1 /* Partial redundancy elimination / Hoisting for RTL.
2 Copyright (C) 1997-2021 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
21 - reordering of memory allocation and freeing to be more space efficient
22 - calc rough register pressure information and use the info to drive all
23 kinds of code motion (including code hoisting) in a unified way.
26 /* References searched while implementing this.
28 Compilers Principles, Techniques and Tools
32 Global Optimization by Suppression of Partial Redundancies
34 communications of the acm, Vol. 22, Num. 2, Feb. 1979
36 A Portable Machine-Independent Global Optimizer - Design and Measurements
38 Stanford Ph.D. thesis, Dec. 1983
40 A Fast Algorithm for Code Movement Optimization
42 SIGPLAN Notices, Vol. 23, Num. 10, Oct. 1988
44 A Solution to a Problem with Morel and Renvoise's
45 Global Optimization by Suppression of Partial Redundancies
46 K-H Drechsler, M.P. Stadel
47 ACM TOPLAS, Vol. 10, Num. 4, Oct. 1988
49 Practical Adaptation of the Global Optimization
50 Algorithm of Morel and Renvoise
52 ACM TOPLAS, Vol. 13, Num. 2. Apr. 1991
54 Efficiently Computing Static Single Assignment Form and the Control
56 R. Cytron, J. Ferrante, B.K. Rosen, M.N. Wegman, and F.K. Zadeck
57 ACM TOPLAS, Vol. 13, Num. 4, Oct. 1991
60 J. Knoop, O. Ruthing, B. Steffen
61 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
63 What's In a Region? Or Computing Control Dependence Regions in Near-Linear
64 Time for Reducible Flow Control
66 ACM Letters on Programming Languages and Systems,
67 Vol. 2, Num. 1-4, Mar-Dec 1993
69 An Efficient Representation for Sparse Sets
70 Preston Briggs, Linda Torczon
71 ACM Letters on Programming Languages and Systems,
72 Vol. 2, Num. 1-4, Mar-Dec 1993
74 A Variation of Knoop, Ruthing, and Steffen's Lazy Code Motion
75 K-H Drechsler, M.P. Stadel
76 ACM SIGPLAN Notices, Vol. 28, Num. 5, May 1993
78 Partial Dead Code Elimination
79 J. Knoop, O. Ruthing, B. Steffen
80 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
82 Effective Partial Redundancy Elimination
83 P. Briggs, K.D. Cooper
84 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
86 The Program Structure Tree: Computing Control Regions in Linear Time
87 R. Johnson, D. Pearson, K. Pingali
88 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
90 Optimal Code Motion: Theory and Practice
91 J. Knoop, O. Ruthing, B. Steffen
92 ACM TOPLAS, Vol. 16, Num. 4, Jul. 1994
94 The power of assignment motion
95 J. Knoop, O. Ruthing, B. Steffen
96 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
98 Global code motion / global value numbering
100 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
102 Value Driven Redundancy Elimination
104 Rice University Ph.D. thesis, Apr. 1996
108 Massively Scalar Compiler Project, Rice University, Sep. 1996
110 High Performance Compilers for Parallel Computing
114 Advanced Compiler Design and Implementation
116 Morgan Kaufmann, 1997
118 Building an Optimizing Compiler
122 People wishing to speed up the code here should read:
123 Elimination Algorithms for Data Flow Analysis
124 B.G. Ryder, M.C. Paull
125 ACM Computing Surveys, Vol. 18, Num. 3, Sep. 1986
127 How to Analyze Large Programs Efficiently and Informatively
128 D.M. Dhamdhere, B.K. Rosen, F.K. Zadeck
129 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
131 People wishing to do something different can find various possibilities
132 in the above papers and elsewhere.
137 #include "coretypes.h"
144 #include "memmodel.h"
146 #include "insn-config.h"
147 #include "print-rtl.h"
151 #include "diagnostic-core.h"
155 #include "cfgcleanup.h"
158 #include "tree-pass.h"
161 #include "gcse-common.h"
162 #include "function-abi.h"
164 /* We support GCSE via Partial Redundancy Elimination. PRE optimizations
165 are a superset of those done by classic GCSE.
167 Two passes of copy/constant propagation are done around PRE or hoisting
168 because the first one enables more GCSE and the second one helps to clean
169 up the copies that PRE and HOIST create. This is needed more for PRE than
170 for HOIST because code hoisting will try to use an existing register
171 containing the common subexpression rather than create a new one. This is
172 harder to do for PRE because of the code motion (which HOIST doesn't do).
174 Expressions we are interested in GCSE-ing are of the form
175 (set (pseudo-reg) (expression)).
176 Function want_to_gcse_p says what these are.
178 In addition, expressions in REG_EQUAL notes are candidates for GCSE-ing.
179 This allows PRE to hoist expressions that are expressed in multiple insns,
180 such as complex address calculations (e.g. for PIC code, or loads with a
181 high part and a low part).
183 PRE handles moving invariant expressions out of loops (by treating them as
184 partially redundant).
186 **********************
188 We used to support multiple passes but there are diminishing returns in
189 doing so. The first pass usually makes 90% of the changes that are doable.
190 A second pass can make a few more changes made possible by the first pass.
191 Experiments show any further passes don't make enough changes to justify
194 A study of spec92 using an unlimited number of passes:
195 [1 pass] = 1208 substitutions, [2] = 577, [3] = 202, [4] = 192, [5] = 83,
196 [6] = 34, [7] = 17, [8] = 9, [9] = 4, [10] = 4, [11] = 2,
197 [12] = 2, [13] = 1, [15] = 1, [16] = 2, [41] = 1
199 It was found doing copy propagation between each pass enables further
202 This study was done before expressions in REG_EQUAL notes were added as
203 candidate expressions for optimization, and before the GIMPLE optimizers
204 were added. Probably, multiple passes is even less efficient now than
205 at the time when the study was conducted.
207 PRE is quite expensive in complicated functions because the DFA can take
208 a while to converge. Hence we only perform one pass.
210 **********************
212 The steps for PRE are:
214 1) Build the hash table of expressions we wish to GCSE (expr_hash_table).
216 2) Perform the data flow analysis for PRE.
218 3) Delete the redundant instructions
220 4) Insert the required copies [if any] that make the partially
221 redundant instructions fully redundant.
223 5) For other reaching expressions, insert an instruction to copy the value
224 to a newly created pseudo that will reach the redundant instruction.
226 The deletion is done first so that when we do insertions we
227 know which pseudo reg to use.
229 Various papers have argued that PRE DFA is expensive (O(n^2)) and others
230 argue it is not. The number of iterations for the algorithm to converge
231 is typically 2-4 so I don't view it as that expensive (relatively speaking).
233 PRE GCSE depends heavily on the second CPROP pass to clean up the copies
234 we create. To make an expression reach the place where it's redundant,
235 the result of the expression is copied to a new register, and the redundant
236 expression is deleted by replacing it with this new register. Classic GCSE
237 doesn't have this problem as much as it computes the reaching defs of
238 each register in each block and thus can try to use an existing
241 /* GCSE global vars. */
243 struct target_gcse default_target_gcse
;
244 #if SWITCHABLE_TARGET
245 struct target_gcse
*this_target_gcse
= &default_target_gcse
;
248 /* Set to non-zero if CSE should run after all GCSE optimizations are done. */
249 int flag_rerun_cse_after_global_opts
;
251 /* An obstack for our working variables. */
252 static struct obstack gcse_obstack
;
254 /* Hash table of expressions. */
258 /* The expression. */
260 /* Index in the available expression bitmaps. */
262 /* Next entry with the same hash. */
263 struct gcse_expr
*next_same_hash
;
264 /* List of anticipatable occurrences in basic blocks in the function.
265 An "anticipatable occurrence" is one that is the first occurrence in the
266 basic block, the operands are not modified in the basic block prior
267 to the occurrence and the output is not used between the start of
268 the block and the occurrence. */
269 struct gcse_occr
*antic_occr
;
270 /* List of available occurrence in basic blocks in the function.
271 An "available occurrence" is one that is the last occurrence in the
272 basic block and the operands are not modified by following statements in
273 the basic block [including this insn]. */
274 struct gcse_occr
*avail_occr
;
275 /* Non-null if the computation is PRE redundant.
276 The value is the newly created pseudo-reg to record a copy of the
277 expression in all the places that reach the redundant copy. */
279 /* Maximum distance in instructions this expression can travel.
280 We avoid moving simple expressions for more than a few instructions
281 to keep register pressure under control.
282 A value of "0" removes restrictions on how far the expression can
284 HOST_WIDE_INT max_distance
;
287 /* Occurrence of an expression.
288 There is one per basic block. If a pattern appears more than once the
289 last appearance is used [or first for anticipatable expressions]. */
293 /* Next occurrence of this expression. */
294 struct gcse_occr
*next
;
295 /* The insn that computes the expression. */
297 /* Nonzero if this [anticipatable] occurrence has been deleted. */
299 /* Nonzero if this [available] occurrence has been copied to
301 /* ??? This is mutually exclusive with deleted_p, so they could share
306 typedef struct gcse_occr
*occr_t
;
308 /* Expression hash tables.
309 Each hash table is an array of buckets.
310 ??? It is known that if it were an array of entries, structure elements
311 `next_same_hash' and `bitmap_index' wouldn't be necessary. However, it is
312 not clear whether in the final analysis a sufficient amount of memory would
313 be saved as the size of the available expression bitmaps would be larger
314 [one could build a mapping table without holes afterwards though].
315 Someday I'll perform the computation and figure it out. */
317 struct gcse_hash_table_d
320 This is an array of `expr_hash_table_size' elements. */
321 struct gcse_expr
**table
;
323 /* Size of the hash table, in elements. */
326 /* Number of hash table elements. */
327 unsigned int n_elems
;
330 /* Expression hash table. */
331 static struct gcse_hash_table_d expr_hash_table
;
333 /* This is a list of expressions which are MEMs and will be used by load
335 Load motion tracks MEMs which aren't killed by anything except itself,
336 i.e. loads and stores to a single location.
337 We can then allow movement of these MEM refs with a little special
338 allowance. (all stores copy the same value to the reaching reg used
339 for the loads). This means all values used to store into memory must have
340 no side effects so we can re-issue the setter value. */
344 struct gcse_expr
* expr
; /* Gcse expression reference for LM. */
345 rtx pattern
; /* Pattern of this mem. */
346 rtx pattern_regs
; /* List of registers mentioned by the mem. */
347 vec
<rtx_insn
*> stores
; /* INSN list of stores seen. */
348 struct ls_expr
* next
; /* Next in the list. */
349 int invalid
; /* Invalid for some reason. */
350 int index
; /* If it maps to a bitmap index. */
351 unsigned int hash_index
; /* Index when in a hash table. */
352 rtx reaching_reg
; /* Register to use when re-writing. */
355 /* Head of the list of load/store memory refs. */
356 static struct ls_expr
* pre_ldst_mems
= NULL
;
358 struct pre_ldst_expr_hasher
: nofree_ptr_hash
<ls_expr
>
360 typedef value_type compare_type
;
361 static inline hashval_t
hash (const ls_expr
*);
362 static inline bool equal (const ls_expr
*, const ls_expr
*);
365 /* Hashtable helpers. */
367 pre_ldst_expr_hasher::hash (const ls_expr
*x
)
369 int do_not_record_p
= 0;
371 hash_rtx (x
->pattern
, GET_MODE (x
->pattern
), &do_not_record_p
, NULL
, false);
374 static int expr_equiv_p (const_rtx
, const_rtx
);
377 pre_ldst_expr_hasher::equal (const ls_expr
*ptr1
,
380 return expr_equiv_p (ptr1
->pattern
, ptr2
->pattern
);
383 /* Hashtable for the load/store memory refs. */
384 static hash_table
<pre_ldst_expr_hasher
> *pre_ldst_table
;
386 /* Bitmap containing one bit for each register in the program.
387 Used when performing GCSE to track which registers have been set since
388 the start of the basic block. */
389 static regset reg_set_bitmap
;
391 /* Array, indexed by basic block number for a list of insns which modify
392 memory within that block. */
393 static vec
<rtx_insn
*> *modify_mem_list
;
394 static bitmap modify_mem_list_set
;
396 /* This array parallels modify_mem_list, except that it stores MEMs
397 being set and their canonicalized memory addresses. */
398 static vec
<modify_pair
> *canon_modify_mem_list
;
400 /* Bitmap indexed by block numbers to record which blocks contain
402 static bitmap blocks_with_calls
;
404 /* Various variables for statistics gathering. */
406 /* Memory used in a pass.
