1 /* Conditional constant propagation pass for the GNU compiler.
2 Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
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, 51 Franklin Street, Fifth Floor, Boston, MA
24 /* Conditional constant propagation (CCP) is based on the SSA
25 propagation engine (tree-ssa-propagate.c). Constant assignments of
26 the form VAR = CST are propagated from the assignments into uses of
27 VAR, which in turn may generate new constants. The simulation uses
28 a four level lattice to keep track of constant values associated
29 with SSA names. Given an SSA name V_i, it may take one of the
32 UNINITIALIZED -> the initial state of the value. This value
33 is replaced with a correct initial value
34 the first time the value is used, so the
35 rest of the pass does not need to care about
36 it. Using this value simplifies initialization
37 of the pass, and prevents us from needlessly
38 scanning statements that are never reached.
40 UNDEFINED -> V_i is a local variable whose definition
41 has not been processed yet. Therefore we
42 don't yet know if its value is a constant
45 CONSTANT -> V_i has been found to hold a constant
48 VARYING -> V_i cannot take a constant value, or if it
49 does, it is not possible to determine it
52 The core of SSA-CCP is in ccp_visit_stmt and ccp_visit_phi_node:
54 1- In ccp_visit_stmt, we are interested in assignments whose RHS
55 evaluates into a constant and conditional jumps whose predicate
56 evaluates into a boolean true or false. When an assignment of
57 the form V_i = CONST is found, V_i's lattice value is set to
58 CONSTANT and CONST is associated with it. This causes the
59 propagation engine to add all the SSA edges coming out the
60 assignment into the worklists, so that statements that use V_i
63 If the statement is a conditional with a constant predicate, we
64 mark the outgoing edges as executable or not executable
65 depending on the predicate's value. This is then used when
66 visiting PHI nodes to know when a PHI argument can be ignored.
69 2- In ccp_visit_phi_node, if all the PHI arguments evaluate to the
70 same constant C, then the LHS of the PHI is set to C. This
71 evaluation is known as the "meet operation". Since one of the
72 goals of this evaluation is to optimistically return constant
73 values as often as possible, it uses two main short cuts:
75 - If an argument is flowing in through a non-executable edge, it
76 is ignored. This is useful in cases like this:
82 a_11 = PHI (a_9, a_10)
84 If PRED is known to always evaluate to false, then we can
85 assume that a_11 will always take its value from a_10, meaning
86 that instead of consider it VARYING (a_9 and a_10 have
87 different values), we can consider it CONSTANT 100.
89 - If an argument has an UNDEFINED value, then it does not affect
90 the outcome of the meet operation. If a variable V_i has an
91 UNDEFINED value, it means that either its defining statement
92 hasn't been visited yet or V_i has no defining statement, in
93 which case the original symbol 'V' is being used
94 uninitialized. Since 'V' is a local variable, the compiler
95 may assume any initial value for it.
98 After propagation, every variable V_i that ends up with a lattice
99 value of CONSTANT will have the associated constant value in the
100 array CONST_VAL[i].VALUE. That is fed into substitute_and_fold for
101 final substitution and folding.
104 Constant propagation in stores and loads (STORE-CCP)
105 ----------------------------------------------------
107 While CCP has all the logic to propagate constants in GIMPLE
108 registers, it is missing the ability to associate constants with
109 stores and loads (i.e., pointer dereferences, structures and
110 global/aliased variables). We don't keep loads and stores in
111 SSA, but we do build a factored use-def web for them (in the
114 For instance, consider the following code fragment:
133 We should be able to deduce that the predicate 'a.a != B' is always
134 false. To achieve this, we associate constant values to the SSA
135 names in the VDEF operands for each store. Additionally,
136 since we also glob partial loads/stores with the base symbol, we
137 also keep track of the memory reference where the constant value
138 was stored (in the MEM_REF field of PROP_VALUE_T). For instance,
146 In the example above, CCP will associate value '2' with 'a_5', but
147 it would be wrong to replace the load from 'a.b' with '2', because
148 '2' had been stored into a.a.
150 Note that the initial value of virtual operands is VARYING, not
151 UNDEFINED. Consider, for instance global variables:
159 # A_5 = PHI (A_4, A_2);
167 The value of A_2 cannot be assumed to be UNDEFINED, as it may have
168 been defined outside of foo. If we were to assume it UNDEFINED, we
169 would erroneously optimize the above into 'return 3;'.
171 Though STORE-CCP is not too expensive, it does have to do more work
172 than regular CCP, so it is only enabled at -O2. Both regular CCP
173 and STORE-CCP use the exact same algorithm. The only distinction
174 is that when doing STORE-CCP, the boolean variable DO_STORE_CCP is
175 set to true. This affects the evaluation of statements and PHI
180 Constant propagation with conditional branches,
181 Wegman and Zadeck, ACM TOPLAS 13(2):181-210.
183 Building an Optimizing Compiler,
184 Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9.
186 Advanced Compiler Design and Implementation,
187 Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */
191 #include "coretypes.h"
198 #include "basic-block.h"
201 #include "function.h"
202 #include "diagnostic.h"
204 #include "tree-dump.h"
205 #include "tree-flow.h"
206 #include "tree-pass.h"
207 #include "tree-ssa-propagate.h"
208 #include "langhooks.h"
213 /* Possible lattice values. */
222 /* Array of propagated constant values. After propagation,
223 CONST_VAL[I].VALUE holds the constant value for SSA_NAME(I). If
224 the constant is held in an SSA name representing a memory store
225 (i.e., a VDEF), CONST_VAL[I].MEM_REF will contain the actual
226 memory reference used to store (i.e., the LHS of the assignment
228 static prop_value_t *const_val;
230 /* True if we are also propagating constants in stores and loads. */
231 static bool do_store_ccp;
233 /* Dump constant propagation value VAL to file OUTF prefixed by PREFIX. */
236 dump_lattice_value (FILE *outf, const char *prefix, prop_value_t val)
238 switch (val.lattice_val)
241 fprintf (outf, "%sUNINITIALIZED", prefix);
244 fprintf (outf, "%sUNDEFINED", prefix);
247 fprintf (outf, "%sVARYING", prefix);
250 fprintf (outf, "%sCONSTANT ", prefix);
251 print_generic_expr (outf, val.value, dump_flags);
259 /* Print lattice value VAL to stderr. */
261 void debug_lattice_value (prop_value_t val);
264 debug_lattice_value (prop_value_t val)
266 dump_lattice_value (stderr, "", val);
267 fprintf (stderr, "\n");
271 /* The regular is_gimple_min_invariant does a shallow test of the object.
272 It assumes that full gimplification has happened, or will happen on the
273 object. For a value coming from DECL_INITIAL, this is not true, so we
274 have to be more strict ourselves. */
277 ccp_decl_initial_min_invariant (tree t)
279 if (!is_gimple_min_invariant (t))
281 if (TREE_CODE (t) == ADDR_EXPR)
283 /* Inline and unroll is_gimple_addressable. */
286 t = TREE_OPERAND (t, 0);
287 if (is_gimple_id (t))
289 if (!handled_component_p (t))
296 /* If SYM is a constant variable with known value, return the value.
297 NULL_TREE is returned otherwise. */
300 get_symbol_constant_value (tree sym)
302 if (TREE_STATIC (sym)
303 && TREE_READONLY (sym)
306 tree val = DECL_INITIAL (sym);
308 && ccp_decl_initial_min_invariant (val))
315 /* Compute a default value for variable VAR and store it in the
316 CONST_VAL array. The following rules are used to get default
319 1- Global and static variables that are declared constant are
322 2- Any other value is considered UNDEFINED. This is useful when
323 considering PHI nodes. PHI arguments that are undefined do not
324 change the constant value of the PHI node, which allows for more
325 constants to be propagated.
327 3- If SSA_NAME_VALUE is set and it is a constant, its value is
330 4- Variables defined by statements other than assignments and PHI
331 nodes are considered VARYING.
333 5- Initial values of variables that are not GIMPLE registers are
334 considered VARYING. */
337 get_default_value (tree var)
339 tree sym = SSA_NAME_VAR (var);
340 prop_value_t val = { UNINITIALIZED, NULL_TREE, NULL_TREE };
343 if (!do_store_ccp && !is_gimple_reg (var))
345 /* Short circuit for regular CCP. We are not interested in any
346 non-register when DO_STORE_CCP is false. */
347 val.lattice_val = VARYING;
349 else if (SSA_NAME_VALUE (var)
350 && is_gimple_min_invariant (SSA_NAME_VALUE (var)))
352 val.lattice_val = CONSTANT;
353 val.value = SSA_NAME_VALUE (var);
355 else if ((cst_val = get_symbol_constant_value (sym)) != NULL_TREE)
357 /* Globals and static variables declared 'const' take their
359 val.lattice_val = CONSTANT;
365 tree stmt = SSA_NAME_DEF_STMT (var);
367 if (IS_EMPTY_STMT (stmt))
369 /* Variables defined by an empty statement are those used
370 before being initialized. If VAR is a local variable, we
371 can assume initially that it is UNDEFINED, otherwise we must
372 consider it VARYING. */
373 if (is_gimple_reg (sym) && TREE_CODE (sym) != PARM_DECL)
374 val.lattice_val = UNDEFINED;
376 val.lattice_val = VARYING;
378 else if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
379 || TREE_CODE (stmt) == PHI_NODE)
381 /* Any other variable defined by an assignment or a PHI node
382 is considered UNDEFINED. */
383 val.lattice_val = UNDEFINED;
387 /* Otherwise, VAR will never take on a constant value. */
388 val.lattice_val = VARYING;
396 /* Get the constant value associated with variable VAR. */
398 static inline prop_value_t *
401 prop_value_t *val = &const_val[SSA_NAME_VERSION (var)];
403 if (val->lattice_val == UNINITIALIZED)
404 *val = get_default_value (var);
409 /* Sets the value associated with VAR to VARYING. */
412 set_value_varying (tree var)
414 prop_value_t *val = &const_val[SSA_NAME_VERSION (var)];
416 val->lattice_val = VARYING;
417 val->value = NULL_TREE;
418 val->mem_ref = NULL_TREE;
421 /* For float types, modify the value of VAL to make ccp work correctly
422 for non-standard values (-0, NaN):
424 If HONOR_SIGNED_ZEROS is false, and VAL = -0, we canonicalize it to 0.
425 If HONOR_NANS is false, and VAL is NaN, we canonicalize it to UNDEFINED.
426 This is to fix the following problem (see PR 29921): Suppose we have
430 and we set value of y to NaN. This causes value of x to be set to NaN.
