloc (ptr
, size
);
888 /* Cover function to obstack_alloc.
889 We don't need to record the bytes allocated here since
890 obstack_chunk_alloc is set to gmalloc. */
896 return (char *) obstack_alloc (&gcse_obstack
, size
);
899 /* Allocate memory for the cuid mapping array,
900 and reg/memory set tracking tables.
902 This is called at the start of each pass. */
911 /* Find the largest UID and create a mapping from UIDs to CUIDs.
912 CUIDs are like UIDs except they increase monotonically, have no gaps,
913 and only apply to real insns. */
915 max_uid
= get_max_uid ();
916 n
= (max_uid
+ 1) * sizeof (int);
917 uid_cuid
= (int *) gmalloc (n
);
918 bzero ((char *) uid_cuid
, n
);
919 for (insn
= f
, i
= 0; insn
; insn
= NEXT_INSN (insn
))
921 if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i')
922 INSN_CUID (insn
) = i
++;
924 INSN_CUID (insn
) = i
;
927 /* Create a table mapping cuids to insns. */
930 n
= (max_cuid
+ 1) * sizeof (rtx
);
931 cuid_insn
= (rtx
*) gmalloc (n
);
932 bzero ((char *) cuid_insn
, n
);
933 for (insn
= f
, i
= 0; insn
; insn
= NEXT_INSN (insn
))
935 if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i')
937 CUID_INSN (i
) = insn
;
942 /* Allocate vars to track sets of regs. */
944 reg_set_bitmap
= (sbitmap
) sbitmap_alloc (max_gcse_regno
);
946 /* Allocate vars to track sets of regs, memory per block. */
948 reg_set_in_block
= (sbitmap
*) sbitmap_vector_alloc (n_basic_blocks
,
950 mem_set_in_block
= (char *) gmalloc (n_basic_blocks
);
953 /* Free memory allocated by alloc_gcse_mem. */
961 free (reg_set_bitmap
);
963 free (reg_set_in_block
);
964 free (mem_set_in_block
);
967 /* Many of the global optimization algorithms work by solving dataflow
968 equations for various expressions. Initially, some local value is
969 computed for each expression in each block. Then, the values
970 across the various blocks are combined (by following flow graph
971 edges) to arrive at global values. Conceptually, each set of
972 equations is independent. We may therefore solve all the equations
973 in parallel, solve them one at a time, or pick any intermediate
976 When you're going to need N two-dimensional bitmaps, each X (say,
977 the number of blocks) by Y (say, the number of expressions), call
978 this function. It's not important what X and Y represent; only
979 that Y correspond to the things that can be done in parallel. This
980 function will return an appropriate chunking factor C; you should
981 solve C sets of equations in parallel. By going through this
982 function, we can easily trade space against time; by solving fewer
983 equations in parallel we use less space. */
986 get_bitmap_width (n
, x
, y
)
991 /* It's not really worth figuring out *exactly* how much memory will
992 be used by a particular choice. The important thing is to get
993 something approximately right. */
994 size_t max_bitmap_memory
= 10 * 1024 * 1024;
996 /* The number of bytes we'd use for a single column of minimum
998 size_t column_size
= n
* x
* sizeof (SBITMAP_ELT_TYPE
);
1000 /* Often, it's reasonable just to solve all the equations in
1002 if (column_size
* SBITMAP_SET_SIZE (y
) <= max_bitmap_memory
)
1005 /* Otherwise, pick the largest width we can, without going over the
1007 return SBITMAP_ELT_BITS
* ((max_bitmap_memory
+ column_size
- 1)
1012 /* Compute the local properties of each recorded expression.
1013 Local properties are those that are defined by the block, irrespective
1016 An expression is transparent in a block if its operands are not modified
1019 An expression is computed (locally available) in a block if it is computed
1020 at least once and expression would contain the same value if the
1021 computation was moved to the end of the block.
1023 An expression is locally anticipatable in a block if it is computed at
1024 least once and expression would contain the same value if the computation
1025 was moved to the beginning of the block.
1027 We call this routine for cprop, pre and code hoisting. They all
1028 compute basically the same information and thus can easily share
1031 TRANSP, COMP, and ANTLOC are destination sbitmaps for recording
1032 local properties. If NULL, then it is not necessary to compute
1033 or record that particular property.
1035 SETP controls which hash table to look at. If zero, this routine
1036 looks at the expr hash table; if nonzero this routine looks at
1037 the set hash table. Additionally, TRANSP is computed as ~TRANSP,
1038 since this is really cprop's ABSALTERED. */
1041 compute_local_properties (transp
, comp
, antloc
, setp
)
1047 int i
, hash_table_size
;
1048 struct expr
**hash_table
;
1050 /* Initialize any bitmaps that were passed in. */
1054 sbitmap_vector_zero (transp
, n_basic_blocks
);
1056 sbitmap_vector_ones (transp
, n_basic_blocks
);
1059 sbitmap_vector_zero (comp
, n_basic_blocks
);
1061 sbitmap_vector_zero (antloc
, n_basic_blocks
);
1063 /* We use the same code for cprop, pre and hoisting. For cprop
1064 we care about the set hash table, for pre and hoisting we
1065 care about the expr hash table. */
1066 hash_table_size
= setp
? set_hash_table_size
: expr_hash_table_size
;
1067 hash_table
= setp
? set_hash_table
: expr_hash_table
;
1069 for (i
= 0; i
< hash_table_size
; i
++)
1073 for (expr
= hash_table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
1076 int indx
= expr
->bitmap_index
;
1078 /* The expression is transparent in this block if it is not killed.
1079 We start by assuming all are transparent [none are killed], and
1080 then reset the bits for those that are. */
1083 compute_transp (expr
->expr
, indx
, transp
, setp
);
1085 /* The occurrences recorded in antic_occr are exactly those that
1086 we want to set to non-zero in ANTLOC. */
1090 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
1092 int bb
= BLOCK_NUM (occr
->insn
);
1093 SET_BIT (antloc
[bb
], indx
);
1095 /* While we're scanning the table, this is a good place to
1097 occr
->deleted_p
= 0;
1101 /* The occurrences recorded in avail_occr are exactly those that
1102 we want to set to non-zero in COMP. */
1106 for (occr
= expr
->avail_occr
; occr
!= NULL
; occr
= occr
->next
)
1108 int bb
= BLOCK_NUM (occr
->insn
);
1109 SET_BIT (comp
[bb
], indx
);
1111 /* While we're scanning the table, this is a good place to
1117 /* While we're scanning the table, this is a good place to
1119 expr
->reaching_reg
= 0;
1125 /* Register set information.
1127 `reg_set_table' records where each register is set or otherwise
1130 static struct obstack reg_set_obstack
;
1133 alloc_reg_set_mem (n_regs
)
1138 reg_set_table_size
= n_regs
+ REG_SET_TABLE_SLOP
;
1139 n
= reg_set_table_size
* sizeof (struct reg_set
*);
1140 reg_set_table
= (struct reg_set
**) gmalloc (n
);
1141 bzero ((char *) reg_set_table
, n
);
1143 gcc_obstack_init (®_set_obstack
);
1149 free (reg_set_table
);
1150 obstack_free (®_set_obstack
, NULL_PTR
);
1153 /* Record REGNO in the reg_set table. */
1156 record_one_set (regno
, insn
)
1160 /* allocate a new reg_set element and link it onto the list */
1161 struct reg_set
*new_reg_info
, *reg_info_ptr1
, *reg_info_ptr2
;
1163 /* If the table isn't big enough, enlarge it. */
1164 if (regno
>= reg_set_table_size
)
1166 int new_size
= regno
+ REG_SET_TABLE_SLOP
;
1167 reg_set_table
= (struct reg_set
**)
1168 grealloc ((char *) reg_set_table
,
1169 new_size
* sizeof (struct reg_set
*));
1170 bzero ((char *) (reg_set_table
+ reg_set_table_size
),
1171 (new_size
- reg_set_table_size
) * sizeof (struct reg_set
*));
1172 reg_set_table_size
= new_size
;
1175 new_reg_info
= (struct reg_set
*) obstack_alloc (®_set_obstack
,
1176 sizeof (struct reg_set
));
1177 bytes_used
+= sizeof (struct reg_set
);
1178 new_reg_info
->insn
= insn
;
1179 new_reg_info
->next
= NULL
;
1180 if (reg_set_table
[regno
] == NULL
)
1181 reg_set_table
[regno
] = new_reg_info
;
1184 reg_info_ptr1
= reg_info_ptr2
= reg_set_table
[regno
];
1185 /* ??? One could keep a "last" pointer to speed this up. */
1186 while (reg_info_ptr1
!= NULL
)
1188 reg_info_ptr2
= reg_info_ptr1
;
1189 reg_info_ptr1
= reg_info_ptr1
->next
;
1191 reg_info_ptr2
->next
= new_reg_info
;
1195 /* Called from compute_sets via note_stores to handle one
1196 SET or CLOBBER in an insn. The DATA is really the instruction
1197 in which the SET is occurring. */
1200 record_set_info (dest
, setter
, data
)
1201 rtx dest
, setter ATTRIBUTE_UNUSED
;
1204 rtx record_set_insn
= (rtx
) data
;
1206 if (GET_CODE (dest
) == SUBREG
)
1207 dest
= SUBREG_REG (dest
);
1209 if (GET_CODE (dest
) == REG
)
1211 if (REGNO (dest
) >= FIRST_PSEUDO_REGISTER
)
1212 record_one_set (REGNO (dest
), record_set_insn
);
1216 /* Scan the function and record each set of each pseudo-register.
1218 This is called once, at the start of the gcse pass.
1219 See the comments for `reg_set_table' for further docs. */
1229 if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i')
1230 note_stores (PATTERN (insn
), record_set_info
, insn
);
1231 insn
= NEXT_INSN (insn
);
1235 /* Hash table support. */
1237 #define NEVER_SET -1
1239 /* For each register, the cuid of the first/last insn in the block to set it,
1240 or -1 if not set. */
1241 static int *reg_first_set
;
1242 static int *reg_last_set
;
1244 /* While computing "first/last set" info, this is the CUID of first/last insn
1245 to set memory or -1 if not set. `mem_last_set' is also used when
1246 performing GCSE to record whether memory has been set since the beginning
1248 Note that handling of memory is very simple, we don't make any attempt
1249 to optimize things (later). */
1250 static int mem_first_set
;
1251 static int mem_last_set
;
1253 /* Perform a quick check whether X, the source of a set, is something
1254 we want to consider for GCSE. */
1260 enum rtx_code code
= GET_CODE (x
);
1278 /* Return non-zero if the operands of expression X are unchanged from the
1279 start of INSN's basic block up to but not including INSN (if AVAIL_P == 0),
1280 or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */
1283 oprs_unchanged_p (x
, insn
, avail_p
)
1291 /* repeat is used to turn tail-recursion into iteration. */
1297 code
= GET_CODE (x
);
1302 return (reg_last_set
[REGNO (x
)] == NEVER_SET
1303 || reg_last_set
[REGNO (x
)] < INSN_CUID (insn
));
1305 return (reg_first_set
[REGNO (x
)] == NEVER_SET
1306 || reg_first_set
[REGNO (x
)] >= INSN_CUID (insn
));
1311 if (mem_last_set
!= NEVER_SET
1312 && mem_last_set
>= INSN_CUID (insn
))
1317 if (mem_first_set
!= NEVER_SET
1318 && mem_first_set
< INSN_CUID (insn
))
1345 i
= GET_RTX_LENGTH (code
) - 1;
1346 fmt
= GET_RTX_FORMAT (code
);
1351 rtx tem
= XEXP (x
, i
);
1353 /* If we are about to do the last recursive call
1354 needed at this level, change it into iteration.
1355 This function is called enough to be worth it. */
1361 if (! oprs_unchanged_p (tem
, insn
, avail_p
))
1364 else if (fmt
[i
] == 'E')
1367 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1369 if (! oprs_unchanged_p (XVECEXP (x
, i
, j
), insn
, avail_p
))
1378 /* Return non-zero if the operands of expression X are unchanged from
1379 the start of INSN's basic block up to but not including INSN. */
1382 oprs_anticipatable_p (x
, insn
)
1385 return oprs_unchanged_p (x
, insn
, 0);
1388 /* Return non-zero if the operands of expression X are unchanged from
1389 INSN to the end of INSN's basic block. */
1392 oprs_available_p (x
, insn
)
1395 return oprs_unchanged_p (x
, insn
, 1);
1398 /* Hash expression X.
1399 MODE is only used if X is a CONST_INT.
1400 A boolean indicating if a volatile operand is found or if the expression
1401 contains something we don't want to insert in the table is stored in
1404 ??? One might want to merge this with canon_hash. Later. */
1407 hash_expr (x
, mode
, do_not_record_p
, hash_table_size
)
1409 enum machine_mode mode
;
1410 int *do_not_record_p
;
1411 int hash_table_size
;
1415 *do_not_record_p
= 0;
1417 hash
= hash_expr_1 (x
, mode
, do_not_record_p
);
1418 return hash
% hash_table_size
;
1421 /* Subroutine of hash_expr to do the actual work. */
1424 hash_expr_1 (x
, mode
, do_not_record_p
)
1426 enum machine_mode mode
;
1427 int *do_not_record_p
;
1434 /* repeat is used to turn tail-recursion into iteration. */
1440 code
= GET_CODE (x
);
1445 register int regno
= REGNO (x
);
1446 hash
+= ((unsigned) REG
<< 7) + regno
;
1452 unsigned HOST_WIDE_INT tem
= INTVAL (x
);
1453 hash
+= ((unsigned) CONST_INT
<< 7) + (unsigned) mode
+ tem
;
1458 /* This is like the general case, except that it only counts
1459 the integers representing the constant. */
1460 hash
+= (unsigned) code
+ (unsigned) GET_MODE (x
);
1461 if (GET_MODE (x
) != VOIDmode
)
1462 for (i
= 2; i
< GET_RTX_LENGTH (CONST_DOUBLE
); i
++)
1464 unsigned tem
= XWINT (x
, i
);
1468 hash
+= ((unsigned) CONST_DOUBLE_LOW (x
)
1469 + (unsigned) CONST_DOUBLE_HIGH (x
));
1472 /* Assume there is only one rtx object for any given label. */
1474 /* We don't hash on the address of the CODE_LABEL to avoid bootstrap
1475 differences and differences between each stage's debugging dumps. */
1476 hash
+= ((unsigned) LABEL_REF
<< 7) + CODE_LABEL_NUMBER (XEXP (x
, 0));
1481 /* Don't hash on the symbol's address to avoid bootstrap differences.
1482 Different hash values may cause expressions to be recorded in
1483 different orders and thus different registers to be used in the
1484 final assembler. This also avoids differences in the dump files
1485 between various stages. */
1487 unsigned char *p
= (unsigned char *) XSTR (x
, 0);
1489 h
+= (h
<< 7) + *p
++; /* ??? revisit */
1490 hash
+= ((unsigned) SYMBOL_REF
<< 7) + h
;
1495 if (MEM_VOLATILE_P (x
))
1497 *do_not_record_p
= 1;
1500 hash
+= (unsigned) MEM
;
1501 hash
+= MEM_ALIAS_SET (x
);
1512 case UNSPEC_VOLATILE
:
1513 *do_not_record_p
= 1;
1517 if (MEM_VOLATILE_P (x
))
1519 *do_not_record_p
= 1;
1527 i
= GET_RTX_LENGTH (code
) - 1;
1528 hash
+= (unsigned) code
+ (unsigned) GET_MODE (x
);
1529 fmt
= GET_RTX_FORMAT (code
);
1534 rtx tem
= XEXP (x
, i
);
1536 /* If we are about to do the last recursive call
1537 needed at this level, change it into iteration.
1538 This function is called enough to be worth it. */
1544 hash
+= hash_expr_1 (tem
, 0, do_not_record_p
);
1545 if (*do_not_record_p
)
1548 else if (fmt
[i
] == 'E')
1549 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1551 hash
+= hash_expr_1 (XVECEXP (x
, i
, j
), 0, do_not_record_p
);
1552 if (*do_not_record_p
)
1555 else if (fmt
[i
] == 's')
1557 register unsigned char *p
= (unsigned char *) XSTR (x
, i
);
1562 else if (fmt
[i
] == 'i')
1564 register unsigned tem
= XINT (x
, i
);
1574 /* Hash a set of register REGNO.
1576 Sets are hashed on the register that is set.
1577 This simplifies the PRE copy propagation code.
1579 ??? May need to make things more elaborate. Later, as necessary. */
1582 hash_set (regno
, hash_table_size
)
1584 int hash_table_size
;
1589 return hash
% hash_table_size
;
1592 /* Return non-zero if exp1 is equivalent to exp2.
