1 /* Conditional constant propagation pass for the GNU compiler.
2 Copyright (C) 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
3 Adapted from original RTL SSA-CCP by Daniel Berlin <dberlin@dberlin.org>
4 Adapted to GIMPLE trees by Diego Novillo <dnovillo@redhat.com>
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it
9 under the terms of the GNU General Public License as published by the
10 Free Software Foundation; either version 2, or (at your option) any
13 GCC is distributed in the hope that it will be useful, but WITHOUT
14 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING. If not, write to the Free
20 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
23 /* Conditional constant propagation.
27 Constant propagation with conditional branches,
28 Wegman and Zadeck, ACM TOPLAS 13(2):181-210.
30 Building an Optimizing Compiler,
31 Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9.
33 Advanced Compiler Design and Implementation,
34 Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */
38 #include "coretypes.h"
45 #include "basic-block.h"
50 #include "diagnostic.h"
52 #include "tree-dump.h"
53 #include "tree-flow.h"
54 #include "tree-pass.h"
55 #include "tree-ssa-propagate.h"
56 #include "langhooks.h"
59 /* Possible lattice values. */
69 /* Main structure for CCP. Contains the lattice value and, if it's a
70 constant, the constant value. */
73 latticevalue lattice_val;
77 /* This is used to track the current value of each variable. */
78 static value *value_vector;
81 /* Dump lattice value VAL to file OUTF prefixed by PREFIX. */
84 dump_lattice_value (FILE *outf, const char *prefix, value val)
86 switch (val.lattice_val)
89 fprintf (outf, "%sUNDEFINED", prefix);
92 fprintf (outf, "%sVARYING", prefix);
95 fprintf (outf, "%sUNKNOWN_VAL", prefix);
98 fprintf (outf, "%sCONSTANT ", prefix);
99 print_generic_expr (outf, val.const_val, dump_flags);
107 /* Return a default value for variable VAR using the following rules:
109 1- Function arguments are considered VARYING.
111 2- Global and static variables that are declared constant are
114 3- Any other virtually defined variable is considered UNKNOWN_VAL.
116 4- Any other value is considered UNDEFINED. This is useful when
117 considering PHI nodes. PHI arguments that are undefined do not
118 change the constant value of the PHI node, which allows for more
119 constants to be propagated. */
122 get_default_value (tree var)
127 if (TREE_CODE (var) == SSA_NAME)
128 sym = SSA_NAME_VAR (var);
131 gcc_assert (DECL_P (var));
135 val.lattice_val = UNDEFINED;
136 val.const_val = NULL_TREE;
138 if (TREE_CODE (var) == SSA_NAME
139 && SSA_NAME_VALUE (var)
140 && is_gimple_min_invariant (SSA_NAME_VALUE (var)))
142 val.lattice_val = CONSTANT;
143 val.const_val = SSA_NAME_VALUE (var);
145 else if (TREE_CODE (sym) == PARM_DECL || TREE_THIS_VOLATILE (sym))
147 /* Function arguments and volatile variables are considered VARYING. */
148 val.lattice_val = VARYING;
150 else if (TREE_STATIC (sym))
152 /* Globals and static variables are considered UNKNOWN_VAL,
153 unless they are declared 'const'. */
154 if (TREE_READONLY (sym)
155 && DECL_INITIAL (sym)
156 && is_gimple_min_invariant (DECL_INITIAL (sym)))
158 val.lattice_val = CONSTANT;
159 val.const_val = DECL_INITIAL (sym);
163 val.const_val = NULL_TREE;
164 val.lattice_val = UNKNOWN_VAL;
167 else if (!is_gimple_reg (sym))
169 val.const_val = NULL_TREE;
170 val.lattice_val = UNKNOWN_VAL;
175 tree stmt = SSA_NAME_DEF_STMT (var);
177 if (!IS_EMPTY_STMT (stmt))
179 code = TREE_CODE (stmt);
180 if (code != MODIFY_EXPR && code != PHI_NODE)
181 val.lattice_val = VARYING;
188 /* Get the constant value associated with variable VAR. */
195 gcc_assert (TREE_CODE (var) == SSA_NAME);
197 val = &value_vector[SSA_NAME_VERSION (var)];
198 if (val->lattice_val == UNINITIALIZED)
199 *val = get_default_value (var);
205 /* Set the lattice value for variable VAR to VAL. Return true if VAL
206 is different from VAR's previous value. */
209 set_lattice_value (tree var, value val)
211 value *old = get_value (var);
213 if (val.lattice_val == UNDEFINED)
215 /* CONSTANT->UNDEFINED is never a valid state transition. */
216 gcc_assert (old->lattice_val != CONSTANT);
218 /* UNKNOWN_VAL->UNDEFINED is never a valid state transition. */
219 gcc_assert (old->lattice_val != UNKNOWN_VAL);
221 /* VARYING->UNDEFINED is generally not a valid state transition,
222 except for values which are initialized to VARYING. */
223 gcc_assert (old->lattice_val != VARYING
224 || get_default_value (var).lattice_val == VARYING);
226 else if (val.lattice_val == CONSTANT)
227 /* VARYING -> CONSTANT is an invalid state transition, except
228 for objects which start off in a VARYING state. */
229 gcc_assert (old->lattice_val != VARYING
230 || get_default_value (var).lattice_val == VARYING);
232 /* If the constant for VAR has changed, then this VAR is really varying. */
233 if (old->lattice_val == CONSTANT
234 && val.lattice_val == CONSTANT
235 && !simple_cst_equal (old->const_val, val.const_val))
237 val.lattice_val = VARYING;
238 val.const_val = NULL_TREE;
241 if (old->lattice_val != val.lattice_val)
243 if (dump_file && (dump_flags & TDF_DETAILS))
245 dump_lattice_value (dump_file, "Lattice value changed to ", val);
246 fprintf (dump_file, ". Adding definition to SSA edges.\n");
257 /* Set the lattice value for the variable VAR to VARYING. */
260 def_to_varying (tree var)
263 val.lattice_val = VARYING;
264 val.const_val = NULL_TREE;
265 set_lattice_value (var, val);
269 /* Return the likely latticevalue for STMT.
271 If STMT has no operands, then return CONSTANT.
273 Else if any operands of STMT are undefined, then return UNDEFINED.
275 Else if any operands of STMT are constants, then return CONSTANT.
277 Else return VARYING. */
280 likely_value (tree stmt)
283 int found_constant = 0;
288 /* If the statement makes aliased loads or has volatile operands, it
289 won't fold to a constant value. */
290 ann = stmt_ann (stmt);
291 if (ann->makes_aliased_loads || ann->has_volatile_ops)
294 /* A CALL_EXPR is assumed to be varying. This may be overly conservative,
295 in the presence of const and pure calls. */
296 if (get_call_expr_in (stmt) != NULL_TREE)
299 get_stmt_operands (stmt);
301 FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
303 value *val = get_value (use);
305 if (val->lattice_val == UNDEFINED)
308 if (val->lattice_val == CONSTANT)
312 vuses = VUSE_OPS (ann);
314 if (NUM_VUSES (vuses))
316 tree vuse = VUSE_OP (vuses, 0);
317 value *val = get_value (vuse);
319 if (val->lattice_val == UNKNOWN_VAL)
322 /* There should be no VUSE operands that are UNDEFINED. */
323 gcc_assert (val->lattice_val != UNDEFINED);
325 if (val->lattice_val == CONSTANT)
329 return ((found_constant || (!USE_OPS (ann) && !vuses)) ? CONSTANT : VARYING);
333 /* Function indicating whether we ought to include information for VAR
334 when calculating immediate uses. */
337 need_imm_uses_for (tree var)
339 return get_value (var)->lattice_val != VARYING;
343 /* Initialize local data structures for CCP. */
346 ccp_initialize (void)
351 value_vector = (value *) xmalloc (num_ssa_names * sizeof (value));
352 memset (value_vector, 0, num_ssa_names * sizeof (value));
354 /* Set of SSA_NAMEs that are defined by a V_MAY_DEF. */
355 is_may_def = sbitmap_alloc (num_ssa_names);
356 sbitmap_zero (is_may_def);
358 /* Initialize simulation flags for PHI nodes and statements. */
361 block_stmt_iterator i;
363 /* Mark all V_MAY_DEF operands VARYING. */
364 for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
366 bool is_varying = false;
367 tree stmt = bsi_stmt (i);
371 get_stmt_operands (stmt);
373 /* Get the default value for each DEF and V_MUST_DEF. */
374 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter,
375 (SSA_OP_DEF | SSA_OP_VMUSTDEF))
377 if (get_value (def)->lattice_val == VARYING)
381 /* Mark all V_MAY_DEF operands VARYING. */
382 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_VMAYDEF)
384 get_value (def)->lattice_val = VARYING;
