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 = fold_unary_to_constant (code, TREE_TYPE (rhs), op0);
852 /* If we folded, but did not create an invariant, then we can not
853 use this expression. */
854 if (retval && ! is_gimple_min_invariant (retval))
857 /* If we could not fold the expression, but the arguments are all
858 constants and gimple values, then build and return the new
861 In some cases the new expression is still something we can
862 use as a replacement for an argument. This happens with
863 NOP conversions of types for example.
865 In other cases the new expression can not be used as a
866 replacement for an argument (as it would create non-gimple
867 code). But the new expression can still be used to derive
869 if (! retval && is_gimple_min_invariant (op0))
870 return build1 (code, TREE_TYPE (rhs), op0);
873 /* Binary and comparison operators. We know one or both of the
874 operands are constants. */
875 else if (kind == tcc_binary
876 || kind == tcc_comparison
877 || code == TRUTH_AND_EXPR
878 || code == TRUTH_OR_EXPR
879 || code == TRUTH_XOR_EXPR)
881 /* Handle binary and comparison operators that can appear in
883 tree op0 = TREE_OPERAND (rhs, 0);
884 tree op1 = TREE_OPERAND (rhs, 1);
886 /* Simplify the operands down to constants when appropriate. */
887 if (TREE_CODE (op0) == SSA_NAME)
889 value *val = get_value (op0);
890 if (val->lattice_val == CONSTANT)
891 op0 = val->const_val;
894 if (TREE_CODE (op1) == SSA_NAME)
896 value *val = get_value (op1);
897 if (val->lattice_val == CONSTANT)
898 op1 = val->const_val;
901 retval = fold_binary_to_constant (code, TREE_TYPE (rhs), op0, op1);
903 /* If we folded, but did not create an invariant, then we can not
904 use this expression. */
905 if (retval && ! is_gimple_min_invariant (retval))
908 /* If we could not fold the expression, but the arguments are all
909 constants and gimple values, then build and return the new
912 In some cases the new expression is still something we can
913 use as a replacement for an argument. This happens with
914 NOP conversions of types for example.
916 In other cases the new expression can not be used as a
917 replacement for an argument (as it would create non-gimple
918 code). But the new expression can still be used to derive
921 && is_gimple_min_invariant (op0)
922 && is_gimple_min_invariant (op1))
923 return build (code, TREE_TYPE (rhs), op0, op1);
926 /* We may be able to fold away calls to builtin functions if their
927 arguments are constants. */
928 else if (code == CALL_EXPR
929 && TREE_CODE (TREE_OPERAND (rhs, 0)) == ADDR_EXPR
930 && (TREE_CODE (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0))
932 && DECL_BUILT_IN (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0)))
934 use_optype uses = STMT_USE_OPS (stmt);
935 if (NUM_USES (uses) != 0)
940 /* Preserve the original values of every operand. */
941 orig = xmalloc (sizeof (tree) * NUM_USES (uses));
942 for (i = 0; i < NUM_USES (uses); i++)
943 orig[i] = USE_OP (uses, i);
945 /* Substitute operands with their values and try to fold. */
946 replace_uses_in (stmt, NULL);
947 retval = fold_builtin (rhs, false);
949 /* Restore operands to their original form. */
950 for (i = 0; i < NUM_USES (uses); i++)
951 SET_USE_OP (uses, i, orig[i]);
958 /* If we got a simplified form, see if we need to convert its type. */
960 return fold_convert (TREE_TYPE (rhs), retval);
962 /* No simplification was possible. */
967 /* Evaluate statement STMT. */
970 evaluate_stmt (tree stmt)
974 latticevalue likelyvalue = likely_value (stmt);
976 /* If the statement is likely to have a CONSTANT result, then try
977 to fold the statement to determine the constant value. */
978 if (likelyvalue == CONSTANT)
979 simplified = ccp_fold (stmt);
980 /* If the statement is likely to have a VARYING result, then do not
981 bother folding the statement. */
982 else if (likelyvalue == VARYING)
983 simplified = get_rhs (stmt);
984 /* Otherwise the statement is likely to have an UNDEFINED value and
985 there will be nothing to do. */
987 simplified = NULL_TREE;
989 if (simplified && is_gimple_min_invariant (simplified))
991 /* The statement produced a constant value. */
992 val.lattice_val = CONSTANT;
993 val.const_val = simplified;
997 /* The statement produced a nonconstant value. If the statement
998 had undefined or virtual operands, then the result of the
999 statement should be undefined or virtual respectively.
1000 Else the result of the statement is VARYING. */
1001 val.lattice_val = (likelyvalue == UNDEFINED ? UNDEFINED : VARYING);
1002 val.lattice_val = (likelyvalue == UNKNOWN_VAL
1003 ? UNKNOWN_VAL : val.lattice_val);
1004 val.const_val = NULL_TREE;
1011 /* Visit the assignment statement STMT. Set the value of its LHS to the
1012 value computed by the RHS and store LHS in *OUTPUT_P. */
1014 static enum ssa_prop_result
1015 visit_assignment (tree stmt, tree *output_p)
1020 v_must_def_optype v_must_defs;
1022 lhs = TREE_OPERAND (stmt, 0);
1023 rhs = TREE_OPERAND (stmt, 1);
1024 vuses = STMT_VUSE_OPS (stmt);
1025 v_must_defs = STMT_V_MUST_DEF_OPS (stmt);
1027 gcc_assert (NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) == 0);
1028 gcc_assert (NUM_V_MUST_DEFS (v_must_defs) == 1
1029 || TREE_CODE (lhs) == SSA_NAME);
1031 /* We require the SSA version number of the lhs for the value_vector.