1593 ??? Borrowed from cse.c. Might want to remerge with cse.c. Later. */
1600 register enum rtx_code code
;
1601 register const char *fmt
;
1605 if (x
== 0 || y
== 0)
1608 code
= GET_CODE (x
);
1609 if (code
!= GET_CODE (y
))
1612 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
1613 if (GET_MODE (x
) != GET_MODE (y
))
1623 return INTVAL (x
) == INTVAL (y
);
1626 return XEXP (x
, 0) == XEXP (y
, 0);
1629 return XSTR (x
, 0) == XSTR (y
, 0);
1632 return REGNO (x
) == REGNO (y
);
1635 /* Can't merge two expressions in different alias sets, since we can
1636 decide that the expression is transparent in a block when it isn't,
1637 due to it being set with the different alias set. */
1638 if (MEM_ALIAS_SET (x
) != MEM_ALIAS_SET (y
))
1642 /* For commutative operations, check both orders. */
1650 return ((expr_equiv_p (XEXP (x
, 0), XEXP (y
, 0))
1651 && expr_equiv_p (XEXP (x
, 1), XEXP (y
, 1)))
1652 || (expr_equiv_p (XEXP (x
, 0), XEXP (y
, 1))
1653 && expr_equiv_p (XEXP (x
, 1), XEXP (y
, 0))));
1659 /* Compare the elements. If any pair of corresponding elements
1660 fail to match, return 0 for the whole thing. */
1662 fmt
= GET_RTX_FORMAT (code
);
1663 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1668 if (! expr_equiv_p (XEXP (x
, i
), XEXP (y
, i
)))
1673 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
1675 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1676 if (! expr_equiv_p (XVECEXP (x
, i
, j
), XVECEXP (y
, i
, j
)))
1681 if (strcmp (XSTR (x
, i
), XSTR (y
, i
)))
1686 if (XINT (x
, i
) != XINT (y
, i
))
1691 if (XWINT (x
, i
) != XWINT (y
, i
))
1706 /* Insert expression X in INSN in the hash table.
1707 If it is already present, record it as the last occurrence in INSN's
1710 MODE is the mode of the value X is being stored into.
1711 It is only used if X is a CONST_INT.
1713 ANTIC_P is non-zero if X is an anticipatable expression.
1714 AVAIL_P is non-zero if X is an available expression. */
1717 insert_expr_in_table (x
, mode
, insn
, antic_p
, avail_p
)
1719 enum machine_mode mode
;
1721 int antic_p
, avail_p
;
1723 int found
, do_not_record_p
;
1725 struct expr
*cur_expr
, *last_expr
= NULL
;
1726 struct occr
*antic_occr
, *avail_occr
;
1727 struct occr
*last_occr
= NULL
;
1729 hash
= hash_expr (x
, mode
, &do_not_record_p
, expr_hash_table_size
);
1731 /* Do not insert expression in table if it contains volatile operands,
1732 or if hash_expr determines the expression is something we don't want
1733 to or can't handle. */
1734 if (do_not_record_p
)
1737 cur_expr
= expr_hash_table
[hash
];
1740 while (cur_expr
&& ! (found
= expr_equiv_p (cur_expr
->expr
, x
)))
1742 /* If the expression isn't found, save a pointer to the end of
1744 last_expr
= cur_expr
;
1745 cur_expr
= cur_expr
->next_same_hash
;
1750 cur_expr
= (struct expr
*) gcse_alloc (sizeof (struct expr
));
1751 bytes_used
+= sizeof (struct expr
);
1752 if (expr_hash_table
[hash
] == NULL
)
1754 /* This is the first pattern that hashed to this index. */
1755 expr_hash_table
[hash
] = cur_expr
;
1759 /* Add EXPR to end of this hash chain. */
1760 last_expr
->next_same_hash
= cur_expr
;
1762 /* Set the fields of the expr element. */
1764 cur_expr
->bitmap_index
= n_exprs
++;
1765 cur_expr
->next_same_hash
= NULL
;
1766 cur_expr
->antic_occr
= NULL
;
1767 cur_expr
->avail_occr
= NULL
;
1770 /* Now record the occurrence(s). */
1774 antic_occr
= cur_expr
->antic_occr
;
1776 /* Search for another occurrence in the same basic block. */
1777 while (antic_occr
&& BLOCK_NUM (antic_occr
->insn
) != BLOCK_NUM (insn
))
1779 /* If an occurrence isn't found, save a pointer to the end of
1781 last_occr
= antic_occr
;
1782 antic_occr
= antic_occr
->next
;
1787 /* Found another instance of the expression in the same basic block.
1788 Prefer the currently recorded one. We want the first one in the
1789 block and the block is scanned from start to end. */
1790 ; /* nothing to do */
1794 /* First occurrence of this expression in this basic block. */
1795 antic_occr
= (struct occr
*) gcse_alloc (sizeof (struct occr
));
1796 bytes_used
+= sizeof (struct occr
);
1797 /* First occurrence of this expression in any block? */
1798 if (cur_expr
->antic_occr
== NULL
)
1799 cur_expr
->antic_occr
= antic_occr
;
1801 last_occr
->next
= antic_occr
;
1802 antic_occr
->insn
= insn
;
1803 antic_occr
->next
= NULL
;
1809 avail_occr
= cur_expr
->avail_occr
;
1811 /* Search for another occurrence in the same basic block. */
1812 while (avail_occr
&& BLOCK_NUM (avail_occr
->insn
) != BLOCK_NUM (insn
))
1814 /* If an occurrence isn't found, save a pointer to the end of
1816 last_occr
= avail_occr
;
1817 avail_occr
= avail_occr
->next
;
1822 /* Found another instance of the expression in the same basic block.
1823 Prefer this occurrence to the currently recorded one. We want
1824 the last one in the block and the block is scanned from start
1826 avail_occr
->insn
= insn
;
1830 /* First occurrence of this expression in this basic block. */
1831 avail_occr
= (struct occr
*) gcse_alloc (sizeof (struct occr
));
1832 bytes_used
+= sizeof (struct occr
);
1833 /* First occurrence of this expression in any block? */
1834 if (cur_expr
->avail_occr
== NULL
)
1835 cur_expr
->avail_occr
= avail_occr
;
1837 last_occr
->next
= avail_occr
;
1838 avail_occr
->insn
= insn
;
1839 avail_occr
->next
= NULL
;
1844 /* Insert pattern X in INSN in the hash table.
1845 X is a SET of a reg to either another reg or a constant.
1846 If it is already present, record it as the last occurrence in INSN's
1850 insert_set_in_table (x
, insn
)
1856 struct expr
*cur_expr
, *last_expr
= NULL
;
1857 struct occr
*cur_occr
, *last_occr
= NULL
;
1859 if (GET_CODE (x
) != SET
1860 || GET_CODE (SET_DEST (x
)) != REG
)
1863 hash
= hash_set (REGNO (SET_DEST (x
)), set_hash_table_size
);
1865 cur_expr
= set_hash_table
[hash
];
1868 while (cur_expr
&& ! (found
= expr_equiv_p (cur_expr
->expr
, x
)))
1870 /* If the expression isn't found, save a pointer to the end of
1872 last_expr
= cur_expr
;
1873 cur_expr
= cur_expr
->next_same_hash
;
1878 cur_expr
= (struct expr
*) gcse_alloc (sizeof (struct expr
));
1879 bytes_used
+= sizeof (struct expr
);
1880 if (set_hash_table
[hash
] == NULL
)
1882 /* This is the first pattern that hashed to this index. */
1883 set_hash_table
[hash
] = cur_expr
;
1887 /* Add EXPR to end of this hash chain. */
1888 last_expr
->next_same_hash
= cur_expr
;
1890 /* Set the fields of the expr element.
1891 We must copy X because it can be modified when copy propagation is
1892 performed on its operands. */
1893 /* ??? Should this go in a different obstack? */
1894 cur_expr
->expr
= copy_rtx (x
);
1895 cur_expr
->bitmap_index
= n_sets
++;
1896 cur_expr
->next_same_hash
= NULL
;
1897 cur_expr
->antic_occr
= NULL
;
1898 cur_expr
->avail_occr
= NULL
;
1901 /* Now record the occurrence. */
1903 cur_occr
= cur_expr
->avail_occr
;
1905 /* Search for another occurrence in the same basic block. */
1906 while (cur_occr
&& BLOCK_NUM (cur_occr
->insn
) != BLOCK_NUM (insn
))
1908 /* If an occurrence isn't found, save a pointer to the end of
1910 last_occr
= cur_occr
;
1911 cur_occr
= cur_occr
->next
;
1916 /* Found another instance of the expression in the same basic block.
1917 Prefer this occurrence to the currently recorded one. We want
1918 the last one in the block and the block is scanned from start
1920 cur_occr
->insn
= insn
;
1924 /* First occurrence of this expression in this basic block. */
1925 cur_occr
= (struct occr
*) gcse_alloc (sizeof (struct occr
));
1926 bytes_used
+= sizeof (struct occr
);
1927 /* First occurrence of this expression in any block? */
1928 if (cur_expr
->avail_occr
== NULL
)
1929 cur_expr
->avail_occr
= cur_occr
;
1931 last_occr
->next
= cur_occr
;
1932 cur_occr
->insn
= insn
;
1933 cur_occr
->next
= NULL
;
1937 /* Scan pattern PAT of INSN and add an entry to the hash table.
1938 If SET_P is non-zero, this is for the assignment hash table,
1939 otherwise it is for the expression hash table. */
1942 hash_scan_set (pat
, insn
, set_p
)
1946 rtx src
= SET_SRC (pat
);
1947 rtx dest
= SET_DEST (pat
);
1949 if (GET_CODE (src
) == CALL
)
1950 hash_scan_call (src
, insn
);
1952 if (GET_CODE (dest
) == REG
)
1954 int regno
= REGNO (dest
);
1957 /* Only record sets of pseudo-regs in the hash table. */
1959 && regno
>= FIRST_PSEUDO_REGISTER
1960 /* Don't GCSE something if we can't do a reg/reg copy. */
1961 && can_copy_p
[GET_MODE (dest
)]
1962 /* Is SET_SRC something we want to gcse? */
1963 && want_to_gcse_p (src
))
1965 /* An expression is not anticipatable if its operands are
1966 modified before this insn. */
1967 int antic_p
= oprs_anticipatable_p (src
, insn
);
1968 /* An expression is not available if its operands are
1969 subsequently modified, including this insn. */
1970 int avail_p
= oprs_available_p (src
, insn
);
1971 insert_expr_in_table (src
, GET_MODE (dest
), insn
, antic_p
, avail_p
);
1973 /* Record sets for constant/copy propagation. */
1975 && regno
>= FIRST_PSEUDO_REGISTER
1976 && ((GET_CODE (src
) == REG
1977 && REGNO (src
) >= FIRST_PSEUDO_REGISTER
1978 && can_copy_p
[GET_MODE (dest
)])
1979 || GET_CODE (src
) == CONST_INT
1980 || GET_CODE (src
) == SYMBOL_REF
1981 || GET_CODE (src
) == CONST_DOUBLE
)
1982 /* A copy is not available if its src or dest is subsequently
1983 modified. Here we want to search from INSN+1 on, but
1984 oprs_available_p searches from INSN on. */
1985 && (insn
== BLOCK_END (BLOCK_NUM (insn
))
1986 || ((tmp
= next_nonnote_insn (insn
)) != NULL_RTX
1987 && oprs_available_p (pat
, tmp
))))
1988 insert_set_in_table (pat
, insn
);
1993 hash_scan_clobber (x
, insn
)
1994 rtx x ATTRIBUTE_UNUSED
, insn ATTRIBUTE_UNUSED
;
1996 /* Currently nothing to do. */
2000 hash_scan_call (x
, insn
)
2001 rtx x ATTRIBUTE_UNUSED
, insn ATTRIBUTE_UNUSED
;
2003 /* Currently nothing to do. */
2006 /* Process INSN and add hash table entries as appropriate.
2008 Only available expressions that set a single pseudo-reg are recorded.
2010 Single sets in a PARALLEL could be handled, but it's an extra complication
2011 that isn't dealt with right now. The trick is handling the CLOBBERs that
2012 are also in the PARALLEL. Later.
2014 If SET_P is non-zero, this is for the assignment hash table,
2015 otherwise it is for the expression hash table.
2016 If IN_LIBCALL_BLOCK nonzero, we are in a libcall block, and should
2017 not record any expressions. */
2020 hash_scan_insn (insn
, set_p
, in_libcall_block
)
2023 int in_libcall_block
;
2025 rtx pat
= PATTERN (insn
);
2027 /* Pick out the sets of INSN and for other forms of instructions record
2028 what's been modified. */
2030 if (GET_CODE (pat
) == SET
&& ! in_libcall_block
)
2032 /* Ignore obvious no-ops. */
2033 if (SET_SRC (pat
) != SET_DEST (pat
))
2034 hash_scan_set (pat
, insn
, set_p
);
2036 else if (GET_CODE (pat
) == PARALLEL
)
2040 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
2042 rtx x
= XVECEXP (pat
, 0, i
);
2044 if (GET_CODE (x
) == SET
)
2046 if (GET_CODE (SET_SRC (x
)) == CALL
)
2047 hash_scan_call (SET_SRC (x
), insn
);
2049 else if (GET_CODE (x
) == CLOBBER
)
2050 hash_scan_clobber (x
, insn
);
2051 else if (GET_CODE (x
) == CALL
)
2052 hash_scan_call (x
, insn
);
2055 else if (GET_CODE (pat
) == CLOBBER
)
2056 hash_scan_clobber (pat
, insn
);
2057 else if (GET_CODE (pat
) == CALL
)
2058 hash_scan_call (pat
, insn
);
2062 dump_hash_table (file
, name
, table
, table_size
, total_size
)
2065 struct expr
**table
;
2066 int table_size
, total_size
;
2069 /* Flattened out table, so it's printed in proper order. */
2070 struct expr
**flat_table
;
2071 unsigned int *hash_val
;
2074 = (struct expr
**) xcalloc (total_size
, sizeof (struct expr
*));
2075 hash_val
= (unsigned int *) xmalloc (total_size
* sizeof (unsigned int));
2077 for (i
= 0; i
< table_size
; i
++)
2081 for (expr
= table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
2083 flat_table
[expr
->bitmap_index
] = expr
;
2084 hash_val
[expr
->bitmap_index
] = i
;
2088 fprintf (file
, "%s hash table (%d buckets, %d entries)\n",
2089 name
, table_size
, total_size
);
2091 for (i
= 0; i
< total_size
; i
++)
2093 struct expr
*expr
= flat_table
[i
];
2095 fprintf (file
, "Index %d (hash value %d)\n ",
2096 expr
->bitmap_index
, hash_val
[i
]);
2097 print_rtl (file
, expr
->expr
);
2098 fprintf (file
, "\n");
2101 fprintf (file
, "\n");
2108 /* Record register first/last/block set information for REGNO in INSN.
2109 reg_first_set records the first place in the block where the register
2110 is set and is used to compute "anticipatability".
2111 reg_last_set records the last place in the block where the register
2112 is set and is used to compute "availability".
2113 reg_set_in_block records whether the register is set in the block
2114 and is used to compute "transparency". */
2117 record_last_reg_set_info (insn
, regno
)
2121 if (reg_first_set
[regno
] == NEVER_SET
)
2122 reg_first_set
[regno
] = INSN_CUID (insn
);
2123 reg_last_set
[regno
] = INSN_CUID (insn
);
2124 SET_BIT (reg_set_in_block
[BLOCK_NUM (insn
)], regno
);
2127 /* Record memory first/last/block set information for INSN. */
2130 record_last_mem_set_info (insn
)
2133 if (mem_first_set
== NEVER_SET
)
2134 mem_first_set
= INSN_CUID (insn
);
2135 mem_last_set
= INSN_CUID (insn
);
2136 mem_set_in_block
[BLOCK_NUM (insn
)] = 1;
2139 /* Called from compute_hash_table via note_stores to handle one
2140 SET or CLOBBER in an insn. DATA is really the instruction in which
2141 the SET is taking place. */
2144 record_last_set_info (dest
, setter
, data
)
2145 rtx dest
, setter ATTRIBUTE_UNUSED
;
2148 rtx last_set_insn
= (rtx
) data
;
2150 if (GET_CODE (dest
) == SUBREG
)
2151 dest
= SUBREG_REG (dest
);
2153 if (GET_CODE (dest
) == REG
)
2154 record_last_reg_set_info (last_set_insn
, REGNO (dest
));
2155 else if (GET_CODE (dest
) == MEM
2156 /* Ignore pushes, they clobber nothing. */
2157 && ! push_operand (dest
, GET_MODE (dest
)))
2158 record_last_mem_set_info (last_set_insn
);
2161 /* Top level function to create an expression or assignment hash table.
