1 /* Optimization of PHI nodes by converting them into straightline code.
2 Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012
3 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it
8 under the terms of the GNU General Public License as published by the
9 Free Software Foundation; either version 3, or (at your option) any
12 GCC is distributed in the hope that it will be useful, but WITHOUT
13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
23 #include "coretypes.h"
29 #include "basic-block.h"
30 #include "tree-flow.h"
31 #include "tree-pass.h"
32 #include "langhooks.h"
33 #include "pointer-set.h"
36 #include "tree-data-ref.h"
37 #include "gimple-pretty-print.h"
38 #include "insn-config.h"
42 #ifndef HAVE_conditional_move
43 #define HAVE_conditional_move (0)
46 static unsigned int tree_ssa_phiopt (void);
47 static unsigned int tree_ssa_phiopt_worker (bool, bool);
48 static bool conditional_replacement (basic_block
, basic_block
,
49 edge
, edge
, gimple
, tree
, tree
);
50 static int value_replacement (basic_block
, basic_block
,
51 edge
, edge
, gimple
, tree
, tree
);
52 static bool minmax_replacement (basic_block
, basic_block
,
53 edge
, edge
, gimple
, tree
, tree
);
54 static bool abs_replacement (basic_block
, basic_block
,
55 edge
, edge
, gimple
, tree
, tree
);
56 static bool cond_store_replacement (basic_block
, basic_block
, edge
, edge
,
57 struct pointer_set_t
*);
58 static bool cond_if_else_store_replacement (basic_block
, basic_block
, basic_block
);
59 static struct pointer_set_t
* get_non_trapping (void);
60 static void replace_phi_edge_with_variable (basic_block
, edge
, gimple
, tree
);
61 static void hoist_adjacent_loads (basic_block
, basic_block
,
62 basic_block
, basic_block
);
63 static bool gate_hoist_loads (void);
65 /* This pass tries to replaces an if-then-else block with an
66 assignment. We have four kinds of transformations. Some of these
67 transformations are also performed by the ifcvt RTL optimizer.
69 Conditional Replacement
70 -----------------------
72 This transformation, implemented in conditional_replacement,
76 if (cond) goto bb2; else goto bb1;
79 x = PHI <0 (bb1), 1 (bb0), ...>;
87 x = PHI <x' (bb0), ...>;
89 We remove bb1 as it becomes unreachable. This occurs often due to
90 gimplification of conditionals.
95 This transformation, implemented in value_replacement, replaces
98 if (a != b) goto bb2; else goto bb1;
101 x = PHI <a (bb1), b (bb0), ...>;
107 x = PHI <b (bb0), ...>;
109 This opportunity can sometimes occur as a result of other
115 This transformation, implemented in abs_replacement, replaces
118 if (a >= 0) goto bb2; else goto bb1;
122 x = PHI <x (bb1), a (bb0), ...>;
129 x = PHI <x' (bb0), ...>;
134 This transformation, minmax_replacement replaces
137 if (a <= b) goto bb2; else goto bb1;
140 x = PHI <b (bb1), a (bb0), ...>;
147 x = PHI <x' (bb0), ...>;
149 A similar transformation is done for MAX_EXPR.
152 This pass also performs a fifth transformation of a slightly different
155 Adjacent Load Hoisting
156 ----------------------
158 This transformation replaces
161 if (...) goto bb2; else goto bb1;
163 x1 = (<expr>).field1;
166 x2 = (<expr>).field2;
173 x1 = (<expr>).field1;
174 x2 = (<expr>).field2;
175 if (...) goto bb2; else goto bb1;
182 The purpose of this transformation is to enable generation of conditional
183 move instructions such as Intel CMOVE or PowerPC ISEL. Because one of
184 the loads is speculative, the transformation is restricted to very
185 specific cases to avoid introducing a page fault. We are looking for
193 where left and right are typically adjacent pointers in a tree structure. */
196 tree_ssa_phiopt (void)
198 return tree_ssa_phiopt_worker (false, gate_hoist_loads ());
201 /* This pass tries to transform conditional stores into unconditional
202 ones, enabling further simplifications with the simpler then and else
203 blocks. In particular it replaces this:
206 if (cond) goto bb2; else goto bb1;
214 if (cond) goto bb1; else goto bb2;
218 condtmp = PHI <RHS, condtmp'>
221 This transformation can only be done under several constraints,
222 documented below. It also replaces:
225 if (cond) goto bb2; else goto bb1;
236 if (cond) goto bb3; else goto bb1;
239 condtmp = PHI <RHS1, RHS2>
243 tree_ssa_cs_elim (void)
245 return tree_ssa_phiopt_worker (true, false);
248 /* Return the singleton PHI in the SEQ of PHIs for edges E0 and E1. */
251 single_non_singleton_phi_for_edges (gimple_seq seq
, edge e0
, edge e1
)
253 gimple_stmt_iterator i
;
255 if (gimple_seq_singleton_p (seq
))
256 return gsi_stmt (gsi_start (seq
));
257 for (i
= gsi_start (seq
); !gsi_end_p (i
); gsi_next (&i
))
259 gimple p
= gsi_stmt (i
);
260 /* If the PHI arguments are equal then we can skip this PHI. */
261 if (operand_equal_for_phi_arg_p (gimple_phi_arg_def (p
, e0
->dest_idx
),
262 gimple_phi_arg_def (p
, e1
->dest_idx
)))
265 /* If we already have a PHI that has the two edge arguments are
266 different, then return it is not a singleton for these PHIs. */
275 /* The core routine of conditional store replacement and normal
276 phi optimizations. Both share much of the infrastructure in how
277 to match applicable basic block patterns. DO_STORE_ELIM is true
278 when we want to do conditional store replacement, false otherwise.
279 DO_HOIST_LOADS is true when we want to hoist adjacent loads out
280 of diamond control flow patterns, false otherwise. */
282 tree_ssa_phiopt_worker (bool do_store_elim
, bool do_hoist_loads
)
285 basic_block
*bb_order
;
287 bool cfgchanged
= false;
288 struct pointer_set_t
*nontrap
= 0;
291 /* Calculate the set of non-trapping memory accesses. */
292 nontrap
= get_non_trapping ();
294 /* Search every basic block for COND_EXPR we may be able to optimize.
296 We walk the blocks in order that guarantees that a block with
297 a single predecessor is processed before the predecessor.
