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
)
305 tree val
= DECL_INITIAL (sym
);
307 && ccp_decl_initial_min_invariant (val
))
309 /* Variables declared 'const' without an initializer
310 have zero as the intializer if they may not be
311 overridden at link or run time. */
313 && targetm
.binds_local_p (sym
)
314 && (INTEGRAL_TYPE_P (TREE_TYPE (sym
))
315 || SCALAR_FLOAT_TYPE_P (TREE_TYPE (sym
))))
316 return fold_convert (TREE_TYPE (sym
), integer_zero_node
);
322 /* Compute a default value for variable VAR and store it in the
323 CONST_VAL array. The following rules are used to get default
326 1- Global and static variables that are declared constant are
329 2- Any other value is considered UNDEFINED. This is useful when
330 considering PHI nodes. PHI arguments that are undefined do not
331 change the constant value of the PHI node, which allows for more
332 constants to be propagated.
334 3- If SSA_NAME_VALUE is set and it is a constant, its value is
337 4- Variables defined by statements other than assignments and PHI
338 nodes are considered VARYING.
340 5- Initial values of variables that are not GIMPLE registers are
341 considered VARYING. */
344 get_default_value (tree var
)
346 tree sym
= SSA_NAME_VAR (var
);
347 prop_value_t val
= { UNINITIALIZED
, NULL_TREE
, NULL_TREE
};
350 if (!do_store_ccp
&& !is_gimple_reg (var
))
352 /* Short circuit for regular CCP. We are not interested in any
353 non-register when DO_STORE_CCP is false. */
354 val
.lattice_val
= VARYING
;
356 else if (SSA_NAME_VALUE (var
)
357 && is_gimple_min_invariant (SSA_NAME_VALUE (var
)))
359 val
.lattice_val
= CONSTANT
;
360 val
.value
= SSA_NAME_VALUE (var
);
362 else if ((cst_val
= get_symbol_constant_value (sym
)) != NULL_TREE
)
364 /* Globals and static variables declared 'const' take their
366 val
.lattice_val
= CONSTANT
;
372 tree stmt
= SSA_NAME_DEF_STMT (var
);
374 if (IS_EMPTY_STMT (stmt
))
376 /* Variables defined by an empty statement are those used
377 before being initialized. If VAR is a local variable, we
378 can assume initially that it is UNDEFINED, otherwise we must
379 consider it VARYING. */
380 if (is_gimple_reg (sym
) && TREE_CODE (sym
) != PARM_DECL
)
381 val
.lattice_val
= UNDEFINED
;
383 val
.lattice_val
= VARYING
;
385 else if (TREE_CODE (stmt
) == GIMPLE_MODIFY_STMT
386 || TREE_CODE (stmt
) == PHI_NODE
)
388 /* Any other variable defined by an assignment or a PHI node
389 is considered UNDEFINED. */
390 val
.lattice_val
= UNDEFINED
;
394 /* Otherwise, VAR will never take on a constant value. */
395 val
.lattice_val
= VARYING
;
403 /* Get the constant value associated with variable VAR. */
405 static inline prop_value_t
*
410 if (const_val
== NULL
)
413 val
= &const_val
[SSA_NAME_VERSION (var
)];
414 if (val
->lattice_val
== UNINITIALIZED
)
415 *val
= get_default_value (var
);
420 /* Sets the value associated with VAR to VARYING. */
423 set_value_varying (tree var
)
425 prop_value_t
*val
= &const_val
[SSA_NAME_VERSION (var
)];
427 val
->lattice_val
= VARYING
;
428 val
->value
= NULL_TREE
;
429 val
->mem_ref
= NULL_TREE
;
432 /* For float types, modify the value of VAL to make ccp work correctly
433 for non-standard values (-0, NaN):
435 If HONOR_SIGNED_ZEROS is false, and VAL = -0, we canonicalize it to 0.
436 If HONOR_NANS is false, and VAL is NaN, we canonicalize it to UNDEFINED.
437 This is to fix the following problem (see PR 29921): Suppose we have
441 and we set value of y to NaN. This causes value of x to be set to NaN.
