1 /* Optimization of PHI nodes by converting them into straightline code.
2 Copyright (C) 2004-2015 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it
7 under the terms of the GNU General Public License as published by the
8 Free Software Foundation; either version 3, or (at your option) any
11 GCC is distributed in the hope that it will be useful, but WITHOUT
12 ANY 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/>. */
22 #include "coretypes.h"
27 #include "fold-const.h"
28 #include "stor-layout.h"
32 #include "hard-reg-set.h"
34 #include "dominance.h"
37 #include "basic-block.h"
38 #include "tree-ssa-alias.h"
39 #include "internal-fn.h"
40 #include "gimple-expr.h"
43 #include "gimple-iterator.h"
44 #include "gimplify-me.h"
45 #include "gimple-ssa.h"
47 #include "tree-phinodes.h"
48 #include "ssa-iterators.h"
49 #include "stringpool.h"
50 #include "tree-ssanames.h"
52 #include "insn-config.h"
62 #include "tree-pass.h"
63 #include "langhooks.h"
66 #include "tree-data-ref.h"
67 #include "gimple-pretty-print.h"
68 #include "insn-codes.h"
70 #include "tree-scalar-evolution.h"
71 #include "tree-inline.h"
73 static unsigned int tree_ssa_phiopt_worker (bool, bool);
74 static bool conditional_replacement (basic_block
, basic_block
,
75 edge
, edge
, gphi
*, tree
, tree
);
76 static int value_replacement (basic_block
, basic_block
,
77 edge
, edge
, gimple
, tree
, tree
);
78 static bool minmax_replacement (basic_block
, basic_block
,
79 edge
, edge
, gimple
, tree
, tree
);
80 static bool abs_replacement (basic_block
, basic_block
,
81 edge
, edge
, gimple
, tree
, tree
);
82 static bool cond_store_replacement (basic_block
, basic_block
, edge
, edge
,
84 static bool cond_if_else_store_replacement (basic_block
, basic_block
, basic_block
);
85 static hash_set
<tree
> * get_non_trapping ();
86 static void replace_phi_edge_with_variable (basic_block
, edge
, gimple
, tree
);
87 static void hoist_adjacent_loads (basic_block
, basic_block
,
88 basic_block
, basic_block
);
89 static bool gate_hoist_loads (void);
91 /* This pass tries to transform conditional stores into unconditional
92 ones, enabling further simplifications with the simpler then and else
93 blocks. In particular it replaces this:
96 if (cond) goto bb2; else goto bb1;
104 if (cond) goto bb1; else goto bb2;
108 condtmp = PHI <RHS, condtmp'>
111 This transformation can only be done under several constraints,
112 documented below. It also replaces:
115 if (cond) goto bb2; else goto bb1;
126 if (cond) goto bb3; else goto bb1;
129 condtmp = PHI <RHS1, RHS2>
133 tree_ssa_cs_elim (void)
136 /* ??? We are not interested in loop related info, but the following
137 will create it, ICEing as we didn't init loops with pre-headers.
138 An interfacing issue of find_data_references_in_bb. */
139 loop_optimizer_init (LOOPS_NORMAL
);
141 todo
= tree_ssa_phiopt_worker (true, false);
143 loop_optimizer_finalize ();
147 /* Return the singleton PHI in the SEQ of PHIs for edges E0 and E1. */
150 single_non_singleton_phi_for_edges (gimple_seq seq
, edge e0
, edge e1
)
152 gimple_stmt_iterator i
;
154 if (gimple_seq_singleton_p (seq
))
155 return as_a
<gphi
*> (gsi_stmt (gsi_start (seq
)));
156 for (i
= gsi_start (seq
); !gsi_end_p (i
); gsi_next (&i
))
158 gphi
*p
= as_a
<gphi
*> (gsi_stmt (i
));
159 /* If the PHI arguments are equal then we can skip this PHI. */
160 if (operand_equal_for_phi_arg_p (gimple_phi_arg_def (p
, e0
->dest_idx
),
161 gimple_phi_arg_def (p
, e1
->dest_idx
)))
164 /* If we already have a PHI that has the two edge arguments are
165 different, then return it is not a singleton for these PHIs. */
174 /* The core routine of conditional store replacement and normal
175 phi optimizations. Both share much of the infrastructure in how
176 to match applicable basic block patterns. DO_STORE_ELIM is true
177 when we want to do conditional store replacement, false otherwise.
178 DO_HOIST_LOADS is true when we want to hoist adjacent loads out
179 of diamond control flow patterns, false otherwise. */
181 tree_ssa_phiopt_worker (bool do_store_elim
, bool do_hoist_loads
)
184 basic_block
*bb_order
;
186 bool cfgchanged
= false;
187 hash_set
<tree
> *nontrap
= 0;
190 /* Calculate the set of non-trapping memory accesses. */
191 nontrap
= get_non_trapping ();
193 /* Search every basic block for COND_EXPR we may be able to optimize.
195 We walk the blocks in order that guarantees that a block with
196 a single predecessor is processed before the predecessor.
197 This ensures that we collapse inner ifs before visiting the
198 outer ones, and also that we do not try to visit a removed
200 bb_order
= single_pred_before_succ_order ();
201 n
= n_basic_blocks_for_fn (cfun
) - NUM_FIXED_BLOCKS
;
203 for (i
= 0; i
< n
; i
++)
207 basic_block bb1
, bb2
;
213 cond_stmt
= last_stmt (bb
);
214 /* Check to see if the last statement is a GIMPLE_COND. */
216 || gimple_code (cond_stmt
) != GIMPLE_COND
)
219 e1
= EDGE_SUCC (bb
, 0);
221 e2
= EDGE_SUCC (bb
, 1);
224 /* We cannot do the optimization on abnormal edges. */
225 if ((e1
->flags
& EDGE_ABNORMAL
) != 0
226 || (e2
->flags
& EDGE_ABNORMAL
) != 0)
229 /* If either bb1's succ or bb2 or bb2's succ is non NULL. */
230 if (EDGE_COUNT (bb1
->succs
) == 0
232 || EDGE_COUNT (bb2
->succs
) == 0)
235 /* Find the bb which is the fall through to the other. */
236 if (EDGE_SUCC (bb1
, 0)->dest
== bb2
)
238 else if (EDGE_SUCC (bb2
, 0)->dest
== bb1
)
240 basic_block bb_tmp
= bb1
;
247 else if (do_store_elim
248 && EDGE_SUCC (bb1
, 0)->dest
== EDGE_SUCC (bb2
, 0)->dest
)
250 basic_block bb3
= EDGE_SUCC (bb1
, 0)->dest
;
252 if (!single_succ_p (bb1
)
253 || (EDGE_SUCC (bb1
, 0)->flags
& EDGE_FALLTHRU
) == 0
254 || !single_succ_p (bb2
)
255 || (EDGE_SUCC (bb2
, 0)->flags
& EDGE_FALLTHRU
) == 0
256 || EDGE_COUNT (bb3
->preds
) != 2)
258 if (cond_if_else_store_replacement (bb1
, bb2
, bb3
))
262 else if (do_hoist_loads
263 && EDGE_SUCC (bb1
, 0)->dest
== EDGE_SUCC (bb2
, 0)->dest
)
265 basic_block bb3
= EDGE_SUCC (bb1
, 0)->dest
;
267 if (!FLOAT_TYPE_P (TREE_TYPE (gimple_cond_lhs (cond_stmt
)))
268 && single_succ_p (bb1
)
269 && single_succ_p (bb2
)
270 && single_pred_p (bb1
)
271 && single_pred_p (bb2
)
272 && EDGE_COUNT (bb
->succs
) == 2
273 && EDGE_COUNT (bb3
->preds
) == 2
274 /* If one edge or the other is dominant, a conditional move
275 is likely to perform worse than the well-predicted branch. */
276 && !predictable_edge_p (EDGE_SUCC (bb
, 0))
277 && !predictable_edge_p (EDGE_SUCC (bb
, 1)))
278 hoist_adjacent_loads (bb
, bb1
, bb2
, bb3
);
284 e1
= EDGE_SUCC (bb1
, 0);
286 /* Make sure that bb1 is just a fall through. */
287 if (!single_succ_p (bb1
)
288 || (e1
->flags
& EDGE_FALLTHRU
) == 0)
291 /* Also make sure that bb1 only have one predecessor and that it
293 if (!single_pred_p (bb1
)
294 || single_pred (bb1
) != bb
)
299 /* bb1 is the middle block, bb2 the join block, bb the split block,
300 e1 the fallthrough edge from bb1 to bb2. We can't do the
301 optimization if the join block has more than two predecessors. */
302 if (EDGE_COUNT (bb2
->preds
) > 2)
304 if (cond_store_replacement (bb1
, bb2
, e1
, e2
, nontrap
))
309 gimple_seq phis
= phi_nodes (bb2
);
310 gimple_stmt_iterator gsi
;
311 bool candorest
= true;
313 /* Value replacement can work with more than one PHI
314 so try that first. */
315 for (gsi
= gsi_start (phis
); !gsi_end_p (gsi
); gsi_next (&gsi
))
317 phi
= as_a
<gphi
*> (gsi_stmt (gsi
));
318 arg0
= gimple_phi_arg_def (phi
, e1
->dest_idx
);
319 arg1
= gimple_phi_arg_def (phi
, e2
->dest_idx
);
320 if (value_replacement (bb
, bb1
, e1
, e2
, phi
, arg0
, arg1
) == 2)
331 phi
= single_non_singleton_phi_for_edges (phis
, e1
, e2
);
335 arg0
= gimple_phi_arg_def (phi
, e1
->dest_idx
);
336 arg1
= gimple_phi_arg_def (phi
, e2
->dest_idx
);
338 /* Something is wrong if we cannot find the arguments in the PHI
340 gcc_assert (arg0
!= NULL
&& arg1
!= NULL
);
342 /* Do the replacement of conditional if it can be done. */
343 if (conditional_replacement (bb
, bb1
, e1
, e2
, phi
, arg0
, arg1
))
345 else if (abs_replacement (bb
, bb1
, e1
, e2
, phi
, arg0
, arg1
))
347 else if (minmax_replacement (bb
, bb1
, e1
, e2
, phi
, arg0
, arg1
))
356 /* If the CFG has changed, we should cleanup the CFG. */
357 if (cfgchanged
&& do_store_elim
)
359 /* In cond-store replacement we have added some loads on edges
360 and new VOPS (as we moved the store, and created a load). */
361 gsi_commit_edge_inserts ();
362 return TODO_cleanup_cfg
| TODO_update_ssa_only_virtuals
;
365 return TODO_cleanup_cfg
;
369 /* Replace PHI node element whose edge is E in block BB with variable NEW.