407 This isn't intended to be absolutely precise. Its intent is only
408 to keep an eye on memory usage. */
409 static int bytes_used
;
411 /* GCSE substitutions made. */
412 static int gcse_subst_count
;
413 /* Number of copy instructions created. */
414 static int gcse_create_count
;
416 /* Doing code hoisting. */
417 static bool doing_code_hoisting_p
= false;
419 /* For available exprs */
420 static sbitmap
*ae_kill
;
422 /* Data stored for each basic block. */
425 /* Maximal register pressure inside basic block for given register class
426 (defined only for the pressure classes). */
427 int max_reg_pressure
[N_REG_CLASSES
];
428 /* Recorded register pressure of basic block before trying to hoist
429 an expression. Will be used to restore the register pressure
430 if the expression should not be hoisted. */
432 /* Recorded register live_in info of basic block during code hoisting
433 process. BACKUP is used to record live_in info before trying to
434 hoist an expression, and will be used to restore LIVE_IN if the
435 expression should not be hoisted. */
436 bitmap live_in
, backup
;
439 #define BB_DATA(bb) ((struct bb_data *) (bb)->aux)
441 static basic_block curr_bb
;
443 /* Current register pressure for each pressure class. */
444 static int curr_reg_pressure
[N_REG_CLASSES
];
447 static void compute_can_copy (void);
448 static void *gmalloc (size_t) ATTRIBUTE_MALLOC
;
449 static void *gcalloc (size_t, size_t) ATTRIBUTE_MALLOC
;
450 static void *gcse_alloc (unsigned long);
451 static void alloc_gcse_mem (void);
452 static void free_gcse_mem (void);
453 static void hash_scan_insn (rtx_insn
*, struct gcse_hash_table_d
*);
454 static void hash_scan_set (rtx
, rtx_insn
*, struct gcse_hash_table_d
*);
455 static void hash_scan_clobber (rtx
, rtx_insn
*, struct gcse_hash_table_d
*);
456 static void hash_scan_call (rtx
, rtx_insn
*, struct gcse_hash_table_d
*);
457 static int oprs_unchanged_p (const_rtx
, const rtx_insn
*, int);
458 static int oprs_anticipatable_p (const_rtx
, const rtx_insn
*);
459 static int oprs_available_p (const_rtx
, const rtx_insn
*);
460 static void insert_expr_in_table (rtx
, machine_mode
, rtx_insn
*, int, int,
461 HOST_WIDE_INT
, struct gcse_hash_table_d
*);
462 static unsigned int hash_expr (const_rtx
, machine_mode
, int *, int);
463 static void record_last_reg_set_info (rtx_insn
*, int);
464 static void record_last_mem_set_info (rtx_insn
*);
465 static void record_last_set_info (rtx
, const_rtx
, void *);
466 static void compute_hash_table (struct gcse_hash_table_d
*);
467 static void alloc_hash_table (struct gcse_hash_table_d
*);
468 static void free_hash_table (struct gcse_hash_table_d
*);
469 static void compute_hash_table_work (struct gcse_hash_table_d
*);
470 static void dump_hash_table (FILE *, const char *, struct gcse_hash_table_d
*);
471 static void compute_local_properties (sbitmap
*, sbitmap
*, sbitmap
*,
472 struct gcse_hash_table_d
*);
473 static void mems_conflict_for_gcse_p (rtx
, const_rtx
, void *);
474 static int load_killed_in_block_p (const_basic_block
, int, const_rtx
, int);
475 static void alloc_pre_mem (int, int);
476 static void free_pre_mem (void);
477 static struct edge_list
*compute_pre_data (void);
478 static int pre_expr_reaches_here_p (basic_block
, struct gcse_expr
*,
480 static void insert_insn_end_basic_block (struct gcse_expr
*, basic_block
);
481 static void pre_insert_copy_insn (struct gcse_expr
*, rtx_insn
*);
482 static void pre_insert_copies (void);
483 static int pre_delete (void);
484 static int pre_gcse (struct edge_list
*);
485 static int one_pre_gcse_pass (void);
486 static void add_label_notes (rtx
, rtx_insn
*);
487 static void alloc_code_hoist_mem (int, int);
488 static void free_code_hoist_mem (void);
489 static void compute_code_hoist_vbeinout (void);
490 static void compute_code_hoist_data (void);
491 static int should_hoist_expr_to_dom (basic_block
, struct gcse_expr
*,
493 sbitmap
, HOST_WIDE_INT
, int *,
495 int *, bitmap
, rtx_insn
*);
496 static int hoist_code (void);
497 static enum reg_class
get_regno_pressure_class (int regno
, int *nregs
);
498 static enum reg_class
get_pressure_class_and_nregs (rtx_insn
*insn
, int *nregs
);
499 static int one_code_hoisting_pass (void);
500 static rtx_insn
*process_insert_insn (struct gcse_expr
*);
501 static int pre_edge_insert (struct edge_list
*, struct gcse_expr
**);
502 static int pre_expr_reaches_here_p_work (basic_block
, struct gcse_expr
*,
503 basic_block
, char *);
504 static struct ls_expr
* ldst_entry (rtx
);
505 static void free_ldst_entry (struct ls_expr
*);
506 static void free_ld_motion_mems (void);
507 static void print_ldst_list (FILE *);
508 static struct ls_expr
* find_rtx_in_ldst (rtx
);
509 static int simple_mem (const_rtx
);
510 static void invalidate_any_buried_refs (rtx
);
511 static void compute_ld_motion_mems (void);
512 static void trim_ld_motion_mems (void);
513 static void update_ld_motion_stores (struct gcse_expr
*);
514 static void clear_modify_mem_tables (void);
515 static void free_modify_mem_tables (void);
517 #define GNEW(T) ((T *) gmalloc (sizeof (T)))
518 #define GCNEW(T) ((T *) gcalloc (1, sizeof (T)))
520 #define GNEWVEC(T, N) ((T *) gmalloc (sizeof (T) * (N)))
521 #define GCNEWVEC(T, N) ((T *) gcalloc ((N), sizeof (T)))
523 #define GNEWVAR(T, S) ((T *) gmalloc ((S)))
524 #define GCNEWVAR(T, S) ((T *) gcalloc (1, (S)))
526 #define GOBNEW(T) ((T *) gcse_alloc (sizeof (T)))
527 #define GOBNEWVAR(T, S) ((T *) gcse_alloc ((S)))
529 /* Misc. utilities. */
532 (this_target_gcse->x_can_copy)
533 #define can_copy_init_p \
534 (this_target_gcse->x_can_copy_init_p)
536 /* Compute which modes support reg/reg copy operations. */
539 compute_can_copy (void)
542 #ifndef AVOID_CCMODE_COPIES
546 memset (can_copy
, 0, NUM_MACHINE_MODES
);
549 for (i
= 0; i
< NUM_MACHINE_MODES
; i
++)
550 if (GET_MODE_CLASS (i
) == MODE_CC
)
552 #ifdef AVOID_CCMODE_COPIES
555 reg
= gen_rtx_REG ((machine_mode
) i
, LAST_VIRTUAL_REGISTER
+ 1);
556 insn
= emit_insn (gen_rtx_SET (reg
, reg
));
557 if (recog (PATTERN (insn
), insn
, NULL
) >= 0)
567 /* Returns whether the mode supports reg/reg copy operations. */
570 can_copy_p (machine_mode mode
)
572 if (! can_copy_init_p
)
575 can_copy_init_p
= true;
578 return can_copy
[mode
] != 0;
581 /* Cover function to xmalloc to record bytes allocated. */
584 gmalloc (size_t size
)
587 return xmalloc (size
);
590 /* Cover function to xcalloc to record bytes allocated. */
593 gcalloc (size_t nelem
, size_t elsize
)
595 bytes_used
+= nelem
* elsize
;
596 return xcalloc (nelem
, elsize
);
599 /* Cover function to obstack_alloc. */
602 gcse_alloc (unsigned long size
)
605 return obstack_alloc (&gcse_obstack
, size
);
608 /* Allocate memory for the reg/memory set tracking tables.
609 This is called at the start of each pass. */
612 alloc_gcse_mem (void)
614 /* Allocate vars to track sets of regs. */
615 reg_set_bitmap
= ALLOC_REG_SET (NULL
);
617 /* Allocate array to keep a list of insns which modify memory in each
618 basic block. The two typedefs are needed to work around the
619 pre-processor limitation with template types in macro arguments. */
620 typedef vec
<rtx_insn
*> vec_rtx_heap
;
621 typedef vec
<modify_pair
> vec_modify_pair_heap
;
622 modify_mem_list
= GCNEWVEC (vec_rtx_heap
, last_basic_block_for_fn (cfun
));
623 canon_modify_mem_list
= GCNEWVEC (vec_modify_pair_heap
,
624 last_basic_block_for_fn (cfun
));
625 modify_mem_list_set
= BITMAP_ALLOC (NULL
);
626 blocks_with_calls
= BITMAP_ALLOC (NULL
);
629 /* Free memory allocated by alloc_gcse_mem. */
634 FREE_REG_SET (reg_set_bitmap
);
636 free_modify_mem_tables ();
637 BITMAP_FREE (modify_mem_list_set
);
638 BITMAP_FREE (blocks_with_calls
);
641 /* Compute the local properties of each recorded expression.
643 Local properties are those that are defined by the block, irrespective of
646 An expression is transparent in a block if its operands are not modified
649 An expression is computed (locally available) in a block if it is computed
650 at least once and expression would contain the same value if the
651 computation was moved to the end of the block.
653 An expression is locally anticipatable in a block if it is computed at
654 least once and expression would contain the same value if the computation
655 was moved to the beginning of the block.
657 We call this routine for pre and code hoisting. They all compute
658 basically the same information and thus can easily share this code.
660 TRANSP, COMP, and ANTLOC are destination sbitmaps for recording local
661 properties. If NULL, then it is not necessary to compute or record that
664 TABLE controls which hash table to look at. */
667 compute_local_properties (sbitmap
*transp
, sbitmap
*comp
, sbitmap
*antloc
,
668 struct gcse_hash_table_d
*table
)
672 /* Initialize any bitmaps that were passed in. */
675 bitmap_vector_ones (transp
, last_basic_block_for_fn (cfun
));
679 bitmap_vector_clear (comp
, last_basic_block_for_fn (cfun
));
681 bitmap_vector_clear (antloc
, last_basic_block_for_fn (cfun
));
683 for (i
= 0; i
< table
->size
; i
++)
685 struct gcse_expr
*expr
;
687 for (expr
= table
->table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
689 int indx
= expr
->bitmap_index
;
690 struct gcse_occr
*occr
;
692 /* The expression is transparent in this block if it is not killed.
693 We start by assuming all are transparent [none are killed], and
694 then reset the bits for those that are. */
696 compute_transp (expr
->expr
, indx
, transp
,
699 canon_modify_mem_list
);
701 /* The occurrences recorded in antic_occr are exactly those that
702 we want to set to nonzero in ANTLOC. */
704 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
706 bitmap_set_bit (antloc
[BLOCK_FOR_INSN (occr
->insn
)->index
], indx
);
708 /* While we're scanning the table, this is a good place to
713 /* The occurrences recorded in avail_occr are exactly those that
714 we want to set to nonzero in COMP. */
716 for (occr
= expr
->avail_occr
; occr
!= NULL
; occr
= occr
->next
)
718 bitmap_set_bit (comp
[BLOCK_FOR_INSN (occr
->insn
)->index
], indx
);
720 /* While we're scanning the table, this is a good place to
725 /* While we're scanning the table, this is a good place to
727 expr
->reaching_reg
= 0;
732 /* Hash table support. */
734 struct reg_avail_info
741 static struct reg_avail_info
*reg_avail_info
;
742 static basic_block current_bb
;
744 /* See whether X, the source of a set, is something we want to consider for
748 want_to_gcse_p (rtx x
, machine_mode mode
, HOST_WIDE_INT
*max_distance_ptr
)
751 /* On register stack architectures, don't GCSE constants from the
752 constant pool, as the benefits are often swamped by the overhead
753 of shuffling the register stack between basic blocks. */
754 if (IS_STACK_MODE (GET_MODE (x
)))
755 x
= avoid_constant_pool_reference (x
);
758 /* GCSE'ing constants:
760 We do not specifically distinguish between constant and non-constant
761 expressions in PRE and Hoist. We use set_src_cost below to limit
762 the maximum distance simple expressions can travel.
764 Nevertheless, constants are much easier to GCSE, and, hence,
765 it is easy to overdo the optimizations. Usually, excessive PRE and
766 Hoisting of constant leads to increased register pressure.
768 RA can deal with this by rematerialing some of the constants.
769 Therefore, it is important that the back-end generates sets of constants
770 in a way that allows reload rematerialize them under high register
771 pressure, i.e., a pseudo register with REG_EQUAL to constant
772 is set only once. Failing to do so will result in IRA/reload
773 spilling such constants under high register pressure instead of
774 rematerializing them. */
776 switch (GET_CODE (x
))
784 if (!doing_code_hoisting_p
)
785 /* Do not PRE constants. */
791 if (doing_code_hoisting_p
)
792 /* PRE doesn't implement max_distance restriction. */
795 HOST_WIDE_INT max_distance
;
797 gcc_assert (!optimize_function_for_speed_p (cfun
)
798 && optimize_function_for_size_p (cfun
));
799 cost
= set_src_cost (x
, mode
, 0);
801 if (cost
< COSTS_N_INSNS (param_gcse_unrestricted_cost
))
804 = ((HOST_WIDE_INT
)param_gcse_cost_distance_ratio
* cost
) / 10;
805 if (max_distance
== 0)
808 gcc_assert (max_distance
> 0);
813 if (max_distance_ptr
)
814 *max_distance_ptr
= max_distance
;
817 return can_assign_to_reg_without_clobbers_p (x
, mode
);
821 /* Used internally by can_assign_to_reg_without_clobbers_p. */
823 static GTY(()) rtx_insn
*test_insn
;
825 /* Return true if we can assign X to a pseudo register of mode MODE
826 such that the resulting insn does not result in clobbering a hard
827 register as a side-effect.
829 Additionally, if the target requires it, check that the resulting insn
830 can be copied. If it cannot, this means that X is special and probably
831 has hidden side-effects we don't want to mess with.
833 This function is typically used by code motion passes, to verify
834 that it is safe to insert an insn without worrying about clobbering
835 maybe live hard regs. */
838 can_assign_to_reg_without_clobbers_p (rtx x
, machine_mode mode
)
840 int num_clobbers
= 0;
842 bool can_assign
= false;
844 /* If this is a valid operand, we are OK. If it's VOIDmode, we aren't. */
845 if (general_operand (x
, mode
))
847 else if (GET_MODE (x
) == VOIDmode
)
850 /* Otherwise, check if we can make a valid insn from it. First initialize
851 our test insn if we haven't already. */
855 = make_insn_raw (gen_rtx_SET (gen_rtx_REG (word_mode
,
856 FIRST_PSEUDO_REGISTER
* 2),
858 SET_NEXT_INSN (test_insn
) = SET_PREV_INSN (test_insn
) = 0;
859 INSN_LOCATION (test_insn
) = UNKNOWN_LOCATION
;
862 /* Now make an insn like the one we would make when GCSE'ing and see if
864 PUT_MODE (SET_DEST (PATTERN (test_insn
)), mode
);
865 SET_SRC (PATTERN (test_insn
)) = x
;
867 icode
= recog (PATTERN (test_insn
), test_insn
, &num_clobbers
);
869 /* If the test insn is valid and doesn't need clobbers, and the target also
870 has no objections, we're good. */
872 && (num_clobbers
== 0 || !added_clobbers_hard_reg_p (icode
))
873 && ! (targetm
.cannot_copy_insn_p
874 && targetm
.cannot_copy_insn_p (test_insn
)))
877 /* Make sure test_insn doesn't have any pointers into GC space. */
878 SET_SRC (PATTERN (test_insn
)) = NULL_RTX
;
883 /* Return nonzero if the operands of expression X are unchanged from the
884 start of INSN's basic block up to but not including INSN (if AVAIL_P == 0),
885 or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */
888 oprs_unchanged_p (const_rtx x
, const rtx_insn
*insn
, int avail_p
)
902 struct reg_avail_info
*info
= ®_avail_info
[REGNO (x
)];
904 if (info
->last_bb
!= current_bb
)
907 return info
->last_set
< DF_INSN_LUID (insn
);
909 return info
->first_set
>= DF_INSN_LUID (insn
);
914 || load_killed_in_block_p (current_bb
, DF_INSN_LUID (insn
),
918 return oprs_unchanged_p (XEXP (x
, 0), insn
, avail_p
);
941 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
945 /* If we are about to do the last recursive call needed at this
946 level, change it into iteration. This function is called enough
949 return oprs_unchanged_p (XEXP (x
, i
), insn
, avail_p
);
951 else if (! oprs_unchanged_p (XEXP (x
, i
), insn
, avail_p
))
954 else if (fmt
[i
] == 'E')
955 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
956 if (! oprs_unchanged_p (XVECEXP (x
, i
, j
), insn
, avail_p
))
963 /* Info passed from load_killed_in_block_p to mems_conflict_for_gcse_p. */
965 struct mem_conflict_info
967 /* A memory reference for a load instruction, mems_conflict_for_gcse_p will
968 see if a memory store conflicts with this memory load. */
971 /* True if mems_conflict_for_gcse_p finds a conflict between two memory
976 /* DEST is the output of an instruction. If it is a memory reference and
977 possibly conflicts with the load found in DATA, then communicate this
978 information back through DATA. */
981 mems_conflict_for_gcse_p (rtx dest
, const_rtx setter ATTRIBUTE_UNUSED
,
984 struct mem_conflict_info
*mci
= (struct mem_conflict_info
*) data
;
986 while (GET_CODE (dest
) == SUBREG
987 || GET_CODE (dest
) == ZERO_EXTRACT
988 || GET_CODE (dest
) == STRICT_LOW_PART
)
989 dest
= XEXP (dest
, 0);
991 /* If DEST is not a MEM, then it will not conflict with the load. Note
992 that function calls are assumed to clobber memory, but are handled
997 /* If we are setting a MEM in our list of specially recognized MEMs,
998 don't mark as killed this time. */
999 if (pre_ldst_mems
!= NULL
&& expr_equiv_p (dest
, mci
->mem
))
1001 if (!find_rtx_in_ldst (dest
))
1002 mci
->conflict
= true;
1006 if (true_dependence (dest
, GET_MODE (dest
), mci
->mem
))
1007 mci
->conflict
= true;
1010 /* Return nonzero if the expression in X (a memory reference) is killed
1011 in block BB before or after the insn with the LUID in UID_LIMIT.
1012 AVAIL_P is nonzero for kills after UID_LIMIT, and zero for kills
1015 To check the entire block, set UID_LIMIT to max_uid + 1 and
1019 load_killed_in_block_p (const_basic_block bb
, int uid_limit
, const_rtx x
,
1022 vec
<rtx_insn
*> list
= modify_mem_list
[bb
->index
];
1026 /* If this is a readonly then we aren't going to be changing it. */
1027 if (MEM_READONLY_P (x
))
1030 FOR_EACH_VEC_ELT_REVERSE (list
, ix
, setter
)
1032 struct mem_conflict_info mci
;
1034 /* Ignore entries in the list that do not apply. */
1036 && DF_INSN_LUID (setter
) < uid_limit
)
1038 && DF_INSN_LUID (setter
) > uid_limit
))
1041 /* If SETTER is a call everything is clobbered. Note that calls
1042 to pure functions are never put on the list, so we need not
1043 worry about them. */
1044 if (CALL_P (setter
))
1047 /* SETTER must be an INSN of some kind that sets memory. Call
1048 note_stores to examine each hunk of memory that is modified. */
1050 mci
.conflict
= false;
1051 note_stores (setter
, mems_conflict_for_gcse_p
, &mci
);
1058 /* Return nonzero if the operands of expression X are unchanged from
1059 the start of INSN's basic block up to but not including INSN. */
1062 oprs_anticipatable_p (const_rtx x
, const rtx_insn
*insn
)
1064 return oprs_unchanged_p (x
, insn
, 0);
1067 /* Return nonzero if the operands of expression X are unchanged from
1068 INSN to the end of INSN's basic block. */
1071 oprs_available_p (const_rtx x
, const rtx_insn
*insn
)
1073 return oprs_unchanged_p (x
, insn
, 1);
1076 /* Hash expression X.