442 When we later determine that y is in fact VARYING, fold uses the fact
443 that HONOR_NANS is false, and we try to change the value of x to 0,
444 causing an ICE. With HONOR_NANS being false, the real appearance of
445 NaN would cause undefined behavior, though, so claiming that y (and x)
446 are UNDEFINED initially is correct. */
449 canonicalize_float_value (prop_value_t
*val
)
451 enum machine_mode mode
;
455 if (val
->lattice_val
!= CONSTANT
456 || TREE_CODE (val
->value
) != REAL_CST
)
459 d
= TREE_REAL_CST (val
->value
);
460 type
= TREE_TYPE (val
->value
);
461 mode
= TYPE_MODE (type
);
463 if (!HONOR_SIGNED_ZEROS (mode
)
464 && REAL_VALUE_MINUS_ZERO (d
))
466 val
->value
= build_real (type
, dconst0
);
470 if (!HONOR_NANS (mode
)
471 && REAL_VALUE_ISNAN (d
))
473 val
->lattice_val
= UNDEFINED
;
480 /* Set the value for variable VAR to NEW_VAL. Return true if the new
481 value is different from VAR's previous value. */
484 set_lattice_value (tree var
, prop_value_t new_val
)
486 prop_value_t
*old_val
= get_value (var
);
488 canonicalize_float_value (&new_val
);
490 /* Lattice transitions must always be monotonically increasing in
491 value. If *OLD_VAL and NEW_VAL are the same, return false to
492 inform the caller that this was a non-transition. */
494 gcc_assert (old_val
->lattice_val
< new_val
.lattice_val
495 || (old_val
->lattice_val
== new_val
.lattice_val
496 && ((!old_val
->value
&& !new_val
.value
)
497 || operand_equal_p (old_val
->value
, new_val
.value
, 0))
498 && old_val
->mem_ref
== new_val
.mem_ref
));
500 if (old_val
->lattice_val
!= new_val
.lattice_val
)
502 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
504 dump_lattice_value (dump_file
, "Lattice value changed to ", new_val
);
505 fprintf (dump_file
, ". Adding SSA edges to worklist.\n");
510 gcc_assert (new_val
.lattice_val
!= UNDEFINED
);
518 /* Return the likely CCP lattice value for STMT.
520 If STMT has no operands, then return CONSTANT.
522 Else if undefinedness of operands of STMT cause its value to be
523 undefined, then return UNDEFINED.
525 Else if any operands of STMT are constants, then return CONSTANT.
527 Else return VARYING. */
530 likely_value (tree stmt
)
532 bool has_constant_operand
, has_undefined_operand
, all_undefined_operands
;
537 ann
= stmt_ann (stmt
);
539 /* If the statement has volatile operands, it won't fold to a
541 if (ann
->has_volatile_ops
)
544 /* If we are not doing store-ccp, statements with loads
545 and/or stores will never fold into a constant. */
547 && !ZERO_SSA_OPERANDS (stmt
, SSA_OP_ALL_VIRTUALS
))
551 /* A CALL_EXPR is assumed to be varying. NOTE: This may be overly
552 conservative, in the presence of const and pure calls. */
553 if (get_call_expr_in (stmt
) != NULL_TREE
)
556 /* Anything other than assignments and conditional jumps are not
557 interesting for CCP. */
558 if (TREE_CODE (stmt
) != GIMPLE_MODIFY_STMT
559 && !(TREE_CODE (stmt
) == RETURN_EXPR
&& get_rhs (stmt
) != NULL_TREE
)
560 && TREE_CODE (stmt
) != COND_EXPR
561 && TREE_CODE (stmt
) != SWITCH_EXPR
)
564 if (is_gimple_min_invariant (get_rhs (stmt
)))
567 has_constant_operand
= false;
568 has_undefined_operand
= false;
569 all_undefined_operands
= true;
570 FOR_EACH_SSA_TREE_OPERAND (use
, stmt
, iter
, SSA_OP_USE
| SSA_OP_VUSE
)
572 prop_value_t
*val
= get_value (use
);
574 if (val
->lattice_val
== UNDEFINED
)
575 has_undefined_operand
= true;
577 all_undefined_operands
= false;
579 if (val
->lattice_val
== CONSTANT
)
580 has_constant_operand
= true;
583 /* If the operation combines operands like COMPLEX_EXPR make sure to
584 not mark the result UNDEFINED if only one part of the result is
586 if (has_undefined_operand
587 && all_undefined_operands
)
589 else if (TREE_CODE (stmt
) == GIMPLE_MODIFY_STMT
590 && has_undefined_operand
)
592 switch (TREE_CODE (GIMPLE_STMT_OPERAND (stmt
, 1)))
594 /* Unary operators are handled with all_undefined_operands. */
597 case POINTER_PLUS_EXPR
:
598 /* Not MIN_EXPR, MAX_EXPR. One VARYING operand may be selected.