1032 Make sure we have it. */
1033 if (TREE_CODE (lhs) != SSA_NAME)
1035 /* If we make it here, then stmt only has one definition:
1037 lhs = V_MUST_DEF_RESULT (v_must_defs, 0);
1040 if (TREE_CODE (rhs) == SSA_NAME)
1042 /* For a simple copy operation, we copy the lattice values. */
1043 value *nval = get_value (rhs);
1046 else if (DECL_P (rhs)
1047 && NUM_VUSES (vuses) == 1
1048 && rhs == SSA_NAME_VAR (VUSE_OP (vuses, 0)))
1050 /* Same as above, but the rhs is not a gimple register and yet
1051 has a known VUSE. */
1052 value *nval = get_value (VUSE_OP (vuses, 0));
1057 /* Evaluate the statement. */
1058 val = evaluate_stmt (stmt);
1061 /* FIXME: Hack. If this was a definition of a bitfield, we need to widen
1062 the constant value into the type of the destination variable. This
1063 should not be necessary if GCC represented bitfields properly. */
1065 tree lhs = TREE_OPERAND (stmt, 0);
1066 if (val.lattice_val == CONSTANT
1067 && TREE_CODE (lhs) == COMPONENT_REF
1068 && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))
1070 tree w = widen_bitfield (val.const_val, TREE_OPERAND (lhs, 1), lhs);
1072 if (w && is_gimple_min_invariant (w))
1076 val.lattice_val = VARYING;
1077 val.const_val = NULL;
1082 /* If LHS is not a gimple register, then it cannot take on an
1084 if (!is_gimple_reg (SSA_NAME_VAR (lhs))
1085 && val.lattice_val == UNDEFINED)
1086 val.lattice_val = UNKNOWN_VAL;
1088 /* Set the lattice value of the statement's output. */
1089 if (set_lattice_value (lhs, val))
1092 if (val.lattice_val == VARYING)
1093 return SSA_PROP_VARYING;
1095 return SSA_PROP_INTERESTING;
1098 return SSA_PROP_NOT_INTERESTING;
1102 /* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING
1103 if it can determine which edge will be taken. Otherwise, return
1104 SSA_PROP_VARYING. */
1106 static enum ssa_prop_result
1107 visit_cond_stmt (tree stmt, edge *taken_edge_p)
1112 block = bb_for_stmt (stmt);
1113 val = evaluate_stmt (stmt);
1115 /* Find which edge out of the conditional block will be taken and add it
1116 to the worklist. If no single edge can be determined statically,
1117 return SSA_PROP_VARYING to feed all the outgoing edges to the
1118 propagation engine. */
1119 *taken_edge_p = val.const_val ? find_taken_edge (block, val.const_val) : 0;
1121 return SSA_PROP_INTERESTING;
1123 return SSA_PROP_VARYING;
1127 /* Evaluate statement STMT. If the statement produces an output value and
1128 its evaluation changes the lattice value of its output, return
1129 SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the
1132 If STMT is a conditional branch and we can determine its truth
1133 value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying
1134 value, return SSA_PROP_VARYING. */
1136 static enum ssa_prop_result
1137 ccp_visit_stmt (tree stmt, edge *taken_edge_p, tree *output_p)
1140 v_may_def_optype v_may_defs;
1141 v_must_def_optype v_must_defs;
1145 if (dump_file && (dump_flags & TDF_DETAILS))
1147 fprintf (dump_file, "\nVisiting statement: ");
1148 print_generic_stmt (dump_file, stmt, TDF_SLIM);
1149 fprintf (dump_file, "\n");
1152 ann = stmt_ann (stmt);
1154 v_must_defs = V_MUST_DEF_OPS (ann);
1155 v_may_defs = V_MAY_DEF_OPS (ann);
1156 if (TREE_CODE (stmt) == MODIFY_EXPR
1157 && NUM_V_MAY_DEFS (v_may_defs) == 0
1158 && (NUM_V_MUST_DEFS (v_must_defs) == 1
1159 || TREE_CODE (TREE_OPERAND (stmt, 0)) == SSA_NAME))
1161 /* If the statement is an assignment that produces a single
1162 output value, evaluate its RHS to see if the lattice value of
1163 its output has changed. */
1164 return visit_assignment (stmt, output_p);
1166 else if (TREE_CODE (stmt) == COND_EXPR || TREE_CODE (stmt) == SWITCH_EXPR)
1168 /* If STMT is a conditional branch, see if we can determine
1169 which branch will be taken. */
1170 return visit_cond_stmt (stmt, taken_edge_p);
1173 /* Any other kind of statement is not interesting for constant
1174 propagation and, therefore, not worth simulating. */
1175 if (dump_file && (dump_flags & TDF_DETAILS))
1176 fprintf (dump_file, "No interesting values produced. Marked VARYING.\n");
1178 /* Definitions made by statements other than assignments to
1179 SSA_NAMEs represent unknown modifications to their outputs.
1180 Mark them VARYING. */
1181 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
1182 def_to_varying (def);
1184 /* Mark all V_MAY_DEF operands VARYING. */
1185 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_VMAYDEF)
1186 def_to_varying (def);
1188 return SSA_PROP_VARYING;
1192 /* Main entry point for SSA Conditional Constant Propagation.