1078 MODE is only used if X is a CONST_INT. DO_NOT_RECORD_P is a boolean
1079 indicating if a volatile operand is found or if the expression contains
1080 something we don't want to insert in the table. HASH_TABLE_SIZE is
1081 the current size of the hash table to be probed. */
1084 hash_expr (const_rtx x
, machine_mode mode
, int *do_not_record_p
,
1085 int hash_table_size
)
1089 *do_not_record_p
= 0;
1091 hash
= hash_rtx (x
, mode
, do_not_record_p
, NULL
, /*have_reg_qty=*/false);
1092 return hash
% hash_table_size
;
1095 /* Return nonzero if exp1 is equivalent to exp2. */
1098 expr_equiv_p (const_rtx x
, const_rtx y
)
1100 return exp_equiv_p (x
, y
, 0, true);
1103 /* Insert expression X in INSN in the hash TABLE.
1104 If it is already present, record it as the last occurrence in INSN's
1107 MODE is the mode of the value X is being stored into.
1108 It is only used if X is a CONST_INT.
1110 ANTIC_P is nonzero if X is an anticipatable expression.
1111 AVAIL_P is nonzero if X is an available expression.
1113 MAX_DISTANCE is the maximum distance in instructions this expression can
1117 insert_expr_in_table (rtx x
, machine_mode mode
, rtx_insn
*insn
,
1119 int avail_p
, HOST_WIDE_INT max_distance
,
1120 struct gcse_hash_table_d
*table
)
1122 int found
, do_not_record_p
;
1124 struct gcse_expr
*cur_expr
, *last_expr
= NULL
;
1125 struct gcse_occr
*antic_occr
, *avail_occr
;
1127 hash
= hash_expr (x
, mode
, &do_not_record_p
, table
->size
);
1129 /* Do not insert expression in table if it contains volatile operands,
1130 or if hash_expr determines the expression is something we don't want
1131 to or can't handle. */
1132 if (do_not_record_p
)
1135 cur_expr
= table
->table
[hash
];
1138 while (cur_expr
&& (found
= expr_equiv_p (cur_expr
->expr
, x
)) == 0)
1140 /* If the expression isn't found, save a pointer to the end of
1142 last_expr
= cur_expr
;
1143 cur_expr
= cur_expr
->next_same_hash
;
1148 cur_expr
= GOBNEW (struct gcse_expr
);
1149 bytes_used
+= sizeof (struct gcse_expr
);
1150 if (table
->table
[hash
] == NULL
)
1151 /* This is the first pattern that hashed to this index. */
1152 table
->table
[hash
] = cur_expr
;
1154 /* Add EXPR to end of this hash chain. */
1155 last_expr
->next_same_hash
= cur_expr
;
1157 /* Set the fields of the expr element. */
1159 cur_expr
->bitmap_index
= table
->n_elems
++;
1160 cur_expr
->next_same_hash
= NULL
;
1161 cur_expr
->antic_occr
= NULL
;
1162 cur_expr
->avail_occr
= NULL
;
1163 gcc_assert (max_distance
>= 0);
1164 cur_expr
->max_distance
= max_distance
;
1167 gcc_assert (cur_expr
->max_distance
== max_distance
);
1169 /* Now record the occurrence(s). */
1172 antic_occr
= cur_expr
->antic_occr
;
1175 && BLOCK_FOR_INSN (antic_occr
->insn
) != BLOCK_FOR_INSN (insn
))
1179 /* Found another instance of the expression in the same basic block.
1180 Prefer the currently recorded one. We want the first one in the
1181 block and the block is scanned from start to end. */
1182 ; /* nothing to do */
1185 /* First occurrence of this expression in this basic block. */
1186 antic_occr
= GOBNEW (struct gcse_occr
);
1187 bytes_used
+= sizeof (struct gcse_occr
);
1188 antic_occr
->insn
= insn
;
1189 antic_occr
->next
= cur_expr
->antic_occr
;
1190 antic_occr
->deleted_p
= 0;
1191 cur_expr
->antic_occr
= antic_occr
;
1197 avail_occr
= cur_expr
->avail_occr
;
1200 && BLOCK_FOR_INSN (avail_occr
->insn
) == BLOCK_FOR_INSN (insn
))
1202 /* Found another instance of the expression in the same basic block.
1203 Prefer this occurrence to the currently recorded one. We want
1204 the last one in the block and the block is scanned from start
1206 avail_occr
->insn
= insn
;
1210 /* First occurrence of this expression in this basic block. */
1211 avail_occr
= GOBNEW (struct gcse_occr
);
1212 bytes_used
+= sizeof (struct gcse_occr
);
1213 avail_occr
->insn
= insn
;
1214 avail_occr
->next
= cur_expr
->avail_occr
;
1215 avail_occr
->deleted_p
= 0;
1216 cur_expr
->avail_occr
= avail_occr
;
1221 /* Scan SET present in INSN and add an entry to the hash TABLE. */
1224 hash_scan_set (rtx set
, rtx_insn
*insn
, struct gcse_hash_table_d
*table
)
1226 rtx src
= SET_SRC (set
);
1227 rtx dest
= SET_DEST (set
);
1230 if (GET_CODE (src
) == CALL
)
1231 hash_scan_call (src
, insn
, table
);
1233 else if (REG_P (dest
))
1235 unsigned int regno
= REGNO (dest
);
1236 HOST_WIDE_INT max_distance
= 0;
1238 /* See if a REG_EQUAL note shows this equivalent to a simpler expression.
1240 This allows us to do a single GCSE pass and still eliminate
1241 redundant constants, addresses or other expressions that are
1242 constructed with multiple instructions.
1244 However, keep the original SRC if INSN is a simple reg-reg move.
1245 In this case, there will almost always be a REG_EQUAL note on the
1246 insn that sets SRC. By recording the REG_EQUAL value here as SRC
1247 for INSN, we miss copy propagation opportunities and we perform the
1248 same PRE GCSE operation repeatedly on the same REG_EQUAL value if we
1249 do more than one PRE GCSE pass.
1251 Note that this does not impede profitable constant propagations. We
1252 "look through" reg-reg sets in lookup_avail_set. */
1253 note
= find_reg_equal_equiv_note (insn
);
1255 && REG_NOTE_KIND (note
) == REG_EQUAL
1257 && want_to_gcse_p (XEXP (note
, 0), GET_MODE (dest
), NULL
))
1258 src
= XEXP (note
, 0), set
= gen_rtx_SET (dest
, src
);
1260 /* Only record sets of pseudo-regs in the hash table. */
1261 if (regno
>= FIRST_PSEUDO_REGISTER
1262 /* Don't GCSE something if we can't do a reg/reg copy. */
1263 && can_copy_p (GET_MODE (dest
))
1264 /* GCSE commonly inserts instruction after the insn. We can't
1265 do that easily for EH edges so disable GCSE on these for now. */
1266 /* ??? We can now easily create new EH landing pads at the
1267 gimple level, for splitting edges; there's no reason we
1268 can't do the same thing at the rtl level. */
1269 && !can_throw_internal (insn
)
1270 /* Is SET_SRC something we want to gcse? */
1271 && want_to_gcse_p (src
, GET_MODE (dest
), &max_distance
)
1272 /* Don't CSE a nop. */
1273 && ! set_noop_p (set
)
1274 /* Don't GCSE if it has attached REG_EQUIV note.
1275 At this point this only function parameters should have
1276 REG_EQUIV notes and if the argument slot is used somewhere
1277 explicitly, it means address of parameter has been taken,
1278 so we should not extend the lifetime of the pseudo. */
1279 && (note
== NULL_RTX
|| ! MEM_P (XEXP (note
, 0))))
1281 /* An expression is not anticipatable if its operands are
1282 modified before this insn or if this is not the only SET in
1283 this insn. The latter condition does not have to mean that
1284 SRC itself is not anticipatable, but we just will not be
1285 able to handle code motion of insns with multiple sets. */
1286 int antic_p
= oprs_anticipatable_p (src
, insn
)
1287 && !multiple_sets (insn
);
1288 /* An expression is not available if its operands are
1289 subsequently modified, including this insn. It's also not
1290 available if this is a branch, because we can't insert
1291 a set after the branch. */
1292 int avail_p
= (oprs_available_p (src
, insn
)
1293 && ! JUMP_P (insn
));
1295 insert_expr_in_table (src
, GET_MODE (dest
), insn
, antic_p
, avail_p
,
1296 max_distance
, table
);
1299 /* In case of store we want to consider the memory value as available in
1300 the REG stored in that memory. This makes it possible to remove
1301 redundant loads from due to stores to the same location. */
1302 else if (flag_gcse_las
&& REG_P (src
) && MEM_P (dest
))
1304 unsigned int regno
= REGNO (src
);
1305 HOST_WIDE_INT max_distance
= 0;
1307 /* Only record sets of pseudo-regs in the hash table. */
1308 if (regno
>= FIRST_PSEUDO_REGISTER
1309 /* Don't GCSE something if we can't do a reg/reg copy. */
1310 && can_copy_p (GET_MODE (src
))
1311 /* GCSE commonly inserts instruction after the insn. We can't
1312 do that easily for EH edges so disable GCSE on these for now. */
1313 && !can_throw_internal (insn
)
1314 /* Is SET_DEST something we want to gcse? */
1315 && want_to_gcse_p (dest
, GET_MODE (dest
), &max_distance
)
1316 /* Don't CSE a nop. */
1317 && ! set_noop_p (set
)
1318 /* Don't GCSE if it has attached REG_EQUIV note.
1319 At this point this only function parameters should have
1320 REG_EQUIV notes and if the argument slot is used somewhere
1321 explicitly, it means address of parameter has been taken,
1322 so we should not extend the lifetime of the pseudo. */
1323 && ((note
= find_reg_note (insn
, REG_EQUIV
, NULL_RTX
)) == 0
1324 || ! MEM_P (XEXP (note
, 0))))
1326 /* Stores are never anticipatable. */
1328 /* An expression is not available if its operands are
1329 subsequently modified, including this insn. It's also not
1330 available if this is a branch, because we can't insert
1331 a set after the branch. */
1332 int avail_p
= oprs_available_p (dest
, insn
) && ! JUMP_P (insn
);
1334 /* Record the memory expression (DEST) in the hash table. */
1335 insert_expr_in_table (dest
, GET_MODE (dest
), insn
,
1336 antic_p
, avail_p
, max_distance
, table
);
1342 hash_scan_clobber (rtx x ATTRIBUTE_UNUSED
, rtx_insn
*insn ATTRIBUTE_UNUSED
,
1343 struct gcse_hash_table_d
*table ATTRIBUTE_UNUSED
)
1345 /* Currently nothing to do. */
1349 hash_scan_call (rtx x ATTRIBUTE_UNUSED
, rtx_insn
*insn ATTRIBUTE_UNUSED
,
1350 struct gcse_hash_table_d
*table ATTRIBUTE_UNUSED
)
1352 /* Currently nothing to do. */
1355 /* Process INSN and add hash table entries as appropriate. */
1358 hash_scan_insn (rtx_insn
*insn
, struct gcse_hash_table_d
*table
)
1360 rtx pat
= PATTERN (insn
);
1363 /* Pick out the sets of INSN and for other forms of instructions record
1364 what's been modified. */
1366 if (GET_CODE (pat
) == SET
)
1367 hash_scan_set (pat
, insn
, table
);
1369 else if (GET_CODE (pat
) == CLOBBER
)
1370 hash_scan_clobber (pat
, insn
, table
);
1372 else if (GET_CODE (pat
) == CALL
)
1373 hash_scan_call (pat
, insn
, table
);
1375 else if (GET_CODE (pat
) == PARALLEL
)
1376 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
1378 rtx x
= XVECEXP (pat
, 0, i
);
1380 if (GET_CODE (x
) == SET
)
1381 hash_scan_set (x
, insn
, table
);
1382 else if (GET_CODE (x
) == CLOBBER
)
1383 hash_scan_clobber (x
, insn
, table
);
1384 else if (GET_CODE (x
) == CALL
)
1385 hash_scan_call (x
, insn
, table
);
1389 /* Dump the hash table TABLE to file FILE under the name NAME. */
1392 dump_hash_table (FILE *file
, const char *name
, struct gcse_hash_table_d
*table
)
1395 /* Flattened out table, so it's printed in proper order. */
1396 struct gcse_expr
**flat_table
;
1397 unsigned int *hash_val
;
1398 struct gcse_expr
*expr
;
1400 flat_table
= XCNEWVEC (struct gcse_expr
*, table
->n_elems
);
1401 hash_val
= XNEWVEC (unsigned int, table
->n_elems
);
1403 for (i
= 0; i
< (int) table
->size
; i
++)
1404 for (expr
= table
->table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
1406 flat_table
[expr
->bitmap_index
] = expr
;
1407 hash_val
[expr
->bitmap_index
] = i
;
1410 fprintf (file
, "%s hash table (%d buckets, %d entries)\n",
1411 name
, table
->size
, table
->n_elems
);
1413 for (i
= 0; i
< (int) table
->n_elems
; i
++)
1414 if (flat_table
[i
] != 0)
1416 expr
= flat_table
[i
];
1417 fprintf (file
, "Index %d (hash value %d; max distance "
1418 HOST_WIDE_INT_PRINT_DEC
")\n ",
1419 expr
->bitmap_index
, hash_val
[i
], expr
->max_distance
);
1420 print_rtl (file
, expr
->expr
);
1421 fprintf (file
, "\n");
1424 fprintf (file
, "\n");
1430 /* Record register first/last/block set information for REGNO in INSN.
1432 first_set records the first place in the block where the register
1433 is set and is used to compute "anticipatability".
1435 last_set records the last place in the block where the register
1436 is set and is used to compute "availability".
1438 last_bb records the block for which first_set and last_set are
1439 valid, as a quick test to invalidate them. */
1442 record_last_reg_set_info (rtx_insn
*insn
, int regno
)
1444 struct reg_avail_info
*info
= ®_avail_info
[regno
];
1445 int luid
= DF_INSN_LUID (insn
);
1447 info
->last_set
= luid
;
1448 if (info
->last_bb
!= current_bb
)
1450 info
->last_bb
= current_bb
;
1451 info
->first_set
= luid
;
1455 /* Record memory modification information for INSN. We do not actually care
1456 about the memory location(s) that are set, or even how they are set (consider
1457 a CALL_INSN). We merely need to record which insns modify memory. */
1460 record_last_mem_set_info (rtx_insn
*insn
)
1465 record_last_mem_set_info_common (insn
, modify_mem_list
,
1466 canon_modify_mem_list
,
1467 modify_mem_list_set
,
1471 /* Called from compute_hash_table via note_stores to handle one
1472 SET or CLOBBER in an insn. DATA is really the instruction in which
1473 the SET is taking place. */
1476 record_last_set_info (rtx dest
, const_rtx setter ATTRIBUTE_UNUSED
, void *data
)
1478 rtx_insn
*last_set_insn
= (rtx_insn
*) data
;
1480 if (GET_CODE (dest
) == SUBREG
)
1481 dest
= SUBREG_REG (dest
);
1484 record_last_reg_set_info (last_set_insn
, REGNO (dest
));
1485 else if (MEM_P (dest
)
1486 /* Ignore pushes, they clobber nothing. */
1487 && ! push_operand (dest
, GET_MODE (dest
)))
1488 record_last_mem_set_info (last_set_insn
);
1491 /* Top level function to create an expression hash table.