298 This ensures that we collapse inner ifs before visiting the
299 outer ones, and also that we do not try to visit a removed
301 bb_order
= blocks_in_phiopt_order ();
302 n
= n_basic_blocks
- NUM_FIXED_BLOCKS
;
304 for (i
= 0; i
< n
; i
++)
306 gimple cond_stmt
, phi
;
307 basic_block bb1
, bb2
;
313 cond_stmt
= last_stmt (bb
);
314 /* Check to see if the last statement is a GIMPLE_COND. */
316 || gimple_code (cond_stmt
) != GIMPLE_COND
)
319 e1
= EDGE_SUCC (bb
, 0);
321 e2
= EDGE_SUCC (bb
, 1);
324 /* We cannot do the optimization on abnormal edges. */
325 if ((e1
->flags
& EDGE_ABNORMAL
) != 0
326 || (e2
->flags
& EDGE_ABNORMAL
) != 0)
329 /* If either bb1's succ or bb2 or bb2's succ is non NULL. */
330 if (EDGE_COUNT (bb1
->succs
) == 0
332 || EDGE_COUNT (bb2
->succs
) == 0)
335 /* Find the bb which is the fall through to the other. */
336 if (EDGE_SUCC (bb1
, 0)->dest
== bb2
)
338 else if (EDGE_SUCC (bb2
, 0)->dest
== bb1
)
340 basic_block bb_tmp
= bb1
;
347 else if (do_store_elim
348 && EDGE_SUCC (bb1
, 0)->dest
== EDGE_SUCC (bb2
, 0)->dest
)
350 basic_block bb3
= EDGE_SUCC (bb1
, 0)->dest
;
352 if (!single_succ_p (bb1
)
353 || (EDGE_SUCC (bb1
, 0)->flags
& EDGE_FALLTHRU
) == 0
354 || !single_succ_p (bb2
)
355 || (EDGE_SUCC (bb2
, 0)->flags
& EDGE_FALLTHRU
) == 0
356 || EDGE_COUNT (bb3
->preds
) != 2)
358 if (cond_if_else_store_replacement (bb1
, bb2
, bb3
))
362 else if (do_hoist_loads
363 && EDGE_SUCC (bb1
, 0)->dest
== EDGE_SUCC (bb2
, 0)->dest
)
365 basic_block bb3
= EDGE_SUCC (bb1
, 0)->dest
;
367 if (!FLOAT_TYPE_P (TREE_TYPE (gimple_cond_lhs (cond_stmt
)))
368 && single_succ_p (bb1
)
369 && single_succ_p (bb2
)
370 && single_pred_p (bb1
)
371 && single_pred_p (bb2
)
372 && EDGE_COUNT (bb
->succs
) == 2
373 && EDGE_COUNT (bb3
->preds
) == 2
374 /* If one edge or the other is dominant, a conditional move
375 is likely to perform worse than the well-predicted branch. */
376 && !predictable_edge_p (EDGE_SUCC (bb
, 0))
377 && !predictable_edge_p (EDGE_SUCC (bb
, 1)))
378 hoist_adjacent_loads (bb
, bb1
, bb2
, bb3
);
384 e1
= EDGE_SUCC (bb1
, 0);
386 /* Make sure that bb1 is just a fall through. */
387 if (!single_succ_p (bb1
)
388 || (e1
->flags
& EDGE_FALLTHRU
) == 0)
391 /* Also make sure that bb1 only have one predecessor and that it
393 if (!single_pred_p (bb1
)
394 || single_pred (bb1
) != bb
)
399 /* bb1 is the middle block, bb2 the join block, bb the split block,
400 e1 the fallthrough edge from bb1 to bb2. We can't do the
401 optimization if the join block has more than two predecessors. */
402 if (EDGE_COUNT (bb2
->preds
) > 2)
404 if (cond_store_replacement (bb1
, bb2
, e1
, e2
, nontrap
))
409 gimple_seq phis
= phi_nodes (bb2
);
410 gimple_stmt_iterator gsi
;
411 bool candorest
= true;
413 /* Value replacement can work with more than one PHI
414 so try that first. */
415 for (gsi
= gsi_start (phis
); !gsi_end_p (gsi
); gsi_next (&gsi
))
417 phi
= gsi_stmt (gsi
);
418 arg0
= gimple_phi_arg_def (phi
, e1
->dest_idx
);
419 arg1
= gimple_phi_arg_def (phi
, e2
->dest_idx
);
420 if (value_replacement (bb
, bb1
, e1
, e2
, phi
, arg0
, arg1
) == 2)
431 phi
= single_non_singleton_phi_for_edges (phis
, e1
, e2
);
435 arg0
= gimple_phi_arg_def (phi
, e1
->dest_idx
);
436 arg1
= gimple_phi_arg_def (phi
, e2
->dest_idx
);
438 /* Something is wrong if we cannot find the arguments in the PHI
440 gcc_assert (arg0
!= NULL
&& arg1
!= NULL
);
442 /* Do the replacement of conditional if it can be done. */
443 if (conditional_replacement (bb
, bb1
, e1
, e2
, phi
, arg0
, arg1
))
445 else if (abs_replacement (bb
, bb1
, e1
, e2
, phi
, arg0
, arg1
))
447 else if (minmax_replacement (bb
, bb1
, e1
, e2
, phi
, arg0
, arg1
))
455 pointer_set_destroy (nontrap
);
456 /* If the CFG has changed, we should cleanup the CFG. */
457 if (cfgchanged
&& do_store_elim
)
459 /* In cond-store replacement we have added some loads on edges
460 and new VOPS (as we moved the store, and created a load). */
461 gsi_commit_edge_inserts ();
462 return TODO_cleanup_cfg
| TODO_update_ssa_only_virtuals
;
465 return TODO_cleanup_cfg
;
469 /* Returns the list of basic blocks in the function in an order that guarantees
470 that if a block X has just a single predecessor Y, then Y is after X in the
474 blocks_in_phiopt_order (void)
477 basic_block
*order
= XNEWVEC (basic_block
, n_basic_blocks
);
478 unsigned n
= n_basic_blocks
- NUM_FIXED_BLOCKS
;
480 sbitmap visited
= sbitmap_alloc (last_basic_block
);
482 #define MARK_VISITED(BB) (SET_BIT (visited, (BB)->index))
483 #define VISITED_P(BB) (TEST_BIT (visited, (BB)->index))
485 bitmap_clear (visited
);
487 MARK_VISITED (ENTRY_BLOCK_PTR
);
493 /* Walk the predecessors of x as long as they have precisely one
494 predecessor and add them to the list, so that they get stored
497 single_pred_p (y
) && !VISITED_P (single_pred (y
));
500 for (y
= x
, i
= n
- np
;
501 single_pred_p (y
) && !VISITED_P (single_pred (y
));
502 y
= single_pred (y
), i
++)
510 gcc_assert (i
== n
- 1);
514 sbitmap_free (visited
);
522 /* Replace PHI node element whose edge is E in block BB with variable NEW.
523 Remove the edge from COND_BLOCK which does not lead to BB (COND_BLOCK
524 is known to have two edges, one of which must reach BB). */
527 replace_phi_edge_with_variable (basic_block cond_block
,
528 edge e
, gimple phi
, tree new_tree
)
530 basic_block bb
= gimple_bb (phi
);
531 basic_block block_to_remove
;
532 gimple_stmt_iterator gsi
;
534 /* Change the PHI argument to new. */
535 SET_USE (PHI_ARG_DEF_PTR (phi
, e
->dest_idx
), new_tree
);
537 /* Remove the empty basic block. */
538 if (EDGE_SUCC (cond_block
, 0)->dest
== bb
)
540 EDGE_SUCC (cond_block
, 0)->flags
|= EDGE_FALLTHRU
;
541 EDGE_SUCC (cond_block
, 0)->flags
&= ~(EDGE_TRUE_VALUE
| EDGE_FALSE_VALUE
);
542 EDGE_SUCC (cond_block
, 0)->probability
= REG_BR_PROB_BASE
;
543 EDGE_SUCC (cond_block
, 0)->count
+= EDGE_SUCC (cond_block
, 1)->count
;
545 block_to_remove
= EDGE_SUCC (cond_block
, 1)->dest
;
549 EDGE_SUCC (cond_block
, 1)->flags
|= EDGE_FALLTHRU
;
550 EDGE_SUCC (cond_block
, 1)->flags
551 &= ~(EDGE_TRUE_VALUE
| EDGE_FALSE_VALUE
);
552 EDGE_SUCC (cond_block
, 1)->probability
= REG_BR_PROB_BASE
;
553 EDGE_SUCC (cond_block
, 1)->count
+= EDGE_SUCC (cond_block
, 0)->count
;
555 block_to_remove
= EDGE_SUCC (cond_block
, 0)->dest
;
557 delete_basic_block (block_to_remove
);
559 /* Eliminate the COND_EXPR at the end of COND_BLOCK. */
560 gsi
= gsi_last_bb (cond_block
);
561 gsi_remove (&gsi
, true);
563 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
565 "COND_EXPR in block %d and PHI in block %d converted to straightline code.\n",
570 /* The function conditional_replacement does the main work of doing the
571 conditional replacement. Return true if the replacement is done.
572 Otherwise return false.
573 BB is the basic block where the replacement is going to be done on. ARG0
574 is argument 0 from PHI. Likewise for ARG1. */
577 conditional_replacement (basic_block cond_bb
, basic_block middle_bb
,
578 edge e0
, edge e1
, gimple phi
,
579 tree arg0
, tree arg1
)
582 gimple stmt
, new_stmt
;
584 gimple_stmt_iterator gsi
;
585 edge true_edge
, false_edge
;
586 tree new_var
, new_var2
;
589 /* FIXME: Gimplification of complex type is too hard for now. */
590 /* We aren't prepared to handle vectors either (and it is a question
591 if it would be worthwhile anyway). */
592 if (!(INTEGRAL_TYPE_P (TREE_TYPE (arg0
))
593 || POINTER_TYPE_P (TREE_TYPE (arg0
)))
594 || !(INTEGRAL_TYPE_P (TREE_TYPE (arg1
))
595 || POINTER_TYPE_P (TREE_TYPE (arg1
))))
598 /* The PHI arguments have the constants 0 and 1, or 0 and -1, then
599 convert it to the conditional. */
600 if ((integer_zerop (arg0
) && integer_onep (arg1
))
601 || (integer_zerop (arg1
) && integer_onep (arg0
)))
603 else if ((integer_zerop (arg0
) && integer_all_onesp (arg1
))
604 || (integer_zerop (arg1
) && integer_all_onesp (arg0
)))
609 if (!empty_block_p (middle_bb
))
612 /* At this point we know we have a GIMPLE_COND with two successors.