599 Not bitwise operators, one VARYING operand may specify the
600 result completely. Not logical operators for the same reason.
601 Not COMPLEX_EXPR as one VARYING operand makes the result partly
602 not UNDEFINED. Not *DIV_EXPR, comparisons and shifts because
603 the undefined operand may be promoted. */
610 /* If there was an UNDEFINED operand but the result may be not UNDEFINED
611 fall back to VARYING even if there were CONSTANT operands. */
612 if (has_undefined_operand
)
615 if (has_constant_operand
616 /* We do not consider virtual operands here -- load from read-only
617 memory may have only VARYING virtual operands, but still be
619 || ZERO_SSA_OPERANDS (stmt
, SSA_OP_USE
))
625 /* Returns true if STMT cannot be constant. */
628 surely_varying_stmt_p (tree stmt
)
630 /* If the statement has operands that we cannot handle, it cannot be
632 if (stmt_ann (stmt
)->has_volatile_ops
)
635 if (!ZERO_SSA_OPERANDS (stmt
, SSA_OP_ALL_VIRTUALS
))
640 /* We can only handle simple loads and stores. */
641 if (!stmt_makes_single_load (stmt
)
642 && !stmt_makes_single_store (stmt
))
646 /* If it contains a call, it is varying. */
647 if (get_call_expr_in (stmt
) != NULL_TREE
)
650 /* Anything other than assignments and conditional jumps are not
651 interesting for CCP. */
652 if (TREE_CODE (stmt
) != GIMPLE_MODIFY_STMT
653 && !(TREE_CODE (stmt
) == RETURN_EXPR
&& get_rhs (stmt
) != NULL_TREE
)
654 && TREE_CODE (stmt
) != COND_EXPR
655 && TREE_CODE (stmt
) != SWITCH_EXPR
)
661 /* Initialize local data structures for CCP. */
664 ccp_initialize (void)
668 const_val
= XCNEWVEC (prop_value_t
, num_ssa_names
);
670 /* Initialize simulation flags for PHI nodes and statements. */
673 block_stmt_iterator i
;
675 for (i
= bsi_start (bb
); !bsi_end_p (i
); bsi_next (&i
))
677 tree stmt
= bsi_stmt (i
);
678 bool is_varying
= surely_varying_stmt_p (stmt
);
685 /* If the statement will not produce a constant, mark
686 all its outputs VARYING. */
687 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_ALL_DEFS
)
690 set_value_varying (def
);
694 DONT_SIMULATE_AGAIN (stmt
) = is_varying
;
698 /* Now process PHI nodes. We never set DONT_SIMULATE_AGAIN on phi node,
699 since we do not know which edges are executable yet, except for
700 phi nodes for virtual operands when we do not do store ccp. */
705 for (phi
= phi_nodes (bb
); phi
; phi
= PHI_CHAIN (phi
))
707 if (!do_store_ccp
&& !is_gimple_reg (PHI_RESULT (phi
)))
708 DONT_SIMULATE_AGAIN (phi
) = true;
710 DONT_SIMULATE_AGAIN (phi
) = false;
716 /* Do final substitution of propagated values, cleanup the flowgraph and
717 free allocated storage.
