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 3, 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 COPYING3. If not see
21 <http://www.gnu.org/licenses/>. */
23 /* Conditional constant propagation (CCP) is based on the SSA
24 propagation engine (tree-ssa-propagate.c). Constant assignments of
25 the form VAR = CST are propagated from the assignments into uses of
26 VAR, which in turn may generate new constants. The simulation uses
27 a four level lattice to keep track of constant values associated
28 with SSA names. Given an SSA name V_i, it may take one of the
31 UNINITIALIZED -> the initial state of the value. This value
32 is replaced with a correct initial value
33 the first time the value is used, so the
34 rest of the pass does not need to care about
35 it. Using this value simplifies initialization
36 of the pass, and prevents us from needlessly
37 scanning statements that are never reached.
39 UNDEFINED -> V_i is a local variable whose definition
40 has not been processed yet. Therefore we
41 don't yet know if its value is a constant
44 CONSTANT -> V_i has been found to hold a constant
47 VARYING -> V_i cannot take a constant value, or if it
48 does, it is not possible to determine it
51 The core of SSA-CCP is in ccp_visit_stmt and ccp_visit_phi_node:
53 1- In ccp_visit_stmt, we are interested in assignments whose RHS
54 evaluates into a constant and conditional jumps whose predicate
55 evaluates into a boolean true or false. When an assignment of
56 the form V_i = CONST is found, V_i's lattice value is set to
57 CONSTANT and CONST is associated with it. This causes the
58 propagation engine to add all the SSA edges coming out the
59 assignment into the worklists, so that statements that use V_i
62 If the statement is a conditional with a constant predicate, we
63 mark the outgoing edges as executable or not executable
64 depending on the predicate's value. This is then used when
65 visiting PHI nodes to know when a PHI argument can be ignored.
68 2- In ccp_visit_phi_node, if all the PHI arguments evaluate to the
69 same constant C, then the LHS of the PHI is set to C. This
70 evaluation is known as the "meet operation". Since one of the
71 goals of this evaluation is to optimistically return constant
72 values as often as possible, it uses two main short cuts:
74 - If an argument is flowing in through a non-executable edge, it
75 is ignored. This is useful in cases like this:
81 a_11 = PHI (a_9, a_10)
83 If PRED is known to always evaluate to false, then we can
84 assume that a_11 will always take its value from a_10, meaning
85 that instead of consider it VARYING (a_9 and a_10 have
86 different values), we can consider it CONSTANT 100.
88 - If an argument has an UNDEFINED value, then it does not affect
89 the outcome of the meet operation. If a variable V_i has an
90 UNDEFINED value, it means that either its defining statement
91 hasn't been visited yet or V_i has no defining statement, in
92 which case the original symbol 'V' is being used
93 uninitialized. Since 'V' is a local variable, the compiler
94 may assume any initial value for it.
97 After propagation, every variable V_i that ends up with a lattice
98 value of CONSTANT will have the associated constant value in the
99 array CONST_VAL[i].VALUE. That is fed into substitute_and_fold for
100 final substitution and folding.
103 Constant propagation in stores and loads (STORE-CCP)
104 ----------------------------------------------------
106 While CCP has all the logic to propagate constants in GIMPLE
107 registers, it is missing the ability to associate constants with
108 stores and loads (i.e., pointer dereferences, structures and
109 global/aliased variables). We don't keep loads and stores in
110 SSA, but we do build a factored use-def web for them (in the
113 For instance, consider the following code fragment:
132 We should be able to deduce that the predicate 'a.a != B' is always
133 false. To achieve this, we associate constant values to the SSA
134 names in the VDEF operands for each store. Additionally,
135 since we also glob partial loads/stores with the base symbol, we
136 also keep track of the memory reference where the constant value
137 was stored (in the MEM_REF field of PROP_VALUE_T). For instance,
145 In the example above, CCP will associate value '2' with 'a_5', but
146 it would be wrong to replace the load from 'a.b' with '2', because
147 '2' had been stored into a.a.
149 Note that the initial value of virtual operands is VARYING, not
150 UNDEFINED. Consider, for instance global variables:
158 # A_5 = PHI (A_4, A_2);
166 The value of A_2 cannot be assumed to be UNDEFINED, as it may have
167 been defined outside of foo. If we were to assume it UNDEFINED, we
168 would erroneously optimize the above into 'return 3;'.
170 Though STORE-CCP is not too expensive, it does have to do more work
171 than regular CCP, so it is only enabled at -O2. Both regular CCP
172 and STORE-CCP use the exact same algorithm. The only distinction
173 is that when doing STORE-CCP, the boolean variable DO_STORE_CCP is
174 set to true. This affects the evaluation of statements and PHI
179 Constant propagation with conditional branches,
180 Wegman and Zadeck, ACM TOPLAS 13(2):181-210.
182 Building an Optimizing Compiler,
183 Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9.
185 Advanced Compiler Design and Implementation,
186 Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */
190 #include "coretypes.h"
197 #include "basic-block.h"
200 #include "function.h"
201 #include "diagnostic.h"
203 #include "tree-dump.h"
204 #include "tree-flow.h"
205 #include "tree-pass.h"
206 #include "tree-ssa-propagate.h"
207 #include "langhooks.h"
212 /* Possible lattice values. */
221 /* Array of propagated constant values. After propagation,
222 CONST_VAL[I].VALUE holds the constant value for SSA_NAME(I). If
223 the constant is held in an SSA name representing a memory store
224 (i.e., a VDEF), CONST_VAL[I].MEM_REF will contain the actual
225 memory reference used to store (i.e., the LHS of the assignment
227 static prop_value_t *const_val;
229 /* True if we are also propagating constants in stores and loads. */
230 static bool do_store_ccp;
232 /* Dump constant propagation value VAL to file OUTF prefixed by PREFIX. */
235 dump_lattice_value (FILE *outf, const char *prefix, prop_value_t val)
237 switch (val.lattice_val)
240 fprintf (outf, "%sUNINITIALIZED", prefix);
243 fprintf (outf, "%sUNDEFINED", prefix);
246 fprintf (outf, "%sVARYING", prefix);
249 fprintf (outf, "%sCONSTANT ", prefix);
250 print_generic_expr (outf, val.value, dump_flags);
258 /* Print lattice value VAL to stderr. */
260 void debug_lattice_value (prop_value_t val);
263 debug_lattice_value (prop_value_t val)
265 dump_lattice_value (stderr, "", val);
266 fprintf (stderr, "\n");
270 /* The regular is_gimple_min_invariant does a shallow test of the object.
271 It assumes that full gimplification has happened, or will happen on the
272 object. For a value coming from DECL_INITIAL, this is not true, so we
273 have to be more strict ourselves. */
276 ccp_decl_initial_min_invariant (tree t)
278 if (!is_gimple_min_invariant (t))
280 if (TREE_CODE (t) == ADDR_EXPR)
282 /* Inline and unroll is_gimple_addressable. */
285 t = TREE_OPERAND (t, 0);
286 if (is_gimple_id (t))
288 if (!handled_component_p (t))
295 /* If SYM is a constant variable with known value, return the value.
296 NULL_TREE is returned otherwise. */
299 get_symbol_constant_value (tree sym)
301 if (TREE_STATIC (sym)
302 && TREE_READONLY (sym)
304 /* Check if a read-only definition may be overridden at
305 link and run time. */
306 && targetm.binds_local_p (sym))
308 tree val = DECL_INITIAL (sym);
310 && ccp_decl_initial_min_invariant (val))
312 /* Variables declared 'const' without an initializer
313 have zero as the intializer. */
315 && (INTEGRAL_TYPE_P (TREE_TYPE (sym))
316 || SCALAR_FLOAT_TYPE_P (TREE_TYPE (sym))))
317 return fold_convert (TREE_TYPE (sym), integer_zero_node);
323 /* Compute a default value for variable VAR and store it in the
324 CONST_VAL array. The following rules are used to get default
327 1- Global and static variables that are declared constant are
330 2- Any other value is considered UNDEFINED. This is useful when
331 considering PHI nodes. PHI arguments that are undefined do not
332 change the constant value of the PHI node, which allows for more
333 constants to be propagated.
335 3- If SSA_NAME_VALUE is set and it is a constant, its value is
338 4- Variables defined by statements other than assignments and PHI
339 nodes are considered VARYING.
341 5- Initial values of variables that are not GIMPLE registers are
342 considered VARYING. */
345 get_default_value (tree var)
347 tree sym = SSA_NAME_VAR (var);
348 prop_value_t val = { UNINITIALIZED, NULL_TREE, NULL_TREE };
351 if (!do_store_ccp && !is_gimple_reg (var))
353 /* Short circuit for regular CCP. We are not interested in any
354 non-register when DO_STORE_CCP is false. */
355 val.lattice_val = VARYING;
357 else if (SSA_NAME_VALUE (var)
358 && is_gimple_min_invariant (SSA_NAME_VALUE (var)))
360 val.lattice_val = CONSTANT;
361 val.value = SSA_NAME_VALUE (var);
363 else if ((cst_val = get_symbol_constant_value (sym)) != NULL_TREE)
365 /* Globals and static variables declared 'const' take their
367 val.lattice_val = CONSTANT;
373 tree stmt = SSA_NAME_DEF_STMT (var);
375 if (IS_EMPTY_STMT (stmt))
377 /* Variables defined by an empty statement are those used
378 before being initialized. If VAR is a local variable, we
379 can assume initially that it is UNDEFINED, otherwise we must
380 consider it VARYING. */
381 if (is_gimple_reg (sym) && TREE_CODE (sym) != PARM_DECL)
382 val.lattice_val = UNDEFINED;
384 val.lattice_val = VARYING;
386 else if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
387 || TREE_CODE (stmt) == PHI_NODE)
389 /* Any other variable defined by an assignment or a PHI node
390 is considered UNDEFINED. */
391 val.lattice_val = UNDEFINED;
395 /* Otherwise, VAR will never take on a constant value. */
396 val.lattice_val = VARYING;
404 /* Get the constant value associated with variable VAR. */
406 static inline prop_value_t *
409 prop_value_t *val = &const_val[SSA_NAME_VERSION (var)];
411 if (val->lattice_val == UNINITIALIZED)
412 *val = get_default_value (var);
417 /* Sets the value associated with VAR to VARYING. */
420 set_value_varying (tree var)
422 prop_value_t *val = &const_val[SSA_NAME_VERSION (var)];
424 val->lattice_val = VARYING;
425 val->value = NULL_TREE;
426 val->mem_ref = NULL_TREE;
429 /* For float types, modify the value of VAL to make ccp work correctly
430 for non-standard values (-0, NaN):
432 If HONOR_SIGNED_ZEROS is false, and VAL = -0, we canonicalize it to 0.
433 If HONOR_NANS is false, and VAL is NaN, we canonicalize it to UNDEFINED.
434 This is to fix the following problem (see PR 29921): Suppose we have
438 and we set value of y to NaN. This causes value of x to be set to NaN.