1194 [ DESCRIBE MAIN ALGORITHM HERE ] */
1197 execute_ssa_ccp (void)
1200 ssa_propagate (ccp_visit_stmt, ccp_visit_phi_node);
1208 return flag_tree_ccp != 0;
1212 struct tree_opt_pass pass_ccp =
1215 gate_ccp, /* gate */
1216 execute_ssa_ccp, /* execute */
1219 0, /* static_pass_number */
1220 TV_TREE_CCP, /* tv_id */
1221 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
1222 0, /* properties_provided */
1223 0, /* properties_destroyed */
1224 0, /* todo_flags_start */
1225 TODO_cleanup_cfg | TODO_dump_func | TODO_rename_vars
1226 | TODO_ggc_collect | TODO_verify_ssa
1227 | TODO_verify_stmts, /* todo_flags_finish */
1232 /* Given a constant value VAL for bitfield FIELD, and a destination
1233 variable VAR, return VAL appropriately widened to fit into VAR. If
1234 FIELD is wider than HOST_WIDE_INT, NULL is returned. */
1237 widen_bitfield (tree val, tree field, tree var)
1239 unsigned HOST_WIDE_INT var_size, field_size;
1241 unsigned HOST_WIDE_INT mask;
1244 /* We can only do this if the size of the type and field and VAL are
1245 all constants representable in HOST_WIDE_INT. */
1246 if (!host_integerp (TYPE_SIZE (TREE_TYPE (var)), 1)
1247 || !host_integerp (DECL_SIZE (field), 1)
1248 || !host_integerp (val, 0))
1251 var_size = tree_low_cst (TYPE_SIZE (TREE_TYPE (var)), 1);
1252 field_size = tree_low_cst (DECL_SIZE (field), 1);
1254 /* Give up if either the bitfield or the variable are too wide. */
1255 if (field_size > HOST_BITS_PER_WIDE_INT || var_size > HOST_BITS_PER_WIDE_INT)
1258 gcc_assert (var_size >= field_size);
1260 /* If the sign bit of the value is not set or the field's type is unsigned,
1261 just mask off the high order bits of the value. */
1262 if (DECL_UNSIGNED (field)
1263 || !(tree_low_cst (val, 0) & (((HOST_WIDE_INT)1) << (field_size - 1))))
1265 /* Zero extension. Build a mask with the lower 'field_size' bits
1266 set and a BIT_AND_EXPR node to clear the high order bits of
1268 for (i = 0, mask = 0; i < field_size; i++)
1269 mask |= ((HOST_WIDE_INT) 1) << i;
1271 wide_val = build (BIT_AND_EXPR, TREE_TYPE (var), val,
1272 fold_convert (TREE_TYPE (var),
1273 build_int_cst (NULL_TREE, mask)));
1277 /* Sign extension. Create a mask with the upper 'field_size'
1278 bits set and a BIT_IOR_EXPR to set the high order bits of the
1280 for (i = 0, mask = 0; i < (var_size - field_size); i++)
1281 mask |= ((HOST_WIDE_INT) 1) << (var_size - i - 1);
1283 wide_val = build (BIT_IOR_EXPR, TREE_TYPE (var), val,
1284 fold_convert (TREE_TYPE (var),
1285 build_int_cst (NULL_TREE, mask)));
1288 return fold (wide_val);
1292 /* A subroutine of fold_stmt_r. Attempts to fold *(A+O) to A[X].
1293 BASE is an array type. OFFSET is a byte displacement. ORIG_TYPE
1294 is the desired result type. */
1297 maybe_fold_offset_to_array_ref (tree base, tree offset, tree orig_type)
1299 tree min_idx, idx, elt_offset = integer_zero_node;
1300 tree array_type, elt_type, elt_size;
1302 /* If BASE is an ARRAY_REF, we can pick up another offset (this time
1303 measured in units of the size of elements type) from that ARRAY_REF).
1304 We can't do anything if either is variable.
1306 The case we handle here is *(&A[N]+O). */
1307 if (TREE_CODE (base) == ARRAY_REF)
1309 tree low_bound = array_ref_low_bound (base);
1311 elt_offset = TREE_OPERAND (base, 1);
1312 if (TREE_CODE (low_bound) != INTEGER_CST
1313 || TREE_CODE (elt_offset) != INTEGER_CST)
1316 elt_offset = int_const_binop (MINUS_EXPR, elt_offset, low_bound, 0);
1317 base = TREE_OPERAND (base, 0);
1320 /* Ignore stupid user tricks of indexing non-array variables. */
1321 array_type = TREE_TYPE (base);
1322 if (TREE_CODE (array_type) != ARRAY_TYPE)
1324 elt_type = TREE_TYPE (array_type);
1325 if (!lang_hooks.types_compatible_p (orig_type, elt_type))
1328 /* If OFFSET and ELT_OFFSET are zero, we don't care about the size of the
1329 element type (so we can use the alignment if it's not constant).