2163 Expression entries are placed in the hash table if
2164 - they are of the form (set (pseudo-reg) src),
2165 - src is something we want to perform GCSE on,
2166 - none of the operands are subsequently modified in the block
2168 Assignment entries are placed in the hash table if
2169 - they are of the form (set (pseudo-reg) src),
2170 - src is something we want to perform const/copy propagation on,
2171 - none of the operands or target are subsequently modified in the block
2172 Currently src must be a pseudo-reg or a const_int.
2174 F is the first insn.
2175 SET_P is non-zero for computing the assignment hash table. */
2178 compute_hash_table (set_p
)
2183 /* While we compute the hash table we also compute a bit array of which
2184 registers are set in which blocks.
2185 We also compute which blocks set memory, in the absence of aliasing
2186 support [which is TODO].
2187 ??? This isn't needed during const/copy propagation, but it's cheap to
2189 sbitmap_vector_zero (reg_set_in_block
, n_basic_blocks
);
2190 bzero ((char *) mem_set_in_block
, n_basic_blocks
);
2192 /* Some working arrays used to track first and last set in each block. */
2193 /* ??? One could use alloca here, but at some size a threshold is crossed
2194 beyond which one should use malloc. Are we at that threshold here? */
2195 reg_first_set
= (int *) gmalloc (max_gcse_regno
* sizeof (int));
2196 reg_last_set
= (int *) gmalloc (max_gcse_regno
* sizeof (int));
2198 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
2202 int in_libcall_block
;
2205 /* First pass over the instructions records information used to
2206 determine when registers and memory are first and last set.
2207 ??? The mem_set_in_block and hard-reg reg_set_in_block computation
2208 could be moved to compute_sets since they currently don't change. */
2210 for (i
= 0; i
< max_gcse_regno
; i
++)
2211 reg_first_set
[i
] = reg_last_set
[i
] = NEVER_SET
;
2212 mem_first_set
= NEVER_SET
;
2213 mem_last_set
= NEVER_SET
;
2215 for (insn
= BLOCK_HEAD (bb
);
2216 insn
&& insn
!= NEXT_INSN (BLOCK_END (bb
));
2217 insn
= NEXT_INSN (insn
))
2219 #ifdef NON_SAVING_SETJMP
2220 if (NON_SAVING_SETJMP
&& GET_CODE (insn
) == NOTE
2221 && NOTE_LINE_NUMBER (insn
) == NOTE_INSN_SETJMP
)
2223 for (regno
= 0; regno
< FIRST_PSEUDO_REGISTER
; regno
++)
2224 record_last_reg_set_info (insn
, regno
);
2229 if (GET_RTX_CLASS (GET_CODE (insn
)) != 'i')
2232 if (GET_CODE (insn
) == CALL_INSN
)
2234 for (regno
= 0; regno
< FIRST_PSEUDO_REGISTER
; regno
++)
2235 if ((call_used_regs
[regno
]
2236 && regno
!= STACK_POINTER_REGNUM
2237 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2238 && regno
!= HARD_FRAME_POINTER_REGNUM
2240 #if ARG_POINTER_REGNUM != FRAME_POINTER_REGNUM
2241 && ! (regno
== ARG_POINTER_REGNUM
&& fixed_regs
[regno
])
2243 #if defined (PIC_OFFSET_TABLE_REGNUM) && !defined (PIC_OFFSET_TABLE_REG_CALL_CLOBBERED)
2244 && ! (regno
== PIC_OFFSET_TABLE_REGNUM
&& flag_pic
)
2247 && regno
!= FRAME_POINTER_REGNUM
)
2248 || global_regs
[regno
])
2249 record_last_reg_set_info (insn
, regno
);
2250 if (! CONST_CALL_P (insn
))
2251 record_last_mem_set_info (insn
);
2254 note_stores (PATTERN (insn
), record_last_set_info
, insn
);
2257 /* The next pass builds the hash table. */
2259 for (insn
= BLOCK_HEAD (bb
), in_libcall_block
= 0;
2260 insn
&& insn
!= NEXT_INSN (BLOCK_END (bb
));
2261 insn
= NEXT_INSN (insn
))
2263 if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i')
2265 if (find_reg_note (insn
, REG_LIBCALL
, NULL_RTX
))
2266 in_libcall_block
= 1;
2267 else if (find_reg_note (insn
, REG_RETVAL
, NULL_RTX
))
2268 in_libcall_block
= 0;
2269 hash_scan_insn (insn
, set_p
, in_libcall_block
);
2274 free (reg_first_set
);
2275 free (reg_last_set
);
2276 /* Catch bugs early. */
2277 reg_first_set
= reg_last_set
= 0;
2280 /* Allocate space for the set hash table.
2281 N_INSNS is the number of instructions in the function.
2282 It is used to determine the number of buckets to use. */
2285 alloc_set_hash_table (n_insns
)
2290 set_hash_table_size
= n_insns
/ 4;
2291 if (set_hash_table_size
< 11)
2292 set_hash_table_size
= 11;
2293 /* Attempt to maintain efficient use of hash table.
2294 Making it an odd number is simplest for now.
2295 ??? Later take some measurements. */
2296 set_hash_table_size
|= 1;
2297 n
= set_hash_table_size
* sizeof (struct expr
*);
2298 set_hash_table
= (struct expr
**) gmalloc (n
);
2301 /* Free things allocated by alloc_set_hash_table. */
2304 free_set_hash_table ()
2306 free (set_hash_table
);
2309 /* Compute the hash table for doing copy/const propagation. */
2312 compute_set_hash_table ()
2314 /* Initialize count of number of entries in hash table. */
2316 bzero ((char *) set_hash_table
, set_hash_table_size
* sizeof (struct expr
*));
2318 compute_hash_table (1);
2321 /* Allocate space for the expression hash table.
2322 N_INSNS is the number of instructions in the function.
2323 It is used to determine the number of buckets to use. */
2326 alloc_expr_hash_table (n_insns
)
2331 expr_hash_table_size
= n_insns
/ 2;
2332 /* Make sure the amount is usable. */
2333 if (expr_hash_table_size
< 11)
2334 expr_hash_table_size
= 11;
2335 /* Attempt to maintain efficient use of hash table.
2336 Making it an odd number is simplest for now.
2337 ??? Later take some measurements. */
2338 expr_hash_table_size
|= 1;
2339 n
= expr_hash_table_size
* sizeof (struct expr
*);
2340 expr_hash_table
= (struct expr
**) gmalloc (n
);
2343 /* Free things allocated by alloc_expr_hash_table. */
2346 free_expr_hash_table ()
2348 free (expr_hash_table
);
2351 /* Compute the hash table for doing GCSE. */
2354 compute_expr_hash_table ()
2356 /* Initialize count of number of entries in hash table. */
2358 bzero ((char *) expr_hash_table
, expr_hash_table_size
* sizeof (struct expr
*));
2360 compute_hash_table (0);
2363 /* Expression tracking support. */
2365 /* Lookup pattern PAT in the expression table.
2366 The result is a pointer to the table entry, or NULL if not found. */
2368 static struct expr
*
2372 int do_not_record_p
;
2373 unsigned int hash
= hash_expr (pat
, GET_MODE (pat
), &do_not_record_p
,
2374 expr_hash_table_size
);
2377 if (do_not_record_p
)
2380 expr
= expr_hash_table
[hash
];
2382 while (expr
&& ! expr_equiv_p (expr
->expr
, pat
))
2383 expr
= expr
->next_same_hash
;
2388 /* Lookup REGNO in the set table.
2389 If PAT is non-NULL look for the entry that matches it, otherwise return
2390 the first entry for REGNO.
2391 The result is a pointer to the table entry, or NULL if not found. */
2393 static struct expr
*
2394 lookup_set (regno
, pat
)
2398 unsigned int hash
= hash_set (regno
, set_hash_table_size
);
2401 expr
= set_hash_table
[hash
];
2405 while (expr
&& ! expr_equiv_p (expr
->expr
, pat
))
2406 expr
= expr
->next_same_hash
;
2410 while (expr
&& REGNO (SET_DEST (expr
->expr
)) != regno
)
2411 expr
= expr
->next_same_hash
;
2417 /* Return the next entry for REGNO in list EXPR. */
2419 static struct expr
*
2420 next_set (regno
, expr
)
2425 expr
= expr
->next_same_hash
;
2426 while (expr
&& REGNO (SET_DEST (expr
->expr
)) != regno
);
2430 /* Reset tables used to keep track of what's still available [since the
2431 start of the block]. */
2434 reset_opr_set_tables ()
2436 /* Maintain a bitmap of which regs have been set since beginning of
2438 sbitmap_zero (reg_set_bitmap
);
2439 /* Also keep a record of the last instruction to modify memory.
2440 For now this is very trivial, we only record whether any memory
2441 location has been modified. */
2445 /* Return non-zero if the operands of X are not set before INSN in
2446 INSN's basic block. */
2449 oprs_not_set_p (x
, insn
)
2456 /* repeat is used to turn tail-recursion into iteration. */
2462 code
= GET_CODE (x
);
2477 if (mem_last_set
!= 0)
2483 return ! TEST_BIT (reg_set_bitmap
, REGNO (x
));
2489 fmt
= GET_RTX_FORMAT (code
);
2490 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
2495 /* If we are about to do the last recursive call
2496 needed at this level, change it into iteration.
2497 This function is called enough to be worth it. */
2503 not_set_p
= oprs_not_set_p (XEXP (x
, i
), insn
);
2507 else if (fmt
[i
] == 'E')
2510 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
2512 int not_set_p
= oprs_not_set_p (XVECEXP (x
, i
, j
), insn
);
2522 /* Mark things set by a CALL. */
2528 mem_last_set
= INSN_CUID (insn
);
2531 /* Mark things set by a SET. */
2534 mark_set (pat
, insn
)
2537 rtx dest
= SET_DEST (pat
);
2539 while (GET_CODE (dest
) == SUBREG
2540 || GET_CODE (dest
) == ZERO_EXTRACT
2541 || GET_CODE (dest
) == SIGN_EXTRACT
2542 || GET_CODE (dest
) == STRICT_LOW_PART
)
2543 dest
= XEXP (dest
, 0);
2545 if (GET_CODE (dest
) == REG
)
2546 SET_BIT (reg_set_bitmap
, REGNO (dest
));
2547 else if (GET_CODE (dest
) == MEM
)
2548 mem_last_set
= INSN_CUID (insn
);
2550 if (GET_CODE (SET_SRC (pat
)) == CALL
)
2554 /* Record things set by a CLOBBER. */
2557 mark_clobber (pat
, insn
)
2560 rtx clob
= XEXP (pat
, 0);
2562 while (GET_CODE (clob
) == SUBREG
|| GET_CODE (clob
) == STRICT_LOW_PART
)
2563 clob
= XEXP (clob
, 0);
2565 if (GET_CODE (clob
) == REG
)
2566 SET_BIT (reg_set_bitmap
, REGNO (clob
));
2568 mem_last_set
= INSN_CUID (insn
);
2571 /* Record things set by INSN.
2572 This data is used by oprs_not_set_p. */
2575 mark_oprs_set (insn
)
2578 rtx pat
= PATTERN (insn
);
2580 if (GET_CODE (pat
) == SET
)
2581 mark_set (pat
, insn
);
2582 else if (GET_CODE (pat
) == PARALLEL
)
2586 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
2588 rtx x
= XVECEXP (pat
, 0, i
);
2590 if (GET_CODE (x
) == SET
)
2592 else if (GET_CODE (x
) == CLOBBER
)
2593 mark_clobber (x
, insn
);
2594 else if (GET_CODE (x
) == CALL
)
2598 else if (GET_CODE (pat
) == CLOBBER
)
2599 mark_clobber (pat
, insn
);
2600 else if (GET_CODE (pat
) == CALL
)
2605 /* Classic GCSE reaching definition support. */
2607 /* Allocate reaching def variables. */
2610 alloc_rd_mem (n_blocks
, n_insns
)
2611 int n_blocks
, n_insns
;
2613 rd_kill
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_insns
);
2614 sbitmap_vector_zero (rd_kill
, n_basic_blocks
);
2616 rd_gen
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_insns
);
2617 sbitmap_vector_zero (rd_gen
, n_basic_blocks
);
2619 reaching_defs
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_insns
);
2620 sbitmap_vector_zero (reaching_defs
, n_basic_blocks
);
2622 rd_out
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_insns
);
2623 sbitmap_vector_zero (rd_out
, n_basic_blocks
);
2626 /* Free reaching def variables. */
2633 free (reaching_defs
);
2637 /* Add INSN to the kills of BB.
2638 REGNO, set in BB, is killed by INSN. */
2641 handle_rd_kill_set (insn
, regno
, bb
)
2645 struct reg_set
*this_reg
= reg_set_table
[regno
];
2649 if (BLOCK_NUM (this_reg
->insn
) != BLOCK_NUM (insn
))
2650 SET_BIT (rd_kill
[bb
], INSN_CUID (this_reg
->insn
));
2651 this_reg
= this_reg
->next
;
2655 /* Compute the set of kill's for reaching definitions. */
2663 For each set bit in `gen' of the block (i.e each insn which
2664 generates a definition in the block)
2665 Call the reg set by the insn corresponding to that bit regx
2666 Look at the linked list starting at reg_set_table[regx]
2667 For each setting of regx in the linked list, which is not in
2669 Set the bit in `kill' corresponding to that insn
2672 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
2674 for (cuid
= 0; cuid
< max_cuid
; cuid
++)
2676 if (TEST_BIT (rd_gen
[bb
], cuid
))
2678 rtx insn
= CUID_INSN (cuid
);
2679 rtx pat
= PATTERN (insn
);
2681 if (GET_CODE (insn
) == CALL_INSN
)
2685 for (regno
= 0; regno
< FIRST_PSEUDO_REGISTER
; regno
++)
2687 if ((call_used_regs
[regno
]
2688 && regno
!= STACK_POINTER_REGNUM
2689 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2690 && regno
!= HARD_FRAME_POINTER_REGNUM
2692 #if ARG_POINTER_REGNUM != FRAME_POINTER_REGNUM
2693 && ! (regno
== ARG_POINTER_REGNUM
2694 && fixed_regs
[regno
])
2696 #if defined (PIC_OFFSET_TABLE_REGNUM) && !defined (PIC_OFFSET_TABLE_REG_CALL_CLOBBERED)
2697 && ! (regno
== PIC_OFFSET_TABLE_REGNUM
&& flag_pic
)
2699 && regno
!= FRAME_POINTER_REGNUM
)
2700 || global_regs
[regno
])
2701 handle_rd_kill_set (insn
, regno
, bb
);
2705 if (GET_CODE (pat
) == PARALLEL
)
2709 /* We work backwards because ... */
2710 for (i
= XVECLEN (pat
, 0) - 1; i
>= 0; i
--)
2712 enum rtx_code code
= GET_CODE (XVECEXP (pat
, 0, i
));
2713 if ((code
== SET
|| code
== CLOBBER
)
2714 && GET_CODE (XEXP (XVECEXP (pat
, 0, i
), 0)) == REG
)
2715 handle_rd_kill_set (insn
,
2716 REGNO (XEXP (XVECEXP (pat
, 0, i
), 0)),
2720 else if (GET_CODE (pat
) == SET
)
2722 if (GET_CODE (SET_DEST (pat
)) == REG
)
2724 /* Each setting of this register outside of this block
2725 must be marked in the set of kills in this block. */
2726 handle_rd_kill_set (insn
, REGNO (SET_DEST (pat
)), bb
);
2729 /* FIXME: CLOBBER? */
2735 /* Compute the reaching definitions as in
2736 Compilers Principles, Techniques, and Tools. Aho, Sethi, Ullman,
2737 Chapter 10. It is the same algorithm as used for computing available
2738 expressions but applied to the gens and kills of reaching definitions. */
2743 int bb
, changed
, passes
;
2745 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
2746 sbitmap_copy (rd_out
[bb
] /*dst*/, rd_gen
[bb
] /*src*/);
2753 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
2755 sbitmap_union_of_preds (reaching_defs
[bb
], rd_out
, bb
);
2756 changed
|= sbitmap_union_of_diff (rd_out
[bb
], rd_gen
[bb
],
2757 reaching_defs
[bb
], rd_kill
[bb
]);
2763 fprintf (gcse_file
, "reaching def computation: %d passes\n", passes
);
2766 /* Classic GCSE available expression support. */
2768 /* Allocate memory for available expression computation. */
2771 alloc_avail_expr_mem (n_blocks
, n_exprs
)
2772 int n_blocks
, n_exprs
;
2774 ae_kill
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_exprs
);
2775 sbitmap_vector_zero (ae_kill
, n_basic_blocks
);
2777 ae_gen
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_exprs
);
2778 sbitmap_vector_zero (ae_gen
, n_basic_blocks
);
2780 ae_in
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_exprs
);
2781 sbitmap_vector_zero (ae_in
, n_basic_blocks
);
2783 ae_out
= (sbitmap
*) sbitmap_vector_alloc (n_blocks
, n_exprs
);
2784 sbitmap_vector_zero (ae_out
, n_basic_blocks
);
2786 u_bitmap
= (sbitmap
) sbitmap_alloc (n_exprs
);
2787 sbitmap_ones (u_bitmap
);
2791 free_avail_expr_mem ()
2800 /* Compute the set of available expressions generated in each basic block. */
2807 /* For each recorded occurrence of each expression, set ae_gen[bb][expr].
