1 /* Convert a program in SSA form into Normal form.
2 Copyright (C) 2004-2015 Free Software Foundation, Inc.
3 Contributed by Andrew Macleod <amacleod@redhat.com>
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3, or (at your option)
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
23 #include "coretypes.h"
29 #include "fold-const.h"
30 #include "stor-layout.h"
32 #include "hard-reg-set.h"
34 #include "dominance.h"
38 #include "basic-block.h"
39 #include "gimple-pretty-print.h"
42 #include "tree-ssa-alias.h"
43 #include "internal-fn.h"
45 #include "gimple-expr.h"
48 #include "gimple-iterator.h"
49 #include "gimple-ssa.h"
51 #include "tree-phinodes.h"
52 #include "ssa-iterators.h"
53 #include "stringpool.h"
54 #include "tree-ssanames.h"
56 #include "diagnostic-core.h"
57 #include "tree-ssa-live.h"
58 #include "tree-ssa-ter.h"
59 #include "tree-ssa-coalesce.h"
60 #include "tree-outof-ssa.h"
62 /* FIXME: A lot of code here deals with expanding to RTL. All that code
63 should be in cfgexpand.c. */
66 #include "insn-config.h"
76 /* Return TRUE if expression STMT is suitable for replacement. */
79 ssa_is_replaceable_p (gimple stmt
)
85 /* Only consider modify stmts. */
86 if (!is_gimple_assign (stmt
))
89 /* If the statement may throw an exception, it cannot be replaced. */
90 if (stmt_could_throw_p (stmt
))
93 /* Punt if there is more than 1 def. */
94 def
= SINGLE_SSA_TREE_OPERAND (stmt
, SSA_OP_DEF
);
98 /* Only consider definitions which have a single use. */
99 if (!single_imm_use (def
, &use_p
, &use_stmt
))
102 /* Used in this block, but at the TOP of the block, not the end. */
103 if (gimple_code (use_stmt
) == GIMPLE_PHI
)
106 /* There must be no VDEFs. */
107 if (gimple_vdef (stmt
))
110 /* Float expressions must go through memory if float-store is on. */
112 && FLOAT_TYPE_P (gimple_expr_type (stmt
)))
115 /* An assignment with a register variable on the RHS is not
117 if (gimple_assign_rhs_code (stmt
) == VAR_DECL
118 && DECL_HARD_REGISTER (gimple_assign_rhs1 (stmt
)))
121 /* No function calls can be replaced. */
122 if (is_gimple_call (stmt
))
125 /* Leave any stmt with volatile operands alone as well. */
126 if (gimple_has_volatile_ops (stmt
))
133 /* Used to hold all the components required to do SSA PHI elimination.
134 The node and pred/succ list is a simple linear list of nodes and
135 edges represented as pairs of nodes.
137 The predecessor and successor list: Nodes are entered in pairs, where
138 [0] ->PRED, [1]->SUCC. All the even indexes in the array represent
139 predecessors, all the odd elements are successors.
142 When implemented as bitmaps, very large programs SSA->Normal times were
143 being dominated by clearing the interference graph.
145 Typically this list of edges is extremely small since it only includes
146 PHI results and uses from a single edge which have not coalesced with
147 each other. This means that no virtual PHI nodes are included, and
148 empirical evidence suggests that the number of edges rarely exceed
149 3, and in a bootstrap of GCC, the maximum size encountered was 7.