1330 Otherwise, compute the offset as an index by using a division. If the
1331 division isn't exact, then don't do anything. */
1332 elt_size = TYPE_SIZE_UNIT (elt_type);
1333 if (integer_zerop (offset))
1335 if (TREE_CODE (elt_size) != INTEGER_CST)
1336 elt_size = size_int (TYPE_ALIGN (elt_type));
1338 idx = integer_zero_node;
1342 unsigned HOST_WIDE_INT lquo, lrem;
1343 HOST_WIDE_INT hquo, hrem;
1345 if (TREE_CODE (elt_size) != INTEGER_CST
1346 || div_and_round_double (TRUNC_DIV_EXPR, 1,
1347 TREE_INT_CST_LOW (offset),
1348 TREE_INT_CST_HIGH (offset),
1349 TREE_INT_CST_LOW (elt_size),
1350 TREE_INT_CST_HIGH (elt_size),
1351 &lquo, &hquo, &lrem, &hrem)
1355 idx = build_int_cst_wide (NULL_TREE, lquo, hquo);
1358 /* Assume the low bound is zero. If there is a domain type, get the
1359 low bound, if any, convert the index into that type, and add the
1361 min_idx = integer_zero_node;
1362 if (TYPE_DOMAIN (array_type))
1364 if (TYPE_MIN_VALUE (TYPE_DOMAIN (array_type)))
1365 min_idx = TYPE_MIN_VALUE (TYPE_DOMAIN (array_type));
1367 min_idx = fold_convert (TYPE_DOMAIN (array_type), min_idx);
1369 if (TREE_CODE (min_idx) != INTEGER_CST)
1372 idx = fold_convert (TYPE_DOMAIN (array_type), idx);
1373 elt_offset = fold_convert (TYPE_DOMAIN (array_type), elt_offset);
1376 if (!integer_zerop (min_idx))
1377 idx = int_const_binop (PLUS_EXPR, idx, min_idx, 0);
1378 if (!integer_zerop (elt_offset))
1379 idx = int_const_binop (PLUS_EXPR, idx, elt_offset, 0);
1381 return build (ARRAY_REF, orig_type, base, idx, min_idx,
1382 size_int (tree_low_cst (elt_size, 1)
1383 / (TYPE_ALIGN_UNIT (elt_type))));
1387 /* A subroutine of fold_stmt_r. Attempts to fold *(S+O) to S.X.
1388 BASE is a record type. OFFSET is a byte displacement. ORIG_TYPE
1389 is the desired result type. */
1390 /* ??? This doesn't handle class inheritance. */
1393 maybe_fold_offset_to_component_ref (tree record_type, tree base, tree offset,
1394 tree orig_type, bool base_is_ptr)
1396 tree f, t, field_type, tail_array_field, field_offset;
1398 if (TREE_CODE (record_type) != RECORD_TYPE
1399 && TREE_CODE (record_type) != UNION_TYPE
1400 && TREE_CODE (record_type) != QUAL_UNION_TYPE)
1403 /* Short-circuit silly cases. */
1404 if (lang_hooks.types_compatible_p (record_type, orig_type))
1407 tail_array_field = NULL_TREE;
1408 for (f = TYPE_FIELDS (record_type); f ; f = TREE_CHAIN (f))
1412 if (TREE_CODE (f) != FIELD_DECL)
1414 if (DECL_BIT_FIELD (f))
1417 field_offset = byte_position (f);
1418 if (TREE_CODE (field_offset) != INTEGER_CST)
1421 /* ??? Java creates "interesting" fields for representing base classes.
1422 They have no name, and have no context. With no context, we get into
1423 trouble with nonoverlapping_component_refs_p. Skip them. */
1424 if (!DECL_FIELD_CONTEXT (f))
1427 /* The previous array field isn't at the end. */
1428 tail_array_field = NULL_TREE;
1430 /* Check to see if this offset overlaps with the field. */
1431 cmp = tree_int_cst_compare (field_offset, offset);
1435 field_type = TREE_TYPE (f);
1438 /* Don't care about offsets into the middle of scalars. */
1439 if (!AGGREGATE_TYPE_P (field_type))
1442 /* Check for array at the end of the struct. This is often
1443 used as for flexible array members. We should be able to
1444 turn this into an array access anyway. */
1445 if (TREE_CODE (field_type) == ARRAY_TYPE)
1446 tail_array_field = f;
1448 /* Check the end of the field against the offset. */
1449 if (!DECL_SIZE_UNIT (f)
1450 || TREE_CODE (DECL_SIZE_UNIT (f)) != INTEGER_CST)
1452 t = int_const_binop (MINUS_EXPR, offset, DECL_FIELD_OFFSET (f), 1);
1453 if (!tree_int_cst_lt (t, DECL_SIZE_UNIT (f)))
1456 /* If we matched, then set offset to the displacement into
1461 /* Here we exactly match the offset being checked. If the types match,
1462 then we can return that field. */
1463 else if (lang_hooks.types_compatible_p (orig_type, field_type))
1466 base = build1 (INDIRECT_REF, record_type, base);
1467 t = build (COMPONENT_REF, field_type, base, f, NULL_TREE);
1471 /* Don't care about type-punning of scalars. */
1472 else if (!AGGREGATE_TYPE_P (field_type))
1478 if (!tail_array_field)
1481 f = tail_array_field;
1482 field_type = TREE_TYPE (f);
1485 /* If we get here, we've got an aggregate field, and a possibly
1486 nonzero offset into them. Recurse and hope for a valid match. */
1488 base = build1 (INDIRECT_REF, record_type, base);
1489 base = build (COMPONENT_REF, field_type, base, f, NULL_TREE);
1491 t = maybe_fold_offset_to_array_ref (base, offset, orig_type);
1494 return maybe_fold_offset_to_component_ref (field_type, base, offset,
1499 /* A subroutine of fold_stmt_r. Attempt to simplify *(BASE+OFFSET).