1493 Expression entries are placed in the hash table if
1494 - they are of the form (set (pseudo-reg) src),
1495 - src is something we want to perform GCSE on,
1496 - none of the operands are subsequently modified in the block
1498 Currently src must be a pseudo-reg or a const_int.
1500 TABLE is the table computed. */
1503 compute_hash_table_work (struct gcse_hash_table_d
*table
)
1507 /* re-Cache any INSN_LIST nodes we have allocated. */
1508 clear_modify_mem_tables ();
1509 /* Some working arrays used to track first and last set in each block. */
1510 reg_avail_info
= GNEWVEC (struct reg_avail_info
, max_reg_num ());
1512 for (i
= 0; i
< max_reg_num (); ++i
)
1513 reg_avail_info
[i
].last_bb
= NULL
;
1515 FOR_EACH_BB_FN (current_bb
, cfun
)
1520 /* First pass over the instructions records information used to
1521 determine when registers and memory are first and last set. */
1522 FOR_BB_INSNS (current_bb
, insn
)
1524 if (!NONDEBUG_INSN_P (insn
))
1529 hard_reg_set_iterator hrsi
;
1531 /* We don't track modes of hard registers, so we need
1532 to be conservative and assume that partial kills
1534 HARD_REG_SET callee_clobbers
1535 = insn_callee_abi (insn
).full_and_partial_reg_clobbers ();
1536 EXECUTE_IF_SET_IN_HARD_REG_SET (callee_clobbers
, 0, regno
, hrsi
)
1537 record_last_reg_set_info (insn
, regno
);
1539 if (! RTL_CONST_OR_PURE_CALL_P (insn
)
1540 || RTL_LOOPING_CONST_OR_PURE_CALL_P (insn
))
1541 record_last_mem_set_info (insn
);
1544 note_stores (insn
, record_last_set_info
, insn
);
1547 /* The next pass builds the hash table. */
1548 FOR_BB_INSNS (current_bb
, insn
)
1549 if (NONDEBUG_INSN_P (insn
))
1550 hash_scan_insn (insn
, table
);
1553 free (reg_avail_info
);
1554 reg_avail_info
= NULL
;
1557 /* Allocate space for the set/expr hash TABLE.
1558 It is used to determine the number of buckets to use. */
1561 alloc_hash_table (struct gcse_hash_table_d
*table
)
1565 n
= get_max_insn_count ();
1567 table
->size
= n
/ 4;
1568 if (table
->size
< 11)
1571 /* Attempt to maintain efficient use of hash table.
1572 Making it an odd number is simplest for now.
1573 ??? Later take some measurements. */
1575 n
= table
->size
* sizeof (struct gcse_expr
*);
1576 table
->table
= GNEWVAR (struct gcse_expr
*, n
);
1579 /* Free things allocated by alloc_hash_table. */
1582 free_hash_table (struct gcse_hash_table_d
*table
)
1584 free (table
->table
);
1587 /* Compute the expression hash table TABLE. */
1590 compute_hash_table (struct gcse_hash_table_d
*table
)
1592 /* Initialize count of number of entries in hash table. */
1594 memset (table
->table
, 0, table
->size
* sizeof (struct gcse_expr
*));
1596 compute_hash_table_work (table
);
1599 /* Expression tracking support. */
1601 /* Clear canon_modify_mem_list and modify_mem_list tables. */
1603 clear_modify_mem_tables (void)
1608 EXECUTE_IF_SET_IN_BITMAP (modify_mem_list_set
, 0, i
, bi
)
1610 modify_mem_list
[i
].release ();
1611 canon_modify_mem_list
[i
].release ();
1613 bitmap_clear (modify_mem_list_set
);
1614 bitmap_clear (blocks_with_calls
);
1617 /* Release memory used by modify_mem_list_set. */
1620 free_modify_mem_tables (void)
1622 clear_modify_mem_tables ();
1623 free (modify_mem_list
);
1624 free (canon_modify_mem_list
);
1625 modify_mem_list
= 0;
1626 canon_modify_mem_list
= 0;
1629 /* Compute PRE+LCM working variables. */
1631 /* Local properties of expressions. */
1633 /* Nonzero for expressions that are transparent in the block. */
1634 static sbitmap
*transp
;
1636 /* Nonzero for expressions that are computed (available) in the block. */
1637 static sbitmap
*comp
;
1639 /* Nonzero for expressions that are locally anticipatable in the block. */
1640 static sbitmap
*antloc
;
1642 /* Nonzero for expressions where this block is an optimal computation
1644 static sbitmap
*pre_optimal
;
1646 /* Nonzero for expressions which are redundant in a particular block. */
1647 static sbitmap
*pre_redundant
;
1649 /* Nonzero for expressions which should be inserted on a specific edge. */
1650 static sbitmap
*pre_insert_map
;
1652 /* Nonzero for expressions which should be deleted in a specific block. */
1653 static sbitmap
*pre_delete_map
;
1655 /* Allocate vars used for PRE analysis. */
1658 alloc_pre_mem (int n_blocks
, int n_exprs
)
1660 transp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
1661 comp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
1662 antloc
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
1665 pre_redundant
= NULL
;
1666 pre_insert_map
= NULL
;
1667 pre_delete_map
= NULL
;
1668 ae_kill
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
1670 /* pre_insert and pre_delete are allocated later. */
1673 /* Free vars used for PRE analysis. */
1678 sbitmap_vector_free (transp
);
1679 sbitmap_vector_free (comp
);
1681 /* ANTLOC and AE_KILL are freed just after pre_lcm finishes. */
1684 sbitmap_vector_free (pre_optimal
);
1686 sbitmap_vector_free (pre_redundant
);
1688 sbitmap_vector_free (pre_insert_map
);
1690 sbitmap_vector_free (pre_delete_map
);
1692 transp
= comp
= NULL
;
1693 pre_optimal
= pre_redundant
= pre_insert_map
= pre_delete_map
= NULL
;
1696 /* Remove certain expressions from anticipatable and transparent
1697 sets of basic blocks that have incoming abnormal edge.
1698 For PRE remove potentially trapping expressions to avoid placing
1699 them on abnormal edges. For hoisting remove memory references that
1700 can be clobbered by calls. */
1703 prune_expressions (bool pre_p
)
1705 struct gcse_expr
*expr
;
1709 auto_sbitmap
prune_exprs (expr_hash_table
.n_elems
);
1710 bitmap_clear (prune_exprs
);
1711 for (ui
= 0; ui
< expr_hash_table
.size
; ui
++)
1713 for (expr
= expr_hash_table
.table
[ui
]; expr
; expr
= expr
->next_same_hash
)
1715 /* Note potentially trapping expressions. */
1716 if (may_trap_p (expr
->expr
))
1718 bitmap_set_bit (prune_exprs
, expr
->bitmap_index
);
1722 if (!pre_p
&& contains_mem_rtx_p (expr
->expr
))
1723 /* Note memory references that can be clobbered by a call.
1724 We do not split abnormal edges in hoisting, so would
1725 a memory reference get hoisted along an abnormal edge,
1726 it would be placed /before/ the call. Therefore, only
1727 constant memory references can be hoisted along abnormal
1732 /* Common cases where we might find the MEM which may allow us
1733 to avoid pruning the expression. */
1734 while (GET_CODE (x
) == ZERO_EXTEND
|| GET_CODE (x
) == SIGN_EXTEND
)
1737 /* If we found the MEM, go ahead and look at it to see if it has
1738 properties that allow us to avoid pruning its expression out
1742 if (GET_CODE (XEXP (x
, 0)) == SYMBOL_REF
1743 && CONSTANT_POOL_ADDRESS_P (XEXP (x
, 0)))
1746 if (MEM_READONLY_P (x
)
1747 && !MEM_VOLATILE_P (x
)
1748 && MEM_NOTRAP_P (x
))
1749 /* Constant memory reference, e.g., a PIC address. */
1753 /* ??? Optimally, we would use interprocedural alias
1754 analysis to determine if this mem is actually killed
1757 bitmap_set_bit (prune_exprs
, expr
->bitmap_index
);
1762 FOR_EACH_BB_FN (bb
, cfun
)
1767 /* If the current block is the destination of an abnormal edge, we
1768 kill all trapping (for PRE) and memory (for hoist) expressions
1769 because we won't be able to properly place the instruction on
1770 the edge. So make them neither anticipatable nor transparent.
1771 This is fairly conservative.
1773 ??? For hoisting it may be necessary to check for set-and-jump
1774 instructions here, not just for abnormal edges. The general problem
1775 is that when an expression cannot not be placed right at the end of
1776 a basic block we should account for any side-effects of a subsequent
1777 jump instructions that could clobber the expression. It would
1778 be best to implement this check along the lines of
1779 should_hoist_expr_to_dom where the target block is already known
1780 and, hence, there's no need to conservatively prune expressions on
1781 "intermediate" set-and-jump instructions. */
1782 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1783 if ((e
->flags
& EDGE_ABNORMAL
)
1784 && (pre_p
|| CALL_P (BB_END (e
->src
))))
1786 bitmap_and_compl (antloc
[bb
->index
],
1787 antloc
[bb
->index
], prune_exprs
);
1788 bitmap_and_compl (transp
[bb
->index
],
1789 transp
[bb
->index
], prune_exprs
);
1795 /* It may be necessary to insert a large number of insns on edges to
1796 make the existing occurrences of expressions fully redundant. This
1797 routine examines the set of insertions and deletions and if the ratio
1798 of insertions to deletions is too high for a particular expression, then
1799 the expression is removed from the insertion/deletion sets.
1801 N_ELEMS is the number of elements in the hash table. */
1804 prune_insertions_deletions (int n_elems
)
1806 sbitmap_iterator sbi
;
1808 /* We always use I to iterate over blocks/edges and J to iterate over
1812 /* Counts for the number of times an expression needs to be inserted and
1813 number of times an expression can be removed as a result. */
1814 int *insertions
= GCNEWVEC (int, n_elems
);
1815 int *deletions
= GCNEWVEC (int, n_elems
);
1817 /* Set of expressions which require too many insertions relative to
1818 the number of deletions achieved. We will prune these out of the
1819 insertion/deletion sets. */
1820 auto_sbitmap
prune_exprs (n_elems
);
1821 bitmap_clear (prune_exprs
);
1823 /* Iterate over the edges counting the number of times each expression
1824 needs to be inserted. */
1825 for (i
= 0; i
< (unsigned) n_edges_for_fn (cfun
); i
++)
1827 EXECUTE_IF_SET_IN_BITMAP (pre_insert_map
[i
], 0, j
, sbi
)
1831 /* Similarly for deletions, but those occur in blocks rather than on
1833 for (i
= 0; i
< (unsigned) last_basic_block_for_fn (cfun
); i
++)
1835 EXECUTE_IF_SET_IN_BITMAP (pre_delete_map
[i
], 0, j
, sbi
)
1839 /* Now that we have accurate counts, iterate over the elements in the
1840 hash table and see if any need too many insertions relative to the
1841 number of evaluations that can be removed. If so, mark them in
1843 for (j
= 0; j
< (unsigned) n_elems
; j
++)
1845 && (insertions
[j
] / deletions
[j
]) > param_max_gcse_insertion_ratio
)
1846 bitmap_set_bit (prune_exprs
, j
);
1848 /* Now prune PRE_INSERT_MAP and PRE_DELETE_MAP based on PRUNE_EXPRS. */
1849 EXECUTE_IF_SET_IN_BITMAP (prune_exprs
, 0, j
, sbi
)
1851 for (i
= 0; i
< (unsigned) n_edges_for_fn (cfun
); i
++)
1852 bitmap_clear_bit (pre_insert_map
[i
], j
);
1854 for (i
= 0; i
< (unsigned) last_basic_block_for_fn (cfun
); i
++)
1855 bitmap_clear_bit (pre_delete_map
[i
], j
);
1862 /* Top level routine to do the dataflow analysis needed by PRE. */
1864 static struct edge_list
*
1865 compute_pre_data (void)
1867 struct edge_list
*edge_list
;
1870 compute_local_properties (transp
, comp
, antloc
, &expr_hash_table
);
1871 prune_expressions (true);
1872 bitmap_vector_clear (ae_kill
, last_basic_block_for_fn (cfun
));
1874 /* Compute ae_kill for each basic block using:
1879 FOR_EACH_BB_FN (bb
, cfun
)
1881 bitmap_ior (ae_kill
[bb
->index
], transp
[bb
->index
], comp
[bb
->index
]);
1882 bitmap_not (ae_kill
[bb
->index
], ae_kill
[bb
->index
]);
1885 edge_list
= pre_edge_lcm (expr_hash_table
.n_elems
, transp
, comp
, antloc
,
1886 ae_kill
, &pre_insert_map
, &pre_delete_map
);
1887 sbitmap_vector_free (antloc
);
1889 sbitmap_vector_free (ae_kill
);
1892 prune_insertions_deletions (expr_hash_table
.n_elems
);
1899 /* Return nonzero if an occurrence of expression EXPR in OCCR_BB would reach
1902 VISITED is a pointer to a working buffer for tracking which BB's have
1903 been visited. It is NULL for the top-level call.
1905 We treat reaching expressions that go through blocks containing the same
1906 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
1907 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
1908 2 as not reaching. The intent is to improve the probability of finding
1909 only one reaching expression and to reduce register lifetimes by picking
1910 the closest such expression. */
1913 pre_expr_reaches_here_p_work (basic_block occr_bb
, struct gcse_expr
*expr
,
1914 basic_block bb
, char *visited
)
1919 FOR_EACH_EDGE (pred
, ei
, bb
->preds
)
1921 basic_block pred_bb
= pred
->src
;
1923 if (pred
->src
== ENTRY_BLOCK_PTR_FOR_FN (cfun
)
1924 /* Has predecessor has already been visited? */
1925 || visited
[pred_bb
->index
])
1926 ;/* Nothing to do. */
1928 /* Does this predecessor generate this expression? */
1929 else if (bitmap_bit_p (comp
[pred_bb
->index
], expr
->bitmap_index
))
1931 /* Is this the occurrence we're looking for?
1932 Note that there's only one generating occurrence per block
1933 so we just need to check the block number. */
1934 if (occr_bb
== pred_bb
)
1937 visited
[pred_bb
->index
] = 1;
1939 /* Ignore this predecessor if it kills the expression. */
1940 else if (! bitmap_bit_p (transp
[pred_bb
->index
], expr
->bitmap_index
))
1941 visited
[pred_bb
->index
] = 1;
1943 /* Neither gen nor kill. */
1946 visited
[pred_bb
->index
] = 1;
1947 if (pre_expr_reaches_here_p_work (occr_bb
, expr
, pred_bb
, visited
))
1952 /* All paths have been checked. */
1956 /* The wrapper for pre_expr_reaches_here_work that ensures that any
1957 memory allocated for that function is returned. */
1960 pre_expr_reaches_here_p (basic_block occr_bb
, struct gcse_expr
*expr
, basic_block bb
)
1963 char *visited
= XCNEWVEC (char, last_basic_block_for_fn (cfun
));
1965 rval
= pre_expr_reaches_here_p_work (occr_bb
, expr
, bb
, visited
);
1971 /* Generate RTL to copy an EXP to REG and return it. */
1974 prepare_copy_insn (rtx reg
, rtx exp
)
1980 /* If the expression is something that's an operand, like a constant,
1981 just copy it to a register. */
1982 if (general_operand (exp
, GET_MODE (reg
)))
1983 emit_move_insn (reg
, exp
);
1985 /* Otherwise, make a new insn to compute this expression and make sure the
1986 insn will be recognized (this also adds any needed CLOBBERs). */
1989 rtx_insn
*insn
= emit_insn (gen_rtx_SET (reg
, exp
));
1991 if (insn_invalid_p (insn
, false))
2001 /* Generate RTL to copy an EXPR to its `reaching_reg' and return it. */
2004 process_insert_insn (struct gcse_expr
*expr
)
2006 rtx reg
= expr
->reaching_reg
;
2007 /* Copy the expression to make sure we don't have any sharing issues. */
2008 rtx exp
= copy_rtx (expr
->expr
);
2010 return prepare_copy_insn (reg
, exp
);
2013 /* Add EXPR to the end of basic block BB.