385 SET_BIT (is_may_def, SSA_NAME_VERSION (def));
388 /* Statements other than MODIFY_EXPR, COND_EXPR and
389 SWITCH_EXPR are not interesting for constant propagation.
390 Mark them VARYING. */
391 if (TREE_CODE (stmt) != MODIFY_EXPR
392 && TREE_CODE (stmt) != COND_EXPR
393 && TREE_CODE (stmt) != SWITCH_EXPR)
396 DONT_SIMULATE_AGAIN (stmt) = is_varying;
400 /* Now process PHI nodes. */
406 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
408 value *val = get_value (PHI_RESULT (phi));
410 for (x = 0; x < PHI_NUM_ARGS (phi); x++)
412 var = PHI_ARG_DEF (phi, x);
414 /* If one argument has a V_MAY_DEF, the result is
416 if (TREE_CODE (var) == SSA_NAME)
418 if (TEST_BIT (is_may_def, SSA_NAME_VERSION (var)))
420 val->lattice_val = VARYING;
421 SET_BIT (is_may_def, SSA_NAME_VERSION (PHI_RESULT (phi)));
427 DONT_SIMULATE_AGAIN (phi) = (val->lattice_val == VARYING);
431 sbitmap_free (is_may_def);
433 /* Compute immediate uses for variables we care about. */
434 compute_immediate_uses (TDFA_USE_OPS | TDFA_USE_VOPS, need_imm_uses_for);
438 /* Replace USE references in statement STMT with their immediate reaching
439 definition. Return true if at least one reference was replaced. If
440 REPLACED_ADDRESSES_P is given, it will be set to true if an address
441 constant was replaced. */
444 replace_uses_in (tree stmt, bool *replaced_addresses_p)
446 bool replaced = false;
450 if (replaced_addresses_p)
451 *replaced_addresses_p = false;
453 get_stmt_operands (stmt);
455 FOR_EACH_SSA_USE_OPERAND (use, stmt, iter, SSA_OP_USE)
457 tree tuse = USE_FROM_PTR (use);
458 value *val = get_value (tuse);
460 if (val->lattice_val != CONSTANT)
463 if (TREE_CODE (stmt) == ASM_EXPR
464 && !may_propagate_copy_into_asm (tuse))
467 SET_USE (use, val->const_val);
470 if (POINTER_TYPE_P (TREE_TYPE (tuse)) && replaced_addresses_p)
471 *replaced_addresses_p = true;
478 /* Replace the VUSE references in statement STMT with its immediate reaching
479 definition. Return true if the reference was replaced. If
480 REPLACED_ADDRESSES_P is given, it will be set to true if an address
481 constant was replaced. */
484 replace_vuse_in (tree stmt, bool *replaced_addresses_p)
486 bool replaced = false;
491 if (replaced_addresses_p)
492 *replaced_addresses_p = false;
494 get_stmt_operands (stmt);
496 vuses = STMT_VUSE_OPS (stmt);
498 if (NUM_VUSES (vuses) != 1)
501 vuse = VUSE_OP_PTR (vuses, 0);
502 val = get_value (USE_FROM_PTR (vuse));
504 if (val->lattice_val == CONSTANT
505 && TREE_CODE (stmt) == MODIFY_EXPR
506 && DECL_P (TREE_OPERAND (stmt, 1))
507 && TREE_OPERAND (stmt, 1) == SSA_NAME_VAR (USE_FROM_PTR (vuse)))
509 TREE_OPERAND (stmt, 1) = val->const_val;
511 if (POINTER_TYPE_P (TREE_TYPE (USE_FROM_PTR (vuse)))
512 && replaced_addresses_p)
513 *replaced_addresses_p = true;
520 /* Perform final substitution and folding. After this pass the program
521 should still be in SSA form. */
524 substitute_and_fold (void)
529 if (dump_file && (dump_flags & TDF_DETAILS))
531 "\nSubstituing constants and folding statements\n\n");
533 /* Substitute constants in every statement of every basic block. */
536 block_stmt_iterator i;
539 /* Propagate our known constants into PHI nodes. */
540 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
544 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
547 use_operand_p orig_p = PHI_ARG_DEF_PTR (phi, i);
548 tree orig = USE_FROM_PTR (orig_p);
550 if (! SSA_VAR_P (orig))
553 new_val = get_value (orig);
554 if (new_val->lattice_val == CONSTANT
555 && may_propagate_copy (orig, new_val->const_val))
556 SET_USE (orig_p, new_val->const_val);
560 for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
562 bool replaced_address;
563 tree stmt = bsi_stmt (i);
565 /* Skip statements that have been folded already. */
566 if (stmt_modified_p (stmt) || !is_exec_stmt (stmt))
569 /* Replace the statement with its folded version and mark it
571 if (dump_file && (dump_flags & TDF_DETAILS))
573 fprintf (dump_file, "Line %d: replaced ", get_lineno (stmt));
574 print_generic_stmt (dump_file, stmt, TDF_SLIM);
577 if (replace_uses_in (stmt, &replaced_address)
578 || replace_vuse_in (stmt, &replaced_address))
580 bool changed = fold_stmt (bsi_stmt_ptr (i));
582 /* If we folded a builtin function, we'll likely
583 need to rename VDEFs. */
584 if (replaced_address || changed)
586 mark_new_vars_to_rename (stmt, vars_to_rename);
587 if (maybe_clean_eh_stmt (stmt))
588 tree_purge_dead_eh_edges (bb);
594 if (dump_file && (dump_flags & TDF_DETAILS))
596 fprintf (dump_file, " with ");
597 print_generic_stmt (dump_file, stmt, TDF_SLIM);
598 fprintf (dump_file, "\n");
603 /* And transfer what we learned from VALUE_VECTOR into the
604 SSA_NAMEs themselves. This probably isn't terribly important
605 since we probably constant propagated the values to their
607 for (i = 0; i < num_ssa_names; i++)
609 tree name = ssa_name (i);
615 value = get_value (name);
616 if (value->lattice_val == CONSTANT
617 && is_gimple_reg (name)
618 && is_gimple_min_invariant (value->const_val))
619 SSA_NAME_VALUE (name) = value->const_val;
624 /* Free allocated storage. */
629 /* Perform substitutions based on the known constant values. */
630 substitute_and_fold ();
637 /* Compute the meet operator between VAL1 and VAL2:
639 any M UNDEFINED = any
640 any M VARYING = VARYING
641 any M UNKNOWN_VAL = UNKNOWN_VAL
642 Ci M Cj = Ci if (i == j)
643 Ci M Cj = VARYING if (i != j) */
645 ccp_lattice_meet (value val1, value val2)
649 /* any M UNDEFINED = any. */
650 if (val1.lattice_val == UNDEFINED)
652 else if (val2.lattice_val == UNDEFINED)
655 /* any M VARYING = VARYING. */
656 if (val1.lattice_val == VARYING || val2.lattice_val == VARYING)
658 result.lattice_val = VARYING;
659 result.const_val = NULL_TREE;
663 /* any M UNKNOWN_VAL = UNKNOWN_VAL. */
664 if (val1.lattice_val == UNKNOWN_VAL
665 || val2.lattice_val == UNKNOWN_VAL)
667 result.lattice_val = UNKNOWN_VAL;
668 result.const_val = NULL_TREE;
672 /* Ci M Cj = Ci if (i == j)
673 Ci M Cj = VARYING if (i != j) */
