1 /* Conditional constant propagation pass for the GNU compiler.
2 Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
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 "value-prof.h"
208 #include "langhooks.h"
214 /* Possible lattice values. */
223 /* Array of propagated constant values. After propagation,
224 CONST_VAL[I].VALUE holds the constant value for SSA_NAME(I). If
225 the constant is held in an SSA name representing a memory store
226 (i.e., a VDEF), CONST_VAL[I].MEM_REF will contain the actual
227 memory reference used to store (i.e., the LHS of the assignment
229 static prop_value_t *const_val;
231 static void canonicalize_float_value (prop_value_t *);
232 static bool ccp_fold_stmt (gimple_stmt_iterator *);
234 /* Dump constant propagation value VAL to file OUTF prefixed by PREFIX. */
237 dump_lattice_value (FILE *outf, const char *prefix, prop_value_t val)
239 switch (val.lattice_val)
242 fprintf (outf, "%sUNINITIALIZED", prefix);
245 fprintf (outf, "%sUNDEFINED", prefix);
248 fprintf (outf, "%sVARYING", prefix);
251 fprintf (outf, "%sCONSTANT ", prefix);
252 print_generic_expr (outf, val.value, dump_flags);
260 /* Print lattice value VAL to stderr. */
262 void debug_lattice_value (prop_value_t val);
265 debug_lattice_value (prop_value_t val)
267 dump_lattice_value (stderr, "", val);
268 fprintf (stderr, "\n");
273 /* If SYM is a constant variable with known value, return the value.
274 NULL_TREE is returned otherwise. */
277 get_symbol_constant_value (tree sym)
279 if (TREE_STATIC (sym)
280 && (TREE_READONLY (sym)
281 || TREE_CODE (sym) == CONST_DECL))
283 tree val = DECL_INITIAL (sym);
286 STRIP_USELESS_TYPE_CONVERSION (val);
287 if (is_gimple_min_invariant (val))
289 if (TREE_CODE (val) == ADDR_EXPR)
291 tree base = get_base_address (TREE_OPERAND (val, 0));
292 if (base && TREE_CODE (base) == VAR_DECL)
294 TREE_ADDRESSABLE (base) = 1;
295 if (gimple_referenced_vars (cfun))
296 add_referenced_var (base);
302 /* Variables declared 'const' without an initializer
303 have zero as the initializer if they may not be
304 overridden at link or run time. */
306 && !DECL_EXTERNAL (sym)
307 && targetm.binds_local_p (sym)
308 && (INTEGRAL_TYPE_P (TREE_TYPE (sym))
309 || SCALAR_FLOAT_TYPE_P (TREE_TYPE (sym))))
310 return fold_convert (TREE_TYPE (sym), integer_zero_node);
316 /* Compute a default value for variable VAR and store it in the
317 CONST_VAL array. The following rules are used to get default
320 1- Global and static variables that are declared constant are
323 2- Any other value is considered UNDEFINED. This is useful when
324 considering PHI nodes. PHI arguments that are undefined do not
325 change the constant value of the PHI node, which allows for more
326 constants to be propagated.
328 3- Variables defined by statements other than assignments and PHI
329 nodes are considered VARYING.
331 4- Initial values of variables that are not GIMPLE registers are
332 considered VARYING. */
335 get_default_value (tree var)
337 tree sym = SSA_NAME_VAR (var);
338 prop_value_t val = { UNINITIALIZED, NULL_TREE };
341 stmt = SSA_NAME_DEF_STMT (var);
343 if (gimple_nop_p (stmt))
345 /* Variables defined by an empty statement are those used
346 before being initialized. If VAR is a local variable, we
347 can assume initially that it is UNDEFINED, otherwise we must
348 consider it VARYING. */
349 if (is_gimple_reg (sym) && TREE_CODE (sym) != PARM_DECL)
350 val.lattice_val = UNDEFINED;
352 val.lattice_val = VARYING;
354 else if (is_gimple_assign (stmt)
355 /* Value-returning GIMPLE_CALL statements assign to
356 a variable, and are treated similarly to GIMPLE_ASSIGN. */
357 || (is_gimple_call (stmt)
358 && gimple_call_lhs (stmt) != NULL_TREE)
359 || gimple_code (stmt) == GIMPLE_PHI)
362 if (gimple_assign_single_p (stmt)
363 && DECL_P (gimple_assign_rhs1 (stmt))
364 && (cst = get_symbol_constant_value (gimple_assign_rhs1 (stmt))))
366 val.lattice_val = CONSTANT;
370 /* Any other variable defined by an assignment or a PHI node
371 is considered UNDEFINED. */
372 val.lattice_val = UNDEFINED;
376 /* Otherwise, VAR will never take on a constant value. */
377 val.lattice_val = VARYING;
384 /* Get the constant value associated with variable VAR. */
386 static inline prop_value_t *
391 if (const_val == NULL)
394 val = &const_val[SSA_NAME_VERSION (var)];
395 if (val->lattice_val == UNINITIALIZED)
396 *val = get_default_value (var);
398 canonicalize_float_value (val);
403 /* Sets the value associated with VAR to VARYING. */
406 set_value_varying (tree var)
408 prop_value_t *val = &const_val[SSA_NAME_VERSION (var)];
410 val->lattice_val = VARYING;
411 val->value = NULL_TREE;
414 /* For float types, modify the value of VAL to make ccp work correctly
415 for non-standard values (-0, NaN):
417 If HONOR_SIGNED_ZEROS is false, and VAL = -0, we canonicalize it to 0.
418 If HONOR_NANS is false, and VAL is NaN, we canonicalize it to UNDEFINED.
419 This is to fix the following problem (see PR 29921): Suppose we have
423 and we set value of y to NaN. This causes value of x to be set to NaN.
424 When we later determine that y is in fact VARYING, fold uses the fact
425 that HONOR_NANS is false, and we try to change the value of x to 0,
426 causing an ICE. With HONOR_NANS being false, the real appearance of
427 NaN would cause undefined behavior, though, so claiming that y (and x)
428 are UNDEFINED initially is correct. */
431 canonicalize_float_value (prop_value_t *val)
433 enum machine_mode mode;
437 if (val->lattice_val != CONSTANT
438 || TREE_CODE (val->value) != REAL_CST)
441 d = TREE_REAL_CST (val->value);
442 type = TREE_TYPE (val->value);
443 mode = TYPE_MODE (type);
445 if (!HONOR_SIGNED_ZEROS (mode)
446 && REAL_VALUE_MINUS_ZERO (d))
448 val->value = build_real (type, dconst0);
452 if (!HONOR_NANS (mode)
453 && REAL_VALUE_ISNAN (d))
455 val->lattice_val = UNDEFINED;
461 /* Set the value for variable VAR to NEW_VAL. Return true if the new
462 value is different from VAR's previous value. */
465 set_lattice_value (tree var, prop_value_t new_val)
467 prop_value_t *old_val = get_value (var);
469 canonicalize_float_value (&new_val);
471 /* Lattice transitions must always be monotonically increasing in
472 value. If *OLD_VAL and NEW_VAL are the same, return false to
473 inform the caller that this was a non-transition. */
475 gcc_assert (old_val->lattice_val < new_val.lattice_val
476 || (old_val->lattice_val == new_val.lattice_val
477 && ((!old_val->value && !new_val.value)
478 || operand_equal_p (old_val->value, new_val.value, 0))));
480 if (old_val->lattice_val != new_val.lattice_val)
482 if (dump_file && (dump_flags & TDF_DETAILS))
484 dump_lattice_value (dump_file, "Lattice value changed to ", new_val);
485 fprintf (dump_file, ". Adding SSA edges to worklist.\n");
490 gcc_assert (new_val.lattice_val != UNDEFINED);
498 /* Return the likely CCP lattice value for STMT.
500 If STMT has no operands, then return CONSTANT.
502 Else if undefinedness of operands of STMT cause its value to be
503 undefined, then return UNDEFINED.
505 Else if any operands of STMT are constants, then return CONSTANT.
507 Else return VARYING. */
510 likely_value (gimple stmt)
512 bool has_constant_operand, has_undefined_operand, all_undefined_operands;
517 enum gimple_code code = gimple_code (stmt);
519 /* This function appears to be called only for assignments, calls,
520 conditionals, and switches, due to the logic in visit_stmt. */
521 gcc_assert (code == GIMPLE_ASSIGN
522 || code == GIMPLE_CALL
523 || code == GIMPLE_COND
524 || code == GIMPLE_SWITCH);
526 /* If the statement has volatile operands, it won't fold to a
528 if (gimple_has_volatile_ops (stmt))
531 /* Arrive here for more complex cases. */
532 has_constant_operand = false;
533 has_undefined_operand = false;
534 all_undefined_operands = true;
535 FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
537 prop_value_t *val = get_value (use);
539 if (val->lattice_val == UNDEFINED)
540 has_undefined_operand = true;
542 all_undefined_operands = false;
544 if (val->lattice_val == CONSTANT)
545 has_constant_operand = true;
548 /* There may be constants in regular rhs operands. For calls we
549 have to ignore lhs, fndecl and static chain, otherwise only
551 for (i = (is_gimple_call (stmt) ? 2 : 0) + gimple_has_lhs (stmt);
552 i < gimple_num_ops (stmt); ++i)
554 tree op = gimple_op (stmt, i);
555 if (!op || TREE_CODE (op) == SSA_NAME)
557 if (is_gimple_min_invariant (op))
558 has_constant_operand = true;
561 /* If the operation combines operands like COMPLEX_EXPR make sure to
562 not mark the result UNDEFINED if only one part of the result is
564 if (has_undefined_operand && all_undefined_operands)
566 else if (code == GIMPLE_ASSIGN && has_undefined_operand)
568 switch (gimple_assign_rhs_code (stmt))
570 /* Unary operators are handled with all_undefined_operands. */
573 case POINTER_PLUS_EXPR:
574 /* Not MIN_EXPR, MAX_EXPR. One VARYING operand may be selected.
575 Not bitwise operators, one VARYING operand may specify the
576 result completely. Not logical operators for the same reason.
577 Not COMPLEX_EXPR as one VARYING operand makes the result partly
578 not UNDEFINED. Not *DIV_EXPR, comparisons and shifts because
579 the undefined operand may be promoted. */
586 /* If there was an UNDEFINED operand but the result may be not UNDEFINED
587 fall back to VARYING even if there were CONSTANT operands. */
588 if (has_undefined_operand)
591 /* We do not consider virtual operands here -- load from read-only
592 memory may have only VARYING virtual operands, but still be
594 if (has_constant_operand
595 || gimple_references_memory_p (stmt))
601 /* Returns true if STMT cannot be constant. */
604 surely_varying_stmt_p (gimple stmt)
606 /* If the statement has operands that we cannot handle, it cannot be
608 if (gimple_has_volatile_ops (stmt))
611 /* If it is a call and does not return a value or is not a
612 builtin and not an indirect call, it is varying. */
613 if (is_gimple_call (stmt))
616 if (!gimple_call_lhs (stmt)
617 || ((fndecl = gimple_call_fndecl (stmt)) != NULL_TREE
618 && !DECL_BUILT_IN (fndecl)))
622 /* Any other store operation is not interesting. */
623 else if (gimple_vdef (stmt))
626 /* Anything other than assignments and conditional jumps are not
627 interesting for CCP. */
628 if (gimple_code (stmt) != GIMPLE_ASSIGN
629 && gimple_code (stmt) != GIMPLE_COND
630 && gimple_code (stmt) != GIMPLE_SWITCH
631 && gimple_code (stmt) != GIMPLE_CALL)
637 /* Initialize local data structures for CCP. */
640 ccp_initialize (void)
644 const_val = XCNEWVEC (prop_value_t, num_ssa_names);
646 /* Initialize simulation flags for PHI nodes and statements. */
649 gimple_stmt_iterator i;
651 for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
653 gimple stmt = gsi_stmt (i);
656 /* If the statement is a control insn, then we do not
657 want to avoid simulating the statement once. Failure
658 to do so means that those edges will never get added. */
659 if (stmt_ends_bb_p (stmt))
662 is_varying = surely_varying_stmt_p (stmt);
669 /* If the statement will not produce a constant, mark
670 all its outputs VARYING. */
671 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
672 set_value_varying (def);
674 prop_set_simulate_again (stmt, !is_varying);
678 /* Now process PHI nodes. We never clear the simulate_again flag on
679 phi nodes, since we do not know which edges are executable yet,
680 except for phi nodes for virtual operands when we do not do store ccp. */
683 gimple_stmt_iterator i;
685 for (i = gsi_start_phis (bb); !gsi_end_p (i); gsi_next (&i))
687 gimple phi = gsi_stmt (i);
689 if (!is_gimple_reg (gimple_phi_result (phi)))
690 prop_set_simulate_again (phi, false);
692 prop_set_simulate_again (phi, true);
697 /* Debug count support. Reset the values of ssa names
698 VARYING when the total number ssa names analyzed is
699 beyond the debug count specified. */
705 for (i = 0; i < num_ssa_names; i++)
709 const_val[i].lattice_val = VARYING;
710 const_val[i].value = NULL_TREE;
716 /* Do final substitution of propagated values, cleanup the flowgraph and
717 free allocated storage.
