1 /* Conditional constant propagation pass for the GNU compiler.
2 Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005
3 Free Software Foundation, Inc.
4 Adapted from original RTL SSA-CCP by Daniel Berlin <dberlin@dberlin.org>
5 Adapted to GIMPLE trees by Diego Novillo <dnovillo@redhat.com>
7 This file is part of GCC.
9 GCC is free software; you can redistribute it and/or modify it
10 under the terms of the GNU General Public License as published by the
11 Free Software Foundation; either version 2, or (at your option) any
14 GCC is distributed in the hope that it will be useful, but WITHOUT
15 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
16 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
19 You should have received a copy of the GNU General Public License
20 along with GCC; see the file COPYING. If not, write to the Free
21 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
24 /* Conditional constant propagation.
28 Constant propagation with conditional branches,
29 Wegman and Zadeck, ACM TOPLAS 13(2):181-210.
31 Building an Optimizing Compiler,
32 Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9.
34 Advanced Compiler Design and Implementation,
35 Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */
39 #include "coretypes.h"
46 #include "basic-block.h"
51 #include "diagnostic.h"
53 #include "tree-dump.h"
54 #include "tree-flow.h"
55 #include "tree-pass.h"
56 #include "tree-ssa-propagate.h"
57 #include "langhooks.h"
60 /* Possible lattice values. */
70 /* Main structure for CCP. Contains the lattice value and, if it's a
71 constant, the constant value. */
74 latticevalue lattice_val;
78 /* This is used to track the current value of each variable. */
79 static value *value_vector;
82 /* Dump lattice value VAL to file OUTF prefixed by PREFIX. */
85 dump_lattice_value (FILE *outf, const char *prefix, value val)
87 switch (val.lattice_val)
90 fprintf (outf, "%sUNDEFINED", prefix);
93 fprintf (outf, "%sVARYING", prefix);
96 fprintf (outf, "%sUNKNOWN_VAL", prefix);
99 fprintf (outf, "%sCONSTANT ", prefix);
100 print_generic_expr (outf, val.const_val, dump_flags);
108 /* Return a default value for variable VAR using the following rules:
110 1- Function arguments are considered VARYING.
112 2- Global and static variables that are declared constant are
115 3- Any other virtually defined variable is considered UNKNOWN_VAL.
117 4- Any other value is considered UNDEFINED. This is useful when
118 considering PHI nodes. PHI arguments that are undefined do not
119 change the constant value of the PHI node, which allows for more
120 constants to be propagated. */
123 get_default_value (tree var)
128 if (TREE_CODE (var) == SSA_NAME)
129 sym = SSA_NAME_VAR (var);
132 gcc_assert (DECL_P (var));
136 val.lattice_val = UNDEFINED;
137 val.const_val = NULL_TREE;
139 if (TREE_CODE (var) == SSA_NAME
140 && SSA_NAME_VALUE (var)
141 && is_gimple_min_invariant (SSA_NAME_VALUE (var)))
143 val.lattice_val = CONSTANT;
144 val.const_val = SSA_NAME_VALUE (var);
146 else if (TREE_CODE (sym) == PARM_DECL || TREE_THIS_VOLATILE (sym))
148 /* Function arguments and volatile variables are considered VARYING. */
149 val.lattice_val = VARYING;
151 else if (TREE_STATIC (sym))
153 /* Globals and static variables are considered UNKNOWN_VAL,
154 unless they are declared 'const'. */
155 if (TREE_READONLY (sym)
156 && DECL_INITIAL (sym)
157 && is_gimple_min_invariant (DECL_INITIAL (sym)))
159 val.lattice_val = CONSTANT;
160 val.const_val = DECL_INITIAL (sym);
164 val.const_val = NULL_TREE;
165 val.lattice_val = UNKNOWN_VAL;
168 else if (!is_gimple_reg (sym))
170 val.const_val = NULL_TREE;
171 val.lattice_val = UNKNOWN_VAL;
176 tree stmt = SSA_NAME_DEF_STMT (var);
178 if (!IS_EMPTY_STMT (stmt))
180 code = TREE_CODE (stmt);
181 if (code != MODIFY_EXPR && code != PHI_NODE)
182 val.lattice_val = VARYING;
189 /* Get the constant value associated with variable VAR. */
196 gcc_assert (TREE_CODE (var) == SSA_NAME);
198 val = &value_vector[SSA_NAME_VERSION (var)];
199 if (val->lattice_val == UNINITIALIZED)
200 *val = get_default_value (var);
206 /* Set the lattice value for variable VAR to VAL. Return true if VAL
207 is different from VAR's previous value. */
210 set_lattice_value (tree var, value val)
212 value *old = get_value (var);
214 if (val.lattice_val == UNDEFINED)
216 /* CONSTANT->UNDEFINED is never a valid state transition. */
217 gcc_assert (old->lattice_val != CONSTANT);
219 /* UNKNOWN_VAL->UNDEFINED is never a valid state transition. */
220 gcc_assert (old->lattice_val != UNKNOWN_VAL);
222 /* VARYING->UNDEFINED is generally not a valid state transition,
223 except for values which are initialized to VARYING. */
224 gcc_assert (old->lattice_val != VARYING
225 || get_default_value (var).lattice_val == VARYING);
227 else if (val.lattice_val == CONSTANT)
228 /* VARYING -> CONSTANT is an invalid state transition, except
229 for objects which start off in a VARYING state. */
230 gcc_assert (old->lattice_val != VARYING
231 || get_default_value (var).lattice_val == VARYING);
233 /* If the constant for VAR has changed, then this VAR is really varying. */
234 if (old->lattice_val == CONSTANT
235 && val.lattice_val == CONSTANT
236 && !simple_cst_equal (old->const_val, val.const_val))
238 val.lattice_val = VARYING;
239 val.const_val = NULL_TREE;
242 if (old->lattice_val != val.lattice_val)
244 if (dump_file && (dump_flags & TDF_DETAILS))
246 dump_lattice_value (dump_file, "Lattice value changed to ", val);
247 fprintf (dump_file, ". Adding definition to SSA edges.\n");
258 /* Set the lattice value for the variable VAR to VARYING. */
261 def_to_varying (tree var)
264 val.lattice_val = VARYING;
265 val.const_val = NULL_TREE;
266 set_lattice_value (var, val);
270 /* Return the likely latticevalue for STMT.
272 If STMT has no operands, then return CONSTANT.
274 Else if any operands of STMT are undefined, then return UNDEFINED.
276 Else if any operands of STMT are constants, then return CONSTANT.
278 Else return VARYING. */
281 likely_value (tree stmt)
284 int found_constant = 0;
289 /* If the statement makes aliased loads or has volatile operands, it
290 won't fold to a constant value. */
291 ann = stmt_ann (stmt);
292 if (ann->makes_aliased_loads || ann->has_volatile_ops)
295 /* A CALL_EXPR is assumed to be varying. This may be overly conservative,
296 in the presence of const and pure calls. */
297 if (get_call_expr_in (stmt) != NULL_TREE)
300 get_stmt_operands (stmt);
302 FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
304 value *val = get_value (use);
306 if (val->lattice_val == UNDEFINED)
309 if (val->lattice_val == CONSTANT)
313 vuses = VUSE_OPS (ann);
315 if (NUM_VUSES (vuses))
317 tree vuse = VUSE_OP (vuses, 0);
318 value *val = get_value (vuse);
320 if (val->lattice_val == UNKNOWN_VAL)
323 /* There should be no VUSE operands that are UNDEFINED. */
324 gcc_assert (val->lattice_val != UNDEFINED);
326 if (val->lattice_val == CONSTANT)
330 return ((found_constant || (!USE_OPS (ann) && !vuses)) ? CONSTANT : VARYING);
334 /* Function indicating whether we ought to include information for VAR
335 when calculating immediate uses. */
338 need_imm_uses_for (tree var)
340 return get_value (var)->lattice_val != VARYING;
344 /* Initialize local data structures for CCP. */
347 ccp_initialize (void)
352 value_vector = (value *) xmalloc (num_ssa_names * sizeof (value));
353 memset (value_vector, 0, num_ssa_names * sizeof (value));
355 /* Set of SSA_NAMEs that are defined by a V_MAY_DEF. */
356 is_may_def = sbitmap_alloc (num_ssa_names);
357 sbitmap_zero (is_may_def);
359 /* Initialize simulation flags for PHI nodes and statements. */
362 block_stmt_iterator i;
364 /* Mark all V_MAY_DEF operands VARYING. */
365 for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
367 bool is_varying = false;
368 tree stmt = bsi_stmt (i);
372 get_stmt_operands (stmt);
374 /* Get the default value for each DEF and V_MUST_DEF. */
375 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter,
376 (SSA_OP_DEF | SSA_OP_VMUSTDEF))
378 if (get_value (def)->lattice_val == VARYING)
382 /* Mark all V_MAY_DEF operands VARYING. */
383 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_VMAYDEF)
385 get_value (def)->lattice_val = VARYING;