439 When we later determine that y is in fact VARYING, fold uses the fact
440 that HONOR_NANS is false, and we try to change the value of x to 0,
441 causing an ICE. With HONOR_NANS being false, the real appearance of
442 NaN would cause undefined behavior, though, so claiming that y (and x)
443 are UNDEFINED initially is correct. */
446 canonicalize_float_value (prop_value_t *val)
448 enum machine_mode mode;
452 if (val->lattice_val != CONSTANT
453 || TREE_CODE (val->value) != REAL_CST)
456 d = TREE_REAL_CST (val->value);
457 type = TREE_TYPE (val->value);
458 mode = TYPE_MODE (type);
460 if (!HONOR_SIGNED_ZEROS (mode)
461 && REAL_VALUE_MINUS_ZERO (d))
463 val->value = build_real (type, dconst0);
467 if (!HONOR_NANS (mode)
468 && REAL_VALUE_ISNAN (d))
470 val->lattice_val = UNDEFINED;
477 /* Set the value for variable VAR to NEW_VAL. Return true if the new
478 value is different from VAR's previous value. */
481 set_lattice_value (tree var, prop_value_t new_val)
483 prop_value_t *old_val = get_value (var);
485 canonicalize_float_value (&new_val);
487 /* Lattice transitions must always be monotonically increasing in
488 value. If *OLD_VAL and NEW_VAL are the same, return false to
489 inform the caller that this was a non-transition. */
491 gcc_assert (old_val->lattice_val < new_val.lattice_val
492 || (old_val->lattice_val == new_val.lattice_val
493 && ((!old_val->value && !new_val.value)
494 || operand_equal_p (old_val->value, new_val.value, 0))
495 && old_val->mem_ref == new_val.mem_ref));
497 if (old_val->lattice_val != new_val.lattice_val)
499 if (dump_file && (dump_flags & TDF_DETAILS))
501 dump_lattice_value (dump_file, "Lattice value changed to ", new_val);
502 fprintf (dump_file, ". Adding SSA edges to worklist.\n");
507 gcc_assert (new_val.lattice_val != UNDEFINED);
515 /* Return the likely CCP lattice value for STMT.
517 If STMT has no operands, then return CONSTANT.
519 Else if undefinedness of operands of STMT cause its value to be
520 undefined, then return UNDEFINED.
522 Else if any operands of STMT are constants, then return CONSTANT.
524 Else return VARYING. */
527 likely_value (tree stmt)
529 bool has_constant_operand, has_undefined_operand, all_undefined_operands;
534 ann = stmt_ann (stmt);
536 /* If the statement has volatile operands, it won't fold to a
538 if (ann->has_volatile_ops)
541 /* If we are not doing store-ccp, statements with loads
542 and/or stores will never fold into a constant. */
544 && !ZERO_SSA_OPERANDS (stmt, SSA_OP_ALL_VIRTUALS))
548 /* A CALL_EXPR is assumed to be varying. NOTE: This may be overly
549 conservative, in the presence of const and pure calls. */
550 if (get_call_expr_in (stmt) != NULL_TREE)
553 /* Anything other than assignments and conditional jumps are not
554 interesting for CCP. */
555 if (TREE_CODE (stmt) != GIMPLE_MODIFY_STMT
556 && !(TREE_CODE (stmt) == RETURN_EXPR && get_rhs (stmt) != NULL_TREE)
557 && TREE_CODE (stmt) != COND_EXPR
558 && TREE_CODE (stmt) != SWITCH_EXPR)
561 if (is_gimple_min_invariant (get_rhs (stmt)))
564 has_constant_operand = false;
565 has_undefined_operand = false;
566 all_undefined_operands = true;
567 FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE | SSA_OP_VUSE)
569 prop_value_t *val = get_value (use);
571 if (val->lattice_val == UNDEFINED)
572 has_undefined_operand = true;
574 all_undefined_operands = false;
576 if (val->lattice_val == CONSTANT)
577 has_constant_operand = true;
580 /* If the operation combines operands like COMPLEX_EXPR make sure to
581 not mark the result UNDEFINED if only one part of the result is
583 if (has_undefined_operand
584 && all_undefined_operands)
586 else if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
587 && has_undefined_operand)
589 switch (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)))
591 /* Unary operators are handled with all_undefined_operands. */
594 case POINTER_PLUS_EXPR:
595 /* Not MIN_EXPR, MAX_EXPR. One VARYING operand may be selected.
596 Not bitwise operators, one VARYING operand may specify the
597 result completely. Not logical operators for the same reason.
598 Not COMPLEX_EXPR as one VARYING operand makes the result partly
599 not UNDEFINED. Not *DIV_EXPR, comparisons and shifts because
600 the undefined operand may be promoted. */
607 /* If there was an UNDEFINED operand but the result may be not UNDEFINED
608 fall back to VARYING even if there were CONSTANT operands. */
609 if (has_undefined_operand)
612 if (has_constant_operand
613 /* We do not consider virtual operands here -- load from read-only
614 memory may have only VARYING virtual operands, but still be
616 || ZERO_SSA_OPERANDS (stmt, SSA_OP_USE))
622 /* Returns true if STMT cannot be constant. */
625 surely_varying_stmt_p (tree stmt)
627 /* If the statement has operands that we cannot handle, it cannot be
629 if (stmt_ann (stmt)->has_volatile_ops)
632 if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_ALL_VIRTUALS))
637 /* We can only handle simple loads and stores. */
638 if (!stmt_makes_single_load (stmt)
639 && !stmt_makes_single_store (stmt))
643 /* If it contains a call, it is varying. */
644 if (get_call_expr_in (stmt) != NULL_TREE)
647 /* Anything other than assignments and conditional jumps are not
648 interesting for CCP. */
649 if (TREE_CODE (stmt) != GIMPLE_MODIFY_STMT
650 && !(TREE_CODE (stmt) == RETURN_EXPR && get_rhs (stmt) != NULL_TREE)
651 && TREE_CODE (stmt) != COND_EXPR
652 && TREE_CODE (stmt) != SWITCH_EXPR)
658 /* Initialize local data structures for CCP. */
661 ccp_initialize (void)
665 const_val = XCNEWVEC (prop_value_t, num_ssa_names);
667 /* Initialize simulation flags for PHI nodes and statements. */
670 block_stmt_iterator i;
672 for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
674 tree stmt = bsi_stmt (i);
675 bool is_varying = surely_varying_stmt_p (stmt);
682 /* If the statement will not produce a constant, mark
683 all its outputs VARYING. */
684 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
687 set_value_varying (def);
691 DONT_SIMULATE_AGAIN (stmt) = is_varying;
695 /* Now process PHI nodes. We never set DONT_SIMULATE_AGAIN on phi node,
696 since we do not know which edges are executable yet, except for
697 phi nodes for virtual operands when we do not do store ccp. */
702 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
704 if (!do_store_ccp && !is_gimple_reg (PHI_RESULT (phi)))
705 DONT_SIMULATE_AGAIN (phi) = true;
707 DONT_SIMULATE_AGAIN (phi) = false;
713 /* Do final substitution of propagated values, cleanup the flowgraph and
714 free allocated storage.
716 Return TRUE when something was optimized. */
721 /* Perform substitutions based on the known constant values. */
722 bool something_changed = substitute_and_fold (const_val, false);
725 return something_changed;;
729 /* Compute the meet operator between *VAL1 and *VAL2. Store the result
732 any M UNDEFINED = any
733 any M VARYING = VARYING
734 Ci M Cj = Ci if (i == j)
735 Ci M Cj = VARYING if (i != j)
739 ccp_lattice_meet (prop_value_t *val1, prop_value_t *val2)
741 if (val1->lattice_val == UNDEFINED)
743 /* UNDEFINED M any = any */
746 else if (val2->lattice_val == UNDEFINED)
748 /* any M UNDEFINED = any
749 Nothing to do. VAL1 already contains the value we want. */
752 else if (val1->lattice_val == VARYING
753 || val2->lattice_val == VARYING)
755 /* any M VARYING = VARYING. */
756 val1->lattice_val = VARYING;
757 val1->value = NULL_TREE;
758 val1->mem_ref = NULL_TREE;
760 else if (val1->lattice_val == CONSTANT
761 && val2->lattice_val == CONSTANT
762 && simple_cst_equal (val1->value, val2->value) == 1
764 || (val1->mem_ref && val2->mem_ref
765 && operand_equal_p (val1->mem_ref, val2->mem_ref, 0))))
767 /* Ci M Cj = Ci if (i == j)
768 Ci M Cj = VARYING if (i != j)
770 If these two values come from memory stores, make sure that
771 they come from the same memory reference. */
772 val1->lattice_val = CONSTANT;
773 val1->value = val1->value;
774 val1->mem_ref = val1->mem_ref;
778 /* Any other combination is VARYING. */
779 val1->lattice_val = VARYING;
780 val1->value = NULL_TREE;
781 val1->mem_ref = NULL_TREE;
786 /* Loop through the PHI_NODE's parameters for BLOCK and compare their
787 lattice values to determine PHI_NODE's lattice value. The value of a
788 PHI node is determined calling ccp_lattice_meet with all the arguments
789 of the PHI node that are incoming via executable edges. */
791 static enum ssa_prop_result
792 ccp_visit_phi_node (tree phi)
795 prop_value_t *old_val, new_val;
797 if (dump_file && (dump_flags & TDF_DETAILS))
799 fprintf (dump_file, "\nVisiting PHI node: ");
800 print_generic_expr (dump_file, phi, dump_flags);
803 old_val = get_value (PHI_RESULT (phi));
804 switch (old_val->lattice_val)
807 return SSA_PROP_VARYING;
814 new_val.lattice_val = UNDEFINED;
815 new_val.value = NULL_TREE;
816 new_val.mem_ref = NULL_TREE;
823 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
825 /* Compute the meet operator over all the PHI arguments flowing
826 through executable edges. */
827 edge e = PHI_ARG_EDGE (phi, i);
829 if (dump_file && (dump_flags & TDF_DETAILS))
832 "\n Argument #%d (%d -> %d %sexecutable)\n",
833 i, e->src->index, e->dest->index,
834 (e->flags & EDGE_EXECUTABLE) ? "" : "not ");
837 /* If the incoming edge is executable, Compute the meet operator for
838 the existing value of the PHI node and the current PHI argument. */
839 if (e->flags & EDGE_EXECUTABLE)
841 tree arg = PHI_ARG_DEF (phi, i);
842 prop_value_t arg_val;
844 if (is_gimple_min_invariant (arg))
846 arg_val.lattice_val = CONSTANT;
848 arg_val.mem_ref = NULL_TREE;
851 arg_val = *(get_value (arg));
853 ccp_lattice_meet (&new_val, &arg_val);
855 if (dump_file && (dump_flags & TDF_DETAILS))
857 fprintf (dump_file, "\t");
858 print_generic_expr (dump_file, arg, dump_flags);
859 dump_lattice_value (dump_file, "\tValue: ", arg_val);
860 fprintf (dump_file, "\n");
863 if (new_val.lattice_val == VARYING)
868 if (dump_file && (dump_flags & TDF_DETAILS))
870 dump_lattice_value (dump_file, "\n PHI node value: ", new_val);
871 fprintf (dump_file, "\n\n");
874 /* Make the transition to the new value. */
875 if (set_lattice_value (PHI_RESULT (phi), new_val))
877 if (new_val.lattice_val == VARYING)
878 return SSA_PROP_VARYING;
880 return SSA_PROP_INTERESTING;
883 return SSA_PROP_NOT_INTERESTING;
887 /* CCP specific front-end to the non-destructive constant folding
890 Attempt to simplify the RHS of STMT knowing that one or more
891 operands are constants.