370 Remove the edge from COND_BLOCK which does not lead to BB (COND_BLOCK
371 is known to have two edges, one of which must reach BB). */
374 replace_phi_edge_with_variable (basic_block cond_block
,
375 edge e
, gimple phi
, tree new_tree
)
377 basic_block bb
= gimple_bb (phi
);
378 basic_block block_to_remove
;
379 gimple_stmt_iterator gsi
;
381 /* Change the PHI argument to new. */
382 SET_USE (PHI_ARG_DEF_PTR (phi
, e
->dest_idx
), new_tree
);
384 /* Remove the empty basic block. */
385 if (EDGE_SUCC (cond_block
, 0)->dest
== bb
)
387 EDGE_SUCC (cond_block
, 0)->flags
|= EDGE_FALLTHRU
;
388 EDGE_SUCC (cond_block
, 0)->flags
&= ~(EDGE_TRUE_VALUE
| EDGE_FALSE_VALUE
);
389 EDGE_SUCC (cond_block
, 0)->probability
= REG_BR_PROB_BASE
;
390 EDGE_SUCC (cond_block
, 0)->count
+= EDGE_SUCC (cond_block
, 1)->count
;
392 block_to_remove
= EDGE_SUCC (cond_block
, 1)->dest
;
396 EDGE_SUCC (cond_block
, 1)->flags
|= EDGE_FALLTHRU
;
397 EDGE_SUCC (cond_block
, 1)->flags
398 &= ~(EDGE_TRUE_VALUE
| EDGE_FALSE_VALUE
);
399 EDGE_SUCC (cond_block
, 1)->probability
= REG_BR_PROB_BASE
;
400 EDGE_SUCC (cond_block
, 1)->count
+= EDGE_SUCC (cond_block
, 0)->count
;
402 block_to_remove
= EDGE_SUCC (cond_block
, 0)->dest
;
404 delete_basic_block (block_to_remove
);
406 /* Eliminate the COND_EXPR at the end of COND_BLOCK. */
407 gsi
= gsi_last_bb (cond_block
);
408 gsi_remove (&gsi
, true);
410 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
412 "COND_EXPR in block %d and PHI in block %d converted to straightline code.\n",
417 /* The function conditional_replacement does the main work of doing the
418 conditional replacement. Return true if the replacement is done.
419 Otherwise return false.
420 BB is the basic block where the replacement is going to be done on. ARG0
421 is argument 0 from PHI. Likewise for ARG1. */
424 conditional_replacement (basic_block cond_bb
, basic_block middle_bb
,
425 edge e0
, edge e1
, gphi
*phi
,
426 tree arg0
, tree arg1
)
432 gimple_stmt_iterator gsi
;
433 edge true_edge
, false_edge
;
434 tree new_var
, new_var2
;
437 /* FIXME: Gimplification of complex type is too hard for now. */
438 /* We aren't prepared to handle vectors either (and it is a question
439 if it would be worthwhile anyway). */
440 if (!(INTEGRAL_TYPE_P (TREE_TYPE (arg0
))
441 || POINTER_TYPE_P (TREE_TYPE (arg0
)))
442 || !(INTEGRAL_TYPE_P (TREE_TYPE (arg1
))
443 || POINTER_TYPE_P (TREE_TYPE (arg1
))))
446 /* The PHI arguments have the constants 0 and 1, or 0 and -1, then
447 convert it to the conditional. */
448 if ((integer_zerop (arg0
) && integer_onep (arg1
))
449 || (integer_zerop (arg1
) && integer_onep (arg0
)))
451 else if ((integer_zerop (arg0
) && integer_all_onesp (arg1
))
452 || (integer_zerop (arg1
) && integer_all_onesp (arg0
)))
457 if (!empty_block_p (middle_bb
))
460 /* At this point we know we have a GIMPLE_COND with two successors.
461 One successor is BB, the other successor is an empty block which
462 falls through into BB.
464 There is a single PHI node at the join point (BB) and its arguments
465 are constants (0, 1) or (0, -1).
467 So, given the condition COND, and the two PHI arguments, we can
468 rewrite this PHI into non-branching code:
470 dest = (COND) or dest = COND'
472 We use the condition as-is if the argument associated with the
473 true edge has the value one or the argument associated with the
474 false edge as the value zero. Note that those conditions are not
475 the same since only one of the outgoing edges from the GIMPLE_COND
476 will directly reach BB and thus be associated with an argument. */
478 stmt
= last_stmt (cond_bb
);
479 result
= PHI_RESULT (phi
);
481 /* To handle special cases like floating point comparison, it is easier and
482 less error-prone to build a tree and gimplify it on the fly though it is
484 cond
= fold_build2_loc (gimple_location (stmt
),
485 gimple_cond_code (stmt
), boolean_type_node
,
486 gimple_cond_lhs (stmt
), gimple_cond_rhs (stmt
));
488 /* We need to know which is the true edge and which is the false
489 edge so that we know when to invert the condition below. */
490 extract_true_false_edges_from_block (cond_bb
, &true_edge
, &false_edge
);
491 if ((e0
== true_edge
&& integer_zerop (arg0
))
492 || (e0
== false_edge
&& !integer_zerop (arg0
))
493 || (e1
== true_edge
&& integer_zerop (arg1
))
494 || (e1
== false_edge
&& !integer_zerop (arg1
)))
495 cond
= fold_build1_loc (gimple_location (stmt
),
496 TRUTH_NOT_EXPR
, TREE_TYPE (cond
), cond
);
500 cond
= fold_convert_loc (gimple_location (stmt
),
501 TREE_TYPE (result
), cond
);
502 cond
= fold_build1_loc (gimple_location (stmt
),
503 NEGATE_EXPR
, TREE_TYPE (cond
), cond
);
506 /* Insert our new statements at the end of conditional block before the
508 gsi
= gsi_for_stmt (stmt
);
509 new_var
= force_gimple_operand_gsi (&gsi
, cond
, true, NULL
, true,
512 if (!useless_type_conversion_p (TREE_TYPE (result
), TREE_TYPE (new_var
)))
514 source_location locus_0
, locus_1
;
516 new_var2
= make_ssa_name (TREE_TYPE (result
));
517 new_stmt
= gimple_build_assign (new_var2
, CONVERT_EXPR
, new_var
);
518 gsi_insert_before (&gsi
, new_stmt
, GSI_SAME_STMT
);
521 /* Set the locus to the first argument, unless is doesn't have one. */
522 locus_0
= gimple_phi_arg_location (phi
, 0);
523 locus_1
= gimple_phi_arg_location (phi
, 1);
524 if (locus_0
== UNKNOWN_LOCATION
)
526 gimple_set_location (new_stmt
, locus_0
);
529 replace_phi_edge_with_variable (cond_bb
, e1
, phi
, new_var
);
531 /* Note that we optimized this PHI. */
535 /* Update *ARG which is defined in STMT so that it contains the
536 computed value if that seems profitable. Return true if the
537 statement is made dead by that rewriting. */
540 jump_function_from_stmt (tree
*arg
, gimple stmt
)
542 enum tree_code code
= gimple_assign_rhs_code (stmt
);
543 if (code
== ADDR_EXPR
)
545 /* For arg = &p->i transform it to p, if possible. */
546 tree rhs1
= gimple_assign_rhs1 (stmt
);
547 HOST_WIDE_INT offset
;
548 tree tem
= get_addr_base_and_unit_offset (TREE_OPERAND (rhs1
, 0),
551 && TREE_CODE (tem
) == MEM_REF
552 && (mem_ref_offset (tem
) + offset
) == 0)
554 *arg
= TREE_OPERAND (tem
, 0);
558 /* TODO: Much like IPA-CP jump-functions we want to handle constant
559 additions symbolically here, and we'd need to update the comparison
560 code that compares the arg + cst tuples in our caller. For now the
561 code above exactly handles the VEC_BASE pattern from vec.h. */
565 /* RHS is a source argument in a BIT_AND_EXPR which feeds a conditional
566 of the form SSA_NAME NE 0.