150 This also limits the number of possible nodes that are involved to
151 rarely more than 6, and in the bootstrap of gcc, the maximum number
152 of nodes encountered was 12. */
154 typedef struct _elim_graph
{
155 /* Size of the elimination vectors. */
158 /* List of nodes in the elimination graph. */
161 /* The predecessor and successor edge list. */
164 /* Source locus on each edge */
165 vec
<source_location
> edge_locus
;
167 /* Visited vector. */
170 /* Stack for visited nodes. */
173 /* The variable partition map. */
176 /* Edge being eliminated by this graph. */
179 /* List of constant copies to emit. These are pushed on in pairs. */
180 vec
<int> const_dests
;
181 vec
<tree
> const_copies
;
183 /* Source locations for any constant copies. */
184 vec
<source_location
> copy_locus
;
188 /* For an edge E find out a good source location to associate with
189 instructions inserted on edge E. If E has an implicit goto set,
190 use its location. Otherwise search instructions in predecessors
191 of E for a location, and use that one. That makes sense because
192 we insert on edges for PHI nodes, and effects of PHIs happen on
193 the end of the predecessor conceptually. */
196 set_location_for_edge (edge e
)
200 set_curr_insn_location (e
->goto_locus
);
204 basic_block bb
= e
->src
;
205 gimple_stmt_iterator gsi
;
209 for (gsi
= gsi_last_bb (bb
); !gsi_end_p (gsi
); gsi_prev (&gsi
))
211 gimple stmt
= gsi_stmt (gsi
);
212 if (is_gimple_debug (stmt
))
214 if (gimple_has_location (stmt
) || gimple_block (stmt
))
216 set_curr_insn_location (gimple_location (stmt
));
220 /* Nothing found in this basic block. Make a half-assed attempt
221 to continue with another block. */
222 if (single_pred_p (bb
))
223 bb
= single_pred (bb
);
227 while (bb
!= e
->src
);
231 /* Emit insns to copy SRC into DEST converting SRC if necessary. As
232 SRC/DEST might be BLKmode memory locations SIZEEXP is a tree from
233 which we deduce the size to copy in that case. */
235 static inline rtx_insn
*
236 emit_partition_copy (rtx dest
, rtx src
, int unsignedsrcp
, tree sizeexp
)
240 if (GET_MODE (src
) != VOIDmode
&& GET_MODE (src
) != GET_MODE (dest
))
241 src
= convert_to_mode (GET_MODE (dest
), src
, unsignedsrcp
);
242 if (GET_MODE (src
) == BLKmode
)
244 gcc_assert (GET_MODE (dest
) == BLKmode
);
245 emit_block_move (dest
, src
, expr_size (sizeexp
), BLOCK_OP_NORMAL
);
248 emit_move_insn (dest
, src
);
250 rtx_insn
*seq
= get_insns ();
256 /* Insert a copy instruction from partition SRC to DEST onto edge E. */
259 insert_partition_copy_on_edge (edge e
, int dest
, int src
, source_location locus
)
262 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
265 "Inserting a partition copy on edge BB%d->BB%d :"
268 e
->dest
->index
, dest
, src
);
269 fprintf (dump_file
, "\n");
272 gcc_assert (SA
.partition_to_pseudo
[dest
]);
273 gcc_assert (SA
.partition_to_pseudo
[src
]);
275 set_location_for_edge (e
);
276 /* If a locus is provided, override the default. */
278 set_curr_insn_location (locus
);
280 var
= partition_to_var (SA
.map
, src
);
281 rtx_insn
*seq
= emit_partition_copy (copy_rtx (SA
.partition_to_pseudo
[dest
]),
282 copy_rtx (SA
.partition_to_pseudo
[src
]),
283 TYPE_UNSIGNED (TREE_TYPE (var
)),
286 insert_insn_on_edge (seq
, e
);
289 /* Insert a copy instruction from expression SRC to partition DEST
293 insert_value_copy_on_edge (edge e
, int dest
, tree src
, source_location locus
)
295 rtx dest_rtx
, seq
, x
;
296 machine_mode dest_mode
, src_mode
;
299 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
302 "Inserting a value copy on edge BB%d->BB%d : PART.%d = ",