431 When we later determine that y is in fact VARYING, fold uses the fact
432 that HONOR_NANS is false, and we try to change the value of x to 0,
433 causing an ICE. With HONOR_NANS being false, the real appearance of
434 NaN would cause undefined behavior, though, so claiming that y (and x)
435 are UNDEFINED initially is correct. */
438 canonicalize_float_value (prop_value_t *val)
440 enum machine_mode mode;
444 if (val->lattice_val != CONSTANT
445 || TREE_CODE (val->value) != REAL_CST)
448 d = TREE_REAL_CST (val->value);
449 type = TREE_TYPE (val->value);
450 mode = TYPE_MODE (type);
452 if (!HONOR_SIGNED_ZEROS (mode)
453 && REAL_VALUE_MINUS_ZERO (d))
455 val->value = build_real (type, dconst0);
459 if (!HONOR_NANS (mode)
460 && REAL_VALUE_ISNAN (d))
462 val->lattice_val = UNDEFINED;
469 /* Set the value for variable VAR to NEW_VAL. Return true if the new
470 value is different from VAR's previous value. */
473 set_lattice_value (tree var, prop_value_t new_val)
475 prop_value_t *old_val = get_value (var);
477 canonicalize_float_value (&new_val);
479 /* Lattice transitions must always be monotonically increasing in
480 value. If *OLD_VAL and NEW_VAL are the same, return false to
481 inform the caller that this was a non-transition. */
483 gcc_assert (old_val->lattice_val < new_val.lattice_val
484 || (old_val->lattice_val == new_val.lattice_val
485 && ((!old_val->value && !new_val.value)
486 || operand_equal_p (old_val->value, new_val.value, 0))
487 && old_val->mem_ref == new_val.mem_ref));
489 if (old_val->lattice_val != new_val.lattice_val)
491 if (dump_file && (dump_flags & TDF_DETAILS))
493 dump_lattice_value (dump_file, "Lattice value changed to ", new_val);
494 fprintf (dump_file, ". Adding SSA edges to worklist.\n");
499 gcc_assert (new_val.lattice_val != UNDEFINED);
507 /* Return the likely CCP lattice value for STMT.
509 If STMT has no operands, then return CONSTANT.
511 Else if any operands of STMT are undefined, then return UNDEFINED.
513 Else if any operands of STMT are constants, then return CONSTANT.
515 Else return VARYING. */
518 likely_value (tree stmt)
520 bool has_constant_operand;
525 ann = stmt_ann (stmt);
527 /* If the statement has volatile operands, it won't fold to a
529 if (ann->has_volatile_ops)
532 /* If we are not doing store-ccp, statements with loads
533 and/or stores will never fold into a constant. */
535 && !ZERO_SSA_OPERANDS (stmt, SSA_OP_ALL_VIRTUALS))
539 /* A CALL_EXPR is assumed to be varying. NOTE: This may be overly
540 conservative, in the presence of const and pure calls. */
541 if (get_call_expr_in (stmt) != NULL_TREE)
544 /* Anything other than assignments and conditional jumps are not
545 interesting for CCP. */
546 if (TREE_CODE (stmt) != GIMPLE_MODIFY_STMT
547 && !(TREE_CODE (stmt) == RETURN_EXPR && get_rhs (stmt) != NULL_TREE)
548 && TREE_CODE (stmt) != COND_EXPR
549 && TREE_CODE (stmt) != SWITCH_EXPR)
552 if (is_gimple_min_invariant (get_rhs (stmt)))
555 has_constant_operand = false;
556 FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE | SSA_OP_VUSE)
558 prop_value_t *val = get_value (use);
560 if (val->lattice_val == UNDEFINED)
563 if (val->lattice_val == CONSTANT)
564 has_constant_operand = true;
567 if (has_constant_operand
568 /* We do not consider virtual operands here -- load from read-only
569 memory may have only VARYING virtual operands, but still be
571 || ZERO_SSA_OPERANDS (stmt, SSA_OP_USE))
577 /* Returns true if STMT cannot be constant. */
580 surely_varying_stmt_p (tree stmt)
582 /* If the statement has operands that we cannot handle, it cannot be
584 if (stmt_ann (stmt)->has_volatile_ops)
587 if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_ALL_VIRTUALS))
592 /* We can only handle simple loads and stores. */
593 if (!stmt_makes_single_load (stmt)
594 && !stmt_makes_single_store (stmt))
598 /* If it contains a call, it is varying. */
599 if (get_call_expr_in (stmt) != NULL_TREE)
602 /* Anything other than assignments and conditional jumps are not
603 interesting for CCP. */
604 if (TREE_CODE (stmt) != GIMPLE_MODIFY_STMT
605 && !(TREE_CODE (stmt) == RETURN_EXPR && get_rhs (stmt) != NULL_TREE)
606 && TREE_CODE (stmt) != COND_EXPR
607 && TREE_CODE (stmt) != SWITCH_EXPR)
613 /* Initialize local data structures for CCP. */
616 ccp_initialize (void)
620 const_val = XCNEWVEC (prop_value_t, num_ssa_names);
622 /* Initialize simulation flags for PHI nodes and statements. */
625 block_stmt_iterator i;
627 for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
629 tree stmt = bsi_stmt (i);
630 bool is_varying = surely_varying_stmt_p (stmt);
637 /* If the statement will not produce a constant, mark
638 all its outputs VARYING. */
639 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
642 set_value_varying (def);
646 DONT_SIMULATE_AGAIN (stmt) = is_varying;
650 /* Now process PHI nodes. We never set DONT_SIMULATE_AGAIN on phi node,
651 since we do not know which edges are executable yet, except for
652 phi nodes for virtual operands when we do not do store ccp. */
657 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
659 if (!do_store_ccp && !is_gimple_reg (PHI_RESULT (phi)))
660 DONT_SIMULATE_AGAIN (phi) = true;
662 DONT_SIMULATE_AGAIN (phi) = false;
668 /* Do final substitution of propagated values, cleanup the flowgraph and
669 free allocated storage.
671 Return TRUE when something was optimized. */
676 /* Perform substitutions based on the known constant values. */
677 bool something_changed = substitute_and_fold (const_val, false);
680 return something_changed;;
684 /* Compute the meet operator between *VAL1 and *VAL2. Store the result
687 any M UNDEFINED = any
688 any M VARYING = VARYING
689 Ci M Cj = Ci if (i == j)
690 Ci M Cj = VARYING if (i != j)
694 ccp_lattice_meet (prop_value_t *val1, prop_value_t *val2)
696 if (val1->lattice_val == UNDEFINED)
698 /* UNDEFINED M any = any */
701 else if (val2->lattice_val == UNDEFINED)
703 /* any M UNDEFINED = any
704 Nothing to do. VAL1 already contains the value we want. */
707 else if (val1->lattice_val == VARYING
708 || val2->lattice_val == VARYING)
710 /* any M VARYING = VARYING. */
711 val1->lattice_val = VARYING;
712 val1->value = NULL_TREE;
713 val1->mem_ref = NULL_TREE;
715 else if (val1->lattice_val == CONSTANT
716 && val2->lattice_val == CONSTANT
717 && simple_cst_equal (val1->value, val2->value) == 1
719 || (val1->mem_ref && val2->mem_ref
720 && operand_equal_p (val1->mem_ref, val2->mem_ref, 0))))
722 /* Ci M Cj = Ci if (i == j)
723 Ci M Cj = VARYING if (i != j)
725 If these two values come from memory stores, make sure that
726 they come from the same memory reference. */
727 val1->lattice_val = CONSTANT;
728 val1->value = val1->value;
729 val1->mem_ref = val1->mem_ref;
733 /* Any other combination is VARYING. */
734 val1->lattice_val = VARYING;
735 val1->value = NULL_TREE;
736 val1->mem_ref = NULL_TREE;
741 /* Loop through the PHI_NODE's parameters for BLOCK and compare their
742 lattice values to determine PHI_NODE's lattice value. The value of a
743 PHI node is determined calling ccp_lattice_meet with all the arguments
744 of the PHI node that are incoming via executable edges. */
746 static enum ssa_prop_result
747 ccp_visit_phi_node (tree phi)
750 prop_value_t *old_val, new_val;
752 if (dump_file && (dump_flags & TDF_DETAILS))
754 fprintf (dump_file, "\nVisiting PHI node: ");
755 print_generic_expr (dump_file, phi, dump_flags);
758 old_val = get_value (PHI_RESULT (phi));
759 switch (old_val->lattice_val)
762 return SSA_PROP_VARYING;
769 new_val.lattice_val = UNDEFINED;
770 new_val.value = NULL_TREE;
771 new_val.mem_ref = NULL_TREE;
778 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
780 /* Compute the meet operator over all the PHI arguments flowing
781 through executable edges. */
782 edge e = PHI_ARG_EDGE (phi, i);
784 if (dump_file && (dump_flags & TDF_DETAILS))
787 "\n Argument #%d (%d -> %d %sexecutable)\n",
788 i, e->src->index, e->dest->index,
789 (e->flags & EDGE_EXECUTABLE) ? "" : "not ");
792 /* If the incoming edge is executable, Compute the meet operator for
793 the existing value of the PHI node and the current PHI argument. */
794 if (e->flags & EDGE_EXECUTABLE)
796 tree arg = PHI_ARG_DEF (phi, i);
797 prop_value_t arg_val;
799 if (is_gimple_min_invariant (arg))
801 arg_val.lattice_val = CONSTANT;
803 arg_val.mem_ref = NULL_TREE;
806 arg_val = *(get_value (arg));
808 ccp_lattice_meet (&new_val, &arg_val);
810 if (dump_file && (dump_flags & TDF_DETAILS))
812 fprintf (dump_file, "\t");
813 print_generic_expr (dump_file, arg, dump_flags);
814 dump_lattice_value (dump_file, "\tValue: ", arg_val);
815 fprintf (dump_file, "\n");
818 if (new_val.lattice_val == VARYING)
823 if (dump_file && (dump_flags & TDF_DETAILS))
825 dump_lattice_value (dump_file, "\n PHI node value: ", new_val);
826 fprintf (dump_file, "\n\n");
829 /* Make the transition to the new value. */
830 if (set_lattice_value (PHI_RESULT (phi), new_val))
832 if (new_val.lattice_val == VARYING)
833 return SSA_PROP_VARYING;
835 return SSA_PROP_INTERESTING;
838 return SSA_PROP_NOT_INTERESTING;
842 /* CCP specific front-end to the non-destructive constant folding
845 Attempt to simplify the RHS of STMT knowing that one or more
846 operands are constants.