893 If simplification is possible, return the simplified RHS,
894 otherwise return the original RHS. */
899 tree rhs = get_rhs (stmt);
900 enum tree_code code = TREE_CODE (rhs);
901 enum tree_code_class kind = TREE_CODE_CLASS (code);
902 tree retval = NULL_TREE;
904 if (TREE_CODE (rhs) == SSA_NAME)
906 /* If the RHS is an SSA_NAME, return its known constant value,
908 return get_value (rhs)->value;
910 else if (do_store_ccp && stmt_makes_single_load (stmt))
912 /* If the RHS is a memory load, see if the VUSEs associated with
913 it are a valid constant for that memory load. */
914 prop_value_t *val = get_value_loaded_by (stmt, const_val);
915 if (val && val->mem_ref)
917 if (operand_equal_p (val->mem_ref, rhs, 0))
920 /* If RHS is extracting REALPART_EXPR or IMAGPART_EXPR of a
921 complex type with a known constant value, return it. */
922 if ((TREE_CODE (rhs) == REALPART_EXPR
923 || TREE_CODE (rhs) == IMAGPART_EXPR)
924 && operand_equal_p (val->mem_ref, TREE_OPERAND (rhs, 0), 0))
925 return fold_build1 (TREE_CODE (rhs), TREE_TYPE (rhs), val->value);
930 /* Unary operators. Note that we know the single operand must
931 be a constant. So this should almost always return a
933 if (kind == tcc_unary)
935 /* Handle unary operators which can appear in GIMPLE form. */
936 tree op0 = TREE_OPERAND (rhs, 0);
938 /* Simplify the operand down to a constant. */
939 if (TREE_CODE (op0) == SSA_NAME)
941 prop_value_t *val = get_value (op0);
942 if (val->lattice_val == CONSTANT)
943 op0 = get_value (op0)->value;
946 if ((code == NOP_EXPR || code == CONVERT_EXPR)
947 && useless_type_conversion_p (TREE_TYPE (rhs), TREE_TYPE (op0)))
949 return fold_unary (code, TREE_TYPE (rhs), op0);
952 /* Binary and comparison operators. We know one or both of the
953 operands are constants. */
954 else if (kind == tcc_binary
955 || kind == tcc_comparison
956 || code == TRUTH_AND_EXPR
957 || code == TRUTH_OR_EXPR
958 || code == TRUTH_XOR_EXPR)
960 /* Handle binary and comparison operators that can appear in
962 tree op0 = TREE_OPERAND (rhs, 0);
963 tree op1 = TREE_OPERAND (rhs, 1);
965 /* Simplify the operands down to constants when appropriate. */
966 if (TREE_CODE (op0) == SSA_NAME)
968 prop_value_t *val = get_value (op0);
969 if (val->lattice_val == CONSTANT)
973 if (TREE_CODE (op1) == SSA_NAME)
975 prop_value_t *val = get_value (op1);
976 if (val->lattice_val == CONSTANT)
980 return fold_binary (code, TREE_TYPE (rhs), op0, op1);
983 /* We may be able to fold away calls to builtin functions if their
984 arguments are constants. */
985 else if (code == CALL_EXPR
986 && TREE_CODE (CALL_EXPR_FN (rhs)) == ADDR_EXPR
987 && TREE_CODE (TREE_OPERAND (CALL_EXPR_FN (rhs), 0)) == FUNCTION_DECL
988 && DECL_BUILT_IN (TREE_OPERAND (CALL_EXPR_FN (rhs), 0)))
990 if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_USE))
997 /* Preserve the original values of every operand. */
998 orig = XNEWVEC (tree, NUM_SSA_OPERANDS (stmt, SSA_OP_USE));
999 FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_USE)
1002 /* Substitute operands with their values and try to fold. */
1003 replace_uses_in (stmt, NULL, const_val);
1004 retval = fold_call_expr (rhs, false);
1006 /* Restore operands to their original form. */
1008 FOR_EACH_SSA_USE_OPERAND (var_p, stmt, iter, SSA_OP_USE)
1009 SET_USE (var_p, orig[i++]);
1016 /* If we got a simplified form, see if we need to convert its type. */
1018 return fold_convert (TREE_TYPE (rhs), retval);
1020 /* No simplification was possible. */
1025 /* Return the tree representing the element referenced by T if T is an
1026 ARRAY_REF or COMPONENT_REF into constant aggregates. Return
1027 NULL_TREE otherwise. */
1030 fold_const_aggregate_ref (tree t)
1032 prop_value_t *value;
1033 tree base, ctor, idx, field;
1034 unsigned HOST_WIDE_INT cnt;
1037 switch (TREE_CODE (t))
1040 /* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its
1041 DECL_INITIAL. If BASE is a nested reference into another
1042 ARRAY_REF or COMPONENT_REF, make a recursive call to resolve
1043 the inner reference. */
1044 base = TREE_OPERAND (t, 0);
1045 switch (TREE_CODE (base))
1048 if (!TREE_READONLY (base)
1049 || TREE_CODE (TREE_TYPE (base)) != ARRAY_TYPE
1050 || !targetm.binds_local_p (base))
1053 ctor = DECL_INITIAL (base);
1058 ctor = fold_const_aggregate_ref (base);
1065 if (ctor == NULL_TREE
1066 || (TREE_CODE (ctor) != CONSTRUCTOR
1067 && TREE_CODE (ctor) != STRING_CST)
1068 || !TREE_STATIC (ctor))
1071 /* Get the index. If we have an SSA_NAME, try to resolve it
1072 with the current lattice value for the SSA_NAME. */
1073 idx = TREE_OPERAND (t, 1);
1074 switch (TREE_CODE (idx))
1077 if ((value = get_value (idx))
1078 && value->lattice_val == CONSTANT
1079 && TREE_CODE (value->value) == INTEGER_CST)
1092 /* Fold read from constant string. */
1093 if (TREE_CODE (ctor) == STRING_CST)
1095 if ((TYPE_MODE (TREE_TYPE (t))
1096 == TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor))))
1097 && (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor))))
1099 && GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor)))) == 1
1100 && compare_tree_int (idx, TREE_STRING_LENGTH (ctor)) < 0)
1101 return build_int_cst_type (TREE_TYPE (t),
1102 (TREE_STRING_POINTER (ctor)
1103 [TREE_INT_CST_LOW (idx)]));
1107 /* Whoo-hoo! I'll fold ya baby. Yeah! */
1108 FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval)
1109 if (tree_int_cst_equal (cfield, idx))
1114 /* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its
1115 DECL_INITIAL. If BASE is a nested reference into another
1116 ARRAY_REF or COMPONENT_REF, make a recursive call to resolve
1117 the inner reference. */
1118 base = TREE_OPERAND (t, 0);
1119 switch (TREE_CODE (base))
1122 if (!TREE_READONLY (base)
1123 || TREE_CODE (TREE_TYPE (base)) != RECORD_TYPE
1124 || !targetm.binds_local_p (base))
1127 ctor = DECL_INITIAL (base);
1132 ctor = fold_const_aggregate_ref (base);
1139 if (ctor == NULL_TREE
1140 || TREE_CODE (ctor) != CONSTRUCTOR
1141 || !TREE_STATIC (ctor))
1144 field = TREE_OPERAND (t, 1);
1146 FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval)
1148 /* FIXME: Handle bit-fields. */
1149 && ! DECL_BIT_FIELD (cfield))
1156 tree c = fold_const_aggregate_ref (TREE_OPERAND (t, 0));
1157 if (c && TREE_CODE (c) == COMPLEX_CST)
1158 return fold_build1 (TREE_CODE (t), TREE_TYPE (t), c);
1169 /* Evaluate statement STMT. */
1172 evaluate_stmt (tree stmt)
1175 tree simplified = NULL_TREE;
1176 ccp_lattice_t likelyvalue = likely_value (stmt);
1179 val.mem_ref = NULL_TREE;
1181 fold_defer_overflow_warnings ();
1183 /* If the statement is likely to have a CONSTANT result, then try
1184 to fold the statement to determine the constant value. */
1185 if (likelyvalue == CONSTANT)
1186 simplified = ccp_fold (stmt);
1187 /* If the statement is likely to have a VARYING result, then do not
1188 bother folding the statement. */
1189 if (likelyvalue == VARYING)
1190 simplified = get_rhs (stmt);
1191 /* If the statement is an ARRAY_REF or COMPONENT_REF into constant
1192 aggregates, extract the referenced constant. Otherwise the
1193 statement is likely to have an UNDEFINED value, and there will be
1194 nothing to do. Note that fold_const_aggregate_ref returns
1195 NULL_TREE if the first case does not match. */
1196 else if (!simplified)
1197 simplified = fold_const_aggregate_ref (get_rhs (stmt));
1199 is_constant = simplified && is_gimple_min_invariant (simplified);
1201 fold_undefer_overflow_warnings (is_constant, stmt, 0);
1205 /* The statement produced a constant value. */
1206 val.lattice_val = CONSTANT;
1207 val.value = simplified;
1211 /* The statement produced a nonconstant value. If the statement
1212 had UNDEFINED operands, then the result of the statement
1213 should be UNDEFINED. Otherwise, the statement is VARYING. */
1214 if (likelyvalue == UNDEFINED)
1215 val.lattice_val = likelyvalue;
1217 val.lattice_val = VARYING;
1219 val.value = NULL_TREE;
1226 /* Visit the assignment statement STMT. Set the value of its LHS to the
1227 value computed by the RHS and store LHS in *OUTPUT_P. If STMT
1228 creates virtual definitions, set the value of each new name to that
1229 of the RHS (if we can derive a constant out of the RHS). */
1231 static enum ssa_prop_result
1232 visit_assignment (tree stmt, tree *output_p)
1236 enum ssa_prop_result retval;
1238 lhs = GIMPLE_STMT_OPERAND (stmt, 0);
1239 rhs = GIMPLE_STMT_OPERAND (stmt, 1);
1241 if (TREE_CODE (rhs) == SSA_NAME)
1243 /* For a simple copy operation, we copy the lattice values. */
1244 prop_value_t *nval = get_value (rhs);
1247 else if (do_store_ccp && stmt_makes_single_load (stmt))
1249 /* Same as above, but the RHS is not a gimple register and yet
1250 has a known VUSE. If STMT is loading from the same memory
1251 location that created the SSA_NAMEs for the virtual operands,
1252 we can propagate the value on the RHS. */
1253 prop_value_t *nval = get_value_loaded_by (stmt, const_val);
1257 && operand_equal_p (nval->mem_ref, rhs, 0))
1260 val = evaluate_stmt (stmt);
1263 /* Evaluate the statement. */
1264 val = evaluate_stmt (stmt);
1266 /* If the original LHS was a VIEW_CONVERT_EXPR, modify the constant
1267 value to be a VIEW_CONVERT_EXPR of the old constant value.