674 if (simple_cst_equal (val1.const_val, val2.const_val) == 1)
676 result.lattice_val = CONSTANT;
677 result.const_val = val1.const_val;
681 result.lattice_val = VARYING;
682 result.const_val = NULL_TREE;
689 /* Loop through the PHI_NODE's parameters for BLOCK and compare their
690 lattice values to determine PHI_NODE's lattice value. The value of a
691 PHI node is determined calling ccp_lattice_meet() with all the arguments
692 of the PHI node that are incoming via executable edges. */
694 static enum ssa_prop_result
695 ccp_visit_phi_node (tree phi)
697 value new_val, *old_val;
700 if (dump_file && (dump_flags & TDF_DETAILS))
702 fprintf (dump_file, "\nVisiting PHI node: ");
703 print_generic_expr (dump_file, phi, dump_flags);
706 old_val = get_value (PHI_RESULT (phi));
707 switch (old_val->lattice_val)
710 return SSA_PROP_NOT_INTERESTING;
717 /* To avoid the default value of UNKNOWN_VAL overriding
718 that of its possible constant arguments, temporarily
719 set the PHI node's default lattice value to be
720 UNDEFINED. If the PHI node's old value was UNKNOWN_VAL and
721 the new value is UNDEFINED, then we prevent the invalid
722 transition by not calling set_lattice_value. */
723 new_val.lattice_val = UNDEFINED;
724 new_val.const_val = NULL_TREE;
729 new_val.lattice_val = UNDEFINED;
730 new_val.const_val = NULL_TREE;
737 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
739 /* Compute the meet operator over all the PHI arguments. */
740 edge e = PHI_ARG_EDGE (phi, i);
742 if (dump_file && (dump_flags & TDF_DETAILS))
745 "\n Argument #%d (%d -> %d %sexecutable)\n",
746 i, e->src->index, e->dest->index,
747 (e->flags & EDGE_EXECUTABLE) ? "" : "not ");
750 /* If the incoming edge is executable, Compute the meet operator for
751 the existing value of the PHI node and the current PHI argument. */
752 if (e->flags & EDGE_EXECUTABLE)
754 tree rdef = PHI_ARG_DEF (phi, i);
755 value *rdef_val, val;
757 if (is_gimple_min_invariant (rdef))
759 val.lattice_val = CONSTANT;
760 val.const_val = rdef;
764 rdef_val = get_value (rdef);
766 new_val = ccp_lattice_meet (new_val, *rdef_val);
768 if (dump_file && (dump_flags & TDF_DETAILS))
770 fprintf (dump_file, "\t");
771 print_generic_expr (dump_file, rdef, dump_flags);
772 dump_lattice_value (dump_file, "\tValue: ", *rdef_val);
773 fprintf (dump_file, "\n");
776 if (new_val.lattice_val == VARYING)
781 if (dump_file && (dump_flags & TDF_DETAILS))
783 dump_lattice_value (dump_file, "\n PHI node value: ", new_val);
784 fprintf (dump_file, "\n\n");
787 /* Check for an invalid change from UNKNOWN_VAL to UNDEFINED. */
788 if (old_val->lattice_val == UNKNOWN_VAL
789 && new_val.lattice_val == UNDEFINED)
790 return SSA_PROP_NOT_INTERESTING;
792 /* Otherwise, make the transition to the new value. */
793 if (set_lattice_value (PHI_RESULT (phi), new_val))
795 if (new_val.lattice_val == VARYING)
796 return SSA_PROP_VARYING;
798 return SSA_PROP_INTERESTING;
801 return SSA_PROP_NOT_INTERESTING;
805 /* CCP specific front-end to the non-destructive constant folding
808 Attempt to simplify the RHS of STMT knowing that one or more
809 operands are constants.
811 If simplification is possible, return the simplified RHS,
812 otherwise return the original RHS. */
817 tree rhs = get_rhs (stmt);
818 enum tree_code code = TREE_CODE (rhs);
819 enum tree_code_class kind = TREE_CODE_CLASS (code);
820 tree retval = NULL_TREE;
823 vuses = STMT_VUSE_OPS (stmt);
825 /* If the RHS is just a variable, then that variable must now have
826 a constant value that we can return directly. */
827 if (TREE_CODE (rhs) == SSA_NAME)
828 return get_value (rhs)->const_val;
829 else if (DECL_P (rhs)
830 && NUM_VUSES (vuses) == 1
831 && rhs == SSA_NAME_VAR (VUSE_OP (vuses, 0)))
832 return get_value (VUSE_OP (vuses, 0))->const_val;
834 /* Unary operators. Note that we know the single operand must
835 be a constant. So this should almost always return a
837 if (kind == tcc_unary)
839 /* Handle unary operators which can appear in GIMPLE form. */
840 tree op0 = TREE_OPERAND (rhs, 0);
842 /* Simplify the operand down to a constant. */
843 if (TREE_CODE (op0) == SSA_NAME)
845 value *val = get_value (op0);
846 if (val->lattice_val == CONSTANT)
847 op0 = get_value (op0)->const_val;
850 retval = nondestructive_fold_unary_to_constant (code,
854 /* If we folded, but did not create an invariant, then we can not
855 use this expression. */
856 if (retval && ! is_gimple_min_invariant (retval))
859 /* If we could not fold the expression, but the arguments are all
860 constants and gimple values, then build and return the new
863 In some cases the new expression is still something we can
864 use as a replacement for an argument. This happens with
865 NOP conversions of types for example.
867 In other cases the new expression can not be used as a
868 replacement for an argument (as it would create non-gimple
869 code). But the new expression can still be used to derive
871 if (! retval && is_gimple_min_invariant (op0))
872 return build1 (code, TREE_TYPE (rhs), op0);
875 /* Binary and comparison operators. We know one or both of the
876 operands are constants. */
877 else if (kind == tcc_binary
878 || kind == tcc_comparison
879 || code == TRUTH_AND_EXPR
880 || code == TRUTH_OR_EXPR
881 || code == TRUTH_XOR_EXPR)
883 /* Handle binary and comparison operators that can appear in
885 tree op0 = TREE_OPERAND (rhs, 0);
886 tree op1 = TREE_OPERAND (rhs, 1);
888 /* Simplify the operands down to constants when appropriate. */
889 if (TREE_CODE (op0) == SSA_NAME)
891 value *val = get_value (op0);
892 if (val->lattice_val == CONSTANT)
893 op0 = val->const_val;
896 if (TREE_CODE (op1) == SSA_NAME)
898 value *val = get_value (op1);
899 if (val->lattice_val == CONSTANT)
900 op1 = val->const_val;
903 retval = nondestructive_fold_binary_to_constant (code,
907 /* If we folded, but did not create an invariant, then we can not
908 use this expression. */
909 if (retval && ! is_gimple_min_invariant (retval))