719 Return TRUE when something was optimized. */
724 bool something_changed;
727 /* Perform substitutions based on the known constant values. */
728 something_changed = substitute_and_fold (const_val, ccp_fold_stmt);
732 return something_changed;;
736 /* Compute the meet operator between *VAL1 and *VAL2. Store the result
739 any M UNDEFINED = any
740 any M VARYING = VARYING
741 Ci M Cj = Ci if (i == j)
742 Ci M Cj = VARYING if (i != j)
746 ccp_lattice_meet (prop_value_t *val1, prop_value_t *val2)
748 if (val1->lattice_val == UNDEFINED)
750 /* UNDEFINED M any = any */
753 else if (val2->lattice_val == UNDEFINED)
755 /* any M UNDEFINED = any
756 Nothing to do. VAL1 already contains the value we want. */
759 else if (val1->lattice_val == VARYING
760 || val2->lattice_val == VARYING)
762 /* any M VARYING = VARYING. */
763 val1->lattice_val = VARYING;
764 val1->value = NULL_TREE;
766 else if (val1->lattice_val == CONSTANT
767 && val2->lattice_val == CONSTANT
768 && simple_cst_equal (val1->value, val2->value) == 1)
770 /* Ci M Cj = Ci if (i == j)
771 Ci M Cj = VARYING if (i != j)
773 If these two values come from memory stores, make sure that
774 they come from the same memory reference. */
775 val1->lattice_val = CONSTANT;
776 val1->value = val1->value;
780 /* Any other combination is VARYING. */
781 val1->lattice_val = VARYING;
782 val1->value = NULL_TREE;
787 /* Loop through the PHI_NODE's parameters for BLOCK and compare their
788 lattice values to determine PHI_NODE's lattice value. The value of a
789 PHI node is determined calling ccp_lattice_meet with all the arguments
790 of the PHI node that are incoming via executable edges. */
792 static enum ssa_prop_result
793 ccp_visit_phi_node (gimple phi)
796 prop_value_t *old_val, new_val;
798 if (dump_file && (dump_flags & TDF_DETAILS))
800 fprintf (dump_file, "\nVisiting PHI node: ");
801 print_gimple_stmt (dump_file, phi, 0, dump_flags);
804 old_val = get_value (gimple_phi_result (phi));
805 switch (old_val->lattice_val)
808 return SSA_PROP_VARYING;
815 new_val.lattice_val = UNDEFINED;
816 new_val.value = NULL_TREE;
823 for (i = 0; i < gimple_phi_num_args (phi); i++)
825 /* Compute the meet operator over all the PHI arguments flowing
826 through executable edges. */
827 edge e = gimple_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 = gimple_phi_arg (phi, i)->def;
842 prop_value_t arg_val;
844 if (is_gimple_min_invariant (arg))
846 arg_val.lattice_val = CONSTANT;
850 arg_val = *(get_value (arg));
852 ccp_lattice_meet (&new_val, &arg_val);
854 if (dump_file && (dump_flags & TDF_DETAILS))
856 fprintf (dump_file, "\t");
857 print_generic_expr (dump_file, arg, dump_flags);
858 dump_lattice_value (dump_file, "\tValue: ", arg_val);
859 fprintf (dump_file, "\n");
862 if (new_val.lattice_val == VARYING)
867 if (dump_file && (dump_flags & TDF_DETAILS))
869 dump_lattice_value (dump_file, "\n PHI node value: ", new_val);
870 fprintf (dump_file, "\n\n");
873 /* Make the transition to the new value. */
874 if (set_lattice_value (gimple_phi_result (phi), new_val))
876 if (new_val.lattice_val == VARYING)
877 return SSA_PROP_VARYING;
879 return SSA_PROP_INTERESTING;
882 return SSA_PROP_NOT_INTERESTING;
885 /* Return true if we may propagate the address expression ADDR into the
886 dereference DEREF and cancel them. */
889 may_propagate_address_into_dereference (tree addr, tree deref)
891 gcc_assert (INDIRECT_REF_P (deref)
892 && TREE_CODE (addr) == ADDR_EXPR);
894 /* Don't propagate if ADDR's operand has incomplete type. */
895 if (!COMPLETE_TYPE_P (TREE_TYPE (TREE_OPERAND (addr, 0))))
898 /* If the address is invariant then we do not need to preserve restrict
899 qualifications. But we do need to preserve volatile qualifiers until
900 we can annotate the folded dereference itself properly. */
901 if (is_gimple_min_invariant (addr)
902 && (!TREE_THIS_VOLATILE (deref)
903 || TYPE_VOLATILE (TREE_TYPE (addr))))
904 return useless_type_conversion_p (TREE_TYPE (deref),
905 TREE_TYPE (TREE_OPERAND (addr, 0)));
907 /* Else both the address substitution and the folding must result in
908 a valid useless type conversion sequence. */
909 return (useless_type_conversion_p (TREE_TYPE (TREE_OPERAND (deref, 0)),
911 && useless_type_conversion_p (TREE_TYPE (deref),
912 TREE_TYPE (TREE_OPERAND (addr, 0))));
915 /* CCP specific front-end to the non-destructive constant folding
918 Attempt to simplify the RHS of STMT knowing that one or more
919 operands are constants.
921 If simplification is possible, return the simplified RHS,
922 otherwise return the original RHS or NULL_TREE. */
925 ccp_fold (gimple stmt)
927 location_t loc = gimple_location (stmt);
928 switch (gimple_code (stmt))
932 enum tree_code subcode = gimple_assign_rhs_code (stmt);
934 switch (get_gimple_rhs_class (subcode))
936 case GIMPLE_SINGLE_RHS:
938 tree rhs = gimple_assign_rhs1 (stmt);
939 enum tree_code_class kind = TREE_CODE_CLASS (subcode);
941 if (TREE_CODE (rhs) == SSA_NAME)
943 /* If the RHS is an SSA_NAME, return its known constant value,
945 return get_value (rhs)->value;
947 /* Handle propagating invariant addresses into address operations.
948 The folding we do here matches that in tree-ssa-forwprop.c. */
949 else if (TREE_CODE (rhs) == ADDR_EXPR)
952 base = &TREE_OPERAND (rhs, 0);
953 while (handled_component_p (*base))
954 base = &TREE_OPERAND (*base, 0);
955 if (TREE_CODE (*base) == INDIRECT_REF
956 && TREE_CODE (TREE_OPERAND (*base, 0)) == SSA_NAME)
958 prop_value_t *val = get_value (TREE_OPERAND (*base, 0));
959 if (val->lattice_val == CONSTANT
960 && TREE_CODE (val->value) == ADDR_EXPR
961 && may_propagate_address_into_dereference
964 /* We need to return a new tree, not modify the IL
965 or share parts of it. So play some tricks to
966 avoid manually building it. */
967 tree ret, save = *base;
968 *base = TREE_OPERAND (val->value, 0);
969 ret = unshare_expr (rhs);
970 recompute_tree_invariant_for_addr_expr (ret);
976 else if (TREE_CODE (rhs) == CONSTRUCTOR
977 && TREE_CODE (TREE_TYPE (rhs)) == VECTOR_TYPE
978 && (CONSTRUCTOR_NELTS (rhs)
979 == TYPE_VECTOR_SUBPARTS (TREE_TYPE (rhs))))
985 FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (rhs), i, val)
987 if (TREE_CODE (val) == SSA_NAME
988 && get_value (val)->lattice_val == CONSTANT)
989 val = get_value (val)->value;
990 if (TREE_CODE (val) == INTEGER_CST
991 || TREE_CODE (val) == REAL_CST
992 || TREE_CODE (val) == FIXED_CST)
993 list = tree_cons (NULL_TREE, val, list);
998 return build_vector (TREE_TYPE (rhs), nreverse (list));
1001 if (kind == tcc_reference)
1003 if ((TREE_CODE (rhs) == VIEW_CONVERT_EXPR
1004 || TREE_CODE (rhs) == REALPART_EXPR
1005 || TREE_CODE (rhs) == IMAGPART_EXPR)
1006 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
1008 prop_value_t *val = get_value (TREE_OPERAND (rhs, 0));
1009 if (val->lattice_val == CONSTANT)
1010 return fold_unary_loc (EXPR_LOCATION (rhs),
1012 TREE_TYPE (rhs), val->value);
1014 else if (TREE_CODE (rhs) == INDIRECT_REF
1015 && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
1017 prop_value_t *val = get_value (TREE_OPERAND (rhs, 0));
1018 if (val->lattice_val == CONSTANT
1019 && TREE_CODE (val->value) == ADDR_EXPR
1020 && useless_type_conversion_p (TREE_TYPE (rhs),
1021 TREE_TYPE (TREE_TYPE (val->value))))
1022 rhs = TREE_OPERAND (val->value, 0);
1024 return fold_const_aggregate_ref (rhs);
1026 else if (kind == tcc_declaration)
1027 return get_symbol_constant_value (rhs);
1031 case GIMPLE_UNARY_RHS:
1033 /* Handle unary operators that can appear in GIMPLE form.