1269 ??? Also, if this was a definition of a bitfield, we need to widen
1270 the constant value into the type of the destination variable. This
1271 should not be necessary if GCC represented bitfields properly. */
1273 tree orig_lhs = GIMPLE_STMT_OPERAND (stmt, 0);
1275 if (TREE_CODE (orig_lhs) == VIEW_CONVERT_EXPR
1276 && val.lattice_val == CONSTANT)
1278 tree w = fold_unary (VIEW_CONVERT_EXPR,
1279 TREE_TYPE (TREE_OPERAND (orig_lhs, 0)),
1282 orig_lhs = TREE_OPERAND (orig_lhs, 0);
1283 if (w && is_gimple_min_invariant (w))
1287 val.lattice_val = VARYING;
1292 if (val.lattice_val == CONSTANT
1293 && TREE_CODE (orig_lhs) == COMPONENT_REF
1294 && DECL_BIT_FIELD (TREE_OPERAND (orig_lhs, 1)))
1296 tree w = widen_bitfield (val.value, TREE_OPERAND (orig_lhs, 1),
1299 if (w && is_gimple_min_invariant (w))
1303 val.lattice_val = VARYING;
1304 val.value = NULL_TREE;
1305 val.mem_ref = NULL_TREE;
1310 retval = SSA_PROP_NOT_INTERESTING;
1312 /* Set the lattice value of the statement's output. */
1313 if (TREE_CODE (lhs) == SSA_NAME)
1315 /* If STMT is an assignment to an SSA_NAME, we only have one
1317 if (set_lattice_value (lhs, val))
1320 if (val.lattice_val == VARYING)
1321 retval = SSA_PROP_VARYING;
1323 retval = SSA_PROP_INTERESTING;
1326 else if (do_store_ccp && stmt_makes_single_store (stmt))
1328 /* Otherwise, set the names in VDEF operands to the new
1329 constant value and mark the LHS as the memory reference
1330 associated with VAL. */
1335 /* Mark VAL as stored in the LHS of this assignment. */
1336 if (val.lattice_val == CONSTANT)
1339 /* Set the value of every VDEF to VAL. */
1341 FOR_EACH_SSA_TREE_OPERAND (vdef, stmt, i, SSA_OP_VIRTUAL_DEFS)
1343 /* See PR 29801. We may have VDEFs for read-only variables
1344 (see the handling of unmodifiable variables in
1345 add_virtual_operand); do not attempt to change their value. */
1346 if (get_symbol_constant_value (SSA_NAME_VAR (vdef)) != NULL_TREE)
1349 changed |= set_lattice_value (vdef, val);
1352 /* Note that for propagation purposes, we are only interested in
1353 visiting statements that load the exact same memory reference
1354 stored here. Those statements will have the exact same list
1355 of virtual uses, so it is enough to set the output of this
1356 statement to be its first virtual definition. */
1357 *output_p = first_vdef (stmt);
1360 if (val.lattice_val == VARYING)
1361 retval = SSA_PROP_VARYING;
1363 retval = SSA_PROP_INTERESTING;
1371 /* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING
1372 if it can determine which edge will be taken. Otherwise, return
1373 SSA_PROP_VARYING. */
1375 static enum ssa_prop_result
1376 visit_cond_stmt (tree stmt, edge *taken_edge_p)
1381 block = bb_for_stmt (stmt);
1382 val = evaluate_stmt (stmt);
1384 /* Find which edge out of the conditional block will be taken and add it
1385 to the worklist. If no single edge can be determined statically,
1386 return SSA_PROP_VARYING to feed all the outgoing edges to the
1387 propagation engine. */
1388 *taken_edge_p = val.value ? find_taken_edge (block, val.value) : 0;
1390 return SSA_PROP_INTERESTING;
1392 return SSA_PROP_VARYING;
1396 /* Evaluate statement STMT. If the statement produces an output value and
1397 its evaluation changes the lattice value of its output, return
1398 SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the
1401 If STMT is a conditional branch and we can determine its truth
1402 value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying
1403 value, return SSA_PROP_VARYING. */
1405 static enum ssa_prop_result
1406 ccp_visit_stmt (tree stmt, edge *taken_edge_p, tree *output_p)
1411 if (dump_file && (dump_flags & TDF_DETAILS))
1413 fprintf (dump_file, "\nVisiting statement:\n");
1414 print_generic_stmt (dump_file, stmt, dump_flags);
1415 fprintf (dump_file, "\n");
1418 if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
1420 /* If the statement is an assignment that produces a single
1421 output value, evaluate its RHS to see if the lattice value of
1422 its output has changed. */
1423 return visit_assignment (stmt, output_p);
1425 else if (TREE_CODE (stmt) == COND_EXPR || TREE_CODE (stmt) == SWITCH_EXPR)
1427 /* If STMT is a conditional branch, see if we can determine
1428 which branch will be taken. */
1429 return visit_cond_stmt (stmt, taken_edge_p);
1432 /* Any other kind of statement is not interesting for constant
1433 propagation and, therefore, not worth simulating. */
1434 if (dump_file && (dump_flags & TDF_DETAILS))
1435 fprintf (dump_file, "No interesting values produced. Marked VARYING.\n");
1437 /* Definitions made by statements other than assignments to
1438 SSA_NAMEs represent unknown modifications to their outputs.
1439 Mark them VARYING. */
1440 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
1442 prop_value_t v = { VARYING, NULL_TREE, NULL_TREE };
1443 set_lattice_value (def, v);
1446 return SSA_PROP_VARYING;
1450 /* Main entry point for SSA Conditional Constant Propagation. */
1453 execute_ssa_ccp (bool store_ccp)
1455 do_store_ccp = store_ccp;
1457 ssa_propagate (ccp_visit_stmt, ccp_visit_phi_node);
1458 if (ccp_finalize ())
1459 return (TODO_cleanup_cfg | TODO_update_ssa | TODO_remove_unused_locals);
1468 return execute_ssa_ccp (false);
1475 return flag_tree_ccp != 0;
1479 struct tree_opt_pass pass_ccp =
1482 gate_ccp, /* gate */
1483 do_ssa_ccp, /* execute */
1486 0, /* static_pass_number */
1487 TV_TREE_CCP, /* tv_id */
1488 PROP_cfg | PROP_ssa, /* properties_required */
1489 0, /* properties_provided */
1490 0, /* properties_destroyed */
1491 0, /* todo_flags_start */
1492 TODO_dump_func | TODO_verify_ssa
1493 | TODO_verify_stmts | TODO_ggc_collect,/* todo_flags_finish */
1499 do_ssa_store_ccp (void)
1501 /* If STORE-CCP is not enabled, we just run regular CCP. */
1502 return execute_ssa_ccp (flag_tree_store_ccp != 0);
1506 gate_store_ccp (void)
1508 /* STORE-CCP is enabled only with -ftree-store-ccp, but when
1509 -fno-tree-store-ccp is specified, we should run regular CCP.
1510 That's why the pass is enabled with either flag. */
1511 return flag_tree_store_ccp != 0 || flag_tree_ccp != 0;
1515 struct tree_opt_pass pass_store_ccp =
1517 "store_ccp", /* name */
1518 gate_store_ccp, /* gate */
1519 do_ssa_store_ccp, /* execute */
1522 0, /* static_pass_number */
1523 TV_TREE_STORE_CCP, /* tv_id */
1524 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
1525 0, /* properties_provided */
1526 0, /* properties_destroyed */
1527 0, /* todo_flags_start */
1528 TODO_dump_func | TODO_verify_ssa
1529 | TODO_verify_stmts | TODO_ggc_collect,/* todo_flags_finish */
1533 /* Given a constant value VAL for bitfield FIELD, and a destination
1534 variable VAR, return VAL appropriately widened to fit into VAR. If
1535 FIELD is wider than HOST_WIDE_INT, NULL is returned. */
1538 widen_bitfield (tree val, tree field, tree var)
1540 unsigned HOST_WIDE_INT var_size, field_size;
1542 unsigned HOST_WIDE_INT mask;
1545 /* We can only do this if the size of the type and field and VAL are
1546 all constants representable in HOST_WIDE_INT. */
1547 if (!host_integerp (TYPE_SIZE (TREE_TYPE (var)), 1)
1548 || !host_integerp (DECL_SIZE (field), 1)
1549 || !host_integerp (val, 0))
1552 var_size = tree_low_cst (TYPE_SIZE (TREE_TYPE (var)), 1);
1553 field_size = tree_low_cst (DECL_SIZE (field), 1);
1555 /* Give up if either the bitfield or the variable are too wide. */
1556 if (field_size > HOST_BITS_PER_WIDE_INT || var_size > HOST_BITS_PER_WIDE_INT)
1559 gcc_assert (var_size >= field_size);
1561 /* If the sign bit of the value is not set or the field's type is unsigned,
1562 just mask off the high order bits of the value. */
1563 if (DECL_UNSIGNED (field)
1564 || !(tree_low_cst (val, 0) & (((HOST_WIDE_INT)1) << (field_size - 1))))
1566 /* Zero extension. Build a mask with the lower 'field_size' bits
1567 set and a BIT_AND_EXPR node to clear the high order bits of
1569 for (i = 0, mask = 0; i < field_size; i++)
1570 mask |= ((HOST_WIDE_INT) 1) << i;
1572 wide_val = fold_build2 (BIT_AND_EXPR, TREE_TYPE (var), val,
1573 build_int_cst (TREE_TYPE (var), mask));
1577 /* Sign extension. Create a mask with the upper 'field_size'
1578 bits set and a BIT_IOR_EXPR to set the high order bits of the
1580 for (i = 0, mask = 0; i < (var_size - field_size); i++)
1581 mask |= ((HOST_WIDE_INT) 1) << (var_size - i - 1);
1583 wide_val = fold_build2 (BIT_IOR_EXPR, TREE_TYPE (var), val,
1584 build_int_cst (TREE_TYPE (var), mask));
1591 /* A subroutine of fold_stmt_r. Attempts to fold *(A+O) to A[X].