2808 This is all we have to do because an expression is not recorded if it
2809 is not available, and the only expressions we want to work with are the
2810 ones that are recorded. */
2812 for (i
= 0; i
< expr_hash_table_size
; i
++)
2814 struct expr
*expr
= expr_hash_table
[i
];
2815 while (expr
!= NULL
)
2817 struct occr
*occr
= expr
->avail_occr
;
2818 while (occr
!= NULL
)
2820 SET_BIT (ae_gen
[BLOCK_NUM (occr
->insn
)], expr
->bitmap_index
);
2823 expr
= expr
->next_same_hash
;
2828 /* Return non-zero if expression X is killed in BB. */
2831 expr_killed_p (x
, bb
)
2839 /* repeat is used to turn tail-recursion into iteration. */
2845 code
= GET_CODE (x
);
2849 return TEST_BIT (reg_set_in_block
[bb
], REGNO (x
));
2852 if (mem_set_in_block
[bb
])
2872 i
= GET_RTX_LENGTH (code
) - 1;
2873 fmt
= GET_RTX_FORMAT (code
);
2878 rtx tem
= XEXP (x
, i
);
2880 /* If we are about to do the last recursive call
2881 needed at this level, change it into iteration.
2882 This function is called enough to be worth it. */
2888 if (expr_killed_p (tem
, bb
))
2891 else if (fmt
[i
] == 'E')
2894 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
2896 if (expr_killed_p (XVECEXP (x
, i
, j
), bb
))
2905 /* Compute the set of available expressions killed in each basic block. */
2908 compute_ae_kill (ae_gen
, ae_kill
)
2909 sbitmap
*ae_gen
, *ae_kill
;
2913 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
2915 for (i
= 0; i
< expr_hash_table_size
; i
++)
2917 struct expr
*expr
= expr_hash_table
[i
];
2919 for ( ; expr
!= NULL
; expr
= expr
->next_same_hash
)
2921 /* Skip EXPR if generated in this block. */
2922 if (TEST_BIT (ae_gen
[bb
], expr
->bitmap_index
))
2925 if (expr_killed_p (expr
->expr
, bb
))
2926 SET_BIT (ae_kill
[bb
], expr
->bitmap_index
);
2932 /* Actually perform the Classic GCSE optimizations. */
2934 /* Return non-zero if occurrence OCCR of expression EXPR reaches block BB.
2936 CHECK_SELF_LOOP is non-zero if we should consider a block reaching itself
2937 as a positive reach. We want to do this when there are two computations
2938 of the expression in the block.
2940 VISITED is a pointer to a working buffer for tracking which BB's have
2941 been visited. It is NULL for the top-level call.
2943 We treat reaching expressions that go through blocks containing the same
2944 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
2945 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
2946 2 as not reaching. The intent is to improve the probability of finding
2947 only one reaching expression and to reduce register lifetimes by picking
2948 the closest such expression. */
2951 expr_reaches_here_p_work (occr
, expr
, bb
, check_self_loop
, visited
)
2955 int check_self_loop
;
2960 for (pred
= BASIC_BLOCK(bb
)->pred
; pred
!= NULL
; pred
= pred
->pred_next
)
2962 int pred_bb
= pred
->src
->index
;
2964 if (visited
[pred_bb
])
2966 /* This predecessor has already been visited.
2970 else if (pred_bb
== bb
)
2972 /* BB loops on itself. */
2974 && TEST_BIT (ae_gen
[pred_bb
], expr
->bitmap_index
)
2975 && BLOCK_NUM (occr
->insn
) == pred_bb
)
2977 visited
[pred_bb
] = 1;
2979 /* Ignore this predecessor if it kills the expression. */
2980 else if (TEST_BIT (ae_kill
[pred_bb
], expr
->bitmap_index
))
2981 visited
[pred_bb
] = 1;
2982 /* Does this predecessor generate this expression? */
2983 else if (TEST_BIT (ae_gen
[pred_bb
], expr
->bitmap_index
))
2985 /* Is this the occurrence we're looking for?
2986 Note that there's only one generating occurrence per block
2987 so we just need to check the block number. */
2988 if (BLOCK_NUM (occr
->insn
) == pred_bb
)
2990 visited
[pred_bb
] = 1;
2992 /* Neither gen nor kill. */
2995 visited
[pred_bb
] = 1;
2996 if (expr_reaches_here_p_work (occr
, expr
, pred_bb
, check_self_loop
,
3002 /* All paths have been checked. */
3006 /* This wrapper for expr_reaches_here_p_work() is to ensure that any
3007 memory allocated for that function is returned. */
3010 expr_reaches_here_p (occr
, expr
, bb
, check_self_loop
)
3014 int check_self_loop
;
3017 char * visited
= (char *) xcalloc (n_basic_blocks
, 1);
3019 rval
= expr_reaches_here_p_work(occr
, expr
, bb
, check_self_loop
, visited
);
3026 /* Return the instruction that computes EXPR that reaches INSN's basic block.
3027 If there is more than one such instruction, return NULL.
3029 Called only by handle_avail_expr. */
3032 computing_insn (expr
, insn
)
3036 int bb
= BLOCK_NUM (insn
);
3038 if (expr
->avail_occr
->next
== NULL
)
3040 if (BLOCK_NUM (expr
->avail_occr
->insn
) == bb
)
3042 /* The available expression is actually itself
3043 (i.e. a loop in the flow graph) so do nothing. */
3046 /* (FIXME) Case that we found a pattern that was created by
3047 a substitution that took place. */
3048 return expr
->avail_occr
->insn
;
3052 /* Pattern is computed more than once.
3053 Search backwards from this insn to see how many of these
3054 computations actually reach this insn. */
3056 rtx insn_computes_expr
= NULL
;
3059 for (occr
= expr
->avail_occr
; occr
!= NULL
; occr
= occr
->next
)
3061 if (BLOCK_NUM (occr
->insn
) == bb
)
3063 /* The expression is generated in this block.
3064 The only time we care about this is when the expression
3065 is generated later in the block [and thus there's a loop].
3066 We let the normal cse pass handle the other cases. */
3067 if (INSN_CUID (insn
) < INSN_CUID (occr
->insn
))
3069 if (expr_reaches_here_p (occr
, expr
, bb
, 1))
3074 insn_computes_expr
= occr
->insn
;
3078 else /* Computation of the pattern outside this block. */
3080 if (expr_reaches_here_p (occr
, expr
, bb
, 0))
3085 insn_computes_expr
= occr
->insn
;
3090 if (insn_computes_expr
== NULL
)
3092 return insn_computes_expr
;
3096 /* Return non-zero if the definition in DEF_INSN can reach INSN.
3097 Only called by can_disregard_other_sets. */
3100 def_reaches_here_p (insn
, def_insn
)
3105 if (TEST_BIT (reaching_defs
[BLOCK_NUM (insn
)], INSN_CUID (def_insn
)))
3108 if (BLOCK_NUM (insn
) == BLOCK_NUM (def_insn
))
3110 if (INSN_CUID (def_insn
) < INSN_CUID (insn
))
3112 if (GET_CODE (PATTERN (def_insn
)) == PARALLEL
)
3114 if (GET_CODE (PATTERN (def_insn
)) == CLOBBER
)
3115 reg
= XEXP (PATTERN (def_insn
), 0);
3116 else if (GET_CODE (PATTERN (def_insn
)) == SET
)
3117 reg
= SET_DEST (PATTERN (def_insn
));
3120 return ! reg_set_between_p (reg
, NEXT_INSN (def_insn
), insn
);
3129 /* Return non-zero if *ADDR_THIS_REG can only have one value at INSN.
3130 The value returned is the number of definitions that reach INSN.
3131 Returning a value of zero means that [maybe] more than one definition
3132 reaches INSN and the caller can't perform whatever optimization it is
3133 trying. i.e. it is always safe to return zero. */
3136 can_disregard_other_sets (addr_this_reg
, insn
, for_combine
)
3137 struct reg_set
**addr_this_reg
;
3141 int number_of_reaching_defs
= 0;
3142 struct reg_set
*this_reg
= *addr_this_reg
;
3146 if (def_reaches_here_p (insn
, this_reg
->insn
))
3148 number_of_reaching_defs
++;
3149 /* Ignore parallels for now. */
3150 if (GET_CODE (PATTERN (this_reg
->insn
)) == PARALLEL
)
3153 && (GET_CODE (PATTERN (this_reg
->insn
)) == CLOBBER
3154 || ! rtx_equal_p (SET_SRC (PATTERN (this_reg
->insn
)),
3155 SET_SRC (PATTERN (insn
)))))
3157 /* A setting of the reg to a different value reaches INSN. */
3160 if (number_of_reaching_defs
> 1)
3162 /* If in this setting the value the register is being
3163 set to is equal to the previous value the register
3164 was set to and this setting reaches the insn we are
3165 trying to do the substitution on then we are ok. */
3167 if (GET_CODE (PATTERN (this_reg
->insn
)) == CLOBBER
)
3169 if (! rtx_equal_p (SET_SRC (PATTERN (this_reg
->insn
)),
3170 SET_SRC (PATTERN (insn
))))
3173 *addr_this_reg
= this_reg
;
3176 /* prev_this_reg = this_reg; */
3177 this_reg
= this_reg
->next
;
3180 return number_of_reaching_defs
;
3183 /* Expression computed by insn is available and the substitution is legal,
3184 so try to perform the substitution.
3186 The result is non-zero if any changes were made. */
3189 handle_avail_expr (insn
, expr
)
3193 rtx pat
, insn_computes_expr
;
3195 struct reg_set
*this_reg
;
3196 int found_setting
, use_src
;
3199 /* We only handle the case where one computation of the expression
3200 reaches this instruction. */
3201 insn_computes_expr
= computing_insn (expr
, insn
);
3202 if (insn_computes_expr
== NULL
)
3208 /* At this point we know only one computation of EXPR outside of this
3209 block reaches this insn. Now try to find a register that the
3210 expression is computed into. */
3212 if (GET_CODE (SET_SRC (PATTERN (insn_computes_expr
))) == REG
)
3214 /* This is the case when the available expression that reaches
3215 here has already been handled as an available expression. */
3216 int regnum_for_replacing
= REGNO (SET_SRC (PATTERN (insn_computes_expr
)));
3217 /* If the register was created by GCSE we can't use `reg_set_table',
3218 however we know it's set only once. */
3219 if (regnum_for_replacing
>= max_gcse_regno
3220 /* If the register the expression is computed into is set only once,
3221 or only one set reaches this insn, we can use it. */
3222 || (((this_reg
= reg_set_table
[regnum_for_replacing
]),
3223 this_reg
->next
== NULL
)
3224 || can_disregard_other_sets (&this_reg
, insn
, 0)))
3233 int regnum_for_replacing
= REGNO (SET_DEST (PATTERN (insn_computes_expr
)));
3234 /* This shouldn't happen. */
3235 if (regnum_for_replacing
>= max_gcse_regno
)
3237 this_reg
= reg_set_table
[regnum_for_replacing
];
3238 /* If the register the expression is computed into is set only once,
3239 or only one set reaches this insn, use it. */
3240 if (this_reg
->next
== NULL
3241 || can_disregard_other_sets (&this_reg
, insn
, 0))
3247 pat
= PATTERN (insn
);
3249 to
= SET_SRC (PATTERN (insn_computes_expr
));
3251 to
= SET_DEST (PATTERN (insn_computes_expr
));
3252 changed
= validate_change (insn
, &SET_SRC (pat
), to
, 0);
3254 /* We should be able to ignore the return code from validate_change but
3255 to play it safe we check. */
3259 if (gcse_file
!= NULL
)
3261 fprintf (gcse_file
, "GCSE: Replacing the source in insn %d with reg %d %s insn %d\n",
3262 INSN_UID (insn
), REGNO (to
),
3263 use_src
? "from" : "set in",
3264 INSN_UID (insn_computes_expr
));
3269 /* The register that the expr is computed into is set more than once. */
3270 else if (1 /*expensive_op(this_pattrn->op) && do_expensive_gcse)*/)
3272 /* Insert an insn after insnx that copies the reg set in insnx
3273 into a new pseudo register call this new register REGN.
3274 From insnb until end of basic block or until REGB is set
3275 replace all uses of REGB with REGN. */
3278 to
= gen_reg_rtx (GET_MODE (SET_DEST (PATTERN (insn_computes_expr
))));
3280 /* Generate the new insn. */
3281 /* ??? If the change fails, we return 0, even though we created
3282 an insn. I think this is ok. */
3284 = emit_insn_after (gen_rtx_SET (VOIDmode
, to
,
3285 SET_DEST (PATTERN (insn_computes_expr
))),
3286 insn_computes_expr
);
3287 /* Keep block number table up to date. */
3288 set_block_num (new_insn
, BLOCK_NUM (insn_computes_expr
));
3289 /* Keep register set table up to date. */
3290 record_one_set (REGNO (to
), new_insn
);
3292 gcse_create_count
++;
3293 if (gcse_file
!= NULL
)
3295 fprintf (gcse_file
, "GCSE: Creating insn %d to copy value of reg %d, computed in insn %d,\n",
3296 INSN_UID (NEXT_INSN (insn_computes_expr
)),
3297 REGNO (SET_SRC (PATTERN (NEXT_INSN (insn_computes_expr
)))),
3298 INSN_UID (insn_computes_expr
));
3299 fprintf (gcse_file
, " into newly allocated reg %d\n", REGNO (to
));
3302 pat
= PATTERN (insn
);
3304 /* Do register replacement for INSN. */
3305 changed
= validate_change (insn
, &SET_SRC (pat
),
3306 SET_DEST (PATTERN (NEXT_INSN (insn_computes_expr
))),
3309 /* We should be able to ignore the return code from validate_change but
3310 to play it safe we check. */
3314 if (gcse_file
!= NULL
)
3316 fprintf (gcse_file
, "GCSE: Replacing the source in insn %d with reg %d set in insn %d\n",
3318 REGNO (SET_DEST (PATTERN (NEXT_INSN (insn_computes_expr
)))),
3319 INSN_UID (insn_computes_expr
));
3328 /* Perform classic GCSE.
3329 This is called by one_classic_gcse_pass after all the dataflow analysis
3332 The result is non-zero if a change was made. */
3340 /* Note we start at block 1. */
3343 for (bb
= 1; bb
< n_basic_blocks
; bb
++)
3345 /* Reset tables used to keep track of what's still valid [since the
3346 start of the block]. */
3347 reset_opr_set_tables ();
3349 for (insn
= BLOCK_HEAD (bb
);
3350 insn
!= NULL
&& insn
!= NEXT_INSN (BLOCK_END (bb
));
3351 insn
= NEXT_INSN (insn
))
3353 /* Is insn of form (set (pseudo-reg) ...)? */
3355 if (GET_CODE (insn
) == INSN
3356 && GET_CODE (PATTERN (insn
)) == SET
3357 && GET_CODE (SET_DEST (PATTERN (insn
))) == REG
3358 && REGNO (SET_DEST (PATTERN (insn
))) >= FIRST_PSEUDO_REGISTER
)
3360 rtx pat
= PATTERN (insn
);
3361 rtx src
= SET_SRC (pat
);
3364 if (want_to_gcse_p (src
)
3365 /* Is the expression recorded? */
3366 && ((expr
= lookup_expr (src
)) != NULL
)
3367 /* Is the expression available [at the start of the
3369 && TEST_BIT (ae_in
[bb
], expr
->bitmap_index
)
3370 /* Are the operands unchanged since the start of the
3372 && oprs_not_set_p (src
, insn
))
3373 changed
|= handle_avail_expr (insn
, expr
);
3376 /* Keep track of everything modified by this insn. */
3377 /* ??? Need to be careful w.r.t. mods done to INSN. */
3378 if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i')
3379 mark_oprs_set (insn
);
3386 /* Top level routine to perform one classic GCSE pass.