2015 This is used by both the PRE and code hoisting. */
2018 insert_insn_end_basic_block (struct gcse_expr
*expr
, basic_block bb
)
2020 rtx_insn
*insn
= BB_END (bb
);
2022 rtx reg
= expr
->reaching_reg
;
2023 int regno
= REGNO (reg
);
2024 rtx_insn
*pat
, *pat_end
;
2026 pat
= process_insert_insn (expr
);
2027 gcc_assert (pat
&& INSN_P (pat
));
2030 while (NEXT_INSN (pat_end
) != NULL_RTX
)
2031 pat_end
= NEXT_INSN (pat_end
);
2033 /* If the last insn is a jump, insert EXPR in front. Similarly we need to
2034 take care of trapping instructions in presence of non-call exceptions. */
2037 || (NONJUMP_INSN_P (insn
)
2038 && (!single_succ_p (bb
)
2039 || single_succ_edge (bb
)->flags
& EDGE_ABNORMAL
)))
2041 /* FIXME: What if something in jump uses value set in new insn? */
2042 new_insn
= emit_insn_before_noloc (pat
, insn
, bb
);
2045 /* Likewise if the last insn is a call, as will happen in the presence
2046 of exception handling. */
2047 else if (CALL_P (insn
)
2048 && (!single_succ_p (bb
)
2049 || single_succ_edge (bb
)->flags
& EDGE_ABNORMAL
))
2051 /* Keeping in mind targets with small register classes and parameters
2052 in registers, we search backward and place the instructions before
2053 the first parameter is loaded. Do this for everyone for consistency
2054 and a presumption that we'll get better code elsewhere as well. */
2056 /* Since different machines initialize their parameter registers
2057 in different orders, assume nothing. Collect the set of all
2058 parameter registers. */
2059 insn
= find_first_parameter_load (insn
, BB_HEAD (bb
));
2061 /* If we found all the parameter loads, then we want to insert
2062 before the first parameter load.
2064 If we did not find all the parameter loads, then we might have
2065 stopped on the head of the block, which could be a CODE_LABEL.
2066 If we inserted before the CODE_LABEL, then we would be putting
2067 the insn in the wrong basic block. In that case, put the insn
2068 after the CODE_LABEL. Also, respect NOTE_INSN_BASIC_BLOCK. */
2069 while (LABEL_P (insn
)
2070 || NOTE_INSN_BASIC_BLOCK_P (insn
))
2071 insn
= NEXT_INSN (insn
);
2073 new_insn
= emit_insn_before_noloc (pat
, insn
, bb
);
2076 new_insn
= emit_insn_after_noloc (pat
, insn
, bb
);
2081 add_label_notes (PATTERN (pat
), new_insn
);
2084 pat
= NEXT_INSN (pat
);
2087 gcse_create_count
++;
2091 fprintf (dump_file
, "PRE/HOIST: end of bb %d, insn %d, ",
2092 bb
->index
, INSN_UID (new_insn
));
2093 fprintf (dump_file
, "copying expression %d to reg %d\n",
2094 expr
->bitmap_index
, regno
);
2098 /* Insert partially redundant expressions on edges in the CFG to make
2099 the expressions fully redundant. */
2102 pre_edge_insert (struct edge_list
*edge_list
, struct gcse_expr
**index_map
)
2104 int e
, i
, j
, num_edges
, set_size
, did_insert
= 0;
2107 /* Where PRE_INSERT_MAP is nonzero, we add the expression on that edge
2108 if it reaches any of the deleted expressions. */
2110 set_size
= pre_insert_map
[0]->size
;
2111 num_edges
= NUM_EDGES (edge_list
);
2112 inserted
= sbitmap_vector_alloc (num_edges
, expr_hash_table
.n_elems
);
2113 bitmap_vector_clear (inserted
, num_edges
);
2115 for (e
= 0; e
< num_edges
; e
++)
2118 basic_block bb
= INDEX_EDGE_PRED_BB (edge_list
, e
);
2120 for (i
= indx
= 0; i
< set_size
; i
++, indx
+= SBITMAP_ELT_BITS
)
2122 SBITMAP_ELT_TYPE insert
= pre_insert_map
[e
]->elms
[i
];
2125 insert
&& j
< (int) expr_hash_table
.n_elems
;
2127 if ((insert
& 1) != 0 && index_map
[j
]->reaching_reg
!= NULL_RTX
)
2129 struct gcse_expr
*expr
= index_map
[j
];
2130 struct gcse_occr
*occr
;
2132 /* Now look at each deleted occurrence of this expression. */
2133 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
2135 if (! occr
->deleted_p
)
2138 /* Insert this expression on this edge if it would
2139 reach the deleted occurrence in BB. */
2140 if (!bitmap_bit_p (inserted
[e
], j
))
2143 edge eg
= INDEX_EDGE (edge_list
, e
);
2145 /* We can't insert anything on an abnormal and
2146 critical edge, so we insert the insn at the end of
2147 the previous block. There are several alternatives
2148 detailed in Morgans book P277 (sec 10.5) for
2149 handling this situation. This one is easiest for
2152 if (eg
->flags
& EDGE_ABNORMAL
)
2153 insert_insn_end_basic_block (index_map
[j
], bb
);
2156 insn
= process_insert_insn (index_map
[j
]);
2157 insert_insn_on_edge (insn
, eg
);
2162 fprintf (dump_file
, "PRE: edge (%d,%d), ",
2164 INDEX_EDGE_SUCC_BB (edge_list
, e
)->index
);
2165 fprintf (dump_file
, "copy expression %d\n",
2166 expr
->bitmap_index
);
2169 update_ld_motion_stores (expr
);
2170 bitmap_set_bit (inserted
[e
], j
);
2172 gcse_create_count
++;
2179 sbitmap_vector_free (inserted
);
2183 /* Copy the result of EXPR->EXPR generated by INSN to EXPR->REACHING_REG.
2184 Given "old_reg <- expr" (INSN), instead of adding after it
2185 reaching_reg <- old_reg
2186 it's better to do the following:
2187 reaching_reg <- expr
2188 old_reg <- reaching_reg
2189 because this way copy propagation can discover additional PRE
2190 opportunities. But if this fails, we try the old way.
2191 When "expr" is a store, i.e.
2192 given "MEM <- old_reg", instead of adding after it
2193 reaching_reg <- old_reg
2194 it's better to add it before as follows:
2195 reaching_reg <- old_reg
2196 MEM <- reaching_reg. */
2199 pre_insert_copy_insn (struct gcse_expr
*expr
, rtx_insn
*insn
)
2201 rtx reg
= expr
->reaching_reg
;
2202 int regno
= REGNO (reg
);
2203 int indx
= expr
->bitmap_index
;
2204 rtx pat
= PATTERN (insn
);
2210 /* This block matches the logic in hash_scan_insn. */
2211 switch (GET_CODE (pat
))
2218 /* Search through the parallel looking for the set whose
2219 source was the expression that we're interested in. */
2220 first_set
= NULL_RTX
;
2222 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
2224 rtx x
= XVECEXP (pat
, 0, i
);
2225 if (GET_CODE (x
) == SET
)
2227 /* If the source was a REG_EQUAL or REG_EQUIV note, we
2228 may not find an equivalent expression, but in this
2229 case the PARALLEL will have a single set. */
2230 if (first_set
== NULL_RTX
)
2232 if (expr_equiv_p (SET_SRC (x
), expr
->expr
))
2240 gcc_assert (first_set
);
2241 if (set
== NULL_RTX
)
2249 if (REG_P (SET_DEST (set
)))
2251 old_reg
= SET_DEST (set
);
2252 /* Check if we can modify the set destination in the original insn. */
2253 if (validate_change (insn
, &SET_DEST (set
), reg
, 0))
2255 new_insn
= gen_move_insn (old_reg
, reg
);
2256 new_insn
= emit_insn_after (new_insn
, insn
);
2260 new_insn
= gen_move_insn (reg
, old_reg
);
2261 new_insn
= emit_insn_after (new_insn
, insn
);
2264 else /* This is possible only in case of a store to memory. */
2266 old_reg
= SET_SRC (set
);
2267 new_insn
= gen_move_insn (reg
, old_reg
);
2269 /* Check if we can modify the set source in the original insn. */
2270 if (validate_change (insn
, &SET_SRC (set
), reg
, 0))
2271 new_insn
= emit_insn_before (new_insn
, insn
);
2273 new_insn
= emit_insn_after (new_insn
, insn
);
2276 gcse_create_count
++;
2280 "PRE: bb %d, insn %d, copy expression %d in insn %d to reg %d\n",
2281 BLOCK_FOR_INSN (insn
)->index
, INSN_UID (new_insn
), indx
,
2282 INSN_UID (insn
), regno
);
2285 /* Copy available expressions that reach the redundant expression
2286 to `reaching_reg'. */
2289 pre_insert_copies (void)
2291 unsigned int i
, added_copy
;
2292 struct gcse_expr
*expr
;
2293 struct gcse_occr
*occr
;
2294 struct gcse_occr
*avail
;
2296 /* For each available expression in the table, copy the result to
2297 `reaching_reg' if the expression reaches a deleted one.
2299 ??? The current algorithm is rather brute force.
2300 Need to do some profiling. */
2302 for (i
= 0; i
< expr_hash_table
.size
; i
++)
2303 for (expr
= expr_hash_table
.table
[i
]; expr
; expr
= expr
->next_same_hash
)
2305 /* If the basic block isn't reachable, PPOUT will be TRUE. However,
2306 we don't want to insert a copy here because the expression may not
2307 really be redundant. So only insert an insn if the expression was
2308 deleted. This test also avoids further processing if the
2309 expression wasn't deleted anywhere. */
2310 if (expr
->reaching_reg
== NULL
)
2313 /* Set when we add a copy for that expression. */
2316 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
2318 if (! occr
->deleted_p
)
2321 for (avail
= expr
->avail_occr
; avail
!= NULL
; avail
= avail
->next
)
2323 rtx_insn
*insn
= avail
->insn
;
2325 /* No need to handle this one if handled already. */
2326 if (avail
->copied_p
)
2329 /* Don't handle this one if it's a redundant one. */
2330 if (insn
->deleted ())
2333 /* Or if the expression doesn't reach the deleted one. */
2334 if (! pre_expr_reaches_here_p (BLOCK_FOR_INSN (avail
->insn
),
2336 BLOCK_FOR_INSN (occr
->insn
)))
2341 /* Copy the result of avail to reaching_reg. */
2342 pre_insert_copy_insn (expr
, insn
);
2343 avail
->copied_p
= 1;
2348 update_ld_motion_stores (expr
);
2359 /* Increment number of sets and record set in DATA. */
2362 record_set_data (rtx dest
, const_rtx set
, void *data
)
2364 struct set_data
*s
= (struct set_data
*)data
;
2366 if (GET_CODE (set
) == SET
)
2368 /* We allow insns having multiple sets, where all but one are
2369 dead as single set insns. In the common case only a single
2370 set is present, so we want to avoid checking for REG_UNUSED
2371 notes unless necessary. */
2373 && find_reg_note (s
->insn
, REG_UNUSED
, SET_DEST (s
->set
))
2374 && !side_effects_p (s
->set
))
2379 /* Record this set. */
2383 else if (!find_reg_note (s
->insn
, REG_UNUSED
, dest
)
2384 || side_effects_p (set
))
2390 single_set_gcse (rtx_insn
*insn
)
2395 gcc_assert (INSN_P (insn
));
2397 /* Optimize common case. */
2398 pattern
= PATTERN (insn
);
2399 if (GET_CODE (pattern
) == SET
)
2404 note_pattern_stores (pattern
, record_set_data
, &s
);
2406 /* Considered invariant insns have exactly one set. */
2407 gcc_assert (s
.nsets
== 1);
2411 /* Emit move from SRC to DEST noting the equivalence with expression computed
2415 gcse_emit_move_after (rtx dest
, rtx src
, rtx_insn
*insn
)
2418 const_rtx set
= single_set_gcse (insn
);
2423 /* This should never fail since we're creating a reg->reg copy
2424 we've verified to be valid. */
2426 new_rtx
= emit_insn_after (gen_move_insn (dest
, src
), insn
);
2428 /* Note the equivalence for local CSE pass. Take the note from the old
2429 set if there was one. Otherwise record the SET_SRC from the old set
2430 unless DEST is also an operand of the SET_SRC. */
2431 set2
= single_set (new_rtx
);
2432 if (!set2
|| !rtx_equal_p (SET_DEST (set2
), dest
))
2434 if ((note
= find_reg_equal_equiv_note (insn
)))
2435 eqv
= XEXP (note
, 0);
2436 else if (! REG_P (dest
)
2437 || ! reg_mentioned_p (dest
, SET_SRC (set
)))
2438 eqv
= SET_SRC (set
);
2440 if (eqv
!= NULL_RTX
)
2441 set_unique_reg_note (new_rtx
, REG_EQUAL
, copy_insn_1 (eqv
));
2446 /* Delete redundant computations.
2447 Deletion is done by changing the insn to copy the `reaching_reg' of
2448 the expression into the result of the SET. It is left to later passes
2449 to propagate the copy or eliminate it.
2451 Return nonzero if a change is made. */
2458 struct gcse_expr
*expr
;
2459 struct gcse_occr
*occr
;
2462 for (i
= 0; i
< expr_hash_table
.size
; i
++)
2463 for (expr
= expr_hash_table
.table
[i
]; expr
; expr
= expr
->next_same_hash
)
2465 int indx
= expr
->bitmap_index
;
2467 /* We only need to search antic_occr since we require ANTLOC != 0. */
2468 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
2470 rtx_insn
*insn
= occr
->insn
;
2472 basic_block bb
= BLOCK_FOR_INSN (insn
);
2474 /* We only delete insns that have a single_set. */
2475 if (bitmap_bit_p (pre_delete_map
[bb
->index
], indx
)
2476 && (set
= single_set (insn
)) != 0
2477 && dbg_cnt (pre_insn
))
2479 /* Create a pseudo-reg to store the result of reaching
2480 expressions into. Get the mode for the new pseudo from
2481 the mode of the original destination pseudo. */
2482 if (expr
->reaching_reg
== NULL
)
2483 expr
->reaching_reg
= gen_reg_rtx_and_attrs (SET_DEST (set
));
2485 gcse_emit_move_after (SET_DEST (set
), expr
->reaching_reg
, insn
);
2487 occr
->deleted_p
= 1;
2494 "PRE: redundant insn %d (expression %d) in ",
2495 INSN_UID (insn
), indx
);
2496 fprintf (dump_file
, "bb %d, reaching reg is %d\n",
2497 bb
->index
, REGNO (expr
->reaching_reg
));
2506 /* Perform GCSE optimizations using PRE.
2507 This is called by one_pre_gcse_pass after all the dataflow analysis
2510 This is based on the original Morel-Renvoise paper Fred Chow's thesis, and
2511 lazy code motion from Knoop, Ruthing and Steffen as described in Advanced
2512 Compiler Design and Implementation.
2514 ??? A new pseudo reg is created to hold the reaching expression. The nice
2515 thing about the classical approach is that it would try to use an existing
2516 reg. If the register can't be adequately optimized [i.e. we introduce
2517 reload problems], one could add a pass here to propagate the new register
2520 ??? We don't handle single sets in PARALLELs because we're [currently] not
2521 able to copy the rest of the parallel when we insert copies to create full
2522 redundancies from partial redundancies. However, there's no reason why we
2523 can't handle PARALLELs in the cases where there are no partial
2527 pre_gcse (struct edge_list
*edge_list
)
2530 int did_insert
, changed
;
2531 struct gcse_expr
**index_map
;
2532 struct gcse_expr
*expr
;
2534 /* Compute a mapping from expression number (`bitmap_index') to
2535 hash table entry. */
2537 index_map
= XCNEWVEC (struct gcse_expr
*, expr_hash_table
.n_elems
);
2538 for (i
= 0; i
< expr_hash_table
.size
; i
++)
2539 for (expr
= expr_hash_table
.table
[i
]; expr
; expr
= expr
->next_same_hash
)
2540 index_map
[expr
->bitmap_index
] = expr
;
2542 /* Delete the redundant insns first so that
2543 - we know what register to use for the new insns and for the other
2544 ones with reaching expressions
2545 - we know which insns are redundant when we go to create copies */
2547 changed
= pre_delete ();
2548 did_insert
= pre_edge_insert (edge_list
, index_map
);
2550 /* In other places with reaching expressions, copy the expression to the
2551 specially allocated pseudo-reg that reaches the redundant expr. */
2552 pre_insert_copies ();
2555 commit_edge_insertions ();
2563 /* Top level routine to perform one PRE GCSE pass.