1034 Note that we know the single operand must be a constant,
1035 so this should almost always return a simplified RHS. */
1036 tree lhs = gimple_assign_lhs (stmt);
1037 tree op0 = gimple_assign_rhs1 (stmt);
1039 /* Simplify the operand down to a constant. */
1040 if (TREE_CODE (op0) == SSA_NAME)
1042 prop_value_t *val = get_value (op0);
1043 if (val->lattice_val == CONSTANT)
1044 op0 = get_value (op0)->value;
1047 /* Conversions are useless for CCP purposes if they are
1048 value-preserving. Thus the restrictions that
1049 useless_type_conversion_p places for pointer type conversions
1050 do not apply here. Substitution later will only substitute to
1052 if (CONVERT_EXPR_CODE_P (subcode)
1053 && POINTER_TYPE_P (TREE_TYPE (lhs))
1054 && POINTER_TYPE_P (TREE_TYPE (op0))
1055 /* Do not allow differences in volatile qualification
1056 as this might get us confused as to whether a
1057 propagation destination statement is volatile
1058 or not. See PR36988. */
1059 && (TYPE_VOLATILE (TREE_TYPE (TREE_TYPE (lhs)))
1060 == TYPE_VOLATILE (TREE_TYPE (TREE_TYPE (op0)))))
1063 /* Still try to generate a constant of correct type. */
1064 if (!useless_type_conversion_p (TREE_TYPE (lhs),
1066 && ((tem = maybe_fold_offset_to_address
1068 op0, integer_zero_node, TREE_TYPE (lhs)))
1075 fold_unary_ignore_overflow_loc (loc, subcode,
1076 gimple_expr_type (stmt), op0);
1079 case GIMPLE_BINARY_RHS:
1081 /* Handle binary operators that can appear in GIMPLE form. */
1082 tree op0 = gimple_assign_rhs1 (stmt);
1083 tree op1 = gimple_assign_rhs2 (stmt);
1085 /* Simplify the operands down to constants when appropriate. */
1086 if (TREE_CODE (op0) == SSA_NAME)
1088 prop_value_t *val = get_value (op0);
1089 if (val->lattice_val == CONSTANT)
1093 if (TREE_CODE (op1) == SSA_NAME)
1095 prop_value_t *val = get_value (op1);
1096 if (val->lattice_val == CONSTANT)
1100 /* Fold &foo + CST into an invariant reference if possible. */
1101 if (gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR
1102 && TREE_CODE (op0) == ADDR_EXPR
1103 && TREE_CODE (op1) == INTEGER_CST)
1105 tree tem = maybe_fold_offset_to_address
1106 (loc, op0, op1, TREE_TYPE (op0));
1107 if (tem != NULL_TREE)
1111 return fold_binary_loc (loc, subcode,
1112 gimple_expr_type (stmt), op0, op1);
1123 tree fn = gimple_call_fn (stmt);
1126 if (TREE_CODE (fn) == SSA_NAME)
1128 val = get_value (fn);
1129 if (val->lattice_val == CONSTANT)
1132 if (TREE_CODE (fn) == ADDR_EXPR
1133 && TREE_CODE (TREE_OPERAND (fn, 0)) == FUNCTION_DECL
1134 && DECL_BUILT_IN (TREE_OPERAND (fn, 0)))
1136 tree *args = XALLOCAVEC (tree, gimple_call_num_args (stmt));
1139 for (i = 0; i < gimple_call_num_args (stmt); ++i)
1141 args[i] = gimple_call_arg (stmt, i);
1142 if (TREE_CODE (args[i]) == SSA_NAME)
1144 val = get_value (args[i]);
1145 if (val->lattice_val == CONSTANT)
1146 args[i] = val->value;
1149 call = build_call_array_loc (loc,
1150 gimple_call_return_type (stmt),
1151 fn, gimple_call_num_args (stmt), args);
1152 retval = fold_call_expr (EXPR_LOCATION (call), call, false);
1154 /* fold_call_expr wraps the result inside a NOP_EXPR. */
1155 STRIP_NOPS (retval);
1163 /* Handle comparison operators that can appear in GIMPLE form. */
1164 tree op0 = gimple_cond_lhs (stmt);
1165 tree op1 = gimple_cond_rhs (stmt);
1166 enum tree_code code = gimple_cond_code (stmt);
1168 /* Simplify the operands down to constants when appropriate. */
1169 if (TREE_CODE (op0) == SSA_NAME)
1171 prop_value_t *val = get_value (op0);
1172 if (val->lattice_val == CONSTANT)
1176 if (TREE_CODE (op1) == SSA_NAME)
1178 prop_value_t *val = get_value (op1);
1179 if (val->lattice_val == CONSTANT)
1183 return fold_binary_loc (loc, code, boolean_type_node, op0, op1);
1188 tree rhs = gimple_switch_index (stmt);
1190 if (TREE_CODE (rhs) == SSA_NAME)
1192 /* If the RHS is an SSA_NAME, return its known constant value,
1194 return get_value (rhs)->value;
1206 /* Return the tree representing the element referenced by T if T is an
1207 ARRAY_REF or COMPONENT_REF into constant aggregates. Return
1208 NULL_TREE otherwise. */
1211 fold_const_aggregate_ref (tree t)
1213 prop_value_t *value;
1214 tree base, ctor, idx, field;
1215 unsigned HOST_WIDE_INT cnt;
1218 if (TREE_CODE_CLASS (TREE_CODE (t)) == tcc_declaration)
1219 return get_symbol_constant_value (t);
1221 switch (TREE_CODE (t))
1224 /* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its
1225 DECL_INITIAL. If BASE is a nested reference into another
1226 ARRAY_REF or COMPONENT_REF, make a recursive call to resolve
1227 the inner reference. */
1228 base = TREE_OPERAND (t, 0);
1229 switch (TREE_CODE (base))
1232 if (!TREE_READONLY (base)
1233 || TREE_CODE (TREE_TYPE (base)) != ARRAY_TYPE
1234 || !targetm.binds_local_p (base))
1237 ctor = DECL_INITIAL (base);
1242 ctor = fold_const_aggregate_ref (base);
1254 if (ctor == NULL_TREE
1255 || (TREE_CODE (ctor) != CONSTRUCTOR
1256 && TREE_CODE (ctor) != STRING_CST)
1257 || !TREE_STATIC (ctor))
1260 /* Get the index. If we have an SSA_NAME, try to resolve it
1261 with the current lattice value for the SSA_NAME. */
1262 idx = TREE_OPERAND (t, 1);
1263 switch (TREE_CODE (idx))
1266 if ((value = get_value (idx))
1267 && value->lattice_val == CONSTANT
1268 && TREE_CODE (value->value) == INTEGER_CST)
1281 /* Fold read from constant string. */
1282 if (TREE_CODE (ctor) == STRING_CST)
1284 if ((TYPE_MODE (TREE_TYPE (t))
1285 == TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor))))
1286 && (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor))))
1288 && GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor)))) == 1
1289 && compare_tree_int (idx, TREE_STRING_LENGTH (ctor)) < 0)
1290 return build_int_cst_type (TREE_TYPE (t),
1291 (TREE_STRING_POINTER (ctor)
1292 [TREE_INT_CST_LOW (idx)]));
1296 /* Whoo-hoo! I'll fold ya baby. Yeah! */
1297 FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval)
1298 if (tree_int_cst_equal (cfield, idx))
1300 STRIP_USELESS_TYPE_CONVERSION (cval);
1301 if (TREE_CODE (cval) == ADDR_EXPR)
1303 tree base = get_base_address (TREE_OPERAND (cval, 0));
1304 if (base && TREE_CODE (base) == VAR_DECL)
1305 add_referenced_var (base);
1312 /* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its
1313 DECL_INITIAL. If BASE is a nested reference into another
1314 ARRAY_REF or COMPONENT_REF, make a recursive call to resolve
1315 the inner reference. */
1316 base = TREE_OPERAND (t, 0);
1317 switch (TREE_CODE (base))
1320 if (!TREE_READONLY (base)
1321 || TREE_CODE (TREE_TYPE (base)) != RECORD_TYPE
1322 || !targetm.binds_local_p (base))
1325 ctor = DECL_INITIAL (base);
1330 ctor = fold_const_aggregate_ref (base);
1337 if (ctor == NULL_TREE
1338 || TREE_CODE (ctor) != CONSTRUCTOR
1339 || !TREE_STATIC (ctor))
1342 field = TREE_OPERAND (t, 1);
1344 FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval)
1346 /* FIXME: Handle bit-fields. */
1347 && ! DECL_BIT_FIELD (cfield))
1349 STRIP_USELESS_TYPE_CONVERSION (cval);
1350 if (TREE_CODE (cval) == ADDR_EXPR)
1352 tree base = get_base_address (TREE_OPERAND (cval, 0));
1353 if (base && TREE_CODE (base) == VAR_DECL)
1354 add_referenced_var (base);
1363 tree c = fold_const_aggregate_ref (TREE_OPERAND (t, 0));
1364 if (c && TREE_CODE (c) == COMPLEX_CST)
1365 return fold_build1_loc (EXPR_LOCATION (t),
1366 TREE_CODE (t), TREE_TYPE (t), c);
1372 tree base = TREE_OPERAND (t, 0);
1373 if (TREE_CODE (base) == SSA_NAME
1374 && (value = get_value (base))
1375 && value->lattice_val == CONSTANT
1376 && TREE_CODE (value->value) == ADDR_EXPR
1377 && useless_type_conversion_p (TREE_TYPE (t),
1378 TREE_TYPE (TREE_TYPE (value->value))))
1379 return fold_const_aggregate_ref (TREE_OPERAND (value->value, 0));
1390 /* Evaluate statement STMT.
1391 Valid only for assignments, calls, conditionals, and switches. */
1394 evaluate_stmt (gimple stmt)
1397 tree simplified = NULL_TREE;
1398 ccp_lattice_t likelyvalue = likely_value (stmt);
1401 fold_defer_overflow_warnings ();
1403 /* If the statement is likely to have a CONSTANT result, then try
1404 to fold the statement to determine the constant value. */
1405 /* FIXME. This is the only place that we call ccp_fold.
1406 Since likely_value never returns CONSTANT for calls, we will
1407 not attempt to fold them, including builtins that may profit. */
1408 if (likelyvalue == CONSTANT)
1409 simplified = ccp_fold (stmt);
1410 /* If the statement is likely to have a VARYING result, then do not
1411 bother folding the statement. */
1412 else if (likelyvalue == VARYING)
1414 enum gimple_code code = gimple_code (stmt);
1415 if (code == GIMPLE_ASSIGN)
1417 enum tree_code subcode = gimple_assign_rhs_code (stmt);
1419 /* Other cases cannot satisfy is_gimple_min_invariant
1421 if (get_gimple_rhs_class (subcode) == GIMPLE_SINGLE_RHS)
1422 simplified = gimple_assign_rhs1 (stmt);
1424 else if (code == GIMPLE_SWITCH)
1425 simplified = gimple_switch_index (stmt);
1427 /* These cannot satisfy is_gimple_min_invariant without folding. */
1428 gcc_assert (code == GIMPLE_CALL || code == GIMPLE_COND);
1431 is_constant = simplified && is_gimple_min_invariant (simplified);
1433 fold_undefer_overflow_warnings (is_constant, stmt, 0);
1435 if (dump_file && (dump_flags & TDF_DETAILS))
1437 fprintf (dump_file, "which is likely ");
1438 switch (likelyvalue)
1441 fprintf (dump_file, "CONSTANT");
1444 fprintf (dump_file, "UNDEFINED");
1447 fprintf (dump_file, "VARYING");
1451 fprintf (dump_file, "\n");
1456 /* The statement produced a constant value. */
1457 val.lattice_val = CONSTANT;
1458 val.value = simplified;
1462 /* The statement produced a nonconstant value. If the statement
1463 had UNDEFINED operands, then the result of the statement
1464 should be UNDEFINED. Otherwise, the statement is VARYING. */
1465 if (likelyvalue == UNDEFINED)
1466 val.lattice_val = likelyvalue;
1468 val.lattice_val = VARYING;
1470 val.value = NULL_TREE;
1476 /* Fold the stmt at *GSI with CCP specific information that propagating
1477 and regular folding does not catch. */
1480 ccp_fold_stmt (gimple_stmt_iterator *gsi)
1482 gimple stmt = gsi_stmt (*gsi);
1484 switch (gimple_code (stmt))
1489 /* Statement evaluation will handle type mismatches in constants
1490 more gracefully than the final propagation. This allows us to
1491 fold more conditionals here. */
1492 val = evaluate_stmt (stmt);
1493 if (val.lattice_val != CONSTANT
1494 || TREE_CODE (val.value) != INTEGER_CST)
1497 if (integer_zerop (val.value))
1498 gimple_cond_make_false (stmt);
1500 gimple_cond_make_true (stmt);
1507 tree lhs = gimple_call_lhs (stmt);
1510 bool changed = false;
1513 /* If the call was folded into a constant make sure it goes
1514 away even if we cannot propagate into all uses because of
1517 && TREE_CODE (lhs) == SSA_NAME
1518 && (val = get_value (lhs))
1519 && val->lattice_val == CONSTANT)
1521 tree new_rhs = unshare_expr (val->value);
1523 if (!useless_type_conversion_p (TREE_TYPE (lhs),
1524 TREE_TYPE (new_rhs)))
1525 new_rhs = fold_convert (TREE_TYPE (lhs), new_rhs);
1526 res = update_call_from_tree (gsi, new_rhs);
1531 /* Propagate into the call arguments. Compared to replace_uses_in
1532 this can use the argument slot types for type verification
1533 instead of the current argument type. We also can safely
1534 drop qualifiers here as we are dealing with constants anyway. */
1535 argt = TYPE_ARG_TYPES (TREE_TYPE (TREE_TYPE (gimple_call_fn (stmt))));
1536 for (i = 0; i < gimple_call_num_args (stmt) && argt;
1537 ++i, argt = TREE_CHAIN (argt))
1539 tree arg = gimple_call_arg (stmt, i);
1540 if (TREE_CODE (arg) == SSA_NAME
1541 && (val = get_value (arg))
1542 && val->lattice_val == CONSTANT
1543 && useless_type_conversion_p
1544 (TYPE_MAIN_VARIANT (TREE_VALUE (argt)),
1545 TYPE_MAIN_VARIANT (TREE_TYPE (val->value))))
1547 gimple_call_set_arg (stmt, i, unshare_expr (val->value));
1560 /* Visit the assignment statement STMT. Set the value of its LHS to the
1561 value computed by the RHS and store LHS in *OUTPUT_P. If STMT
1562 creates virtual definitions, set the value of each new name to that
1563 of the RHS (if we can derive a constant out of the RHS).