304 e
->dest
->index
, dest
);
305 print_generic_expr (dump_file
, src
, TDF_SLIM
);
306 fprintf (dump_file
, "\n");
309 dest_rtx
= copy_rtx (SA
.partition_to_pseudo
[dest
]);
310 gcc_assert (dest_rtx
);
312 set_location_for_edge (e
);
313 /* If a locus is provided, override the default. */
315 set_curr_insn_location (locus
);
319 tree name
= partition_to_var (SA
.map
, dest
);
320 src_mode
= TYPE_MODE (TREE_TYPE (src
));
321 dest_mode
= GET_MODE (dest_rtx
);
322 gcc_assert (src_mode
== TYPE_MODE (TREE_TYPE (name
)));
323 gcc_assert (!REG_P (dest_rtx
)
324 || dest_mode
== promote_ssa_mode (name
, &unsignedp
));
326 if (src_mode
!= dest_mode
)
328 x
= expand_expr (src
, NULL
, src_mode
, EXPAND_NORMAL
);
329 x
= convert_modes (dest_mode
, src_mode
, x
, unsignedp
);
331 else if (src_mode
== BLKmode
)
334 store_expr (src
, x
, 0, false);
337 x
= expand_expr (src
, dest_rtx
, dest_mode
, EXPAND_NORMAL
);
340 emit_move_insn (dest_rtx
, x
);
344 insert_insn_on_edge (seq
, e
);
347 /* Insert a copy instruction from RTL expression SRC to partition DEST
351 insert_rtx_to_part_on_edge (edge e
, int dest
, rtx src
, int unsignedsrcp
,
352 source_location locus
)
354 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
357 "Inserting a temp copy on edge BB%d->BB%d : PART.%d = ",
359 e
->dest
->index
, dest
);
360 print_simple_rtl (dump_file
, src
);
361 fprintf (dump_file
, "\n");
364 gcc_assert (SA
.partition_to_pseudo
[dest
]);
366 set_location_for_edge (e
);
367 /* If a locus is provided, override the default. */
369 set_curr_insn_location (locus
);
371 /* We give the destination as sizeexp in case src/dest are BLKmode
372 mems. Usually we give the source. As we result from SSA names
373 the left and right size should be the same (and no WITH_SIZE_EXPR
374 involved), so it doesn't matter. */
375 rtx_insn
*seq
= emit_partition_copy (copy_rtx (SA
.partition_to_pseudo
[dest
]),
377 partition_to_var (SA
.map
, dest
));
379 insert_insn_on_edge (seq
, e
);
382 /* Insert a copy instruction from partition SRC to RTL lvalue DEST
386 insert_part_to_rtx_on_edge (edge e
, rtx dest
, int src
, source_location locus
)
389 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
392 "Inserting a temp copy on edge BB%d->BB%d : ",
395 print_simple_rtl (dump_file
, dest
);
396 fprintf (dump_file
, "= PART.%d\n", src
);
399 gcc_assert (SA
.partition_to_pseudo
[src
]);
401 set_location_for_edge (e
);
402 /* If a locus is provided, override the default. */
404 set_curr_insn_location (locus
);
406 var
= partition_to_var (SA
.map
, src
);
407 rtx_insn
*seq
= emit_partition_copy (dest
,
408 copy_rtx (SA
.partition_to_pseudo
[src
]),
409 TYPE_UNSIGNED (TREE_TYPE (var
)),
412 insert_insn_on_edge (seq
, e
);
416 /* Create an elimination graph with SIZE nodes and associated data
420 new_elim_graph (int size
)
422 elim_graph g
= (elim_graph
) xmalloc (sizeof (struct _elim_graph
));
424 g
->nodes
.create (30);
425 g
->const_dests
.create (20);
426 g
->const_copies
.create (20);
427 g
->copy_locus
.create (10);
428 g
->edge_list
.create (20);
429 g
->edge_locus
.create (10);
430 g
->stack
.create (30);
432 g
->visited
= sbitmap_alloc (size
);
438 /* Empty elimination graph G. */
441 clear_elim_graph (elim_graph g
)
443 g
->nodes
.truncate (0);
444 g
->edge_list
.truncate (0);
445 g
->edge_locus
.truncate (0);
449 /* Delete elimination graph G. */
452 delete_elim_graph (elim_graph g
)
454 sbitmap_free (g
->visited
);
456 g
->edge_list
.release ();
457 g
->const_copies
.release ();
458 g
->const_dests
.release ();
460 g
->copy_locus
.release ();
461 g
->edge_locus
.release ();