1500 Return the simplified expression, or NULL if nothing could be done. */
1503 maybe_fold_stmt_indirect (tree expr, tree base, tree offset)
1507 /* We may well have constructed a double-nested PLUS_EXPR via multiple
1508 substitutions. Fold that down to one. Remove NON_LVALUE_EXPRs that
1509 are sometimes added. */
1512 TREE_OPERAND (expr, 0) = base;
1514 /* One possibility is that the address reduces to a string constant. */
1515 t = fold_read_from_constant_string (expr);
1519 /* Add in any offset from a PLUS_EXPR. */
1520 if (TREE_CODE (base) == PLUS_EXPR)
1524 offset2 = TREE_OPERAND (base, 1);
1525 if (TREE_CODE (offset2) != INTEGER_CST)
1527 base = TREE_OPERAND (base, 0);
1529 offset = int_const_binop (PLUS_EXPR, offset, offset2, 1);
1532 if (TREE_CODE (base) == ADDR_EXPR)
1534 /* Strip the ADDR_EXPR. */
1535 base = TREE_OPERAND (base, 0);
1537 /* Fold away CONST_DECL to its value, if the type is scalar. */
1538 if (TREE_CODE (base) == CONST_DECL
1539 && is_gimple_min_invariant (DECL_INITIAL (base)))
1540 return DECL_INITIAL (base);
1542 /* Try folding *(&B+O) to B[X]. */
1543 t = maybe_fold_offset_to_array_ref (base, offset, TREE_TYPE (expr));
1547 /* Try folding *(&B+O) to B.X. */
1548 t = maybe_fold_offset_to_component_ref (TREE_TYPE (base), base, offset,
1549 TREE_TYPE (expr), false);
1553 /* Fold *&B to B. We can only do this if EXPR is the same type
1554 as BASE. We can't do this if EXPR is the element type of an array
1555 and BASE is the array. */
1556 if (integer_zerop (offset)
1557 && lang_hooks.types_compatible_p (TREE_TYPE (base),
1563 /* We can get here for out-of-range string constant accesses,
1564 such as "_"[3]. Bail out of the entire substitution search
1565 and arrange for the entire statement to be replaced by a
1566 call to __builtin_trap. In all likelyhood this will all be
1567 constant-folded away, but in the meantime we can't leave with
1568 something that get_expr_operands can't understand. */
1572 if (TREE_CODE (t) == ADDR_EXPR
1573 && TREE_CODE (TREE_OPERAND (t, 0)) == STRING_CST)
1575 /* FIXME: Except that this causes problems elsewhere with dead
1576 code not being deleted, and we abort in the rtl expanders
1577 because we failed to remove some ssa_name. In the meantime,
1578 just return zero. */
1579 /* FIXME2: This condition should be signaled by
1580 fold_read_from_constant_string directly, rather than
1581 re-checking for it here. */
1582 return integer_zero_node;
1585 /* Try folding *(B+O) to B->X. Still an improvement. */
1586 if (POINTER_TYPE_P (TREE_TYPE (base)))
1588 t = maybe_fold_offset_to_component_ref (TREE_TYPE (TREE_TYPE (base)),
1590 TREE_TYPE (expr), true);
1596 /* Otherwise we had an offset that we could not simplify. */
1601 /* A subroutine of fold_stmt_r. EXPR is a PLUS_EXPR.
1603 A quaint feature extant in our address arithmetic is that there
1604 can be hidden type changes here. The type of the result need
1605 not be the same as the type of the input pointer.