386 SET_BIT (is_may_def, SSA_NAME_VERSION (def));
389 /* Statements other than MODIFY_EXPR, COND_EXPR and
390 SWITCH_EXPR are not interesting for constant propagation.
391 Mark them VARYING. */
392 if (TREE_CODE (stmt) != MODIFY_EXPR
393 && TREE_CODE (stmt) != COND_EXPR
394 && TREE_CODE (stmt) != SWITCH_EXPR)
397 DONT_SIMULATE_AGAIN (stmt) = is_varying;
401 /* Now process PHI nodes. */
407 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
409 value *val = get_value (PHI_RESULT (phi));
411 for (x = 0; x < PHI_NUM_ARGS (phi); x++)
413 var = PHI_ARG_DEF (phi, x);
415 /* If one argument has a V_MAY_DEF, the result is
417 if (TREE_CODE (var) == SSA_NAME)
419 if (TEST_BIT (is_may_def, SSA_NAME_VERSION (var)))
421 val->lattice_val = VARYING;
422 SET_BIT (is_may_def, SSA_NAME_VERSION (PHI_RESULT (phi)));
428 DONT_SIMULATE_AGAIN (phi) = (val->lattice_val == VARYING);
432 sbitmap_free (is_may_def);
434 /* Compute immediate uses for variables we care about. */
435 compute_immediate_uses (TDFA_USE_OPS | TDFA_USE_VOPS, need_imm_uses_for);
439 /* Replace USE references in statement STMT with their immediate reaching
440 definition. Return true if at least one reference was replaced. If
441 REPLACED_ADDRESSES_P is given, it will be set to true if an address
442 constant was replaced. */
445 replace_uses_in (tree stmt, bool *replaced_addresses_p)
447 bool replaced = false;
451 if (replaced_addresses_p)
452 *replaced_addresses_p = false;
454 get_stmt_operands (stmt);
456 FOR_EACH_SSA_USE_OPERAND (use, stmt, iter, SSA_OP_USE)
458 tree tuse = USE_FROM_PTR (use);
459 value *val = get_value (tuse);
461 if (val->lattice_val != CONSTANT)
464 if (TREE_CODE (stmt) == ASM_EXPR
465 && !may_propagate_copy_into_asm (tuse))
468 SET_USE (use, val->const_val);
471 if (POINTER_TYPE_P (TREE_TYPE (tuse)) && replaced_addresses_p)
472 *replaced_addresses_p = true;
479 /* Replace the VUSE references in statement STMT with its immediate reaching
480 definition. Return true if the reference was replaced. If
481 REPLACED_ADDRESSES_P is given, it will be set to true if an address
482 constant was replaced. */
485 replace_vuse_in (tree stmt, bool *replaced_addresses_p)
487 bool replaced = false;
492 if (replaced_addresses_p)
493 *replaced_addresses_p = false;
495 get_stmt_operands (stmt);
497 vuses = STMT_VUSE_OPS (stmt);
499 if (NUM_VUSES (vuses) != 1)
502 vuse = VUSE_OP_PTR (vuses, 0);
503 val = get_value (USE_FROM_PTR (vuse));
505 if (val->lattice_val == CONSTANT
506 && TREE_CODE (stmt) == MODIFY_EXPR
507 && DECL_P (TREE_OPERAND (stmt, 1))
508 && TREE_OPERAND (stmt, 1) == SSA_NAME_VAR (USE_FROM_PTR (vuse)))
510 TREE_OPERAND (stmt, 1) = val->const_val;
512 if (POINTER_TYPE_P (TREE_TYPE (USE_FROM_PTR (vuse)))
513 && replaced_addresses_p)
514 *replaced_addresses_p = true;
521 /* Perform final substitution and folding. After this pass the program
522 should still be in SSA form. */
525 substitute_and_fold (void)
530 if (dump_file && (dump_flags & TDF_DETAILS))
532 "\nSubstituing constants and folding statements\n\n");
534 /* Substitute constants in every statement of every basic block. */
537 block_stmt_iterator i;
540 /* Propagate our known constants into PHI nodes. */
541 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
545 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
548 use_operand_p orig_p = PHI_ARG_DEF_PTR (phi, i);
549 tree orig = USE_FROM_PTR (orig_p);
551 if (! SSA_VAR_P (orig))
554 new_val = get_value (orig);
555 if (new_val->lattice_val == CONSTANT
556 && may_propagate_copy (orig, new_val->const_val))
557 SET_USE (orig_p, new_val->const_val);
561 for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
563 bool replaced_address;
564 tree stmt = bsi_stmt (i);
566 /* Skip statements that have been folded already. */
567 if (stmt_modified_p (stmt) || !is_exec_stmt (stmt))
570 /* Replace the statement with its folded version and mark it
572 if (dump_file && (dump_flags & TDF_DETAILS))
574 fprintf (dump_file, "Line %d: replaced ", get_lineno (stmt));
575 print_generic_stmt (dump_file, stmt, TDF_SLIM);
578 if (replace_uses_in (stmt, &replaced_address)
579 || replace_vuse_in (stmt, &replaced_address))
581 bool changed = fold_stmt (bsi_stmt_ptr (i));
584 /* If we folded a builtin function, we'll likely
585 need to rename VDEFs. */
586 if (replaced_address || changed)
587 mark_new_vars_to_rename (stmt, vars_to_rename);
589 /* If we cleaned up EH information from the statement,
591 if (maybe_clean_eh_stmt (stmt))
592 tree_purge_dead_eh_edges (bb);
597 if (dump_file && (dump_flags & TDF_DETAILS))
599 fprintf (dump_file, " with ");
600 print_generic_stmt (dump_file, stmt, TDF_SLIM);
601 fprintf (dump_file, "\n");
606 /* And transfer what we learned from VALUE_VECTOR into the
607 SSA_NAMEs themselves. This probably isn't terribly important
608 since we probably constant propagated the values to their
610 for (i = 0; i < num_ssa_names; i++)
612 tree name = ssa_name (i);
618 value = get_value (name);
619 if (value->lattice_val == CONSTANT
620 && is_gimple_reg (name)
621 && is_gimple_min_invariant (value->const_val))
622 SSA_NAME_VALUE (name) = value->const_val;
627 /* Free allocated storage. */
632 /* Perform substitutions based on the known constant values. */
633 substitute_and_fold ();
640 /* Compute the meet operator between VAL1 and VAL2:
642 any M UNDEFINED = any
643 any M VARYING = VARYING
644 any M UNKNOWN_VAL = UNKNOWN_VAL
645 Ci M Cj = Ci if (i == j)
646 Ci M Cj = VARYING if (i != j) */
648 ccp_lattice_meet (value val1, value val2)
652 /* any M UNDEFINED = any. */
653 if (val1.lattice_val == UNDEFINED)
655 else if (val2.lattice_val == UNDEFINED)
658 /* any M VARYING = VARYING. */
659 if (val1.lattice_val == VARYING || val2.lattice_val == VARYING)
661 result.lattice_val = VARYING;
662 result.const_val = NULL_TREE;
666 /* any M UNKNOWN_VAL = UNKNOWN_VAL. */
667 if (val1.lattice_val == UNKNOWN_VAL
668 || val2.lattice_val == UNKNOWN_VAL)
670 result.lattice_val = UNKNOWN_VAL;
671 result.const_val = NULL_TREE;
675 /* Ci M Cj = Ci if (i == j)