467 /* Return the number of nodes in graph G. */
470 elim_graph_size (elim_graph g
)
472 return g
->nodes
.length ();
476 /* Add NODE to graph G, if it doesn't exist already. */
479 elim_graph_add_node (elim_graph g
, int node
)
484 FOR_EACH_VEC_ELT (g
->nodes
, x
, t
)
487 g
->nodes
.safe_push (node
);
491 /* Add the edge PRED->SUCC to graph G. */
494 elim_graph_add_edge (elim_graph g
, int pred
, int succ
, source_location locus
)
496 g
->edge_list
.safe_push (pred
);
497 g
->edge_list
.safe_push (succ
);
498 g
->edge_locus
.safe_push (locus
);
502 /* Remove an edge from graph G for which NODE is the predecessor, and
503 return the successor node. -1 is returned if there is no such edge. */
506 elim_graph_remove_succ_edge (elim_graph g
, int node
, source_location
*locus
)
510 for (x
= 0; x
< g
->edge_list
.length (); x
+= 2)
511 if (g
->edge_list
[x
] == node
)
513 g
->edge_list
[x
] = -1;
514 y
= g
->edge_list
[x
+ 1];
515 g
->edge_list
[x
+ 1] = -1;
516 *locus
= g
->edge_locus
[x
/ 2];
517 g
->edge_locus
[x
/ 2] = UNKNOWN_LOCATION
;
520 *locus
= UNKNOWN_LOCATION
;
525 /* Find all the nodes in GRAPH which are successors to NODE in the
526 edge list. VAR will hold the partition number found. CODE is the
527 code fragment executed for every node found. */
529 #define FOR_EACH_ELIM_GRAPH_SUCC(GRAPH, NODE, VAR, LOCUS, CODE) \
533 for (x_ = 0; x_ < (GRAPH)->edge_list.length (); x_ += 2) \
535 y_ = (GRAPH)->edge_list[x_]; \
538 (void) ((VAR) = (GRAPH)->edge_list[x_ + 1]); \
539 (void) ((LOCUS) = (GRAPH)->edge_locus[x_ / 2]); \
545 /* Find all the nodes which are predecessors of NODE in the edge list for
546 GRAPH. VAR will hold the partition number found. CODE is the
547 code fragment executed for every node found. */
549 #define FOR_EACH_ELIM_GRAPH_PRED(GRAPH, NODE, VAR, LOCUS, CODE) \
553 for (x_ = 0; x_ < (GRAPH)->edge_list.length (); x_ += 2) \
555 y_ = (GRAPH)->edge_list[x_ + 1]; \
558 (void) ((VAR) = (GRAPH)->edge_list[x_]); \
559 (void) ((LOCUS) = (GRAPH)->edge_locus[x_ / 2]); \
565 /* Add T to elimination graph G. */
568 eliminate_name (elim_graph g
, int T
)
570 elim_graph_add_node (g
, T
);
573 /* Return true if this phi argument T should have a copy queued when using
574 var_map MAP. PHI nodes should contain only ssa_names and invariants. A
575 test for ssa_name is definitely simpler, but don't let invalid contents
576 slip through in the meantime. */
579 queue_phi_copy_p (var_map map
, tree t
)
581 if (TREE_CODE (t
) == SSA_NAME
)
583 if (var_to_partition (map
, t
) == NO_PARTITION
)
587 gcc_checking_assert (is_gimple_min_invariant (t
));
591 /* Build elimination graph G for basic block BB on incoming PHI edge
595 eliminate_build (elim_graph g
)
601 clear_elim_graph (g
);
603 for (gsi
= gsi_start_phis (g
->e
->dest
); !gsi_end_p (gsi
); gsi_next (&gsi
))
605 gphi
*phi
= gsi
.phi ();
606 source_location locus
;
608 p0
= var_to_partition (g
->map
, gimple_phi_result (phi
));
609 /* Ignore results which are not in partitions. */
610 if (p0
== NO_PARTITION
)
613 Ti
= PHI_ARG_DEF (phi
, g
->e
->dest_idx
);
614 locus
= gimple_phi_arg_location_from_edge (phi
, g
->e
);
616 /* If this argument is a constant, or a SSA_NAME which is being
617 left in SSA form, just queue a copy to be emitted on this
619 if (queue_phi_copy_p (g
->map
, Ti
))
621 /* Save constant copies until all other copies have been emitted
623 g
->const_dests
.safe_push (p0
);
624 g
->const_copies
.safe_push (Ti
);
625 g
->copy_locus
.safe_push (locus
);
629 pi
= var_to_partition (g
->map
, Ti
);
632 eliminate_name (g
, p0
);
633 eliminate_name (g
, pi
);
634 elim_graph_add_edge (g
, p0
, pi
, locus
);