1564 Value-returning call statements also perform an assignment, and
1565 are handled here. */
1567 static enum ssa_prop_result
1568 visit_assignment (gimple stmt, tree *output_p)
1571 enum ssa_prop_result retval;
1573 tree lhs = gimple_get_lhs (stmt);
1575 gcc_assert (gimple_code (stmt) != GIMPLE_CALL
1576 || gimple_call_lhs (stmt) != NULL_TREE);
1578 if (gimple_assign_copy_p (stmt))
1580 tree rhs = gimple_assign_rhs1 (stmt);
1582 if (TREE_CODE (rhs) == SSA_NAME)
1584 /* For a simple copy operation, we copy the lattice values. */
1585 prop_value_t *nval = get_value (rhs);
1589 val = evaluate_stmt (stmt);
1592 /* Evaluate the statement, which could be
1593 either a GIMPLE_ASSIGN or a GIMPLE_CALL. */
1594 val = evaluate_stmt (stmt);
1596 retval = SSA_PROP_NOT_INTERESTING;
1598 /* Set the lattice value of the statement's output. */
1599 if (TREE_CODE (lhs) == SSA_NAME)
1601 /* If STMT is an assignment to an SSA_NAME, we only have one
1603 if (set_lattice_value (lhs, val))
1606 if (val.lattice_val == VARYING)
1607 retval = SSA_PROP_VARYING;
1609 retval = SSA_PROP_INTERESTING;
1617 /* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING
1618 if it can determine which edge will be taken. Otherwise, return
1619 SSA_PROP_VARYING. */
1621 static enum ssa_prop_result
1622 visit_cond_stmt (gimple stmt, edge *taken_edge_p)
1627 block = gimple_bb (stmt);
1628 val = evaluate_stmt (stmt);
1630 /* Find which edge out of the conditional block will be taken and add it
1631 to the worklist. If no single edge can be determined statically,
1632 return SSA_PROP_VARYING to feed all the outgoing edges to the
1633 propagation engine. */
1634 *taken_edge_p = val.value ? find_taken_edge (block, val.value) : 0;
1636 return SSA_PROP_INTERESTING;
1638 return SSA_PROP_VARYING;
1642 /* Evaluate statement STMT. If the statement produces an output value and
1643 its evaluation changes the lattice value of its output, return
1644 SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the
1647 If STMT is a conditional branch and we can determine its truth
1648 value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying
1649 value, return SSA_PROP_VARYING. */
1651 static enum ssa_prop_result
1652 ccp_visit_stmt (gimple stmt, edge *taken_edge_p, tree *output_p)
1657 if (dump_file && (dump_flags & TDF_DETAILS))
1659 fprintf (dump_file, "\nVisiting statement:\n");
1660 print_gimple_stmt (dump_file, stmt, 0, dump_flags);
1663 switch (gimple_code (stmt))
1666 /* If the statement is an assignment that produces a single
1667 output value, evaluate its RHS to see if the lattice value of
1668 its output has changed. */
1669 return visit_assignment (stmt, output_p);
1672 /* A value-returning call also performs an assignment. */
1673 if (gimple_call_lhs (stmt) != NULL_TREE)
1674 return visit_assignment (stmt, output_p);
1679 /* If STMT is a conditional branch, see if we can determine
1680 which branch will be taken. */
1681 /* FIXME. It appears that we should be able to optimize
1682 computed GOTOs here as well. */
1683 return visit_cond_stmt (stmt, taken_edge_p);
1689 /* Any other kind of statement is not interesting for constant
1690 propagation and, therefore, not worth simulating. */
1691 if (dump_file && (dump_flags & TDF_DETAILS))
1692 fprintf (dump_file, "No interesting values produced. Marked VARYING.\n");
1694 /* Definitions made by statements other than assignments to
1695 SSA_NAMEs represent unknown modifications to their outputs.
1696 Mark them VARYING. */
1697 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
1699 prop_value_t v = { VARYING, NULL_TREE };
1700 set_lattice_value (def, v);
1703 return SSA_PROP_VARYING;
1707 /* Main entry point for SSA Conditional Constant Propagation. */
1713 ssa_propagate (ccp_visit_stmt, ccp_visit_phi_node);
1714 if (ccp_finalize ())
1715 return (TODO_cleanup_cfg | TODO_update_ssa | TODO_remove_unused_locals);
1724 return flag_tree_ccp != 0;
1728 struct gimple_opt_pass pass_ccp =
1733 gate_ccp, /* gate */
1734 do_ssa_ccp, /* execute */
1737 0, /* static_pass_number */
1738 TV_TREE_CCP, /* tv_id */
1739 PROP_cfg | PROP_ssa, /* properties_required */
1740 0, /* properties_provided */
1741 0, /* properties_destroyed */
1742 0, /* todo_flags_start */
1743 TODO_dump_func | TODO_verify_ssa
1744 | TODO_verify_stmts | TODO_ggc_collect/* todo_flags_finish */
1749 /* A subroutine of fold_stmt. Attempts to fold *(A+O) to A[X].
1750 BASE is an array type. OFFSET is a byte displacement. ORIG_TYPE
1751 is the desired result type.
1753 LOC is the location of the original expression. */
1756 maybe_fold_offset_to_array_ref (location_t loc, tree base, tree offset,
1758 bool allow_negative_idx)
1760 tree min_idx, idx, idx_type, elt_offset = integer_zero_node;
1761 tree array_type, elt_type, elt_size;
1764 /* If BASE is an ARRAY_REF, we can pick up another offset (this time
1765 measured in units of the size of elements type) from that ARRAY_REF).
1766 We can't do anything if either is variable.
1768 The case we handle here is *(&A[N]+O). */
1769 if (TREE_CODE (base) == ARRAY_REF)
1771 tree low_bound = array_ref_low_bound (base);
1773 elt_offset = TREE_OPERAND (base, 1);
1774 if (TREE_CODE (low_bound) != INTEGER_CST
1775 || TREE_CODE (elt_offset) != INTEGER_CST)
1778 elt_offset = int_const_binop (MINUS_EXPR, elt_offset, low_bound, 0);
1779 base = TREE_OPERAND (base, 0);
1782 /* Ignore stupid user tricks of indexing non-array variables. */
1783 array_type = TREE_TYPE (base);
1784 if (TREE_CODE (array_type) != ARRAY_TYPE)
1786 elt_type = TREE_TYPE (array_type);
1787 if (!useless_type_conversion_p (orig_type, elt_type))
1790 /* Use signed size type for intermediate computation on the index. */
1791 idx_type = signed_type_for (size_type_node);
1793 /* If OFFSET and ELT_OFFSET are zero, we don't care about the size of the
1794 element type (so we can use the alignment if it's not constant).
1795 Otherwise, compute the offset as an index by using a division. If the
1796 division isn't exact, then don't do anything. */
1797 elt_size = TYPE_SIZE_UNIT (elt_type);
1800 if (integer_zerop (offset))
1802 if (TREE_CODE (elt_size) != INTEGER_CST)
1803 elt_size = size_int (TYPE_ALIGN (elt_type));
1805 idx = build_int_cst (idx_type, 0);
1809 unsigned HOST_WIDE_INT lquo, lrem;
1810 HOST_WIDE_INT hquo, hrem;
1813 /* The final array offset should be signed, so we need
1814 to sign-extend the (possibly pointer) offset here
1815 and use signed division. */
1816 soffset = double_int_sext (tree_to_double_int (offset),
1817 TYPE_PRECISION (TREE_TYPE (offset)));
1818 if (TREE_CODE (elt_size) != INTEGER_CST
1819 || div_and_round_double (TRUNC_DIV_EXPR, 0,
1820 soffset.low, soffset.high,
1821 TREE_INT_CST_LOW (elt_size),
1822 TREE_INT_CST_HIGH (elt_size),
1823 &lquo, &hquo, &lrem, &hrem)
1827 idx = build_int_cst_wide (idx_type, lquo, hquo);
1830 /* Assume the low bound is zero. If there is a domain type, get the
1831 low bound, if any, convert the index into that type, and add the
1833 min_idx = build_int_cst (idx_type, 0);
1834 domain_type = TYPE_DOMAIN (array_type);
1837 idx_type = domain_type;
1838 if (TYPE_MIN_VALUE (idx_type))
1839 min_idx = TYPE_MIN_VALUE (idx_type);
1841 min_idx = fold_convert (idx_type, min_idx);
1843 if (TREE_CODE (min_idx) != INTEGER_CST)
1846 elt_offset = fold_convert (idx_type, elt_offset);
1849 if (!integer_zerop (min_idx))
1850 idx = int_const_binop (PLUS_EXPR, idx, min_idx, 0);
1851 if (!integer_zerop (elt_offset))
1852 idx = int_const_binop (PLUS_EXPR, idx, elt_offset, 0);
1854 /* Make sure to possibly truncate late after offsetting. */
1855 idx = fold_convert (idx_type, idx);
1857 /* We don't want to construct access past array bounds. For example
1860 should not be simplified into (*c)[14] or tree-vrp will
1861 give false warnings. The same is true for
1862 struct A { long x; char d[0]; } *a;
1864 which should be not folded to &a->d[-8]. */
1866 && TYPE_MAX_VALUE (domain_type)
1867 && TREE_CODE (TYPE_MAX_VALUE (domain_type)) == INTEGER_CST)
1869 tree up_bound = TYPE_MAX_VALUE (domain_type);
1871 if (tree_int_cst_lt (up_bound, idx)
1872 /* Accesses after the end of arrays of size 0 (gcc
1873 extension) and 1 are likely intentional ("struct
1875 && compare_tree_int (up_bound, 1) > 0)
1879 && TYPE_MIN_VALUE (domain_type))
1881 if (!allow_negative_idx
1882 && TREE_CODE (TYPE_MIN_VALUE (domain_type)) == INTEGER_CST
1883 && tree_int_cst_lt (idx, TYPE_MIN_VALUE (domain_type)))
1886 else if (!allow_negative_idx
1887 && compare_tree_int (idx, 0) < 0)
1891 tree t = build4 (ARRAY_REF, elt_type, base, idx, NULL_TREE, NULL_TREE);
1892 SET_EXPR_LOCATION (t, loc);
1898 /* Attempt to fold *(S+O) to S.X.
1899 BASE is a record type. OFFSET is a byte displacement. ORIG_TYPE
1900 is the desired result type.
1902 LOC is the location of the original expression. */
1905 maybe_fold_offset_to_component_ref (location_t loc, tree record_type,
1906 tree base, tree offset, tree orig_type)
1908 tree f, t, field_type, tail_array_field, field_offset;
1912 if (TREE_CODE (record_type) != RECORD_TYPE
1913 && TREE_CODE (record_type) != UNION_TYPE
1914 && TREE_CODE (record_type) != QUAL_UNION_TYPE)
1917 /* Short-circuit silly cases. */
1918 if (useless_type_conversion_p (record_type, orig_type))
1921 tail_array_field = NULL_TREE;
1922 for (f = TYPE_FIELDS (record_type); f ; f = TREE_CHAIN (f))
1926 if (TREE_CODE (f) != FIELD_DECL)
1928 if (DECL_BIT_FIELD (f))
1931 if (!DECL_FIELD_OFFSET (f))
1933 field_offset = byte_position (f);
1934 if (TREE_CODE (field_offset) != INTEGER_CST)
1937 /* ??? Java creates "interesting" fields for representing base classes.