3388 Return non-zero if a change was made. */
3391 one_classic_gcse_pass (pass
)
3396 gcse_subst_count
= 0;
3397 gcse_create_count
= 0;
3399 alloc_expr_hash_table (max_cuid
);
3400 alloc_rd_mem (n_basic_blocks
, max_cuid
);
3401 compute_expr_hash_table ();
3403 dump_hash_table (gcse_file
, "Expression", expr_hash_table
,
3404 expr_hash_table_size
, n_exprs
);
3409 alloc_avail_expr_mem (n_basic_blocks
, n_exprs
);
3411 compute_ae_kill (ae_gen
, ae_kill
);
3412 compute_available (ae_gen
, ae_kill
, ae_out
, ae_in
);
3413 changed
= classic_gcse ();
3414 free_avail_expr_mem ();
3417 free_expr_hash_table ();
3421 fprintf (gcse_file
, "\n");
3422 fprintf (gcse_file
, "GCSE of %s, pass %d: %d bytes needed, %d substs, %d insns created\n",
3423 current_function_name
, pass
,
3424 bytes_used
, gcse_subst_count
, gcse_create_count
);
3430 /* Compute copy/constant propagation working variables. */
3432 /* Local properties of assignments. */
3434 static sbitmap
*cprop_pavloc
;
3435 static sbitmap
*cprop_absaltered
;
3437 /* Global properties of assignments (computed from the local properties). */
3439 static sbitmap
*cprop_avin
;
3440 static sbitmap
*cprop_avout
;
3442 /* Allocate vars used for copy/const propagation.
3443 N_BLOCKS is the number of basic blocks.
3444 N_SETS is the number of sets. */
3447 alloc_cprop_mem (n_blocks
, n_sets
)
3448 int n_blocks
, n_sets
;
3450 cprop_pavloc
= sbitmap_vector_alloc (n_blocks
, n_sets
);
3451 cprop_absaltered
= sbitmap_vector_alloc (n_blocks
, n_sets
);
3453 cprop_avin
= sbitmap_vector_alloc (n_blocks
, n_sets
);
3454 cprop_avout
= sbitmap_vector_alloc (n_blocks
, n_sets
);
3457 /* Free vars used by copy/const propagation. */
3462 free (cprop_pavloc
);
3463 free (cprop_absaltered
);
3468 /* For each block, compute whether X is transparent.
3469 X is either an expression or an assignment [though we don't care which,
3470 for this context an assignment is treated as an expression].
3471 For each block where an element of X is modified, set (SET_P == 1) or reset
3472 (SET_P == 0) the INDX bit in BMAP. */
3475 compute_transp (x
, indx
, bmap
, set_p
)
3485 /* repeat is used to turn tail-recursion into iteration. */
3491 code
= GET_CODE (x
);
3497 int regno
= REGNO (x
);
3501 if (regno
< FIRST_PSEUDO_REGISTER
)
3503 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
3504 if (TEST_BIT (reg_set_in_block
[bb
], regno
))
3505 SET_BIT (bmap
[bb
], indx
);
3509 for (r
= reg_set_table
[regno
]; r
!= NULL
; r
= r
->next
)
3511 bb
= BLOCK_NUM (r
->insn
);
3512 SET_BIT (bmap
[bb
], indx
);
3518 if (regno
< FIRST_PSEUDO_REGISTER
)
3520 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
3521 if (TEST_BIT (reg_set_in_block
[bb
], regno
))
3522 RESET_BIT (bmap
[bb
], indx
);
3526 for (r
= reg_set_table
[regno
]; r
!= NULL
; r
= r
->next
)
3528 bb
= BLOCK_NUM (r
->insn
);
3529 RESET_BIT (bmap
[bb
], indx
);
3539 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
3540 if (mem_set_in_block
[bb
])
3541 SET_BIT (bmap
[bb
], indx
);
3545 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
3546 if (mem_set_in_block
[bb
])
3547 RESET_BIT (bmap
[bb
], indx
);
3567 i
= GET_RTX_LENGTH (code
) - 1;
3568 fmt
= GET_RTX_FORMAT (code
);
3573 rtx tem
= XEXP (x
, i
);
3575 /* If we are about to do the last recursive call
3576 needed at this level, change it into iteration.
3577 This function is called enough to be worth it. */
3583 compute_transp (tem
, indx
, bmap
, set_p
);
3585 else if (fmt
[i
] == 'E')
3588 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
3589 compute_transp (XVECEXP (x
, i
, j
), indx
, bmap
, set_p
);
3594 /* Compute the available expressions at the start and end of each
3595 basic block for cprop. This particular dataflow equation is
3596 used often enough that we might want to generalize it and make
3597 as a subroutine for other global optimizations that need available
3598 in/out information. */
3600 compute_cprop_avinout ()
3602 int bb
, changed
, passes
;
3604 sbitmap_zero (cprop_avin
[0]);
3605 sbitmap_vector_ones (cprop_avout
, n_basic_blocks
);
3612 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
3615 sbitmap_intersection_of_preds (cprop_avin
[bb
], cprop_avout
, bb
);
3616 changed
|= sbitmap_union_of_diff (cprop_avout
[bb
],
3619 cprop_absaltered
[bb
]);
3625 fprintf (gcse_file
, "cprop avail expr computation: %d passes\n", passes
);
3628 /* Top level routine to do the dataflow analysis needed by copy/const
3632 compute_cprop_data ()
3634 compute_local_properties (cprop_absaltered
, cprop_pavloc
, NULL
, 1);
3635 compute_cprop_avinout ();
3638 /* Copy/constant propagation. */
3640 /* Maximum number of register uses in an insn that we handle. */
3643 /* Table of uses found in an insn.
3644 Allocated statically to avoid alloc/free complexity and overhead. */
3645 static struct reg_use reg_use_table
[MAX_USES
];
3647 /* Index into `reg_use_table' while building it. */
3648 static int reg_use_count
;
3650 /* Set up a list of register numbers used in INSN.
3651 The found uses are stored in `reg_use_table'.
3652 `reg_use_count' is initialized to zero before entry, and
3653 contains the number of uses in the table upon exit.
3655 ??? If a register appears multiple times we will record it multiple
3656 times. This doesn't hurt anything but it will slow things down. */
3666 /* repeat is used to turn tail-recursion into iteration. */
3672 code
= GET_CODE (x
);
3676 if (reg_use_count
== MAX_USES
)
3678 reg_use_table
[reg_use_count
].reg_rtx
= x
;
3696 case ASM_INPUT
: /*FIXME*/
3700 if (GET_CODE (SET_DEST (x
)) == MEM
)
3701 find_used_regs (SET_DEST (x
));
3709 /* Recursively scan the operands of this expression. */
3711 fmt
= GET_RTX_FORMAT (code
);
3712 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
3716 /* If we are about to do the last recursive call
3717 needed at this level, change it into iteration.
3718 This function is called enough to be worth it. */
3724 find_used_regs (XEXP (x
, i
));
3726 else if (fmt
[i
] == 'E')
3729 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
3730 find_used_regs (XVECEXP (x
, i
, j
));
3735 /* Try to replace all non-SET_DEST occurrences of FROM in INSN with TO.
3736 Returns non-zero is successful. */
3739 try_replace_reg (from
, to
, insn
)
3742 /* If this fails we could try to simplify the result of the
3743 replacement and attempt to recognize the simplified insn.
3745 But we need a general simplify_rtx that doesn't have pass
3746 specific state variables. I'm not aware of one at the moment. */
3747 return validate_replace_src (from
, to
, insn
);
3750 /* Find a set of REGNO that is available on entry to INSN's block.
3751 Returns NULL if not found. */
3753 static struct expr
*
3754 find_avail_set (regno
, insn
)
3758 /* SET1 contains the last set found that can be returned to the caller for
3759 use in a substitution. */
3760 struct expr
*set1
= 0;
3762 /* Loops are not possible here. To get a loop we would need two sets
3763 available at the start of the block containing INSN. ie we would
3764 need two sets like this available at the start of the block:
3766 (set (reg X) (reg Y))
3767 (set (reg Y) (reg X))
3769 This can not happen since the set of (reg Y) would have killed the
3770 set of (reg X) making it unavailable at the start of this block. */
3774 struct expr
*set
= lookup_set (regno
, NULL_RTX
);
3776 /* Find a set that is available at the start of the block
3777 which contains INSN. */
3780 if (TEST_BIT (cprop_avin
[BLOCK_NUM (insn
)], set
->bitmap_index
))
3782 set
= next_set (regno
, set
);
3785 /* If no available set was found we've reached the end of the
3786 (possibly empty) copy chain. */
3790 if (GET_CODE (set
->expr
) != SET
)
3793 src
= SET_SRC (set
->expr
);
3795 /* We know the set is available.
3796 Now check that SRC is ANTLOC (i.e. none of the source operands
3797 have changed since the start of the block).
3799 If the source operand changed, we may still use it for the next
3800 iteration of this loop, but we may not use it for substitutions. */
3801 if (CONSTANT_P (src
) || oprs_not_set_p (src
, insn
))
3804 /* If the source of the set is anything except a register, then
3805 we have reached the end of the copy chain. */
3806 if (GET_CODE (src
) != REG
)
3809 /* Follow the copy chain, ie start another iteration of the loop
3810 and see if we have an available copy into SRC. */
3811 regno
= REGNO (src
);
3814 /* SET1 holds the last set that was available and anticipatable at
3819 /* Subroutine of cprop_insn that tries to propagate constants into
3820 JUMP_INSNS. INSN must be a conditional jump; COPY is a copy of it
3821 that we can use for substitutions.
3822 REG_USED is the use we will try to replace, SRC is the constant we
3823 will try to substitute for it.
3824 Returns nonzero if a change was made. */
3826 cprop_jump (insn
, copy
, reg_used
, src
)
3828 struct reg_use
*reg_used
;
3831 rtx set
= PATTERN (copy
);
3834 /* Replace the register with the appropriate constant. */
3835 replace_rtx (SET_SRC (set
), reg_used
->reg_rtx
, src
);
3837 temp
= simplify_ternary_operation (GET_CODE (SET_SRC (set
)),
3838 GET_MODE (SET_SRC (set
)),
3839 GET_MODE (XEXP (SET_SRC (set
), 0)),
3840 XEXP (SET_SRC (set
), 0),
3841 XEXP (SET_SRC (set
), 1),
3842 XEXP (SET_SRC (set
), 2));
3844 /* If no simplification can be made, then try the next
3849 SET_SRC (set
) = temp
;
3851 /* That may have changed the structure of TEMP, so
3852 force it to be rerecognized if it has not turned
3853 into a nop or unconditional jump. */
3855 INSN_CODE (copy
) = -1;
3856 if ((SET_DEST (set
) == pc_rtx
3857 && (SET_SRC (set
) == pc_rtx
3858 || GET_CODE (SET_SRC (set
)) == LABEL_REF
))
3859 || recog (PATTERN (copy
), copy
, NULL
) >= 0)
3861 /* This has either become an unconditional jump
3862 or a nop-jump. We'd like to delete nop jumps
3863 here, but doing so confuses gcse. So we just
3864 make the replacement and let later passes
3866 PATTERN (insn
) = set
;
3867 INSN_CODE (insn
) = -1;
3869 /* One less use of the label this insn used to jump to
3870 if we turned this into a NOP jump. */
3871 if (SET_SRC (set
) == pc_rtx
&& JUMP_LABEL (insn
) != 0)
3872 --LABEL_NUSES (JUMP_LABEL (insn
));
3874 /* If this has turned into an unconditional jump,
3875 then put a barrier after it so that the unreachable
3876 code will be deleted. */
3877 if (GET_CODE (SET_SRC (set
)) == LABEL_REF
)
3878 emit_barrier_after (insn
);
3880 run_jump_opt_after_gcse
= 1;
3883 if (gcse_file
!= NULL
)
3885 int regno
= REGNO (reg_used
->reg_rtx
);
3886 fprintf (gcse_file
, "CONST-PROP: Replacing reg %d in insn %d with constant ",
3887 regno
, INSN_UID (insn
));
3888 print_rtl (gcse_file
, src
);
3889 fprintf (gcse_file
, "\n");
3897 /* Subroutine of cprop_insn that tries to propagate constants into
3898 JUMP_INSNS for machines that have CC0. INSN is a single set that
3899 stores into CC0; the insn following it is a conditional jump.
3900 REG_USED is the use we will try to replace, SRC is the constant we
3901 will try to substitute for it.
3902 Returns nonzero if a change was made. */
3904 cprop_cc0_jump (insn
, reg_used
, src
)
3906 struct reg_use
*reg_used
;
3909 rtx jump
= NEXT_INSN (insn
);
3910 rtx copy
= copy_rtx (jump
);
3911 rtx set
= PATTERN (copy
);
3913 /* We need to copy the source of the cc0 setter, as cprop_jump is going to
3914 substitute into it. */
3915 replace_rtx (SET_SRC (set
), cc0_rtx
, copy_rtx (SET_SRC (PATTERN (insn
))));
3916 if (! cprop_jump (jump
, copy
, reg_used
, src
))
3919 /* If we succeeded, delete the cc0 setter. */
3920 PUT_CODE (insn
, NOTE
);
3921 NOTE_LINE_NUMBER (insn
) = NOTE_INSN_DELETED
;
3922 NOTE_SOURCE_FILE (insn
) = 0;
3927 /* Perform constant and copy propagation on INSN.
3928 The result is non-zero if a change was made. */
3931 cprop_insn (insn
, alter_jumps
)
3935 struct reg_use
*reg_used
;
3938 /* Only propagate into SETs. Note that a conditional jump is a
3939 SET with pc_rtx as the destination. */
3940 if ((GET_CODE (insn
) != INSN
3941 && GET_CODE (insn
) != JUMP_INSN
)
3942 || GET_CODE (PATTERN (insn
)) != SET
)
3946 find_used_regs (PATTERN (insn
));
3948 reg_used
= ®_use_table
[0];
3949 for ( ; reg_use_count
> 0; reg_used
++, reg_use_count
--)
3953 int regno
= REGNO (reg_used
->reg_rtx
);
3955 /* Ignore registers created by GCSE.
3956 We do this because ... */
3957 if (regno
>= max_gcse_regno
)
3960 /* If the register has already been set in this block, there's
3961 nothing we can do. */
3962 if (! oprs_not_set_p (reg_used
->reg_rtx
, insn
))
3965 /* Find an assignment that sets reg_used and is available
3966 at the start of the block. */
3967 set
= find_avail_set (regno
, insn
);
3972 /* ??? We might be able to handle PARALLELs. Later. */
3973 if (GET_CODE (pat
) != SET
)
3975 src
= SET_SRC (pat
);
3977 /* Constant propagation. */
3978 if (GET_CODE (src
) == CONST_INT
|| GET_CODE (src
) == CONST_DOUBLE
3979 || GET_CODE (src
) == SYMBOL_REF
)
3981 /* Handle normal insns first. */
3982 if (GET_CODE (insn
) == INSN
3983 && try_replace_reg (reg_used
->reg_rtx
, src
, insn
))
3987 if (gcse_file
!= NULL
)
3989 fprintf (gcse_file
, "CONST-PROP: Replacing reg %d in insn %d with constant ",
3990 regno
, INSN_UID (insn
));
3991 print_rtl (gcse_file
, src
);
3992 fprintf (gcse_file
, "\n");
3995 /* The original insn setting reg_used may or may not now be
3996 deletable. We leave the deletion to flow. */
3999 /* Try to propagate a CONST_INT into a conditional jump.
4000 We're pretty specific about what we will handle in this
4001 code, we can extend this as necessary over time.