848 If simplification is possible, return the simplified RHS,
849 otherwise return the original RHS. */
854 tree rhs = get_rhs (stmt);
855 enum tree_code code = TREE_CODE (rhs);
856 enum tree_code_class kind = TREE_CODE_CLASS (code);
857 tree retval = NULL_TREE;
859 if (TREE_CODE (rhs) == SSA_NAME)
861 /* If the RHS is an SSA_NAME, return its known constant value,
863 return get_value (rhs)->value;
865 else if (do_store_ccp && stmt_makes_single_load (stmt))
867 /* If the RHS is a memory load, see if the VUSEs associated with
868 it are a valid constant for that memory load. */
869 prop_value_t *val = get_value_loaded_by (stmt, const_val);
870 if (val && val->mem_ref)
872 if (operand_equal_p (val->mem_ref, rhs, 0))
875 /* If RHS is extracting REALPART_EXPR or IMAGPART_EXPR of a
876 complex type with a known constant value, return it. */
877 if ((TREE_CODE (rhs) == REALPART_EXPR
878 || TREE_CODE (rhs) == IMAGPART_EXPR)
879 && operand_equal_p (val->mem_ref, TREE_OPERAND (rhs, 0), 0))
880 return fold_build1 (TREE_CODE (rhs), TREE_TYPE (rhs), val->value);
885 /* Unary operators. Note that we know the single operand must
886 be a constant. So this should almost always return a
888 if (kind == tcc_unary)
890 /* Handle unary operators which can appear in GIMPLE form. */
891 tree op0 = TREE_OPERAND (rhs, 0);
893 /* Simplify the operand down to a constant. */
894 if (TREE_CODE (op0) == SSA_NAME)
896 prop_value_t *val = get_value (op0);
897 if (val->lattice_val == CONSTANT)
898 op0 = get_value (op0)->value;
901 if ((code == NOP_EXPR || code == CONVERT_EXPR)
902 && useless_type_conversion_p (TREE_TYPE (rhs), TREE_TYPE (op0)))
904 return fold_unary (code, TREE_TYPE (rhs), op0);
907 /* Binary and comparison operators. We know one or both of the
908 operands are constants. */
909 else if (kind == tcc_binary
910 || kind == tcc_comparison
911 || code == TRUTH_AND_EXPR
912 || code == TRUTH_OR_EXPR
913 || code == TRUTH_XOR_EXPR)
915 /* Handle binary and comparison operators that can appear in
917 tree op0 = TREE_OPERAND (rhs, 0);
918 tree op1 = TREE_OPERAND (rhs, 1);
920 /* Simplify the operands down to constants when appropriate. */
921 if (TREE_CODE (op0) == SSA_NAME)
923 prop_value_t *val = get_value (op0);
924 if (val->lattice_val == CONSTANT)
928 if (TREE_CODE (op1) == SSA_NAME)
930 prop_value_t *val = get_value (op1);
931 if (val->lattice_val == CONSTANT)
935 return fold_binary (code, TREE_TYPE (rhs), op0, op1);
938 /* We may be able to fold away calls to builtin functions if their
939 arguments are constants. */
940 else if (code == CALL_EXPR
941 && TREE_CODE (CALL_EXPR_FN (rhs)) == ADDR_EXPR
942 && TREE_CODE (TREE_OPERAND (CALL_EXPR_FN (rhs), 0)) == FUNCTION_DECL
943 && DECL_BUILT_IN (TREE_OPERAND (CALL_EXPR_FN (rhs), 0)))
945 if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_USE))
952 /* Preserve the original values of every operand. */
953 orig = XNEWVEC (tree, NUM_SSA_OPERANDS (stmt, SSA_OP_USE));
954 FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_USE)
957 /* Substitute operands with their values and try to fold. */
958 replace_uses_in (stmt, NULL, const_val);
959 retval = fold_call_expr (rhs, false);
961 /* Restore operands to their original form. */
963 FOR_EACH_SSA_USE_OPERAND (var_p, stmt, iter, SSA_OP_USE)
964 SET_USE (var_p, orig[i++]);
971 /* If we got a simplified form, see if we need to convert its type. */
973 return fold_convert (TREE_TYPE (rhs), retval);
975 /* No simplification was possible. */
980 /* Return the tree representing the element referenced by T if T is an
981 ARRAY_REF or COMPONENT_REF into constant aggregates. Return
982 NULL_TREE otherwise. */
985 fold_const_aggregate_ref (tree t)
988 tree base, ctor, idx, field;
989 unsigned HOST_WIDE_INT cnt;
992 switch (TREE_CODE (t))
995 /* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its
996 DECL_INITIAL. If BASE is a nested reference into another
997 ARRAY_REF or COMPONENT_REF, make a recursive call to resolve
998 the inner reference. */
999 base = TREE_OPERAND (t, 0);
1000 switch (TREE_CODE (base))
1003 if (!TREE_READONLY (base)
1004 || TREE_CODE (TREE_TYPE (base)) != ARRAY_TYPE
1005 || !targetm.binds_local_p (base))
1008 ctor = DECL_INITIAL (base);
1013 ctor = fold_const_aggregate_ref (base);
1020 if (ctor == NULL_TREE
1021 || (TREE_CODE (ctor) != CONSTRUCTOR
1022 && TREE_CODE (ctor) != STRING_CST)
1023 || !TREE_STATIC (ctor))
1026 /* Get the index. If we have an SSA_NAME, try to resolve it
1027 with the current lattice value for the SSA_NAME. */
1028 idx = TREE_OPERAND (t, 1);
1029 switch (TREE_CODE (idx))
1032 if ((value = get_value (idx))
1033 && value->lattice_val == CONSTANT
1034 && TREE_CODE (value->value) == INTEGER_CST)
1047 /* Fold read from constant string. */
1048 if (TREE_CODE (ctor) == STRING_CST)
1050 if ((TYPE_MODE (TREE_TYPE (t))
1051 == TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor))))
1052 && (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor))))
1054 && GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor)))) == 1
1055 && compare_tree_int (idx, TREE_STRING_LENGTH (ctor)) < 0)
1056 return build_int_cst (TREE_TYPE (t), (TREE_STRING_POINTER (ctor)
1057 [TREE_INT_CST_LOW (idx)]));
1061 /* Whoo-hoo! I'll fold ya baby. Yeah! */
1062 FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval)
1063 if (tree_int_cst_equal (cfield, idx))
1068 /* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its
1069 DECL_INITIAL. If BASE is a nested reference into another
1070 ARRAY_REF or COMPONENT_REF, make a recursive call to resolve
1071 the inner reference. */
1072 base = TREE_OPERAND (t, 0);
1073 switch (TREE_CODE (base))
1076 if (!TREE_READONLY (base)
1077 || TREE_CODE (TREE_TYPE (base)) != RECORD_TYPE
1078 || !targetm.binds_local_p (base))
1081 ctor = DECL_INITIAL (base);
1086 ctor = fold_const_aggregate_ref (base);
1093 if (ctor == NULL_TREE
1094 || TREE_CODE (ctor) != CONSTRUCTOR
1095 || !TREE_STATIC (ctor))
1098 field = TREE_OPERAND (t, 1);
1100 FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval)
1102 /* FIXME: Handle bit-fields. */
1103 && ! DECL_BIT_FIELD (cfield))
1110 tree c = fold_const_aggregate_ref (TREE_OPERAND (t, 0));
1111 if (c && TREE_CODE (c) == COMPLEX_CST)
1112 return fold_build1 (TREE_CODE (t), TREE_TYPE (t), c);
1123 /* Evaluate statement STMT. */
1126 evaluate_stmt (tree stmt)
1129 tree simplified = NULL_TREE;
1130 ccp_lattice_t likelyvalue = likely_value (stmt);
1133 val.mem_ref = NULL_TREE;
1135 fold_defer_overflow_warnings ();
1137 /* If the statement is likely to have a CONSTANT result, then try
1138 to fold the statement to determine the constant value. */
1139 if (likelyvalue == CONSTANT)
1140 simplified = ccp_fold (stmt);
1141 /* If the statement is likely to have a VARYING result, then do not
1142 bother folding the statement. */
1143 if (likelyvalue == VARYING)
1144 simplified = get_rhs (stmt);
1145 /* If the statement is an ARRAY_REF or COMPONENT_REF into constant
1146 aggregates, extract the referenced constant. Otherwise the
1147 statement is likely to have an UNDEFINED value, and there will be
1148 nothing to do. Note that fold_const_aggregate_ref returns
1149 NULL_TREE if the first case does not match. */
1150 else if (!simplified)
1151 simplified = fold_const_aggregate_ref (get_rhs (stmt));
1153 is_constant = simplified && is_gimple_min_invariant (simplified);
1155 fold_undefer_overflow_warnings (is_constant, stmt, 0);
1159 /* The statement produced a constant value. */
1160 val.lattice_val = CONSTANT;
1161 val.value = simplified;
1165 /* The statement produced a nonconstant value. If the statement
1166 had UNDEFINED operands, then the result of the statement
1167 should be UNDEFINED. Otherwise, the statement is VARYING. */
1168 if (likelyvalue == UNDEFINED)
1169 val.lattice_val = likelyvalue;
1171 val.lattice_val = VARYING;
1173 val.value = NULL_TREE;
1180 /* Visit the assignment statement STMT. Set the value of its LHS to the
1181 value computed by the RHS and store LHS in *OUTPUT_P. If STMT
1182 creates virtual definitions, set the value of each new name to that
1183 of the RHS (if we can derive a constant out of the RHS). */
1185 static enum ssa_prop_result
1186 visit_assignment (tree stmt, tree *output_p)
1190 enum ssa_prop_result retval;
1192 lhs = GIMPLE_STMT_OPERAND (stmt, 0);
1193 rhs = GIMPLE_STMT_OPERAND (stmt, 1);
1195 if (TREE_CODE (rhs) == SSA_NAME)
1197 /* For a simple copy operation, we copy the lattice values. */
1198 prop_value_t *nval = get_value (rhs);
1201 else if (do_store_ccp && stmt_makes_single_load (stmt))
1203 /* Same as above, but the RHS is not a gimple register and yet
1204 has a known VUSE. If STMT is loading from the same memory
1205 location that created the SSA_NAMEs for the virtual operands,
1206 we can propagate the value on the RHS. */
1207 prop_value_t *nval = get_value_loaded_by (stmt, const_val);
1211 && operand_equal_p (nval->mem_ref, rhs, 0))
1214 val = evaluate_stmt (stmt);
1217 /* Evaluate the statement. */
1218 val = evaluate_stmt (stmt);
1220 /* If the original LHS was a VIEW_CONVERT_EXPR, modify the constant
1221 value to be a VIEW_CONVERT_EXPR of the old constant value.