613 One successor is BB, the other successor is an empty block which
614 falls through into BB.
616 There is a single PHI node at the join point (BB) and its arguments
617 are constants (0, 1) or (0, -1).
619 So, given the condition COND, and the two PHI arguments, we can
620 rewrite this PHI into non-branching code:
622 dest = (COND) or dest = COND'
624 We use the condition as-is if the argument associated with the
625 true edge has the value one or the argument associated with the
626 false edge as the value zero. Note that those conditions are not
627 the same since only one of the outgoing edges from the GIMPLE_COND
628 will directly reach BB and thus be associated with an argument. */
630 stmt
= last_stmt (cond_bb
);
631 result
= PHI_RESULT (phi
);
633 /* To handle special cases like floating point comparison, it is easier and
634 less error-prone to build a tree and gimplify it on the fly though it is
636 cond
= fold_build2_loc (gimple_location (stmt
),
637 gimple_cond_code (stmt
), boolean_type_node
,
638 gimple_cond_lhs (stmt
), gimple_cond_rhs (stmt
));
640 /* We need to know which is the true edge and which is the false
641 edge so that we know when to invert the condition below. */
642 extract_true_false_edges_from_block (cond_bb
, &true_edge
, &false_edge
);
643 if ((e0
== true_edge
&& integer_zerop (arg0
))
644 || (e0
== false_edge
&& !integer_zerop (arg0
))
645 || (e1
== true_edge
&& integer_zerop (arg1
))
646 || (e1
== false_edge
&& !integer_zerop (arg1
)))
647 cond
= fold_build1_loc (gimple_location (stmt
),
648 TRUTH_NOT_EXPR
, TREE_TYPE (cond
), cond
);
652 cond
= fold_convert_loc (gimple_location (stmt
),
653 TREE_TYPE (result
), cond
);
654 cond
= fold_build1_loc (gimple_location (stmt
),
655 NEGATE_EXPR
, TREE_TYPE (cond
), cond
);
658 /* Insert our new statements at the end of conditional block before the
660 gsi
= gsi_for_stmt (stmt
);
661 new_var
= force_gimple_operand_gsi (&gsi
, cond
, true, NULL
, true,
664 if (!useless_type_conversion_p (TREE_TYPE (result
), TREE_TYPE (new_var
)))
666 source_location locus_0
, locus_1
;
668 new_var2
= make_ssa_name (TREE_TYPE (result
), NULL
);
669 new_stmt
= gimple_build_assign_with_ops (CONVERT_EXPR
, new_var2
,
671 gsi_insert_before (&gsi
, new_stmt
, GSI_SAME_STMT
);
674 /* Set the locus to the first argument, unless is doesn't have one. */
675 locus_0
= gimple_phi_arg_location (phi
, 0);
676 locus_1
= gimple_phi_arg_location (phi
, 1);
677 if (locus_0
== UNKNOWN_LOCATION
)
679 gimple_set_location (new_stmt
, locus_0
);
682 replace_phi_edge_with_variable (cond_bb
, e1
, phi
, new_var
);
684 /* Note that we optimized this PHI. */
688 /* Update *ARG which is defined in STMT so that it contains the
689 computed value if that seems profitable. Return true if the
690 statement is made dead by that rewriting. */
693 jump_function_from_stmt (tree
*arg
, gimple stmt
)
695 enum tree_code code
= gimple_assign_rhs_code (stmt
);
696 if (code
== ADDR_EXPR
)
698 /* For arg = &p->i transform it to p, if possible. */
699 tree rhs1
= gimple_assign_rhs1 (stmt
);
700 HOST_WIDE_INT offset
;
701 tree tem
= get_addr_base_and_unit_offset (TREE_OPERAND (rhs1
, 0),
704 && TREE_CODE (tem
) == MEM_REF
705 && (mem_ref_offset (tem
) + double_int::from_shwi (offset
)).is_zero ())
707 *arg
= TREE_OPERAND (tem
, 0);
711 /* TODO: Much like IPA-CP jump-functions we want to handle constant
712 additions symbolically here, and we'd need to update the comparison
713 code that compares the arg + cst tuples in our caller. For now the
714 code above exactly handles the VEC_BASE pattern from vec.h. */
718 /* The function value_replacement does the main work of doing the value
719 replacement. Return non-zero if the replacement is done. Otherwise return
720 0. If we remove the middle basic block, return 2.
721 BB is the basic block where the replacement is going to be done on. ARG0
722 is argument 0 from the PHI. Likewise for ARG1. */
725 value_replacement (basic_block cond_bb
, basic_block middle_bb
,
726 edge e0
, edge e1
, gimple phi
,
727 tree arg0
, tree arg1
)
729 gimple_stmt_iterator gsi
;
731 edge true_edge
, false_edge
;
733 bool emtpy_or_with_defined_p
= true;
735 /* If the type says honor signed zeros we cannot do this
737 if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1
))))
740 /* If there is a statement in MIDDLE_BB that defines one of the PHI
741 arguments, then adjust arg0 or arg1. */
742 gsi
= gsi_after_labels (middle_bb
);
743 if (!gsi_end_p (gsi
) && is_gimple_debug (gsi_stmt (gsi
)))
744 gsi_next_nondebug (&gsi
);
745 while (!gsi_end_p (gsi
))
747 gimple stmt
= gsi_stmt (gsi
);
749 gsi_next_nondebug (&gsi
);
750 if (!is_gimple_assign (stmt
))
752 emtpy_or_with_defined_p
= false;
755 /* Now try to adjust arg0 or arg1 according to the computation
757 lhs
= gimple_assign_lhs (stmt
);
759 && jump_function_from_stmt (&arg0
, stmt
))
761 && jump_function_from_stmt (&arg1
, stmt
)))
762 emtpy_or_with_defined_p
= false;
765 cond
= last_stmt (cond_bb
);
766 code
= gimple_cond_code (cond
);
768 /* This transformation is only valid for equality comparisons. */
769 if (code
!= NE_EXPR
&& code
!= EQ_EXPR
)
772 /* We need to know which is the true edge and which is the false
773 edge so that we know if have abs or negative abs. */
774 extract_true_false_edges_from_block (cond_bb
, &true_edge
, &false_edge
);
776 /* At this point we know we have a COND_EXPR with two successors.
777 One successor is BB, the other successor is an empty block which
778 falls through into BB.