4003 Right now the insn in question must look like
4004 (set (pc) (if_then_else ...)) */
4005 else if (alter_jumps
4006 && GET_CODE (insn
) == JUMP_INSN
4007 && condjump_p (insn
)
4008 && ! simplejump_p (insn
))
4009 changed
|= cprop_jump (insn
, copy_rtx (insn
), reg_used
, src
);
4011 /* Similar code for machines that use a pair of CC0 setter and
4012 conditional jump insn. */
4013 else if (alter_jumps
4014 && GET_CODE (PATTERN (insn
)) == SET
4015 && SET_DEST (PATTERN (insn
)) == cc0_rtx
4016 && GET_CODE (NEXT_INSN (insn
)) == JUMP_INSN
4017 && condjump_p (NEXT_INSN (insn
))
4018 && ! simplejump_p (NEXT_INSN (insn
)))
4019 changed
|= cprop_cc0_jump (insn
, reg_used
, src
);
4022 else if (GET_CODE (src
) == REG
4023 && REGNO (src
) >= FIRST_PSEUDO_REGISTER
4024 && REGNO (src
) != regno
)
4026 if (try_replace_reg (reg_used
->reg_rtx
, src
, insn
))
4030 if (gcse_file
!= NULL
)
4032 fprintf (gcse_file
, "COPY-PROP: Replacing reg %d in insn %d with reg %d\n",
4033 regno
, INSN_UID (insn
), REGNO (src
));
4036 /* The original insn setting reg_used may or may not now be
4037 deletable. We leave the deletion to flow. */
4038 /* FIXME: If it turns out that the insn isn't deletable,
4039 then we may have unnecessarily extended register lifetimes
4040 and made things worse. */
4048 /* Forward propagate copies.
4049 This includes copies and constants.
4050 Return non-zero if a change was made. */
4059 /* Note we start at block 1. */
4062 for (bb
= 1; bb
< n_basic_blocks
; bb
++)
4064 /* Reset tables used to keep track of what's still valid [since the
4065 start of the block]. */
4066 reset_opr_set_tables ();
4068 for (insn
= BLOCK_HEAD (bb
);
4069 insn
!= NULL
&& insn
!= NEXT_INSN (BLOCK_END (bb
));
4070 insn
= NEXT_INSN (insn
))
4072 if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i')
4074 changed
|= cprop_insn (insn
, alter_jumps
);
4076 /* Keep track of everything modified by this insn. */
4077 /* ??? Need to be careful w.r.t. mods done to INSN. Don't
4078 call mark_oprs_set if we turned the insn into a NOTE. */
4079 if (GET_CODE (insn
) != NOTE
)
4080 mark_oprs_set (insn
);
4085 if (gcse_file
!= NULL
)
4086 fprintf (gcse_file
, "\n");
4091 /* Perform one copy/constant propagation pass.
4092 F is the first insn in the function.
4093 PASS is the pass count. */
4096 one_cprop_pass (pass
, alter_jumps
)
4102 const_prop_count
= 0;
4103 copy_prop_count
= 0;
4105 alloc_set_hash_table (max_cuid
);
4106 compute_set_hash_table ();
4108 dump_hash_table (gcse_file
, "SET", set_hash_table
, set_hash_table_size
,
4112 alloc_cprop_mem (n_basic_blocks
, n_sets
);
4113 compute_cprop_data ();
4114 changed
= cprop (alter_jumps
);
4117 free_set_hash_table ();
4121 fprintf (gcse_file
, "CPROP of %s, pass %d: %d bytes needed, %d const props, %d copy props\n",
4122 current_function_name
, pass
,
4123 bytes_used
, const_prop_count
, copy_prop_count
);
4124 fprintf (gcse_file
, "\n");
4130 /* Compute PRE+LCM working variables. */
4132 /* Local properties of expressions. */
4133 /* Nonzero for expressions that are transparent in the block. */
4134 static sbitmap
*transp
;
4136 /* Nonzero for expressions that are transparent at the end of the block.
4137 This is only zero for expressions killed by abnormal critical edge
4138 created by a calls. */
4139 static sbitmap
*transpout
;
4141 /* Nonzero for expressions that are computed (available) in the block. */
4142 static sbitmap
*comp
;
4144 /* Nonzero for expressions that are locally anticipatable in the block. */
4145 static sbitmap
*antloc
;
4147 /* Nonzero for expressions where this block is an optimal computation
4149 static sbitmap
*pre_optimal
;
4151 /* Nonzero for expressions which are redundant in a particular block. */
4152 static sbitmap
*pre_redundant
;
4154 /* Nonzero for expressions which should be inserted on a specific edge. */
4155 static sbitmap
*pre_insert_map
;
4157 /* Nonzero for expressions which should be deleted in a specific block. */
4158 static sbitmap
*pre_delete_map
;
4160 /* Contains the edge_list returned by pre_edge_lcm. */
4161 static struct edge_list
*edge_list
;
4163 static sbitmap
*temp_bitmap
;
4165 /* Redundant insns. */
4166 static sbitmap pre_redundant_insns
;
4168 /* Allocate vars used for PRE analysis. */
4171 alloc_pre_mem (n_blocks
, n_exprs
)
4172 int n_blocks
, n_exprs
;
4174 transp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4175 comp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4176 antloc
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4177 temp_bitmap
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4180 pre_redundant
= NULL
;
4181 pre_insert_map
= NULL
;
4182 pre_delete_map
= NULL
;
4186 transpout
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4187 ae_kill
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4188 /* pre_insert and pre_delete are allocated later. */
4191 /* Free vars used for PRE analysis. */
4204 free (pre_redundant
);
4206 free (pre_insert_map
);
4208 free (pre_delete_map
);
4221 transp
= comp
= antloc
= NULL
;
4222 pre_optimal
= pre_redundant
= pre_insert_map
= pre_delete_map
= NULL
;
4223 transpout
= ae_in
= ae_out
= ae_kill
= NULL
;
4228 /* Top level routine to do the dataflow analysis needed by PRE. */
4233 compute_local_properties (transp
, comp
, antloc
, 0);
4234 compute_transpout ();
4235 sbitmap_vector_zero (ae_kill
, n_basic_blocks
);
4236 compute_ae_kill (comp
, ae_kill
);
4237 edge_list
= pre_edge_lcm (gcse_file
, n_exprs
, transp
, comp
, antloc
,
4238 ae_kill
, &pre_insert_map
, &pre_delete_map
);
4244 /* Return non-zero if an occurrence of expression EXPR in OCCR_BB would reach
4247 VISITED is a pointer to a working buffer for tracking which BB's have
4248 been visited. It is NULL for the top-level call.
4250 CHECK_PRE_COMP controls whether or not we check for a computation of
4253 We treat reaching expressions that go through blocks containing the same
4254 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
4255 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
4256 2 as not reaching. The intent is to improve the probability of finding
4257 only one reaching expression and to reduce register lifetimes by picking
4258 the closest such expression. */
4261 pre_expr_reaches_here_p_work (occr_bb
, expr
, bb
, check_pre_comp
, visited
)
4270 for (pred
= BASIC_BLOCK (bb
)->pred
; pred
!= NULL
; pred
= pred
->pred_next
)
4272 int pred_bb
= pred
->src
->index
;
4274 if (pred
->src
== ENTRY_BLOCK_PTR
4275 /* Has predecessor has already been visited? */
4276 || visited
[pred_bb
])
4278 /* Nothing to do. */
4280 /* Does this predecessor generate this expression? */
4281 else if ((!check_pre_comp
&& occr_bb
== pred_bb
)
4282 || TEST_BIT (comp
[pred_bb
], expr
->bitmap_index
))
4284 /* Is this the occurrence we're looking for?
4285 Note that there's only one generating occurrence per block
4286 so we just need to check the block number. */
4287 if (occr_bb
== pred_bb
)
4289 visited
[pred_bb
] = 1;
4291 /* Ignore this predecessor if it kills the expression. */
4292 else if (! TEST_BIT (transp
[pred_bb
], expr
->bitmap_index
))
4293 visited
[pred_bb
] = 1;
4294 /* Neither gen nor kill. */
4297 visited
[pred_bb
] = 1;
4298 if (pre_expr_reaches_here_p_work (occr_bb
, expr
, pred_bb
,
4299 check_pre_comp
, visited
))
4304 /* All paths have been checked. */
4308 /* The wrapper for pre_expr_reaches_here_work that ensures that any
4309 memory allocated for that function is returned. */
4312 pre_expr_reaches_here_p (occr_bb
, expr
, bb
, check_pre_comp
)
4319 char * visited
= (char *) xcalloc (n_basic_blocks
, 1);
4321 rval
= pre_expr_reaches_here_p_work(occr_bb
, expr
, bb
, check_pre_comp
,
4330 /* Given an expr, generate RTL which we can insert at the end of a BB,
4331 or on an edge. Set the block number of any insns generated to
4335 process_insert_insn (expr
)
4338 rtx reg
= expr
->reaching_reg
;
4339 rtx pat
, copied_expr
;
4343 copied_expr
= copy_rtx (expr
->expr
);
4344 emit_move_insn (reg
, copied_expr
);
4345 first_new_insn
= get_insns ();
4346 pat
= gen_sequence ();
4352 /* Add EXPR to the end of basic block BB.
4354 This is used by both the PRE and code hoisting.
4356 For PRE, we want to verify that the expr is either transparent
4357 or locally anticipatable in the target block. This check makes
4358 no sense for code hoisting. */
4361 insert_insn_end_bb (expr
, bb
, pre
)
4366 rtx insn
= BLOCK_END (bb
);
4368 rtx reg
= expr
->reaching_reg
;
4369 int regno
= REGNO (reg
);
4372 pat
= process_insert_insn (expr
);
4374 /* If the last insn is a jump, insert EXPR in front [taking care to
4375 handle cc0, etc. properly]. */
4377 if (GET_CODE (insn
) == JUMP_INSN
)
4383 /* If this is a jump table, then we can't insert stuff here. Since
4384 we know the previous real insn must be the tablejump, we insert
4385 the new instruction just before the tablejump. */
4386 if (GET_CODE (PATTERN (insn
)) == ADDR_VEC
4387 || GET_CODE (PATTERN (insn
)) == ADDR_DIFF_VEC
)
4388 insn
= prev_real_insn (insn
);
4391 /* FIXME: 'twould be nice to call prev_cc0_setter here but it aborts
4392 if cc0 isn't set. */
4393 note
= find_reg_note (insn
, REG_CC_SETTER
, NULL_RTX
);
4395 insn
= XEXP (note
, 0);
4398 rtx maybe_cc0_setter
= prev_nonnote_insn (insn
);
4399 if (maybe_cc0_setter
4400 && GET_RTX_CLASS (GET_CODE (maybe_cc0_setter
)) == 'i'
4401 && sets_cc0_p (PATTERN (maybe_cc0_setter
)))
4402 insn
= maybe_cc0_setter
;
4405 /* FIXME: What if something in cc0/jump uses value set in new insn? */
4406 new_insn
= emit_insn_before (pat
, insn
);
4407 if (BLOCK_HEAD (bb
) == insn
)
4408 BLOCK_HEAD (bb
) = new_insn
;
4410 /* Likewise if the last insn is a call, as will happen in the presence
4411 of exception handling. */
4412 else if (GET_CODE (insn
) == CALL_INSN
)
4414 HARD_REG_SET parm_regs
;
4418 /* Keeping in mind SMALL_REGISTER_CLASSES and parameters in registers,
4419 we search backward and place the instructions before the first
4420 parameter is loaded. Do this for everyone for consistency and a
4421 presumtion that we'll get better code elsewhere as well. */
4423 /* It should always be the case that we can put these instructions
4424 anywhere in the basic block with performing PRE optimizations.
4427 && !TEST_BIT (antloc
[bb
], expr
->bitmap_index
)
4428 && !TEST_BIT (transp
[bb
], expr
->bitmap_index
))
4431 /* Since different machines initialize their parameter registers
4432 in different orders, assume nothing. Collect the set of all
4433 parameter registers. */
4434 CLEAR_HARD_REG_SET (parm_regs
);
4436 for (p
= CALL_INSN_FUNCTION_USAGE (insn
); p
; p
= XEXP (p
, 1))
4437 if (GET_CODE (XEXP (p
, 0)) == USE
4438 && GET_CODE (XEXP (XEXP (p
, 0), 0)) == REG
)
4440 int regno
= REGNO (XEXP (XEXP (p
, 0), 0));
4441 if (regno
>= FIRST_PSEUDO_REGISTER
)
4443 SET_HARD_REG_BIT (parm_regs
, regno
);
4447 /* Search backward for the first set of a register in this set. */
4448 while (nparm_regs
&& BLOCK_HEAD (bb
) != insn
)
4450 insn
= PREV_INSN (insn
);
4451 p
= single_set (insn
);
4452 if (p
&& GET_CODE (SET_DEST (p
)) == REG
4453 && REGNO (SET_DEST (p
)) < FIRST_PSEUDO_REGISTER
4454 && TEST_HARD_REG_BIT (parm_regs
, REGNO (SET_DEST (p
))))
4456 CLEAR_HARD_REG_BIT (parm_regs
, REGNO (SET_DEST (p
)));
4461 /* If we found all the parameter loads, then we want to insert
4462 before the first parameter load.
4464 If we did not find all the parameter loads, then we might have
4465 stopped on the head of the block, which could be a CODE_LABEL.
4466 If we inserted before the CODE_LABEL, then we would be putting
4467 the insn in the wrong basic block. In that case, put the insn
4468 after the CODE_LABEL.
4470 ?!? Do we need to account for NOTE_INSN_BASIC_BLOCK here? */
4471 if (GET_CODE (insn
) != CODE_LABEL
)
4473 new_insn
= emit_insn_before (pat
, insn
);
4474 if (BLOCK_HEAD (bb
) == insn
)
4475 BLOCK_HEAD (bb
) = new_insn
;
4479 new_insn
= emit_insn_after (pat
, insn
);
4484 new_insn
= emit_insn_after (pat
, insn
);
4485 BLOCK_END (bb
) = new_insn
;
4488 /* Keep block number table up to date.
4489 Note, PAT could be a multiple insn sequence, we have to make
4490 sure that each insn in the sequence is handled. */
4491 if (GET_CODE (pat
) == SEQUENCE
)
4495 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
4497 rtx insn
= XVECEXP (pat
, 0, i
);
4498 set_block_num (insn
, bb
);
4499 if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i')
4500 add_label_notes (PATTERN (insn
), new_insn
);
4501 note_stores (PATTERN (insn
), record_set_info
, insn
);
4506 add_label_notes (SET_SRC (pat
), new_insn
);
4507 set_block_num (new_insn
, bb
);
4508 /* Keep register set table up to date. */
4509 record_one_set (regno
, new_insn
);
4512 gcse_create_count
++;
4516 fprintf (gcse_file
, "PRE/HOIST: end of bb %d, insn %d, copying expression %d to reg %d\n",
4517 bb
, INSN_UID (new_insn
), expr
->bitmap_index
, regno
);
4521 /* Insert partially redundant expressions on edges in the CFG to make
4522 the expressions fully redundant. */
4525 pre_edge_insert (edge_list
, index_map
)
4526 struct edge_list
*edge_list
;
4527 struct expr
**index_map
;
4529 int e
, i
, num_edges
, set_size
, did_insert
= 0;
4532 /* Where PRE_INSERT_MAP is nonzero, we add the expression on that edge
4533 if it reaches any of the deleted expressions. */
4535 set_size
= pre_insert_map
[0]->size
;
4536 num_edges
= NUM_EDGES (edge_list
);
4537 inserted
= sbitmap_vector_alloc (num_edges
, n_exprs
);
4538 sbitmap_vector_zero (inserted
, num_edges
);
4540 for (e
= 0; e
< num_edges
; e
++)
4543 basic_block pred
= INDEX_EDGE_PRED_BB (edge_list
, e
);
4544 int bb
= pred
->index
;
4546 for (i
= indx
= 0; i
< set_size
; i
++, indx
+= SBITMAP_ELT_BITS
)
4548 SBITMAP_ELT_TYPE insert
= pre_insert_map
[e
]->elms
[i
];
4551 for (j
= indx
; insert
&& j
< n_exprs
; j
++, insert
>>= 1)
4553 if ((insert
& 1) != 0 && index_map
[j
]->reaching_reg
!= NULL_RTX
)
4555 struct expr
*expr
= index_map
[j
];
4558 /* Now look at each deleted occurence of this expression. */
4559 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
4561 if (! occr
->deleted_p
)
4564 /* Insert this expression on this edge if if it would
4565 reach the deleted occurence in BB. */
4566 if (!TEST_BIT (inserted
[e
], j
)
4567 && (bb
== ENTRY_BLOCK
4568 || pre_expr_reaches_here_p (bb
, expr
,
4569 BLOCK_NUM (occr
->insn
), 0)))
4572 edge eg
= INDEX_EDGE (edge_list
, e
);
4573 /* We can't insert anything on an abnormal
4574 and critical edge, so we insert the
4575 insn at the end of the previous block. There
4576 are several alternatives detailed in
4577 Morgans book P277 (sec 10.5) for handling
4578 this situation. This one is easiest for now. */
4580 if ((eg
->flags
& EDGE_ABNORMAL
) == EDGE_ABNORMAL
)
4582 insert_insn_end_bb (index_map
[j
], bb
, 0);
4586 insn
= process_insert_insn (index_map
[j
]);
4587 insert_insn_on_edge (insn
, eg
);
4592 "PRE/HOIST: edge (%d,%d), copy expression %d\n",
4594 INDEX_EDGE_SUCC_BB (edge_list
, e
)->index
, expr
->bitmap_index
);
4596 SET_BIT (inserted
[e
], j
);
4598 gcse_create_count
++;
4612 /* Copy the result of INSN to REG.