1223 ??? Also, if this was a definition of a bitfield, we need to widen
1224 the constant value into the type of the destination variable. This
1225 should not be necessary if GCC represented bitfields properly. */
1227 tree orig_lhs = GIMPLE_STMT_OPERAND (stmt, 0);
1229 if (TREE_CODE (orig_lhs) == VIEW_CONVERT_EXPR
1230 && val.lattice_val == CONSTANT)
1232 tree w = fold_unary (VIEW_CONVERT_EXPR,
1233 TREE_TYPE (TREE_OPERAND (orig_lhs, 0)),
1236 orig_lhs = TREE_OPERAND (orig_lhs, 0);
1237 if (w && is_gimple_min_invariant (w))
1241 val.lattice_val = VARYING;
1246 if (val.lattice_val == CONSTANT
1247 && TREE_CODE (orig_lhs) == COMPONENT_REF
1248 && DECL_BIT_FIELD (TREE_OPERAND (orig_lhs, 1)))
1250 tree w = widen_bitfield (val.value, TREE_OPERAND (orig_lhs, 1),
1253 if (w && is_gimple_min_invariant (w))
1257 val.lattice_val = VARYING;
1258 val.value = NULL_TREE;
1259 val.mem_ref = NULL_TREE;
1264 retval = SSA_PROP_NOT_INTERESTING;
1266 /* Set the lattice value of the statement's output. */
1267 if (TREE_CODE (lhs) == SSA_NAME)
1269 /* If STMT is an assignment to an SSA_NAME, we only have one
1271 if (set_lattice_value (lhs, val))
1274 if (val.lattice_val == VARYING)
1275 retval = SSA_PROP_VARYING;
1277 retval = SSA_PROP_INTERESTING;
1280 else if (do_store_ccp && stmt_makes_single_store (stmt))
1282 /* Otherwise, set the names in VDEF operands to the new
1283 constant value and mark the LHS as the memory reference
1284 associated with VAL. */
1289 /* Mark VAL as stored in the LHS of this assignment. */
1290 if (val.lattice_val == CONSTANT)
1293 /* Set the value of every VDEF to VAL. */
1295 FOR_EACH_SSA_TREE_OPERAND (vdef, stmt, i, SSA_OP_VIRTUAL_DEFS)
1297 /* See PR 29801. We may have VDEFs for read-only variables
1298 (see the handling of unmodifiable variables in
1299 add_virtual_operand); do not attempt to change their value. */
1300 if (get_symbol_constant_value (SSA_NAME_VAR (vdef)) != NULL_TREE)
1303 changed |= set_lattice_value (vdef, val);
1306 /* Note that for propagation purposes, we are only interested in
1307 visiting statements that load the exact same memory reference
1308 stored here. Those statements will have the exact same list
1309 of virtual uses, so it is enough to set the output of this
1310 statement to be its first virtual definition. */
1311 *output_p = first_vdef (stmt);
1314 if (val.lattice_val == VARYING)
1315 retval = SSA_PROP_VARYING;
1317 retval = SSA_PROP_INTERESTING;
1325 /* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING
1326 if it can determine which edge will be taken. Otherwise, return
1327 SSA_PROP_VARYING. */
1329 static enum ssa_prop_result
1330 visit_cond_stmt (tree stmt, edge *taken_edge_p)
1335 block = bb_for_stmt (stmt);
1336 val = evaluate_stmt (stmt);
1338 /* Find which edge out of the conditional block will be taken and add it
1339 to the worklist. If no single edge can be determined statically,
1340 return SSA_PROP_VARYING to feed all the outgoing edges to the
1341 propagation engine. */
1342 *taken_edge_p = val.value ? find_taken_edge (block, val.value) : 0;
1344 return SSA_PROP_INTERESTING;
1346 return SSA_PROP_VARYING;
1350 /* Evaluate statement STMT. If the statement produces an output value and
1351 its evaluation changes the lattice value of its output, return
1352 SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the
1355 If STMT is a conditional branch and we can determine its truth
1356 value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying
1357 value, return SSA_PROP_VARYING. */
1359 static enum ssa_prop_result
1360 ccp_visit_stmt (tree stmt, edge *taken_edge_p, tree *output_p)
1365 if (dump_file && (dump_flags & TDF_DETAILS))
1367 fprintf (dump_file, "\nVisiting statement:\n");
1368 print_generic_stmt (dump_file, stmt, dump_flags);
1369 fprintf (dump_file, "\n");
1372 if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
1374 /* If the statement is an assignment that produces a single
1375 output value, evaluate its RHS to see if the lattice value of
1376 its output has changed. */
1377 return visit_assignment (stmt, output_p);
1379 else if (TREE_CODE (stmt) == COND_EXPR || TREE_CODE (stmt) == SWITCH_EXPR)
1381 /* If STMT is a conditional branch, see if we can determine
1382 which branch will be taken. */
1383 return visit_cond_stmt (stmt, taken_edge_p);
1386 /* Any other kind of statement is not interesting for constant
1387 propagation and, therefore, not worth simulating. */
1388 if (dump_file && (dump_flags & TDF_DETAILS))
1389 fprintf (dump_file, "No interesting values produced. Marked VARYING.\n");
1391 /* Definitions made by statements other than assignments to
1392 SSA_NAMEs represent unknown modifications to their outputs.
1393 Mark them VARYING. */
1394 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
1396 prop_value_t v = { VARYING, NULL_TREE, NULL_TREE };
1397 set_lattice_value (def, v);
1400 return SSA_PROP_VARYING;
1404 /* Main entry point for SSA Conditional Constant Propagation. */
1407 execute_ssa_ccp (bool store_ccp)
1409 do_store_ccp = store_ccp;
1411 ssa_propagate (ccp_visit_stmt, ccp_visit_phi_node);
1412 if (ccp_finalize ())
1413 return (TODO_cleanup_cfg | TODO_update_ssa | TODO_remove_unused_locals);
1422 return execute_ssa_ccp (false);
1429 return flag_tree_ccp != 0;
1433 struct tree_opt_pass pass_ccp =
1436 gate_ccp, /* gate */
1437 do_ssa_ccp, /* execute */
1440 0, /* static_pass_number */
1441 TV_TREE_CCP, /* tv_id */
1442 PROP_cfg | PROP_ssa, /* properties_required */
1443 0, /* properties_provided */
1444 0, /* properties_destroyed */
1445 0, /* todo_flags_start */
1446 TODO_dump_func | TODO_verify_ssa
1447 | TODO_verify_stmts | TODO_ggc_collect,/* todo_flags_finish */
1453 do_ssa_store_ccp (void)
1455 /* If STORE-CCP is not enabled, we just run regular CCP. */
1456 return execute_ssa_ccp (flag_tree_store_ccp != 0);
1460 gate_store_ccp (void)
1462 /* STORE-CCP is enabled only with -ftree-store-ccp, but when
1463 -fno-tree-store-ccp is specified, we should run regular CCP.