780 The condition for the COND_EXPR is known to be NE_EXPR or EQ_EXPR.
782 There is a single PHI node at the join point (BB) with two arguments.
784 We now need to verify that the two arguments in the PHI node match
785 the two arguments to the equality comparison. */
787 if ((operand_equal_for_phi_arg_p (arg0
, gimple_cond_lhs (cond
))
788 && operand_equal_for_phi_arg_p (arg1
, gimple_cond_rhs (cond
)))
789 || (operand_equal_for_phi_arg_p (arg1
, gimple_cond_lhs (cond
))
790 && operand_equal_for_phi_arg_p (arg0
, gimple_cond_rhs (cond
))))
795 /* For NE_EXPR, we want to build an assignment result = arg where
796 arg is the PHI argument associated with the true edge. For
797 EQ_EXPR we want the PHI argument associated with the false edge. */
798 e
= (code
== NE_EXPR
? true_edge
: false_edge
);
800 /* Unfortunately, E may not reach BB (it may instead have gone to
801 OTHER_BLOCK). If that is the case, then we want the single outgoing
802 edge from OTHER_BLOCK which reaches BB and represents the desired
803 path from COND_BLOCK. */
804 if (e
->dest
== middle_bb
)
805 e
= single_succ_edge (e
->dest
);
807 /* Now we know the incoming edge to BB that has the argument for the
808 RHS of our new assignment statement. */
814 /* If the middle basic block was empty or is defining the
815 PHI arguments and this is a single phi where the args are different
816 for the edges e0 and e1 then we can remove the middle basic block. */
817 if (emtpy_or_with_defined_p
818 && single_non_singleton_phi_for_edges (phi_nodes (gimple_bb (phi
)),
821 replace_phi_edge_with_variable (cond_bb
, e1
, phi
, arg
);
822 /* Note that we optimized this PHI. */
827 /* Replace the PHI arguments with arg. */
828 SET_PHI_ARG_DEF (phi
, e0
->dest_idx
, arg
);
829 SET_PHI_ARG_DEF (phi
, e1
->dest_idx
, arg
);
830 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
832 fprintf (dump_file
, "PHI ");
833 print_generic_expr (dump_file
, gimple_phi_result (phi
), 0);
834 fprintf (dump_file
, " reduced for COND_EXPR in block %d to ",
836 print_generic_expr (dump_file
, arg
, 0);
837 fprintf (dump_file
, ".\n");
846 /* The function minmax_replacement does the main work of doing the minmax
847 replacement. Return true if the replacement is done. Otherwise return
849 BB is the basic block where the replacement is going to be done on. ARG0
850 is argument 0 from the PHI. Likewise for ARG1. */
853 minmax_replacement (basic_block cond_bb
, basic_block middle_bb
,
854 edge e0
, edge e1
, gimple phi
,
855 tree arg0
, tree arg1
)
858 gimple cond
, new_stmt
;
859 edge true_edge
, false_edge
;
860 enum tree_code cmp
, minmax
, ass_code
;
861 tree smaller
, larger
, arg_true
, arg_false
;
862 gimple_stmt_iterator gsi
, gsi_from
;
864 type
= TREE_TYPE (PHI_RESULT (phi
));
866 /* The optimization may be unsafe due to NaNs. */
867 if (HONOR_NANS (TYPE_MODE (type
)))
870 cond
= last_stmt (cond_bb
);
871 cmp
= gimple_cond_code (cond
);
873 /* This transformation is only valid for order comparisons. Record which
874 operand is smaller/larger if the result of the comparison is true. */
875 if (cmp
== LT_EXPR
|| cmp
== LE_EXPR
)
877 smaller
= gimple_cond_lhs (cond
);
878 larger
= gimple_cond_rhs (cond
);
880 else if (cmp
== GT_EXPR
|| cmp
== GE_EXPR
)
882 smaller
= gimple_cond_rhs (cond
);
883 larger
= gimple_cond_lhs (cond
);
888 /* We need to know which is the true edge and which is the false
889 edge so that we know if have abs or negative abs. */
890 extract_true_false_edges_from_block (cond_bb
, &true_edge
, &false_edge
);
892 /* Forward the edges over the middle basic block. */
893 if (true_edge
->dest
== middle_bb
)
894 true_edge
= EDGE_SUCC (true_edge
->dest
, 0);
895 if (false_edge
->dest
== middle_bb
)
896 false_edge
= EDGE_SUCC (false_edge
->dest
, 0);
900 gcc_assert (false_edge
== e1
);
906 gcc_assert (false_edge
== e0
);
907 gcc_assert (true_edge
== e1
);
912 if (empty_block_p (middle_bb
))
914 if (operand_equal_for_phi_arg_p (arg_true
, smaller
)
915 && operand_equal_for_phi_arg_p (arg_false
, larger
))
919 if (smaller < larger)
925 else if (operand_equal_for_phi_arg_p (arg_false
, smaller
)
926 && operand_equal_for_phi_arg_p (arg_true
, larger
))
933 /* Recognize the following case, assuming d <= u:
939 This is equivalent to
944 gimple assign
= last_and_only_stmt (middle_bb
);
945 tree lhs
, op0
, op1
, bound
;
948 || gimple_code (assign
) != GIMPLE_ASSIGN
)
951 lhs
= gimple_assign_lhs (assign
);
952 ass_code
= gimple_assign_rhs_code (assign
);
953 if (ass_code
!= MAX_EXPR
&& ass_code
!= MIN_EXPR
)
955 op0
= gimple_assign_rhs1 (assign
);
956 op1
= gimple_assign_rhs2 (assign
);
958 if (true_edge
->src
== middle_bb
)
960 /* We got here if the condition is true, i.e., SMALLER < LARGER. */
961 if (!operand_equal_for_phi_arg_p (lhs
, arg_true
))
964 if (operand_equal_for_phi_arg_p (arg_false
, larger
))
968 if (smaller < larger)
970 r' = MAX_EXPR (smaller, bound)
972 r = PHI <r', larger> --> to be turned to MIN_EXPR. */
973 if (ass_code
!= MAX_EXPR
)
977 if (operand_equal_for_phi_arg_p (op0
, smaller
))
979 else if (operand_equal_for_phi_arg_p (op1
, smaller
))
984 /* We need BOUND <= LARGER. */
985 if (!integer_nonzerop (fold_build2 (LE_EXPR
, boolean_type_node
,
989 else if (operand_equal_for_phi_arg_p (arg_false
, smaller
))
993 if (smaller < larger)
995 r' = MIN_EXPR (larger, bound)
997 r = PHI <r', smaller> --> to be turned to MAX_EXPR. */
998 if (ass_code
!= MIN_EXPR
)
1002 if (operand_equal_for_phi_arg_p (op0
, larger
))
1004 else if (operand_equal_for_phi_arg_p (op1
, larger
))
1009 /* We need BOUND >= SMALLER. */
1010 if (!integer_nonzerop (fold_build2 (GE_EXPR
, boolean_type_node
,
1019 /* We got here if the condition is false, i.e., SMALLER > LARGER. */
1020 if (!operand_equal_for_phi_arg_p (lhs
, arg_false
))
1023 if (operand_equal_for_phi_arg_p (arg_true
, larger
))
1027 if (smaller > larger)
1029 r' = MIN_EXPR (smaller, bound)
1031 r = PHI <r', larger> --> to be turned to MAX_EXPR. */
1032 if (ass_code
!= MIN_EXPR
)
1036 if (operand_equal_for_phi_arg_p (op0
, smaller
))
1038 else if (operand_equal_for_phi_arg_p (op1
, smaller
))
1043 /* We need BOUND >= LARGER. */
1044 if (!integer_nonzerop (fold_build2 (GE_EXPR
, boolean_type_node
,
1048 else if (operand_equal_for_phi_arg_p (arg_true
, smaller
))
1052 if (smaller > larger)
1054 r' = MAX_EXPR (larger, bound)
1056 r = PHI <r', smaller> --> to be turned to MIN_EXPR. */
1057 if (ass_code
!= MAX_EXPR
)
1061 if (operand_equal_for_phi_arg_p (op0
, larger
))
1063 else if (operand_equal_for_phi_arg_p (op1
, larger
))
1068 /* We need BOUND <= SMALLER. */
1069 if (!integer_nonzerop (fold_build2 (LE_EXPR
, boolean_type_node
,
1077 /* Move the statement from the middle block. */
1078 gsi
= gsi_last_bb (cond_bb
);
1079 gsi_from
= gsi_last_nondebug_bb (middle_bb
);
1080 gsi_move_before (&gsi_from
, &gsi
);
1083 /* Emit the statement to compute min/max. */
1084 result
= duplicate_ssa_name (PHI_RESULT (phi
), NULL
);
1085 new_stmt
= gimple_build_assign_with_ops (minmax
, result
, arg0
, arg1
);
1086 gsi
= gsi_last_bb (cond_bb
);
1087 gsi_insert_before (&gsi
, new_stmt
, GSI_NEW_STMT
);
1089 replace_phi_edge_with_variable (cond_bb
, e1
, phi
, result
);
1093 /* The function absolute_replacement does the main work of doing the absolute
1094 replacement. Return true if the replacement is done. Otherwise return
1096 bb is the basic block where the replacement is going to be done on. arg0
1097 is argument 0 from the phi. Likewise for arg1. */