676 Ci M Cj = VARYING if (i != j) */
677 if (simple_cst_equal (val1.const_val, val2.const_val) == 1)
679 result.lattice_val = CONSTANT;
680 result.const_val = val1.const_val;
684 result.lattice_val = VARYING;
685 result.const_val = NULL_TREE;
692 /* Loop through the PHI_NODE's parameters for BLOCK and compare their
693 lattice values to determine PHI_NODE's lattice value. The value of a
694 PHI node is determined calling ccp_lattice_meet() with all the arguments
695 of the PHI node that are incoming via executable edges. */
697 static enum ssa_prop_result
698 ccp_visit_phi_node (tree phi)
700 value new_val, *old_val;
703 if (dump_file && (dump_flags & TDF_DETAILS))
705 fprintf (dump_file, "\nVisiting PHI node: ");
706 print_generic_expr (dump_file, phi, dump_flags);
709 old_val = get_value (PHI_RESULT (phi));
710 switch (old_val->lattice_val)
713 return SSA_PROP_NOT_INTERESTING;
720 /* To avoid the default value of UNKNOWN_VAL overriding
721 that of its possible constant arguments, temporarily
722 set the PHI node's default lattice value to be
723 UNDEFINED. If the PHI node's old value was UNKNOWN_VAL and
724 the new value is UNDEFINED, then we prevent the invalid
725 transition by not calling set_lattice_value. */
726 new_val.lattice_val = UNDEFINED;
727 new_val.const_val = NULL_TREE;
732 new_val.lattice_val = UNDEFINED;
733 new_val.const_val = NULL_TREE;
740 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
742 /* Compute the meet operator over all the PHI arguments. */
743 edge e = PHI_ARG_EDGE (phi, i);
745 if (dump_file && (dump_flags & TDF_DETAILS))
748 "\n Argument #%d (%d -> %d %sexecutable)\n",
749 i, e->src->index, e->dest->index,
750 (e->flags & EDGE_EXECUTABLE) ? "" : "not ");
753 /* If the incoming edge is executable, Compute the meet operator for
754 the existing value of the PHI node and the current PHI argument. */
755 if (e->flags & EDGE_EXECUTABLE)
757 tree rdef = PHI_ARG_DEF (phi, i);
758 value *rdef_val, val;
760 if (is_gimple_min_invariant (rdef))
762 val.lattice_val = CONSTANT;
763 val.const_val = rdef;
767 rdef_val = get_value (rdef);
769 new_val = ccp_lattice_meet (new_val, *rdef_val);
771 if (dump_file && (dump_flags & TDF_DETAILS))
773 fprintf (dump_file, "\t");
774 print_generic_expr (dump_file, rdef, dump_flags);
775 dump_lattice_value (dump_file, "\tValue: ", *rdef_val);
776 fprintf (dump_file, "\n");
779 if (new_val.lattice_val == VARYING)
784 if (dump_file && (dump_flags & TDF_DETAILS))
786 dump_lattice_value (dump_file, "\n PHI node value: ", new_val);
787 fprintf (dump_file, "\n\n");
790 /* Check for an invalid change from UNKNOWN_VAL to UNDEFINED. */
791 if (old_val->lattice_val == UNKNOWN_VAL
792 && new_val.lattice_val == UNDEFINED)
793 return SSA_PROP_NOT_INTERESTING;
795 /* Otherwise, make the transition to the new value. */
796 if (set_lattice_value (PHI_RESULT (phi), new_val))
798 if (new_val.lattice_val == VARYING)
799 return SSA_PROP_VARYING;
801 return SSA_PROP_INTERESTING;
804 return SSA_PROP_NOT_INTERESTING;
808 /* CCP specific front-end to the non-destructive constant folding
811 Attempt to simplify the RHS of STMT knowing that one or more
812 operands are constants.
814 If simplification is possible, return the simplified RHS,
815 otherwise return the original RHS. */
820 tree rhs = get_rhs (stmt);
821 enum tree_code code = TREE_CODE (rhs);
822 enum tree_code_class kind = TREE_CODE_CLASS (code);
823 tree retval = NULL_TREE;
826 vuses = STMT_VUSE_OPS (stmt);
828 /* If the RHS is just a variable, then that variable must now have
829 a constant value that we can return directly. */
830 if (TREE_CODE (rhs) == SSA_NAME)
831 return get_value (rhs)->const_val;
832 else if (DECL_P (rhs)
833 && NUM_VUSES (vuses) == 1
834 && rhs == SSA_NAME_VAR (VUSE_OP (vuses, 0)))
835 return get_value (VUSE_OP (vuses, 0))->const_val;
837 /* Unary operators. Note that we know the single operand must
838 be a constant. So this should almost always return a
840 if (kind == tcc_unary)
842 /* Handle unary operators which can appear in GIMPLE form. */
843 tree op0 = TREE_OPERAND (rhs, 0);
845 /* Simplify the operand down to a constant. */
846 if (TREE_CODE (op0) == SSA_NAME)
848 value *val = get_value (op0);
849 if (val->lattice_val == CONSTANT)
850 op0 = get_value (op0)->const_val;
853 retval = fold_unary_to_constant (code, TREE_TYPE (rhs), op0);
855 /* If we folded, but did not create an invariant, then we can not
856 use this expression. */
857 if (retval && ! is_gimple_min_invariant (retval))
860 /* If we could not fold the expression, but the arguments are all
861 constants and gimple values, then build and return the new
864 In some cases the new expression is still something we can
865 use as a replacement for an argument. This happens with
866 NOP conversions of types for example.
868 In other cases the new expression can not be used as a
869 replacement for an argument (as it would create non-gimple
870 code). But the new expression can still be used to derive
872 if (! retval && is_gimple_min_invariant (op0))
873 return build1 (code, TREE_TYPE (rhs), op0);
876 /* Binary and comparison operators. We know one or both of the
877 operands are constants. */
878 else if (kind == tcc_binary
879 || kind == tcc_comparison
880 || code == TRUTH_AND_EXPR
881 || code == TRUTH_OR_EXPR
882 || code == TRUTH_XOR_EXPR)
884 /* Handle binary and comparison operators that can appear in
886 tree op0 = TREE_OPERAND (rhs, 0);
887 tree op1 = TREE_OPERAND (rhs, 1);
889 /* Simplify the operands down to constants when appropriate. */
890 if (TREE_CODE (op0) == SSA_NAME)
892 value *val = get_value (op0);
893 if (val->lattice_val == CONSTANT)
894 op0 = val->const_val;
897 if (TREE_CODE (op1) == SSA_NAME)
899 value *val = get_value (op1);
900 if (val->lattice_val == CONSTANT)
901 op1 = val->const_val;
904 retval = fold_binary_to_constant (code, TREE_TYPE (rhs), op0, op1);
906 /* If we folded, but did not create an invariant, then we can not
907 use this expression. */
908 if (retval && ! is_gimple_min_invariant (retval))