2565 Return nonzero if a change was made. */
2568 one_pre_gcse_pass (void)
2572 gcse_subst_count
= 0;
2573 gcse_create_count
= 0;
2575 /* Return if there's nothing to do, or it is too expensive. */
2576 if (n_basic_blocks_for_fn (cfun
) <= NUM_FIXED_BLOCKS
+ 1
2577 || gcse_or_cprop_is_too_expensive (_("PRE disabled")))
2580 /* We need alias. */
2581 init_alias_analysis ();
2584 gcc_obstack_init (&gcse_obstack
);
2587 alloc_hash_table (&expr_hash_table
);
2588 add_noreturn_fake_exit_edges ();
2590 compute_ld_motion_mems ();
2592 compute_hash_table (&expr_hash_table
);
2594 trim_ld_motion_mems ();
2596 dump_hash_table (dump_file
, "Expression", &expr_hash_table
);
2598 if (expr_hash_table
.n_elems
> 0)
2600 struct edge_list
*edge_list
;
2601 alloc_pre_mem (last_basic_block_for_fn (cfun
), expr_hash_table
.n_elems
);
2602 edge_list
= compute_pre_data ();
2603 changed
|= pre_gcse (edge_list
);
2604 free_edge_list (edge_list
);
2609 free_ld_motion_mems ();
2610 remove_fake_exit_edges ();
2611 free_hash_table (&expr_hash_table
);
2614 obstack_free (&gcse_obstack
, NULL
);
2616 /* We are finished with alias. */
2617 end_alias_analysis ();
2621 fprintf (dump_file
, "PRE GCSE of %s, %d basic blocks, %d bytes needed, ",
2622 current_function_name (), n_basic_blocks_for_fn (cfun
),
2624 fprintf (dump_file
, "%d substs, %d insns created\n",
2625 gcse_subst_count
, gcse_create_count
);
2631 /* If X contains any LABEL_REF's, add REG_LABEL_OPERAND notes for them
2632 to INSN. If such notes are added to an insn which references a
2633 CODE_LABEL, the LABEL_NUSES count is incremented. We have to add
2634 that note, because the following loop optimization pass requires
2637 /* ??? If there was a jump optimization pass after gcse and before loop,
2638 then we would not need to do this here, because jump would add the
2639 necessary REG_LABEL_OPERAND and REG_LABEL_TARGET notes. */
2642 add_label_notes (rtx x
, rtx_insn
*insn
)
2644 enum rtx_code code
= GET_CODE (x
);
2648 if (code
== LABEL_REF
&& !LABEL_REF_NONLOCAL_P (x
))
2650 /* This code used to ignore labels that referred to dispatch tables to
2651 avoid flow generating (slightly) worse code.
2653 We no longer ignore such label references (see LABEL_REF handling in
2654 mark_jump_label for additional information). */
2656 /* There's no reason for current users to emit jump-insns with
2657 such a LABEL_REF, so we don't have to handle REG_LABEL_TARGET
2659 gcc_assert (!JUMP_P (insn
));
2660 add_reg_note (insn
, REG_LABEL_OPERAND
, label_ref_label (x
));
2662 if (LABEL_P (label_ref_label (x
)))
2663 LABEL_NUSES (label_ref_label (x
))++;
2668 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
2671 add_label_notes (XEXP (x
, i
), insn
);
2672 else if (fmt
[i
] == 'E')
2673 for (j
= XVECLEN (x
, i
) - 1; j
>= 0; j
--)
2674 add_label_notes (XVECEXP (x
, i
, j
), insn
);
2678 /* Code Hoisting variables and subroutines. */
2680 /* Very busy expressions. */
2681 static sbitmap
*hoist_vbein
;
2682 static sbitmap
*hoist_vbeout
;
2684 /* ??? We could compute post dominators and run this algorithm in
2685 reverse to perform tail merging, doing so would probably be
2686 more effective than the tail merging code in jump.c.
2688 It's unclear if tail merging could be run in parallel with
2689 code hoisting. It would be nice. */
2691 /* Allocate vars used for code hoisting analysis. */
2694 alloc_code_hoist_mem (int n_blocks
, int n_exprs
)
2696 antloc
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2697 transp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2698 comp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2700 hoist_vbein
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2701 hoist_vbeout
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
2704 /* Free vars used for code hoisting analysis. */
2707 free_code_hoist_mem (void)
2709 sbitmap_vector_free (antloc
);
2710 sbitmap_vector_free (transp
);
2711 sbitmap_vector_free (comp
);
2713 sbitmap_vector_free (hoist_vbein
);
2714 sbitmap_vector_free (hoist_vbeout
);
2716 free_dominance_info (CDI_DOMINATORS
);
2719 /* Compute the very busy expressions at entry/exit from each block.
2721 An expression is very busy if all paths from a given point
2722 compute the expression. */
2725 compute_code_hoist_vbeinout (void)
2727 int changed
, passes
;
2730 bitmap_vector_clear (hoist_vbeout
, last_basic_block_for_fn (cfun
));
2731 bitmap_vector_clear (hoist_vbein
, last_basic_block_for_fn (cfun
));
2740 /* We scan the blocks in the reverse order to speed up
2742 FOR_EACH_BB_REVERSE_FN (bb
, cfun
)
2744 if (bb
->next_bb
!= EXIT_BLOCK_PTR_FOR_FN (cfun
))
2746 bitmap_intersection_of_succs (hoist_vbeout
[bb
->index
],
2749 /* Include expressions in VBEout that are calculated
2750 in BB and available at its end. */
2751 bitmap_ior (hoist_vbeout
[bb
->index
],
2752 hoist_vbeout
[bb
->index
], comp
[bb
->index
]);
2755 changed
|= bitmap_or_and (hoist_vbein
[bb
->index
],
2757 hoist_vbeout
[bb
->index
],
2766 fprintf (dump_file
, "hoisting vbeinout computation: %d passes\n", passes
);
2768 FOR_EACH_BB_FN (bb
, cfun
)
2770 fprintf (dump_file
, "vbein (%d): ", bb
->index
);
2771 dump_bitmap_file (dump_file
, hoist_vbein
[bb
->index
]);
2772 fprintf (dump_file
, "vbeout(%d): ", bb
->index
);
2773 dump_bitmap_file (dump_file
, hoist_vbeout
[bb
->index
]);
2778 /* Top level routine to do the dataflow analysis needed by code hoisting. */
2781 compute_code_hoist_data (void)
2783 compute_local_properties (transp
, comp
, antloc
, &expr_hash_table
);
2784 prune_expressions (false);
2785 compute_code_hoist_vbeinout ();
2786 calculate_dominance_info (CDI_DOMINATORS
);
2788 fprintf (dump_file
, "\n");
2791 /* Update register pressure for BB when hoisting an expression from
2792 instruction FROM, if live ranges of inputs are shrunk. Also
2793 maintain live_in information if live range of register referred
2796 Return 0 if register pressure doesn't change, otherwise return
2797 the number by which register pressure is decreased.
2799 NOTE: Register pressure won't be increased in this function. */
2802 update_bb_reg_pressure (basic_block bb
, rtx_insn
*from
)
2806 basic_block succ_bb
;
2810 int decreased_pressure
= 0;
2812 enum reg_class pressure_class
;
2814 FOR_EACH_INSN_USE (use
, from
)
2816 dreg
= DF_REF_REAL_REG (use
);
2817 /* The live range of register is shrunk only if it isn't:
2818 1. referred on any path from the end of this block to EXIT, or
2819 2. referred by insns other than FROM in this block. */
2820 FOR_EACH_EDGE (succ
, ei
, bb
->succs
)
2822 succ_bb
= succ
->dest
;
2823 if (succ_bb
== EXIT_BLOCK_PTR_FOR_FN (cfun
))
2826 if (bitmap_bit_p (BB_DATA (succ_bb
)->live_in
, REGNO (dreg
)))
2832 op_ref
= DF_REG_USE_CHAIN (REGNO (dreg
));
2833 for (; op_ref
; op_ref
= DF_REF_NEXT_REG (op_ref
))
2835 if (!DF_REF_INSN_INFO (op_ref
))
2838 insn
= DF_REF_INSN (op_ref
);
2839 if (BLOCK_FOR_INSN (insn
) == bb
2840 && NONDEBUG_INSN_P (insn
) && insn
!= from
)
2844 pressure_class
= get_regno_pressure_class (REGNO (dreg
), &nregs
);
2845 /* Decrease register pressure and update live_in information for
2847 if (!op_ref
&& pressure_class
!= NO_REGS
)
2849 decreased_pressure
+= nregs
;
2850 BB_DATA (bb
)->max_reg_pressure
[pressure_class
] -= nregs
;
2851 bitmap_clear_bit (BB_DATA (bb
)->live_in
, REGNO (dreg
));
2854 return decreased_pressure
;
2857 /* Determine if the expression EXPR should be hoisted to EXPR_BB up in
2858 flow graph, if it can reach BB unimpared. Stop the search if the
2859 expression would need to be moved more than DISTANCE instructions.
2861 DISTANCE is the number of instructions through which EXPR can be
2862 hoisted up in flow graph.
2864 BB_SIZE points to an array which contains the number of instructions
2865 for each basic block.
2867 PRESSURE_CLASS and NREGS are register class and number of hard registers
2870 HOISTED_BBS points to a bitmap indicating basic blocks through which
2873 FROM is the instruction from which EXPR is hoisted.
2875 It's unclear exactly what Muchnick meant by "unimpared". It seems
2876 to me that the expression must either be computed or transparent in
2877 *every* block in the path(s) from EXPR_BB to BB. Any other definition
2878 would allow the expression to be hoisted out of loops, even if
2879 the expression wasn't a loop invariant.
2881 Contrast this to reachability for PRE where an expression is
2882 considered reachable if *any* path reaches instead of *all*
2886 should_hoist_expr_to_dom (basic_block expr_bb
, struct gcse_expr
*expr
,
2887 basic_block bb
, sbitmap visited
,
2888 HOST_WIDE_INT distance
,
2889 int *bb_size
, enum reg_class pressure_class
,
2890 int *nregs
, bitmap hoisted_bbs
, rtx_insn
*from
)
2895 sbitmap_iterator sbi
;
2896 int visited_allocated_locally
= 0;
2897 int decreased_pressure
= 0;
2899 if (flag_ira_hoist_pressure
)
2901 /* Record old information of basic block BB when it is visited
2902 at the first time. */
2903 if (!bitmap_bit_p (hoisted_bbs
, bb
->index
))
2905 struct bb_data
*data
= BB_DATA (bb
);
2906 bitmap_copy (data
->backup
, data
->live_in
);
2907 data
->old_pressure
= data
->max_reg_pressure
[pressure_class
];
2909 decreased_pressure
= update_bb_reg_pressure (bb
, from
);
2911 /* Terminate the search if distance, for which EXPR is allowed to move,
2915 if (flag_ira_hoist_pressure
)
2917 /* Prefer to hoist EXPR if register pressure is decreased. */
2918 if (decreased_pressure
> *nregs
)
2919 distance
+= bb_size
[bb
->index
];
2920 /* Let EXPR be hoisted through basic block at no cost if one
2921 of following conditions is satisfied:
2923 1. The basic block has low register pressure.
2924 2. Register pressure won't be increases after hoisting EXPR.
2926 Constant expressions is handled conservatively, because
2927 hoisting constant expression aggressively results in worse
2928 code. This decision is made by the observation of CSiBE
2929 on ARM target, while it has no obvious effect on other
2930 targets like x86, x86_64, mips and powerpc. */
2931 else if (CONST_INT_P (expr
->expr
)
2932 || (BB_DATA (bb
)->max_reg_pressure
[pressure_class
]
2933 >= ira_class_hard_regs_num
[pressure_class
]
2934 && decreased_pressure
< *nregs
))
2935 distance
-= bb_size
[bb
->index
];
2938 distance
-= bb_size
[bb
->index
];
2944 gcc_assert (distance
== 0);
2946 if (visited
== NULL
)
2948 visited_allocated_locally
= 1;
2949 visited
= sbitmap_alloc (last_basic_block_for_fn (cfun
));
2950 bitmap_clear (visited
);
2953 FOR_EACH_EDGE (pred
, ei
, bb
->preds
)
2955 basic_block pred_bb
= pred
->src
;
2957 if (pred
->src
== ENTRY_BLOCK_PTR_FOR_FN (cfun
))
2959 else if (pred_bb
== expr_bb
)
2961 else if (bitmap_bit_p (visited
, pred_bb
->index
))
2963 else if (! bitmap_bit_p (transp
[pred_bb
->index
], expr
->bitmap_index
))
2968 bitmap_set_bit (visited
, pred_bb
->index
);
2969 if (! should_hoist_expr_to_dom (expr_bb
, expr
, pred_bb
,
2970 visited
, distance
, bb_size
,
2971 pressure_class
, nregs
,
2976 if (visited_allocated_locally
)
2978 /* If EXPR can be hoisted to expr_bb, record basic blocks through
2979 which EXPR is hoisted in hoisted_bbs. */
2980 if (flag_ira_hoist_pressure
&& !pred
)
2982 /* Record the basic block from which EXPR is hoisted. */
2983 bitmap_set_bit (visited
, bb
->index
);
2984 EXECUTE_IF_SET_IN_BITMAP (visited
, 0, i
, sbi
)
2985 bitmap_set_bit (hoisted_bbs
, i
);
2987 sbitmap_free (visited
);
2990 return (pred
== NULL
);
2993 /* Find occurrence in BB. */
2995 static struct gcse_occr
*
2996 find_occr_in_bb (struct gcse_occr
*occr
, basic_block bb
)
2998 /* Find the right occurrence of this expression. */
2999 while (occr
&& BLOCK_FOR_INSN (occr
->insn
) != bb
)
3005 /* Actually perform code hoisting.
3007 The code hoisting pass can hoist multiple computations of the same
3008 expression along dominated path to a dominating basic block, like
3009 from b2/b3 to b1 as depicted below:
3019 Unfortunately code hoisting generally extends the live range of an
3020 output pseudo register, which increases register pressure and hurts
3021 register allocation. To address this issue, an attribute MAX_DISTANCE
3022 is computed and attached to each expression. The attribute is computed
3023 from rtx cost of the corresponding expression and it's used to control
3024 how long the expression can be hoisted up in flow graph. As the
3025 expression is hoisted up in flow graph, GCC decreases its DISTANCE
3026 and stops the hoist if DISTANCE reaches 0. Code hoisting can decrease
3027 register pressure if live ranges of inputs are shrunk.
3029 Option "-fira-hoist-pressure" implements register pressure directed
3030 hoist based on upper method. The rationale is:
3031 1. Calculate register pressure for each basic block by reusing IRA
3033 2. When expression is hoisted through one basic block, GCC checks
3034 the change of live ranges for inputs/output. The basic block's
3035 register pressure will be increased because of extended live
3036 range of output. However, register pressure will be decreased
3037 if the live ranges of inputs are shrunk.
3038 3. After knowing how hoisting affects register pressure, GCC prefers
3039 to hoist the expression if it can decrease register pressure, by
3040 increasing DISTANCE of the corresponding expression.