4613 INDX is the expression number. */
4616 pre_insert_copy_insn (expr
, insn
)
4620 rtx reg
= expr
->reaching_reg
;
4621 int regno
= REGNO (reg
);
4622 int indx
= expr
->bitmap_index
;
4623 rtx set
= single_set (insn
);
4625 int bb
= BLOCK_NUM (insn
);
4629 new_insn
= emit_insn_after (gen_rtx_SET (VOIDmode
, reg
, SET_DEST (set
)),
4631 /* Keep block number table up to date. */
4632 set_block_num (new_insn
, bb
);
4633 /* Keep register set table up to date. */
4634 record_one_set (regno
, new_insn
);
4635 if (insn
== BLOCK_END (bb
))
4636 BLOCK_END (bb
) = new_insn
;
4638 gcse_create_count
++;
4642 "PRE: bb %d, insn %d, copy expression %d in insn %d to reg %d\n",
4643 BLOCK_NUM (insn
), INSN_UID (new_insn
), indx
,
4644 INSN_UID (insn
), regno
);
4647 /* Copy available expressions that reach the redundant expression
4648 to `reaching_reg'. */
4651 pre_insert_copies ()
4655 /* For each available expression in the table, copy the result to
4656 `reaching_reg' if the expression reaches a deleted one.
4658 ??? The current algorithm is rather brute force.
4659 Need to do some profiling. */
4661 for (i
= 0; i
< expr_hash_table_size
; i
++)
4665 for (expr
= expr_hash_table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
4669 /* If the basic block isn't reachable, PPOUT will be TRUE.
4670 However, we don't want to insert a copy here because the
4671 expression may not really be redundant. So only insert
4672 an insn if the expression was deleted.
4673 This test also avoids further processing if the expression
4674 wasn't deleted anywhere. */
4675 if (expr
->reaching_reg
== NULL
)
4678 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
4682 if (! occr
->deleted_p
)
4685 for (avail
= expr
->avail_occr
; avail
!= NULL
; avail
= avail
->next
)
4687 rtx insn
= avail
->insn
;
4689 /* No need to handle this one if handled already. */
4690 if (avail
->copied_p
)
4692 /* Don't handle this one if it's a redundant one. */
4693 if (TEST_BIT (pre_redundant_insns
, INSN_CUID (insn
)))
4695 /* Or if the expression doesn't reach the deleted one. */
4696 if (! pre_expr_reaches_here_p (BLOCK_NUM (avail
->insn
), expr
,
4697 BLOCK_NUM (occr
->insn
),1))
4700 /* Copy the result of avail to reaching_reg. */
4701 pre_insert_copy_insn (expr
, insn
);
4702 avail
->copied_p
= 1;
4709 /* Delete redundant computations.
4710 Deletion is done by changing the insn to copy the `reaching_reg' of
4711 the expression into the result of the SET. It is left to later passes
4712 (cprop, cse2, flow, combine, regmove) to propagate the copy or eliminate it.
4714 Returns non-zero if a change is made. */
4721 /* Compute the expressions which are redundant and need to be replaced by
4722 copies from the reaching reg to the target reg. */
4723 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
4724 sbitmap_copy (temp_bitmap
[bb
], pre_delete_map
[bb
]);
4727 for (i
= 0; i
< expr_hash_table_size
; i
++)
4731 for (expr
= expr_hash_table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
4734 int indx
= expr
->bitmap_index
;
4736 /* We only need to search antic_occr since we require
4739 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
4741 rtx insn
= occr
->insn
;
4743 int bb
= BLOCK_NUM (insn
);
4745 if (TEST_BIT (temp_bitmap
[bb
], indx
))
4747 set
= single_set (insn
);
4751 /* Create a pseudo-reg to store the result of reaching
4752 expressions into. Get the mode for the new pseudo
4753 from the mode of the original destination pseudo. */
4754 if (expr
->reaching_reg
== NULL
)
4756 = gen_reg_rtx (GET_MODE (SET_DEST (set
)));
4758 /* In theory this should never fail since we're creating
4761 However, on the x86 some of the movXX patterns actually
4762 contain clobbers of scratch regs. This may cause the
4763 insn created by validate_change to not match any pattern
4764 and thus cause validate_change to fail. */
4765 if (validate_change (insn
, &SET_SRC (set
),
4766 expr
->reaching_reg
, 0))
4768 occr
->deleted_p
= 1;
4769 SET_BIT (pre_redundant_insns
, INSN_CUID (insn
));
4777 "PRE: redundant insn %d (expression %d) in bb %d, reaching reg is %d\n",
4778 INSN_UID (insn
), indx
, bb
, REGNO (expr
->reaching_reg
));
4788 /* Perform GCSE optimizations using PRE.
4789 This is called by one_pre_gcse_pass after all the dataflow analysis
4792 This is based on the original Morel-Renvoise paper Fred Chow's thesis,
4793 and lazy code motion from Knoop, Ruthing and Steffen as described in
4794 Advanced Compiler Design and Implementation.
4796 ??? A new pseudo reg is created to hold the reaching expression.
4797 The nice thing about the classical approach is that it would try to
4798 use an existing reg. If the register can't be adequately optimized
4799 [i.e. we introduce reload problems], one could add a pass here to
4800 propagate the new register through the block.
4802 ??? We don't handle single sets in PARALLELs because we're [currently]
4803 not able to copy the rest of the parallel when we insert copies to create
4804 full redundancies from partial redundancies. However, there's no reason
4805 why we can't handle PARALLELs in the cases where there are no partial
4813 struct expr
**index_map
;
4815 /* Compute a mapping from expression number (`bitmap_index') to
4816 hash table entry. */
4818 index_map
= xcalloc (n_exprs
, sizeof (struct expr
*));
4819 for (i
= 0; i
< expr_hash_table_size
; i
++)
4823 for (expr
= expr_hash_table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
4824 index_map
[expr
->bitmap_index
] = expr
;
4827 /* Reset bitmap used to track which insns are redundant. */
4828 pre_redundant_insns
= sbitmap_alloc (max_cuid
);
4829 sbitmap_zero (pre_redundant_insns
);
4831 /* Delete the redundant insns first so that
4832 - we know what register to use for the new insns and for the other
4833 ones with reaching expressions
4834 - we know which insns are redundant when we go to create copies */
4835 changed
= pre_delete ();
4837 did_insert
= pre_edge_insert (edge_list
, index_map
);
4838 /* In other places with reaching expressions, copy the expression to the
4839 specially allocated pseudo-reg that reaches the redundant expr. */
4840 pre_insert_copies ();
4843 commit_edge_insertions ();
4848 free (pre_redundant_insns
);
4853 /* Top level routine to perform one PRE GCSE pass.
4855 Return non-zero if a change was made. */
4858 one_pre_gcse_pass (pass
)
4863 gcse_subst_count
= 0;
4864 gcse_create_count
= 0;
4866 alloc_expr_hash_table (max_cuid
);
4867 add_noreturn_fake_exit_edges ();
4868 compute_expr_hash_table ();
4870 dump_hash_table (gcse_file
, "Expression", expr_hash_table
,
4871 expr_hash_table_size
, n_exprs
);
4874 alloc_pre_mem (n_basic_blocks
, n_exprs
);
4875 compute_pre_data ();
4876 changed
|= pre_gcse ();
4877 free_edge_list (edge_list
);
4880 remove_fake_edges ();
4881 free_expr_hash_table ();
4885 fprintf (gcse_file
, "\n");
4886 fprintf (gcse_file
, "PRE GCSE of %s, pass %d: %d bytes needed, %d substs, %d insns created\n",
4887 current_function_name
, pass
,
4888 bytes_used
, gcse_subst_count
, gcse_create_count
);
4894 /* If X contains any LABEL_REF's, add REG_LABEL notes for them to INSN.
4895 We have to add REG_LABEL notes, because the following loop optimization
4896 pass requires them. */
4898 /* ??? This is very similar to the loop.c add_label_notes function. We
4899 could probably share code here. */
4901 /* ??? If there was a jump optimization pass after gcse and before loop,
4902 then we would not need to do this here, because jump would add the
4903 necessary REG_LABEL notes. */
4906 add_label_notes (x
, insn
)
4910 enum rtx_code code
= GET_CODE (x
);
4914 if (code
== LABEL_REF
&& !LABEL_REF_NONLOCAL_P (x
))
4916 /* This code used to ignore labels that referred to dispatch tables to
4917 avoid flow generating (slighly) worse code.
4919 We no longer ignore such label references (see LABEL_REF handling in
4920 mark_jump_label for additional information). */
4921 REG_NOTES (insn
) = gen_rtx_EXPR_LIST (REG_LABEL
, XEXP (x
, 0),
4926 fmt
= GET_RTX_FORMAT (code
);
4927 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
4930 add_label_notes (XEXP (x
, i
), insn
);
4931 else if (fmt
[i
] == 'E')
4932 for (j
= XVECLEN (x
, i
) - 1; j
>= 0; j
--)
4933 add_label_notes (XVECEXP (x
, i
, j
), insn
);
4937 /* Compute transparent outgoing information for each block.
4939 An expression is transparent to an edge unless it is killed by
4940 the edge itself. This can only happen with abnormal control flow,
4941 when the edge is traversed through a call. This happens with
4942 non-local labels and exceptions.
4944 This would not be necessary if we split the edge. While this is
4945 normally impossible for abnormal critical edges, with some effort
4946 it should be possible with exception handling, since we still have
4947 control over which handler should be invoked. But due to increased
4948 EH table sizes, this may not be worthwhile. */
4951 compute_transpout ()
4955 sbitmap_vector_ones (transpout
, n_basic_blocks
);
4957 for (bb
= 0; bb
< n_basic_blocks
; ++bb
)
4961 /* Note that flow inserted a nop a the end of basic blocks that
4962 end in call instructions for reasons other than abnormal
4964 if (GET_CODE (BLOCK_END (bb
)) != CALL_INSN
)
4967 for (i
= 0; i
< expr_hash_table_size
; i
++)
4970 for (expr
= expr_hash_table
[i
]; expr
; expr
= expr
->next_same_hash
)
4971 if (GET_CODE (expr
->expr
) == MEM
)
4973 rtx addr
= XEXP (expr
->expr
, 0);
4975 if (GET_CODE (addr
) == SYMBOL_REF
4976 && CONSTANT_POOL_ADDRESS_P (addr
))
4979 /* ??? Optimally, we would use interprocedural alias
4980 analysis to determine if this mem is actually killed
4982 RESET_BIT (transpout
[bb
], expr
->bitmap_index
);
4988 /* Removal of useless null pointer checks */
4990 /* Called via note_stores. X is set by SETTER. If X is a register we must
4991 invalidate nonnull_local and set nonnull_killed. DATA is really a
4992 `null_pointer_info *'.
4994 We ignore hard registers. */
4996 invalidate_nonnull_info (x
, setter
, data
)
4998 rtx setter ATTRIBUTE_UNUSED
;
5002 struct null_pointer_info
* npi
= (struct null_pointer_info
*) data
;
5005 while (GET_CODE (x
) == SUBREG
)
5008 /* Ignore anything that is not a register or is a hard register. */
5009 if (GET_CODE (x
) != REG
5010 || REGNO (x
) < npi
->min_reg
5011 || REGNO (x
) >= npi
->max_reg
)
5014 regno
= REGNO (x
) - npi
->min_reg
;
5016 RESET_BIT (npi
->nonnull_local
[npi
->current_block
], regno
);
5017 SET_BIT (npi
->nonnull_killed
[npi
->current_block
], regno
);
5020 /* Do null-pointer check elimination for the registers indicated in
5021 NPI. NONNULL_AVIN and NONNULL_AVOUT are pre-allocated sbitmaps;
5022 they are not our responsibility to free. */
5025 delete_null_pointer_checks_1 (s_preds
, block_reg
, nonnull_avin
,
5027 int_list_ptr
*s_preds
;
5029 sbitmap
*nonnull_avin
;
5030 sbitmap
*nonnull_avout
;
5031 struct null_pointer_info
*npi
;
5035 sbitmap
*nonnull_local
= npi
->nonnull_local
;
5036 sbitmap
*nonnull_killed
= npi
->nonnull_killed
;
5038 /* Compute local properties, nonnull and killed. A register will have
5039 the nonnull property if at the end of the current block its value is
5040 known to be nonnull. The killed property indicates that somewhere in
5041 the block any information we had about the register is killed.
5043 Note that a register can have both properties in a single block. That
5044 indicates that it's killed, then later in the block a new value is
5046 sbitmap_vector_zero (nonnull_local
, n_basic_blocks
);
5047 sbitmap_vector_zero (nonnull_killed
, n_basic_blocks
);
5048 for (current_block
= 0; current_block
< n_basic_blocks
; current_block
++)
5050 rtx insn
, stop_insn
;
5052 /* Set the current block for invalidate_nonnull_info. */
5053 npi
->current_block
= current_block
;
5055 /* Scan each insn in the basic block looking for memory references and
5057 stop_insn
= NEXT_INSN (BLOCK_END (current_block
));
5058 for (insn
= BLOCK_HEAD (current_block
);
5060 insn
= NEXT_INSN (insn
))
5065 /* Ignore anything that is not a normal insn. */
5066 if (GET_RTX_CLASS (GET_CODE (insn
)) != 'i')
5069 /* Basically ignore anything that is not a simple SET. We do have
5070 to make sure to invalidate nonnull_local and set nonnull_killed
5071 for such insns though. */
5072 set
= single_set (insn
);
5075 note_stores (PATTERN (insn
), invalidate_nonnull_info
, npi
);
5079 /* See if we've got a useable memory load. We handle it first
5080 in case it uses its address register as a dest (which kills
5081 the nonnull property). */
5082 if (GET_CODE (SET_SRC (set
)) == MEM
5083 && GET_CODE ((reg
= XEXP (SET_SRC (set
), 0))) == REG
5084 && REGNO (reg
) >= npi
->min_reg
5085 && REGNO (reg
) < npi
->max_reg
)
5086 SET_BIT (nonnull_local
[current_block
],
5087 REGNO (reg
) - npi
->min_reg
);
5089 /* Now invalidate stuff clobbered by this insn. */
5090 note_stores (PATTERN (insn
), invalidate_nonnull_info
, npi
);
5092 /* And handle stores, we do these last since any sets in INSN can
5093 not kill the nonnull property if it is derived from a MEM
5094 appearing in a SET_DEST. */
5095 if (GET_CODE (SET_DEST (set
)) == MEM
5096 && GET_CODE ((reg
= XEXP (SET_DEST (set
), 0))) == REG
5097 && REGNO (reg
) >= npi
->min_reg
5098 && REGNO (reg
) < npi
->max_reg
)
5099 SET_BIT (nonnull_local
[current_block
],
5100 REGNO (reg
) - npi
->min_reg
);
5104 /* Now compute global properties based on the local properties. This
5105 is a classic global availablity algorithm. */
5106 sbitmap_zero (nonnull_avin
[0]);
5107 sbitmap_vector_ones (nonnull_avout
, n_basic_blocks
);
5113 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
5116 sbitmap_intersect_of_predecessors (nonnull_avin
[bb
],
5117 nonnull_avout
, bb
, s_preds
);
5119 changed
|= sbitmap_union_of_diff (nonnull_avout
[bb
],
5122 nonnull_killed
[bb
]);
5126 /* Now look at each bb and see if it ends with a compare of a value
5128 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
5130 rtx last_insn
= BLOCK_END (bb
);
5131 rtx condition
, earliest
;
5132 int compare_and_branch
;
5134 /* Since MIN_REG is always at least FIRST_PSEUDO_REGISTER, and
5135 since BLOCK_REG[BB] is zero if this block did not end with a
5136 comparison against zero, this condition works. */
5137 if (block_reg
[bb
] < npi
->min_reg
5138 || block_reg
[bb
] >= npi
->max_reg
)
5141 /* LAST_INSN is a conditional jump. Get its condition. */
5142 condition
= get_condition (last_insn
, &earliest
);
5144 /* Is the register known to have a nonzero value? */
5145 if (!TEST_BIT (nonnull_avout
[bb
], block_reg
[bb
] - npi
->min_reg
))
5148 /* Try to compute whether the compare/branch at the loop end is one or
5149 two instructions. */
5150 if (earliest
== last_insn
)
5151 compare_and_branch
= 1;
5152 else if (earliest
== prev_nonnote_insn (last_insn
))
5153 compare_and_branch
= 2;
5157 /* We know the register in this comparison is nonnull at exit from
5158 this block. We can optimize this comparison. */
5159 if (GET_CODE (condition
) == NE
)
5163 new_jump
= emit_jump_insn_before (gen_jump (JUMP_LABEL (last_insn
)),
5165 JUMP_LABEL (new_jump
) = JUMP_LABEL (last_insn
);
5166 LABEL_NUSES (JUMP_LABEL (new_jump
))++;
5167 emit_barrier_after (new_jump
);
5169 delete_insn (last_insn
);
5170 if (compare_and_branch
== 2)
5171 delete_insn (earliest
);
5173 /* Don't check this block again. (Note that BLOCK_END is
5174 invalid here; we deleted the last instruction in the
5180 /* Find EQ/NE comparisons against zero which can be (indirectly) evaluated
5183 This is conceptually similar to global constant/copy propagation and
5184 classic global CSE (it even uses the same dataflow equations as cprop).