1592 BASE is an array type. OFFSET is a byte displacement. ORIG_TYPE
1593 is the desired result type. */
1596 maybe_fold_offset_to_array_ref (tree base, tree offset, tree orig_type,
1597 bool allow_negative_idx)
1599 tree min_idx, idx, idx_type, elt_offset = integer_zero_node;
1600 tree array_type, elt_type, elt_size;
1603 /* If BASE is an ARRAY_REF, we can pick up another offset (this time
1604 measured in units of the size of elements type) from that ARRAY_REF).
1605 We can't do anything if either is variable.
1607 The case we handle here is *(&A[N]+O). */
1608 if (TREE_CODE (base) == ARRAY_REF)
1610 tree low_bound = array_ref_low_bound (base);
1612 elt_offset = TREE_OPERAND (base, 1);
1613 if (TREE_CODE (low_bound) != INTEGER_CST
1614 || TREE_CODE (elt_offset) != INTEGER_CST)
1617 elt_offset = int_const_binop (MINUS_EXPR, elt_offset, low_bound, 0);
1618 base = TREE_OPERAND (base, 0);
1621 /* Ignore stupid user tricks of indexing non-array variables. */
1622 array_type = TREE_TYPE (base);
1623 if (TREE_CODE (array_type) != ARRAY_TYPE)
1625 elt_type = TREE_TYPE (array_type);
1626 if (!useless_type_conversion_p (orig_type, elt_type))
1629 /* Use signed size type for intermediate computation on the index. */
1630 idx_type = signed_type_for (size_type_node);
1632 /* If OFFSET and ELT_OFFSET are zero, we don't care about the size of the
1633 element type (so we can use the alignment if it's not constant).
1634 Otherwise, compute the offset as an index by using a division. If the
1635 division isn't exact, then don't do anything. */
1636 elt_size = TYPE_SIZE_UNIT (elt_type);
1639 if (integer_zerop (offset))
1641 if (TREE_CODE (elt_size) != INTEGER_CST)
1642 elt_size = size_int (TYPE_ALIGN (elt_type));
1644 idx = build_int_cst (idx_type, 0);
1648 unsigned HOST_WIDE_INT lquo, lrem;
1649 HOST_WIDE_INT hquo, hrem;
1652 /* The final array offset should be signed, so we need
1653 to sign-extend the (possibly pointer) offset here
1654 and use signed division. */
1655 soffset = double_int_sext (tree_to_double_int (offset),
1656 TYPE_PRECISION (TREE_TYPE (offset)));
1657 if (TREE_CODE (elt_size) != INTEGER_CST
1658 || div_and_round_double (TRUNC_DIV_EXPR, 0,
1659 soffset.low, soffset.high,
1660 TREE_INT_CST_LOW (elt_size),
1661 TREE_INT_CST_HIGH (elt_size),
1662 &lquo, &hquo, &lrem, &hrem)
1666 idx = build_int_cst_wide (idx_type, lquo, hquo);
1669 /* Assume the low bound is zero. If there is a domain type, get the
1670 low bound, if any, convert the index into that type, and add the
1672 min_idx = build_int_cst (idx_type, 0);
1673 domain_type = TYPE_DOMAIN (array_type);
1676 idx_type = domain_type;
1677 if (TYPE_MIN_VALUE (idx_type))
1678 min_idx = TYPE_MIN_VALUE (idx_type);
1680 min_idx = fold_convert (idx_type, min_idx);
1682 if (TREE_CODE (min_idx) != INTEGER_CST)
1685 elt_offset = fold_convert (idx_type, elt_offset);
1688 if (!integer_zerop (min_idx))
1689 idx = int_const_binop (PLUS_EXPR, idx, min_idx, 0);
1690 if (!integer_zerop (elt_offset))
1691 idx = int_const_binop (PLUS_EXPR, idx, elt_offset, 0);
1693 /* Make sure to possibly truncate late after offsetting. */
1694 idx = fold_convert (idx_type, idx);
1696 /* We don't want to construct access past array bounds. For example
1699 should not be simplified into (*c)[14] or tree-vrp will
1700 give false warnings. The same is true for
1701 struct A { long x; char d[0]; } *a;
1703 which should be not folded to &a->d[-8]. */
1705 && TYPE_MAX_VALUE (domain_type)
1706 && TREE_CODE (TYPE_MAX_VALUE (domain_type)) == INTEGER_CST)
1708 tree up_bound = TYPE_MAX_VALUE (domain_type);
1710 if (tree_int_cst_lt (up_bound, idx)
1711 /* Accesses after the end of arrays of size 0 (gcc
1712 extension) and 1 are likely intentional ("struct
1714 && compare_tree_int (up_bound, 1) > 0)
1718 && TYPE_MIN_VALUE (domain_type))
1720 if (!allow_negative_idx
1721 && TREE_CODE (TYPE_MIN_VALUE (domain_type)) == INTEGER_CST
1722 && tree_int_cst_lt (idx, TYPE_MIN_VALUE (domain_type)))
1725 else if (!allow_negative_idx
1726 && compare_tree_int (idx, 0) < 0)
1729 return build4 (ARRAY_REF, elt_type, base, idx, NULL_TREE, NULL_TREE);
1733 /* Attempt to fold *(S+O) to S.X.
1734 BASE is a record type. OFFSET is a byte displacement. ORIG_TYPE
1735 is the desired result type. */
1738 maybe_fold_offset_to_component_ref (tree record_type, tree base, tree offset,
1739 tree orig_type, bool base_is_ptr)
1741 tree f, t, field_type, tail_array_field, field_offset;
1745 if (TREE_CODE (record_type) != RECORD_TYPE
1746 && TREE_CODE (record_type) != UNION_TYPE
1747 && TREE_CODE (record_type) != QUAL_UNION_TYPE)
1750 /* Short-circuit silly cases. */
1751 if (useless_type_conversion_p (record_type, orig_type))
1754 tail_array_field = NULL_TREE;
1755 for (f = TYPE_FIELDS (record_type); f ; f = TREE_CHAIN (f))
1759 if (TREE_CODE (f) != FIELD_DECL)
1761 if (DECL_BIT_FIELD (f))
1764 if (!DECL_FIELD_OFFSET (f))
1766 field_offset = byte_position (f);
1767 if (TREE_CODE (field_offset) != INTEGER_CST)
1770 /* ??? Java creates "interesting" fields for representing base classes.
1771 They have no name, and have no context. With no context, we get into
1772 trouble with nonoverlapping_component_refs_p. Skip them. */
1773 if (!DECL_FIELD_CONTEXT (f))
1776 /* The previous array field isn't at the end. */
1777 tail_array_field = NULL_TREE;
1779 /* Check to see if this offset overlaps with the field. */
1780 cmp = tree_int_cst_compare (field_offset, offset);
1784 field_type = TREE_TYPE (f);
1786 /* Here we exactly match the offset being checked. If the types match,
1787 then we can return that field. */
1789 && useless_type_conversion_p (orig_type, field_type))
1792 base = build1 (INDIRECT_REF, record_type, base);
1793 t = build3 (COMPONENT_REF, field_type, base, f, NULL_TREE);
1797 /* Don't care about offsets into the middle of scalars. */
1798 if (!AGGREGATE_TYPE_P (field_type))
1801 /* Check for array at the end of the struct. This is often
1802 used as for flexible array members. We should be able to
1803 turn this into an array access anyway. */
1804 if (TREE_CODE (field_type) == ARRAY_TYPE)
1805 tail_array_field = f;
1807 /* Check the end of the field against the offset. */
1808 if (!DECL_SIZE_UNIT (f)
1809 || TREE_CODE (DECL_SIZE_UNIT (f)) != INTEGER_CST)
1811 t = int_const_binop (MINUS_EXPR, offset, field_offset, 1);
1812 if (!tree_int_cst_lt (t, DECL_SIZE_UNIT (f)))
1815 /* If we matched, then set offset to the displacement into
1818 new_base = build1 (INDIRECT_REF, record_type, base);
1821 new_base = build3 (COMPONENT_REF, field_type, new_base, f, NULL_TREE);
1823 /* Recurse to possibly find the match. */
1824 ret = maybe_fold_offset_to_array_ref (new_base, t, orig_type,
1825 f == TYPE_FIELDS (record_type));
1828 ret = maybe_fold_offset_to_component_ref (field_type, new_base, t,
1834 if (!tail_array_field)
1837 f = tail_array_field;
1838 field_type = TREE_TYPE (f);
1839 offset = int_const_binop (MINUS_EXPR, offset, byte_position (f), 1);
1841 /* If we get here, we've got an aggregate field, and a possibly
1842 nonzero offset into them. Recurse and hope for a valid match. */
1844 base = build1 (INDIRECT_REF, record_type, base);
1845 base = build3 (COMPONENT_REF, field_type, base, f, NULL_TREE);
1847 t = maybe_fold_offset_to_array_ref (base, offset, orig_type,
1848 f == TYPE_FIELDS (record_type));
1851 return maybe_fold_offset_to_component_ref (field_type, base, offset,
1855 /* Attempt to express (ORIG_TYPE)BASE+OFFSET as BASE->field_of_orig_type
1856 or BASE[index] or by combination of those.
1858 Before attempting the conversion strip off existing ADDR_EXPRs and
1859 handled component refs. */
1862 maybe_fold_offset_to_reference (tree base, tree offset, tree orig_type)
1866 bool base_is_ptr = true;
1869 if (TREE_CODE (base) == ADDR_EXPR)
1871 base_is_ptr = false;
1873 base = TREE_OPERAND (base, 0);
1875 /* Handle case where existing COMPONENT_REF pick e.g. wrong field of union,
1876 so it needs to be removed and new COMPONENT_REF constructed.
1877 The wrong COMPONENT_REF are often constructed by folding the
1878 (type *)&object within the expression (type *)&object+offset */
1879 if (handled_component_p (base) && 0)
1881 HOST_WIDE_INT sub_offset, size, maxsize;
1883 newbase = get_ref_base_and_extent (base, &sub_offset,
1885 gcc_assert (newbase);
1886 gcc_assert (!(sub_offset & (BITS_PER_UNIT - 1)));
1887 if (size == maxsize)
1891 offset = int_const_binop (PLUS_EXPR, offset,
1892 build_int_cst (TREE_TYPE (offset),
1893 sub_offset / BITS_PER_UNIT), 1);
1896 if (useless_type_conversion_p (orig_type, TREE_TYPE (base))
1897 && integer_zerop (offset))
1899 type = TREE_TYPE (base);
1904 if (!POINTER_TYPE_P (TREE_TYPE (base)))
1906 type = TREE_TYPE (TREE_TYPE (base));
1908 ret = maybe_fold_offset_to_component_ref (type, base, offset,
1909 orig_type, base_is_ptr);
1913 base = build1 (INDIRECT_REF, type, base);
1914 ret = maybe_fold_offset_to_array_ref (base, offset, orig_type, true);
1919 /* A subroutine of fold_stmt_r. Attempt to simplify *(BASE+OFFSET).