1464 That's why the pass is enabled with either flag. */
1465 return flag_tree_store_ccp != 0 || flag_tree_ccp != 0;
1469 struct tree_opt_pass pass_store_ccp =
1471 "store_ccp", /* name */
1472 gate_store_ccp, /* gate */
1473 do_ssa_store_ccp, /* execute */
1476 0, /* static_pass_number */
1477 TV_TREE_STORE_CCP, /* tv_id */
1478 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
1479 0, /* properties_provided */
1480 0, /* properties_destroyed */
1481 0, /* todo_flags_start */
1482 TODO_dump_func | TODO_verify_ssa
1483 | TODO_verify_stmts | TODO_ggc_collect,/* todo_flags_finish */
1487 /* Given a constant value VAL for bitfield FIELD, and a destination
1488 variable VAR, return VAL appropriately widened to fit into VAR. If
1489 FIELD is wider than HOST_WIDE_INT, NULL is returned. */
1492 widen_bitfield (tree val, tree field, tree var)
1494 unsigned HOST_WIDE_INT var_size, field_size;
1496 unsigned HOST_WIDE_INT mask;
1499 /* We can only do this if the size of the type and field and VAL are
1500 all constants representable in HOST_WIDE_INT. */
1501 if (!host_integerp (TYPE_SIZE (TREE_TYPE (var)), 1)
1502 || !host_integerp (DECL_SIZE (field), 1)
1503 || !host_integerp (val, 0))
1506 var_size = tree_low_cst (TYPE_SIZE (TREE_TYPE (var)), 1);
1507 field_size = tree_low_cst (DECL_SIZE (field), 1);
1509 /* Give up if either the bitfield or the variable are too wide. */
1510 if (field_size > HOST_BITS_PER_WIDE_INT || var_size > HOST_BITS_PER_WIDE_INT)
1513 gcc_assert (var_size >= field_size);
1515 /* If the sign bit of the value is not set or the field's type is unsigned,
1516 just mask off the high order bits of the value. */
1517 if (DECL_UNSIGNED (field)
1518 || !(tree_low_cst (val, 0) & (((HOST_WIDE_INT)1) << (field_size - 1))))
1520 /* Zero extension. Build a mask with the lower 'field_size' bits
1521 set and a BIT_AND_EXPR node to clear the high order bits of
1523 for (i = 0, mask = 0; i < field_size; i++)
1524 mask |= ((HOST_WIDE_INT) 1) << i;
1526 wide_val = fold_build2 (BIT_AND_EXPR, TREE_TYPE (var), val,
1527 build_int_cst (TREE_TYPE (var), mask));
1531 /* Sign extension. Create a mask with the upper 'field_size'
1532 bits set and a BIT_IOR_EXPR to set the high order bits of the
1534 for (i = 0, mask = 0; i < (var_size - field_size); i++)
1535 mask |= ((HOST_WIDE_INT) 1) << (var_size - i - 1);
1537 wide_val = fold_build2 (BIT_IOR_EXPR, TREE_TYPE (var), val,
1538 build_int_cst (TREE_TYPE (var), mask));
1545 /* A subroutine of fold_stmt_r. Attempts to fold *(A+O) to A[X].
1546 BASE is an array type. OFFSET is a byte displacement. ORIG_TYPE
1547 is the desired result type. */
1550 maybe_fold_offset_to_array_ref (tree base, tree offset, tree orig_type)
1552 tree min_idx, idx, idx_type, elt_offset = integer_zero_node;
1553 tree array_type, elt_type, elt_size;
1555 /* If BASE is an ARRAY_REF, we can pick up another offset (this time
1556 measured in units of the size of elements type) from that ARRAY_REF).
1557 We can't do anything if either is variable.
1559 The case we handle here is *(&A[N]+O). */
1560 if (TREE_CODE (base) == ARRAY_REF)
1562 tree low_bound = array_ref_low_bound (base);
1564 elt_offset = TREE_OPERAND (base, 1);
1565 if (TREE_CODE (low_bound) != INTEGER_CST
1566 || TREE_CODE (elt_offset) != INTEGER_CST)
1569 elt_offset = int_const_binop (MINUS_EXPR, elt_offset, low_bound, 0);
1570 base = TREE_OPERAND (base, 0);
1573 /* Ignore stupid user tricks of indexing non-array variables. */
1574 array_type = TREE_TYPE (base);
1575 if (TREE_CODE (array_type) != ARRAY_TYPE)
1577 elt_type = TREE_TYPE (array_type);
1578 if (!useless_type_conversion_p (orig_type, elt_type))
1581 /* Use signed size type for intermediate computation on the index. */
1582 idx_type = signed_type_for (size_type_node);
1584 /* If OFFSET and ELT_OFFSET are zero, we don't care about the size of the
1585 element type (so we can use the alignment if it's not constant).
1586 Otherwise, compute the offset as an index by using a division. If the
1587 division isn't exact, then don't do anything. */
1588 elt_size = TYPE_SIZE_UNIT (elt_type);
1591 if (integer_zerop (offset))
1593 if (TREE_CODE (elt_size) != INTEGER_CST)
1594 elt_size = size_int (TYPE_ALIGN (elt_type));
1596 idx = build_int_cst (idx_type, 0);
1600 unsigned HOST_WIDE_INT lquo, lrem;
1601 HOST_WIDE_INT hquo, hrem;
1604 /* The final array offset should be signed, so we need
1605 to sign-extend the (possibly pointer) offset here
1606 and use signed division. */
1607 soffset = double_int_sext (tree_to_double_int (offset),
1608 TYPE_PRECISION (TREE_TYPE (offset)));
1609 if (TREE_CODE (elt_size) != INTEGER_CST
1610 || div_and_round_double (TRUNC_DIV_EXPR, 0,
1611 soffset.low, soffset.high,
1612 TREE_INT_CST_LOW (elt_size),
1613 TREE_INT_CST_HIGH (elt_size),
1614 &lquo, &hquo, &lrem, &hrem)
1618 idx = build_int_cst_wide (idx_type, lquo, hquo);
1621 /* Assume the low bound is zero. If there is a domain type, get the
1622 low bound, if any, convert the index into that type, and add the
1624 min_idx = build_int_cst (idx_type, 0);
1625 if (TYPE_DOMAIN (array_type))
1627 idx_type = TYPE_DOMAIN (array_type);
1628 if (TYPE_MIN_VALUE (idx_type))
1629 min_idx = TYPE_MIN_VALUE (idx_type);
1631 min_idx = fold_convert (idx_type, min_idx);
1633 if (TREE_CODE (min_idx) != INTEGER_CST)
1636 elt_offset = fold_convert (idx_type, elt_offset);
1639 if (!integer_zerop (min_idx))
1640 idx = int_const_binop (PLUS_EXPR, idx, min_idx, 0);
1641 if (!integer_zerop (elt_offset))
1642 idx = int_const_binop (PLUS_EXPR, idx, elt_offset, 0);
1644 /* Make sure to possibly truncate late after offsetting. */
1645 idx = fold_convert (idx_type, idx);
1647 return build4 (ARRAY_REF, orig_type, base, idx, NULL_TREE, NULL_TREE);
1651 /* Attempt to fold *(S+O) to S.X.
1652 BASE is a record type. OFFSET is a byte displacement. ORIG_TYPE
1653 is the desired result type. */
1656 maybe_fold_offset_to_component_ref (tree record_type, tree base, tree offset,
1657 tree orig_type, bool base_is_ptr)
1659 tree f, t, field_type, tail_array_field, field_offset;
1663 if (TREE_CODE (record_type) != RECORD_TYPE
1664 && TREE_CODE (record_type) != UNION_TYPE
1665 && TREE_CODE (record_type) != QUAL_UNION_TYPE)
1668 /* Short-circuit silly cases. */
1669 if (useless_type_conversion_p (record_type, orig_type))
1672 tail_array_field = NULL_TREE;
1673 for (f = TYPE_FIELDS (record_type); f ; f = TREE_CHAIN (f))
1677 if (TREE_CODE (f) != FIELD_DECL)
1679 if (DECL_BIT_FIELD (f))
1682 if (!DECL_FIELD_OFFSET (f))
1684 field_offset = byte_position (f);
1685 if (TREE_CODE (field_offset) != INTEGER_CST)
1688 /* ??? Java creates "interesting" fields for representing base classes.
1689 They have no name, and have no context. With no context, we get into
1690 trouble with nonoverlapping_component_refs_p. Skip them. */
1691 if (!DECL_FIELD_CONTEXT (f))
1694 /* The previous array field isn't at the end. */
1695 tail_array_field = NULL_TREE;
1697 /* Check to see if this offset overlaps with the field. */
1698 cmp = tree_int_cst_compare (field_offset, offset);
1702 field_type = TREE_TYPE (f);
1704 /* Here we exactly match the offset being checked. If the types match,
1705 then we can return that field. */
1707 && useless_type_conversion_p (orig_type, field_type))
1710 base = build1 (INDIRECT_REF, record_type, base);
1711 t = build3 (COMPONENT_REF, field_type, base, f, NULL_TREE);
1715 /* Don't care about offsets into the middle of scalars. */
1716 if (!AGGREGATE_TYPE_P (field_type))
1719 /* Check for array at the end of the struct. This is often
1720 used as for flexible array members. We should be able to
1721 turn this into an array access anyway. */
1722 if (TREE_CODE (field_type) == ARRAY_TYPE)
1723 tail_array_field = f;
1725 /* Check the end of the field against the offset. */
1726 if (!DECL_SIZE_UNIT (f)
1727 || TREE_CODE (DECL_SIZE_UNIT (f)) != INTEGER_CST)
1729 t = int_const_binop (MINUS_EXPR, offset, field_offset, 1);
1730 if (!tree_int_cst_lt (t, DECL_SIZE_UNIT (f)))
1733 /* If we matched, then set offset to the displacement into
1736 new_base = build1 (INDIRECT_REF, record_type, base);
1739 new_base = build3 (COMPONENT_REF, field_type, new_base, f, NULL_TREE);
1741 /* Recurse to possibly find the match. */
1742 ret = maybe_fold_offset_to_array_ref (new_base, t, orig_type);
1745 ret = maybe_fold_offset_to_component_ref (field_type, new_base, t,
1751 if (!tail_array_field)
1754 f = tail_array_field;
1755 field_type = TREE_TYPE (f);
1756 offset = int_const_binop (MINUS_EXPR, offset, byte_position (f), 1);
1758 /* If we get here, we've got an aggregate field, and a possibly
1759 nonzero offset into them. Recurse and hope for a valid match. */
1761 base = build1 (INDIRECT_REF, record_type, base);
1762 base = build3 (COMPONENT_REF, field_type, base, f, NULL_TREE);
1764 t = maybe_fold_offset_to_array_ref (base, offset, orig_type);
1767 return maybe_fold_offset_to_component_ref (field_type, base, offset,
1771 /* Attempt to express (ORIG_TYPE)BASE+OFFSET as BASE->field_of_orig_type
1772 or BASE[index] or by combination of those.