568 If RHS is fed by a simple EQ_EXPR comparison of two values, see if
569 the two input values of the EQ_EXPR match arg0 and arg1.
571 If so update *code and return TRUE. Otherwise return FALSE. */
574 rhs_is_fed_for_value_replacement (const_tree arg0
, const_tree arg1
,
575 enum tree_code
*code
, const_tree rhs
)
577 /* Obviously if RHS is not an SSA_NAME, we can't look at the defining
579 if (TREE_CODE (rhs
) == SSA_NAME
)
581 gimple def1
= SSA_NAME_DEF_STMT (rhs
);
583 /* Verify the defining statement has an EQ_EXPR on the RHS. */
584 if (is_gimple_assign (def1
) && gimple_assign_rhs_code (def1
) == EQ_EXPR
)
586 /* Finally verify the source operands of the EQ_EXPR are equal
588 tree op0
= gimple_assign_rhs1 (def1
);
589 tree op1
= gimple_assign_rhs2 (def1
);
590 if ((operand_equal_for_phi_arg_p (arg0
, op0
)
591 && operand_equal_for_phi_arg_p (arg1
, op1
))
592 || (operand_equal_for_phi_arg_p (arg0
, op1
)
593 && operand_equal_for_phi_arg_p (arg1
, op0
)))
595 /* We will perform the optimization. */
596 *code
= gimple_assign_rhs_code (def1
);
604 /* Return TRUE if arg0/arg1 are equal to the rhs/lhs or lhs/rhs of COND.
606 Also return TRUE if arg0/arg1 are equal to the source arguments of a
607 an EQ comparison feeding a BIT_AND_EXPR which feeds COND.
609 Return FALSE otherwise. */
612 operand_equal_for_value_replacement (const_tree arg0
, const_tree arg1
,
613 enum tree_code
*code
, gimple cond
)
616 tree lhs
= gimple_cond_lhs (cond
);
617 tree rhs
= gimple_cond_rhs (cond
);
619 if ((operand_equal_for_phi_arg_p (arg0
, lhs
)
620 && operand_equal_for_phi_arg_p (arg1
, rhs
))
621 || (operand_equal_for_phi_arg_p (arg1
, lhs
)
622 && operand_equal_for_phi_arg_p (arg0
, rhs
)))
625 /* Now handle more complex case where we have an EQ comparison
626 which feeds a BIT_AND_EXPR which feeds COND.
628 First verify that COND is of the form SSA_NAME NE 0. */
629 if (*code
!= NE_EXPR
|| !integer_zerop (rhs
)
630 || TREE_CODE (lhs
) != SSA_NAME
)
633 /* Now ensure that SSA_NAME is set by a BIT_AND_EXPR. */
634 def
= SSA_NAME_DEF_STMT (lhs
);
635 if (!is_gimple_assign (def
) || gimple_assign_rhs_code (def
) != BIT_AND_EXPR
)
638 /* Now verify arg0/arg1 correspond to the source arguments of an
639 EQ comparison feeding the BIT_AND_EXPR. */
641 tree tmp
= gimple_assign_rhs1 (def
);
642 if (rhs_is_fed_for_value_replacement (arg0
, arg1
, code
, tmp
))
645 tmp
= gimple_assign_rhs2 (def
);
646 if (rhs_is_fed_for_value_replacement (arg0
, arg1
, code
, tmp
))
652 /* Returns true if ARG is a neutral element for operation CODE
653 on the RIGHT side. */
656 neutral_element_p (tree_code code
, tree arg
, bool right
)
663 return integer_zerop (arg
);
670 case POINTER_PLUS_EXPR
:
671 return right
&& integer_zerop (arg
);
674 return integer_onep (arg
);
681 return right
&& integer_onep (arg
);
684 return integer_all_onesp (arg
);
691 /* Returns true if ARG is an absorbing element for operation CODE. */
694 absorbing_element_p (tree_code code
, tree arg
)
699 return integer_all_onesp (arg
);
703 return integer_zerop (arg
);
710 /* The function value_replacement does the main work of doing the value
711 replacement. Return non-zero if the replacement is done. Otherwise return
712 0. If we remove the middle basic block, return 2.
713 BB is the basic block where the replacement is going to be done on. ARG0
714 is argument 0 from the PHI. Likewise for ARG1. */
717 value_replacement (basic_block cond_bb
, basic_block middle_bb
,
718 edge e0
, edge e1
, gimple phi
,
719 tree arg0
, tree arg1
)
721 gimple_stmt_iterator gsi
;
723 edge true_edge
, false_edge
;
725 bool emtpy_or_with_defined_p
= true;
727 /* If the type says honor signed zeros we cannot do this
729 if (HONOR_SIGNED_ZEROS (arg1
))
732 /* If there is a statement in MIDDLE_BB that defines one of the PHI
733 arguments, then adjust arg0 or arg1. */
734 gsi
= gsi_start_nondebug_after_labels_bb (middle_bb
);
735 while (!gsi_end_p (gsi
))
737 gimple stmt
= gsi_stmt (gsi
);
739 gsi_next_nondebug (&gsi
);
740 if (!is_gimple_assign (stmt
))
742 emtpy_or_with_defined_p
= false;
745 /* Now try to adjust arg0 or arg1 according to the computation
747 lhs
= gimple_assign_lhs (stmt
);
749 && jump_function_from_stmt (&arg0
, stmt
))
751 && jump_function_from_stmt (&arg1
, stmt
)))
752 emtpy_or_with_defined_p
= false;
755 cond
= last_stmt (cond_bb
);
756 code
= gimple_cond_code (cond
);
758 /* This transformation is only valid for equality comparisons. */
759 if (code
!= NE_EXPR
&& code
!= EQ_EXPR
)
762 /* We need to know which is the true edge and which is the false
763 edge so that we know if have abs or negative abs. */
764 extract_true_false_edges_from_block (cond_bb
, &true_edge
, &false_edge
);
766 /* At this point we know we have a COND_EXPR with two successors.
767 One successor is BB, the other successor is an empty block which
768 falls through into BB.
770 The condition for the COND_EXPR is known to be NE_EXPR or EQ_EXPR.
772 There is a single PHI node at the join point (BB) with two arguments.
774 We now need to verify that the two arguments in the PHI node match
775 the two arguments to the equality comparison. */
777 if (operand_equal_for_value_replacement (arg0
, arg1
, &code
, cond
))
782 /* For NE_EXPR, we want to build an assignment result = arg where
783 arg is the PHI argument associated with the true edge. For
784 EQ_EXPR we want the PHI argument associated with the false edge. */
785 e
= (code
== NE_EXPR
? true_edge
: false_edge
);
787 /* Unfortunately, E may not reach BB (it may instead have gone to
788 OTHER_BLOCK). If that is the case, then we want the single outgoing
789 edge from OTHER_BLOCK which reaches BB and represents the desired
790 path from COND_BLOCK. */
791 if (e
->dest
== middle_bb
)
792 e
= single_succ_edge (e
->dest
);
794 /* Now we know the incoming edge to BB that has the argument for the
795 RHS of our new assignment statement. */
801 /* If the middle basic block was empty or is defining the
802 PHI arguments and this is a single phi where the args are different
803 for the edges e0 and e1 then we can remove the middle basic block. */
804 if (emtpy_or_with_defined_p
805 && single_non_singleton_phi_for_edges (phi_nodes (gimple_bb (phi
)),
808 replace_phi_edge_with_variable (cond_bb
, e1
, phi
, arg
);
809 /* Note that we optimized this PHI. */
814 /* Replace the PHI arguments with arg. */
815 SET_PHI_ARG_DEF (phi
, e0
->dest_idx
, arg
);
816 SET_PHI_ARG_DEF (phi
, e1
->dest_idx
, arg
);
817 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
819 fprintf (dump_file
, "PHI ");
820 print_generic_expr (dump_file
, gimple_phi_result (phi
), 0);
821 fprintf (dump_file
, " reduced for COND_EXPR in block %d to ",
823 print_generic_expr (dump_file
, arg
, 0);
824 fprintf (dump_file
, ".\n");
831 /* Now optimize (x != 0) ? x + y : y to just y.