719 Return TRUE when something was optimized. */
724 /* Perform substitutions based on the known constant values. */
725 bool something_changed
= substitute_and_fold (const_val
, false);
729 return something_changed
;;
733 /* Compute the meet operator between *VAL1 and *VAL2. Store the result
736 any M UNDEFINED = any
737 any M VARYING = VARYING
738 Ci M Cj = Ci if (i == j)
739 Ci M Cj = VARYING if (i != j)
743 ccp_lattice_meet (prop_value_t
*val1
, prop_value_t
*val2
)
745 if (val1
->lattice_val
== UNDEFINED
)
747 /* UNDEFINED M any = any */
750 else if (val2
->lattice_val
== UNDEFINED
)
752 /* any M UNDEFINED = any
753 Nothing to do. VAL1 already contains the value we want. */
756 else if (val1
->lattice_val
== VARYING
757 || val2
->lattice_val
== VARYING
)
759 /* any M VARYING = VARYING. */
760 val1
->lattice_val
= VARYING
;
761 val1
->value
= NULL_TREE
;
762 val1
->mem_ref
= NULL_TREE
;
764 else if (val1
->lattice_val
== CONSTANT
765 && val2
->lattice_val
== CONSTANT
766 && simple_cst_equal (val1
->value
, val2
->value
) == 1
768 || (val1
->mem_ref
&& val2
->mem_ref
769 && operand_equal_p (val1
->mem_ref
, val2
->mem_ref
, 0))))
771 /* Ci M Cj = Ci if (i == j)
772 Ci M Cj = VARYING if (i != j)
774 If these two values come from memory stores, make sure that
775 they come from the same memory reference. */
776 val1
->lattice_val
= CONSTANT
;
777 val1
->value
= val1
->value
;
778 val1
->mem_ref
= val1
->mem_ref
;
782 /* Any other combination is VARYING. */
783 val1
->lattice_val
= VARYING
;
784 val1
->value
= NULL_TREE
;
785 val1
->mem_ref
= NULL_TREE
;
790 /* Loop through the PHI_NODE's parameters for BLOCK and compare their
791 lattice values to determine PHI_NODE's lattice value. The value of a
792 PHI node is determined calling ccp_lattice_meet with all the arguments
793 of the PHI node that are incoming via executable edges. */
795 static enum ssa_prop_result
796 ccp_visit_phi_node (tree phi
)
799 prop_value_t
*old_val
, new_val
;
801 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
803 fprintf (dump_file
, "\nVisiting PHI node: ");
804 print_generic_expr (dump_file
, phi
, dump_flags
);
807 old_val
= get_value (PHI_RESULT (phi
));
808 switch (old_val
->lattice_val
)
811 return SSA_PROP_VARYING
;
818 new_val
.lattice_val
= UNDEFINED
;
819 new_val
.value
= NULL_TREE
;
820 new_val
.mem_ref
= NULL_TREE
;
827 for (i
= 0; i
< PHI_NUM_ARGS (phi
); i
++)
829 /* Compute the meet operator over all the PHI arguments flowing
830 through executable edges. */
831 edge e
= PHI_ARG_EDGE (phi
, i
);
833 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
836 "\n Argument #%d (%d -> %d %sexecutable)\n",
837 i
, e
->src
->index
, e
->dest
->index
,
838 (e
->flags
& EDGE_EXECUTABLE
) ? "" : "not ");
841 /* If the incoming edge is executable, Compute the meet operator for
842 the existing value of the PHI node and the current PHI argument. */
843 if (e
->flags
& EDGE_EXECUTABLE
)
845 tree arg
= PHI_ARG_DEF (phi
, i
);
846 prop_value_t arg_val
;
848 if (is_gimple_min_invariant (arg
))
850 arg_val
.lattice_val
= CONSTANT
;
852 arg_val
.mem_ref
= NULL_TREE
;
855 arg_val
= *(get_value (arg
));
857 ccp_lattice_meet (&new_val
, &arg_val
);
859 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
861 fprintf (dump_file
, "\t");
862 print_generic_expr (dump_file
, arg
, dump_flags
);
863 dump_lattice_value (dump_file
, "\tValue: ", arg_val
);
864 fprintf (dump_file
, "\n");
867 if (new_val
.lattice_val
== VARYING
)
872 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
874 dump_lattice_value (dump_file
, "\n PHI node value: ", new_val
);
875 fprintf (dump_file
, "\n\n");
878 /* Make the transition to the new value. */
879 if (set_lattice_value (PHI_RESULT (phi
), new_val
))
881 if (new_val
.lattice_val
== VARYING
)
882 return SSA_PROP_VARYING
;
884 return SSA_PROP_INTERESTING
;
887 return SSA_PROP_NOT_INTERESTING
;
891 /* CCP specific front-end to the non-destructive constant folding
894 Attempt to simplify the RHS of STMT knowing that one or more
895 operands are constants.