1938 They have no name, and have no context. With no context, we get into
1939 trouble with nonoverlapping_component_refs_p. Skip them. */
1940 if (!DECL_FIELD_CONTEXT (f))
1943 /* The previous array field isn't at the end. */
1944 tail_array_field = NULL_TREE;
1946 /* Check to see if this offset overlaps with the field. */
1947 cmp = tree_int_cst_compare (field_offset, offset);
1951 field_type = TREE_TYPE (f);
1953 /* Here we exactly match the offset being checked. If the types match,
1954 then we can return that field. */
1956 && useless_type_conversion_p (orig_type, field_type))
1958 t = build3 (COMPONENT_REF, field_type, base, f, NULL_TREE);
1962 /* Don't care about offsets into the middle of scalars. */
1963 if (!AGGREGATE_TYPE_P (field_type))
1966 /* Check for array at the end of the struct. This is often
1967 used as for flexible array members. We should be able to
1968 turn this into an array access anyway. */
1969 if (TREE_CODE (field_type) == ARRAY_TYPE)
1970 tail_array_field = f;
1972 /* Check the end of the field against the offset. */
1973 if (!DECL_SIZE_UNIT (f)
1974 || TREE_CODE (DECL_SIZE_UNIT (f)) != INTEGER_CST)
1976 t = int_const_binop (MINUS_EXPR, offset, field_offset, 1);
1977 if (!tree_int_cst_lt (t, DECL_SIZE_UNIT (f)))
1980 /* If we matched, then set offset to the displacement into
1982 new_base = build3 (COMPONENT_REF, field_type, base, f, NULL_TREE);
1983 SET_EXPR_LOCATION (new_base, loc);
1985 /* Recurse to possibly find the match. */
1986 ret = maybe_fold_offset_to_array_ref (loc, new_base, t, orig_type,
1987 f == TYPE_FIELDS (record_type));
1990 ret = maybe_fold_offset_to_component_ref (loc, field_type, new_base, t,
1996 if (!tail_array_field)
1999 f = tail_array_field;
2000 field_type = TREE_TYPE (f);
2001 offset = int_const_binop (MINUS_EXPR, offset, byte_position (f), 1);
2003 /* If we get here, we've got an aggregate field, and a possibly
2004 nonzero offset into them. Recurse and hope for a valid match. */
2005 base = build3 (COMPONENT_REF, field_type, base, f, NULL_TREE);
2006 SET_EXPR_LOCATION (base, loc);
2008 t = maybe_fold_offset_to_array_ref (loc, base, offset, orig_type,
2009 f == TYPE_FIELDS (record_type));
2012 return maybe_fold_offset_to_component_ref (loc, field_type, base, offset,
2016 /* Attempt to express (ORIG_TYPE)BASE+OFFSET as BASE->field_of_orig_type
2017 or BASE[index] or by combination of those.
2019 LOC is the location of original expression.
2021 Before attempting the conversion strip off existing ADDR_EXPRs and
2022 handled component refs. */
2025 maybe_fold_offset_to_reference (location_t loc, tree base, tree offset,
2032 if (TREE_CODE (base) != ADDR_EXPR)
2035 base = TREE_OPERAND (base, 0);
2037 /* Handle case where existing COMPONENT_REF pick e.g. wrong field of union,
2038 so it needs to be removed and new COMPONENT_REF constructed.
2039 The wrong COMPONENT_REF are often constructed by folding the
2040 (type *)&object within the expression (type *)&object+offset */
2041 if (handled_component_p (base))
2043 HOST_WIDE_INT sub_offset, size, maxsize;
2045 newbase = get_ref_base_and_extent (base, &sub_offset,
2047 gcc_assert (newbase);
2050 && !(sub_offset & (BITS_PER_UNIT - 1)))
2054 offset = int_const_binop (PLUS_EXPR, offset,
2055 build_int_cst (TREE_TYPE (offset),
2056 sub_offset / BITS_PER_UNIT), 1);
2059 if (useless_type_conversion_p (orig_type, TREE_TYPE (base))
2060 && integer_zerop (offset))
2062 type = TREE_TYPE (base);
2064 ret = maybe_fold_offset_to_component_ref (loc, type, base, offset, orig_type);
2066 ret = maybe_fold_offset_to_array_ref (loc, base, offset, orig_type, true);
2071 /* Attempt to express (ORIG_TYPE)&BASE+OFFSET as &BASE->field_of_orig_type
2072 or &BASE[index] or by combination of those.
2074 LOC is the location of the original expression.
2076 Before attempting the conversion strip off existing component refs. */
2079 maybe_fold_offset_to_address (location_t loc, tree addr, tree offset,
2084 gcc_assert (POINTER_TYPE_P (TREE_TYPE (addr))
2085 && POINTER_TYPE_P (orig_type));
2087 t = maybe_fold_offset_to_reference (loc, addr, offset,
2088 TREE_TYPE (orig_type));
2094 /* For __builtin_object_size to function correctly we need to
2095 make sure not to fold address arithmetic so that we change
2096 reference from one array to another. This would happen for
2099 struct X { char s1[10]; char s2[10] } s;
2100 char *foo (void) { return &s.s2[-4]; }
2102 where we need to avoid generating &s.s1[6]. As the C and
2103 C++ frontends create different initial trees
2104 (char *) &s.s1 + -4 vs. &s.s1[-4] we have to do some
2105 sophisticated comparisons here. Note that checking for the
2106 condition after the fact is easier than trying to avoid doing
2109 if (TREE_CODE (orig) == ADDR_EXPR)
2110 orig = TREE_OPERAND (orig, 0);
2111 if ((TREE_CODE (orig) == ARRAY_REF
2112 || (TREE_CODE (orig) == COMPONENT_REF
2113 && TREE_CODE (TREE_TYPE (TREE_OPERAND (orig, 1))) == ARRAY_TYPE))
2114 && (TREE_CODE (t) == ARRAY_REF
2115 || TREE_CODE (t) == COMPONENT_REF)
2116 && !operand_equal_p (TREE_CODE (orig) == ARRAY_REF
2117 ? TREE_OPERAND (orig, 0) : orig,
2118 TREE_CODE (t) == ARRAY_REF
2119 ? TREE_OPERAND (t, 0) : t, 0))
2122 ptr_type = build_pointer_type (TREE_TYPE (t));
2123 if (!useless_type_conversion_p (orig_type, ptr_type))
2125 return build_fold_addr_expr_with_type_loc (loc, t, ptr_type);
2131 /* A subroutine of fold_stmt. Attempt to simplify *(BASE+OFFSET).
2132 Return the simplified expression, or NULL if nothing could be done. */
2135 maybe_fold_stmt_indirect (tree expr, tree base, tree offset)
2138 bool volatile_p = TREE_THIS_VOLATILE (expr);
2139 location_t loc = EXPR_LOCATION (expr);
2141 /* We may well have constructed a double-nested PLUS_EXPR via multiple
2142 substitutions. Fold that down to one. Remove NON_LVALUE_EXPRs that
2143 are sometimes added. */
2145 STRIP_TYPE_NOPS (base);
2146 TREE_OPERAND (expr, 0) = base;
2148 /* One possibility is that the address reduces to a string constant. */
2149 t = fold_read_from_constant_string (expr);
2153 /* Add in any offset from a POINTER_PLUS_EXPR. */
2154 if (TREE_CODE (base) == POINTER_PLUS_EXPR)
2158 offset2 = TREE_OPERAND (base, 1);
2159 if (TREE_CODE (offset2) != INTEGER_CST)
2161 base = TREE_OPERAND (base, 0);
2163 offset = fold_convert (sizetype,
2164 int_const_binop (PLUS_EXPR, offset, offset2, 1));
2167 if (TREE_CODE (base) == ADDR_EXPR)
2169 tree base_addr = base;
2171 /* Strip the ADDR_EXPR. */
2172 base = TREE_OPERAND (base, 0);
2174 /* Fold away CONST_DECL to its value, if the type is scalar. */
2175 if (TREE_CODE (base) == CONST_DECL
2176 && is_gimple_min_invariant (DECL_INITIAL (base)))
2177 return DECL_INITIAL (base);
2179 /* If there is no offset involved simply return the folded base. */
2180 if (integer_zerop (offset))
2183 /* Try folding *(&B+O) to B.X. */
2184 t = maybe_fold_offset_to_reference (loc, base_addr, offset,
2188 /* Preserve volatileness of the original expression.
2189 We can end up with a plain decl here which is shared
2190 and we shouldn't mess with its flags. */
2192 TREE_THIS_VOLATILE (t) = volatile_p;
2198 /* We can get here for out-of-range string constant accesses,
2199 such as "_"[3]. Bail out of the entire substitution search
2200 and arrange for the entire statement to be replaced by a
2201 call to __builtin_trap. In all likelihood this will all be
2202 constant-folded away, but in the meantime we can't leave with
2203 something that get_expr_operands can't understand. */
2207 if (TREE_CODE (t) == ADDR_EXPR
2208 && TREE_CODE (TREE_OPERAND (t, 0)) == STRING_CST)
2210 /* FIXME: Except that this causes problems elsewhere with dead
2211 code not being deleted, and we die in the rtl expanders
2212 because we failed to remove some ssa_name. In the meantime,
2213 just return zero. */
2214 /* FIXME2: This condition should be signaled by
2215 fold_read_from_constant_string directly, rather than
2216 re-checking for it here. */
2217 return integer_zero_node;
2220 /* Try folding *(B+O) to B->X. Still an improvement. */
2221 if (POINTER_TYPE_P (TREE_TYPE (base)))
2223 t = maybe_fold_offset_to_reference (loc, base, offset,
2230 /* Otherwise we had an offset that we could not simplify. */
2235 /* A quaint feature extant in our address arithmetic is that there
2236 can be hidden type changes here. The type of the result need
2237 not be the same as the type of the input pointer.