832 The following condition is too restrictive, there can easily be another
833 stmt in middle_bb, for instance a CONVERT_EXPR for the second argument. */
834 gimple assign
= last_and_only_stmt (middle_bb
);
835 if (!assign
|| gimple_code (assign
) != GIMPLE_ASSIGN
836 || gimple_assign_rhs_class (assign
) != GIMPLE_BINARY_RHS
837 || (!INTEGRAL_TYPE_P (TREE_TYPE (arg0
))
838 && !POINTER_TYPE_P (TREE_TYPE (arg0
))))
841 /* Punt if there are (degenerate) PHIs in middle_bb, there should not be. */
842 if (!gimple_seq_empty_p (phi_nodes (middle_bb
)))
845 /* Only transform if it removes the condition. */
846 if (!single_non_singleton_phi_for_edges (phi_nodes (gimple_bb (phi
)), e0
, e1
))
849 /* Size-wise, this is always profitable. */
850 if (optimize_bb_for_speed_p (cond_bb
)
851 /* The special case is useless if it has a low probability. */
852 && profile_status_for_fn (cfun
) != PROFILE_ABSENT
853 && EDGE_PRED (middle_bb
, 0)->probability
< PROB_EVEN
854 /* If assign is cheap, there is no point avoiding it. */
855 && estimate_num_insns (assign
, &eni_time_weights
)
856 >= 3 * estimate_num_insns (cond
, &eni_time_weights
))
859 tree lhs
= gimple_assign_lhs (assign
);
860 tree rhs1
= gimple_assign_rhs1 (assign
);
861 tree rhs2
= gimple_assign_rhs2 (assign
);
862 enum tree_code code_def
= gimple_assign_rhs_code (assign
);
863 tree cond_lhs
= gimple_cond_lhs (cond
);
864 tree cond_rhs
= gimple_cond_rhs (cond
);
866 if (((code
== NE_EXPR
&& e1
== false_edge
)
867 || (code
== EQ_EXPR
&& e1
== true_edge
))
870 && operand_equal_for_phi_arg_p (rhs2
, cond_lhs
)
871 && neutral_element_p (code_def
, cond_rhs
, true))
873 && operand_equal_for_phi_arg_p (rhs1
, cond_lhs
)
874 && neutral_element_p (code_def
, cond_rhs
, false))
875 || (operand_equal_for_phi_arg_p (arg1
, cond_rhs
)
876 && (operand_equal_for_phi_arg_p (rhs2
, cond_lhs
)
877 || operand_equal_for_phi_arg_p (rhs1
, cond_lhs
))
878 && absorbing_element_p (code_def
, cond_rhs
))))
880 gsi
= gsi_for_stmt (cond
);
881 if (INTEGRAL_TYPE_P (TREE_TYPE (lhs
)))
883 /* Moving ASSIGN might change VR of lhs, e.g. when moving u_6
891 # RANGE [0, 4294967294]
892 u_6 = n_5 + 4294967295;
895 # u_3 = PHI <u_6(3), 4294967295(2)> */
896 SSA_NAME_RANGE_INFO (lhs
) = NULL
;
897 SSA_NAME_ANTI_RANGE_P (lhs
) = 0;
898 /* If available, we can use VR of phi result at least. */
899 tree phires
= gimple_phi_result (phi
);
900 struct range_info_def
*phires_range_info
901 = SSA_NAME_RANGE_INFO (phires
);
902 if (phires_range_info
)
903 duplicate_ssa_name_range_info (lhs
, SSA_NAME_RANGE_TYPE (phires
),
906 gimple_stmt_iterator gsi_from
= gsi_for_stmt (assign
);
907 gsi_move_before (&gsi_from
, &gsi
);
908 replace_phi_edge_with_variable (cond_bb
, e1
, phi
, lhs
);
915 /* The function minmax_replacement does the main work of doing the minmax
916 replacement. Return true if the replacement is done. Otherwise return
918 BB is the basic block where the replacement is going to be done on. ARG0
919 is argument 0 from the PHI. Likewise for ARG1. */
922 minmax_replacement (basic_block cond_bb
, basic_block middle_bb
,
923 edge e0
, edge e1
, gimple phi
,
924 tree arg0
, tree arg1
)
929 edge true_edge
, false_edge
;
930 enum tree_code cmp
, minmax
, ass_code
;
931 tree smaller
, larger
, arg_true
, arg_false
;
932 gimple_stmt_iterator gsi
, gsi_from
;
934 type
= TREE_TYPE (PHI_RESULT (phi
));
936 /* The optimization may be unsafe due to NaNs. */
937 if (HONOR_NANS (type
))
940 cond
= as_a
<gcond
*> (last_stmt (cond_bb
));
941 cmp
= gimple_cond_code (cond
);
943 /* This transformation is only valid for order comparisons. Record which
944 operand is smaller/larger if the result of the comparison is true. */
945 if (cmp
== LT_EXPR
|| cmp
== LE_EXPR
)
947 smaller
= gimple_cond_lhs (cond
);
948 larger
= gimple_cond_rhs (cond
);
950 else if (cmp
== GT_EXPR
|| cmp
== GE_EXPR
)
952 smaller
= gimple_cond_rhs (cond
);
953 larger
= gimple_cond_lhs (cond
);
958 /* We need to know which is the true edge and which is the false
959 edge so that we know if have abs or negative abs. */
960 extract_true_false_edges_from_block (cond_bb
, &true_edge
, &false_edge
);
962 /* Forward the edges over the middle basic block. */
963 if (true_edge
->dest
== middle_bb
)
964 true_edge
= EDGE_SUCC (true_edge
->dest
, 0);
965 if (false_edge
->dest
== middle_bb
)
966 false_edge
= EDGE_SUCC (false_edge
->dest
, 0);
970 gcc_assert (false_edge
== e1
);
976 gcc_assert (false_edge
== e0
);
977 gcc_assert (true_edge
== e1
);
982 if (empty_block_p (middle_bb
))
984 if (operand_equal_for_phi_arg_p (arg_true
, smaller
)
985 && operand_equal_for_phi_arg_p (arg_false
, larger
))
989 if (smaller < larger)
995 else if (operand_equal_for_phi_arg_p (arg_false
, smaller
)
996 && operand_equal_for_phi_arg_p (arg_true
, larger
))
1003 /* Recognize the following case, assuming d <= u:
1009 This is equivalent to
1014 gimple assign
= last_and_only_stmt (middle_bb
);
1015 tree lhs
, op0
, op1
, bound
;
1018 || gimple_code (assign
) != GIMPLE_ASSIGN
)
1021 lhs
= gimple_assign_lhs (assign
);
1022 ass_code
= gimple_assign_rhs_code (assign
);
1023 if (ass_code
!= MAX_EXPR
&& ass_code
!= MIN_EXPR
)
1025 op0
= gimple_assign_rhs1 (assign
);
1026 op1
= gimple_assign_rhs2 (assign
);
1028 if (true_edge
->src
== middle_bb
)
1030 /* We got here if the condition is true, i.e., SMALLER < LARGER. */
1031 if (!operand_equal_for_phi_arg_p (lhs
, arg_true
))
1034 if (operand_equal_for_phi_arg_p (arg_false
, larger
))
1038 if (smaller < larger)
1040 r' = MAX_EXPR (smaller, bound)
1042 r = PHI <r', larger> --> to be turned to MIN_EXPR. */
1043 if (ass_code
!= MAX_EXPR
)
1047 if (operand_equal_for_phi_arg_p (op0
, smaller
))
1049 else if (operand_equal_for_phi_arg_p (op1
, smaller
))
1054 /* We need BOUND <= LARGER. */
1055 if (!integer_nonzerop (fold_build2 (LE_EXPR
, boolean_type_node
,
1059 else if (operand_equal_for_phi_arg_p (arg_false
, smaller
))
1063 if (smaller < larger)
1065 r' = MIN_EXPR (larger, bound)
1067 r = PHI <r', smaller> --> to be turned to MAX_EXPR. */
1068 if (ass_code
!= MIN_EXPR
)
1072 if (operand_equal_for_phi_arg_p (op0
, larger
))
1074 else if (operand_equal_for_phi_arg_p (op1
, larger
))
1079 /* We need BOUND >= SMALLER. */
1080 if (!integer_nonzerop (fold_build2 (GE_EXPR
, boolean_type_node
,
1089 /* We got here if the condition is false, i.e., SMALLER > LARGER. */
1090 if (!operand_equal_for_phi_arg_p (lhs
, arg_false
))
1093 if (operand_equal_for_phi_arg_p (arg_true
, larger
))
1097 if (smaller > larger)
1099 r' = MIN_EXPR (smaller, bound)
1101 r = PHI <r', larger> --> to be turned to MAX_EXPR. */
1102 if (ass_code
!= MIN_EXPR
)
1106 if (operand_equal_for_phi_arg_p (op0
, smaller
))
1108 else if (operand_equal_for_phi_arg_p (op1
, smaller
))
1113 /* We need BOUND >= LARGER. */
1114 if (!integer_nonzerop (fold_build2 (GE_EXPR
, boolean_type_node
,
1118 else if (operand_equal_for_phi_arg_p (arg_true
, smaller
))
1122 if (smaller > larger)
1124 r' = MAX_EXPR (larger, bound)
1126 r = PHI <r', smaller> --> to be turned to MIN_EXPR. */
1127 if (ass_code
!= MAX_EXPR
)
1131 if (operand_equal_for_phi_arg_p (op0
, larger
))
1133 else if (operand_equal_for_phi_arg_p (op1
, larger
))
1138 /* We need BOUND <= SMALLER. */
1139 if (!integer_nonzerop (fold_build2 (LE_EXPR
, boolean_type_node
,
1147 /* Move the statement from the middle block. */
1148 gsi
= gsi_last_bb (cond_bb
);
1149 gsi_from
= gsi_last_nondebug_bb (middle_bb
);
1150 gsi_move_before (&gsi_from
, &gsi
);
1153 /* Emit the statement to compute min/max. */
1154 result
= duplicate_ssa_name (PHI_RESULT (phi
), NULL
);
1155 new_stmt
= gimple_build_assign (result
, minmax
, arg0
, arg1
);
1156 gsi