3041 4. If hoisting the expression increases register pressure, GCC checks
3042 register pressure of the basic block and decrease DISTANCE only if
3043 the register pressure is high. In other words, expression will be
3044 hoisted through at no cost if the basic block has low register
3046 5. Update register pressure information for basic blocks through
3047 which expression is hoisted. */
3052 basic_block bb
, dominated
;
3053 unsigned int dom_tree_walk_index
;
3054 unsigned int i
, j
, k
;
3055 struct gcse_expr
**index_map
;
3056 struct gcse_expr
*expr
;
3060 struct bb_data
*data
;
3061 /* Basic blocks that have occurrences reachable from BB. */
3063 /* Basic blocks through which expr is hoisted. */
3064 bitmap hoisted_bbs
= NULL
;
3067 /* Compute a mapping from expression number (`bitmap_index') to
3068 hash table entry. */
3070 index_map
= XCNEWVEC (struct gcse_expr
*, expr_hash_table
.n_elems
);
3071 for (i
= 0; i
< expr_hash_table
.size
; i
++)
3072 for (expr
= expr_hash_table
.table
[i
]; expr
; expr
= expr
->next_same_hash
)
3073 index_map
[expr
->bitmap_index
] = expr
;
3075 /* Calculate sizes of basic blocks and note how far
3076 each instruction is from the start of its block. We then use this
3077 data to restrict distance an expression can travel. */
3079 to_bb_head
= XCNEWVEC (int, get_max_uid ());
3080 bb_size
= XCNEWVEC (int, last_basic_block_for_fn (cfun
));
3082 FOR_EACH_BB_FN (bb
, cfun
)
3088 FOR_BB_INSNS (bb
, insn
)
3090 /* Don't count debug instructions to avoid them affecting
3091 decision choices. */
3092 if (NONDEBUG_INSN_P (insn
))
3093 to_bb_head
[INSN_UID (insn
)] = to_head
++;
3096 bb_size
[bb
->index
] = to_head
;
3099 gcc_assert (EDGE_COUNT (ENTRY_BLOCK_PTR_FOR_FN (cfun
)->succs
) == 1
3100 && (EDGE_SUCC (ENTRY_BLOCK_PTR_FOR_FN (cfun
), 0)->dest
3101 == ENTRY_BLOCK_PTR_FOR_FN (cfun
)->next_bb
));
3103 from_bbs
= BITMAP_ALLOC (NULL
);
3104 if (flag_ira_hoist_pressure
)
3105 hoisted_bbs
= BITMAP_ALLOC (NULL
);
3107 auto_vec
<basic_block
> dom_tree_walk
3108 = get_all_dominated_blocks (CDI_DOMINATORS
,
3109 ENTRY_BLOCK_PTR_FOR_FN (cfun
)->next_bb
);
3111 /* Walk over each basic block looking for potentially hoistable
3112 expressions, nothing gets hoisted from the entry block. */
3113 FOR_EACH_VEC_ELT (dom_tree_walk
, dom_tree_walk_index
, bb
)
3115 auto_vec
<basic_block
> domby
3116 = get_dominated_to_depth (CDI_DOMINATORS
, bb
, param_max_hoist_depth
);
3118 if (domby
.length () == 0)
3121 /* Examine each expression that is very busy at the exit of this
3122 block. These are the potentially hoistable expressions. */
3123 for (i
= 0; i
< SBITMAP_SIZE (hoist_vbeout
[bb
->index
]); i
++)
3125 if (bitmap_bit_p (hoist_vbeout
[bb
->index
], i
))
3128 enum reg_class pressure_class
= NO_REGS
;
3129 /* Current expression. */
3130 struct gcse_expr
*expr
= index_map
[i
];
3131 /* Number of occurrences of EXPR that can be hoisted to BB. */
3133 /* Occurrences reachable from BB. */
3134 vec
<occr_t
> occrs_to_hoist
= vNULL
;
3135 /* We want to insert the expression into BB only once, so
3136 note when we've inserted it. */
3137 int insn_inserted_p
;
3140 /* If an expression is computed in BB and is available at end of
3141 BB, hoist all occurrences dominated by BB to BB. */
3142 if (bitmap_bit_p (comp
[bb
->index
], i
))
3144 occr
= find_occr_in_bb (expr
->antic_occr
, bb
);
3148 /* An occurrence might've been already deleted
3149 while processing a dominator of BB. */
3150 if (!occr
->deleted_p
)
3152 gcc_assert (NONDEBUG_INSN_P (occr
->insn
));
3160 /* We've found a potentially hoistable expression, now
3161 we look at every block BB dominates to see if it
3162 computes the expression. */
3163 FOR_EACH_VEC_ELT (domby
, j
, dominated
)
3165 HOST_WIDE_INT max_distance
;
3167 /* Ignore self dominance. */
3168 if (bb
== dominated
)
3170 /* We've found a dominated block, now see if it computes
3171 the busy expression and whether or not moving that
3172 expression to the "beginning" of that block is safe. */
3173 if (!bitmap_bit_p (antloc
[dominated
->index
], i
))
3176 occr
= find_occr_in_bb (expr
->antic_occr
, dominated
);
3179 /* An occurrence might've been already deleted
3180 while processing a dominator of BB. */
3181 if (occr
->deleted_p
)
3183 gcc_assert (NONDEBUG_INSN_P (occr
->insn
));
3185 max_distance
= expr
->max_distance
;
3186 if (max_distance
> 0)
3187 /* Adjust MAX_DISTANCE to account for the fact that
3188 OCCR won't have to travel all of DOMINATED, but
3190 max_distance
+= (bb_size
[dominated
->index
]
3191 - to_bb_head
[INSN_UID (occr
->insn
)]);
3193 pressure_class
= get_pressure_class_and_nregs (occr
->insn
,
3196 /* Note if the expression should be hoisted from the dominated
3197 block to BB if it can reach DOMINATED unimpared.
3199 Keep track of how many times this expression is hoistable
3200 from a dominated block into BB. */
3201 if (should_hoist_expr_to_dom (bb
, expr
, dominated
, NULL
,
3202 max_distance
, bb_size
,
3203 pressure_class
, &nregs
,
3204 hoisted_bbs
, occr
->insn
))
3207 occrs_to_hoist
.safe_push (occr
);
3208 bitmap_set_bit (from_bbs
, dominated
->index
);
3212 /* If we found more than one hoistable occurrence of this
3213 expression, then note it in the vector of expressions to
3214 hoist. It makes no sense to hoist things which are computed
3215 in only one BB, and doing so tends to pessimize register
3216 allocation. One could increase this value to try harder
3217 to avoid any possible code expansion due to register
3218 allocation issues; however experiments have shown that
3219 the vast majority of hoistable expressions are only movable
3220 from two successors, so raising this threshold is likely
3221 to nullify any benefit we get from code hoisting. */
3222 if (hoistable
> 1 && dbg_cnt (hoist_insn
))
3224 /* If (hoistable != vec::length), then there is
3225 an occurrence of EXPR in BB itself. Don't waste
3226 time looking for LCA in this case. */
3227 if ((unsigned) hoistable
== occrs_to_hoist
.length ())
3231 lca
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
3234 /* Punt, it's better to hoist these occurrences to
3236 occrs_to_hoist
.release ();
3240 /* Punt, no point hoisting a single occurrence. */
3241 occrs_to_hoist
.release ();
3243 if (flag_ira_hoist_pressure
3244 && !occrs_to_hoist
.is_empty ())
3246 /* Increase register pressure of basic blocks to which
3247 expr is hoisted because of extended live range of
3249 data
= BB_DATA (bb
);
3250 data
->max_reg_pressure
[pressure_class
] += nregs
;
3251 EXECUTE_IF_SET_IN_BITMAP (hoisted_bbs
, 0, k
, bi
)
3253 data
= BB_DATA (BASIC_BLOCK_FOR_FN (cfun
, k
));
3254 data
->max_reg_pressure
[pressure_class
] += nregs
;
3257 else if (flag_ira_hoist_pressure
)
3259 /* Restore register pressure and live_in info for basic
3260 blocks recorded in hoisted_bbs when expr will not be
3262 EXECUTE_IF_SET_IN_BITMAP (hoisted_bbs
, 0, k
, bi
)
3264 data
= BB_DATA (BASIC_BLOCK_FOR_FN (cfun
, k
));
3265 bitmap_copy (data
->live_in
, data
->backup
);
3266 data
->max_reg_pressure
[pressure_class
]
3267 = data
->old_pressure
;
3271 if (flag_ira_hoist_pressure
)
3272 bitmap_clear (hoisted_bbs
);
3274 insn_inserted_p
= 0;
3276 /* Walk through occurrences of I'th expressions we want
3277 to hoist to BB and make the transformations. */
3278 FOR_EACH_VEC_ELT (occrs_to_hoist
, j
, occr
)
3283 gcc_assert (!occr
->deleted_p
);
3286 set
= single_set_gcse (insn
);
3288 /* Create a pseudo-reg to store the result of reaching
3289 expressions into. Get the mode for the new pseudo
3290 from the mode of the original destination pseudo.
3292 It is important to use new pseudos whenever we
3293 emit a set. This will allow reload to use
3294 rematerialization for such registers. */
3295 if (!insn_inserted_p
)
3297 = gen_reg_rtx_and_attrs (SET_DEST (set
));
3299 gcse_emit_move_after (SET_DEST (set
), expr
->reaching_reg
,
3302 occr
->deleted_p
= 1;
3306 if (!insn_inserted_p
)
3308 insert_insn_end_basic_block (expr
, bb
);
3309 insn_inserted_p
= 1;
3313 occrs_to_hoist
.release ();
3314 bitmap_clear (from_bbs
);
3319 BITMAP_FREE (from_bbs
);
3320 if (flag_ira_hoist_pressure
)
3321 BITMAP_FREE (hoisted_bbs
);
3330 /* Return pressure class and number of needed hard registers (through
3331 *NREGS) of register REGNO. */
3332 static enum reg_class
3333 get_regno_pressure_class (int regno
, int *nregs
)
3335 if (regno
>= FIRST_PSEUDO_REGISTER
)
3337 enum reg_class pressure_class
;
3339 pressure_class
= reg_allocno_class (regno
);
3340 pressure_class
= ira_pressure_class_translate
[pressure_class
];
3342 = ira_reg_class_max_nregs
[pressure_class
][PSEUDO_REGNO_MODE (regno
)];
3343 return pressure_class
;
3345 else if (! TEST_HARD_REG_BIT (ira_no_alloc_regs
, regno
)
3346 && ! TEST_HARD_REG_BIT (eliminable_regset
, regno
))
3349 return ira_pressure_class_translate
[REGNO_REG_CLASS (regno
)];
3358 /* Return pressure class and number of hard registers (through *NREGS)
3359 for destination of INSN. */
3360 static enum reg_class
3361 get_pressure_class_and_nregs (rtx_insn
*insn
, int *nregs
)
3364 enum reg_class pressure_class
;
3365 const_rtx set
= single_set_gcse (insn
);
3367 reg
= SET_DEST (set
);
3368 if (GET_CODE (reg
) == SUBREG
)
3369 reg
= SUBREG_REG (reg
);
3373 pressure_class
= NO_REGS
;
3377 gcc_assert (REG_P (reg
));
3378 pressure_class
= reg_allocno_class (REGNO (reg
));
3379 pressure_class
= ira_pressure_class_translate
[pressure_class
];
3381 = ira_reg_class_max_nregs
[pressure_class
][GET_MODE (SET_SRC (set
))];
3383 return pressure_class
;
3386 /* Increase (if INCR_P) or decrease current register pressure for
3389 change_pressure (int regno
, bool incr_p
)
3392 enum reg_class pressure_class
;
3394 pressure_class
= get_regno_pressure_class (regno
, &nregs
);
3396 curr_reg_pressure
[pressure_class
] -= nregs
;
3399 curr_reg_pressure
[pressure_class
] += nregs
;
3400 if (BB_DATA (curr_bb
)->max_reg_pressure
[pressure_class
]
3401 < curr_reg_pressure
[pressure_class
])
3402 BB_DATA (curr_bb
)->max_reg_pressure
[pressure_class
]
3403 = curr_reg_pressure
[pressure_class
];
3407 /* Calculate register pressure for each basic block by walking insns
3408 from last to first. */
3410 calculate_bb_reg_pressure (void)
3416 bitmap curr_regs_live
;
3420 ira_setup_eliminable_regset ();
3421 curr_regs_live
= BITMAP_ALLOC (®_obstack
);
3422 FOR_EACH_BB_FN (bb
, cfun
)
3425 BB_DATA (bb
)->live_in
= BITMAP_ALLOC (NULL
);
3426 BB_DATA (bb
)->backup
= BITMAP_ALLOC (NULL
);
3427 bitmap_copy (BB_DATA (bb
)->live_in
, df_get_live_in (bb
));
3428 bitmap_copy (curr_regs_live
, df_get_live_out (bb
));
3429 for (i
= 0; i
< ira_pressure_classes_num
; i
++)
3430 curr_reg_pressure
[ira_pressure_classes
[i
]] = 0;
3431 EXECUTE_IF_SET_IN_BITMAP (curr_regs_live
, 0, j
, bi
)
3432 change_pressure (j
, true);
3434 FOR_BB_INSNS_REVERSE (bb
, insn
)
3440 if (! NONDEBUG_INSN_P (insn
))
3443 FOR_EACH_INSN_DEF (def
, insn
)
3445 dreg
= DF_REF_REAL_REG (def
);
3446 gcc_assert (REG_P (dreg
));
3447 regno
= REGNO (dreg
);
3448 if (!(DF_REF_FLAGS (def
)
3449 & (DF_REF_PARTIAL
| DF_REF_CONDITIONAL
)))
3451 if (bitmap_clear_bit (curr_regs_live
, regno
))
3452 change_pressure (regno
, false);
3456 FOR_EACH_INSN_USE (use
, insn
)
3458 dreg
= DF_REF_REAL_REG (use
);
3459 gcc_assert (REG_P (dreg
));
3460 regno
= REGNO (dreg
);
3461 if (bitmap_set_bit (curr_regs_live
, regno
))
3462 change_pressure (regno
, true);
3466 BITMAP_FREE (curr_regs_live
);
3468 if (dump_file
== NULL
)
3471 fprintf (dump_file
, "\nRegister Pressure: \n");
3472 FOR_EACH_BB_FN (bb
, cfun
)
3474 fprintf (dump_file
, " Basic block %d: \n", bb
->index
);
3475 for (i
= 0; (int) i
< ira_pressure_classes_num
; i
++)
3477 enum reg_class pressure_class
;
3479 pressure_class
= ira_pressure_classes
[i
];
3480 if (BB_DATA (bb
)->max_reg_pressure
[pressure_class
] == 0)
3483 fprintf (dump_file
, " %s=%d\n", reg_class_names
[pressure_class
],
3484 BB_DATA (bb
)->max_reg_pressure
[pressure_class
]);
3487 fprintf (dump_file
, "\n");
3490 /* Top level routine to perform one code hoisting (aka unification) pass
3492 Return nonzero if a change was made. */
3495 one_code_hoisting_pass (void)
3499 gcse_subst_count
= 0;
3500 gcse_create_count
= 0;
3502 /* Return if there's nothing to do, or it is too expensive. */
3503 if (n_basic_blocks_for_fn (cfun
) <= NUM_FIXED_BLOCKS
+ 1
3504 || gcse_or_cprop_is_too_expensive (_("GCSE disabled")))
3507 doing_code_hoisting_p
= true;
3509 /* Calculate register pressure for each basic block. */
3510 if (flag_ira_hoist_pressure
)
3512 regstat_init_n_sets_and_refs ();
3513 ira_set_pseudo_classes (false, dump_file
);
3514 alloc_aux_for_blocks (sizeof (struct bb_data
));
3515 calculate_bb_reg_pressure ();
3516 regstat_free_n_sets_and_refs ();
3519 /* We need alias. */
3520 init_alias_analysis ();
3523 gcc_obstack_init (&gcse_obstack
);
3526 alloc_hash_table (&expr_hash_table
);
3527 compute_hash_table (&expr_hash_table
);
3529 dump_hash_table (dump_file
, "Code Hosting Expressions", &expr_hash_table
);
3531 if (expr_hash_table
.n_elems
> 0)
3533 alloc_code_hoist_mem (last_basic_block_for_fn (cfun
),
3534 expr_hash_table
.n_elems
);
3535 compute_code_hoist_data ();
3536 changed
= hoist_code ();
3537 free_code_hoist_mem ();
3540 if (flag_ira_hoist_pressure
)
3542 free_aux_for_blocks ();
3545 free_hash_table (&expr_hash_table
);
3547 obstack_free (&gcse_obstack
, NULL
);
3549 /* We are finished with alias. */
3550 end_alias_analysis ();
3554 fprintf (dump_file
, "HOIST of %s, %d basic blocks, %d bytes needed, ",
3555 current_function_name (), n_basic_blocks_for_fn (cfun
),
3557 fprintf (dump_file
, "%d substs, %d insns created\n",
3558 gcse_subst_count
, gcse_create_count
);
3561 doing_code_hoisting_p
= false;
3566 /* Here we provide the things required to do store motion towards the exit.