1920 Return the simplified expression, or NULL if nothing could be done. */
1923 maybe_fold_stmt_indirect (tree expr, tree base, tree offset)
1926 bool volatile_p = TREE_THIS_VOLATILE (expr);
1928 /* We may well have constructed a double-nested PLUS_EXPR via multiple
1929 substitutions. Fold that down to one. Remove NON_LVALUE_EXPRs that
1930 are sometimes added. */
1932 STRIP_TYPE_NOPS (base);
1933 TREE_OPERAND (expr, 0) = base;
1935 /* One possibility is that the address reduces to a string constant. */
1936 t = fold_read_from_constant_string (expr);
1940 /* Add in any offset from a POINTER_PLUS_EXPR. */
1941 if (TREE_CODE (base) == POINTER_PLUS_EXPR)
1945 offset2 = TREE_OPERAND (base, 1);
1946 if (TREE_CODE (offset2) != INTEGER_CST)
1948 base = TREE_OPERAND (base, 0);
1950 offset = fold_convert (sizetype,
1951 int_const_binop (PLUS_EXPR, offset, offset2, 1));
1954 if (TREE_CODE (base) == ADDR_EXPR)
1956 tree base_addr = base;
1958 /* Strip the ADDR_EXPR. */
1959 base = TREE_OPERAND (base, 0);
1961 /* Fold away CONST_DECL to its value, if the type is scalar. */
1962 if (TREE_CODE (base) == CONST_DECL
1963 && ccp_decl_initial_min_invariant (DECL_INITIAL (base)))
1964 return DECL_INITIAL (base);
1966 /* Try folding *(&B+O) to B.X. */
1967 t = maybe_fold_offset_to_reference (base_addr, offset,
1971 TREE_THIS_VOLATILE (t) = volatile_p;
1977 /* We can get here for out-of-range string constant accesses,
1978 such as "_"[3]. Bail out of the entire substitution search
1979 and arrange for the entire statement to be replaced by a
1980 call to __builtin_trap. In all likelihood this will all be
1981 constant-folded away, but in the meantime we can't leave with
1982 something that get_expr_operands can't understand. */
1986 if (TREE_CODE (t) == ADDR_EXPR
1987 && TREE_CODE (TREE_OPERAND (t, 0)) == STRING_CST)
1989 /* FIXME: Except that this causes problems elsewhere with dead
1990 code not being deleted, and we die in the rtl expanders
1991 because we failed to remove some ssa_name. In the meantime,
1992 just return zero. */
1993 /* FIXME2: This condition should be signaled by
1994 fold_read_from_constant_string directly, rather than
1995 re-checking for it here. */
1996 return integer_zero_node;
1999 /* Try folding *(B+O) to B->X. Still an improvement. */
2000 if (POINTER_TYPE_P (TREE_TYPE (base)))
2002 t = maybe_fold_offset_to_reference (base, offset,
2009 /* Otherwise we had an offset that we could not simplify. */
2014 /* A subroutine of fold_stmt_r. EXPR is a POINTER_PLUS_EXPR.
2016 A quaint feature extant in our address arithmetic is that there
2017 can be hidden type changes here. The type of the result need
2018 not be the same as the type of the input pointer.
2020 What we're after here is an expression of the form
2021 (T *)(&array + const)
2022 where the cast doesn't actually exist, but is implicit in the
2023 type of the POINTER_PLUS_EXPR. We'd like to turn this into
2025 which may be able to propagate further. */
2028 maybe_fold_stmt_addition (tree expr)
2030 tree op0 = TREE_OPERAND (expr, 0);
2031 tree op1 = TREE_OPERAND (expr, 1);
2032 tree ptr_type = TREE_TYPE (expr);
2036 gcc_assert (TREE_CODE (expr) == POINTER_PLUS_EXPR);
2038 /* It had better be a constant. */
2039 if (TREE_CODE (op1) != INTEGER_CST)
2041 /* The first operand should be an ADDR_EXPR. */
2042 if (TREE_CODE (op0) != ADDR_EXPR)
2044 op0 = TREE_OPERAND (op0, 0);
2046 /* If the first operand is an ARRAY_REF, expand it so that we can fold
2047 the offset into it. */
2048 while (TREE_CODE (op0) == ARRAY_REF)
2050 tree array_obj = TREE_OPERAND (op0, 0);
2051 tree array_idx = TREE_OPERAND (op0, 1);
2052 tree elt_type = TREE_TYPE (op0);
2053 tree elt_size = TYPE_SIZE_UNIT (elt_type);
2056 if (TREE_CODE (array_idx) != INTEGER_CST)
2058 if (TREE_CODE (elt_size) != INTEGER_CST)
2061 /* Un-bias the index by the min index of the array type. */
2062 min_idx = TYPE_DOMAIN (TREE_TYPE (array_obj));
2065 min_idx = TYPE_MIN_VALUE (min_idx);
2068 if (TREE_CODE (min_idx) != INTEGER_CST)
2071 array_idx = fold_convert (TREE_TYPE (min_idx), array_idx);
2072 if (!integer_zerop (min_idx))
2073 array_idx = int_const_binop (MINUS_EXPR, array_idx,
2078 /* Convert the index to a byte offset. */
2079 array_idx = fold_convert (sizetype, array_idx);
2080 array_idx = int_const_binop (MULT_EXPR, array_idx, elt_size, 0);
2082 /* Update the operands for the next round, or for folding. */
2083 op1 = int_const_binop (PLUS_EXPR,
2088 ptd_type = TREE_TYPE (ptr_type);
2090 /* At which point we can try some of the same things as for indirects. */
2091 t = maybe_fold_offset_to_array_ref (op0, op1, ptd_type, true);
2093 t = maybe_fold_offset_to_component_ref (TREE_TYPE (op0), op0, op1,
2096 t = build1 (ADDR_EXPR, ptr_type, t);
2101 /* For passing state through walk_tree into fold_stmt_r and its
2104 struct fold_stmt_r_data
2108 bool *inside_addr_expr_p;
2111 /* Subroutine of fold_stmt called via walk_tree. We perform several
2112 simplifications of EXPR_P, mostly having to do with pointer arithmetic. */
2115 fold_stmt_r (tree *expr_p, int *walk_subtrees, void *data)
2117 struct fold_stmt_r_data *fold_stmt_r_data = (struct fold_stmt_r_data *) data;
2118 bool *inside_addr_expr_p = fold_stmt_r_data->inside_addr_expr_p;
2119 bool *changed_p = fold_stmt_r_data->changed_p;
2120 tree expr = *expr_p, t;
2121 bool volatile_p = TREE_THIS_VOLATILE (expr);
2123 /* ??? It'd be nice if walk_tree had a pre-order option. */
2124 switch (TREE_CODE (expr))
2127 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
2132 t = maybe_fold_stmt_indirect (expr, TREE_OPERAND (expr, 0),
2137 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
2142 if (POINTER_TYPE_P (TREE_TYPE (expr))
2143 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (expr, 0)))
2144 && (t = maybe_fold_offset_to_reference
2145 (TREE_OPERAND (expr, 0),
2147 TREE_TYPE (TREE_TYPE (expr)))))
2149 tree ptr_type = build_pointer_type (TREE_TYPE (t));
2150 if (!useless_type_conversion_p (TREE_TYPE (expr), ptr_type))
2152 t = build_fold_addr_expr_with_type (t, ptr_type);
2156 /* ??? Could handle more ARRAY_REFs here, as a variant of INDIRECT_REF.
2157 We'd only want to bother decomposing an existing ARRAY_REF if
2158 the base array is found to have another offset contained within.
2159 Otherwise we'd be wasting time. */
2161 /* If we are not processing expressions found within an
2162 ADDR_EXPR, then we can fold constant array references. */
2163 if (!*inside_addr_expr_p)
2164 t = fold_read_from_constant_string (expr);
2170 *inside_addr_expr_p = true;
2171 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
2172 *inside_addr_expr_p = false;
2177 /* Set TREE_INVARIANT properly so that the value is properly
2178 considered constant, and so gets propagated as expected. */
2180 recompute_tree_invariant_for_addr_expr (expr);
2183 case POINTER_PLUS_EXPR:
2184 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
2187 t = walk_tree (&TREE_OPERAND (expr, 1), fold_stmt_r, data, NULL);
2192 t = maybe_fold_stmt_addition (expr);
2196 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
2201 /* Make sure the FIELD_DECL is actually a field in the type on the lhs.
2202 We've already checked that the records are compatible, so we should
2203 come up with a set of compatible fields. */
2205 tree expr_record = TREE_TYPE (TREE_OPERAND (expr, 0));
2206 tree expr_field = TREE_OPERAND (expr, 1);
2208 if (DECL_FIELD_CONTEXT (expr_field) != TYPE_MAIN_VARIANT (expr_record))
2210 expr_field = find_compatible_field (expr_record, expr_field);
2211 TREE_OPERAND (expr, 1) = expr_field;
2216 case TARGET_MEM_REF:
2217 t = maybe_fold_tmr (expr);
2221 if (COMPARISON_CLASS_P (TREE_OPERAND (expr, 0)))
2223 tree op0 = TREE_OPERAND (expr, 0);
2227 fold_defer_overflow_warnings ();
2228 tem = fold_binary (TREE_CODE (op0), TREE_TYPE (op0),
2229 TREE_OPERAND (op0, 0),
2230 TREE_OPERAND (op0, 1));
2231 set = tem && set_rhs (expr_p, tem);
2232 fold_undefer_overflow_warnings (set, fold_stmt_r_data->stmt, 0);
2247 /* Preserve volatileness of the original expression. */
2248 TREE_THIS_VOLATILE (t) = volatile_p;
2257 /* Return the string length, maximum string length or maximum value of
2259 If ARG is an SSA name variable, follow its use-def chains. If LENGTH
2260 is not NULL and, for TYPE == 0, its value is not equal to the length
2261 we determine or if we are unable to determine the length or value,
2262 return false. VISITED is a bitmap of visited variables.