2239 What we're after here is an expression of the form
2240 (T *)(&array + const)
2241 where array is OP0, const is OP1, RES_TYPE is T and
2242 the cast doesn't actually exist, but is implicit in the
2243 type of the POINTER_PLUS_EXPR. We'd like to turn this into
2245 which may be able to propagate further. */
2248 maybe_fold_stmt_addition (location_t loc, tree res_type, tree op0, tree op1)
2253 /* The first operand should be an ADDR_EXPR. */
2254 if (TREE_CODE (op0) != ADDR_EXPR)
2256 op0 = TREE_OPERAND (op0, 0);
2258 /* It had better be a constant. */
2259 if (TREE_CODE (op1) != INTEGER_CST)
2261 /* Or op0 should now be A[0] and the non-constant offset defined
2262 via a multiplication by the array element size. */
2263 if (TREE_CODE (op0) == ARRAY_REF
2264 && integer_zerop (TREE_OPERAND (op0, 1))
2265 && TREE_CODE (op1) == SSA_NAME
2266 && host_integerp (TYPE_SIZE_UNIT (TREE_TYPE (op0)), 1))
2268 gimple offset_def = SSA_NAME_DEF_STMT (op1);
2269 if (!is_gimple_assign (offset_def))
2272 if (gimple_assign_rhs_code (offset_def) == MULT_EXPR
2273 && TREE_CODE (gimple_assign_rhs2 (offset_def)) == INTEGER_CST
2274 && tree_int_cst_equal (gimple_assign_rhs2 (offset_def),
2275 TYPE_SIZE_UNIT (TREE_TYPE (op0))))
2276 return build_fold_addr_expr
2277 (build4 (ARRAY_REF, TREE_TYPE (op0),
2278 TREE_OPERAND (op0, 0),
2279 gimple_assign_rhs1 (offset_def),
2280 TREE_OPERAND (op0, 2),
2281 TREE_OPERAND (op0, 3)));
2282 else if (integer_onep (TYPE_SIZE_UNIT (TREE_TYPE (op0)))
2283 && gimple_assign_rhs_code (offset_def) != MULT_EXPR)
2284 return build_fold_addr_expr
2285 (build4 (ARRAY_REF, TREE_TYPE (op0),
2286 TREE_OPERAND (op0, 0),
2288 TREE_OPERAND (op0, 2),
2289 TREE_OPERAND (op0, 3)));
2294 /* If the first operand is an ARRAY_REF, expand it so that we can fold
2295 the offset into it. */
2296 while (TREE_CODE (op0) == ARRAY_REF)
2298 tree array_obj = TREE_OPERAND (op0, 0);
2299 tree array_idx = TREE_OPERAND (op0, 1);
2300 tree elt_type = TREE_TYPE (op0);
2301 tree elt_size = TYPE_SIZE_UNIT (elt_type);
2304 if (TREE_CODE (array_idx) != INTEGER_CST)
2306 if (TREE_CODE (elt_size) != INTEGER_CST)
2309 /* Un-bias the index by the min index of the array type. */
2310 min_idx = TYPE_DOMAIN (TREE_TYPE (array_obj));
2313 min_idx = TYPE_MIN_VALUE (min_idx);
2316 if (TREE_CODE (min_idx) != INTEGER_CST)
2319 array_idx = fold_convert (TREE_TYPE (min_idx), array_idx);
2320 if (!integer_zerop (min_idx))
2321 array_idx = int_const_binop (MINUS_EXPR, array_idx,
2326 /* Convert the index to a byte offset. */
2327 array_idx = fold_convert (sizetype, array_idx);
2328 array_idx = int_const_binop (MULT_EXPR, array_idx, elt_size, 0);
2330 /* Update the operands for the next round, or for folding. */
2331 op1 = int_const_binop (PLUS_EXPR,
2336 ptd_type = TREE_TYPE (res_type);
2337 /* If we want a pointer to void, reconstruct the reference from the
2338 array element type. A pointer to that can be trivially converted
2339 to void *. This happens as we fold (void *)(ptr p+ off). */
2340 if (VOID_TYPE_P (ptd_type)
2341 && TREE_CODE (TREE_TYPE (op0)) == ARRAY_TYPE)
2342 ptd_type = TREE_TYPE (TREE_TYPE (op0));
2344 /* At which point we can try some of the same things as for indirects. */
2345 t = maybe_fold_offset_to_array_ref (loc, op0, op1, ptd_type, true);
2347 t = maybe_fold_offset_to_component_ref (loc, TREE_TYPE (op0), op0, op1,
2351 t = build1 (ADDR_EXPR, res_type, t);
2352 SET_EXPR_LOCATION (t, loc);
2358 /* Subroutine of fold_stmt. We perform several simplifications of the
2359 memory reference tree EXPR and make sure to re-gimplify them properly
2360 after propagation of constant addresses. IS_LHS is true if the
2361 reference is supposed to be an lvalue. */
2364 maybe_fold_reference (tree expr, bool is_lhs)
2368 if (TREE_CODE (expr) == ARRAY_REF
2371 tree tem = fold_read_from_constant_string (expr);
2376 /* ??? We might want to open-code the relevant remaining cases
2377 to avoid using the generic fold. */
2378 if (handled_component_p (*t)
2379 && CONSTANT_CLASS_P (TREE_OPERAND (*t, 0)))
2381 tree tem = fold (*t);
2386 while (handled_component_p (*t))
2387 t = &TREE_OPERAND (*t, 0);
2389 if (TREE_CODE (*t) == INDIRECT_REF)
2391 tree tem = maybe_fold_stmt_indirect (*t, TREE_OPERAND (*t, 0),
2393 /* Avoid folding *"abc" = 5 into 'a' = 5. */
2394 if (is_lhs && tem && CONSTANT_CLASS_P (tem))
2397 && TREE_CODE (TREE_OPERAND (*t, 0)) == ADDR_EXPR)
2398 /* If we had a good reason for propagating the address here,
2399 make sure we end up with valid gimple. See PR34989. */
2400 tem = TREE_OPERAND (TREE_OPERAND (*t, 0), 0);
2405 tem = maybe_fold_reference (expr, is_lhs);
2414 tree tem = get_symbol_constant_value (*t);
2418 tem = maybe_fold_reference (expr, is_lhs);
2429 /* Return the string length, maximum string length or maximum value of
2431 If ARG is an SSA name variable, follow its use-def chains. If LENGTH
2432 is not NULL and, for TYPE == 0, its value is not equal to the length
2433 we determine or if we are unable to determine the length or value,
2434 return false. VISITED is a bitmap of visited variables.
2435 TYPE is 0 if string length should be returned, 1 for maximum string
2436 length and 2 for maximum value ARG can have. */
2439 get_maxval_strlen (tree arg, tree *length, bitmap visited, int type)
2444 if (TREE_CODE (arg) != SSA_NAME)
2446 if (TREE_CODE (arg) == COND_EXPR)
2447 return get_maxval_strlen (COND_EXPR_THEN (arg), length, visited, type)
2448 && get_maxval_strlen (COND_EXPR_ELSE (arg), length, visited, type);
2449 /* We can end up with &(*iftmp_1)[0] here as well, so handle it. */
2450 else if (TREE_CODE (arg) == ADDR_EXPR
2451 && TREE_CODE (TREE_OPERAND (arg, 0)) == ARRAY_REF
2452 && integer_zerop (TREE_OPERAND (TREE_OPERAND (arg, 0), 1)))
2454 tree aop0 = TREE_OPERAND (TREE_OPERAND (arg, 0), 0);
2455 if (TREE_CODE (aop0) == INDIRECT_REF
2456 && TREE_CODE (TREE_OPERAND (aop0, 0)) == SSA_NAME)
2457 return get_maxval_strlen (TREE_OPERAND (aop0, 0),
2458 length, visited, type);
2464 if (TREE_CODE (val) != INTEGER_CST
2465 || tree_int_cst_sgn (val) < 0)
2469 val = c_strlen (arg, 1);
2477 if (TREE_CODE (*length) != INTEGER_CST
2478 || TREE_CODE (val) != INTEGER_CST)
2481 if (tree_int_cst_lt (*length, val))
2485 else if (simple_cst_equal (val, *length) != 1)
2493 /* If we were already here, break the infinite cycle. */
2494 if (bitmap_bit_p (visited, SSA_NAME_VERSION (arg)))
2496 bitmap_set_bit (visited, SSA_NAME_VERSION (arg));
2499 def_stmt = SSA_NAME_DEF_STMT (var);
2501 switch (gimple_code (def_stmt))
2504 /* The RHS of the statement defining VAR must either have a
2505 constant length or come from another SSA_NAME with a constant
2507 if (gimple_assign_single_p (def_stmt)
2508 || gimple_assign_unary_nop_p (def_stmt))
2510 tree rhs = gimple_assign_rhs1 (def_stmt);
2511 return get_maxval_strlen (rhs, length, visited, type);
2517 /* All the arguments of the PHI node must have the same constant
2521 for (i = 0; i < gimple_phi_num_args (def_stmt); i++)
2523 tree arg = gimple_phi_arg (def_stmt, i)->def;
2525 /* If this PHI has itself as an argument, we cannot
2526 determine the string length of this argument. However,
2527 if we can find a constant string length for the other
2528 PHI args then we can still be sure that this is a
2529 constant string length. So be optimistic and just
2530 continue with the next argument. */
2531 if (arg == gimple_phi_result (def_stmt))
2534 if (!get_maxval_strlen (arg, length, visited, type))
2546 /* Fold builtin call in statement STMT. Returns a simplified tree.
2547 We may return a non-constant expression, including another call
2548 to a different function and with different arguments, e.g.,
2549 substituting memcpy for strcpy when the string length is known.
2550 Note that some builtins expand into inline code that may not
2551 be valid in GIMPLE. Callers must take care. */
2554 ccp_fold_builtin (gimple stmt)
2556 tree result, val[3];
2562 location_t loc = gimple_location (stmt);
2564 gcc_assert (is_gimple_call (stmt));
2566 ignore = (gimple_call_lhs (stmt) == NULL);
2568 /* First try the generic builtin folder. If that succeeds, return the
2570 result = fold_call_stmt (stmt, ignore);
2574 STRIP_NOPS (result);
2578 /* Ignore MD builtins. */
2579 callee = gimple_call_fndecl (stmt);
2580 if (DECL_BUILT_IN_CLASS (callee) == BUILT_IN_MD)
2583 /* If the builtin could not be folded, and it has no argument list,
2585 nargs = gimple_call_num_args (stmt);
2589 /* Limit the work only for builtins we know how to simplify. */
2590 switch (DECL_FUNCTION_CODE (callee))
2592 case BUILT_IN_STRLEN:
2593 case BUILT_IN_FPUTS:
2594 case BUILT_IN_FPUTS_UNLOCKED:
2598 case BUILT_IN_STRCPY:
2599 case BUILT_IN_STRNCPY:
2603 case BUILT_IN_MEMCPY_CHK:
2604 case BUILT_IN_MEMPCPY_CHK:
2605 case BUILT_IN_MEMMOVE_CHK:
2606 case BUILT_IN_MEMSET_CHK:
2607 case BUILT_IN_STRNCPY_CHK:
2611 case BUILT_IN_STRCPY_CHK:
2612 case BUILT_IN_STPCPY_CHK:
2616 case BUILT_IN_SNPRINTF_CHK:
2617 case BUILT_IN_VSNPRINTF_CHK:
2625 if (arg_idx >= nargs)
2628 /* Try to use the dataflow information gathered by the CCP process. */
2629 visited = BITMAP_ALLOC (NULL);
2630 bitmap_clear (visited);
2632 memset (val, 0, sizeof (val));
2633 a = gimple_call_arg (stmt, arg_idx);
2634 if (!get_maxval_strlen (a, &val[arg_idx], visited, type))
2635 val[arg_idx] = NULL_TREE;
2637 BITMAP_FREE (visited);
2640 switch (DECL_FUNCTION_CODE (callee))
2642 case BUILT_IN_STRLEN:
2643 if (val[0] && nargs == 1)
2646 fold_convert (TREE_TYPE (gimple_call_lhs (stmt)), val[0]);
2648 /* If the result is not a valid gimple value, or not a cast
2649 of a valid gimple value, then we can not use the result. */
2650 if (is_gimple_val (new_val)
2651 || (is_gimple_cast (new_val)
2652 && is_gimple_val (TREE_OPERAND (new_val, 0))))
2657 case BUILT_IN_STRCPY:
2658 if (val[1] && is_gimple_val (val[1]) && nargs == 2)
2659 result = fold_builtin_strcpy (loc, callee,
2660 gimple_call_arg (stmt, 0),
2661 gimple_call_arg (stmt, 1),
2665 case BUILT_IN_STRNCPY:
2666 if (val[1] && is_gimple_val (val[1]) && nargs == 3)
2667 result = fold_builtin_strncpy (loc, callee,
2668 gimple_call_arg (stmt, 0),
2669 gimple_call_arg (stmt, 1),
2670 gimple_call_arg (stmt, 2),
2674 case BUILT_IN_FPUTS:
2676 result = fold_builtin_fputs (loc, gimple_call_arg (stmt, 0),
2677 gimple_call_arg (stmt, 1),
2678 ignore, false, val[0]);
2681 case BUILT_IN_FPUTS_UNLOCKED:
2683 result = fold_builtin_fputs (loc, gimple_call_arg (stmt, 0),
2684 gimple_call_arg (stmt, 1),
2685 ignore, true, val[0]);
2688 case BUILT_IN_MEMCPY_CHK:
2689 case BUILT_IN_MEMPCPY_CHK:
2690 case BUILT_IN_MEMMOVE_CHK:
2691 case BUILT_IN_MEMSET_CHK:
2692 if (val[2] && is_gimple_val (val[2]) && nargs == 4)
2693 result = fold_builtin_memory_chk (loc, callee,
2694 gimple_call_arg (stmt, 0),
2695 gimple_call_arg (stmt, 1),
2696 gimple_call_arg (stmt, 2),
2697 gimple_call_arg (stmt, 3),
2699 DECL_FUNCTION_CODE (callee));