911 /* If we could not fold the expression, but the arguments are all
912 constants and gimple values, then build and return the new
915 In some cases the new expression is still something we can
916 use as a replacement for an argument. This happens with
917 NOP conversions of types for example.
919 In other cases the new expression can not be used as a
920 replacement for an argument (as it would create non-gimple
921 code). But the new expression can still be used to derive
924 && is_gimple_min_invariant (op0)
925 && is_gimple_min_invariant (op1))
926 return build (code, TREE_TYPE (rhs), op0, op1);
929 /* We may be able to fold away calls to builtin functions if their
930 arguments are constants. */
931 else if (code == CALL_EXPR
932 && TREE_CODE (TREE_OPERAND (rhs, 0)) == ADDR_EXPR
933 && (TREE_CODE (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0))
935 && DECL_BUILT_IN (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0)))
937 use_optype uses = STMT_USE_OPS (stmt);
938 if (NUM_USES (uses) != 0)
943 /* Preserve the original values of every operand. */
944 orig = xmalloc (sizeof (tree) * NUM_USES (uses));
945 for (i = 0; i < NUM_USES (uses); i++)
946 orig[i] = USE_OP (uses, i);
948 /* Substitute operands with their values and try to fold. */
949 replace_uses_in (stmt, NULL);
950 retval = fold_builtin (rhs, false);
952 /* Restore operands to their original form. */
953 for (i = 0; i < NUM_USES (uses); i++)
954 SET_USE_OP (uses, i, orig[i]);
961 /* If we got a simplified form, see if we need to convert its type. */
963 return fold_convert (TREE_TYPE (rhs), retval);
965 /* No simplification was possible. */
970 /* Evaluate statement STMT. */
973 evaluate_stmt (tree stmt)
977 latticevalue likelyvalue = likely_value (stmt);
979 /* If the statement is likely to have a CONSTANT result, then try
980 to fold the statement to determine the constant value. */
981 if (likelyvalue == CONSTANT)
982 simplified = ccp_fold (stmt);
983 /* If the statement is likely to have a VARYING result, then do not
984 bother folding the statement. */
985 else if (likelyvalue == VARYING)
986 simplified = get_rhs (stmt);
987 /* Otherwise the statement is likely to have an UNDEFINED value and
988 there will be nothing to do. */
990 simplified = NULL_TREE;
992 if (simplified && is_gimple_min_invariant (simplified))
994 /* The statement produced a constant value. */
995 val.lattice_val = CONSTANT;
996 val.const_val = simplified;
1000 /* The statement produced a nonconstant value. If the statement
1001 had undefined or virtual operands, then the result of the
1002 statement should be undefined or virtual respectively.
1003 Else the result of the statement is VARYING. */
1004 val.lattice_val = (likelyvalue == UNDEFINED ? UNDEFINED : VARYING);
1005 val.lattice_val = (likelyvalue == UNKNOWN_VAL
1006 ? UNKNOWN_VAL : val.lattice_val);
1007 val.const_val = NULL_TREE;
1014 /* Visit the assignment statement STMT. Set the value of its LHS to the
1015 value computed by the RHS and store LHS in *OUTPUT_P. */
1017 static enum ssa_prop_result
1018 visit_assignment (tree stmt, tree *output_p)
1023 v_must_def_optype v_must_defs;
1025 lhs = TREE_OPERAND (stmt, 0);
1026 rhs = TREE_OPERAND (stmt, 1);
1027 vuses = STMT_VUSE_OPS (stmt);
1028 v_must_defs = STMT_V_MUST_DEF_OPS (stmt);
1030 gcc_assert (NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) == 0);
1031 gcc_assert (NUM_V_MUST_DEFS (v_must_defs) == 1
1032 || TREE_CODE (lhs) == SSA_NAME);
1034 /* We require the SSA version number of the lhs for the value_vector.
1035 Make sure we have it. */
1036 if (TREE_CODE (lhs) != SSA_NAME)
1038 /* If we make it here, then stmt only has one definition:
1040 lhs = V_MUST_DEF_RESULT (v_must_defs, 0);
1043 if (TREE_CODE (rhs) == SSA_NAME)
1045 /* For a simple copy operation, we copy the lattice values. */
1046 value *nval = get_value (rhs);
1049 else if (DECL_P (rhs)
1050 && NUM_VUSES (vuses) == 1
1051 && rhs == SSA_NAME_VAR (VUSE_OP (vuses, 0)))
1053 /* Same as above, but the rhs is not a gimple register and yet
1054 has a known VUSE. */
1055 value *nval = get_value (VUSE_OP (vuses, 0));
1059 /* Evaluate the statement. */
1060 val = evaluate_stmt (stmt);
1062 /* If the original LHS was a VIEW_CONVERT_EXPR, modify the constant
1063 value to be a VIEW_CONVERT_EXPR of the old constant value. This is
1064 valid because a VIEW_CONVERT_EXPR is valid everywhere an operand of
1065 aggregate type is valid.
1067 ??? Also, if this was a definition of a bitfield, we need to widen
1068 the constant value into the type of the destination variable. This
1069 should not be necessary if GCC represented bitfields properly. */
1071 tree orig_lhs = TREE_OPERAND (stmt, 0);
1073 if (TREE_CODE (orig_lhs) == VIEW_CONVERT_EXPR
1074 && val.lattice_val == CONSTANT)
1076 val.const_val = build1 (VIEW_CONVERT_EXPR,
1077 TREE_TYPE (TREE_OPERAND (orig_lhs, 0)),
1079 orig_lhs = TREE_OPERAND (orig_lhs, 1);
1082 if (val.lattice_val == CONSTANT
1083 && TREE_CODE (orig_lhs) == COMPONENT_REF
1084 && DECL_BIT_FIELD (TREE_OPERAND (orig_lhs, 1)))
1086 tree w = widen_bitfield (val.const_val, TREE_OPERAND (orig_lhs, 1),
1089 if (w && is_gimple_min_invariant (w))
1093 val.lattice_val = VARYING;
1094 val.const_val = NULL;
1099 /* If LHS is not a gimple register, then it cannot take on an
1101 if (!is_gimple_reg (SSA_NAME_VAR (lhs))
1102 && val.lattice_val == UNDEFINED)
1103 val.lattice_val = UNKNOWN_VAL;
1105 /* Set the lattice value of the statement's output. */
1106 if (set_lattice_value (lhs, val))
1109 if (val.lattice_val == VARYING)
1110 return SSA_PROP_VARYING;
1112 return SSA_PROP_INTERESTING;
1115 return SSA_PROP_NOT_INTERESTING;
1119 /* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING
1120 if it can determine which edge will be taken. Otherwise, return
1121 SSA_PROP_VARYING. */
1123 static enum ssa_prop_result
1124 visit_cond_stmt (tree stmt, edge *taken_edge_p)
1129 block = bb_for_stmt (stmt);
1130 val = evaluate_stmt (stmt);
1132 /* Find which edge out of the conditional block will be taken and add it
1133 to the worklist. If no single edge can be determined statically,
1134 return SSA_PROP_VARYING to feed all the outgoing edges to the
1135 propagation engine. */
1136 *taken_edge_p = val.const_val ? find_taken_edge (block, val.const_val) : 0;
1138 return SSA_PROP_INTERESTING;
1140 return SSA_PROP_VARYING;
1144 /* Evaluate statement STMT. If the statement produces an output value and
1145 its evaluation changes the lattice value of its output, return
1146 SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the
1149 If STMT is a conditional branch and we can determine its truth
1150 value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying
1151 value, return SSA_PROP_VARYING. */
1153 static enum ssa_prop_result
1154 ccp_visit_stmt (tree stmt, edge *taken_edge_p, tree *output_p)
1157 v_may_def_optype v_may_defs;
1158 v_must_def_optype v_must_defs;
1162 if (dump_file && (dump_flags & TDF_DETAILS))
1164 fprintf (dump_file, "\nVisiting statement: ");
1165 print_generic_stmt (dump_file, stmt, TDF_SLIM);
1166 fprintf (dump_file, "\n");
1169 ann = stmt_ann (stmt);
1171 v_must_defs = V_MUST_DEF_OPS (ann);
1172 v_may_defs = V_MAY_DEF_OPS (ann);
1173 if (TREE_CODE (stmt) == MODIFY_EXPR
1174 && NUM_V_MAY_DEFS (v_may_defs) == 0
1175 && (NUM_V_MUST_DEFS (v_must_defs) == 1
1176 || TREE_CODE (TREE_OPERAND (stmt, 0)) == SSA_NAME))
1178 /* If the statement is an assignment that produces a single
1179 output value, evaluate its RHS to see if the lattice value of
1180 its output has changed. */
1181 return visit_assignment (stmt, output_p);
1183 else if (TREE_CODE (stmt) == COND_EXPR || TREE_CODE (stmt) == SWITCH_EXPR)
1185 /* If STMT is a conditional branch, see if we can determine
1186 which branch will be taken. */
1187 return visit_cond_stmt (stmt, taken_edge_p);
1190 /* Any other kind of statement is not interesting for constant
1191 propagation and, therefore, not worth simulating. */
1192 if (dump_file && (dump_flags & TDF_DETAILS))
1193 fprintf (dump_file, "No interesting values produced. Marked VARYING.\n");