5186 If a register is used as memory address with the form (mem (reg)), then we
5187 know that REG can not be zero at that point in the program. Any instruction
5188 which sets REG "kills" this property.
5190 So, if every path leading to a conditional branch has an available memory
5191 reference of that form, then we know the register can not have the value
5192 zero at the conditional branch.
5194 So we merely need to compute the local properies and propagate that data
5195 around the cfg, then optimize where possible.
5197 We run this pass two times. Once before CSE, then again after CSE. This
5198 has proven to be the most profitable approach. It is rare for new
5199 optimization opportunities of this nature to appear after the first CSE
5202 This could probably be integrated with global cprop with a little work. */
5205 delete_null_pointer_checks (f
)
5208 int_list_ptr
*s_preds
, *s_succs
;
5209 int *num_preds
, *num_succs
;
5210 sbitmap
*nonnull_avin
, *nonnull_avout
;
5216 struct null_pointer_info npi
;
5218 /* First break the program into basic blocks. */
5219 find_basic_blocks (f
, max_reg_num (), NULL
, 1);
5221 /* If we have only a single block, then there's nothing to do. */
5222 if (n_basic_blocks
<= 1)
5224 /* Free storage allocated by find_basic_blocks. */
5225 free_basic_block_vars (0);
5229 /* Trying to perform global optimizations on flow graphs which have
5230 a high connectivity will take a long time and is unlikely to be
5231 particularly useful.
5233 In normal circumstances a cfg should have about twice has many edges
5234 as blocks. But we do not want to punish small functions which have
5235 a couple switch statements. So we require a relatively large number
5236 of basic blocks and the ratio of edges to blocks to be high. */
5237 if (n_basic_blocks
> 1000 && n_edges
/ n_basic_blocks
>= 20)
5239 /* Free storage allocated by find_basic_blocks. */
5240 free_basic_block_vars (0);
5244 /* We need predecessor/successor lists as well as pred/succ counts for
5245 each basic block. */
5246 s_preds
= (int_list_ptr
*) gmalloc (n_basic_blocks
* sizeof (int_list_ptr
));
5247 s_succs
= (int_list_ptr
*) gmalloc (n_basic_blocks
* sizeof (int_list_ptr
));
5248 num_preds
= (int *) gmalloc (n_basic_blocks
* sizeof (int));
5249 num_succs
= (int *) gmalloc (n_basic_blocks
* sizeof (int));
5250 compute_preds_succs (s_preds
, s_succs
, num_preds
, num_succs
);
5252 /* We need four bitmaps, each with a bit for each register in each
5254 max_reg
= max_reg_num ();
5255 regs_per_pass
= get_bitmap_width (4, n_basic_blocks
, max_reg
);
5257 /* Allocate bitmaps to hold local and global properties. */
5258 npi
.nonnull_local
= sbitmap_vector_alloc (n_basic_blocks
, regs_per_pass
);
5259 npi
.nonnull_killed
= sbitmap_vector_alloc (n_basic_blocks
, regs_per_pass
);
5260 nonnull_avin
= sbitmap_vector_alloc (n_basic_blocks
, regs_per_pass
);
5261 nonnull_avout
= sbitmap_vector_alloc (n_basic_blocks
, regs_per_pass
);
5263 /* Go through the basic blocks, seeing whether or not each block
5264 ends with a conditional branch whose condition is a comparison
5265 against zero. Record the register compared in BLOCK_REG. */
5266 block_reg
= (int *) xcalloc (n_basic_blocks
, sizeof (int));
5267 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
5269 rtx last_insn
= BLOCK_END (bb
);
5270 rtx condition
, earliest
, reg
;
5272 /* We only want conditional branches. */
5273 if (GET_CODE (last_insn
) != JUMP_INSN
5274 || !condjump_p (last_insn
)
5275 || simplejump_p (last_insn
))
5278 /* LAST_INSN is a conditional jump. Get its condition. */
5279 condition
= get_condition (last_insn
, &earliest
);
5281 /* If we were unable to get the condition, or it is not a equality
5282 comparison against zero then there's nothing we can do. */
5284 || (GET_CODE (condition
) != NE
&& GET_CODE (condition
) != EQ
)
5285 || GET_CODE (XEXP (condition
, 1)) != CONST_INT
5286 || (XEXP (condition
, 1)
5287 != CONST0_RTX (GET_MODE (XEXP (condition
, 0)))))
5290 /* We must be checking a register against zero. */
5291 reg
= XEXP (condition
, 0);
5292 if (GET_CODE (reg
) != REG
)
5295 block_reg
[bb
] = REGNO (reg
);
5298 /* Go through the algorithm for each block of registers. */
5299 for (reg
= FIRST_PSEUDO_REGISTER
; reg
< max_reg
; reg
+= regs_per_pass
)
5302 npi
.max_reg
= MIN (reg
+ regs_per_pass
, max_reg
);
5303 delete_null_pointer_checks_1 (s_preds
, block_reg
, nonnull_avin
,
5304 nonnull_avout
, &npi
);
5307 /* Free storage allocated by find_basic_blocks. */
5308 free_basic_block_vars (0);
5310 /* Free our local predecessor/successor lists. */
5316 /* Free the table of registers compared at the end of every block. */
5320 free (npi
.nonnull_local
);
5321 free (npi
.nonnull_killed
);
5322 free (nonnull_avin
);
5323 free (nonnull_avout
);
5326 /* Code Hoisting variables and subroutines. */
5328 /* Very busy expressions. */
5329 static sbitmap
*hoist_vbein
;
5330 static sbitmap
*hoist_vbeout
;
5332 /* Hoistable expressions. */
5333 static sbitmap
*hoist_exprs
;
5335 /* Dominator bitmaps. */
5336 static sbitmap
*dominators
;
5338 /* ??? We could compute post dominators and run this algorithm in
5339 reverse to to perform tail merging, doing so would probably be
5340 more effective than the tail merging code in jump.c.
5342 It's unclear if tail merging could be run in parallel with
5343 code hoisting. It would be nice. */
5345 /* Allocate vars used for code hoisting analysis. */
5348 alloc_code_hoist_mem (n_blocks
, n_exprs
)
5349 int n_blocks
, n_exprs
;
5351 antloc
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
5352 transp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
5353 comp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
5355 hoist_vbein
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
5356 hoist_vbeout
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
5357 hoist_exprs
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
5358 transpout
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
5360 dominators
= sbitmap_vector_alloc (n_blocks
, n_blocks
);
5363 /* Free vars used for code hoisting analysis. */
5366 free_code_hoist_mem ()
5373 free (hoist_vbeout
);
5380 /* Compute the very busy expressions at entry/exit from each block.
5382 An expression is very busy if all paths from a given point
5383 compute the expression. */
5386 compute_code_hoist_vbeinout ()
5388 int bb
, changed
, passes
;
5390 sbitmap_vector_zero (hoist_vbeout
, n_basic_blocks
);
5391 sbitmap_vector_zero (hoist_vbein
, n_basic_blocks
);
5398 /* We scan the blocks in the reverse order to speed up
5400 for (bb
= n_basic_blocks
- 1; bb
>= 0; bb
--)
5402 changed
|= sbitmap_a_or_b_and_c (hoist_vbein
[bb
], antloc
[bb
],
5403 hoist_vbeout
[bb
], transp
[bb
]);
5404 if (bb
!= n_basic_blocks
- 1)
5405 sbitmap_intersection_of_succs (hoist_vbeout
[bb
], hoist_vbein
, bb
);
5411 fprintf (gcse_file
, "hoisting vbeinout computation: %d passes\n", passes
);
5414 /* Top level routine to do the dataflow analysis needed by code hoisting. */
5417 compute_code_hoist_data ()
5419 compute_local_properties (transp
, comp
, antloc
, 0);
5420 compute_transpout ();
5421 compute_code_hoist_vbeinout ();
5422 compute_flow_dominators (dominators
, NULL
);
5424 fprintf (gcse_file
, "\n");
5427 /* Determine if the expression identified by EXPR_INDEX would
5428 reach BB unimpared if it was placed at the end of EXPR_BB.
5430 It's unclear exactly what Muchnick meant by "unimpared". It seems
5431 to me that the expression must either be computed or transparent in
5432 *every* block in the path(s) from EXPR_BB to BB. Any other definition
5433 would allow the expression to be hoisted out of loops, even if
5434 the expression wasn't a loop invariant.
5436 Contrast this to reachability for PRE where an expression is
5437 considered reachable if *any* path reaches instead of *all*
5441 hoist_expr_reaches_here_p (expr_bb
, expr_index
, bb
, visited
)
5448 int visited_allocated_locally
= 0;
5451 if (visited
== NULL
)
5453 visited_allocated_locally
= 1;
5454 visited
= xcalloc (n_basic_blocks
, 1);
5457 visited
[expr_bb
] = 1;
5458 for (pred
= BASIC_BLOCK (bb
)->pred
; pred
!= NULL
; pred
= pred
->pred_next
)
5460 int pred_bb
= pred
->src
->index
;
5462 if (pred
->src
== ENTRY_BLOCK_PTR
)
5464 else if (visited
[pred_bb
])
5466 /* Does this predecessor generate this expression? */
5467 else if (TEST_BIT (comp
[pred_bb
], expr_index
))
5469 else if (! TEST_BIT (transp
[pred_bb
], expr_index
))
5474 visited
[pred_bb
] = 1;
5475 if (! hoist_expr_reaches_here_p (expr_bb
, expr_index
,
5480 if (visited_allocated_locally
)
5482 return (pred
== NULL
);
5485 /* Actually perform code hoisting. */
5489 int bb
, dominated
, i
;
5490 struct expr
**index_map
;
5492 sbitmap_vector_zero (hoist_exprs
, n_basic_blocks
);
5494 /* Compute a mapping from expression number (`bitmap_index') to
5495 hash table entry. */
5497 index_map
= xcalloc (n_exprs
, sizeof (struct expr
*));
5498 for (i
= 0; i
< expr_hash_table_size
; i
++)
5502 for (expr
= expr_hash_table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
5503 index_map
[expr
->bitmap_index
] = expr
;
5506 /* Walk over each basic block looking for potentially hoistable
5507 expressions, nothing gets hoisted from the entry block. */
5508 for (bb
= 0; bb
< n_basic_blocks
; bb
++)
5511 int insn_inserted_p
;
5513 /* Examine each expression that is very busy at the exit of this
5514 block. These are the potentially hoistable expressions. */
5515 for (i
= 0; i
< hoist_vbeout
[bb
]->n_bits
; i
++)
5518 if (TEST_BIT (hoist_vbeout
[bb
], i
)
5519 && TEST_BIT (transpout
[bb
], i
))
5521 /* We've found a potentially hoistable expression, now
5522 we look at every block BB dominates to see if it
5523 computes the expression. */
5524 for (dominated
= 0; dominated
< n_basic_blocks
; dominated
++)
5526 /* Ignore self dominance. */
5528 || ! TEST_BIT (dominators
[dominated
], bb
))
5531 /* We've found a dominated block, now see if it computes
5532 the busy expression and whether or not moving that
5533 expression to the "beginning" of that block is safe. */
5534 if (!TEST_BIT (antloc
[dominated
], i
))
5537 /* Note if the expression would reach the dominated block
5538 unimpared if it was placed at the end of BB.
5540 Keep track of how many times this expression is hoistable
5541 from a dominated block into BB. */
5542 if (hoist_expr_reaches_here_p (bb
, i
, dominated
, NULL
))
5546 /* If we found more than one hoistable occurence of this
5547 expression, then note it in the bitmap of expressions to
5548 hoist. It makes no sense to hoist things which are computed
5549 in only one BB, and doing so tends to pessimize register
5550 allocation. One could increase this value to try harder
5551 to avoid any possible code expansion due to register
5552 allocation issues; however experiments have shown that
5553 the vast majority of hoistable expressions are only movable
5554 from two successors, so raising this threshhold is likely
5555 to nullify any benefit we get from code hoisting. */
5558 SET_BIT (hoist_exprs
[bb
], i
);
5564 /* If we found nothing to hoist, then quit now. */
5568 /* Loop over all the hoistable expressions. */
5569 for (i
= 0; i
< hoist_exprs
[bb
]->n_bits
; i
++)
5571 /* We want to insert the expression into BB only once, so
5572 note when we've inserted it. */
5573 insn_inserted_p
= 0;
5575 /* These tests should be the same as the tests above. */
5576 if (TEST_BIT (hoist_vbeout
[bb
], i
))
5578 /* We've found a potentially hoistable expression, now
5579 we look at every block BB dominates to see if it
5580 computes the expression. */
5581 for (dominated
= 0; dominated
< n_basic_blocks
; dominated
++)
5583 /* Ignore self dominance. */
5585 || ! TEST_BIT (dominators
[dominated
], bb
))
5588 /* We've found a dominated block, now see if it computes
5589 the busy expression and whether or not moving that
5590 expression to the "beginning" of that block is safe. */
5591 if (!TEST_BIT (antloc
[dominated
], i
))
5594 /* The expression is computed in the dominated block and
5595 it would be safe to compute it at the start of the
5596 dominated block. Now we have to determine if the
5597 expresion would reach the dominated block if it was
5598 placed at the end of BB. */
5599 if (hoist_expr_reaches_here_p (bb
, i
, dominated
, NULL
))
5601 struct expr
*expr
= index_map
[i
];
5602 struct occr
*occr
= expr
->antic_occr
;
5607 /* Find the right occurence of this expression. */
5608 while (BLOCK_NUM (occr
->insn
) != dominated
&& occr
)
5611 /* Should never happen. */
5617 set
= single_set (insn
);
5621 /* Create a pseudo-reg to store the result of reaching
5622 expressions into. Get the mode for the new pseudo
5623 from the mode of the original destination pseudo. */
5624 if (expr
->reaching_reg
== NULL
)
5626 = gen_reg_rtx (GET_MODE (SET_DEST (set
)));
5628 /* In theory this should never fail since we're creating
5631 However, on the x86 some of the movXX patterns actually
5632 contain clobbers of scratch regs. This may cause the
5633 insn created by validate_change to not match any
5634 pattern and thus cause validate_change to fail. */
5635 if (validate_change (insn
, &SET_SRC (set
),
5636 expr
->reaching_reg
, 0))
5638 occr
->deleted_p
= 1;
5639 if (!insn_inserted_p
)
5641 insert_insn_end_bb (index_map
[i
], bb
, 0);
5642 insn_inserted_p
= 1;
5653 /* Top level routine to perform one code hoisting (aka unification) pass
5655 Return non-zero if a change was made. */
5658 one_code_hoisting_pass ()
5662 alloc_expr_hash_table (max_cuid
);
5663 compute_expr_hash_table ();
5665 dump_hash_table (gcse_file
, "Code Hosting Expressions", expr_hash_table
,
5666 expr_hash_table_size
, n_exprs
);
5669 alloc_code_hoist_mem (n_basic_blocks
, n_exprs
);
5670 compute_code_hoist_data ();
5672 free_code_hoist_mem ();
5674 free_expr_hash_table ();