912 /* If we could not fold the expression, but the arguments are all
913 constants and gimple values, then build and return the new
916 In some cases the new expression is still something we can
917 use as a replacement for an argument. This happens with
918 NOP conversions of types for example.
920 In other cases the new expression can not be used as a
921 replacement for an argument (as it would create non-gimple
922 code). But the new expression can still be used to derive
925 && is_gimple_min_invariant (op0)
926 && is_gimple_min_invariant (op1))
927 return build (code, TREE_TYPE (rhs), op0, op1);
930 /* We may be able to fold away calls to builtin functions if their
931 arguments are constants. */
932 else if (code == CALL_EXPR
933 && TREE_CODE (TREE_OPERAND (rhs, 0)) == ADDR_EXPR
934 && (TREE_CODE (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0))
936 && DECL_BUILT_IN (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0)))
938 use_optype uses = STMT_USE_OPS (stmt);
939 if (NUM_USES (uses) != 0)
944 /* Preserve the original values of every operand. */
945 orig = xmalloc (sizeof (tree) * NUM_USES (uses));
946 for (i = 0; i < NUM_USES (uses); i++)
947 orig[i] = USE_OP (uses, i);
949 /* Substitute operands with their values and try to fold. */
950 replace_uses_in (stmt, NULL);
951 retval = fold_builtin (rhs, false);
953 /* Restore operands to their original form. */
954 for (i = 0; i < NUM_USES (uses); i++)
955 SET_USE_OP (uses, i, orig[i]);
962 /* If we got a simplified form, see if we need to convert its type. */
964 return fold_convert (TREE_TYPE (rhs), retval);
966 /* No simplification was possible. */
971 /* Evaluate statement STMT. */
974 evaluate_stmt (tree stmt)
978 latticevalue likelyvalue = likely_value (stmt);
980 /* If the statement is likely to have a CONSTANT result, then try
981 to fold the statement to determine the constant value. */
982 if (likelyvalue == CONSTANT)
983 simplified = ccp_fold (stmt);
984 /* If the statement is likely to have a VARYING result, then do not
985 bother folding the statement. */
986 else if (likelyvalue == VARYING)
987 simplified = get_rhs (stmt);
988 /* Otherwise the statement is likely to have an UNDEFINED value and
989 there will be nothing to do. */
991 simplified = NULL_TREE;
993 if (simplified && is_gimple_min_invariant (simplified))
995 /* The statement produced a constant value. */
996 val.lattice_val = CONSTANT;
997 val.const_val = simplified;
1001 /* The statement produced a nonconstant value. If the statement
1002 had undefined or virtual operands, then the result of the
1003 statement should be undefined or virtual respectively.
1004 Else the result of the statement is VARYING. */
1005 val.lattice_val = (likelyvalue == UNDEFINED ? UNDEFINED : VARYING);
1006 val.lattice_val = (likelyvalue == UNKNOWN_VAL
1007 ? UNKNOWN_VAL : val.lattice_val);
1008 val.const_val = NULL_TREE;
1015 /* Visit the assignment statement STMT. Set the value of its LHS to the
1016 value computed by the RHS and store LHS in *OUTPUT_P. */
1018 static enum ssa_prop_result
1019 visit_assignment (tree stmt, tree *output_p)
1024 v_must_def_optype v_must_defs;
1026 lhs = TREE_OPERAND (stmt, 0);
1027 rhs = TREE_OPERAND (stmt, 1);
1028 vuses = STMT_VUSE_OPS (stmt);
1029 v_must_defs = STMT_V_MUST_DEF_OPS (stmt);
1031 gcc_assert (NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) == 0);
1032 gcc_assert (NUM_V_MUST_DEFS (v_must_defs) == 1
1033 || TREE_CODE (lhs) == SSA_NAME);
1035 /* We require the SSA version number of the lhs for the value_vector.
1036 Make sure we have it. */
1037 if (TREE_CODE (lhs) != SSA_NAME)
1039 /* If we make it here, then stmt only has one definition:
1041 lhs = V_MUST_DEF_RESULT (v_must_defs, 0);
1044 if (TREE_CODE (rhs) == SSA_NAME)
1046 /* For a simple copy operation, we copy the lattice values. */
1047 value *nval = get_value (rhs);
1050 else if (DECL_P (rhs)
1051 && NUM_VUSES (vuses) == 1
1052 && rhs == SSA_NAME_VAR (VUSE_OP (vuses, 0)))
1054 /* Same as above, but the rhs is not a gimple register and yet
1055 has a known VUSE. */
1056 value *nval = get_value (VUSE_OP (vuses, 0));
1061 /* Evaluate the statement. */
1062 val = evaluate_stmt (stmt);
1065 /* FIXME: Hack. If this was a definition of a bitfield, we need to widen
1066 the constant value into the type of the destination variable. This
1067 should not be necessary if GCC represented bitfields properly. */
1069 tree lhs = TREE_OPERAND (stmt, 0);
1070 if (val.lattice_val == CONSTANT
1071 && TREE_CODE (lhs) == COMPONENT_REF
1072 && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))
1074 tree w = widen_bitfield (val.const_val, TREE_OPERAND (lhs, 1), lhs);
1076 if (w && is_gimple_min_invariant (w))
1080 val.lattice_val = VARYING;
1081 val.const_val = NULL;
1086 /* If LHS is not a gimple register, then it cannot take on an
1088 if (!is_gimple_reg (SSA_NAME_VAR (lhs))
1089 && val.lattice_val == UNDEFINED)
1090 val.lattice_val = UNKNOWN_VAL;
1092 /* Set the lattice value of the statement's output. */
1093 if (set_lattice_value (lhs, val))
1096 if (val.lattice_val == VARYING)
1097 return SSA_PROP_VARYING;
1099 return SSA_PROP_INTERESTING;
1102 return SSA_PROP_NOT_INTERESTING;
1106 /* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING
1107 if it can determine which edge will be taken. Otherwise, return
1108 SSA_PROP_VARYING. */
1110 static enum ssa_prop_result
1111 visit_cond_stmt (tree stmt, edge *taken_edge_p)
1116 block = bb_for_stmt (stmt);
1117 val = evaluate_stmt (stmt);
1119 /* Find which edge out of the conditional block will be taken and add it
1120 to the worklist. If no single edge can be determined statically,
1121 return SSA_PROP_VARYING to feed all the outgoing edges to the
1122 propagation engine. */
1123 *taken_edge_p = val.const_val ? find_taken_edge (block, val.const_val) : 0;
1125 return SSA_PROP_INTERESTING;
1127 return SSA_PROP_VARYING;
1131 /* Evaluate statement STMT. If the statement produces an output value and
1132 its evaluation changes the lattice value of its output, return
1133 SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the
1136 If STMT is a conditional branch and we can determine its truth
1137 value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying
1138 value, return SSA_PROP_VARYING. */
1140 static enum ssa_prop_result
1141 ccp_visit_stmt (tree stmt, edge *taken_edge_p, tree *output_p)
1144 v_may_def_optype v_may_defs;
1145 v_must_def_optype v_must_defs;
1149 if (dump_file && (dump_flags & TDF_DETAILS))
1151 fprintf (dump_file, "\nVisiting statement: ");
1152 print_generic_stmt (dump_file, stmt, TDF_SLIM);
1153 fprintf (dump_file, "\n");
1156 ann = stmt_ann (stmt);
1158 v_must_defs = V_MUST_DEF_OPS (ann);
1159 v_may_defs = V_MAY_DEF_OPS (ann);
1160 if (TREE_CODE (stmt) == MODIFY_EXPR
1161 && NUM_V_MAY_DEFS (v_may_defs) == 0
1162 && (NUM_V_MUST_DEFS (v_must_defs) == 1
1163 || TREE_CODE (TREE_OPERAND (stmt, 0)) == SSA_NAME))
1165 /* If the statement is an assignment that produces a single
1166 output value, evaluate its RHS to see if the lattice value of
1167 its output has changed. */
1168 return visit_assignment (stmt, output_p);
1170 else if (TREE_CODE (stmt) == COND_EXPR || TREE_CODE (stmt) == SWITCH_EXPR)
1172 /* If STMT is a conditional branch, see if we can determine
1173 which branch will be taken. */
1174 return visit_cond_stmt (stmt, taken_edge_p);
1177 /* Any other kind of statement is not interesting for constant
1178 propagation and, therefore, not worth simulating. */
1179 if (dump_file && (dump_flags & TDF_DETAILS))
1180 fprintf (dump_file, "No interesting values produced. Marked VARYING.\n");
1182 /* Definitions made by statements other than assignments to
1183 SSA_NAMEs represent unknown modifications to their outputs.
1184 Mark them VARYING. */
1185 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
1186 def_to_varying (def);
1188 /* Mark all V_MAY_DEF operands VARYING. */
1189 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_VMAYDEF)
1190 def_to_varying (def);
1192 return SSA_PROP_VARYING;
1196 /* Main entry point for SSA Conditional Constant Propagation.