1195 /* Definitions made by statements other than assignments to
1196 SSA_NAMEs represent unknown modifications to their outputs.
1197 Mark them VARYING. */
1198 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
1199 def_to_varying (def);
1201 /* Mark all V_MAY_DEF operands VARYING. */
1202 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_VMAYDEF)
1203 def_to_varying (def);
1205 return SSA_PROP_VARYING;
1209 /* Main entry point for SSA Conditional Constant Propagation.
1211 [ DESCRIBE MAIN ALGORITHM HERE ] */
1214 execute_ssa_ccp (void)
1217 ssa_propagate (ccp_visit_stmt, ccp_visit_phi_node);
1225 return flag_tree_ccp != 0;
1229 struct tree_opt_pass pass_ccp =
1232 gate_ccp, /* gate */
1233 execute_ssa_ccp, /* execute */
1236 0, /* static_pass_number */
1237 TV_TREE_CCP, /* tv_id */
1238 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
1239 0, /* properties_provided */
1240 0, /* properties_destroyed */
1241 0, /* todo_flags_start */
1242 TODO_cleanup_cfg | TODO_dump_func | TODO_rename_vars
1243 | TODO_ggc_collect | TODO_verify_ssa
1244 | TODO_verify_stmts, /* todo_flags_finish */
1249 /* Given a constant value VAL for bitfield FIELD, and a destination
1250 variable VAR, return VAL appropriately widened to fit into VAR. If
1251 FIELD is wider than HOST_WIDE_INT, NULL is returned. */
1254 widen_bitfield (tree val, tree field, tree var)
1256 unsigned HOST_WIDE_INT var_size, field_size;
1258 unsigned HOST_WIDE_INT mask;
1261 /* We can only do this if the size of the type and field and VAL are
1262 all constants representable in HOST_WIDE_INT. */
1263 if (!host_integerp (TYPE_SIZE (TREE_TYPE (var)), 1)
1264 || !host_integerp (DECL_SIZE (field), 1)
1265 || !host_integerp (val, 0))
1268 var_size = tree_low_cst (TYPE_SIZE (TREE_TYPE (var)), 1);
1269 field_size = tree_low_cst (DECL_SIZE (field), 1);
1271 /* Give up if either the bitfield or the variable are too wide. */
1272 if (field_size > HOST_BITS_PER_WIDE_INT || var_size > HOST_BITS_PER_WIDE_INT)
1275 gcc_assert (var_size >= field_size);
1277 /* If the sign bit of the value is not set or the field's type is unsigned,
1278 just mask off the high order bits of the value. */
1279 if (DECL_UNSIGNED (field)
1280 || !(tree_low_cst (val, 0) & (((HOST_WIDE_INT)1) << (field_size - 1))))
1282 /* Zero extension. Build a mask with the lower 'field_size' bits
1283 set and a BIT_AND_EXPR node to clear the high order bits of
1285 for (i = 0, mask = 0; i < field_size; i++)
1286 mask |= ((HOST_WIDE_INT) 1) << i;
1288 wide_val = build2 (BIT_AND_EXPR, TREE_TYPE (var), val,
1289 build_int_cst (TREE_TYPE (var), mask));
1293 /* Sign extension. Create a mask with the upper 'field_size'
1294 bits set and a BIT_IOR_EXPR to set the high order bits of the
1296 for (i = 0, mask = 0; i < (var_size - field_size); i++)
1297 mask |= ((HOST_WIDE_INT) 1) << (var_size - i - 1);
1299 wide_val = build2 (BIT_IOR_EXPR, TREE_TYPE (var), val,
1300 build_int_cst (TREE_TYPE (var), mask));
1303 return fold (wide_val);
1307 /* A subroutine of fold_stmt_r. Attempts to fold *(A+O) to A[X].
1308 BASE is an array type. OFFSET is a byte displacement. ORIG_TYPE
1309 is the desired result type. */
1312 maybe_fold_offset_to_array_ref (tree base, tree offset, tree orig_type)
1314 tree min_idx, idx, elt_offset = integer_zero_node;
1315 tree array_type, elt_type, elt_size;
1317 /* If BASE is an ARRAY_REF, we can pick up another offset (this time
1318 measured in units of the size of elements type) from that ARRAY_REF).
1319 We can't do anything if either is variable.
1321 The case we handle here is *(&A[N]+O). */
1322 if (TREE_CODE (base) == ARRAY_REF)
1324 tree low_bound = array_ref_low_bound (base);
1326 elt_offset = TREE_OPERAND (base, 1);
1327 if (TREE_CODE (low_bound) != INTEGER_CST
1328 || TREE_CODE (elt_offset) != INTEGER_CST)
1331 elt_offset = int_const_binop (MINUS_EXPR, elt_offset, low_bound, 0);
1332 base = TREE_OPERAND (base, 0);
1335 /* Ignore stupid user tricks of indexing non-array variables. */
1336 array_type = TREE_TYPE (base);
1337 if (TREE_CODE (array_type) != ARRAY_TYPE)
1339 elt_type = TREE_TYPE (array_type);
1340 if (!lang_hooks.types_compatible_p (orig_type, elt_type))
1343 /* If OFFSET and ELT_OFFSET are zero, we don't care about the size of the
1344 element type (so we can use the alignment if it's not constant).
1345 Otherwise, compute the offset as an index by using a division. If the
1346 division isn't exact, then don't do anything. */
1347 elt_size = TYPE_SIZE_UNIT (elt_type);
1348 if (integer_zerop (offset))
1350 if (TREE_CODE (elt_size) != INTEGER_CST)
1351 elt_size = size_int (TYPE_ALIGN (elt_type));
1353 idx = integer_zero_node;
1357 unsigned HOST_WIDE_INT lquo, lrem;
1358 HOST_WIDE_INT hquo, hrem;
1360 if (TREE_CODE (elt_size) != INTEGER_CST
1361 || div_and_round_double (TRUNC_DIV_EXPR, 1,
1362 TREE_INT_CST_LOW (offset),
1363 TREE_INT_CST_HIGH (offset),
1364 TREE_INT_CST_LOW (elt_size),
1365 TREE_INT_CST_HIGH (elt_size),
1366 &lquo, &hquo, &lrem, &hrem)
1370 idx = build_int_cst_wide (NULL_TREE, lquo, hquo);
1373 /* Assume the low bound is zero. If there is a domain type, get the
1374 low bound, if any, convert the index into that type, and add the
1376 min_idx = integer_zero_node;
1377 if (TYPE_DOMAIN (array_type))
1379 if (TYPE_MIN_VALUE (TYPE_DOMAIN (array_type)))
1380 min_idx = TYPE_MIN_VALUE (TYPE_DOMAIN (array_type));
1382 min_idx = fold_convert (TYPE_DOMAIN (array_type), min_idx);
1384 if (TREE_CODE (min_idx) != INTEGER_CST)
1387 idx = fold_convert (TYPE_DOMAIN (array_type), idx);
1388 elt_offset = fold_convert (TYPE_DOMAIN (array_type), elt_offset);
1391 if (!integer_zerop (min_idx))
1392 idx = int_const_binop (PLUS_EXPR, idx, min_idx, 0);
1393 if (!integer_zerop (elt_offset))
1394 idx = int_const_binop (PLUS_EXPR, idx, elt_offset, 0);
1396 return build (ARRAY_REF, orig_type, base, idx, min_idx,
1397 size_int (tree_low_cst (elt_size, 1)
1398 / (TYPE_ALIGN_UNIT (elt_type))));
1402 /* A subroutine of fold_stmt_r. Attempts to fold *(S+O) to S.X.