1100 abs_replacement (basic_block cond_bb
, basic_block middle_bb
,
1101 edge e0 ATTRIBUTE_UNUSED
, edge e1
,
1102 gimple phi
, tree arg0
, tree arg1
)
1105 gimple new_stmt
, cond
;
1106 gimple_stmt_iterator gsi
;
1107 edge true_edge
, false_edge
;
1112 enum tree_code cond_code
;
1114 /* If the type says honor signed zeros we cannot do this
1116 if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1
))))
1119 /* OTHER_BLOCK must have only one executable statement which must have the
1120 form arg0 = -arg1 or arg1 = -arg0. */
1122 assign
= last_and_only_stmt (middle_bb
);
1123 /* If we did not find the proper negation assignment, then we can not
1128 /* If we got here, then we have found the only executable statement
1129 in OTHER_BLOCK. If it is anything other than arg = -arg1 or
1130 arg1 = -arg0, then we can not optimize. */
1131 if (gimple_code (assign
) != GIMPLE_ASSIGN
)
1134 lhs
= gimple_assign_lhs (assign
);
1136 if (gimple_assign_rhs_code (assign
) != NEGATE_EXPR
)
1139 rhs
= gimple_assign_rhs1 (assign
);
1141 /* The assignment has to be arg0 = -arg1 or arg1 = -arg0. */
1142 if (!(lhs
== arg0
&& rhs
== arg1
)
1143 && !(lhs
== arg1
&& rhs
== arg0
))
1146 cond
= last_stmt (cond_bb
);
1147 result
= PHI_RESULT (phi
);
1149 /* Only relationals comparing arg[01] against zero are interesting. */
1150 cond_code
= gimple_cond_code (cond
);
1151 if (cond_code
!= GT_EXPR
&& cond_code
!= GE_EXPR
1152 && cond_code
!= LT_EXPR
&& cond_code
!= LE_EXPR
)
1155 /* Make sure the conditional is arg[01] OP y. */
1156 if (gimple_cond_lhs (cond
) != rhs
)
1159 if (FLOAT_TYPE_P (TREE_TYPE (gimple_cond_rhs (cond
)))
1160 ? real_zerop (gimple_cond_rhs (cond
))
1161 : integer_zerop (gimple_cond_rhs (cond
)))
1166 /* We need to know which is the true edge and which is the false
1167 edge so that we know if have abs or negative abs. */
1168 extract_true_false_edges_from_block (cond_bb
, &true_edge
, &false_edge
);
1170 /* For GT_EXPR/GE_EXPR, if the true edge goes to OTHER_BLOCK, then we
1171 will need to negate the result. Similarly for LT_EXPR/LE_EXPR if
1172 the false edge goes to OTHER_BLOCK. */
1173 if (cond_code
== GT_EXPR
|| cond_code
== GE_EXPR
)
1178 if (e
->dest
== middle_bb
)
1183 result
= duplicate_ssa_name (result
, NULL
);
1186 lhs
= make_ssa_name (TREE_TYPE (result
), NULL
);
1190 /* Build the modify expression with abs expression. */
1191 new_stmt
= gimple_build_assign_with_ops (ABS_EXPR
, lhs
, rhs
, NULL
);
1193 gsi
= gsi_last_bb (cond_bb
);
1194 gsi_insert_before (&gsi
, new_stmt
, GSI_NEW_STMT
);
1198 /* Get the right GSI. We want to insert after the recently
1199 added ABS_EXPR statement (which we know is the first statement
1201 new_stmt
= gimple_build_assign_with_ops (NEGATE_EXPR
, result
, lhs
, NULL
);
1203 gsi_insert_after (&gsi
, new_stmt
, GSI_NEW_STMT
);
1206 replace_phi_edge_with_variable (cond_bb
, e1
, phi
, result
);
1208 /* Note that we optimized this PHI. */
1212 /* Auxiliary functions to determine the set of memory accesses which
1213 can't trap because they are preceded by accesses to the same memory
1214 portion. We do that for MEM_REFs, so we only need to track
1215 the SSA_NAME of the pointer indirectly referenced. The algorithm
1216 simply is a walk over all instructions in dominator order. When
1217 we see an MEM_REF we determine if we've already seen a same
1218 ref anywhere up to the root of the dominator tree. If we do the
1219 current access can't trap. If we don't see any dominating access
1220 the current access might trap, but might also make later accesses
1221 non-trapping, so we remember it. We need to be careful with loads
1222 or stores, for instance a load might not trap, while a store would,
1223 so if we see a dominating read access this doesn't mean that a later
1224 write access would not trap. Hence we also need to differentiate the
1225 type of access(es) seen.
1227 ??? We currently are very conservative and assume that a load might
1228 trap even if a store doesn't (write-only memory). This probably is
1229 overly conservative. */
1231 /* A hash-table of SSA_NAMEs, and in which basic block an MEM_REF
1232 through it was seen, which would constitute a no-trap region for
1236 unsigned int ssa_name_ver
;
1238 HOST_WIDE_INT offset
, size
;
1242 /* The hash table for remembering what we've seen. */
1243 static htab_t seen_ssa_names
;
1245 /* The set of MEM_REFs which can't trap. */
1246 static struct pointer_set_t
*nontrap_set
;
1248 /* The hash function. */
1250 name_to_bb_hash (const void *p
)
1252 const struct name_to_bb
*n
= (const struct name_to_bb
*) p
;
1253 return n
->ssa_name_ver
^ (((hashval_t
) n
->store
) << 31)
1254 ^ (n
->offset
<< 6) ^ (n
->size
<< 3);
1257 /* The equality function of *P1 and *P2. */
1259 name_to_bb_eq (const void *p1
, const void *p2
)
1261 const struct name_to_bb
*n1
= (const struct name_to_bb
*)p1
;
1262 const struct name_to_bb
*n2
= (const struct name_to_bb
*)p2
;
1264 return n1
->ssa_name_ver
== n2
->ssa_name_ver
1265 && n1
->store
== n2
->store
1266 && n1
->offset
== n2
->offset
1267 && n1
->size
== n2
->size
;
1270 /* We see the expression EXP in basic block BB. If it's an interesting
1271 expression (an MEM_REF through an SSA_NAME) possibly insert the
1272 expression into the set NONTRAP or the hash table of seen expressions.
1273 STORE is true if this expression is on the LHS, otherwise it's on
1276 add_or_mark_expr (basic_block bb
, tree exp
,
1277 struct pointer_set_t
*nontrap
, bool store
)
1281 if (TREE_CODE (exp
) == MEM_REF
1282 && TREE_CODE (TREE_OPERAND (exp
, 0)) == SSA_NAME
1283 && host_integerp (TREE_OPERAND (exp
, 1), 0)
1284 && (size
= int_size_in_bytes (TREE_TYPE (exp
))) > 0)
1286 tree name
= TREE_OPERAND (exp
, 0);
1287 struct name_to_bb map
;
1289 struct name_to_bb
*n2bb
;
1290 basic_block found_bb
= 0;
1292 /* Try to find the last seen MEM_REF through the same
1293 SSA_NAME, which can trap. */
1294 map
.ssa_name_ver
= SSA_NAME_VERSION (name
);
1297 map
.offset
= tree_low_cst (TREE_OPERAND (exp
, 1), 0);
1300 slot
= htab_find_slot (seen_ssa_names
, &map
, INSERT
);
1301 n2bb
= (struct name_to_bb
*) *slot
;
1303 found_bb
= n2bb
->bb
;
1305 /* If we've found a trapping MEM_REF, _and_ it dominates EXP
1306 (it's in a basic block on the path from us to the dominator root)
1307 then we can't trap. */
1308 if (found_bb
&& found_bb
->aux
== (void *)1)
1310 pointer_set_insert (nontrap
, exp
);
1314 /* EXP might trap, so insert it into the hash table. */
1321 n2bb
= XNEW (struct name_to_bb
);
1322 n2bb
->ssa_name_ver
= SSA_NAME_VERSION (name
);
1324 n2bb
->store
= store
;
1325 n2bb
->offset
= map
.offset
;
1333 /* Called by walk_dominator_tree, when entering the block BB. */
1335 nt_init_block (struct dom_walk_data
*data ATTRIBUTE_UNUSED
, basic_block bb
)
1337 gimple_stmt_iterator gsi
;
1338 /* Mark this BB as being on the path to dominator root. */
1341 /* And walk the statements in order. */
1342 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1344 gimple stmt
= gsi_stmt (gsi
);
1346 if (gimple_assign_single_p (stmt
))
1348 add_or_mark_expr (bb
, gimple_assign_lhs (stmt
), nontrap_set
, true);
1349 add_or_mark_expr (bb
, gimple_assign_rhs1 (stmt
), nontrap_set
, false);
1354 /* Called by walk_dominator_tree, when basic block BB is exited. */
1356 nt_fini_block (struct dom_walk_data
*data ATTRIBUTE_UNUSED
, basic_block bb
)
1358 /* This BB isn't on the path to dominator root anymore. */
1362 /* This is the entry point of gathering non trapping memory accesses.