1198 [ DESCRIBE MAIN ALGORITHM HERE ] */
1201 execute_ssa_ccp (void)
1204 ssa_propagate (ccp_visit_stmt, ccp_visit_phi_node);
1212 return flag_tree_ccp != 0;
1216 struct tree_opt_pass pass_ccp =
1219 gate_ccp, /* gate */
1220 execute_ssa_ccp, /* execute */
1223 0, /* static_pass_number */
1224 TV_TREE_CCP, /* tv_id */
1225 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
1226 0, /* properties_provided */
1227 0, /* properties_destroyed */
1228 0, /* todo_flags_start */
1229 TODO_cleanup_cfg | TODO_dump_func | TODO_rename_vars
1230 | TODO_ggc_collect | TODO_verify_ssa
1231 | TODO_verify_stmts, /* todo_flags_finish */
1236 /* Given a constant value VAL for bitfield FIELD, and a destination
1237 variable VAR, return VAL appropriately widened to fit into VAR. If
1238 FIELD is wider than HOST_WIDE_INT, NULL is returned. */
1241 widen_bitfield (tree val, tree field, tree var)
1243 unsigned HOST_WIDE_INT var_size, field_size;
1245 unsigned HOST_WIDE_INT mask;
1248 /* We can only do this if the size of the type and field and VAL are
1249 all constants representable in HOST_WIDE_INT. */
1250 if (!host_integerp (TYPE_SIZE (TREE_TYPE (var)), 1)
1251 || !host_integerp (DECL_SIZE (field), 1)
1252 || !host_integerp (val, 0))
1255 var_size = tree_low_cst (TYPE_SIZE (TREE_TYPE (var)), 1);
1256 field_size = tree_low_cst (DECL_SIZE (field), 1);
1258 /* Give up if either the bitfield or the variable are too wide. */
1259 if (field_size > HOST_BITS_PER_WIDE_INT || var_size > HOST_BITS_PER_WIDE_INT)
1262 gcc_assert (var_size >= field_size);
1264 /* If the sign bit of the value is not set or the field's type is unsigned,
1265 just mask off the high order bits of the value. */
1266 if (DECL_UNSIGNED (field)
1267 || !(tree_low_cst (val, 0) & (((HOST_WIDE_INT)1) << (field_size - 1))))
1269 /* Zero extension. Build a mask with the lower 'field_size' bits
1270 set and a BIT_AND_EXPR node to clear the high order bits of
1272 for (i = 0, mask = 0; i < field_size; i++)
1273 mask |= ((HOST_WIDE_INT) 1) << i;
1275 wide_val = build (BIT_AND_EXPR, TREE_TYPE (var), val,
1276 fold_convert (TREE_TYPE (var),
1277 build_int_cst (NULL_TREE, mask)));
1281 /* Sign extension. Create a mask with the upper 'field_size'
1282 bits set and a BIT_IOR_EXPR to set the high order bits of the
1284 for (i = 0, mask = 0; i < (var_size - field_size); i++)
1285 mask |= ((HOST_WIDE_INT) 1) << (var_size - i - 1);
1287 wide_val = build (BIT_IOR_EXPR, TREE_TYPE (var), val,
1288 fold_convert (TREE_TYPE (var),
1289 build_int_cst (NULL_TREE, mask)));
1292 return fold (wide_val);
1296 /* A subroutine of fold_stmt_r. Attempts to fold *(A+O) to A[X].
1297 BASE is an array type. OFFSET is a byte displacement. ORIG_TYPE
1298 is the desired result type. */
1301 maybe_fold_offset_to_array_ref (tree base, tree offset, tree orig_type)
1303 tree min_idx, idx, elt_offset = integer_zero_node;
1304 tree array_type, elt_type, elt_size;
1306 /* If BASE is an ARRAY_REF, we can pick up another offset (this time
1307 measured in units of the size of elements type) from that ARRAY_REF).
1308 We can't do anything if either is variable.
1310 The case we handle here is *(&A[N]+O). */
1311 if (TREE_CODE (base) == ARRAY_REF)
1313 tree low_bound = array_ref_low_bound (base);
1315 elt_offset = TREE_OPERAND (base, 1);
1316 if (TREE_CODE (low_bound) != INTEGER_CST
1317 || TREE_CODE (elt_offset) != INTEGER_CST)
1320 elt_offset = int_const_binop (MINUS_EXPR, elt_offset, low_bound, 0);
1321 base = TREE_OPERAND (base, 0);
1324 /* Ignore stupid user tricks of indexing non-array variables. */
1325 array_type = TREE_TYPE (base);
1326 if (TREE_CODE (array_type) != ARRAY_TYPE)
1328 elt_type = TREE_TYPE (array_type);
1329 if (!lang_hooks.types_compatible_p (orig_type, elt_type))
1332 /* If OFFSET and ELT_OFFSET are zero, we don't care about the size of the
1333 element type (so we can use the alignment if it's not constant).
1334 Otherwise, compute the offset as an index by using a division. If the
1335 division isn't exact, then don't do anything. */
1336 elt_size = TYPE_SIZE_UNIT (elt_type);
1337 if (integer_zerop (offset))
1339 if (TREE_CODE (elt_size) != INTEGER_CST)
1340 elt_size = size_int (TYPE_ALIGN (elt_type));
1342 idx = integer_zero_node;
1346 unsigned HOST_WIDE_INT lquo, lrem;
1347 HOST_WIDE_INT hquo, hrem;
1349 if (TREE_CODE (elt_size) != INTEGER_CST
1350 || div_and_round_double (TRUNC_DIV_EXPR, 1,
1351 TREE_INT_CST_LOW (offset),
1352 TREE_INT_CST_HIGH (offset),
1353 TREE_INT_CST_LOW (elt_size),
1354 TREE_INT_CST_HIGH (elt_size),
1355 &lquo, &hquo, &lrem, &hrem)
1359 idx = build_int_cst_wide (NULL_TREE, lquo, hquo);
1362 /* Assume the low bound is zero. If there is a domain type, get the
1363 low bound, if any, convert the index into that type, and add the
1365 min_idx = integer_zero_node;
1366 if (TYPE_DOMAIN (array_type))
1368 if (TYPE_MIN_VALUE (TYPE_DOMAIN (array_type)))
1369 min_idx = TYPE_MIN_VALUE (TYPE_DOMAIN (array_type));
1371 min_idx = fold_convert (TYPE_DOMAIN (array_type), min_idx);
1373 if (TREE_CODE (min_idx) != INTEGER_CST)
1376 idx = fold_convert (TYPE_DOMAIN (array_type), idx);
1377 elt_offset = fold_convert (TYPE_DOMAIN (array_type), elt_offset);
1380 if (!integer_zerop (min_idx))
1381 idx = int_const_binop (PLUS_EXPR, idx, min_idx, 0);
1382 if (!integer_zerop (elt_offset))
1383 idx = int_const_binop (PLUS_EXPR, idx, elt_offset, 0);
1385 return build (ARRAY_REF, orig_type, base, idx, min_idx,
1386 size_int (tree_low_cst (elt_size, 1)
1387 / (TYPE_ALIGN_UNIT (elt_type))));
1391 /* A subroutine of fold_stmt_r. Attempts to fold *(S+O) to S.X.