1774 Before attempting the conversion strip off existing ADDR_EXPRs and
1775 handled component refs. */
1778 maybe_fold_offset_to_reference (tree base, tree offset, tree orig_type)
1782 bool base_is_ptr = true;
1785 if (TREE_CODE (base) == ADDR_EXPR)
1787 base_is_ptr = false;
1789 base = TREE_OPERAND (base, 0);
1791 /* Handle case where existing COMPONENT_REF pick e.g. wrong field of union,
1792 so it needs to be removed and new COMPONENT_REF constructed.
1793 The wrong COMPONENT_REF are often constructed by folding the
1794 (type *)&object within the expression (type *)&object+offset */
1795 if (handled_component_p (base) && 0)
1797 HOST_WIDE_INT sub_offset, size, maxsize;
1799 newbase = get_ref_base_and_extent (base, &sub_offset,
1801 gcc_assert (newbase);
1802 gcc_assert (!(sub_offset & (BITS_PER_UNIT - 1)));
1803 if (size == maxsize)
1807 offset = int_const_binop (PLUS_EXPR, offset,
1808 build_int_cst (TREE_TYPE (offset),
1809 sub_offset / BITS_PER_UNIT), 1);
1812 if (useless_type_conversion_p (orig_type, TREE_TYPE (base))
1813 && integer_zerop (offset))
1815 type = TREE_TYPE (base);
1820 if (!POINTER_TYPE_P (TREE_TYPE (base)))
1822 type = TREE_TYPE (TREE_TYPE (base));
1824 ret = maybe_fold_offset_to_component_ref (type, base, offset,
1825 orig_type, base_is_ptr);
1829 base = build1 (INDIRECT_REF, type, base);
1830 ret = maybe_fold_offset_to_array_ref (base, offset, orig_type);
1835 /* A subroutine of fold_stmt_r. Attempt to simplify *(BASE+OFFSET).
1836 Return the simplified expression, or NULL if nothing could be done. */
1839 maybe_fold_stmt_indirect (tree expr, tree base, tree offset)
1843 /* We may well have constructed a double-nested PLUS_EXPR via multiple
1844 substitutions. Fold that down to one. Remove NON_LVALUE_EXPRs that
1845 are sometimes added. */
1847 STRIP_TYPE_NOPS (base);
1848 TREE_OPERAND (expr, 0) = base;
1850 /* One possibility is that the address reduces to a string constant. */
1851 t = fold_read_from_constant_string (expr);
1855 /* Add in any offset from a POINTER_PLUS_EXPR. */
1856 if (TREE_CODE (base) == POINTER_PLUS_EXPR)
1860 offset2 = TREE_OPERAND (base, 1);
1861 if (TREE_CODE (offset2) != INTEGER_CST)
1863 base = TREE_OPERAND (base, 0);
1865 offset = fold_convert (sizetype,
1866 int_const_binop (PLUS_EXPR, offset, offset2, 1));
1869 if (TREE_CODE (base) == ADDR_EXPR)
1871 tree base_addr = base;
1873 /* Strip the ADDR_EXPR. */
1874 base = TREE_OPERAND (base, 0);
1876 /* Fold away CONST_DECL to its value, if the type is scalar. */
1877 if (TREE_CODE (base) == CONST_DECL
1878 && ccp_decl_initial_min_invariant (DECL_INITIAL (base)))
1879 return DECL_INITIAL (base);
1881 /* Try folding *(&B+O) to B.X. */
1882 t = maybe_fold_offset_to_reference (base_addr, offset,
1889 /* We can get here for out-of-range string constant accesses,
1890 such as "_"[3]. Bail out of the entire substitution search
1891 and arrange for the entire statement to be replaced by a
1892 call to __builtin_trap. In all likelihood this will all be
1893 constant-folded away, but in the meantime we can't leave with
1894 something that get_expr_operands can't understand. */
1898 if (TREE_CODE (t) == ADDR_EXPR
1899 && TREE_CODE (TREE_OPERAND (t, 0)) == STRING_CST)
1901 /* FIXME: Except that this causes problems elsewhere with dead
1902 code not being deleted, and we die in the rtl expanders
1903 because we failed to remove some ssa_name. In the meantime,
1904 just return zero. */
1905 /* FIXME2: This condition should be signaled by
1906 fold_read_from_constant_string directly, rather than
1907 re-checking for it here. */
1908 return integer_zero_node;
1911 /* Try folding *(B+O) to B->X. Still an improvement. */
1912 if (POINTER_TYPE_P (TREE_TYPE (base)))
1914 t = maybe_fold_offset_to_reference (base, offset,
1921 /* Otherwise we had an offset that we could not simplify. */
1926 /* A subroutine of fold_stmt_r. EXPR is a POINTER_PLUS_EXPR.
1928 A quaint feature extant in our address arithmetic is that there
1929 can be hidden type changes here. The type of the result need
1930 not be the same as the type of the input pointer.
1932 What we're after here is an expression of the form
1933 (T *)(&array + const)
1934 where the cast doesn't actually exist, but is implicit in the
1935 type of the POINTER_PLUS_EXPR. We'd like to turn this into
1937 which may be able to propagate further. */
1940 maybe_fold_stmt_addition (tree expr)
1942 tree op0 = TREE_OPERAND (expr, 0);
1943 tree op1 = TREE_OPERAND (expr, 1);
1944 tree ptr_type = TREE_TYPE (expr);
1948 gcc_assert (TREE_CODE (expr) == POINTER_PLUS_EXPR);
1950 /* It had better be a constant. */
1951 if (TREE_CODE (op1) != INTEGER_CST)
1953 /* The first operand should be an ADDR_EXPR. */
1954 if (TREE_CODE (op0) != ADDR_EXPR)
1956 op0 = TREE_OPERAND (op0, 0);
1958 /* If the first operand is an ARRAY_REF, expand it so that we can fold
1959 the offset into it. */
1960 while (TREE_CODE (op0) == ARRAY_REF)
1962 tree array_obj = TREE_OPERAND (op0, 0);
1963 tree array_idx = TREE_OPERAND (op0, 1);
1964 tree elt_type = TREE_TYPE (op0);
1965 tree elt_size = TYPE_SIZE_UNIT (elt_type);
1968 if (TREE_CODE (array_idx) != INTEGER_CST)
1970 if (TREE_CODE (elt_size) != INTEGER_CST)
1973 /* Un-bias the index by the min index of the array type. */
1974 min_idx = TYPE_DOMAIN (TREE_TYPE (array_obj));
1977 min_idx = TYPE_MIN_VALUE (min_idx);
1980 if (TREE_CODE (min_idx) != INTEGER_CST)
1983 array_idx = fold_convert (TREE_TYPE (min_idx), array_idx);
1984 if (!integer_zerop (min_idx))
1985 array_idx = int_const_binop (MINUS_EXPR, array_idx,
1990 /* Convert the index to a byte offset. */
1991 array_idx = fold_convert (sizetype, array_idx);
1992 array_idx = int_const_binop (MULT_EXPR, array_idx, elt_size, 0);
1994 /* Update the operands for the next round, or for folding. */
1995 op1 = int_const_binop (PLUS_EXPR,
2000 ptd_type = TREE_TYPE (ptr_type);
2002 /* At which point we can try some of the same things as for indirects. */
2003 t = maybe_fold_offset_to_array_ref (op0, op1, ptd_type);
2005 t = maybe_fold_offset_to_component_ref (TREE_TYPE (op0), op0, op1,
2008 t = build1 (ADDR_EXPR, ptr_type, t);
2013 /* For passing state through walk_tree into fold_stmt_r and its
2016 struct fold_stmt_r_data
2020 bool *inside_addr_expr_p;
2023 /* Subroutine of fold_stmt called via walk_tree. We perform several
2024 simplifications of EXPR_P, mostly having to do with pointer arithmetic. */
2027 fold_stmt_r (tree *expr_p, int *walk_subtrees, void *data)
2029 struct fold_stmt_r_data *fold_stmt_r_data = (struct fold_stmt_r_data *) data;
2030 bool *inside_addr_expr_p = fold_stmt_r_data->inside_addr_expr_p;
2031 bool *changed_p = fold_stmt_r_data->changed_p;
2032 tree expr = *expr_p, t;
2034 /* ??? It'd be nice if walk_tree had a pre-order option. */
2035 switch (TREE_CODE (expr))
2038 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
2043 t = maybe_fold_stmt_indirect (expr, TREE_OPERAND (expr, 0),
2048 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
2053 if (POINTER_TYPE_P (TREE_TYPE (expr))
2054 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (expr, 0)))
2055 && (t = maybe_fold_offset_to_reference
2056 (TREE_OPERAND (expr, 0),
2058 TREE_TYPE (TREE_TYPE (expr)))))
2059 t = build_fold_addr_expr_with_type (t, TREE_TYPE (expr));
2062 /* ??? Could handle more ARRAY_REFs here, as a variant of INDIRECT_REF.