1363 It will do a dominator walk over the whole function, and it will
1364 make use of the bb->aux pointers. It returns a set of trees
1365 (the MEM_REFs itself) which can't trap. */
1366 static struct pointer_set_t
*
1367 get_non_trapping (void)
1369 struct pointer_set_t
*nontrap
;
1370 struct dom_walk_data walk_data
;
1372 nontrap
= pointer_set_create ();
1373 seen_ssa_names
= htab_create (128, name_to_bb_hash
, name_to_bb_eq
,
1375 /* We're going to do a dominator walk, so ensure that we have
1376 dominance information. */
1377 calculate_dominance_info (CDI_DOMINATORS
);
1379 /* Setup callbacks for the generic dominator tree walker. */
1380 nontrap_set
= nontrap
;
1381 walk_data
.dom_direction
= CDI_DOMINATORS
;
1382 walk_data
.initialize_block_local_data
= NULL
;
1383 walk_data
.before_dom_children
= nt_init_block
;
1384 walk_data
.after_dom_children
= nt_fini_block
;
1385 walk_data
.global_data
= NULL
;
1386 walk_data
.block_local_data_size
= 0;
1388 init_walk_dominator_tree (&walk_data
);
1389 walk_dominator_tree (&walk_data
, ENTRY_BLOCK_PTR
);
1390 fini_walk_dominator_tree (&walk_data
);
1391 htab_delete (seen_ssa_names
);
1396 /* Do the main work of conditional store replacement. We already know
1397 that the recognized pattern looks like so:
1400 if (cond) goto MIDDLE_BB; else goto JOIN_BB (edge E1)
1403 fallthrough (edge E0)
1407 We check that MIDDLE_BB contains only one store, that that store
1408 doesn't trap (not via NOTRAP, but via checking if an access to the same
1409 memory location dominates us) and that the store has a "simple" RHS. */
1412 cond_store_replacement (basic_block middle_bb
, basic_block join_bb
,
1413 edge e0
, edge e1
, struct pointer_set_t
*nontrap
)
1415 gimple assign
= last_and_only_stmt (middle_bb
);
1416 tree lhs
, rhs
, name
, name2
;
1417 gimple newphi
, new_stmt
;
1418 gimple_stmt_iterator gsi
;
1419 source_location locus
;
1421 /* Check if middle_bb contains of only one store. */
1423 || !gimple_assign_single_p (assign
))
1426 locus
= gimple_location (assign
);
1427 lhs
= gimple_assign_lhs (assign
);
1428 rhs
= gimple_assign_rhs1 (assign
);
1429 if (TREE_CODE (lhs
) != MEM_REF
1430 || TREE_CODE (TREE_OPERAND (lhs
, 0)) != SSA_NAME
1431 || !is_gimple_reg_type (TREE_TYPE (lhs
)))
1434 /* Prove that we can move the store down. We could also check
1435 TREE_THIS_NOTRAP here, but in that case we also could move stores,
1436 whose value is not available readily, which we want to avoid. */
1437 if (!pointer_set_contains (nontrap
, lhs
))
1440 /* Now we've checked the constraints, so do the transformation:
1441 1) Remove the single store. */
1442 gsi
= gsi_for_stmt (assign
);
1443 unlink_stmt_vdef (assign
);
1444 gsi_remove (&gsi
, true);
1445 release_defs (assign
);
1447 /* 2) Insert a load from the memory of the store to the temporary
1448 on the edge which did not contain the store. */
1449 lhs
= unshare_expr (lhs
);
1450 name
= make_temp_ssa_name (TREE_TYPE (lhs
), NULL
, "cstore");
1451 new_stmt
= gimple_build_assign (name
, lhs
);
1452 gimple_set_location (new_stmt
, locus
);
1453 gsi_insert_on_edge (e1
, new_stmt
);
1455 /* 3) Create a PHI node at the join block, with one argument
1456 holding the old RHS, and the other holding the temporary
1457 where we stored the old memory contents. */
1458 name2
= make_temp_ssa_name (TREE_TYPE (lhs
), NULL
, "cstore");
1459 newphi
= create_phi_node (name2
, join_bb
);
1460 add_phi_arg (newphi
, rhs
, e0
, locus
);
1461 add_phi_arg (newphi
, name
, e1
, locus
);
1463 lhs
= unshare_expr (lhs
);
1464 new_stmt
= gimple_build_assign (lhs
, PHI_RESULT (newphi
));
1466 /* 4) Insert that PHI node. */
1467 gsi
= gsi_after_labels (join_bb
);
1468 if (gsi_end_p (gsi
))
1470 gsi
= gsi_last_bb (join_bb
);
1471 gsi_insert_after (&gsi
, new_stmt
, GSI_NEW_STMT
);
1474 gsi_insert_before (&gsi
, new_stmt
, GSI_NEW_STMT
);
1479 /* Do the main work of conditional store replacement. */
1482 cond_if_else_store_replacement_1 (basic_block then_bb
, basic_block else_bb
,
1483 basic_block join_bb
, gimple then_assign
,
1486 tree lhs_base
, lhs
, then_rhs
, else_rhs
, name
;
1487 source_location then_locus
, else_locus
;
1488 gimple_stmt_iterator gsi
;
1489 gimple newphi
, new_stmt
;
1491 if (then_assign
== NULL
1492 || !gimple_assign_single_p (then_assign
)
1493 || gimple_clobber_p (then_assign
)
1494 || else_assign
== NULL
1495 || !gimple_assign_single_p (else_assign
)
1496 || gimple_clobber_p (else_assign
))
1499 lhs
= gimple_assign_lhs (then_assign
);
1500 if (!is_gimple_reg_type (TREE_TYPE (lhs
))
1501 || !operand_equal_p (lhs
, gimple_assign_lhs (else_assign
), 0))
1504 lhs_base
= get_base_address (lhs
);
1505 if (lhs_base
== NULL_TREE
1506 || (!DECL_P (lhs_base
) && TREE_CODE (lhs_base
) != MEM_REF
))
1509 then_rhs
= gimple_assign_rhs1 (then_assign
);
1510 else_rhs
= gimple_assign_rhs1 (else_assign
);
1511 then_locus
= gimple_location (then_assign
);
1512 else_locus
= gimple_location (else_assign
);
1514 /* Now we've checked the constraints, so do the transformation:
1515 1) Remove the stores. */
1516 gsi
= gsi_for_stmt (then_assign
);
1517 unlink_stmt_vdef (then_assign
);
1518 gsi_remove (&gsi
, true);
1519 release_defs (then_assign
);
1521 gsi
= gsi_for_stmt (else_assign
);
1522 unlink_stmt_vdef (else_assign
);
1523 gsi_remove (&gsi
, true);
1524 release_defs (else_assign
);
1526 /* 2) Create a PHI node at the join block, with one argument
1527 holding the old RHS, and the other holding the temporary
1528 where we stored the old memory contents. */
1529 name
= make_temp_ssa_name (TREE_TYPE (lhs
), NULL
, "cstore");
1530 newphi
= create_phi_node (name
, join_bb
);
1531 add_phi_arg (newphi
, then_rhs
, EDGE_SUCC (then_bb
, 0), then_locus
);
1532 add_phi_arg (newphi
, else_rhs
, EDGE_SUCC (else_bb
, 0), else_locus
);
1534 new_stmt
= gimple_build_assign (lhs
, PHI_RESULT (newphi
));
1536 /* 3) Insert that PHI node. */
1537 gsi
= gsi_after_labels (join_bb
);
1538 if (gsi_end_p (gsi
))
1540 gsi
= gsi_last_bb (join_bb
);
1541 gsi_insert_after (&gsi
, new_stmt
, GSI_NEW_STMT
);
1544 gsi_insert_before (&gsi
, new_stmt
, GSI_NEW_STMT
);
1549 /* Conditional store replacement. We already know
1550 that the recognized pattern looks like so:
1553 if (cond) goto THEN_BB; else goto ELSE_BB (edge E1)