= gsi_last_bb (cond_bb
);
1157 gsi_insert_before (&gsi
, new_stmt
, GSI_NEW_STMT
);
1159 replace_phi_edge_with_variable (cond_bb
, e1
, phi
, result
);
1163 /* The function absolute_replacement does the main work of doing the absolute
1164 replacement. Return true if the replacement is done. Otherwise return
1166 bb is the basic block where the replacement is going to be done on. arg0
1167 is argument 0 from the phi. Likewise for arg1. */
1170 abs_replacement (basic_block cond_bb
, basic_block middle_bb
,
1171 edge e0 ATTRIBUTE_UNUSED
, edge e1
,
1172 gimple phi
, tree arg0
, tree arg1
)
1177 gimple_stmt_iterator gsi
;
1178 edge true_edge
, false_edge
;
1183 enum tree_code cond_code
;
1185 /* If the type says honor signed zeros we cannot do this
1187 if (HONOR_SIGNED_ZEROS (arg1
))
1190 /* OTHER_BLOCK must have only one executable statement which must have the
1191 form arg0 = -arg1 or arg1 = -arg0. */
1193 assign
= last_and_only_stmt (middle_bb
);
1194 /* If we did not find the proper negation assignment, then we can not
1199 /* If we got here, then we have found the only executable statement
1200 in OTHER_BLOCK. If it is anything other than arg = -arg1 or
1201 arg1 = -arg0, then we can not optimize. */
1202 if (gimple_code (assign
) != GIMPLE_ASSIGN
)
1205 lhs
= gimple_assign_lhs (assign
);
1207 if (gimple_assign_rhs_code (assign
) != NEGATE_EXPR
)
1210 rhs
= gimple_assign_rhs1 (assign
);
1212 /* The assignment has to be arg0 = -arg1 or arg1 = -arg0. */
1213 if (!(lhs
== arg0
&& rhs
== arg1
)
1214 && !(lhs
== arg1
&& rhs
== arg0
))
1217 cond
= last_stmt (cond_bb
);
1218 result
= PHI_RESULT (phi
);
1220 /* Only relationals comparing arg[01] against zero are interesting. */
1221 cond_code
= gimple_cond_code (cond
);
1222 if (cond_code
!= GT_EXPR
&& cond_code
!= GE_EXPR
1223 && cond_code
!= LT_EXPR
&& cond_code
!= LE_EXPR
)
1226 /* Make sure the conditional is arg[01] OP y. */
1227 if (gimple_cond_lhs (cond
) != rhs
)
1230 if (FLOAT_TYPE_P (TREE_TYPE (gimple_cond_rhs (cond
)))
1231 ? real_zerop (gimple_cond_rhs (cond
))
1232 : integer_zerop (gimple_cond_rhs (cond
)))
1237 /* We need to know which is the true edge and which is the false
1238 edge so that we know if have abs or negative abs. */
1239 extract_true_false_edges_from_block (cond_bb
, &true_edge
, &false_edge
);
1241 /* For GT_EXPR/GE_EXPR, if the true edge goes to OTHER_BLOCK, then we
1242 will need to negate the result. Similarly for LT_EXPR/LE_EXPR if
1243 the false edge goes to OTHER_BLOCK. */
1244 if (cond_code
== GT_EXPR
|| cond_code
== GE_EXPR
)
1249 if (e
->dest
== middle_bb
)
1254 result
= duplicate_ssa_name (result
, NULL
);
1257 lhs
= make_ssa_name (TREE_TYPE (result
));
1261 /* Build the modify expression with abs expression. */
1262 new_stmt
= gimple_build_assign (lhs
, ABS_EXPR
, rhs
);
1264 gsi
= gsi_last_bb (cond_bb
);
1265 gsi_insert_before (&gsi
, new_stmt
, GSI_NEW_STMT
);
1269 /* Get the right GSI. We want to insert after the recently
1270 added ABS_EXPR statement (which we know is the first statement
1272 new_stmt
= gimple_build_assign (result
, NEGATE_EXPR
, lhs
);
1274 gsi_insert_after (&gsi
, new_stmt
, GSI_NEW_STMT
);
1277 replace_phi_edge_with_variable (cond_bb
, e1
, phi
, result
);
1279 /* Note that we optimized this PHI. */
1283 /* Auxiliary functions to determine the set of memory accesses which
1284 can't trap because they are preceded by accesses to the same memory
1285 portion. We do that for MEM_REFs, so we only need to track
1286 the SSA_NAME of the pointer indirectly referenced. The algorithm
1287 simply is a walk over all instructions in dominator order. When
1288 we see an MEM_REF we determine if we've already seen a same
1289 ref anywhere up to the root of the dominator tree. If we do the
1290 current access can't trap. If we don't see any dominating access
1291 the current access might trap, but might also make later accesses
1292 non-trapping, so we remember it. We need to be careful with loads
1293 or stores, for instance a load might not trap, while a store would,
1294 so if we see a dominating read access this doesn't mean that a later
1295 write access would not trap. Hence we also need to differentiate the
1296 type of access(es) seen.
1298 ??? We currently are very conservative and assume that a load might
1299 trap even if a store doesn't (write-only memory). This probably is
1300 overly conservative. */
1302 /* A hash-table of SSA_NAMEs, and in which basic block an MEM_REF
1303 through it was seen, which would constitute a no-trap region for
1307 unsigned int ssa_name_ver
;
1310 HOST_WIDE_INT offset
, size
;
1314 /* Hashtable helpers. */
1316 struct ssa_names_hasher
: typed_free_remove
<name_to_bb
>
1318 typedef name_to_bb
*value_type
;
1319 typedef name_to_bb
*compare_type
;
1320 static inline hashval_t
hash (const name_to_bb
*);
1321 static inline bool equal (const name_to_bb
*, const name_to_bb
*);
1324 /* Used for quick clearing of the hash-table when we see calls.
1325 Hash entries with phase < nt_call_phase are invalid. */
1326 static unsigned int nt_call_phase
;
1328 /* The hash function. */
1331 ssa_names_hasher::hash (const name_to_bb
*n
)
1333 return n
->ssa_name_ver
^ (((hashval_t
) n
->store
) << 31)
1334 ^ (n
->offset
<< 6) ^ (n
->size
<< 3);
1337 /* The equality function of *P1 and *P2. */
1340 ssa_names_hasher::equal (const name_to_bb
*n1
, const name_to_bb
*n2
)
1342 return n1
->ssa_name_ver
== n2
->ssa_name_ver
1343 && n1
->store
== n2
->store
1344 && n1
->offset
== n2
->offset
1345 && n1
->size
== n2
->size
;
1348 class nontrapping_dom_walker
: public dom_walker
1351 nontrapping_dom_walker (cdi_direction direction
, hash_set
<tree
> *ps
)
1352 : dom_walker (direction
), m_nontrapping (ps
), m_seen_ssa_names (128) {}
1354 virtual void before_dom_children (basic_block
);
1355 virtual void after_dom_children (basic_block
);
1359 /* We see the expression EXP in basic block BB. If it's an interesting
1360 expression (an MEM_REF through an SSA_NAME) possibly insert the
1361 expression into the set NONTRAP or the hash table of seen expressions.
1362 STORE is true if this expression is on the LHS, otherwise it's on
1364 void add_or_mark_expr (basic_block
, tree
, bool);
1366 hash_set
<tree
> *m_nontrapping
;
1368 /* The hash table for remembering what we've seen. */
1369 hash_table
<ssa_names_hasher
> m_seen_ssa_names
;
1372 /* Called by walk_dominator_tree, when entering the block BB. */
1374 nontrapping_dom_walker::before_dom_children (basic_block bb
)
1378 gimple_stmt_iterator gsi
;
1380 /* If we haven't seen all our predecessors, clear the hash-table. */
1381 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1382 if ((((size_t)e
->src
->aux
) & 2) == 0)
1388 /* Mark this BB as being on the path to dominator root and as visited. */
1389 bb
->aux
= (void*)(1 | 2);
1391 /* And walk the statements in order. */
1392 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1394 gimple stmt
= gsi_stmt (gsi
);
1396 if (is_gimple_call (stmt
) && !nonfreeing_call_p (stmt
))
1398 else if (gimple_assign_single_p (stmt
) && !gimple_has_volatile_ops (stmt
))
1400 add_or_mark_expr (bb
, gimple_assign_lhs (stmt
), true);
1401 add_or_mark_expr (bb
, gimple_assign_rhs1 (stmt
), false);
1406 /* Called by walk_dominator_tree, when basic block BB is exited. */
1408 nontrapping_dom_walker::after_dom_children (basic_block bb
)
1410 /* This BB isn't on the path to dominator root anymore. */
1414 /* We see the expression EXP in basic block BB. If it's an interesting
1415 expression (an MEM_REF through an SSA_NAME) possibly insert the
1416 expression into the set NONTRAP or the hash table of seen expressions.