1403 BASE is a record type. OFFSET is a byte displacement. ORIG_TYPE
1404 is the desired result type. */
1405 /* ??? This doesn't handle class inheritance. */
1408 maybe_fold_offset_to_component_ref (tree record_type, tree base, tree offset,
1409 tree orig_type, bool base_is_ptr)
1411 tree f, t, field_type, tail_array_field, field_offset;
1413 if (TREE_CODE (record_type) != RECORD_TYPE
1414 && TREE_CODE (record_type) != UNION_TYPE
1415 && TREE_CODE (record_type) != QUAL_UNION_TYPE)
1418 /* Short-circuit silly cases. */
1419 if (lang_hooks.types_compatible_p (record_type, orig_type))
1422 tail_array_field = NULL_TREE;
1423 for (f = TYPE_FIELDS (record_type); f ; f = TREE_CHAIN (f))
1427 if (TREE_CODE (f) != FIELD_DECL)
1429 if (DECL_BIT_FIELD (f))
1432 field_offset = byte_position (f);
1433 if (TREE_CODE (field_offset) != INTEGER_CST)
1436 /* ??? Java creates "interesting" fields for representing base classes.
1437 They have no name, and have no context. With no context, we get into
1438 trouble with nonoverlapping_component_refs_p. Skip them. */
1439 if (!DECL_FIELD_CONTEXT (f))
1442 /* The previous array field isn't at the end. */
1443 tail_array_field = NULL_TREE;
1445 /* Check to see if this offset overlaps with the field. */
1446 cmp = tree_int_cst_compare (field_offset, offset);
1450 field_type = TREE_TYPE (f);
1452 /* Here we exactly match the offset being checked. If the types match,
1453 then we can return that field. */
1455 && lang_hooks.types_compatible_p (orig_type, field_type))
1458 base = build1 (INDIRECT_REF, record_type, base);
1459 t = build (COMPONENT_REF, field_type, base, f, NULL_TREE);
1463 /* Don't care about offsets into the middle of scalars. */
1464 if (!AGGREGATE_TYPE_P (field_type))
1467 /* Check for array at the end of the struct. This is often
1468 used as for flexible array members. We should be able to
1469 turn this into an array access anyway. */
1470 if (TREE_CODE (field_type) == ARRAY_TYPE)
1471 tail_array_field = f;
1473 /* Check the end of the field against the offset. */
1474 if (!DECL_SIZE_UNIT (f)
1475 || TREE_CODE (DECL_SIZE_UNIT (f)) != INTEGER_CST)
1477 t = int_const_binop (MINUS_EXPR, offset, field_offset, 1);
1478 if (!tree_int_cst_lt (t, DECL_SIZE_UNIT (f)))
1481 /* If we matched, then set offset to the displacement into
1487 if (!tail_array_field)
1490 f = tail_array_field;
1491 field_type = TREE_TYPE (f);
1492 offset = int_const_binop (MINUS_EXPR, offset, byte_position (f), 1);
1495 /* If we get here, we've got an aggregate field, and a possibly
1496 nonzero offset into them. Recurse and hope for a valid match. */
1498 base = build1 (INDIRECT_REF, record_type, base);
1499 base = build (COMPONENT_REF, field_type, base, f, NULL_TREE);
1501 t = maybe_fold_offset_to_array_ref (base, offset, orig_type);
1504 return maybe_fold_offset_to_component_ref (field_type, base, offset,
1509 /* A subroutine of fold_stmt_r. Attempt to simplify *(BASE+OFFSET).
1510 Return the simplified expression, or NULL if nothing could be done. */
1513 maybe_fold_stmt_indirect (tree expr, tree base, tree offset)
1517 /* We may well have constructed a double-nested PLUS_EXPR via multiple
1518 substitutions. Fold that down to one. Remove NON_LVALUE_EXPRs that
1519 are sometimes added. */
1522 TREE_OPERAND (expr, 0) = base;
1524 /* One possibility is that the address reduces to a string constant. */
1525 t = fold_read_from_constant_string (expr);
1529 /* Add in any offset from a PLUS_EXPR. */
1530 if (TREE_CODE (base) == PLUS_EXPR)
1534 offset2 = TREE_OPERAND (base, 1);
1535 if (TREE_CODE (offset2) != INTEGER_CST)
1537 base = TREE_OPERAND (base, 0);
1539 offset = int_const_binop (PLUS_EXPR, offset, offset2, 1);
1542 if (TREE_CODE (base) == ADDR_EXPR)
1544 /* Strip the ADDR_EXPR. */
1545 base = TREE_OPERAND (base, 0);
1547 /* Fold away CONST_DECL to its value, if the type is scalar. */
1548 if (TREE_CODE (base) == CONST_DECL
1549 && is_gimple_min_invariant (DECL_INITIAL (base)))
1550 return DECL_INITIAL (base);
1552 /* Try folding *(&B+O) to B[X]. */
1553 t = maybe_fold_offset_to_array_ref (base, offset, TREE_TYPE (expr));
1557 /* Try folding *(&B+O) to B.X. */
1558 t = maybe_fold_offset_to_component_ref (TREE_TYPE (base), base, offset,
1559 TREE_TYPE (expr), false);
1563 /* Fold *&B to B. We can only do this if EXPR is the same type
1564 as BASE. We can't do this if EXPR is the element type of an array
1565 and BASE is the array. */
1566 if (integer_zerop (offset)
1567 && lang_hooks.types_compatible_p (TREE_TYPE (base),
1573 /* We can get here for out-of-range string constant accesses,
1574 such as "_"[3]. Bail out of the entire substitution search
1575 and arrange for the entire statement to be replaced by a
1576 call to __builtin_trap. In all likelyhood this will all be
1577 constant-folded away, but in the meantime we can't leave with
1578 something that get_expr_operands can't understand. */
1582 if (TREE_CODE (t) == ADDR_EXPR
1583 && TREE_CODE (TREE_OPERAND (t, 0)) == STRING_CST)
1585 /* FIXME: Except that this causes problems elsewhere with dead
1586 code not being deleted, and we abort in the rtl expanders
1587 because we failed to remove some ssa_name. In the meantime,
1588 just return zero. */
1589 /* FIXME2: This condition should be signaled by
1590 fold_read_from_constant_string directly, rather than
1591 re-checking for it here. */
1592 return integer_zero_node;
1595 /* Try folding *(B+O) to B->X. Still an improvement. */
1596 if (POINTER_TYPE_P (TREE_TYPE (base)))
1598 t = maybe_fold_offset_to_component_ref (TREE_TYPE (TREE_TYPE (base)),
1600 TREE_TYPE (expr), true);
1606 /* Otherwise we had an offset that we could not simplify. */
1611 /* A subroutine of fold_stmt_r. EXPR is a PLUS_EXPR.
1613 A quaint feature extant in our address arithmetic is that there
1614 can be hidden type changes here. The type of the result need
1615 not be the same as the type of the input pointer.