1563 fallthrough (edge E0)
1567 We check that it is safe to sink the store to JOIN_BB by verifying that
1568 there are no read-after-write or write-after-write dependencies in
1569 THEN_BB and ELSE_BB. */
1572 cond_if_else_store_replacement (basic_block then_bb
, basic_block else_bb
,
1573 basic_block join_bb
)
1575 gimple then_assign
= last_and_only_stmt (then_bb
);
1576 gimple else_assign
= last_and_only_stmt (else_bb
);
1577 VEC (data_reference_p
, heap
) *then_datarefs
, *else_datarefs
;
1578 VEC (ddr_p
, heap
) *then_ddrs
, *else_ddrs
;
1579 gimple then_store
, else_store
;
1580 bool found
, ok
= false, res
;
1581 struct data_dependence_relation
*ddr
;
1582 data_reference_p then_dr
, else_dr
;
1584 tree then_lhs
, else_lhs
;
1585 VEC (gimple
, heap
) *then_stores
, *else_stores
;
1586 basic_block blocks
[3];
1588 if (MAX_STORES_TO_SINK
== 0)
1591 /* Handle the case with single statement in THEN_BB and ELSE_BB. */
1592 if (then_assign
&& else_assign
)
1593 return cond_if_else_store_replacement_1 (then_bb
, else_bb
, join_bb
,
1594 then_assign
, else_assign
);
1596 /* Find data references. */
1597 then_datarefs
= VEC_alloc (data_reference_p
, heap
, 1);
1598 else_datarefs
= VEC_alloc (data_reference_p
, heap
, 1);
1599 if ((find_data_references_in_bb (NULL
, then_bb
, &then_datarefs
)
1601 || !VEC_length (data_reference_p
, then_datarefs
)
1602 || (find_data_references_in_bb (NULL
, else_bb
, &else_datarefs
)
1604 || !VEC_length (data_reference_p
, else_datarefs
))
1606 free_data_refs (then_datarefs
);
1607 free_data_refs (else_datarefs
);
1611 /* Find pairs of stores with equal LHS. */
1612 then_stores
= VEC_alloc (gimple
, heap
, 1);
1613 else_stores
= VEC_alloc (gimple
, heap
, 1);
1614 FOR_EACH_VEC_ELT (data_reference_p
, then_datarefs
, i
, then_dr
)
1616 if (DR_IS_READ (then_dr
))
1619 then_store
= DR_STMT (then_dr
);
1620 then_lhs
= gimple_get_lhs (then_store
);
1623 FOR_EACH_VEC_ELT (data_reference_p
, else_datarefs
, j
, else_dr
)
1625 if (DR_IS_READ (else_dr
))
1628 else_store
= DR_STMT (else_dr
);
1629 else_lhs
= gimple_get_lhs (else_store
);
1631 if (operand_equal_p (then_lhs
, else_lhs
, 0))
1641 VEC_safe_push (gimple
, heap
, then_stores
, then_store
);
1642 VEC_safe_push (gimple
, heap
, else_stores
, else_store
);
1645 /* No pairs of stores found. */
1646 if (!VEC_length (gimple
, then_stores
)
1647 || VEC_length (gimple
, then_stores
) > (unsigned) MAX_STORES_TO_SINK
)
1649 free_data_refs (then_datarefs
);
1650 free_data_refs (else_datarefs
);
1651 VEC_free (gimple
, heap
, then_stores
);
1652 VEC_free (gimple
, heap
, else_stores
);
1656 /* Compute and check data dependencies in both basic blocks. */
1657 then_ddrs
= VEC_alloc (ddr_p
, heap
, 1);
1658 else_ddrs
= VEC_alloc (ddr_p
, heap
, 1);
1659 if (!compute_all_dependences (then_datarefs
, &then_ddrs
, NULL
, false)
1660 || !compute_all_dependences (else_datarefs
, &else_ddrs
, NULL
, false))
1662 free_dependence_relations (then_ddrs
);
1663 free_dependence_relations (else_ddrs
);
1664 free_data_refs (then_datarefs
);
1665 free_data_refs (else_datarefs
);
1666 VEC_free (gimple
, heap
, then_stores
);
1667 VEC_free (gimple
, heap
, else_stores
);
1670 blocks
[0] = then_bb
;
1671 blocks
[1] = else_bb
;
1672 blocks
[2] = join_bb
;
1673 renumber_gimple_stmt_uids_in_blocks (blocks
, 3);
1675 /* Check that there are no read-after-write or write-after-write dependencies
1677 FOR_EACH_VEC_ELT (ddr_p
, then_ddrs
, i
, ddr
)
1679 struct data_reference
*dra
= DDR_A (ddr
);
1680 struct data_reference
*drb
= DDR_B (ddr
);
1682 if (DDR_ARE_DEPENDENT (ddr
) != chrec_known
1683 && ((DR_IS_READ (dra
) && DR_IS_WRITE (drb
)
1684 && gimple_uid (DR_STMT (dra
)) > gimple_uid (DR_STMT (drb
)))
1685 || (DR_IS_READ (drb
) && DR_IS_WRITE (dra
)
1686 && gimple_uid (DR_STMT (drb
)) > gimple_uid (DR_STMT (dra
)))
1687 || (DR_IS_WRITE (dra
) && DR_IS_WRITE (drb
))))
1689 free_dependence_relations (then_ddrs
);
1690 free_dependence_relations (else_ddrs
);
1691 free_data_refs (then_datarefs
);
1692 free_data_refs (else_datarefs
);
1693 VEC_free (gimple
, heap
, then_stores
);
1694 VEC_free (gimple
, heap
, else_stores
);
1699 /* Check that there are no read-after-write or write-after-write dependencies
1701 FOR_EACH_VEC_ELT (ddr_p
, else_ddrs
, i
, ddr
)
1703 struct data_reference
*dra
= DDR_A (ddr
);
1704 struct data_reference
*drb
= DDR_B (ddr
);
1706 if (DDR_ARE_DEPENDENT (ddr
) != chrec_known
1707 && ((DR_IS_READ (dra
) && DR_IS_WRITE (drb
)
1708 && gimple_uid (DR_STMT (dra
)) > gimple_uid (DR_STMT (drb
)))
1709 || (DR_IS_READ (drb
) && DR_IS_WRITE (dra
)
1710 && gimple_uid (DR_STMT (drb
)) > gimple_uid (DR_STMT (dra
)))
1711 || (DR_IS_WRITE (dra
) && DR_IS_WRITE (drb
))))
1713 free_dependence_relations (then_ddrs
);
1714 free_dependence_relations (else_ddrs
);
1715 free_data_refs (then_datarefs
);
1716 free_data_refs (else_datarefs
);
1717 VEC_free (gimple
, heap
, then_stores
);
1718 VEC_free (gimple
, heap
, else_stores
);
1723 /* Sink stores with same LHS. */
1724 FOR_EACH_VEC_ELT (gimple
, then_stores
, i
, then_store
)
1726 else_store
= VEC_index (gimple
, else_stores
, i
);
1727 res
= cond_if_else_store_replacement_1 (then_bb
, else_bb
, join_bb
,
1728 then_store
, else_store
);
1732 free_dependence_relations (then_ddrs
);
1733 free_dependence_relations (else_ddrs
);
1734 free_data_refs (then_datarefs
);
1735 free_data_refs (else_datarefs
);
1736 VEC_free (gimple
, heap
, then_stores
);
1737 VEC_free (gimple
, heap
, else_stores
);
1742 /* Return TRUE if STMT has a VUSE whose corresponding VDEF is in BB. */
1745 local_mem_dependence (gimple stmt
, basic_block bb
)
1747 tree vuse
= gimple_vuse (stmt
);
1753 def
= SSA_NAME_DEF_STMT (vuse
);
1754 return (def
&& gimple_bb (def
) == bb
);
1757 /* Given a "diamond" control-flow pattern where BB0 tests a condition,
1758 BB1 and BB2 are "then" and "else" blocks dependent on this test,
1759 and BB3 rejoins control flow following BB1 and BB2, look for
1760 opportunities to hoist loads as follows. If BB3 contains a PHI of
1761 two loads, one each occurring in BB1 and BB2, and the loads are
1762 provably of adjacent fields in the same structure, then move both
1763 loads into BB0. Of course this can only be done if there are no
1764 dependencies preventing such motion.