1417 STORE is true if this expression is on the LHS, otherwise it's on
1420 nontrapping_dom_walker::add_or_mark_expr (basic_block bb
, tree exp
, bool store
)
1424 if (TREE_CODE (exp
) == MEM_REF
1425 && TREE_CODE (TREE_OPERAND (exp
, 0)) == SSA_NAME
1426 && tree_fits_shwi_p (TREE_OPERAND (exp
, 1))
1427 && (size
= int_size_in_bytes (TREE_TYPE (exp
))) > 0)
1429 tree name
= TREE_OPERAND (exp
, 0);
1430 struct name_to_bb map
;
1432 struct name_to_bb
*n2bb
;
1433 basic_block found_bb
= 0;
1435 /* Try to find the last seen MEM_REF through the same
1436 SSA_NAME, which can trap. */
1437 map
.ssa_name_ver
= SSA_NAME_VERSION (name
);
1441 map
.offset
= tree_to_shwi (TREE_OPERAND (exp
, 1));
1444 slot
= m_seen_ssa_names
.find_slot (&map
, INSERT
);
1446 if (n2bb
&& n2bb
->phase
>= nt_call_phase
)
1447 found_bb
= n2bb
->bb
;
1449 /* If we've found a trapping MEM_REF, _and_ it dominates EXP
1450 (it's in a basic block on the path from us to the dominator root)
1451 then we can't trap. */
1452 if (found_bb
&& (((size_t)found_bb
->aux
) & 1) == 1)
1454 m_nontrapping
->add (exp
);
1458 /* EXP might trap, so insert it into the hash table. */
1461 n2bb
->phase
= nt_call_phase
;
1466 n2bb
= XNEW (struct name_to_bb
);
1467 n2bb
->ssa_name_ver
= SSA_NAME_VERSION (name
);
1468 n2bb
->phase
= nt_call_phase
;
1470 n2bb
->store
= store
;
1471 n2bb
->offset
= map
.offset
;
1479 /* This is the entry point of gathering non trapping memory accesses.
1480 It will do a dominator walk over the whole function, and it will
1481 make use of the bb->aux pointers. It returns a set of trees
1482 (the MEM_REFs itself) which can't trap. */
1483 static hash_set
<tree
> *
1484 get_non_trapping (void)
1487 hash_set
<tree
> *nontrap
= new hash_set
<tree
>;
1488 /* We're going to do a dominator walk, so ensure that we have
1489 dominance information. */
1490 calculate_dominance_info (CDI_DOMINATORS
);
1492 nontrapping_dom_walker (CDI_DOMINATORS
, nontrap
)
1493 .walk (cfun
->cfg
->x_entry_block_ptr
);
1495 clear_aux_for_blocks ();
1499 /* Do the main work of conditional store replacement. We already know
1500 that the recognized pattern looks like so:
1503 if (cond) goto MIDDLE_BB; else goto JOIN_BB (edge E1)
1506 fallthrough (edge E0)
1510 We check that MIDDLE_BB contains only one store, that that store
1511 doesn't trap (not via NOTRAP, but via checking if an access to the same
1512 memory location dominates us) and that the store has a "simple" RHS. */
1515 cond_store_replacement (basic_block middle_bb
, basic_block join_bb
,
1516 edge e0
, edge e1
, hash_set
<tree
> *nontrap
)
1518 gimple assign
= last_and_only_stmt (middle_bb
);
1519 tree lhs
, rhs
, name
, name2
;
1522 gimple_stmt_iterator gsi
;
1523 source_location locus
;
1525 /* Check if middle_bb contains of only one store. */
1527 || !gimple_assign_single_p (assign
)
1528 || gimple_has_volatile_ops (assign
))
1531 locus
= gimple_location (assign
);
1532 lhs
= gimple_assign_lhs (assign
);
1533 rhs
= gimple_assign_rhs1 (assign
);
1534 if (TREE_CODE (lhs
) != MEM_REF
1535 || TREE_CODE (TREE_OPERAND (lhs
, 0)) != SSA_NAME
1536 || !is_gimple_reg_type (TREE_TYPE (lhs
)))
1539 /* Prove that we can move the store down. We could also check
1540 TREE_THIS_NOTRAP here, but in that case we also could move stores,
1541 whose value is not available readily, which we want to avoid. */
1542 if (!nontrap
->contains (lhs
))
1545 /* Now we've checked the constraints, so do the transformation:
1546 1) Remove the single store. */
1547 gsi
= gsi_for_stmt (assign
);
1548 unlink_stmt_vdef (assign
);
1549 gsi_remove (&gsi
, true);
1550 release_defs (assign
);
1552 /* 2) Insert a load from the memory of the store to the temporary
1553 on the edge which did not contain the store. */
1554 lhs
= unshare_expr (lhs
);
1555 name
= make_temp_ssa_name (TREE_TYPE (lhs
), NULL
, "cstore");
1556 new_stmt
= gimple_build_assign (name
, lhs
);
1557 gimple_set_location (new_stmt
, locus
);
1558 gsi_insert_on_edge (e1
, new_stmt
);
1560 /* 3) Create a PHI node at the join block, with one argument
1561 holding the old RHS, and the other holding the temporary
1562 where we stored the old memory contents. */
1563 name2
= make_temp_ssa_name (TREE_TYPE (lhs
), NULL
, "cstore");
1564 newphi
= create_phi_node (name2
, join_bb
);
1565 add_phi_arg (newphi
, rhs
, e0
, locus
);
1566 add_phi_arg (newphi
, name
, e1
, locus
);
1568 lhs
= unshare_expr (lhs
);
1569 new_stmt
= gimple_build_assign (lhs
, PHI_RESULT (newphi
));
1571 /* 4) Insert that PHI node. */
1572 gsi
= gsi_after_labels (join_bb
);
1573 if (gsi_end_p (gsi
))
1575 gsi
= gsi_last_bb (join_bb
);
1576 gsi_insert_after (&gsi
, new_stmt
, GSI_NEW_STMT
);
1579 gsi_insert_before (&gsi
, new_stmt
, GSI_NEW_STMT
);
1584 /* Do the main work of conditional store replacement. */
1587 cond_if_else_store_replacement_1 (basic_block then_bb
, basic_block else_bb
,
1588 basic_block join_bb
, gimple then_assign
,
1591 tree lhs_base
, lhs
, then_rhs
, else_rhs
, name
;
1592 source_location then_locus
, else_locus
;
1593 gimple_stmt_iterator gsi
;
1597 if (then_assign
== NULL
1598 || !gimple_assign_single_p (then_assign
)
1599 || gimple_clobber_p (then_assign
)
1600 || gimple_has_volatile_ops (then_assign
)
1601 || else_assign
== NULL
1602 || !gimple_assign_single_p (else_assign
)
1603 || gimple_clobber_p (else_assign
)
1604 || gimple_has_volatile_ops (else_assign
))
1607 lhs
= gimple_assign_lhs (then_assign
);
1608 if (!is_gimple_reg_type (TREE_TYPE (lhs
))
1609 || !operand_equal_p (lhs
, gimple_assign_lhs (else_assign
), 0))
1612 lhs_base
= get_base_address (lhs
);
1613 if (lhs_base
== NULL_TREE
1614 || (!DECL_P (lhs_base
) && TREE_CODE (lhs_base
) != MEM_REF
))
1617 then_rhs
= gimple_assign_rhs1 (then_assign
);
1618 else_rhs
= gimple_assign_rhs1 (else_assign
);
1619 then_locus
= gimple_location (then_assign
);
1620 else_locus
= gimple_location (else_assign
);
1622 /* Now we've checked the constraints, so do the transformation:
1623 1) Remove the stores. */
1624 gsi
= gsi_for_stmt (then_assign
);
1625 unlink_stmt_vdef (then_assign
);
1626 gsi_remove (&gsi
, true);
1627 release_defs (then_assign
);
1629 gsi
= gsi_for_stmt (else_assign
);
1630 unlink_stmt_vdef (else_assign
);
1631 gsi_remove (&gsi
, true);
1632 release_defs (else_assign
);
1634 /* 2) Create a PHI node at the join block, with one argument
1635 holding the old RHS, and the other holding the temporary
1636 where we stored the old memory contents. */
1637 name
= make_temp_ssa_name (TREE_TYPE (lhs
), NULL
, "cstore");
1638 newphi
= create_phi_node (name
, join_bb
);
1639 add_phi_arg (newphi