1607 What we're after here is an expression of the form
1608 (T *)(&array + const)
1609 where the cast doesn't actually exist, but is implicit in the
1610 type of the PLUS_EXPR. We'd like to turn this into
1612 which may be able to propagate further. */
1615 maybe_fold_stmt_addition (tree expr)
1617 tree op0 = TREE_OPERAND (expr, 0);
1618 tree op1 = TREE_OPERAND (expr, 1);
1619 tree ptr_type = TREE_TYPE (expr);
1622 bool subtract = (TREE_CODE (expr) == MINUS_EXPR);
1624 /* We're only interested in pointer arithmetic. */
1625 if (!POINTER_TYPE_P (ptr_type))
1627 /* Canonicalize the integral operand to op1. */
1628 if (INTEGRAL_TYPE_P (TREE_TYPE (op0)))
1632 t = op0, op0 = op1, op1 = t;
1634 /* It had better be a constant. */
1635 if (TREE_CODE (op1) != INTEGER_CST)
1637 /* The first operand should be an ADDR_EXPR. */
1638 if (TREE_CODE (op0) != ADDR_EXPR)
1640 op0 = TREE_OPERAND (op0, 0);
1642 /* If the first operand is an ARRAY_REF, expand it so that we can fold
1643 the offset into it. */
1644 while (TREE_CODE (op0) == ARRAY_REF)
1646 tree array_obj = TREE_OPERAND (op0, 0);
1647 tree array_idx = TREE_OPERAND (op0, 1);
1648 tree elt_type = TREE_TYPE (op0);
1649 tree elt_size = TYPE_SIZE_UNIT (elt_type);
1652 if (TREE_CODE (array_idx) != INTEGER_CST)
1654 if (TREE_CODE (elt_size) != INTEGER_CST)
1657 /* Un-bias the index by the min index of the array type. */
1658 min_idx = TYPE_DOMAIN (TREE_TYPE (array_obj));
1661 min_idx = TYPE_MIN_VALUE (min_idx);
1664 if (TREE_CODE (min_idx) != INTEGER_CST)
1667 array_idx = convert (TREE_TYPE (min_idx), array_idx);
1668 if (!integer_zerop (min_idx))
1669 array_idx = int_const_binop (MINUS_EXPR, array_idx,
1674 /* Convert the index to a byte offset. */
1675 array_idx = convert (sizetype, array_idx);
1676 array_idx = int_const_binop (MULT_EXPR, array_idx, elt_size, 0);
1678 /* Update the operands for the next round, or for folding. */
1679 /* If we're manipulating unsigned types, then folding into negative
1680 values can produce incorrect results. Particularly if the type
1681 is smaller than the width of the pointer. */
1683 && TYPE_UNSIGNED (TREE_TYPE (op1))
1684 && tree_int_cst_lt (array_idx, op1))
1686 op1 = int_const_binop (subtract ? MINUS_EXPR : PLUS_EXPR,
1692 /* If we weren't able to fold the subtraction into another array reference,
1693 canonicalize the integer for passing to the array and component ref
1694 simplification functions. */
1697 if (TYPE_UNSIGNED (TREE_TYPE (op1)))
1699 op1 = fold (build1 (NEGATE_EXPR, TREE_TYPE (op1), op1));
1700 /* ??? In theory fold should always produce another integer. */
1701 if (TREE_CODE (op1) != INTEGER_CST)
1705 ptd_type = TREE_TYPE (ptr_type);
1707 /* At which point we can try some of the same things as for indirects. */
1708 t = maybe_fold_offset_to_array_ref (op0, op1, ptd_type);
1710 t = maybe_fold_offset_to_component_ref (TREE_TYPE (op0), op0, op1,
1713 t = build1 (ADDR_EXPR, ptr_type, t);
1719 /* Subroutine of fold_stmt called via walk_tree. We perform several
1720 simplifications of EXPR_P, mostly having to do with pointer arithmetic. */
1723 fold_stmt_r (tree *expr_p, int *walk_subtrees, void *data)
1725 bool *changed_p = data;
1726 tree expr = *expr_p, t;
1728 /* ??? It'd be nice if walk_tree had a pre-order option. */
1729 switch (TREE_CODE (expr))
1732 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1737 t = maybe_fold_stmt_indirect (expr, TREE_OPERAND (expr, 0),
1741 /* ??? Could handle ARRAY_REF here, as a variant of INDIRECT_REF.
1742 We'd only want to bother decomposing an existing ARRAY_REF if
1743 the base array is found to have another offset contained within.
1744 Otherwise we'd be wasting time. */
1747 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1752 /* Set TREE_INVARIANT properly so that the value is properly
1753 considered constant, and so gets propagated as expected. */
1755 recompute_tree_invarant_for_addr_expr (expr);
1760 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1763 t = walk_tree (&TREE_OPERAND (expr, 1), fold_stmt_r, data, NULL);
1768 t = maybe_fold_stmt_addition (expr);
1772 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1777 /* Make sure the FIELD_DECL is actually a field in the type on the lhs.