641 /* Push successors of T onto the elimination stack for G. */
644 elim_forward (elim_graph g
, int T
)
647 source_location locus
;
649 bitmap_set_bit (g
->visited
, T
);
650 FOR_EACH_ELIM_GRAPH_SUCC (g
, T
, S
, locus
,
652 if (!bitmap_bit_p (g
->visited
, S
))
655 g
->stack
.safe_push (T
);
659 /* Return 1 if there unvisited predecessors of T in graph G. */
662 elim_unvisited_predecessor (elim_graph g
, int T
)
665 source_location locus
;
667 FOR_EACH_ELIM_GRAPH_PRED (g
, T
, P
, locus
,
669 if (!bitmap_bit_p (g
->visited
, P
))
675 /* Process predecessors first, and insert a copy. */
678 elim_backward (elim_graph g
, int T
)
681 source_location locus
;
683 bitmap_set_bit (g
->visited
, T
);
684 FOR_EACH_ELIM_GRAPH_PRED (g
, T
, P
, locus
,
686 if (!bitmap_bit_p (g
->visited
, P
))
688 elim_backward (g
, P
);
689 insert_partition_copy_on_edge (g
->e
, P
, T
, locus
);
694 /* Allocate a new pseudo register usable for storing values sitting
695 in NAME (a decl or SSA name), i.e. with matching mode and attributes. */
698 get_temp_reg (tree name
)
700 tree type
= TREE_TYPE (name
);
702 machine_mode reg_mode
= promote_ssa_mode (name
, &unsignedp
);
703 rtx x
= gen_reg_rtx (reg_mode
);
704 if (POINTER_TYPE_P (type
))
705 mark_reg_pointer (x
, TYPE_ALIGN (TREE_TYPE (type
)));
709 /* Insert required copies for T in graph G. Check for a strongly connected
710 region, and create a temporary to break the cycle if one is found. */
713 elim_create (elim_graph g
, int T
)
716 source_location locus
;
718 if (elim_unvisited_predecessor (g
, T
))
720 tree var
= partition_to_var (g
->map
, T
);
721 rtx U
= get_temp_reg (var
);
722 int unsignedsrcp
= TYPE_UNSIGNED (TREE_TYPE (var
));
724 insert_part_to_rtx_on_edge (g
->e
, U
, T
, UNKNOWN_LOCATION
);
725 FOR_EACH_ELIM_GRAPH_PRED (g
, T
, P
, locus
,
727 if (!bitmap_bit_p (g
->visited
, P
))
729 elim_backward (g
, P
);
730 insert_rtx_to_part_on_edge (g
->e
, P
, U
, unsignedsrcp
, locus
);
736 S
= elim_graph_remove_succ_edge (g
, T
, &locus
);
739 bitmap_set_bit (g
->visited
, T
);
740 insert_partition_copy_on_edge (g
->e
, T
, S
, locus
);
746 /* Eliminate all the phi nodes on edge E in graph G. */
749 eliminate_phi (edge e
, elim_graph g
)
753 gcc_assert (g
->const_copies
.length () == 0);
754 gcc_assert (g
->copy_locus
.length () == 0);
756 /* Abnormal edges already have everything coalesced. */
757 if (e
->flags
& EDGE_ABNORMAL
)
764 if (elim_graph_size (g
) != 0)
768 bitmap_clear (g
->visited
);
769 g
->stack
.truncate (0);
771 FOR_EACH_VEC_ELT (g
->nodes
, x
, part
)
773 if (!bitmap_bit_p (g
->visited
, part
))
774 elim_forward (g
, part
);
777 bitmap_clear (g
->visited
);
778 while (g
->stack
.length () > 0)
781 if (!bitmap_bit_p (g
->visited
, x
))
786 /* If there are any pending constant copies, issue them now. */
787 while (g
->const_copies
.length () > 0)
791 source_location locus
;
793 src
= g
->const_copies
.pop ();
794 dest
= g
->const_dests
.pop ();
795 locus
= g
->copy_locus
.pop ();
796 insert_value_copy_on_edge (e
, dest
, src
, locus
);
801 /* Remove each argument from PHI. If an arg was the last use of an SSA_NAME,
802 check to see if this allows another PHI node to be removed. */
805 remove_gimple_phi_args (gphi
*phi
)
810 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
812 fprintf (dump_file
, "Removing Dead PHI definition: ");
813 print_gimple_stmt (dump_file
, phi
, 0, TDF_SLIM
);
816 FOR_EACH_PHI_ARG (arg_p
, phi
, iter
, SSA_OP_USE
)
818 tree arg
= USE_FROM_PTR (arg_p
);
819 if (TREE_CODE (arg
) == SSA_NAME
)
821 /* Remove the reference to the existing argument. */
822 SET_USE (arg_p
, NULL_TREE