, then_rhs
, EDGE_SUCC (then_bb
, 0), then_locus
);
1640 add_phi_arg (newphi
, else_rhs
, EDGE_SUCC (else_bb
, 0), else_locus
);
1642 new_stmt
= gimple_build_assign (lhs
, PHI_RESULT (newphi
));
1644 /* 3) Insert that PHI node. */
1645 gsi
= gsi_after_labels (join_bb
);
1646 if (gsi_end_p (gsi
))
1648 gsi
= gsi_last_bb (join_bb
);
1649 gsi_insert_after (&gsi
, new_stmt
, GSI_NEW_STMT
);
1652 gsi_insert_before (&gsi
, new_stmt
, GSI_NEW_STMT
);
1657 /* Conditional store replacement. We already know
1658 that the recognized pattern looks like so:
1661 if (cond) goto THEN_BB; else goto ELSE_BB (edge E1)
1671 fallthrough (edge E0)
1675 We check that it is safe to sink the store to JOIN_BB by verifying that
1676 there are no read-after-write or write-after-write dependencies in
1677 THEN_BB and ELSE_BB. */
1680 cond_if_else_store_replacement (basic_block then_bb
, basic_block else_bb
,
1681 basic_block join_bb
)
1683 gimple then_assign
= last_and_only_stmt (then_bb
);
1684 gimple else_assign
= last_and_only_stmt (else_bb
);
1685 vec
<data_reference_p
> then_datarefs
, else_datarefs
;
1686 vec
<ddr_p
> then_ddrs
, else_ddrs
;
1687 gimple then_store
, else_store
;
1688 bool found
, ok
= false, res
;
1689 struct data_dependence_relation
*ddr
;
1690 data_reference_p then_dr
, else_dr
;
1692 tree then_lhs
, else_lhs
;
1693 basic_block blocks
[3];
1695 if (MAX_STORES_TO_SINK
== 0)
1698 /* Handle the case with single statement in THEN_BB and ELSE_BB. */
1699 if (then_assign
&& else_assign
)
1700 return cond_if_else_store_replacement_1 (then_bb
, else_bb
, join_bb
,
1701 then_assign
, else_assign
);
1703 /* Find data references. */
1704 then_datarefs
.create (1);
1705 else_datarefs
.create (1);
1706 if ((find_data_references_in_bb (NULL
, then_bb
, &then_datarefs
)
1708 || !then_datarefs
.length ()
1709 || (find_data_references_in_bb (NULL
, else_bb
, &else_datarefs
)
1711 || !else_datarefs
.length ())
1713 free_data_refs (then_datarefs
);
1714 free_data_refs (else_datarefs
);
1718 /* Find pairs of stores with equal LHS. */
1719 auto_vec
<gimple
, 1> then_stores
, else_stores
;
1720 FOR_EACH_VEC_ELT (then_datarefs
, i
, then_dr
)
1722 if (DR_IS_READ (then_dr
))
1725 then_store
= DR_STMT (then_dr
);
1726 then_lhs
= gimple_get_lhs (then_store
);
1727 if (then_lhs
== NULL_TREE
)
1731 FOR_EACH_VEC_ELT (else_datarefs
, j
, else_dr
)
1733 if (DR_IS_READ (else_dr
))
1736 else_store
= DR_STMT (else_dr
);
1737 else_lhs
= gimple_get_lhs (else_store
);
1738 if (else_lhs
== NULL_TREE
)
1741 if (operand_equal_p (then_lhs
, else_lhs
, 0))
1751 then_stores
.safe_push (then_store
);
1752 else_stores
.safe_push (else_store
);
1755 /* No pairs of stores found. */
1756 if (!then_stores
.length ()
1757 || then_stores
.length () > (unsigned) MAX_STORES_TO_SINK
)
1759 free_data_refs (then_datarefs
);
1760 free_data_refs (else_datarefs
);
1764 /* Compute and check data dependencies in both basic blocks. */
1765 then_ddrs
.create (1);
1766 else_ddrs
.create (1);
1767 if (!compute_all_dependences (then_datarefs
, &then_ddrs
,
1769 || !compute_all_dependences (else_datarefs
, &else_ddrs
,
1772 free_dependence_relations (then_ddrs
);
1773 free_dependence_relations (else_ddrs
);
1774 free_data_refs (then_datarefs
);
1775 free_data_refs (else_datarefs
);
1778 blocks
[0] = then_bb
;
1779 blocks
[1] = else_bb
;
1780 blocks
[2] = join_bb
;
1781 renumber_gimple_stmt_uids_in_blocks (blocks
, 3);
1783 /* Check that there are no read-after-write or write-after-write dependencies
1785 FOR_EACH_VEC_ELT (then_ddrs
, i
, ddr
)
1787 struct data_reference
*dra
= DDR_A (ddr
);
1788 struct data_reference
*drb
= DDR_B (ddr
);
1790 if (DDR_ARE_DEPENDENT (ddr
) != chrec_known
1791 && ((DR_IS_READ (dra
) && DR_IS_WRITE (drb
)
1792 && gimple_uid (DR_STMT (dra
)) > gimple_uid (DR_STMT (drb
)))
1793 || (DR_IS_READ (drb
) && DR_IS_WRITE (dra
)
1794 && gimple_uid (DR_STMT (drb
)) > gimple_uid (DR_STMT (dra
)))
1795 || (DR_IS_WRITE (dra
) && DR_IS_WRITE (drb
))))
1797 free_dependence_relations (then_ddrs
);
1798 free_dependence_relations (else_ddrs
);
1799 free_data_refs (then_datarefs
);
1800 free_data_refs (else_datarefs
);
1805 /* Check that there are no read-after-write or write-after-write dependencies
1807 FOR_EACH_VEC_ELT (else_ddrs
, i
, ddr
)
1809 struct data_reference
*dra
= DDR_A (ddr
);
1810 struct data_reference
*drb
= DDR_B (ddr
);
1812 if (DDR_ARE_DEPENDENT (ddr
) != chrec_known
1813 && ((DR_IS_READ (dra
) && DR_IS_WRITE (drb
)
1814 && gimple_uid (DR_STMT (dra
)) > gimple_uid (DR_STMT (drb
)))
1815 || (DR_IS_READ (drb
) && DR_IS_WRITE (dra
)
1816 && gimple_uid (DR_STMT (drb
)) > gimple_uid (DR_STMT (dra
)))
1817 || (DR_IS_WRITE (dra
) && DR_IS_WRITE (drb
))))
1819 free_dependence_relations (then_ddrs
);
1820 free_dependence_relations (else_ddrs
);
1821 free_data_refs (then_datarefs
);
1822 free_data_refs (else_datarefs
);
1827 /* Sink stores with same LHS. */
1828 FOR_EACH_VEC_ELT (then_stores
, i
, then_store
)
1830 else_store
= else_stores
[i
];
1831 res
= cond_if_else_store_replacement_1 (then_bb
, else_bb
, join_bb
,
1832 then_store
, else_store
);
1836 free_dependence_relations (then_ddrs
);
1837 free_dependence_relations (else_ddrs
);
1838 free_data_refs (then_datarefs
);
1839 free_data_refs (else_datarefs
);
1844 /* Return TRUE if STMT has a VUSE whose corresponding VDEF is in BB. */
1847 local_mem_dependence (gimple stmt
, basic_block bb
)
1849 tree vuse
= gimple_vuse (stmt
);
1855 def
= SSA_NAME_DEF_STMT (vuse
);
1856 return (def
&& gimple_bb (def
) == bb
);
1859 /* Given a "diamond" control-flow pattern where BB0 tests a condition,
1860 BB1 and BB2 are "then" and "else" blocks dependent on this test,
1861 and BB3 rejoins control flow following BB1 and BB2, look for
1862 opportunities to hoist loads as follows. If BB3 contains a PHI of
1863 two loads, one each occurring in BB1 and BB2, and the loads are
1864 provably of adjacent fields in the same structure, then move both
1865 loads into BB0. Of course this can only be done if there are no
1866 dependencies preventing such motion.
1868 One of the hoisted loads will always be speculative, so the
1869 transformation is currently conservative:
1871 - The fields must be strictly adjacent.
1872 - The two fields must occupy a single memory block that is
1873 guaranteed to not cross a page boundary.
1875 The last is difficult to prove, as such memory blocks should be
1876 aligned on the minimum of the stack alignment boundary and the
1877 alignment guaranteed by heap allocation interfaces. Thus we rely
1878 on a parameter for the alignment value.