1766 One of the hoisted loads will always be speculative, so the
1767 transformation is currently conservative:
1769 - The fields must be strictly adjacent.
1770 - The two fields must occupy a single memory block that is
1771 guaranteed to not cross a page boundary.
1773 The last is difficult to prove, as such memory blocks should be
1774 aligned on the minimum of the stack alignment boundary and the
1775 alignment guaranteed by heap allocation interfaces. Thus we rely
1776 on a parameter for the alignment value.
1778 Provided a good value is used for the last case, the first
1779 restriction could possibly be relaxed. */
1782 hoist_adjacent_loads (basic_block bb0
, basic_block bb1
,
1783 basic_block bb2
, basic_block bb3
)
1785 int param_align
= PARAM_VALUE (PARAM_L1_CACHE_LINE_SIZE
);
1786 unsigned param_align_bits
= (unsigned) (param_align
* BITS_PER_UNIT
);
1787 gimple_stmt_iterator gsi
;
1789 /* Walk the phis in bb3 looking for an opportunity. We are looking
1790 for phis of two SSA names, one each of which is defined in bb1 and
1792 for (gsi
= gsi_start_phis (bb3
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1794 gimple phi_stmt
= gsi_stmt (gsi
);
1795 gimple def1
, def2
, defswap
;
1796 tree arg1
, arg2
, ref1
, ref2
, field1
, field2
, fieldswap
;
1797 tree tree_offset1
, tree_offset2
, tree_size2
, next
;
1798 int offset1
, offset2
, size2
;
1800 gimple_stmt_iterator gsi2
;
1801 basic_block bb_for_def1
, bb_for_def2
;
1803 if (gimple_phi_num_args (phi_stmt
) != 2
1804 || virtual_operand_p (gimple_phi_result (phi_stmt
)))
1807 arg1
= gimple_phi_arg_def (phi_stmt
, 0);
1808 arg2
= gimple_phi_arg_def (phi_stmt
, 1);
1810 if (TREE_CODE (arg1
) != SSA_NAME
1811 || TREE_CODE (arg2
) != SSA_NAME
1812 || SSA_NAME_IS_DEFAULT_DEF (arg1
)
1813 || SSA_NAME_IS_DEFAULT_DEF (arg2
))
1816 def1
= SSA_NAME_DEF_STMT (arg1
);
1817 def2
= SSA_NAME_DEF_STMT (arg2
);
1819 if ((gimple_bb (def1
) != bb1
|| gimple_bb (def2
) != bb2
)
1820 && (gimple_bb (def2
) != bb1
|| gimple_bb (def1
) != bb2
))
1823 /* Check the mode of the arguments to be sure a conditional move
1824 can be generated for it. */
1825 if (optab_handler (movcc_optab
, TYPE_MODE (TREE_TYPE (arg1
)))
1826 == CODE_FOR_nothing
)
1829 /* Both statements must be assignments whose RHS is a COMPONENT_REF. */
1830 if (!gimple_assign_single_p (def1
)
1831 || !gimple_assign_single_p (def2
))
1834 ref1
= gimple_assign_rhs1 (def1
);
1835 ref2
= gimple_assign_rhs1 (def2
);
1837 if (TREE_CODE (ref1
) != COMPONENT_REF
1838 || TREE_CODE (ref2
) != COMPONENT_REF
)
1841 /* The zeroth operand of the two component references must be
1842 identical. It is not sufficient to compare get_base_address of
1843 the two references, because this could allow for different
1844 elements of the same array in the two trees. It is not safe to
1845 assume that the existence of one array element implies the
1846 existence of a different one. */
1847 if (!operand_equal_p (TREE_OPERAND (ref1
, 0), TREE_OPERAND (ref2
, 0), 0))
1850 field1
= TREE_OPERAND (ref1
, 1);
1851 field2
= TREE_OPERAND (ref2
, 1);
1853 /* Check for field adjacency, and ensure field1 comes first. */
1854 for (next
= DECL_CHAIN (field1
);
1855 next
&& TREE_CODE (next
) != FIELD_DECL
;
1856 next
= DECL_CHAIN (next
))
1861 for (next
= DECL_CHAIN (field2
);
1862 next
&& TREE_CODE (next
) != FIELD_DECL
;
1863 next
= DECL_CHAIN (next
))
1877 bb_for_def1
= gimple_bb (def1
);
1878 bb_for_def2
= gimple_bb (def2
);
1880 /* Check for proper alignment of the first field. */
1881 tree_offset1
= bit_position (field1
);
1882 tree_offset2
= bit_position (field2
);
1883 tree_size2
= DECL_SIZE (field2
);
1885 if (!host_integerp (tree_offset1
, 1)
1886 || !host_integerp (tree_offset2
, 1)
1887 || !host_integerp (tree_size2
, 1))
1890 offset1
= TREE_INT_CST_LOW (tree_offset1
);
1891 offset2
= TREE_INT_CST_LOW (tree_offset2
);
1892 size2
= TREE_INT_CST_LOW (tree_size2
);
1893 align1
= DECL_ALIGN (field1
) % param_align_bits
;
1895 if (offset1
% BITS_PER_UNIT
!= 0)
1898 /* For profitability, the two field references should fit within
1899 a single cache line. */
1900 if (align1
+ offset2
- offset1
+ size2
> param_align_bits
)
1903 /* The two expressions cannot be dependent upon vdefs defined
1905 if (local_mem_dependence (def1
, bb_for_def1
)
1906 || local_mem_dependence (def2
, bb_for_def2
))
1909 /* The conditions are satisfied; hoist the loads from bb1 and bb2 into
1910 bb0. We hoist the first one first so that a cache miss is handled
1911 efficiently regardless of hardware cache-fill policy. */
1912 gsi2
= gsi_for_stmt (def1
);
1913 gsi_move_to_bb_end (&gsi2
, bb0
);
1914 gsi2
= gsi_for_stmt (def2
);
1915 gsi_move_to_bb_end (&gsi2
, bb0
);
1917 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1920 "\nHoisting adjacent loads from %d and %d into %d: \n",
1921 bb_for_def1
->index
, bb_for_def2
->index
, bb0
->index
);
1922 print_gimple_stmt (dump_file
, def1
, 0, TDF_VOPS
|TDF_MEMSYMS
);
1923 print_gimple_stmt (dump_file
, def2
, 0, TDF_VOPS
|TDF_MEMSYMS
);
1928 /* Determine whether we should attempt to hoist adjacent loads out of
1929 diamond patterns in pass_phiopt. Always hoist loads if
1930 -fhoist-adjacent-loads is specified and the target machine has
1931 both a conditional move instruction and a defined cache line size. */
1934 gate_hoist_loads (void)
1936 return (flag_hoist_adjacent_loads
== 1
1937 && PARAM_VALUE (PARAM_L1_CACHE_LINE_SIZE
)
1938 && HAVE_conditional_move
);
1941 /* Always do these optimizations if we have SSA
1942 trees to work on. */
1949 struct gimple_opt_pass pass_phiopt
=
1953 "phiopt", /* name */
1954 gate_phiopt
, /* gate */
1955 tree_ssa_phiopt
, /* execute */
1958 0, /* static_pass_number */
1959 TV_TREE_PHIOPT
, /* tv_id */
1960 PROP_cfg
| PROP_ssa
, /* properties_required */
1961 0, /* properties_provided */
1962 0, /* properties_destroyed */
1963 0, /* todo_flags_start */
1967 | TODO_verify_stmts
/* todo_flags_finish */
1974 return flag_tree_cselim
;
1977 struct gimple_opt_pass pass_cselim
=
1981 "cselim", /* name */
1982 gate_cselim
, /* gate */
1983 tree_ssa_cs_elim
, /* execute */
1986 0, /* static_pass_number */
1987 TV_TREE_PHIOPT
, /* tv_id */
1988 PROP_cfg
| PROP_ssa
, /* properties_required */
1989 0, /* properties_provided */
1990 0, /* properties_destroyed */
1991 0, /* todo_flags_start */
1995 | TODO_verify_stmts
/* todo_flags_finish */