1392 BASE is a record type. OFFSET is a byte displacement. ORIG_TYPE
1393 is the desired result type. */
1394 /* ??? This doesn't handle class inheritance. */
1397 maybe_fold_offset_to_component_ref (tree record_type, tree base, tree offset,
1398 tree orig_type, bool base_is_ptr)
1400 tree f, t, field_type, tail_array_field, field_offset;
1402 if (TREE_CODE (record_type) != RECORD_TYPE
1403 && TREE_CODE (record_type) != UNION_TYPE
1404 && TREE_CODE (record_type) != QUAL_UNION_TYPE)
1407 /* Short-circuit silly cases. */
1408 if (lang_hooks.types_compatible_p (record_type, orig_type))
1411 tail_array_field = NULL_TREE;
1412 for (f = TYPE_FIELDS (record_type); f ; f = TREE_CHAIN (f))
1416 if (TREE_CODE (f) != FIELD_DECL)
1418 if (DECL_BIT_FIELD (f))
1421 field_offset = byte_position (f);
1422 if (TREE_CODE (field_offset) != INTEGER_CST)
1425 /* ??? Java creates "interesting" fields for representing base classes.
1426 They have no name, and have no context. With no context, we get into
1427 trouble with nonoverlapping_component_refs_p. Skip them. */
1428 if (!DECL_FIELD_CONTEXT (f))
1431 /* The previous array field isn't at the end. */
1432 tail_array_field = NULL_TREE;
1434 /* Check to see if this offset overlaps with the field. */
1435 cmp = tree_int_cst_compare (field_offset, offset);
1439 field_type = TREE_TYPE (f);
1442 /* Don't care about offsets into the middle of scalars. */
1443 if (!AGGREGATE_TYPE_P (field_type))
1446 /* Check for array at the end of the struct. This is often
1447 used as for flexible array members. We should be able to
1448 turn this into an array access anyway. */
1449 if (TREE_CODE (field_type) == ARRAY_TYPE)
1450 tail_array_field = f;
1452 /* Check the end of the field against the offset. */
1453 if (!DECL_SIZE_UNIT (f)
1454 || TREE_CODE (DECL_SIZE_UNIT (f)) != INTEGER_CST)
1456 t = int_const_binop (MINUS_EXPR, offset, DECL_FIELD_OFFSET (f), 1);
1457 if (!tree_int_cst_lt (t, DECL_SIZE_UNIT (f)))
1460 /* If we matched, then set offset to the displacement into
1465 /* Here we exactly match the offset being checked. If the types match,
1466 then we can return that field. */
1467 else if (lang_hooks.types_compatible_p (orig_type, field_type))
1470 base = build1 (INDIRECT_REF, record_type, base);
1471 t = build (COMPONENT_REF, field_type, base, f, NULL_TREE);
1475 /* Don't care about type-punning of scalars. */
1476 else if (!AGGREGATE_TYPE_P (field_type))
1482 if (!tail_array_field)
1485 f = tail_array_field;
1486 field_type = TREE_TYPE (f);
1489 /* If we get here, we've got an aggregate field, and a possibly
1490 nonzero offset into them. Recurse and hope for a valid match. */
1492 base = build1 (INDIRECT_REF, record_type, base);
1493 base = build (COMPONENT_REF, field_type, base, f, NULL_TREE);
1495 t = maybe_fold_offset_to_array_ref (base, offset, orig_type);
1498 return maybe_fold_offset_to_component_ref (field_type, base, offset,
1503 /* A subroutine of fold_stmt_r. Attempt to simplify *(BASE+OFFSET).
1504 Return the simplified expression, or NULL if nothing could be done. */
1507 maybe_fold_stmt_indirect (tree expr, tree base, tree offset)
1511 /* We may well have constructed a double-nested PLUS_EXPR via multiple
1512 substitutions. Fold that down to one. Remove NON_LVALUE_EXPRs that
1513 are sometimes added. */
1516 TREE_OPERAND (expr, 0) = base;
1518 /* One possibility is that the address reduces to a string constant. */
1519 t = fold_read_from_constant_string (expr);
1523 /* Add in any offset from a PLUS_EXPR. */
1524 if (TREE_CODE (base) == PLUS_EXPR)
1528 offset2 = TREE_OPERAND (base, 1);
1529 if (TREE_CODE (offset2) != INTEGER_CST)
1531 base = TREE_OPERAND (base, 0);
1533 offset = int_const_binop (PLUS_EXPR, offset, offset2, 1);
1536 if (TREE_CODE (base) == ADDR_EXPR)
1538 /* Strip the ADDR_EXPR. */
1539 base = TREE_OPERAND (base, 0);
1541 /* Fold away CONST_DECL to its value, if the type is scalar. */
1542 if (TREE_CODE (base) == CONST_DECL
1543 && is_gimple_min_invariant (DECL_INITIAL (base)))
1544 return DECL_INITIAL (base);
1546 /* Try folding *(&B+O) to B[X]. */
1547 t = maybe_fold_offset_to_array_ref (base, offset, TREE_TYPE (expr));
1551 /* Try folding *(&B+O) to B.X. */
1552 t = maybe_fold_offset_to_component_ref (TREE_TYPE (base), base, offset,
1553 TREE_TYPE (expr), false);
1557 /* Fold *&B to B. We can only do this if EXPR is the same type
1558 as BASE. We can't do this if EXPR is the element type of an array
1559 and BASE is the array. */
1560 if (integer_zerop (offset)
1561 && lang_hooks.types_compatible_p (TREE_TYPE (base),
1567 /* We can get here for out-of-range string constant accesses,
1568 such as "_"[3]. Bail out of the entire substitution search
1569 and arrange for the entire statement to be replaced by a
1570 call to __builtin_trap. In all likelyhood this will all be
1571 constant-folded away, but in the meantime we can't leave with
1572 something that get_expr_operands can't understand. */
1576 if (TREE_CODE (t) == ADDR_EXPR
1577 && TREE_CODE (TREE_OPERAND (t, 0)) == STRING_CST)
1579 /* FIXME: Except that this causes problems elsewhere with dead
1580 code not being deleted, and we abort in the rtl expanders
1581 because we failed to remove some ssa_name. In the meantime,
1582 just return zero. */
1583 /* FIXME2: This condition should be signaled by
1584 fold_read_from_constant_string directly, rather than
1585 re-checking for it here. */
1586 return integer_zero_node;
1589 /* Try folding *(B+O) to B->X. Still an improvement. */
1590 if (POINTER_TYPE_P (TREE_TYPE (base)))
1592 t = maybe_fold_offset_to_component_ref (TREE_TYPE (TREE_TYPE (base)),
1594 TREE_TYPE (expr), true);
1600 /* Otherwise we had an offset that we could not simplify. */
1605 /* A subroutine of fold_stmt_r. EXPR is a PLUS_EXPR.
1607 A quaint feature extant in our address arithmetic is that there
1608 can be hidden type changes here. The type of the result need
1609 not be the same as the type of the input pointer.