3567 In order for this to be effective, gcse also needed to be taught how to
3568 move a load when it is killed only by a store to itself.
3573 void foo(float scale)
3575 for (i=0; i<10; i++)
3579 'i' is both loaded and stored to in the loop. Normally, gcse cannot move
3580 the load out since its live around the loop, and stored at the bottom
3583 The 'Load Motion' referred to and implemented in this file is
3584 an enhancement to gcse which when using edge based LCM, recognizes
3585 this situation and allows gcse to move the load out of the loop.
3587 Once gcse has hoisted the load, store motion can then push this
3588 load towards the exit, and we end up with no loads or stores of 'i'
3591 /* This will search the ldst list for a matching expression. If it
3592 doesn't find one, we create one and initialize it. */
3594 static struct ls_expr
*
3597 int do_not_record_p
= 0;
3598 struct ls_expr
* ptr
;
3603 hash
= hash_rtx (x
, GET_MODE (x
), &do_not_record_p
,
3604 NULL
, /*have_reg_qty=*/false);
3607 slot
= pre_ldst_table
->find_slot_with_hash (&e
, hash
, INSERT
);
3611 ptr
= XNEW (struct ls_expr
);
3613 ptr
->next
= pre_ldst_mems
;
3616 ptr
->pattern_regs
= NULL_RTX
;
3617 ptr
->stores
.create (0);
3618 ptr
->reaching_reg
= NULL_RTX
;
3621 ptr
->hash_index
= hash
;
3622 pre_ldst_mems
= ptr
;
3628 /* Free up an individual ldst entry. */
3631 free_ldst_entry (struct ls_expr
* ptr
)
3633 ptr
->stores
.release ();
3638 /* Free up all memory associated with the ldst list. */
3641 free_ld_motion_mems (void)
3643 delete pre_ldst_table
;
3644 pre_ldst_table
= NULL
;
3646 while (pre_ldst_mems
)
3648 struct ls_expr
* tmp
= pre_ldst_mems
;
3650 pre_ldst_mems
= pre_ldst_mems
->next
;
3652 free_ldst_entry (tmp
);
3655 pre_ldst_mems
= NULL
;
3658 /* Dump debugging info about the ldst list. */
3661 print_ldst_list (FILE * file
)
3663 struct ls_expr
* ptr
;
3665 fprintf (file
, "LDST list: \n");
3667 for (ptr
= pre_ldst_mems
; ptr
!= NULL
; ptr
= ptr
->next
)
3669 fprintf (file
, " Pattern (%3d): ", ptr
->index
);
3671 print_rtl (file
, ptr
->pattern
);
3673 fprintf (file
, "\n Stores : ");
3674 print_rtx_insn_vec (file
, ptr
->stores
);
3676 fprintf (file
, "\n\n");
3679 fprintf (file
, "\n");
3682 /* Returns 1 if X is in the list of ldst only expressions. */
3684 static struct ls_expr
*
3685 find_rtx_in_ldst (rtx x
)
3689 if (!pre_ldst_table
)
3692 slot
= pre_ldst_table
->find_slot (&e
, NO_INSERT
);
3693 if (!slot
|| (*slot
)->invalid
)
3698 /* Load Motion for loads which only kill themselves. */
3700 /* Return true if x, a MEM, is a simple access with no side effects.
3701 These are the types of loads we consider for the ld_motion list,
3702 otherwise we let the usual aliasing take care of it. */
3705 simple_mem (const_rtx x
)
3707 if (MEM_VOLATILE_P (x
))
3710 if (GET_MODE (x
) == BLKmode
)
3713 /* If we are handling exceptions, we must be careful with memory references
3714 that may trap. If we are not, the behavior is undefined, so we may just
3716 if (cfun
->can_throw_non_call_exceptions
&& may_trap_p (x
))
3719 if (side_effects_p (x
))
3722 /* Do not consider function arguments passed on stack. */
3723 if (reg_mentioned_p (stack_pointer_rtx
, x
))
3726 if (flag_float_store
&& FLOAT_MODE_P (GET_MODE (x
)))
3732 /* Make sure there isn't a buried reference in this pattern anywhere.
3733 If there is, invalidate the entry for it since we're not capable
3734 of fixing it up just yet.. We have to be sure we know about ALL
3735 loads since the aliasing code will allow all entries in the
3736 ld_motion list to not-alias itself. If we miss a load, we will get
3737 the wrong value since gcse might common it and we won't know to
3741 invalidate_any_buried_refs (rtx x
)
3745 struct ls_expr
* ptr
;
3747 /* Invalidate it in the list. */
3748 if (MEM_P (x
) && simple_mem (x
))
3750 ptr
= ldst_entry (x
);
3754 /* Recursively process the insn. */
3755 fmt
= GET_RTX_FORMAT (GET_CODE (x
));
3757 for (i
= GET_RTX_LENGTH (GET_CODE (x
)) - 1; i
>= 0; i
--)
3760 invalidate_any_buried_refs (XEXP (x
, i
));
3761 else if (fmt
[i
] == 'E')
3762 for (j
= XVECLEN (x
, i
) - 1; j
>= 0; j
--)
3763 invalidate_any_buried_refs (XVECEXP (x
, i
, j
));
3767 /* Find all the 'simple' MEMs which are used in LOADs and STORES. Simple
3768 being defined as MEM loads and stores to symbols, with no side effects
3769 and no registers in the expression. For a MEM destination, we also
3770 check that the insn is still valid if we replace the destination with a
3771 REG, as is done in update_ld_motion_stores. If there are any uses/defs
3772 which don't match this criteria, they are invalidated and trimmed out
3776 compute_ld_motion_mems (void)
3778 struct ls_expr
* ptr
;
3782 pre_ldst_mems
= NULL
;
3783 pre_ldst_table
= new hash_table
<pre_ldst_expr_hasher
> (13);
3785 FOR_EACH_BB_FN (bb
, cfun
)
3787 FOR_BB_INSNS (bb
, insn
)
3789 if (NONDEBUG_INSN_P (insn
))
3791 if (GET_CODE (PATTERN (insn
)) == SET
)
3793 rtx src
= SET_SRC (PATTERN (insn
));
3794 rtx dest
= SET_DEST (PATTERN (insn
));
3796 /* Check for a simple load. */
3797 if (MEM_P (src
) && simple_mem (src
))
3799 ptr
= ldst_entry (src
);
3805 /* Make sure there isn't a buried load somewhere. */
3806 invalidate_any_buried_refs (src
);
3809 /* Check for a simple load through a REG_EQUAL note. */
3810 rtx note
= find_reg_equal_equiv_note (insn
), src_eq
;
3812 && REG_NOTE_KIND (note
) == REG_EQUAL
3813 && (src_eq
= XEXP (note
, 0))
3814 && !(MEM_P (src_eq
) && simple_mem (src_eq
)))
3815 invalidate_any_buried_refs (src_eq
);
3817 /* Check for stores. Don't worry about aliased ones, they
3818 will block any movement we might do later. We only care
3819 about this exact pattern since those are the only
3820 circumstance that we will ignore the aliasing info. */
3821 if (MEM_P (dest
) && simple_mem (dest
))
3823 ptr
= ldst_entry (dest
);
3824 machine_mode src_mode
= GET_MODE (src
);
3826 && GET_CODE (src
) != ASM_OPERANDS
3827 /* Check for REG manually since want_to_gcse_p
3828 returns 0 for all REGs. */
3829 && can_assign_to_reg_without_clobbers_p (src
,
3831 ptr
->stores
.safe_push (insn
);
3838 /* Invalidate all MEMs in the pattern and... */
3839 invalidate_any_buried_refs (PATTERN (insn
));
3841 /* ...in REG_EQUAL notes for PARALLELs with single SET. */
3842 rtx note
= find_reg_equal_equiv_note (insn
), src_eq
;
3844 && REG_NOTE_KIND (note
) == REG_EQUAL
3845 && (src_eq
= XEXP (note
, 0)))
3846 invalidate_any_buried_refs (src_eq
);
3853 /* Remove any references that have been either invalidated or are not in the
3854 expression list for pre gcse. */
3857 trim_ld_motion_mems (void)
3859 struct ls_expr
* * last
= & pre_ldst_mems
;
3860 struct ls_expr
* ptr
= pre_ldst_mems
;
3864 struct gcse_expr
* expr
;
3866 /* Delete if entry has been made invalid. */
3869 /* Delete if we cannot find this mem in the expression list. */
3870 unsigned int hash
= ptr
->hash_index
% expr_hash_table
.size
;
3872 for (expr
= expr_hash_table
.table
[hash
];
3874 expr
= expr
->next_same_hash
)
3875 if (expr_equiv_p (expr
->expr
, ptr
->pattern
))
3879 expr
= (struct gcse_expr
*) 0;
3883 /* Set the expression field if we are keeping it. */
3891 pre_ldst_table
->remove_elt_with_hash (ptr
, ptr
->hash_index
);
3892 free_ldst_entry (ptr
);
3897 /* Show the world what we've found. */
3898 if (dump_file
&& pre_ldst_mems
!= NULL
)
3899 print_ldst_list (dump_file
);
3902 /* This routine will take an expression which we are replacing with
3903 a reaching register, and update any stores that are needed if
3904 that expression is in the ld_motion list. Stores are updated by
3905 copying their SRC to the reaching register, and then storing
3906 the reaching register into the store location. These keeps the
3907 correct value in the reaching register for the loads. */
3910 update_ld_motion_stores (struct gcse_expr
* expr
)
3912 struct ls_expr
* mem_ptr
;
3914 if ((mem_ptr
= find_rtx_in_ldst (expr
->expr
)))
3916 /* We can try to find just the REACHED stores, but is shouldn't
3917 matter to set the reaching reg everywhere... some might be
3918 dead and should be eliminated later. */
3920 /* We replace (set mem expr) with (set reg expr) (set mem reg)
3921 where reg is the reaching reg used in the load. We checked in
3922 compute_ld_motion_mems that we can replace (set mem expr) with
3923 (set reg expr) in that insn. */
3926 FOR_EACH_VEC_ELT_REVERSE (mem_ptr
->stores
, i
, insn
)
3928 rtx pat
= PATTERN (insn
);
3929 rtx src
= SET_SRC (pat
);
3930 rtx reg
= expr
->reaching_reg
;
3932 /* If we've already copied it, continue. */
3933 if (expr
->reaching_reg
== src
)
3938 fprintf (dump_file
, "PRE: store updated with reaching reg ");
3939 print_rtl (dump_file
, reg
);
3940 fprintf (dump_file
, ":\n ");
3941 print_inline_rtx (dump_file
, insn
, 8);
3942 fprintf (dump_file
, "\n");
3945 rtx_insn
*copy
= gen_move_insn (reg
, copy_rtx (SET_SRC (pat
)));
3946 emit_insn_before (copy
, insn
);
3947 SET_SRC (pat
) = reg
;
3948 df_insn_rescan (insn
);
3950 /* un-recognize this pattern since it's probably different now. */
3951 INSN_CODE (insn
) = -1;
3952 gcse_create_count
++;
3957 /* Return true if the graph is too expensive to optimize. PASS is the
3958 optimization about to be performed. */
3961 gcse_or_cprop_is_too_expensive (const char *pass
)
3963 unsigned HOST_WIDE_INT memory_request
3964 = ((unsigned HOST_WIDE_INT
)n_basic_blocks_for_fn (cfun
)
3965 * SBITMAP_SET_SIZE (max_reg_num ()) * sizeof (SBITMAP_ELT_TYPE
));
3967 /* Trying to perform global optimizations on flow graphs which have
3968 a high connectivity will take a long time and is unlikely to be
3969 particularly useful.
3971 In normal circumstances a cfg should have about twice as many
3972 edges as blocks. But we do not want to punish small functions
3973 which have a couple switch statements. Rather than simply
3974 threshold the number of blocks, uses something with a more
3975 graceful degradation. */
3976 if (n_edges_for_fn (cfun
) > 20000 + n_basic_blocks_for_fn (cfun
) * 4)
3978 warning (OPT_Wdisabled_optimization
,
3979 "%s: %d basic blocks and %d edges/basic block",
3980 pass
, n_basic_blocks_for_fn (cfun
),
3981 n_edges_for_fn (cfun
) / n_basic_blocks_for_fn (cfun
));
3986 /* If allocating memory for the dataflow bitmaps would take up too much
3987 storage it's better just to disable the optimization. */
3988 if (memory_request
/ 1024 > (unsigned HOST_WIDE_INT
)param_max_gcse_memory
)
3990 warning (OPT_Wdisabled_optimization
,
3991 "%s: %d basic blocks and %d registers; "
3992 "increase %<--param max-gcse-memory%> above %wu",
3993 pass
, n_basic_blocks_for_fn (cfun
), max_reg_num (),
3994 memory_request
/ 1024);
4003 execute_rtl_pre (void)
4006 delete_unreachable_blocks ();
4008 changed
= one_pre_gcse_pass ();
4009 flag_rerun_cse_after_global_opts
|= changed
;
4016 execute_rtl_hoist (void)
4019 delete_unreachable_blocks ();
4021 changed
= one_code_hoisting_pass ();
4022 flag_rerun_cse_after_global_opts
|= changed
;
4030 const pass_data pass_data_rtl_pre
=
4032 RTL_PASS
, /* type */
4033 "rtl pre", /* name */
4034 OPTGROUP_NONE
, /* optinfo_flags */
4036 PROP_cfglayout
, /* properties_required */
4037 0, /* properties_provided */
4038 0, /* properties_destroyed */
4039 0, /* todo_flags_start */
4040 TODO_df_finish
, /* todo_flags_finish */
4043 class pass_rtl_pre
: public rtl_opt_pass
4046 pass_rtl_pre (gcc::context
*ctxt
)
4047 : rtl_opt_pass (pass_data_rtl_pre
, ctxt
)
4050 /* opt_pass methods: */
4051 virtual bool gate (function
*);
4052 virtual unsigned int execute (function
*) { return execute_rtl_pre (); }
4054 }; // class pass_rtl_pre
4056 /* We do not construct an accurate cfg in functions which call
4057 setjmp, so none of these passes runs if the function calls
4059 FIXME: Should just handle setjmp via REG_SETJMP notes. */
4062 pass_rtl_pre::gate (function
*fun
)
4064 return optimize
> 0 && flag_gcse
4065 && !fun
->calls_setjmp
4066 && optimize_function_for_speed_p (fun
)
4073 make_pass_rtl_pre (gcc::context
*ctxt
)
4075 return new pass_rtl_pre (ctxt
);
4080 const pass_data pass_data_rtl_hoist
=
4082 RTL_PASS
, /* type */
4084 OPTGROUP_NONE
, /* optinfo_flags */
4085 TV_HOIST
, /* tv_id */
4086 PROP_cfglayout
, /* properties_required */
4087 0, /* properties_provided */
4088 0, /* properties_destroyed */
4089 0, /* todo_flags_start */
4090 TODO_df_finish
, /* todo_flags_finish */
4093 class pass_rtl_hoist
: public rtl_opt_pass
4096 pass_rtl_hoist (gcc::context
*ctxt
)
4097 : rtl_opt_pass (pass_data_rtl_hoist
, ctxt
)
4100 /* opt_pass methods: */
4101 virtual bool gate (function
*);
4102 virtual unsigned int execute (function
*) { return execute_rtl_hoist (); }
4104 }; // class pass_rtl_hoist
4107 pass_rtl_hoist::gate (function
*)
4109 return optimize
> 0 && flag_gcse
4110 && !cfun
->calls_setjmp
4111 /* It does not make sense to run code hoisting unless we are optimizing
4112 for code size -- it rarely makes programs faster, and can make then
4113 bigger if we did PRE (when optimizing for space, we don't run PRE). */
4114 && optimize_function_for_size_p (cfun
)
4121 make_pass_rtl_hoist (gcc::context
*ctxt
)
4123 return new pass_rtl_hoist (ctxt
);
4126 /* Reset all state within gcse.c so that we can rerun the compiler
4127 within the same process. For use by toplev::finalize. */
4130 gcse_c_finalize (void)
4135 #include "gt-gcse.h"