2263 TYPE is 0 if string length should be returned, 1 for maximum string
2264 length and 2 for maximum value ARG can have. */
2267 get_maxval_strlen (tree arg, tree *length, bitmap visited, int type)
2269 tree var, def_stmt, val;
2271 if (TREE_CODE (arg) != SSA_NAME)
2273 if (TREE_CODE (arg) == COND_EXPR)
2274 return get_maxval_strlen (COND_EXPR_THEN (arg), length, visited, type)
2275 && get_maxval_strlen (COND_EXPR_ELSE (arg), length, visited, type);
2280 if (TREE_CODE (val) != INTEGER_CST
2281 || tree_int_cst_sgn (val) < 0)
2285 val = c_strlen (arg, 1);
2293 if (TREE_CODE (*length) != INTEGER_CST
2294 || TREE_CODE (val) != INTEGER_CST)
2297 if (tree_int_cst_lt (*length, val))
2301 else if (simple_cst_equal (val, *length) != 1)
2309 /* If we were already here, break the infinite cycle. */
2310 if (bitmap_bit_p (visited, SSA_NAME_VERSION (arg)))
2312 bitmap_set_bit (visited, SSA_NAME_VERSION (arg));
2315 def_stmt = SSA_NAME_DEF_STMT (var);
2317 switch (TREE_CODE (def_stmt))
2319 case GIMPLE_MODIFY_STMT:
2323 /* The RHS of the statement defining VAR must either have a
2324 constant length or come from another SSA_NAME with a constant
2326 rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
2328 return get_maxval_strlen (rhs, length, visited, type);
2333 /* All the arguments of the PHI node must have the same constant
2337 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
2339 tree arg = PHI_ARG_DEF (def_stmt, i);
2341 /* If this PHI has itself as an argument, we cannot
2342 determine the string length of this argument. However,
2343 if we can find a constant string length for the other
2344 PHI args then we can still be sure that this is a
2345 constant string length. So be optimistic and just
2346 continue with the next argument. */
2347 if (arg == PHI_RESULT (def_stmt))
2350 if (!get_maxval_strlen (arg, length, visited, type))
2366 /* Fold builtin call FN in statement STMT. If it cannot be folded into a
2367 constant, return NULL_TREE. Otherwise, return its constant value. */
2370 ccp_fold_builtin (tree stmt, tree fn)
2372 tree result, val[3];
2374 int arg_mask, i, type;
2377 call_expr_arg_iterator iter;
2380 ignore = TREE_CODE (stmt) != GIMPLE_MODIFY_STMT;
2382 /* First try the generic builtin folder. If that succeeds, return the
2384 result = fold_call_expr (fn, ignore);
2388 STRIP_NOPS (result);
2392 /* Ignore MD builtins. */
2393 callee = get_callee_fndecl (fn);
2394 if (DECL_BUILT_IN_CLASS (callee) == BUILT_IN_MD)
2397 /* If the builtin could not be folded, and it has no argument list,
2399 nargs = call_expr_nargs (fn);
2403 /* Limit the work only for builtins we know how to simplify. */
2404 switch (DECL_FUNCTION_CODE (callee))
2406 case BUILT_IN_STRLEN:
2407 case BUILT_IN_FPUTS:
2408 case BUILT_IN_FPUTS_UNLOCKED:
2412 case BUILT_IN_STRCPY:
2413 case BUILT_IN_STRNCPY:
2417 case BUILT_IN_MEMCPY_CHK:
2418 case BUILT_IN_MEMPCPY_CHK:
2419 case BUILT_IN_MEMMOVE_CHK:
2420 case BUILT_IN_MEMSET_CHK:
2421 case BUILT_IN_STRNCPY_CHK:
2425 case BUILT_IN_STRCPY_CHK:
2426 case BUILT_IN_STPCPY_CHK:
2430 case BUILT_IN_SNPRINTF_CHK:
2431 case BUILT_IN_VSNPRINTF_CHK:
2439 /* Try to use the dataflow information gathered by the CCP process. */
2440 visited = BITMAP_ALLOC (NULL);
2442 memset (val, 0, sizeof (val));
2443 init_call_expr_arg_iterator (fn, &iter);
2444 for (i = 0; arg_mask; i++, arg_mask >>= 1)
2446 a = next_call_expr_arg (&iter);
2449 bitmap_clear (visited);
2450 if (!get_maxval_strlen (a, &val[i], visited, type))
2455 BITMAP_FREE (visited);
2458 switch (DECL_FUNCTION_CODE (callee))
2460 case BUILT_IN_STRLEN:
2463 tree new_val = fold_convert (TREE_TYPE (fn), val[0]);
2465 /* If the result is not a valid gimple value, or not a cast
2466 of a valid gimple value, then we can not use the result. */
2467 if (is_gimple_val (new_val)
2468 || (is_gimple_cast (new_val)
2469 && is_gimple_val (TREE_OPERAND (new_val, 0))))
2474 case BUILT_IN_STRCPY:
2475 if (val[1] && is_gimple_val (val[1]) && nargs == 2)
2476 result = fold_builtin_strcpy (callee,
2477 CALL_EXPR_ARG (fn, 0),
2478 CALL_EXPR_ARG (fn, 1),
2482 case BUILT_IN_STRNCPY:
2483 if (val[1] && is_gimple_val (val[1]) && nargs == 3)
2484 result = fold_builtin_strncpy (callee,
2485 CALL_EXPR_ARG (fn, 0),
2486 CALL_EXPR_ARG (fn, 1),
2487 CALL_EXPR_ARG (fn, 2),
2491 case BUILT_IN_FPUTS:
2492 result = fold_builtin_fputs (CALL_EXPR_ARG (fn, 0),
2493 CALL_EXPR_ARG (fn, 1),
2494 TREE_CODE (stmt) != GIMPLE_MODIFY_STMT, 0,
2498 case BUILT_IN_FPUTS_UNLOCKED:
2499 result = fold_builtin_fputs (CALL_EXPR_ARG (fn, 0),
2500 CALL_EXPR_ARG (fn, 1),
2501 TREE_CODE (stmt) != GIMPLE_MODIFY_STMT, 1,
2505 case BUILT_IN_MEMCPY_CHK:
2506 case BUILT_IN_MEMPCPY_CHK:
2507 case BUILT_IN_MEMMOVE_CHK:
2508 case BUILT_IN_MEMSET_CHK:
2509 if (val[2] && is_gimple_val (val[2]))
2510 result = fold_builtin_memory_chk (callee,
2511 CALL_EXPR_ARG (fn, 0),
2512 CALL_EXPR_ARG (fn, 1),
2513 CALL_EXPR_ARG (fn, 2),
2514 CALL_EXPR_ARG (fn, 3),
2516 DECL_FUNCTION_CODE (callee));
2519 case BUILT_IN_STRCPY_CHK:
2520 case BUILT_IN_STPCPY_CHK:
2521 if (val[1] && is_gimple_val (val[1]))
2522 result = fold_builtin_stxcpy_chk (callee,
2523 CALL_EXPR_ARG (fn, 0),
2524 CALL_EXPR_ARG (fn, 1),
2525 CALL_EXPR_ARG (fn, 2),
2527 DECL_FUNCTION_CODE (callee));
2530 case BUILT_IN_STRNCPY_CHK:
2531 if (val[2] && is_gimple_val (val[2]))
2532 result = fold_builtin_strncpy_chk (CALL_EXPR_ARG (fn, 0),
2533 CALL_EXPR_ARG (fn, 1),
2534 CALL_EXPR_ARG (fn, 2),
2535 CALL_EXPR_ARG (fn, 3),
2539 case BUILT_IN_SNPRINTF_CHK:
2540 case BUILT_IN_VSNPRINTF_CHK:
2541 if (val[1] && is_gimple_val (val[1]))
2542 result = fold_builtin_snprintf_chk (fn, val[1],
2543 DECL_FUNCTION_CODE (callee));
2550 if (result && ignore)
2551 result = fold_ignored_result (result);
2556 /* Fold the statement pointed to by STMT_P. In some cases, this function may
2557 replace the whole statement with a new one. Returns true iff folding
2558 makes any changes. */
2561 fold_stmt (tree *stmt_p)
2563 tree rhs, result, stmt;
2564 struct fold_stmt_r_data fold_stmt_r_data;
2565 bool changed = false;
2566 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 /* If we replaced constants and the statement makes pointer dereferences,
2575 then we may need to fold instances of *&VAR into VAR, etc. */
2576 if (walk_tree (stmt_p, fold_stmt_r, &fold_stmt_r_data, NULL))
2578 *stmt_p = build_call_expr (implicit_built_in_decls[BUILT_IN_TRAP], 0);
2582 rhs = get_rhs (stmt);
2587 if (TREE_CODE (rhs) == CALL_EXPR)
2591 /* Check for builtins that CCP can handle using information not
2592 available in the generic fold routines. */
2593 callee = get_callee_fndecl (rhs);
2594 if (callee && DECL_BUILT_IN (callee))
2595 result = ccp_fold_builtin (stmt, rhs);
2598 /* Check for resolvable OBJ_TYPE_REF. The only sorts we can resolve
2599 here are when we've propagated the address of a decl into the
2601 /* ??? Should perhaps do this in fold proper. However, doing it
2602 there requires that we create a new CALL_EXPR, and that requires
2603 copying EH region info to the new node. Easier to just do it
2604 here where we can just smash the call operand. Also
2605 CALL_EXPR_RETURN_SLOT_OPT needs to be handled correctly and
2606 copied, fold_call_expr does not have not information. */
2607 callee = CALL_EXPR_FN (rhs);
2608 if (TREE_CODE (callee) == OBJ_TYPE_REF
2609 && lang_hooks.fold_obj_type_ref
2610 && TREE_CODE (OBJ_TYPE_REF_OBJECT (callee)) == ADDR_EXPR
2611 && DECL_P (TREE_OPERAND
2612 (OBJ_TYPE_REF_OBJECT (callee), 0)))
2616 /* ??? Caution: Broken ADDR_EXPR semantics means that
2617 looking at the type of the operand of the addr_expr
2618 can yield an array type. See silly exception in
2619 check_pointer_types_r. */
2621 t = TREE_TYPE (TREE_TYPE (OBJ_TYPE_REF_OBJECT (callee)));
2622 t = lang_hooks.fold_obj_type_ref (callee, t);
2625 CALL_EXPR_FN (rhs) = t;
2631 else if (TREE_CODE (rhs) == COND_EXPR)
2633 tree temp = fold (COND_EXPR_COND (rhs));
2634 if (temp != COND_EXPR_COND (rhs))
2635 result = fold_build3 (COND_EXPR, TREE_TYPE (rhs), temp,
2636 COND_EXPR_THEN (rhs), COND_EXPR_ELSE (rhs));
2639 /* If we couldn't fold the RHS, hand over to the generic fold routines. */
2640 if (result == NULL_TREE)
2641 result = fold (rhs);
2643 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
2644 may have been added by fold, and "useless" type conversions that might
2645 now be apparent due to propagation. */
2646 STRIP_USELESS_TYPE_CONVERSION (result);