1611 What we're after here is an expression of the form
1612 (T *)(&array + const)
1613 where the cast doesn't actually exist, but is implicit in the
1614 type of the PLUS_EXPR. We'd like to turn this into
1616 which may be able to propagate further. */
1619 maybe_fold_stmt_addition (tree expr)
1621 tree op0 = TREE_OPERAND (expr, 0);
1622 tree op1 = TREE_OPERAND (expr, 1);
1623 tree ptr_type = TREE_TYPE (expr);
1626 bool subtract = (TREE_CODE (expr) == MINUS_EXPR);
1628 /* We're only interested in pointer arithmetic. */
1629 if (!POINTER_TYPE_P (ptr_type))
1631 /* Canonicalize the integral operand to op1. */
1632 if (INTEGRAL_TYPE_P (TREE_TYPE (op0)))
1636 t = op0, op0 = op1, op1 = t;
1638 /* It had better be a constant. */
1639 if (TREE_CODE (op1) != INTEGER_CST)
1641 /* The first operand should be an ADDR_EXPR. */
1642 if (TREE_CODE (op0) != ADDR_EXPR)
1644 op0 = TREE_OPERAND (op0, 0);
1646 /* If the first operand is an ARRAY_REF, expand it so that we can fold
1647 the offset into it. */
1648 while (TREE_CODE (op0) == ARRAY_REF)
1650 tree array_obj = TREE_OPERAND (op0, 0);
1651 tree array_idx = TREE_OPERAND (op0, 1);
1652 tree elt_type = TREE_TYPE (op0);
1653 tree elt_size = TYPE_SIZE_UNIT (elt_type);
1656 if (TREE_CODE (array_idx) != INTEGER_CST)
1658 if (TREE_CODE (elt_size) != INTEGER_CST)
1661 /* Un-bias the index by the min index of the array type. */
1662 min_idx = TYPE_DOMAIN (TREE_TYPE (array_obj));
1665 min_idx = TYPE_MIN_VALUE (min_idx);
1668 if (TREE_CODE (min_idx) != INTEGER_CST)
1671 array_idx = convert (TREE_TYPE (min_idx), array_idx);
1672 if (!integer_zerop (min_idx))
1673 array_idx = int_const_binop (MINUS_EXPR, array_idx,
1678 /* Convert the index to a byte offset. */
1679 array_idx = convert (sizetype, array_idx);
1680 array_idx = int_const_binop (MULT_EXPR, array_idx, elt_size, 0);
1682 /* Update the operands for the next round, or for folding. */
1683 /* If we're manipulating unsigned types, then folding into negative
1684 values can produce incorrect results. Particularly if the type
1685 is smaller than the width of the pointer. */
1687 && TYPE_UNSIGNED (TREE_TYPE (op1))
1688 && tree_int_cst_lt (array_idx, op1))
1690 op1 = int_const_binop (subtract ? MINUS_EXPR : PLUS_EXPR,
1696 /* If we weren't able to fold the subtraction into another array reference,
1697 canonicalize the integer for passing to the array and component ref
1698 simplification functions. */
1701 if (TYPE_UNSIGNED (TREE_TYPE (op1)))
1703 op1 = fold (build1 (NEGATE_EXPR, TREE_TYPE (op1), op1));
1704 /* ??? In theory fold should always produce another integer. */
1705 if (TREE_CODE (op1) != INTEGER_CST)
1709 ptd_type = TREE_TYPE (ptr_type);
1711 /* At which point we can try some of the same things as for indirects. */
1712 t = maybe_fold_offset_to_array_ref (op0, op1, ptd_type);
1714 t = maybe_fold_offset_to_component_ref (TREE_TYPE (op0), op0, op1,
1717 t = build1 (ADDR_EXPR, ptr_type, t);
1723 /* Subroutine of fold_stmt called via walk_tree. We perform several
1724 simplifications of EXPR_P, mostly having to do with pointer arithmetic. */
1727 fold_stmt_r (tree *expr_p, int *walk_subtrees, void *data)
1729 bool *changed_p = data;
1730 tree expr = *expr_p, t;
1732 /* ??? It'd be nice if walk_tree had a pre-order option. */
1733 switch (TREE_CODE (expr))
1736 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1741 t = maybe_fold_stmt_indirect (expr, TREE_OPERAND (expr, 0),
1745 /* ??? Could handle ARRAY_REF here, as a variant of INDIRECT_REF.
1746 We'd only want to bother decomposing an existing ARRAY_REF if
1747 the base array is found to have another offset contained within.
1748 Otherwise we'd be wasting time. */
1751 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1756 /* Set TREE_INVARIANT properly so that the value is properly
1757 considered constant, and so gets propagated as expected. */
1759 recompute_tree_invarant_for_addr_expr (expr);
1764 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1767 t = walk_tree (&TREE_OPERAND (expr, 1), fold_stmt_r, data, NULL);
1772 t = maybe_fold_stmt_addition (expr);
1776 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1781 /* Make sure the FIELD_DECL is actually a field in the type on the lhs.
1782 We've already checked that the records are compatible, so we should
1783 come up with a set of compatible fields. */
1785 tree expr_record = TREE_TYPE (TREE_OPERAND (expr, 0));
1786 tree expr_field = TREE_OPERAND (expr, 1);
1788 if (DECL_FIELD_CONTEXT (expr_field) != TYPE_MAIN_VARIANT (expr_record))
1790 expr_field = find_compatible_field (expr_record, expr_field);
1791 TREE_OPERAND (expr, 1) = expr_field;
1810 /* Return the string length of ARG in LENGTH. If ARG is an SSA name variable,
1811 follow its use-def chains. If LENGTH is not NULL and its value is not
1812 equal to the length we determine, or if we are unable to determine the
1813 length, return false. VISITED is a bitmap of visited variables. */
1816 get_strlen (tree arg, tree *length, bitmap visited)
1818 tree var, def_stmt, val;
1820 if (TREE_CODE (arg) != SSA_NAME)
1822 val = c_strlen (arg, 1);
1826 if (*length && simple_cst_equal (val, *length) != 1)
1833 /* If we were already here, break the infinite cycle. */
1834 if (bitmap_bit_p (visited, SSA_NAME_VERSION (arg)))
1836 bitmap_set_bit (visited, SSA_NAME_VERSION (arg));
1839 def_stmt = SSA_NAME_DEF_STMT (var);
1841 switch (TREE_CODE (def_stmt))
1847 /* The RHS of the statement defining VAR must either have a
1848 constant length or come from another SSA_NAME with a constant
1850 rhs = TREE_OPERAND (def_stmt, 1);
1852 if (TREE_CODE (rhs) == SSA_NAME)
1853 return get_strlen (rhs, length, visited);
1855 /* See if the RHS is a constant length. */
1856 len = c_strlen (rhs, 1);
1859 if (*length && simple_cst_equal (len, *length) != 1)
1871 /* All the arguments of the PHI node must have the same constant
1875 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
1877 tree arg = PHI_ARG_DEF (def_stmt, i);
1879 /* If this PHI has itself as an argument, we cannot
1880 determine the string length of this argument. However,
1881 if we can find a constant string length for the other
1882 PHI args then we can still be sure that this is a
1883 constant string length. So be optimistic and just
1884 continue with the next argument. */
1885 if (arg == PHI_RESULT (def_stmt))
1888 if (!get_strlen (arg, length, visited))
1904 /* Fold builtin call FN in statement STMT. If it cannot be folded into a
1905 constant, return NULL_TREE. Otherwise, return its constant value. */
1908 ccp_fold_builtin (tree stmt, tree fn)
1910 tree result, strlen_val[2];
1911 tree callee, arglist, a;
1916 ignore = TREE_CODE (stmt) != MODIFY_EXPR;
1918 /* First try the generic builtin folder. If that succeeds, return the