);
823 if (has_zero_uses (arg
))
826 gimple_stmt_iterator gsi
;
828 stmt
= SSA_NAME_DEF_STMT (arg
);
830 /* Also remove the def if it is a PHI node. */
831 if (gimple_code (stmt
) == GIMPLE_PHI
)
833 remove_gimple_phi_args (as_a
<gphi
*> (stmt
));
834 gsi
= gsi_for_stmt (stmt
);
835 remove_phi_node (&gsi
, true);
843 /* Remove any PHI node which is a virtual PHI, or a PHI with no uses. */
846 eliminate_useless_phis (void)
852 FOR_EACH_BB_FN (bb
, cfun
)
854 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); )
856 gphi
*phi
= gsi
.phi ();
857 result
= gimple_phi_result (phi
);
858 if (virtual_operand_p (result
))
860 #ifdef ENABLE_CHECKING
862 /* There should be no arguments which are not virtual, or the
863 results will be incorrect. */
864 for (i
= 0; i
< gimple_phi_num_args (phi
); i
++)
866 tree arg
= PHI_ARG_DEF (phi
, i
);
867 if (TREE_CODE (arg
) == SSA_NAME
868 && !virtual_operand_p (arg
))
870 fprintf (stderr
, "Argument of PHI is not virtual (");
871 print_generic_expr (stderr
, arg
, TDF_SLIM
);
872 fprintf (stderr
, "), but the result is :");
873 print_gimple_stmt (stderr
, phi
, 0, TDF_SLIM
);
874 internal_error ("SSA corruption");
878 remove_phi_node (&gsi
, true);
882 /* Also remove real PHIs with no uses. */
883 if (has_zero_uses (result
))
885 remove_gimple_phi_args (phi
);
886 remove_phi_node (&gsi
, true);
896 /* This function will rewrite the current program using the variable mapping
897 found in MAP. If the replacement vector VALUES is provided, any
898 occurrences of partitions with non-null entries in the vector will be
899 replaced with the expression in the vector instead of its mapped
903 rewrite_trees (var_map map ATTRIBUTE_UNUSED
)
905 #ifdef ENABLE_CHECKING
907 /* Search for PHIs where the destination has no partition, but one
908 or more arguments has a partition. This should not happen and can
909 create incorrect code. */
910 FOR_EACH_BB_FN (bb
, cfun
)
913 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
915 gphi
*phi
= gsi
.phi ();
916 tree T0
= var_to_partition_to_var (map
, gimple_phi_result (phi
));
920 for (i
= 0; i
< gimple_phi_num_args (phi
); i
++)
922 tree arg
= PHI_ARG_DEF (phi
, i
);
924 if (TREE_CODE (arg
) == SSA_NAME
925 && var_to_partition (map
, arg
) != NO_PARTITION
)
927 fprintf (stderr
, "Argument of PHI is in a partition :(");
928 print_generic_expr (stderr
, arg
, TDF_SLIM
);
929 fprintf (stderr
, "), but the result is not :");
930 print_gimple_stmt (stderr
, phi
, 0, TDF_SLIM
);
931 internal_error ("SSA corruption");
940 /* Given the out-of-ssa info object SA (with prepared partitions)
941 eliminate all phi nodes in all basic blocks. Afterwards no
942 basic block will have phi nodes anymore and there are possibly
943 some RTL instructions inserted on edges. */
946 expand_phi_nodes (struct ssaexpand
*sa
)
949 elim_graph g
= new_elim_graph (sa
->map
->num_partitions
);
952 FOR_BB_BETWEEN (bb
, ENTRY_BLOCK_PTR_FOR_FN (cfun
)->next_bb
,
953 EXIT_BLOCK_PTR_FOR_FN (cfun
), next_bb
)
954 if (!gimple_seq_empty_p (phi_nodes (bb
)))
958 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
959 eliminate_phi (e
, g
);
960 set_phi_nodes (bb
, NULL
);
961 /* We can't redirect EH edges in RTL land, so we need to do this
962 here. Redirection happens only when splitting is necessary,
963 which it is only for critical edges, normally. For EH edges
964 it might also be necessary when the successor has more than
965 one predecessor. In that case the edge is either required to
966 be fallthru (which EH edges aren't), or the predecessor needs
967 to end with a jump (which again, isn't the case with EH edges).