1880 Provided a good value is used for the last case, the first
1881 restriction could possibly be relaxed. */
1884 hoist_adjacent_loads (basic_block bb0
, basic_block bb1
,
1885 basic_block bb2
, basic_block bb3
)
1887 int param_align
= PARAM_VALUE (PARAM_L1_CACHE_LINE_SIZE
);
1888 unsigned param_align_bits
= (unsigned) (param_align
* BITS_PER_UNIT
);
1891 /* Walk the phis in bb3 looking for an opportunity. We are looking
1892 for phis of two SSA names, one each of which is defined in bb1 and
1894 for (gsi
= gsi_start_phis (bb3
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1896 gphi
*phi_stmt
= gsi
.phi ();
1898 tree arg1
, arg2
, ref1
, ref2
, field1
, field2
;
1899 tree tree_offset1
, tree_offset2
, tree_size2
, next
;
1900 int offset1
, offset2
, size2
;
1902 gimple_stmt_iterator gsi2
;
1903 basic_block bb_for_def1
, bb_for_def2
;
1905 if (gimple_phi_num_args (phi_stmt
) != 2
1906 || virtual_operand_p (gimple_phi_result (phi_stmt
)))
1909 arg1
= gimple_phi_arg_def (phi_stmt
, 0);
1910 arg2
= gimple_phi_arg_def (phi_stmt
, 1);
1912 if (TREE_CODE (arg1
) != SSA_NAME
1913 || TREE_CODE (arg2
) != SSA_NAME
1914 || SSA_NAME_IS_DEFAULT_DEF (arg1
)
1915 || SSA_NAME_IS_DEFAULT_DEF (arg2
))
1918 def1
= SSA_NAME_DEF_STMT (arg1
);
1919 def2
= SSA_NAME_DEF_STMT (arg2
);
1921 if ((gimple_bb (def1
) != bb1
|| gimple_bb (def2
) != bb2
)
1922 && (gimple_bb (def2
) != bb1
|| gimple_bb (def1
) != bb2
))
1925 /* Check the mode of the arguments to be sure a conditional move
1926 can be generated for it. */
1927 if (optab_handler (movcc_optab
, TYPE_MODE (TREE_TYPE (arg1
)))
1928 == CODE_FOR_nothing
)
1931 /* Both statements must be assignments whose RHS is a COMPONENT_REF. */
1932 if (!gimple_assign_single_p (def1
)
1933 || !gimple_assign_single_p (def2
)
1934 || gimple_has_volatile_ops (def1
)
1935 || gimple_has_volatile_ops (def2
))
1938 ref1
= gimple_assign_rhs1 (def1
);
1939 ref2
= gimple_assign_rhs1 (def2
);
1941 if (TREE_CODE (ref1
) != COMPONENT_REF
1942 || TREE_CODE (ref2
) != COMPONENT_REF
)
1945 /* The zeroth operand of the two component references must be
1946 identical. It is not sufficient to compare get_base_address of
1947 the two references, because this could allow for different
1948 elements of the same array in the two trees. It is not safe to
1949 assume that the existence of one array element implies the
1950 existence of a different one. */
1951 if (!operand_equal_p (TREE_OPERAND (ref1
, 0), TREE_OPERAND (ref2
, 0), 0))
1954 field1
= TREE_OPERAND (ref1
, 1);
1955 field2
= TREE_OPERAND (ref2
, 1);
1957 /* Check for field adjacency, and ensure field1 comes first. */
1958 for (next
= DECL_CHAIN (field1
);
1959 next
&& TREE_CODE (next
) != FIELD_DECL
;
1960 next
= DECL_CHAIN (next
))
1965 for (next
= DECL_CHAIN (field2
);
1966 next
&& TREE_CODE (next
) != FIELD_DECL
;
1967 next
= DECL_CHAIN (next
))
1973 std::swap (field1
, field2
);
1974 std::swap (def1
, def2
);
1977 bb_for_def1
= gimple_bb (def1
);
1978 bb_for_def2
= gimple_bb (def2
);
1980 /* Check for proper alignment of the first field. */
1981 tree_offset1
= bit_position (field1
);
1982 tree_offset2
= bit_position (field2
);
1983 tree_size2
= DECL_SIZE (field2
);
1985 if (!tree_fits_uhwi_p (tree_offset1
)
1986 || !tree_fits_uhwi_p (tree_offset2
)
1987 || !tree_fits_uhwi_p (tree_size2
))
1990 offset1
= tree_to_uhwi (tree_offset1
);
1991 offset2
= tree_to_uhwi (tree_offset2
);
1992 size2
= tree_to_uhwi (tree_size2
);
1993 align1
= DECL_ALIGN (field1
) % param_align_bits
;
1995 if (offset1
% BITS_PER_UNIT
!= 0)
1998 /* For profitability, the two field references should fit within
1999 a single cache line. */
2000 if (align1
+ offset2
- offset1
+ size2
> param_align_bits
)
2003 /* The two expressions cannot be dependent upon vdefs defined
2005 if (local_mem_dependence (def1
, bb_for_def1
)
2006 || local_mem_dependence (def2
, bb_for_def2
))
2009 /* The conditions are satisfied; hoist the loads from bb1 and bb2 into
2010 bb0. We hoist the first one first so that a cache miss is handled
2011 efficiently regardless of hardware cache-fill policy. */
2012 gsi2
= gsi_for_stmt (def1
);
2013 gsi_move_to_bb_end (&gsi2
, bb0
);
2014 gsi2
= gsi_for_stmt (def2
);
2015 gsi_move_to_bb_end (&gsi2
, bb0
);
2017 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2020 "\nHoisting adjacent loads from %d and %d into %d: \n",
2021 bb_for_def1
->index
, bb_for_def2
->index
, bb0
->index
);
2022 print_gimple_stmt (dump_file
, def1
, 0, TDF_VOPS
|TDF_MEMSYMS
);
2023 print_gimple_stmt (dump_file
, def2
, 0, TDF_VOPS
|TDF_MEMSYMS
);
2028 /* Determine whether we should attempt to hoist adjacent loads out of
2029 diamond patterns in pass_phiopt. Always hoist loads if
2030 -fhoist-adjacent-loads is specified and the target machine has
2031 both a conditional move instruction and a defined cache line size. */
2034 gate_hoist_loads (void)
2036 return (flag_hoist_adjacent_loads
== 1
2037 && PARAM_VALUE (PARAM_L1_CACHE_LINE_SIZE
)
2038 && HAVE_conditional_move
);
2041 /* This pass tries to replaces an if-then-else block with an
2042 assignment. We have four kinds of transformations. Some of these
2043 transformations are also performed by the ifcvt RTL optimizer.
2045 Conditional Replacement
2046 -----------------------
2048 This transformation, implemented in conditional_replacement,
2052 if (cond) goto bb2; else goto bb1;
2055 x = PHI <0 (bb1), 1 (bb0), ...>;
2063 x = PHI <x' (bb0), ...>;
2065 We remove bb1 as it becomes unreachable. This occurs often due to
2066 gimplification of conditionals.
2071 This transformation, implemented in value_replacement, replaces
2074 if (a != b) goto bb2; else goto bb1;
2077 x = PHI <a (bb1), b (bb0), ...>;
2083 x = PHI <b (bb0), ...>;
2085 This opportunity can sometimes occur as a result of other
2089 Another case caught by value replacement looks like this:
2095 if (t3 != 0) goto bb1; else goto bb2;
2111 This transformation, implemented in abs_replacement, replaces
2114 if (a >= 0) goto bb2; else goto bb1;
2118 x = PHI <x (bb1), a (bb0), ...>;
2125 x = PHI <x' (bb0), ...>;
2130 This transformation, minmax_replacement replaces
2133 if (a <= b) goto bb2; else goto bb1;
2136 x = PHI <b (bb1), a (bb0), ...>;
2141 x' = MIN_EXPR (a, b)
2143 x = PHI <x' (bb0), ...>;
2145 A similar transformation is done for MAX_EXPR.
2148 This pass also performs a fifth transformation of a slightly different
2151 Adjacent Load Hoisting
2152 ----------------------
2154 This transformation replaces
2157 if (...) goto bb2; else goto bb1;
2159 x1 = (<expr>).field1;
2162 x2 = (<expr>).field2;
2169 x1 = (<expr>).field1;
2170 x2 = (<expr>).field2;
2171 if (...) goto bb2; else goto bb1;
2178 The purpose of this transformation is to enable generation of conditional
2179 move instructions such as Intel CMOVE or PowerPC ISEL. Because one of
2180 the loads is speculative, the transformation is restricted to very
2181 specific cases to avoid introducing a page fault. We are looking for
2189 where left and right are typically adjacent pointers in a tree structure. */
2193 const pass_data pass_data_phiopt
=
2195 GIMPLE_PASS
, /* type */
2196 "phiopt", /* name */
2197 OPTGROUP_NONE
, /* optinfo_flags */
2198 TV_TREE_PHIOPT
, /* tv_id */
2199 ( PROP_cfg
| PROP_ssa
), /* properties_required */
2200 0, /* properties_provided */
2201 0, /* properties_destroyed */
2202 0, /* todo_flags_start */
2203 0, /* todo_flags_finish */
2206 class pass_phiopt
: public gimple_opt_pass
2209 pass_phiopt (gcc::context
*ctxt
)
2210 : gimple_opt_pass (pass_data_phiopt
, ctxt
)
2213 /* opt_pass methods: */
2214 opt_pass
* clone () { return new pass_phiopt (m_ctxt
); }
2215 virtual bool gate (function
*) { return flag_ssa_phiopt
; }
2216 virtual unsigned int execute (function
*)
2218 return tree_ssa_phiopt_worker (false, gate_hoist_loads ());
2221 }; // class pass_phiopt
2226 make_pass_phiopt (gcc::context
*ctxt
)
2228 return new pass_phiopt (ctxt
);
2233 const pass_data pass_data_cselim
=
2235 GIMPLE_PASS
, /* type */
2236 "cselim", /* name */
2237 OPTGROUP_NONE
, /* optinfo_flags */
2238 TV_TREE_PHIOPT
, /* tv_id */
2239 ( PROP_cfg
| PROP_ssa
), /* properties_required */
2240 0, /* properties_provided */
2241 0, /* properties_destroyed */
2242 0, /* todo_flags_start */
2243 0, /* todo_flags_finish */
2246 class pass_cselim
: public gimple_opt_pass
2249 pass_cselim (gcc::context
*ctxt
)
2250 : gimple_opt_pass (pass_data_cselim
, ctxt
)
2253 /* opt_pass methods: */
2254 virtual bool gate (function
*) { return flag_tree_cselim
; }
2255 virtual unsigned int execute (function
*) { return tree_ssa_cs_elim (); }
2257 }; // class pass_cselim
2262 make_pass_cselim (gcc::context
*ctxt
)
2264 return new pass_cselim (ctxt
);