1778 We've already checked that the records are compatible, so we should
1779 come up with a set of compatible fields. */
1781 tree expr_record = TREE_TYPE (TREE_OPERAND (expr, 0));
1782 tree expr_field = TREE_OPERAND (expr, 1);
1784 if (DECL_FIELD_CONTEXT (expr_field) != TYPE_MAIN_VARIANT (expr_record))
1786 expr_field = find_compatible_field (expr_record, expr_field);
1787 TREE_OPERAND (expr, 1) = expr_field;
1806 /* Return the string length of ARG in LENGTH. If ARG is an SSA name variable,
1807 follow its use-def chains. If LENGTH is not NULL and its value is not
1808 equal to the length we determine, or if we are unable to determine the
1809 length, return false. VISITED is a bitmap of visited variables. */
1812 get_strlen (tree arg, tree *length, bitmap visited)
1814 tree var, def_stmt, val;
1816 if (TREE_CODE (arg) != SSA_NAME)
1818 val = c_strlen (arg, 1);
1822 if (*length && simple_cst_equal (val, *length) != 1)
1829 /* If we were already here, break the infinite cycle. */
1830 if (bitmap_bit_p (visited, SSA_NAME_VERSION (arg)))
1832 bitmap_set_bit (visited, SSA_NAME_VERSION (arg));
1835 def_stmt = SSA_NAME_DEF_STMT (var);
1837 switch (TREE_CODE (def_stmt))
1843 /* The RHS of the statement defining VAR must either have a
1844 constant length or come from another SSA_NAME with a constant
1846 rhs = TREE_OPERAND (def_stmt, 1);
1848 if (TREE_CODE (rhs) == SSA_NAME)
1849 return get_strlen (rhs, length, visited);
1851 /* See if the RHS is a constant length. */
1852 len = c_strlen (rhs, 1);
1855 if (*length && simple_cst_equal (len, *length) != 1)
1867 /* All the arguments of the PHI node must have the same constant
1871 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
1873 tree arg = PHI_ARG_DEF (def_stmt, i);
1875 /* If this PHI has itself as an argument, we cannot
1876 determine the string length of this argument. However,
1877 if we can find a constant string length for the other
1878 PHI args then we can still be sure that this is a
1879 constant string length. So be optimistic and just
1880 continue with the next argument. */
1881 if (arg == PHI_RESULT (def_stmt))
1884 if (!get_strlen (arg, length, visited))
1900 /* Fold builtin call FN in statement STMT. If it cannot be folded into a
1901 constant, return NULL_TREE. Otherwise, return its constant value. */
1904 ccp_fold_builtin (tree stmt, tree fn)
1906 tree result, strlen_val[2];
1907 tree callee, arglist, a;
1912 ignore = TREE_CODE (stmt) != MODIFY_EXPR;
1914 /* First try the generic builtin folder. If that succeeds, return the
1916 result = fold_builtin (fn, ignore);
1920 STRIP_NOPS (result);
1924 /* Ignore MD builtins. */
1925 callee = get_callee_fndecl (fn);
1926 if (DECL_BUILT_IN_CLASS (callee) == BUILT_IN_MD)
1929 /* If the builtin could not be folded, and it has no argument list,
1931 arglist = TREE_OPERAND (fn, 1);
1935 /* Limit the work only for builtins we know how to simplify. */
1936 switch (DECL_FUNCTION_CODE (callee))
1938 case BUILT_IN_STRLEN:
1939 case BUILT_IN_FPUTS:
1940 case BUILT_IN_FPUTS_UNLOCKED:
1943 case BUILT_IN_STRCPY:
1944 case BUILT_IN_STRNCPY:
1951 /* Try to use the dataflow information gathered by the CCP process. */
1952 visited = BITMAP_XMALLOC ();
1954 memset (strlen_val, 0, sizeof (strlen_val));
1955 for (i = 0, a = arglist;
1957 i++, strlen_arg >>= 1, a = TREE_CHAIN (a))
1960 bitmap_clear (visited);
1961 if (!get_strlen (TREE_VALUE (a), &strlen_val[i], visited))
1962 strlen_val[i] = NULL_TREE;
1965 BITMAP_XFREE (visited);
1968 switch (DECL_FUNCTION_CODE (callee))
1970 case BUILT_IN_STRLEN:
1973 tree new = fold_convert (TREE_TYPE (fn), strlen_val[0]);
1975 /* If the result is not a valid gimple value, or not a cast
1976 of a valid gimple value, then we can not use the result. */
1977 if (is_gimple_val (new)
1978 || (is_gimple_cast (new)
1979 && is_gimple_val (TREE_OPERAND (new, 0))))
1984 case BUILT_IN_STRCPY:
1985 if (strlen_val[1] && is_gimple_val (strlen_val[1]))
1986 result = fold_builtin_strcpy (fn, strlen_val[1]);
1989 case BUILT_IN_STRNCPY:
1990 if (strlen_val[1] && is_gimple_val (strlen_val[1]))
1991 result = fold_builtin_strncpy (fn, strlen_val[1]);
1994 case BUILT_IN_FPUTS:
1995 result = fold_builtin_fputs (arglist,
1996 TREE_CODE (stmt) != MODIFY_EXPR, 0,
2000 case BUILT_IN_FPUTS_UNLOCKED:
2001 result = fold_builtin_fputs (arglist,
2002 TREE_CODE (stmt) != MODIFY_EXPR, 1,
2010 if (result && ignore)
2011 result = fold_ignored_result (result);
2016 /* Fold the statement pointed by STMT_P. In some cases, this function may
2017 replace the whole statement with a new one. Returns true iff folding
2018 makes any changes. */
2021 fold_stmt (tree *stmt_p)
2023 tree rhs, result, stmt;