1920 result = fold_builtin (fn, ignore);
1924 STRIP_NOPS (result);
1928 /* Ignore MD builtins. */
1929 callee = get_callee_fndecl (fn);
1930 if (DECL_BUILT_IN_CLASS (callee) == BUILT_IN_MD)
1933 /* If the builtin could not be folded, and it has no argument list,
1935 arglist = TREE_OPERAND (fn, 1);
1939 /* Limit the work only for builtins we know how to simplify. */
1940 switch (DECL_FUNCTION_CODE (callee))
1942 case BUILT_IN_STRLEN:
1943 case BUILT_IN_FPUTS:
1944 case BUILT_IN_FPUTS_UNLOCKED:
1947 case BUILT_IN_STRCPY:
1948 case BUILT_IN_STRNCPY:
1955 /* Try to use the dataflow information gathered by the CCP process. */
1956 visited = BITMAP_XMALLOC ();
1958 memset (strlen_val, 0, sizeof (strlen_val));
1959 for (i = 0, a = arglist;
1961 i++, strlen_arg >>= 1, a = TREE_CHAIN (a))
1964 bitmap_clear (visited);
1965 if (!get_strlen (TREE_VALUE (a), &strlen_val[i], visited))
1966 strlen_val[i] = NULL_TREE;
1969 BITMAP_XFREE (visited);
1972 switch (DECL_FUNCTION_CODE (callee))
1974 case BUILT_IN_STRLEN:
1977 tree new = fold_convert (TREE_TYPE (fn), strlen_val[0]);
1979 /* If the result is not a valid gimple value, or not a cast
1980 of a valid gimple value, then we can not use the result. */
1981 if (is_gimple_val (new)
1982 || (is_gimple_cast (new)
1983 && is_gimple_val (TREE_OPERAND (new, 0))))
1988 case BUILT_IN_STRCPY:
1989 if (strlen_val[1] && is_gimple_val (strlen_val[1]))
1990 result = fold_builtin_strcpy (fn, strlen_val[1]);
1993 case BUILT_IN_STRNCPY:
1994 if (strlen_val[1] && is_gimple_val (strlen_val[1]))
1995 result = fold_builtin_strncpy (fn, strlen_val[1]);
1998 case BUILT_IN_FPUTS:
1999 result = fold_builtin_fputs (arglist,
2000 TREE_CODE (stmt) != MODIFY_EXPR, 0,
2004 case BUILT_IN_FPUTS_UNLOCKED:
2005 result = fold_builtin_fputs (arglist,
2006 TREE_CODE (stmt) != MODIFY_EXPR, 1,
2014 if (result && ignore)
2015 result = fold_ignored_result (result);
2020 /* Fold the statement pointed by STMT_P. In some cases, this function may
2021 replace the whole statement with a new one. Returns true iff folding
2022 makes any changes. */
2025 fold_stmt (tree *stmt_p)
2027 tree rhs, result, stmt;
2028 bool changed = false;
2032 /* If we replaced constants and the statement makes pointer dereferences,
2033 then we may need to fold instances of *&VAR into VAR, etc. */
2034 if (walk_tree (stmt_p, fold_stmt_r, &changed, NULL))
2037 = build_function_call_expr (implicit_built_in_decls[BUILT_IN_TRAP],
2042 rhs = get_rhs (stmt);
2047 if (TREE_CODE (rhs) == CALL_EXPR)
2051 /* Check for builtins that CCP can handle using information not
2052 available in the generic fold routines. */
2053 callee = get_callee_fndecl (rhs);
2054 if (callee && DECL_BUILT_IN (callee))
2055 result = ccp_fold_builtin (stmt, rhs);
2058 /* Check for resolvable OBJ_TYPE_REF. The only sorts we can resolve
2059 here are when we've propagated the address of a decl into the
2061 /* ??? Should perhaps do this in fold proper. However, doing it
2062 there requires that we create a new CALL_EXPR, and that requires
2063 copying EH region info to the new node. Easier to just do it
2064 here where we can just smash the call operand. */
2065 callee = TREE_OPERAND (rhs, 0);
2066 if (TREE_CODE (callee) == OBJ_TYPE_REF
2067 && lang_hooks.fold_obj_type_ref
2068 && TREE_CODE (OBJ_TYPE_REF_OBJECT (callee)) == ADDR_EXPR
2069 && DECL_P (TREE_OPERAND
2070 (OBJ_TYPE_REF_OBJECT (callee), 0)))
2074 /* ??? Caution: Broken ADDR_EXPR semantics means that
2075 looking at the type of the operand of the addr_expr
2076 can yield an array type. See silly exception in
2077 check_pointer_types_r. */
2079 t = TREE_TYPE (TREE_TYPE (OBJ_TYPE_REF_OBJECT (callee)));
2080 t = lang_hooks.fold_obj_type_ref (callee, t);
2083 TREE_OPERAND (rhs, 0) = t;
2090 /* If we couldn't fold the RHS, hand over to the generic fold routines. */
2091 if (result == NULL_TREE)
2092 result = fold (rhs);
2094 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
2095 may have been added by fold, and "useless" type conversions that might
2096 now be apparent due to propagation. */
2097 STRIP_USELESS_TYPE_CONVERSION (result);
2100 changed |= set_rhs (stmt_p, result);
2106 /* Convert EXPR into a GIMPLE value suitable for substitution on the
2107 RHS of an assignment. Insert the necessary statements before
2111 convert_to_gimple_builtin (block_stmt_iterator *si_p, tree expr)
2113 tree_stmt_iterator ti;
2114 tree stmt = bsi_stmt (*si_p);
2115 tree tmp, stmts = NULL;
2117 push_gimplify_context ();
2118 tmp = get_initialized_tmp_var (expr, &stmts, NULL);
2119 pop_gimplify_context (NULL);
2121 /* The replacement can expose previously unreferenced variables. */
2122 for (ti = tsi_start (stmts); !tsi_end_p (ti); tsi_next (&ti))
2124 find_new_referenced_vars (tsi_stmt_ptr (ti));
2125 mark_new_vars_to_rename (tsi_stmt (ti), vars_to_rename);
2128 if (EXPR_HAS_LOCATION (stmt))
2129 annotate_all_with_locus (&stmts, EXPR_LOCATION (stmt));
2131 bsi_insert_before (si_p, stmts, BSI_SAME_STMT);
2137 /* A simple pass that attempts to fold all builtin functions. This pass
2138 is run after we've propagated as many constants as we can. */
2141 execute_fold_all_builtins (void)
2143 bool cfg_changed = false;
2147 block_stmt_iterator i;
2148 for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
2150 tree *stmtp = bsi_stmt_ptr (i);
2151 tree call = get_rhs (*stmtp);
2152 tree callee, result;
2154 if (!call || TREE_CODE (call) != CALL_EXPR)
2156 callee = get_callee_fndecl (call);
2157 if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)
2160 result = ccp_fold_builtin (*stmtp, call);
2162 switch (DECL_FUNCTION_CODE (callee))
2164 case BUILT_IN_CONSTANT_P:
2165 /* Resolve __builtin_constant_p. If it hasn't been
2166 folded to integer_one_node by now, it's fairly
2167 certain that the value simply isn't constant. */
2168 result = integer_zero_node;
2175 if (dump_file && (dump_flags & TDF_DETAILS))
2177 fprintf (dump_file, "Simplified\n ");
2178 print_generic_stmt (dump_file, *stmtp, dump_flags);
2181 if (!set_rhs (stmtp, result))
2183 result = convert_to_gimple_builtin (&i, result);
2184 if (result && !set_rhs (stmtp, result))
2187 modify_stmt (*stmtp);
2188 if (maybe_clean_eh_stmt (*stmtp)
2189 && tree_purge_dead_eh_edges (bb))
2192 if (dump_file && (dump_flags & TDF_DETAILS))
2194 fprintf (dump_file, "to\n ");
2195 print_generic_stmt (dump_file, *stmtp, dump_flags);
2196 fprintf (dump_file, "\n");
2201 /* Delete unreachable blocks. */
2203 cleanup_tree_cfg ();
2207 struct tree_opt_pass pass_fold_builtins =
2211 execute_fold_all_builtins, /* execute */
2214 0, /* static_pass_number */
2216 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
2217 0, /* properties_provided */
2218 0, /* properties_destroyed */
2219 0, /* todo_flags_start */
2222 | TODO_rename_vars, /* todo_flags_finish */