2063 We'd only want to bother decomposing an existing ARRAY_REF if
2064 the base array is found to have another offset contained within.
2065 Otherwise we'd be wasting time. */
2067 /* If we are not processing expressions found within an
2068 ADDR_EXPR, then we can fold constant array references. */
2069 if (!*inside_addr_expr_p)
2070 t = fold_read_from_constant_string (expr);
2076 *inside_addr_expr_p = true;
2077 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
2078 *inside_addr_expr_p = false;
2083 /* Set TREE_INVARIANT properly so that the value is properly
2084 considered constant, and so gets propagated as expected. */
2086 recompute_tree_invariant_for_addr_expr (expr);
2089 case POINTER_PLUS_EXPR:
2090 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
2093 t = walk_tree (&TREE_OPERAND (expr, 1), fold_stmt_r, data, NULL);
2098 t = maybe_fold_stmt_addition (expr);
2102 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
2107 /* Make sure the FIELD_DECL is actually a field in the type on the lhs.
2108 We've already checked that the records are compatible, so we should
2109 come up with a set of compatible fields. */
2111 tree expr_record = TREE_TYPE (TREE_OPERAND (expr, 0));
2112 tree expr_field = TREE_OPERAND (expr, 1);
2114 if (DECL_FIELD_CONTEXT (expr_field) != TYPE_MAIN_VARIANT (expr_record))
2116 expr_field = find_compatible_field (expr_record, expr_field);
2117 TREE_OPERAND (expr, 1) = expr_field;
2122 case TARGET_MEM_REF:
2123 t = maybe_fold_tmr (expr);
2127 if (COMPARISON_CLASS_P (TREE_OPERAND (expr, 0)))
2129 tree op0 = TREE_OPERAND (expr, 0);
2133 fold_defer_overflow_warnings ();
2134 tem = fold_binary (TREE_CODE (op0), TREE_TYPE (op0),
2135 TREE_OPERAND (op0, 0),
2136 TREE_OPERAND (op0, 1));
2137 set = tem && set_rhs (expr_p, tem);
2138 fold_undefer_overflow_warnings (set, fold_stmt_r_data->stmt, 0);
2161 /* Return the string length, maximum string length or maximum value of
2163 If ARG is an SSA name variable, follow its use-def chains. If LENGTH
2164 is not NULL and, for TYPE == 0, its value is not equal to the length
2165 we determine or if we are unable to determine the length or value,
2166 return false. VISITED is a bitmap of visited variables.
2167 TYPE is 0 if string length should be returned, 1 for maximum string
2168 length and 2 for maximum value ARG can have. */
2171 get_maxval_strlen (tree arg, tree *length, bitmap visited, int type)
2173 tree var, def_stmt, val;
2175 if (TREE_CODE (arg) != SSA_NAME)
2177 if (TREE_CODE (arg) == COND_EXPR)
2178 return get_maxval_strlen (COND_EXPR_THEN (arg), length, visited, type)
2179 && get_maxval_strlen (COND_EXPR_ELSE (arg), length, visited, type);
2184 if (TREE_CODE (val) != INTEGER_CST
2185 || tree_int_cst_sgn (val) < 0)
2189 val = c_strlen (arg, 1);
2197 if (TREE_CODE (*length) != INTEGER_CST
2198 || TREE_CODE (val) != INTEGER_CST)
2201 if (tree_int_cst_lt (*length, val))
2205 else if (simple_cst_equal (val, *length) != 1)
2213 /* If we were already here, break the infinite cycle. */
2214 if (bitmap_bit_p (visited, SSA_NAME_VERSION (arg)))
2216 bitmap_set_bit (visited, SSA_NAME_VERSION (arg));
2219 def_stmt = SSA_NAME_DEF_STMT (var);
2221 switch (TREE_CODE (def_stmt))
2223 case GIMPLE_MODIFY_STMT:
2227 /* The RHS of the statement defining VAR must either have a
2228 constant length or come from another SSA_NAME with a constant
2230 rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
2232 return get_maxval_strlen (rhs, length, visited, type);
2237 /* All the arguments of the PHI node must have the same constant
2241 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
2243 tree arg = PHI_ARG_DEF (def_stmt, i);
2245 /* If this PHI has itself as an argument, we cannot
2246 determine the string length of this argument. However,
2247 if we can find a constant string length for the other
2248 PHI args then we can still be sure that this is a
2249 constant string length. So be optimistic and just
2250 continue with the next argument. */
2251 if (arg == PHI_RESULT (def_stmt))
2254 if (!get_maxval_strlen (arg, length, visited, type))
2270 /* Fold builtin call FN in statement STMT. If it cannot be folded into a
2271 constant, return NULL_TREE. Otherwise, return its constant value. */
2274 ccp_fold_builtin (tree stmt, tree fn)
2276 tree result, val[3];
2278 int arg_mask, i, type;
2281 call_expr_arg_iterator iter;
2284 ignore = TREE_CODE (stmt) != GIMPLE_MODIFY_STMT;
2286 /* First try the generic builtin folder. If that succeeds, return the
2288 result = fold_call_expr (fn, ignore);
2292 STRIP_NOPS (result);
2296 /* Ignore MD builtins. */
2297 callee = get_callee_fndecl (fn);
2298 if (DECL_BUILT_IN_CLASS (callee) == BUILT_IN_MD)
2301 /* If the builtin could not be folded, and it has no argument list,
2303 nargs = call_expr_nargs (fn);
2307 /* Limit the work only for builtins we know how to simplify. */
2308 switch (DECL_FUNCTION_CODE (callee))
2310 case BUILT_IN_STRLEN:
2311 case BUILT_IN_FPUTS:
2312 case BUILT_IN_FPUTS_UNLOCKED:
2316 case BUILT_IN_STRCPY:
2317 case BUILT_IN_STRNCPY:
2321 case BUILT_IN_MEMCPY_CHK:
2322 case BUILT_IN_MEMPCPY_CHK:
2323 case BUILT_IN_MEMMOVE_CHK:
2324 case BUILT_IN_MEMSET_CHK:
2325 case BUILT_IN_STRNCPY_CHK:
2329 case BUILT_IN_STRCPY_CHK:
2330 case BUILT_IN_STPCPY_CHK:
2334 case BUILT_IN_SNPRINTF_CHK:
2335 case BUILT_IN_VSNPRINTF_CHK:
2343 /* Try to use the dataflow information gathered by the CCP process. */
2344 visited = BITMAP_ALLOC (NULL);
2346 memset (val, 0, sizeof (val));
2347 init_call_expr_arg_iterator (fn, &iter);
2348 for (i = 0; arg_mask; i++, arg_mask >>= 1)
2350 a = next_call_expr_arg (&iter);
2353 bitmap_clear (visited);
2354 if (!get_maxval_strlen (a, &val[i], visited, type))
2359 BITMAP_FREE (visited);
2362 switch (DECL_FUNCTION_CODE (callee))
2364 case BUILT_IN_STRLEN:
2367 tree new_val = fold_convert (TREE_TYPE (fn), val[0]);
2369 /* If the result is not a valid gimple value, or not a cast
2370 of a valid gimple value, then we can not use the result. */
2371 if (is_gimple_val (new_val)
2372 || (is_gimple_cast (new_val)
2373 && is_gimple_val (TREE_OPERAND (new_val, 0))))
2378 case BUILT_IN_STRCPY:
2379 if (val[1] && is_gimple_val (val[1]) && nargs == 2)
2380 result = fold_builtin_strcpy (callee,
2381 CALL_EXPR_ARG (fn, 0),
2382 CALL_EXPR_ARG (fn, 1),
2386 case BUILT_IN_STRNCPY:
2387 if (val[1] && is_gimple_val (val[1]) && nargs == 3)
2388 result = fold_builtin_strncpy (callee,
2389 CALL_EXPR_ARG (fn, 0),
2390 CALL_EXPR_ARG (fn, 1),
2391 CALL_EXPR_ARG (fn, 2),
2395 case BUILT_IN_FPUTS:
2396 result = fold_builtin_fputs (CALL_EXPR_ARG (fn, 0),
2397 CALL_EXPR_ARG (fn, 1),
2398 TREE_CODE (stmt) != GIMPLE_MODIFY_STMT, 0,
2402 case BUILT_IN_FPUTS_UNLOCKED:
2403 result = fold_builtin_fputs (CALL_EXPR_ARG (fn, 0),
2404 CALL_EXPR_ARG (fn, 1),
2405 TREE_CODE (stmt) != GIMPLE_MODIFY_STMT, 1,
2409 case BUILT_IN_MEMCPY_CHK:
2410 case BUILT_IN_MEMPCPY_CHK:
2411 case BUILT_IN_MEMMOVE_CHK:
2412 case BUILT_IN_MEMSET_CHK:
2413 if (val[2] && is_gimple_val (val[2]))
2414 result = fold_builtin_memory_chk (callee,
2415 CALL_EXPR_ARG (fn, 0),
2416 CALL_EXPR_ARG (fn, 1),
2417 CALL_EXPR_ARG (fn, 2),
2418 CALL_EXPR_ARG (fn, 3),
2420 DECL_FUNCTION_CODE (callee));
2423 case BUILT_IN_STRCPY_CHK:
2424 case BUILT_IN_STPCPY_CHK:
2425 if (val[1] && is_gimple_val (val[1]))
2426 result = fold_builtin_stxcpy_chk (callee,
2427 CALL_EXPR_ARG (fn, 0),
2428 CALL_EXPR_ARG (fn, 1),
2429 CALL_EXPR_ARG (fn, 2),
2431 DECL_FUNCTION_CODE (callee));
2434 case BUILT_IN_STRNCPY_CHK:
2435 if (val[2] && is_gimple_val (val[2]))
2436 result = fold_builtin_strncpy_chk (CALL_EXPR_ARG (fn, 0),
2437 CALL_EXPR_ARG (fn, 1),
2438 CALL_EXPR_ARG (fn, 2),
2439 CALL_EXPR_ARG (fn, 3),
2443 case BUILT_IN_SNPRINTF_CHK:
2444 case BUILT_IN_VSNPRINTF_CHK:
2445 if (val[1] && is_gimple_val (val[1]))
2446 result = fold_builtin_snprintf_chk (fn, val[1],
2447 DECL_FUNCTION_CODE (callee));
2454 if (result && ignore)
2455 result = fold_ignored_result (result);
2460 /* Fold the statement pointed to by STMT_P. In some cases, this function may
2461 replace the whole statement with a new one. Returns true iff folding
2462 makes any changes. */
2465 fold_stmt (tree *stmt_p)
2467 tree rhs, result, stmt;
2468 struct fold_stmt_r_data fold_stmt_r_data;
2469 bool changed = false;
2470 bool inside_addr_expr = false;
2474 fold_stmt_r_data.stmt = stmt;
2475 fold_stmt_r_data.changed_p = &changed;
2476 fold_stmt_r_data.inside_addr_expr_p = &inside_addr_expr;
2478 /* If we replaced constants and the statement makes pointer dereferences,
2479 then we may need to fold instances of *&VAR into VAR, etc. */
2480 if (walk_tree (stmt_p, fold_stmt_r, &fold_stmt_r_data, NULL))
2482 *stmt_p = build_call_expr (implicit_built_in_decls[BUILT_IN_TRAP], 0);
2486 rhs = get_rhs (stmt);
2491 if (TREE_CODE (rhs) == CALL_EXPR)
2495 /* Check for builtins that CCP can handle using information not
2496 available in the generic fold routines. */
2497 callee = get_callee_fndecl (rhs);
2498 if (callee && DECL_BUILT_IN (callee))
2499 result = ccp_fold_builtin (stmt, rhs);
2502 /* Check for resolvable OBJ_TYPE_REF. The only sorts we can resolve
2503 here are when we've propagated the address of a decl into the
2505 /* ??? Should perhaps do this in fold proper. However, doing it
2506 there requires that we create a new CALL_EXPR, and that requires
2507 copying EH region info to the new node. Easier to just do it
2508 here where we can just smash the call operand. Also
2509 CALL_EXPR_RETURN_SLOT_OPT needs to be handled correctly and
2510 copied, fold_call_expr does not have not information. */
2511 callee = CALL_EXPR_FN (rhs);
2512 if (TREE_CODE (callee) == OBJ_TYPE_REF
2513 && lang_hooks.fold_obj_type_ref
2514 && TREE_CODE (OBJ_TYPE_REF_OBJECT (callee)) == ADDR_EXPR
2515 && DECL_P (TREE_OPERAND
2516 (OBJ_TYPE_REF_OBJECT (callee), 0)))
2520 /* ??? Caution: Broken ADDR_EXPR semantics means that
2521 looking at the type of the operand of the addr_expr
2522 can yield an array type. See silly exception in
2523 check_pointer_types_r. */
2525 t = TREE_TYPE (TREE_TYPE (OBJ_TYPE_REF_OBJECT (callee)));
2526 t = lang_hooks.fold_obj_type_ref (callee, t);
2529 CALL_EXPR_FN (rhs) = t;
2535 else if (TREE_CODE (rhs) == COND_EXPR)
2537 tree temp = fold (COND_EXPR_COND (rhs));
2538 if (temp != COND_EXPR_COND (rhs))
2539 result = fold_build3 (COND_EXPR, TREE_TYPE (rhs), temp,
2540 COND_EXPR_THEN (rhs), COND_EXPR_ELSE (rhs));
2543 /* If we couldn't fold the RHS, hand over to the generic fold routines. */
2544 if (result == NULL_TREE)
2545 result = fold (rhs);
2547 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
2548 may have been added by fold, and "useless" type conversions that might
2549 now be apparent due to propagation. */
2550 STRIP_USELESS_TYPE_CONVERSION (result);
2553 changed |= set_rhs (stmt_p, result);
2558 /* Perform the minimal folding on statement STMT. Only operations like
2559 *&x created by constant propagation are handled. The statement cannot
2560 be replaced with a new one. */
2563 fold_stmt_inplace (tree stmt)
2565 tree old_stmt = stmt, rhs, new_rhs;
2566 struct fold_stmt_r_data fold_stmt_r_data;
2567 bool changed = false;
2568 bool inside_addr_expr = false;
2570 fold_stmt_r_data.stmt = stmt;
2571 fold_stmt_r_data.changed_p = &changed;
2572 fold_stmt_r_data.inside_addr_expr_p = &inside_addr_expr;
2574 walk_tree (&stmt, fold_stmt_r, &fold_stmt_r_data, NULL);
2575 gcc_assert (stmt == old_stmt);
2577 rhs = get_rhs (stmt);
2578 if (!rhs || rhs == stmt)
2581 new_rhs = fold (rhs);
2582 STRIP_USELESS_TYPE_CONVERSION (new_rhs);
2586 changed |= set_rhs (&stmt, new_rhs);
2587 gcc_assert (stmt == old_stmt);
2592 /* Convert EXPR into a GIMPLE value suitable for substitution on the
2593 RHS of an assignment. Insert the necessary statements before
2595 When IGNORE is set, don't worry about the return value. */
2598 convert_to_gimple_builtin (block_stmt_iterator *si_p, tree expr, bool ignore)
2600 tree_stmt_iterator ti;
2601 tree stmt = bsi_stmt (*si_p);
2602 tree tmp, stmts = NULL;
2604 push_gimplify_context ();
2607 tmp = build_empty_stmt ();
2608 gimplify_and_add (expr, &stmts);
2611 tmp = get_initialized_tmp_var (expr, &stmts, NULL);
2612 pop_gimplify_context (NULL);
2614 if (EXPR_HAS_LOCATION (stmt))
2615 annotate_all_with_locus (&stmts, EXPR_LOCATION (stmt));
2617 /* The replacement can expose previously unreferenced variables. */
2618 for (ti = tsi_start (stmts); !tsi_end_p (ti); tsi_next (&ti))
2620 tree new_stmt = tsi_stmt (ti);
2621 find_new_referenced_vars (tsi_stmt_ptr (ti));
2622 bsi_insert_before (si_p, new_stmt, BSI_NEW_STMT);
2623 mark_symbols_for_renaming (new_stmt);
2631 /* A simple pass that attempts to fold all builtin functions. This pass
2632 is run after we've propagated as many constants as we can. */
2635 execute_fold_all_builtins (void)
2637 bool cfg_changed = false;
2641 block_stmt_iterator i;
2642 for (i = bsi_start (bb); !bsi_end_p (i); )
2644 tree *stmtp = bsi_stmt_ptr (i);
2645 tree old_stmt = *stmtp;
2646 tree call = get_rhs (*stmtp);
2647 tree callee, result;
2648 enum built_in_function fcode;
2650 if (!call || TREE_CODE (call) != CALL_EXPR)
2655 callee = get_callee_fndecl (call);
2656 if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)
2661 fcode = DECL_FUNCTION_CODE (callee);
2663 result = ccp_fold_builtin (*stmtp, call);
2665 switch (DECL_FUNCTION_CODE (callee))
2667 case BUILT_IN_CONSTANT_P:
2668 /* Resolve __builtin_constant_p. If it hasn't been
2669 folded to integer_one_node by now, it's fairly
2670 certain that the value simply isn't constant. */
2671 result = integer_zero_node;
2679 if (dump_file && (dump_flags & TDF_DETAILS))
2681 fprintf (dump_file, "Simplified\n ");
2682 print_generic_stmt (dump_file, *stmtp, dump_flags);
2685 push_stmt_changes (stmtp);
2687 if (!set_rhs (stmtp, result))
2689 result = convert_to_gimple_builtin (&i, result,
2690 TREE_CODE (old_stmt)
2691 != GIMPLE_MODIFY_STMT);
2694 bool ok = set_rhs (stmtp, result);
2699 pop_stmt_changes (stmtp);
2701 if (maybe_clean_or_replace_eh_stmt (old_stmt, *stmtp)
2702 && tree_purge_dead_eh_edges (bb))
2705 if (dump_file && (dump_flags & TDF_DETAILS))
2707 fprintf (dump_file, "to\n ");
2708 print_generic_stmt (dump_file, *stmtp, dump_flags);
2709 fprintf (dump_file, "\n");
2712 /* Retry the same statement if it changed into another
2713 builtin, there might be new opportunities now. */
2714 call = get_rhs (*stmtp);
2715 if (!call || TREE_CODE (call) != CALL_EXPR)
2720 callee = get_callee_fndecl (call);
2722 || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL
2723 || DECL_FUNCTION_CODE (callee) == fcode)
2728 /* Delete unreachable blocks. */
2729 return cfg_changed ? TODO_cleanup_cfg : 0;
2733 struct tree_opt_pass pass_fold_builtins =
2737 execute_fold_all_builtins, /* execute */
2740 0, /* static_pass_number */
2742 PROP_cfg | PROP_ssa, /* properties_required */
2743 0, /* properties_provided */
2744 0, /* properties_destroyed */
2745 0, /* todo_flags_start */
2748 | TODO_update_ssa, /* todo_flags_finish */