2702 case BUILT_IN_STRCPY_CHK:
2703 case BUILT_IN_STPCPY_CHK:
2704 if (val[1] && is_gimple_val (val[1]) && nargs == 3)
2705 result = fold_builtin_stxcpy_chk (loc, callee,
2706 gimple_call_arg (stmt, 0),
2707 gimple_call_arg (stmt, 1),
2708 gimple_call_arg (stmt, 2),
2710 DECL_FUNCTION_CODE (callee));
2713 case BUILT_IN_STRNCPY_CHK:
2714 if (val[2] && is_gimple_val (val[2]) && nargs == 4)
2715 result = fold_builtin_strncpy_chk (loc, gimple_call_arg (stmt, 0),
2716 gimple_call_arg (stmt, 1),
2717 gimple_call_arg (stmt, 2),
2718 gimple_call_arg (stmt, 3),
2722 case BUILT_IN_SNPRINTF_CHK:
2723 case BUILT_IN_VSNPRINTF_CHK:
2724 if (val[1] && is_gimple_val (val[1]))
2725 result = gimple_fold_builtin_snprintf_chk (stmt, val[1],
2726 DECL_FUNCTION_CODE (callee));
2733 if (result && ignore)
2734 result = fold_ignored_result (result);
2738 /* Attempt to fold an assignment statement pointed-to by SI. Returns a
2739 replacement rhs for the statement or NULL_TREE if no simplification
2740 could be made. It is assumed that the operands have been previously
2744 fold_gimple_assign (gimple_stmt_iterator *si)
2746 gimple stmt = gsi_stmt (*si);
2747 enum tree_code subcode = gimple_assign_rhs_code (stmt);
2748 location_t loc = gimple_location (stmt);
2750 tree result = NULL_TREE;
2752 switch (get_gimple_rhs_class (subcode))
2754 case GIMPLE_SINGLE_RHS:
2756 tree rhs = gimple_assign_rhs1 (stmt);
2758 /* Try to fold a conditional expression. */
2759 if (TREE_CODE (rhs) == COND_EXPR)
2761 tree op0 = COND_EXPR_COND (rhs);
2764 location_t cond_loc = EXPR_LOCATION (rhs);
2766 if (COMPARISON_CLASS_P (op0))
2768 fold_defer_overflow_warnings ();
2769 tem = fold_binary_loc (cond_loc,
2770 TREE_CODE (op0), TREE_TYPE (op0),
2771 TREE_OPERAND (op0, 0),
2772 TREE_OPERAND (op0, 1));
2773 /* This is actually a conditional expression, not a GIMPLE
2774 conditional statement, however, the valid_gimple_rhs_p
2775 test still applies. */
2776 set = (tem && is_gimple_condexpr (tem)
2777 && valid_gimple_rhs_p (tem));
2778 fold_undefer_overflow_warnings (set, stmt, 0);
2780 else if (is_gimple_min_invariant (op0))
2789 result = fold_build3_loc (cond_loc, COND_EXPR, TREE_TYPE (rhs), tem,
2790 COND_EXPR_THEN (rhs), COND_EXPR_ELSE (rhs));
2793 else if (TREE_CODE (rhs) == TARGET_MEM_REF)
2794 return maybe_fold_tmr (rhs);
2796 else if (REFERENCE_CLASS_P (rhs))
2797 return maybe_fold_reference (rhs, false);
2799 else if (TREE_CODE (rhs) == ADDR_EXPR)
2801 tree tem = maybe_fold_reference (TREE_OPERAND (rhs, 0), true);
2803 result = fold_convert (TREE_TYPE (rhs),
2804 build_fold_addr_expr_loc (loc, tem));
2807 else if (TREE_CODE (rhs) == CONSTRUCTOR
2808 && TREE_CODE (TREE_TYPE (rhs)) == VECTOR_TYPE
2809 && (CONSTRUCTOR_NELTS (rhs)
2810 == TYPE_VECTOR_SUBPARTS (TREE_TYPE (rhs))))
2812 /* Fold a constant vector CONSTRUCTOR to VECTOR_CST. */
2816 FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (rhs), i, val)
2817 if (TREE_CODE (val) != INTEGER_CST
2818 && TREE_CODE (val) != REAL_CST
2819 && TREE_CODE (val) != FIXED_CST)
2822 return build_vector_from_ctor (TREE_TYPE (rhs),
2823 CONSTRUCTOR_ELTS (rhs));
2826 else if (DECL_P (rhs))
2827 return get_symbol_constant_value (rhs);
2829 /* If we couldn't fold the RHS, hand over to the generic
2831 if (result == NULL_TREE)
2832 result = fold (rhs);
2834 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR
2835 that may have been added by fold, and "useless" type
2836 conversions that might now be apparent due to propagation. */
2837 STRIP_USELESS_TYPE_CONVERSION (result);
2839 if (result != rhs && valid_gimple_rhs_p (result))
2846 case GIMPLE_UNARY_RHS:
2848 tree rhs = gimple_assign_rhs1 (stmt);
2850 result = fold_unary_loc (loc, subcode, gimple_expr_type (stmt), rhs);
2853 /* If the operation was a conversion do _not_ mark a
2854 resulting constant with TREE_OVERFLOW if the original
2855 constant was not. These conversions have implementation
2856 defined behavior and retaining the TREE_OVERFLOW flag
2857 here would confuse later passes such as VRP. */
2858 if (CONVERT_EXPR_CODE_P (subcode)
2859 && TREE_CODE (result) == INTEGER_CST
2860 && TREE_CODE (rhs) == INTEGER_CST)
2861 TREE_OVERFLOW (result) = TREE_OVERFLOW (rhs);
2863 STRIP_USELESS_TYPE_CONVERSION (result);
2864 if (valid_gimple_rhs_p (result))
2867 else if (CONVERT_EXPR_CODE_P (subcode)
2868 && POINTER_TYPE_P (gimple_expr_type (stmt))
2869 && POINTER_TYPE_P (TREE_TYPE (gimple_assign_rhs1 (stmt))))
2871 tree type = gimple_expr_type (stmt);
2872 tree t = maybe_fold_offset_to_address (loc,
2873 gimple_assign_rhs1 (stmt),
2874 integer_zero_node, type);
2881 case GIMPLE_BINARY_RHS:
2882 /* Try to fold pointer addition. */
2883 if (gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR)
2885 tree type = TREE_TYPE (gimple_assign_rhs1 (stmt));
2886 if (TREE_CODE (TREE_TYPE (type)) == ARRAY_TYPE)
2888 type = build_pointer_type (TREE_TYPE (TREE_TYPE (type)));
2889 if (!useless_type_conversion_p
2890 (TREE_TYPE (gimple_assign_lhs (stmt)), type))
2891 type = TREE_TYPE (gimple_assign_rhs1 (stmt));
2893 result = maybe_fold_stmt_addition (gimple_location (stmt),
2895 gimple_assign_rhs1 (stmt),
2896 gimple_assign_rhs2 (stmt));
2900 result = fold_binary_loc (loc, subcode,
2901 TREE_TYPE (gimple_assign_lhs (stmt)),
2902 gimple_assign_rhs1 (stmt),
2903 gimple_assign_rhs2 (stmt));
2907 STRIP_USELESS_TYPE_CONVERSION (result);
2908 if (valid_gimple_rhs_p (result))
2911 /* Fold might have produced non-GIMPLE, so if we trust it blindly
2912 we lose canonicalization opportunities. Do not go again
2913 through fold here though, or the same non-GIMPLE will be
2915 if (commutative_tree_code (subcode)
2916 && tree_swap_operands_p (gimple_assign_rhs1 (stmt),
2917 gimple_assign_rhs2 (stmt), false))
2918 return build2 (subcode, TREE_TYPE (gimple_assign_lhs (stmt)),
2919 gimple_assign_rhs2 (stmt),
2920 gimple_assign_rhs1 (stmt));
2924 case GIMPLE_INVALID_RHS:
2931 /* Attempt to fold a conditional statement. Return true if any changes were
2932 made. We only attempt to fold the condition expression, and do not perform
2933 any transformation that would require alteration of the cfg. It is
2934 assumed that the operands have been previously folded. */
2937 fold_gimple_cond (gimple stmt)
2939 tree result = fold_binary_loc (gimple_location (stmt),
2940 gimple_cond_code (stmt),
2942 gimple_cond_lhs (stmt),
2943 gimple_cond_rhs (stmt));
2947 STRIP_USELESS_TYPE_CONVERSION (result);
2948 if (is_gimple_condexpr (result) && valid_gimple_rhs_p (result))
2950 gimple_cond_set_condition_from_tree (stmt, result);
2958 static void gimplify_and_update_call_from_tree (gimple_stmt_iterator *, tree);
2960 /* Attempt to fold a call statement referenced by the statement iterator GSI.
2961 The statement may be replaced by another statement, e.g., if the call
2962 simplifies to a constant value. Return true if any changes were made.
2963 It is assumed that the operands have been previously folded. */
2966 fold_gimple_call (gimple_stmt_iterator *gsi)
2968 gimple stmt = gsi_stmt (*gsi);
2970 tree callee = gimple_call_fndecl (stmt);
2972 /* Check for builtins that CCP can handle using information not
2973 available in the generic fold routines. */
2974 if (callee && DECL_BUILT_IN (callee))
2976 tree result = ccp_fold_builtin (stmt);
2980 if (!update_call_from_tree (gsi, result))
2981 gimplify_and_update_call_from_tree (gsi, result);
2987 /* Check for resolvable OBJ_TYPE_REF. The only sorts we can resolve
2988 here are when we've propagated the address of a decl into the
2990 /* ??? Should perhaps do this in fold proper. However, doing it
2991 there requires that we create a new CALL_EXPR, and that requires
2992 copying EH region info to the new node. Easier to just do it
2993 here where we can just smash the call operand. */
2994 /* ??? Is there a good reason not to do this in fold_stmt_inplace? */
2995 callee = gimple_call_fn (stmt);
2996 if (TREE_CODE (callee) == OBJ_TYPE_REF
2997 && lang_hooks.fold_obj_type_ref
2998 && TREE_CODE (OBJ_TYPE_REF_OBJECT (callee)) == ADDR_EXPR
2999 && DECL_P (TREE_OPERAND
3000 (OBJ_TYPE_REF_OBJECT (callee), 0)))
3004 /* ??? Caution: Broken ADDR_EXPR semantics means that
3005 looking at the type of the operand of the addr_expr
3006 can yield an array type. See silly exception in
3007 check_pointer_types_r. */
3008 t = TREE_TYPE (TREE_TYPE (OBJ_TYPE_REF_OBJECT (callee)));
3009 t = lang_hooks.fold_obj_type_ref (callee, t);
3012 gimple_call_set_fn (stmt, t);
3021 /* Worker for both fold_stmt and fold_stmt_inplace. The INPLACE argument
3022 distinguishes both cases. */
3025 fold_stmt_1 (gimple_stmt_iterator *gsi, bool inplace)
3027 bool changed = false;
3028 gimple stmt = gsi_stmt (*gsi);
3031 /* Fold the main computation performed by the statement. */
3032 switch (gimple_code (stmt))
3036 unsigned old_num_ops = gimple_num_ops (stmt);
3037 tree new_rhs = fold_gimple_assign (gsi);
3038 if (new_rhs != NULL_TREE
3040 || get_gimple_rhs_num_ops (TREE_CODE (new_rhs)) < old_num_ops))
3042 gimple_assign_set_rhs_from_tree (gsi, new_rhs);
3049 changed |= fold_gimple_cond (stmt);
3053 /* Fold *& in call arguments. */
3054 for (i = 0; i < gimple_call_num_args (stmt); ++i)
3055 if (REFERENCE_CLASS_P (gimple_call_arg (stmt, i)))
3057 tree tmp = maybe_fold_reference (gimple_call_arg (stmt, i), false);
3060 gimple_call_set_arg (stmt, i, tmp);
3064 /* The entire statement may be replaced in this case. */
3066 changed |= fold_gimple_call (gsi);
3070 /* Fold *& in asm operands. */
3071 for (i = 0; i < gimple_asm_noutputs (stmt); ++i)
3073 tree link = gimple_asm_output_op (stmt, i);
3074 tree op = TREE_VALUE (link);
3075 if (REFERENCE_CLASS_P (op)
3076 && (op = maybe_fold_reference (op, true)) != NULL_TREE)
3078 TREE_VALUE (link) = op;
3082 for (i = 0; i < gimple_asm_ninputs (stmt); ++i)
3084 tree link = gimple_asm_input_op (stmt, i);
3085 tree op = TREE_VALUE (link);
3086 if (REFERENCE_CLASS_P (op)
3087 && (op = maybe_fold_reference (op, false)) != NULL_TREE)
3089 TREE_VALUE (link) = op;
3098 stmt = gsi_stmt (*gsi);
3100 /* Fold *& on the lhs. */
3101 if (gimple_has_lhs (stmt))
3103 tree lhs = gimple_get_lhs (stmt);
3104 if (lhs && REFERENCE_CLASS_P (lhs))
3106 tree new_lhs = maybe_fold_reference (lhs, true);
3109 gimple_set_lhs (stmt, new_lhs);
3118 /* Fold the statement pointed to by GSI. In some cases, this function may
3119 replace the whole statement with a new one. Returns true iff folding
3121 The statement pointed to by GSI should be in valid gimple form but may
3122 be in unfolded state as resulting from for example constant propagation
3123 which can produce *&x = 0. */
3126 fold_stmt (gimple_stmt_iterator *gsi)
3128 return fold_stmt_1 (gsi, false);
3131 /* Perform the minimal folding on statement STMT. Only operations like
3132 *&x created by constant propagation are handled. The statement cannot
3133 be replaced with a new one. Return true if the statement was
3134 changed, false otherwise.