2649 changed |= set_rhs (stmt_p, result);
2654 /* Perform the minimal folding on statement STMT. Only operations like
2655 *&x created by constant propagation are handled. The statement cannot
2656 be replaced with a new one. */
2659 fold_stmt_inplace (tree stmt)
2661 tree old_stmt = stmt, rhs, new_rhs;
2662 struct fold_stmt_r_data fold_stmt_r_data;
2663 bool changed = false;
2664 bool inside_addr_expr = false;
2666 fold_stmt_r_data.stmt = stmt;
2667 fold_stmt_r_data.changed_p = &changed;
2668 fold_stmt_r_data.inside_addr_expr_p = &inside_addr_expr;
2670 walk_tree (&stmt, fold_stmt_r, &fold_stmt_r_data, NULL);
2671 gcc_assert (stmt == old_stmt);
2673 rhs = get_rhs (stmt);
2674 if (!rhs || rhs == stmt)
2677 new_rhs = fold (rhs);
2678 STRIP_USELESS_TYPE_CONVERSION (new_rhs);
2682 changed |= set_rhs (&stmt, new_rhs);
2683 gcc_assert (stmt == old_stmt);
2688 /* Try to optimize out __builtin_stack_restore. Optimize it out
2689 if there is another __builtin_stack_restore in the same basic
2690 block and no calls or ASM_EXPRs are in between, or if this block's
2691 only outgoing edge is to EXIT_BLOCK and there are no calls or
2692 ASM_EXPRs after this __builtin_stack_restore. */
2695 optimize_stack_restore (basic_block bb, tree call, block_stmt_iterator i)
2697 tree stack_save, stmt, callee;
2699 if (TREE_CODE (call) != CALL_EXPR
2700 || call_expr_nargs (call) != 1
2701 || TREE_CODE (CALL_EXPR_ARG (call, 0)) != SSA_NAME
2702 || !POINTER_TYPE_P (TREE_TYPE (CALL_EXPR_ARG (call, 0))))
2705 for (bsi_next (&i); !bsi_end_p (i); bsi_next (&i))
2709 stmt = bsi_stmt (i);
2710 if (TREE_CODE (stmt) == ASM_EXPR)
2712 call = get_call_expr_in (stmt);
2716 callee = get_callee_fndecl (call);
2717 if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)
2720 if (DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_RESTORE)
2725 && (! single_succ_p (bb)
2726 || single_succ_edge (bb)->dest != EXIT_BLOCK_PTR))
2729 stack_save = SSA_NAME_DEF_STMT (CALL_EXPR_ARG (call, 0));
2730 if (TREE_CODE (stack_save) != GIMPLE_MODIFY_STMT
2731 || GIMPLE_STMT_OPERAND (stack_save, 0) != CALL_EXPR_ARG (call, 0)
2732 || TREE_CODE (GIMPLE_STMT_OPERAND (stack_save, 1)) != CALL_EXPR
2733 || tree_could_throw_p (stack_save)
2734 || !has_single_use (CALL_EXPR_ARG (call, 0)))
2737 callee = get_callee_fndecl (GIMPLE_STMT_OPERAND (stack_save, 1));
2739 || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL
2740 || DECL_FUNCTION_CODE (callee) != BUILT_IN_STACK_SAVE
2741 || call_expr_nargs (GIMPLE_STMT_OPERAND (stack_save, 1)) != 0)
2745 push_stmt_changes (&stmt);
2746 if (!set_rhs (&stmt,
2747 build_int_cst (TREE_TYPE (CALL_EXPR_ARG (call, 0)), 0)))
2749 discard_stmt_changes (&stmt);
2752 gcc_assert (stmt == stack_save);
2753 pop_stmt_changes (&stmt);
2755 return integer_zero_node;
2758 /* If va_list type is a simple pointer and nothing special is needed,
2759 optimize __builtin_va_start (&ap, 0) into ap = __builtin_next_arg (0),
2760 __builtin_va_end (&ap) out as NOP and __builtin_va_copy into a simple
2761 pointer assignment. */
2764 optimize_stdarg_builtin (tree call)
2766 tree callee, lhs, rhs;
2767 bool va_list_simple_ptr;
2769 if (TREE_CODE (call) != CALL_EXPR)
2772 va_list_simple_ptr = POINTER_TYPE_P (va_list_type_node)
2773 && (TREE_TYPE (va_list_type_node) == void_type_node
2774 || TREE_TYPE (va_list_type_node) == char_type_node);
2776 callee = get_callee_fndecl (call);
2777 switch (DECL_FUNCTION_CODE (callee))
2779 case BUILT_IN_VA_START:
2780 if (!va_list_simple_ptr
2781 || targetm.expand_builtin_va_start != NULL
2782 || built_in_decls[BUILT_IN_NEXT_ARG] == NULL)
2785 if (call_expr_nargs (call) != 2)
2788 lhs = CALL_EXPR_ARG (call, 0);
2789 if (!POINTER_TYPE_P (TREE_TYPE (lhs))
2790 || TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs)))
2791 != TYPE_MAIN_VARIANT (va_list_type_node))
2794 lhs = build_fold_indirect_ref (lhs);
2795 rhs = build_call_expr (built_in_decls[BUILT_IN_NEXT_ARG],
2796 1, integer_zero_node);
2797 rhs = fold_convert (TREE_TYPE (lhs), rhs);
2798 return build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, rhs);
2800 case BUILT_IN_VA_COPY:
2801 if (!va_list_simple_ptr)
2804 if (call_expr_nargs (call) != 2)
2807 lhs = CALL_EXPR_ARG (call, 0);
2808 if (!POINTER_TYPE_P (TREE_TYPE (lhs))
2809 || TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs)))
2810 != TYPE_MAIN_VARIANT (va_list_type_node))
2813 lhs = build_fold_indirect_ref (lhs);
2814 rhs = CALL_EXPR_ARG (call, 1);
2815 if (TYPE_MAIN_VARIANT (TREE_TYPE (rhs))
2816 != TYPE_MAIN_VARIANT (va_list_type_node))
2819 rhs = fold_convert (TREE_TYPE (lhs), rhs);
2820 return build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, rhs);
2822 case BUILT_IN_VA_END:
2823 return integer_zero_node;
2830 /* Convert EXPR into a GIMPLE value suitable for substitution on the
2831 RHS of an assignment. Insert the necessary statements before
2833 When IGNORE is set, don't worry about the return value. */
2836 convert_to_gimple_builtin (block_stmt_iterator *si_p, tree expr, bool ignore)
2838 tree_stmt_iterator ti;
2839 tree stmt = bsi_stmt (*si_p);
2840 tree tmp, stmts = NULL;
2842 push_gimplify_context ();
2845 tmp = build_empty_stmt ();
2846 gimplify_and_add (expr, &stmts);
2849 tmp = get_initialized_tmp_var (expr, &stmts, NULL);
2850 pop_gimplify_context (NULL);
2852 if (EXPR_HAS_LOCATION (stmt))
2853 annotate_all_with_locus (&stmts, EXPR_LOCATION (stmt));
2855 /* The replacement can expose previously unreferenced variables. */
2856 for (ti = tsi_start (stmts); !tsi_end_p (ti); tsi_next (&ti))
2858 tree new_stmt = tsi_stmt (ti);
2859 find_new_referenced_vars (tsi_stmt_ptr (ti));
2860 bsi_insert_before (si_p, new_stmt, BSI_NEW_STMT);
2861 mark_symbols_for_renaming (new_stmt);
2869 /* A simple pass that attempts to fold all builtin functions. This pass
2870 is run after we've propagated as many constants as we can. */
2873 execute_fold_all_builtins (void)
2875 bool cfg_changed = false;
2877 unsigned int todoflags = 0;
2881 block_stmt_iterator i;
2882 for (i = bsi_start (bb); !bsi_end_p (i); )
2884 tree *stmtp = bsi_stmt_ptr (i);
2885 tree old_stmt = *stmtp;
2886 tree call = get_rhs (*stmtp);
2887 tree callee, result;
2888 enum built_in_function fcode;
2890 if (!call || TREE_CODE (call) != CALL_EXPR)
2895 callee = get_callee_fndecl (call);
2896 if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)
2901 fcode = DECL_FUNCTION_CODE (callee);
2903 result = ccp_fold_builtin (*stmtp, call);
2905 switch (DECL_FUNCTION_CODE (callee))
2907 case BUILT_IN_CONSTANT_P:
2908 /* Resolve __builtin_constant_p. If it hasn't been
2909 folded to integer_one_node by now, it's fairly
2910 certain that the value simply isn't constant. */
2911 result = integer_zero_node;
2914 case BUILT_IN_STACK_RESTORE:
2915 result = optimize_stack_restore (bb, *stmtp, i);
2921 case BUILT_IN_VA_START:
2922 case BUILT_IN_VA_END:
2923 case BUILT_IN_VA_COPY:
2924 /* These shouldn't be folded before pass_stdarg. */
2925 result = optimize_stdarg_builtin (*stmtp);
2935 if (dump_file && (dump_flags & TDF_DETAILS))
2937 fprintf (dump_file, "Simplified\n ");
2938 print_generic_stmt (dump_file, *stmtp, dump_flags);
2941 push_stmt_changes (stmtp);
2943 if (!set_rhs (stmtp, result))
2945 result = convert_to_gimple_builtin (&i, result,
2946 TREE_CODE (old_stmt)
2947 != GIMPLE_MODIFY_STMT);
2950 bool ok = set_rhs (stmtp, result);
2952 todoflags |= TODO_rebuild_alias;
2956 pop_stmt_changes (stmtp);
2958 if (maybe_clean_or_replace_eh_stmt (old_stmt, *stmtp)
2959 && tree_purge_dead_eh_edges (bb))
2962 if (dump_file && (dump_flags & TDF_DETAILS))
2964 fprintf (dump_file, "to\n ");
2965 print_generic_stmt (dump_file, *stmtp, dump_flags);
2966 fprintf (dump_file, "\n");
2969 /* Retry the same statement if it changed into another
2970 builtin, there might be new opportunities now. */
2971 call = get_rhs (*stmtp);
2972 if (!call || TREE_CODE (call) != CALL_EXPR)
2977 callee = get_callee_fndecl (call);
2979 || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL
2980 || DECL_FUNCTION_CODE (callee) == fcode)
2985 /* Delete unreachable blocks. */
2987 todoflags |= TODO_cleanup_cfg;
2993 struct tree_opt_pass pass_fold_builtins =
2997 execute_fold_all_builtins, /* execute */
3000 0, /* static_pass_number */
3002 PROP_cfg | PROP_ssa, /* properties_required */
3003 0, /* properties_provided */
3004 0, /* properties_destroyed */
3005 0, /* todo_flags_start */
3008 | TODO_update_ssa, /* todo_flags_finish */