1617 What we're after here is an expression of the form
1618 (T *)(&array + const)
1619 where the cast doesn't actually exist, but is implicit in the
1620 type of the PLUS_EXPR. We'd like to turn this into
1622 which may be able to propagate further. */
1625 maybe_fold_stmt_addition (tree expr)
1627 tree op0 = TREE_OPERAND (expr, 0);
1628 tree op1 = TREE_OPERAND (expr, 1);
1629 tree ptr_type = TREE_TYPE (expr);
1632 bool subtract = (TREE_CODE (expr) == MINUS_EXPR);
1634 /* We're only interested in pointer arithmetic. */
1635 if (!POINTER_TYPE_P (ptr_type))
1637 /* Canonicalize the integral operand to op1. */
1638 if (INTEGRAL_TYPE_P (TREE_TYPE (op0)))
1642 t = op0, op0 = op1, op1 = t;
1644 /* It had better be a constant. */
1645 if (TREE_CODE (op1) != INTEGER_CST)
1647 /* The first operand should be an ADDR_EXPR. */
1648 if (TREE_CODE (op0) != ADDR_EXPR)
1650 op0 = TREE_OPERAND (op0, 0);
1652 /* If the first operand is an ARRAY_REF, expand it so that we can fold
1653 the offset into it. */
1654 while (TREE_CODE (op0) == ARRAY_REF)
1656 tree array_obj = TREE_OPERAND (op0, 0);
1657 tree array_idx = TREE_OPERAND (op0, 1);
1658 tree elt_type = TREE_TYPE (op0);
1659 tree elt_size = TYPE_SIZE_UNIT (elt_type);
1662 if (TREE_CODE (array_idx) != INTEGER_CST)
1664 if (TREE_CODE (elt_size) != INTEGER_CST)
1667 /* Un-bias the index by the min index of the array type. */
1668 min_idx = TYPE_DOMAIN (TREE_TYPE (array_obj));
1671 min_idx = TYPE_MIN_VALUE (min_idx);
1674 if (TREE_CODE (min_idx) != INTEGER_CST)
1677 array_idx = convert (TREE_TYPE (min_idx), array_idx);
1678 if (!integer_zerop (min_idx))
1679 array_idx = int_const_binop (MINUS_EXPR, array_idx,
1684 /* Convert the index to a byte offset. */
1685 array_idx = convert (sizetype, array_idx);
1686 array_idx = int_const_binop (MULT_EXPR, array_idx, elt_size, 0);
1688 /* Update the operands for the next round, or for folding. */
1689 /* If we're manipulating unsigned types, then folding into negative
1690 values can produce incorrect results. Particularly if the type
1691 is smaller than the width of the pointer. */
1693 && TYPE_UNSIGNED (TREE_TYPE (op1))
1694 && tree_int_cst_lt (array_idx, op1))
1696 op1 = int_const_binop (subtract ? MINUS_EXPR : PLUS_EXPR,
1702 /* If we weren't able to fold the subtraction into another array reference,
1703 canonicalize the integer for passing to the array and component ref
1704 simplification functions. */
1707 if (TYPE_UNSIGNED (TREE_TYPE (op1)))
1709 op1 = fold (build1 (NEGATE_EXPR, TREE_TYPE (op1), op1));
1710 /* ??? In theory fold should always produce another integer. */
1711 if (TREE_CODE (op1) != INTEGER_CST)
1715 ptd_type = TREE_TYPE (ptr_type);
1717 /* At which point we can try some of the same things as for indirects. */
1718 t = maybe_fold_offset_to_array_ref (op0, op1, ptd_type);
1720 t = maybe_fold_offset_to_component_ref (TREE_TYPE (op0), op0, op1,
1723 t = build1 (ADDR_EXPR, ptr_type, t);
1729 /* Subroutine of fold_stmt called via walk_tree. We perform several
1730 simplifications of EXPR_P, mostly having to do with pointer arithmetic. */
1733 fold_stmt_r (tree *expr_p, int *walk_subtrees, void *data)
1735 bool *changed_p = data;
1736 tree expr = *expr_p, t;
1738 /* ??? It'd be nice if walk_tree had a pre-order option. */
1739 switch (TREE_CODE (expr))
1742 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1747 t = maybe_fold_stmt_indirect (expr, TREE_OPERAND (expr, 0),
1751 /* ??? Could handle ARRAY_REF here, as a variant of INDIRECT_REF.
1752 We'd only want to bother decomposing an existing ARRAY_REF if
1753 the base array is found to have another offset contained within.
1754 Otherwise we'd be wasting time. */
1757 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1762 /* Set TREE_INVARIANT properly so that the value is properly
1763 considered constant, and so gets propagated as expected. */
1765 recompute_tree_invarant_for_addr_expr (expr);
1770 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1773 t = walk_tree (&TREE_OPERAND (expr, 1), fold_stmt_r, data, NULL);
1778 t = maybe_fold_stmt_addition (expr);
1782 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1787 /* Make sure the FIELD_DECL is actually a field in the type on the lhs.
1788 We've already checked that the records are compatible, so we should
1789 come up with a set of compatible fields. */
1791 tree expr_record = TREE_TYPE (TREE_OPERAND (expr, 0));
1792 tree expr_field = TREE_OPERAND (expr, 1);
1794 if (DECL_FIELD_CONTEXT (expr_field) != TYPE_MAIN_VARIANT (expr_record))
1796 expr_field = find_compatible_field (expr_record, expr_field);
1797 TREE_OPERAND (expr, 1) = expr_field;
1816 /* Return the string length of ARG in LENGTH. If ARG is an SSA name variable,
1817 follow its use-def chains. If LENGTH is not NULL and its value is not
1818 equal to the length we determine, or if we are unable to determine the
1819 length, return false. VISITED is a bitmap of visited variables. */
1822 get_strlen (tree arg, tree *length, bitmap visited)
1824 tree var, def_stmt, val;
1826 if (TREE_CODE (arg) != SSA_NAME)
1828 val = c_strlen (arg, 1);
1832 if (*length && simple_cst_equal (val, *length) != 1)
1839 /* If we were already here, break the infinite cycle. */
1840 if (bitmap_bit_p (visited, SSA_NAME_VERSION (arg)))
1842 bitmap_set_bit (visited, SSA_NAME_VERSION (arg));
1845 def_stmt = SSA_NAME_DEF_STMT (var);
1847 switch (TREE_CODE (def_stmt))
1853 /* The RHS of the statement defining VAR must either have a
1854 constant length or come from another SSA_NAME with a constant
1856 rhs = TREE_OPERAND (def_stmt, 1);
1858 if (TREE_CODE (rhs) == SSA_NAME)
1859 return get_strlen (rhs, length, visited);
1861 /* See if the RHS is a constant length. */
1862 len = c_strlen (rhs, 1);
1865 if (*length && simple_cst_equal (len, *length) != 1)
1877 /* All the arguments of the PHI node must have the same constant
1881 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
1883 tree arg = PHI_ARG_DEF (def_stmt, i);
1885 /* If this PHI has itself as an argument, we cannot
1886 determine the string length of this argument. However,
1887 if we can find a constant string length for the other
1888 PHI args then we can still be sure that this is a
1889 constant string length. So be optimistic and just
1890 continue with the next argument. */
1891 if (arg == PHI_RESULT (def_stmt))
1894 if (!get_strlen (arg, length, visited))
1910 /* Fold builtin call FN in statement STMT. If it cannot be folded into a
1911 constant, return NULL_TREE. Otherwise, return its constant value. */
1914 ccp_fold_builtin (tree stmt, tree fn)
1916 tree result, strlen_val[2];
1917 tree callee, arglist, a;
1922 ignore = TREE_CODE (stmt) != MODIFY_EXPR;
1924 /* First try the generic builtin folder. If that succeeds, return the