968 Hence, split all EH edges on which we inserted instructions
969 and whose successor has multiple predecessors. */
970 for (ei
= ei_start (bb
->preds
); (e
= ei_safe_edge (ei
)); )
972 if (e
->insns
.r
&& (e
->flags
& EDGE_EH
)
973 && !single_pred_p (e
->dest
))
975 rtx_insn
*insns
= e
->insns
.r
;
979 single_pred_edge (bb
)->insns
.r
= insns
;
986 delete_elim_graph (g
);
990 /* Remove the ssa-names in the current function and translate them into normal
991 compiler variables. PERFORM_TER is true if Temporary Expression Replacement
992 should also be used. */
995 remove_ssa_form (bool perform_ter
, struct ssaexpand
*sa
)
997 bitmap values
= NULL
;
1001 map
= coalesce_ssa_name ();
1003 /* Return to viewing the variable list as just all reference variables after
1004 coalescing has been performed. */
1005 partition_view_normal (map
);
1007 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1009 fprintf (dump_file
, "After Coalescing:\n");
1010 dump_var_map (dump_file
, map
);
1015 values
= find_replaceable_exprs (map
);
1016 if (values
&& dump_file
&& (dump_flags
& TDF_DETAILS
))
1017 dump_replaceable_exprs (dump_file
, values
);
1020 rewrite_trees (map
);
1023 sa
->values
= values
;
1024 sa
->partition_has_default_def
= BITMAP_ALLOC (NULL
);
1025 for (i
= 1; i
< num_ssa_names
; i
++)
1027 tree t
= ssa_name (i
);
1028 if (t
&& SSA_NAME_IS_DEFAULT_DEF (t
))
1030 int p
= var_to_partition (map
, t
);
1031 if (p
!= NO_PARTITION
)
1032 bitmap_set_bit (sa
->partition_has_default_def
, p
);
1038 /* If not already done so for basic block BB, assign increasing uids
1039 to each of its instructions. */
1042 maybe_renumber_stmts_bb (basic_block bb
)
1045 gimple_stmt_iterator gsi
;
1050 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1052 gimple stmt
= gsi_stmt (gsi
);
1053 gimple_set_uid (stmt
, i
);
1059 /* Return true if we can determine that the SSA_NAMEs RESULT (a result
1060 of a PHI node) and ARG (one of its arguments) conflict. Return false
1061 otherwise, also when we simply aren't sure. */
1064 trivially_conflicts_p (basic_block bb
, tree result
, tree arg
)
1067 imm_use_iterator imm_iter
;
1068 gimple defa
= SSA_NAME_DEF_STMT (arg
);
1070 /* If ARG isn't defined in the same block it's too complicated for
1072 if (gimple_bb (defa
) != bb
)
1075 FOR_EACH_IMM_USE_FAST (use
, imm_iter
, result
)
1077 gimple use_stmt
= USE_STMT (use
);
1078 if (is_gimple_debug (use_stmt
))
1080 /* Now, if there's a use of RESULT that lies outside this basic block,
1081 then there surely is a conflict with ARG. */
1082 if (gimple_bb (use_stmt
) != bb
)
1084 if (gimple_code (use_stmt
) == GIMPLE_PHI
)
1086 /* The use now is in a real stmt of BB, so if ARG was defined
1087 in a PHI node (like RESULT) both conflict. */
1088 if (gimple_code (defa
) == GIMPLE_PHI
)
1090 maybe_renumber_stmts_bb (bb
);
1091 /* If the use of RESULT occurs after the definition of ARG,
1092 the two conflict too. */
1093 if (gimple_uid (defa
) < gimple_uid (use_stmt
))
1101 /* Search every PHI node for arguments associated with backedges which
1102 we can trivially determine will need a copy (the argument is either
1103 not an SSA_NAME or the argument has a different underlying variable
1104 than the PHI result).