2024 bool changed = false;
2028 /* If we replaced constants and the statement makes pointer dereferences,
2029 then we may need to fold instances of *&VAR into VAR, etc. */
2030 if (walk_tree (stmt_p, fold_stmt_r, &changed, NULL))
2033 = build_function_call_expr (implicit_built_in_decls[BUILT_IN_TRAP],
2038 rhs = get_rhs (stmt);
2043 if (TREE_CODE (rhs) == CALL_EXPR)
2047 /* Check for builtins that CCP can handle using information not
2048 available in the generic fold routines. */
2049 callee = get_callee_fndecl (rhs);
2050 if (callee && DECL_BUILT_IN (callee))
2051 result = ccp_fold_builtin (stmt, rhs);
2054 /* Check for resolvable OBJ_TYPE_REF. The only sorts we can resolve
2055 here are when we've propagated the address of a decl into the
2057 /* ??? Should perhaps do this in fold proper. However, doing it
2058 there requires that we create a new CALL_EXPR, and that requires
2059 copying EH region info to the new node. Easier to just do it
2060 here where we can just smash the call operand. */
2061 callee = TREE_OPERAND (rhs, 0);
2062 if (TREE_CODE (callee) == OBJ_TYPE_REF
2063 && lang_hooks.fold_obj_type_ref
2064 && TREE_CODE (OBJ_TYPE_REF_OBJECT (callee)) == ADDR_EXPR
2065 && DECL_P (TREE_OPERAND
2066 (OBJ_TYPE_REF_OBJECT (callee), 0)))
2070 /* ??? Caution: Broken ADDR_EXPR semantics means that
2071 looking at the type of the operand of the addr_expr
2072 can yield an array type. See silly exception in
2073 check_pointer_types_r. */
2075 t = TREE_TYPE (TREE_TYPE (OBJ_TYPE_REF_OBJECT (callee)));
2076 t = lang_hooks.fold_obj_type_ref (callee, t);
2079 TREE_OPERAND (rhs, 0) = t;
2086 /* If we couldn't fold the RHS, hand over to the generic fold routines. */
2087 if (result == NULL_TREE)
2088 result = fold (rhs);
2090 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
2091 may have been added by fold, and "useless" type conversions that might
2092 now be apparent due to propagation. */
2093 STRIP_USELESS_TYPE_CONVERSION (result);
2096 changed |= set_rhs (stmt_p, result);
2102 /* Convert EXPR into a GIMPLE value suitable for substitution on the
2103 RHS of an assignment. Insert the necessary statements before
2107 convert_to_gimple_builtin (block_stmt_iterator *si_p, tree expr)
2109 tree_stmt_iterator ti;
2110 tree stmt = bsi_stmt (*si_p);
2111 tree tmp, stmts = NULL;
2113 push_gimplify_context ();
2114 tmp = get_initialized_tmp_var (expr, &stmts, NULL);
2115 pop_gimplify_context (NULL);
2117 /* The replacement can expose previously unreferenced variables. */
2118 for (ti = tsi_start (stmts); !tsi_end_p (ti); tsi_next (&ti))
2120 find_new_referenced_vars (tsi_stmt_ptr (ti));
2121 mark_new_vars_to_rename (tsi_stmt (ti), vars_to_rename);
2124 if (EXPR_HAS_LOCATION (stmt))
2125 annotate_all_with_locus (&stmts, EXPR_LOCATION (stmt));
2127 bsi_insert_before (si_p, stmts, BSI_SAME_STMT);
2133 /* A simple pass that attempts to fold all builtin functions. This pass
2134 is run after we've propagated as many constants as we can. */
2137 execute_fold_all_builtins (void)
2139 bool cfg_changed = false;
2143 block_stmt_iterator i;
2144 for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
2146 tree *stmtp = bsi_stmt_ptr (i);
2147 tree call = get_rhs (*stmtp);
2148 tree callee, result;
2150 if (!call || TREE_CODE (call) != CALL_EXPR)
2152 callee = get_callee_fndecl (call);
2153 if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)
2156 result = ccp_fold_builtin (*stmtp, call);
2158 switch (DECL_FUNCTION_CODE (callee))
2160 case BUILT_IN_CONSTANT_P:
2161 /* Resolve __builtin_constant_p. If it hasn't been
2162 folded to integer_one_node by now, it's fairly
2163 certain that the value simply isn't constant. */
2164 result = integer_zero_node;
2171 if (dump_file && (dump_flags & TDF_DETAILS))
2173 fprintf (dump_file, "Simplified\n ");
2174 print_generic_stmt (dump_file, *stmtp, dump_flags);
2177 if (!set_rhs (stmtp, result))
2179 result = convert_to_gimple_builtin (&i, result);
2180 if (result && !set_rhs (stmtp, result))
2183 modify_stmt (*stmtp);
2184 if (maybe_clean_eh_stmt (*stmtp)
2185 && tree_purge_dead_eh_edges (bb))
2188 if (dump_file && (dump_flags & TDF_DETAILS))
2190 fprintf (dump_file, "to\n ");
2191 print_generic_stmt (dump_file, *stmtp, dump_flags);
2192 fprintf (dump_file, "\n");
2197 /* Delete unreachable blocks. */
2199 cleanup_tree_cfg ();
2203 struct tree_opt_pass pass_fold_builtins =
2207 execute_fold_all_builtins, /* execute */
2210 0, /* static_pass_number */
2212 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
2213 0, /* properties_provided */
2214 0, /* properties_destroyed */
2215 0, /* todo_flags_start */
2218 | TODO_rename_vars, /* todo_flags_finish */