1926 result = fold_builtin (fn, ignore);
1930 STRIP_NOPS (result);
1934 /* Ignore MD builtins. */
1935 callee = get_callee_fndecl (fn);
1936 if (DECL_BUILT_IN_CLASS (callee) == BUILT_IN_MD)
1939 /* If the builtin could not be folded, and it has no argument list,
1941 arglist = TREE_OPERAND (fn, 1);
1945 /* Limit the work only for builtins we know how to simplify. */
1946 switch (DECL_FUNCTION_CODE (callee))
1948 case BUILT_IN_STRLEN:
1949 case BUILT_IN_FPUTS:
1950 case BUILT_IN_FPUTS_UNLOCKED:
1953 case BUILT_IN_STRCPY:
1954 case BUILT_IN_STRNCPY:
1961 /* Try to use the dataflow information gathered by the CCP process. */
1962 visited = BITMAP_ALLOC (NULL);
1964 memset (strlen_val, 0, sizeof (strlen_val));
1965 for (i = 0, a = arglist;
1967 i++, strlen_arg >>= 1, a = TREE_CHAIN (a))
1970 bitmap_clear (visited);
1971 if (!get_strlen (TREE_VALUE (a), &strlen_val[i], visited))
1972 strlen_val[i] = NULL_TREE;
1975 BITMAP_FREE (visited);
1978 switch (DECL_FUNCTION_CODE (callee))
1980 case BUILT_IN_STRLEN:
1983 tree new = fold_convert (TREE_TYPE (fn), strlen_val[0]);
1985 /* If the result is not a valid gimple value, or not a cast
1986 of a valid gimple value, then we can not use the result. */
1987 if (is_gimple_val (new)
1988 || (is_gimple_cast (new)
1989 && is_gimple_val (TREE_OPERAND (new, 0))))
1994 case BUILT_IN_STRCPY:
1995 if (strlen_val[1] && is_gimple_val (strlen_val[1]))
1996 result = fold_builtin_strcpy (fn, strlen_val[1]);
1999 case BUILT_IN_STRNCPY:
2000 if (strlen_val[1] && is_gimple_val (strlen_val[1]))
2001 result = fold_builtin_strncpy (fn, strlen_val[1]);
2004 case BUILT_IN_FPUTS:
2005 result = fold_builtin_fputs (arglist,
2006 TREE_CODE (stmt) != MODIFY_EXPR, 0,
2010 case BUILT_IN_FPUTS_UNLOCKED:
2011 result = fold_builtin_fputs (arglist,
2012 TREE_CODE (stmt) != MODIFY_EXPR, 1,
2020 if (result && ignore)
2021 result = fold_ignored_result (result);
2026 /* Fold the statement pointed by STMT_P. In some cases, this function may
2027 replace the whole statement with a new one. Returns true iff folding
2028 makes any changes. */
2031 fold_stmt (tree *stmt_p)
2033 tree rhs, result, stmt;
2034 bool changed = false;
2038 /* If we replaced constants and the statement makes pointer dereferences,
2039 then we may need to fold instances of *&VAR into VAR, etc. */
2040 if (walk_tree (stmt_p, fold_stmt_r, &changed, NULL))
2043 = build_function_call_expr (implicit_built_in_decls[BUILT_IN_TRAP],
2048 rhs = get_rhs (stmt);
2053 if (TREE_CODE (rhs) == CALL_EXPR)
2057 /* Check for builtins that CCP can handle using information not
2058 available in the generic fold routines. */
2059 callee = get_callee_fndecl (rhs);
2060 if (callee && DECL_BUILT_IN (callee))
2061 result = ccp_fold_builtin (stmt, rhs);
2064 /* Check for resolvable OBJ_TYPE_REF. The only sorts we can resolve
2065 here are when we've propagated the address of a decl into the
2067 /* ??? Should perhaps do this in fold proper. However, doing it
2068 there requires that we create a new CALL_EXPR, and that requires
2069 copying EH region info to the new node. Easier to just do it
2070 here where we can just smash the call operand. */
2071 callee = TREE_OPERAND (rhs, 0);
2072 if (TREE_CODE (callee) == OBJ_TYPE_REF
2073 && lang_hooks.fold_obj_type_ref
2074 && TREE_CODE (OBJ_TYPE_REF_OBJECT (callee)) == ADDR_EXPR
2075 && DECL_P (TREE_OPERAND
2076 (OBJ_TYPE_REF_OBJECT (callee), 0)))
2080 /* ??? Caution: Broken ADDR_EXPR semantics means that
2081 looking at the type of the operand of the addr_expr
2082 can yield an array type. See silly exception in
2083 check_pointer_types_r. */
2085 t = TREE_TYPE (TREE_TYPE (OBJ_TYPE_REF_OBJECT (callee)));
2086 t = lang_hooks.fold_obj_type_ref (callee, t);
2089 TREE_OPERAND (rhs, 0) = t;
2096 /* If we couldn't fold the RHS, hand over to the generic fold routines. */
2097 if (result == NULL_TREE)
2098 result = fold (rhs);
2100 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
2101 may have been added by fold, and "useless" type conversions that might
2102 now be apparent due to propagation. */
2103 STRIP_USELESS_TYPE_CONVERSION (result);
2106 changed |= set_rhs (stmt_p, result);
2112 /* Convert EXPR into a GIMPLE value suitable for substitution on the
2113 RHS of an assignment. Insert the necessary statements before
2117 convert_to_gimple_builtin (block_stmt_iterator *si_p, tree expr)
2119 tree_stmt_iterator ti;
2120 tree stmt = bsi_stmt (*si_p);
2121 tree tmp, stmts = NULL;
2123 push_gimplify_context ();
2124 tmp = get_initialized_tmp_var (expr, &stmts, NULL);
2125 pop_gimplify_context (NULL);
2127 /* The replacement can expose previously unreferenced variables. */
2128 for (ti = tsi_start (stmts); !tsi_end_p (ti); tsi_next (&ti))
2130 find_new_referenced_vars (tsi_stmt_ptr (ti));
2131 mark_new_vars_to_rename (tsi_stmt (ti), vars_to_rename);
2134 if (EXPR_HAS_LOCATION (stmt))
2135 annotate_all_with_locus (&stmts, EXPR_LOCATION (stmt));
2137 bsi_insert_before (si_p, stmts, BSI_SAME_STMT);
2143 /* A simple pass that attempts to fold all builtin functions. This pass
2144 is run after we've propagated as many constants as we can. */
2147 execute_fold_all_builtins (void)
2149 bool cfg_changed = false;
2153 block_stmt_iterator i;
2154 for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
2156 tree *stmtp = bsi_stmt_ptr (i);
2157 tree call = get_rhs (*stmtp);
2158 tree callee, result;
2160 if (!call || TREE_CODE (call) != CALL_EXPR)
2162 callee = get_callee_fndecl (call);
2163 if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)
2166 result = ccp_fold_builtin (*stmtp, call);
2168 switch (DECL_FUNCTION_CODE (callee))
2170 case BUILT_IN_CONSTANT_P:
2171 /* Resolve __builtin_constant_p. If it hasn't been
2172 folded to integer_one_node by now, it's fairly
2173 certain that the value simply isn't constant. */
2174 result = integer_zero_node;
2181 if (dump_file && (dump_flags & TDF_DETAILS))
2183 fprintf (dump_file, "Simplified\n ");
2184 print_generic_stmt (dump_file, *stmtp, dump_flags);
2187 if (!set_rhs (stmtp, result))
2189 result = convert_to_gimple_builtin (&i, result);
2190 if (result && !set_rhs (stmtp, result))
2193 modify_stmt (*stmtp);
2194 if (maybe_clean_eh_stmt (*stmtp)
2195 && tree_purge_dead_eh_edges (bb))
2198 if (dump_file && (dump_flags & TDF_DETAILS))
2200 fprintf (dump_file, "to\n ");
2201 print_generic_stmt (dump_file, *stmtp, dump_flags);
2202 fprintf (dump_file, "\n");
2207 /* Delete unreachable blocks. */
2209 cleanup_tree_cfg ();
2213 struct tree_opt_pass pass_fold_builtins =
2217 execute_fold_all_builtins, /* execute */
2220 0, /* static_pass_number */
2222 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
2223 0, /* properties_provided */
2224 0, /* properties_destroyed */
2225 0, /* todo_flags_start */
2228 | TODO_rename_vars, /* todo_flags_finish */