1106 Insert a copy from the PHI argument to a new destination at the
1107 end of the block with the backedge to the top of the loop. Update
1108 the PHI argument to reference this new destination. */
1111 insert_backedge_copies (void)
1116 mark_dfs_back_edges ();
1118 FOR_EACH_BB_FN (bb
, cfun
)
1120 /* Mark block as possibly needing calculation of UIDs. */
1123 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1125 gphi
*phi
= gsi
.phi ();
1126 tree result
= gimple_phi_result (phi
);
1129 if (virtual_operand_p (result
))
1132 for (i
= 0; i
< gimple_phi_num_args (phi
); i
++)
1134 tree arg
= gimple_phi_arg_def (phi
, i
);
1135 edge e
= gimple_phi_arg_edge (phi
, i
);
1137 /* If the argument is not an SSA_NAME, then we will need a
1138 constant initialization. If the argument is an SSA_NAME with
1139 a different underlying variable then a copy statement will be
1141 if ((e
->flags
& EDGE_DFS_BACK
)
1142 && (TREE_CODE (arg
) != SSA_NAME
1143 || SSA_NAME_VAR (arg
) != SSA_NAME_VAR (result
)
1144 || trivially_conflicts_p (bb
, result
, arg
)))
1149 gimple_stmt_iterator gsi2
;
1151 gsi2
= gsi_last_bb (gimple_phi_arg_edge (phi
, i
)->src
);
1152 if (!gsi_end_p (gsi2
))
1153 last
= gsi_stmt (gsi2
);
1155 /* In theory the only way we ought to get back to the
1156 start of a loop should be with a COND_EXPR or GOTO_EXPR.
1157 However, better safe than sorry.
1158 If the block ends with a control statement or
1159 something that might throw, then we have to
1160 insert this assignment before the last
1161 statement. Else insert it after the last statement. */
1162 if (last
&& stmt_ends_bb_p (last
))
1164 /* If the last statement in the block is the definition
1165 site of the PHI argument, then we can't insert
1166 anything after it. */
1167 if (TREE_CODE (arg
) == SSA_NAME
1168 && SSA_NAME_DEF_STMT (arg
) == last
)
1172 /* Create a new instance of the underlying variable of the
1174 name
= copy_ssa_name (result
);
1175 stmt
= gimple_build_assign (name
,
1176 gimple_phi_arg_def (phi
, i
));
1178 /* copy location if present. */
1179 if (gimple_phi_arg_has_location (phi
, i
))
1180 gimple_set_location (stmt
,
1181 gimple_phi_arg_location (phi
, i
));
1183 /* Insert the new statement into the block and update
1185 if (last
&& stmt_ends_bb_p (last
))
1186 gsi_insert_before (&gsi2
, stmt
, GSI_NEW_STMT
);
1188 gsi_insert_after (&gsi2
, stmt
, GSI_NEW_STMT
);
1189 SET_PHI_ARG_DEF (phi
, i
, name
);
1194 /* Unmark this block again. */
1199 /* Free all memory associated with going out of SSA form. SA is
1200 the outof-SSA info object. */
1203 finish_out_of_ssa (struct ssaexpand
*sa
)
1205 free (sa
->partition_to_pseudo
);
1207 BITMAP_FREE (sa
->values
);
1208 delete_var_map (sa
->map
);
1209 BITMAP_FREE (sa
->partition_has_default_def
);
1210 memset (sa
, 0, sizeof *sa
);
1213 /* Take the current function out of SSA form, translating PHIs as described in
1214 R. Morgan, ``Building an Optimizing Compiler'',
1215 Butterworth-Heinemann, Boston, MA, 1998. pp 176-186. */
1218 rewrite_out_of_ssa (struct ssaexpand
*sa
)
1220 /* If elimination of a PHI requires inserting a copy on a backedge,
1221 then we will have to split the backedge which has numerous
1222 undesirable performance effects.
1224 A significant number of such cases can be handled here by inserting
1225 copies into the loop itself. */
1226 insert_backedge_copies ();
1229 /* Eliminate PHIs which are of no use, such as virtual or dead phis. */
1230 eliminate_useless_phis ();
1232 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1233 gimple_dump_cfg (dump_file
, dump_flags
& ~TDF_DETAILS
);
1235 remove_ssa_form (flag_tree_ter
, sa
);
1237 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1238 gimple_dump_cfg (dump_file
, dump_flags
& ~TDF_DETAILS
);