3135 The statement STMT should be in valid gimple form but may
3136 be in unfolded state as resulting from for example constant propagation
3137 which can produce *&x = 0. */
3140 fold_stmt_inplace (gimple stmt)
3142 gimple_stmt_iterator gsi = gsi_for_stmt (stmt);
3143 bool changed = fold_stmt_1 (&gsi, true);
3144 gcc_assert (gsi_stmt (gsi) == stmt);
3148 /* Try to optimize out __builtin_stack_restore. Optimize it out
3149 if there is another __builtin_stack_restore in the same basic
3150 block and no calls or ASM_EXPRs are in between, or if this block's
3151 only outgoing edge is to EXIT_BLOCK and there are no calls or
3152 ASM_EXPRs after this __builtin_stack_restore. */
3155 optimize_stack_restore (gimple_stmt_iterator i)
3160 basic_block bb = gsi_bb (i);
3161 gimple call = gsi_stmt (i);
3163 if (gimple_code (call) != GIMPLE_CALL
3164 || gimple_call_num_args (call) != 1
3165 || TREE_CODE (gimple_call_arg (call, 0)) != SSA_NAME
3166 || !POINTER_TYPE_P (TREE_TYPE (gimple_call_arg (call, 0))))
3169 for (gsi_next (&i); !gsi_end_p (i); gsi_next (&i))
3171 stmt = gsi_stmt (i);
3172 if (gimple_code (stmt) == GIMPLE_ASM)
3174 if (gimple_code (stmt) != GIMPLE_CALL)
3177 callee = gimple_call_fndecl (stmt);
3178 if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)
3181 if (DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_RESTORE)
3182 goto second_stack_restore;
3188 /* Allow one successor of the exit block, or zero successors. */
3189 switch (EDGE_COUNT (bb->succs))
3194 if (single_succ_edge (bb)->dest != EXIT_BLOCK_PTR)
3200 second_stack_restore:
3202 /* If there's exactly one use, then zap the call to __builtin_stack_save.
3203 If there are multiple uses, then the last one should remove the call.
3204 In any case, whether the call to __builtin_stack_save can be removed
3205 or not is irrelevant to removing the call to __builtin_stack_restore. */
3206 if (has_single_use (gimple_call_arg (call, 0)))
3208 gimple stack_save = SSA_NAME_DEF_STMT (gimple_call_arg (call, 0));
3209 if (is_gimple_call (stack_save))
3211 callee = gimple_call_fndecl (stack_save);
3213 && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL
3214 && DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_SAVE)
3216 gimple_stmt_iterator stack_save_gsi;
3219 stack_save_gsi = gsi_for_stmt (stack_save);
3220 rhs = build_int_cst (TREE_TYPE (gimple_call_arg (call, 0)), 0);
3221 update_call_from_tree (&stack_save_gsi, rhs);
3226 /* No effect, so the statement will be deleted. */
3227 return integer_zero_node;
3230 /* If va_list type is a simple pointer and nothing special is needed,
3231 optimize __builtin_va_start (&ap, 0) into ap = __builtin_next_arg (0),
3232 __builtin_va_end (&ap) out as NOP and __builtin_va_copy into a simple
3233 pointer assignment. */
3236 optimize_stdarg_builtin (gimple call)
3238 tree callee, lhs, rhs, cfun_va_list;
3239 bool va_list_simple_ptr;
3240 location_t loc = gimple_location (call);
3242 if (gimple_code (call) != GIMPLE_CALL)
3245 callee = gimple_call_fndecl (call);
3247 cfun_va_list = targetm.fn_abi_va_list (callee);
3248 va_list_simple_ptr = POINTER_TYPE_P (cfun_va_list)
3249 && (TREE_TYPE (cfun_va_list) == void_type_node
3250 || TREE_TYPE (cfun_va_list) == char_type_node);
3252 switch (DECL_FUNCTION_CODE (callee))
3254 case BUILT_IN_VA_START:
3255 if (!va_list_simple_ptr
3256 || targetm.expand_builtin_va_start != NULL
3257 || built_in_decls[BUILT_IN_NEXT_ARG] == NULL)
3260 if (gimple_call_num_args (call) != 2)
3263 lhs = gimple_call_arg (call, 0);
3264 if (!POINTER_TYPE_P (TREE_TYPE (lhs))
3265 || TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs)))
3266 != TYPE_MAIN_VARIANT (cfun_va_list))
3269 lhs = build_fold_indirect_ref_loc (loc, lhs);
3270 rhs = build_call_expr_loc (loc, built_in_decls[BUILT_IN_NEXT_ARG],
3271 1, integer_zero_node);
3272 rhs = fold_convert_loc (loc, TREE_TYPE (lhs), rhs);
3273 return build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, rhs);
3275 case BUILT_IN_VA_COPY:
3276 if (!va_list_simple_ptr)
3279 if (gimple_call_num_args (call) != 2)
3282 lhs = gimple_call_arg (call, 0);
3283 if (!POINTER_TYPE_P (TREE_TYPE (lhs))
3284 || TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs)))
3285 != TYPE_MAIN_VARIANT (cfun_va_list))
3288 lhs = build_fold_indirect_ref_loc (loc, lhs);
3289 rhs = gimple_call_arg (call, 1);
3290 if (TYPE_MAIN_VARIANT (TREE_TYPE (rhs))
3291 != TYPE_MAIN_VARIANT (cfun_va_list))
3294 rhs = fold_convert_loc (loc, TREE_TYPE (lhs), rhs);
3295 return build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, rhs);
3297 case BUILT_IN_VA_END:
3298 /* No effect, so the statement will be deleted. */
3299 return integer_zero_node;
3306 /* Convert EXPR into a GIMPLE value suitable for substitution on the
3307 RHS of an assignment. Insert the necessary statements before
3308 iterator *SI_P. The statement at *SI_P, which must be a GIMPLE_CALL
3309 is replaced. If the call is expected to produces a result, then it
3310 is replaced by an assignment of the new RHS to the result variable.
3311 If the result is to be ignored, then the call is replaced by a
3315 gimplify_and_update_call_from_tree (gimple_stmt_iterator *si_p, tree expr)
3318 tree tmp = NULL_TREE; /* Silence warning. */
3319 gimple stmt, new_stmt;
3320 gimple_stmt_iterator i;
3321 gimple_seq stmts = gimple_seq_alloc();
3322 struct gimplify_ctx gctx;
3324 stmt = gsi_stmt (*si_p);
3326 gcc_assert (is_gimple_call (stmt));
3328 lhs = gimple_call_lhs (stmt);
3330 push_gimplify_context (&gctx);
3332 if (lhs == NULL_TREE)
3333 gimplify_and_add (expr, &stmts);
3335 tmp = get_initialized_tmp_var (expr, &stmts, NULL);
3337 pop_gimplify_context (NULL);
3339 if (gimple_has_location (stmt))
3340 annotate_all_with_location (stmts, gimple_location (stmt));
3342 /* The replacement can expose previously unreferenced variables. */
3343 for (i = gsi_start (stmts); !gsi_end_p (i); gsi_next (&i))
3345 new_stmt = gsi_stmt (i);
3346 find_new_referenced_vars (new_stmt);
3347 gsi_insert_before (si_p, new_stmt, GSI_NEW_STMT);
3348 mark_symbols_for_renaming (new_stmt);
3352 if (lhs == NULL_TREE)
3354 new_stmt = gimple_build_nop ();
3355 unlink_stmt_vdef (stmt);
3356 release_defs (stmt);
3360 new_stmt = gimple_build_assign (lhs, tmp);
3361 gimple_set_vuse (new_stmt, gimple_vuse (stmt));
3362 gimple_set_vdef (new_stmt, gimple_vdef (stmt));
3363 move_ssa_defining_stmt_for_defs (new_stmt, stmt);
3366 gimple_set_location (new_stmt, gimple_location (stmt));
3367 gsi_replace (si_p, new_stmt, false);
3370 /* A simple pass that attempts to fold all builtin functions. This pass
3371 is run after we've propagated as many constants as we can. */
3374 execute_fold_all_builtins (void)
3376 bool cfg_changed = false;
3378 unsigned int todoflags = 0;
3382 gimple_stmt_iterator i;
3383 for (i = gsi_start_bb (bb); !gsi_end_p (i); )
3385 gimple stmt, old_stmt;
3386 tree callee, result;
3387 enum built_in_function fcode;
3389 stmt = gsi_stmt (i);
3391 if (gimple_code (stmt) != GIMPLE_CALL)
3396 callee = gimple_call_fndecl (stmt);
3397 if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)
3402 fcode = DECL_FUNCTION_CODE (callee);
3404 result = ccp_fold_builtin (stmt);
3407 gimple_remove_stmt_histograms (cfun, stmt);
3410 switch (DECL_FUNCTION_CODE (callee))
3412 case BUILT_IN_CONSTANT_P:
3413 /* Resolve __builtin_constant_p. If it hasn't been
3414 folded to integer_one_node by now, it's fairly
3415 certain that the value simply isn't constant. */
3416 result = integer_zero_node;
3419 case BUILT_IN_STACK_RESTORE:
3420 result = optimize_stack_restore (i);
3426 case BUILT_IN_VA_START:
3427 case BUILT_IN_VA_END:
3428 case BUILT_IN_VA_COPY:
3429 /* These shouldn't be folded before pass_stdarg. */
3430 result = optimize_stdarg_builtin (stmt);
3440 if (dump_file && (dump_flags & TDF_DETAILS))
3442 fprintf (dump_file, "Simplified\n ");
3443 print_gimple_stmt (dump_file, stmt, 0, dump_flags);
3447 if (!update_call_from_tree (&i, result))
3449 gimplify_and_update_call_from_tree (&i, result);
3450 todoflags |= TODO_update_address_taken;
3453 stmt = gsi_stmt (i);
3456 if (maybe_clean_or_replace_eh_stmt (old_stmt, stmt)
3457 && gimple_purge_dead_eh_edges (bb))
3460 if (dump_file && (dump_flags & TDF_DETAILS))
3462 fprintf (dump_file, "to\n ");
3463 print_gimple_stmt (dump_file, stmt, 0, dump_flags);
3464 fprintf (dump_file, "\n");
3467 /* Retry the same statement if it changed into another
3468 builtin, there might be new opportunities now. */
3469 if (gimple_code (stmt) != GIMPLE_CALL)
3474 callee = gimple_call_fndecl (stmt);
3476 || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL
3477 || DECL_FUNCTION_CODE (callee) == fcode)
3482 /* Delete unreachable blocks. */
3484 todoflags |= TODO_cleanup_cfg;
3490 struct gimple_opt_pass pass_fold_builtins =
3496 execute_fold_all_builtins, /* execute */
3499 0, /* static_pass_number */
3500 TV_NONE, /* tv_id */
3501 PROP_cfg | PROP_ssa, /* properties_required */
3502 0, /* properties_provided */
3503 0, /* properties_destroyed */
3504 0, /* todo_flags_start */
3507 | TODO_update_ssa /* todo_flags_finish */