897 If simplification is possible, return the simplified RHS,
898 otherwise return the original RHS. */
903 tree rhs
= get_rhs (stmt
);
904 enum tree_code code
= TREE_CODE (rhs
);
905 enum tree_code_class kind
= TREE_CODE_CLASS (code
);
906 tree retval
= NULL_TREE
;
908 if (TREE_CODE (rhs
) == SSA_NAME
)
910 /* If the RHS is an SSA_NAME, return its known constant value,
912 return get_value (rhs
)->value
;
914 else if (do_store_ccp
&& stmt_makes_single_load (stmt
))
916 /* If the RHS is a memory load, see if the VUSEs associated with
917 it are a valid constant for that memory load. */
918 prop_value_t
*val
= get_value_loaded_by (stmt
, const_val
);
919 if (val
&& val
->mem_ref
)
921 if (operand_equal_p (val
->mem_ref
, rhs
, 0))
924 /* If RHS is extracting REALPART_EXPR or IMAGPART_EXPR of a
925 complex type with a known constant value, return it. */
926 if ((TREE_CODE (rhs
) == REALPART_EXPR
927 || TREE_CODE (rhs
) == IMAGPART_EXPR
)
928 && operand_equal_p (val
->mem_ref
, TREE_OPERAND (rhs
, 0), 0))
929 return fold_build1 (TREE_CODE (rhs
), TREE_TYPE (rhs
), val
->value
);
934 /* Unary operators. Note that we know the single operand must
935 be a constant. So this should almost always return a
937 if (kind
== tcc_unary
)
939 /* Handle unary operators which can appear in GIMPLE form. */
940 tree op0
= TREE_OPERAND (rhs
, 0);
942 /* Simplify the operand down to a constant. */
943 if (TREE_CODE (op0
) == SSA_NAME
)
945 prop_value_t
*val
= get_value (op0
);
946 if (val
->lattice_val
== CONSTANT
)
947 op0
= get_value (op0
)->value
;
950 /* Conversions are useless for CCP purposes if they are
951 value-preserving. Thus the restrictions that
952 useless_type_conversion_p places for pointer type conversions do
953 not apply here. Substitution later will only substitute to
955 if ((code
== NOP_EXPR
|| code
== CONVERT_EXPR
)
956 && ((POINTER_TYPE_P (TREE_TYPE (rhs
))
957 && POINTER_TYPE_P (TREE_TYPE (op0
)))
958 || useless_type_conversion_p (TREE_TYPE (rhs
), TREE_TYPE (op0
))))
960 return fold_unary (code
, TREE_TYPE (rhs
), op0
);
963 /* Binary and comparison operators. We know one or both of the
964 operands are constants. */
965 else if (kind
== tcc_binary
966 || kind
== tcc_comparison
967 || code
== TRUTH_AND_EXPR
968 || code
== TRUTH_OR_EXPR
969 || code
== TRUTH_XOR_EXPR
)
971 /* Handle binary and comparison operators that can appear in
973 tree op0
= TREE_OPERAND (rhs
, 0);
974 tree op1
= TREE_OPERAND (rhs
, 1);
976 /* Simplify the operands down to constants when appropriate. */
977 if (TREE_CODE (op0
) == SSA_NAME
)
979 prop_value_t
*val
= get_value (op0
);
980 if (val
->lattice_val
== CONSTANT
)
984 if (TREE_CODE (op1
) == SSA_NAME
)
986 prop_value_t
*val
= get_value (op1
);
987 if (val
->lattice_val
== CONSTANT
)
991 return fold_binary (code
, TREE_TYPE (rhs
), op0
, op1
);
994 else if (kind
== tcc_declaration
)
995 return get_symbol_constant_value (rhs
);
997 else if (kind
== tcc_reference
)
998 return fold_const_aggregate_ref (rhs
);
1000 /* We may be able to fold away calls to builtin functions if their
1001 arguments are constants. */
1002 else if (code
== CALL_EXPR
1003 && TREE_CODE (CALL_EXPR_FN (rhs
)) == ADDR_EXPR
1004 && TREE_CODE (TREE_OPERAND (CALL_EXPR_FN (rhs
), 0)) == FUNCTION_DECL
1005 && DECL_BUILT_IN (TREE_OPERAND (CALL_EXPR_FN (rhs
), 0)))
1007 if (!ZERO_SSA_OPERANDS (stmt
, SSA_OP_USE
))
1012 use_operand_p var_p
;
1014 /* Preserve the original values of every operand. */
1015 orig
= XNEWVEC (tree
, NUM_SSA_OPERANDS (stmt
, SSA_OP_USE
));
1016 FOR_EACH_SSA_TREE_OPERAND (var
, stmt
, iter
, SSA_OP_USE
)
1019 /* Substitute operands with their values and try to fold. */
1020 replace_uses_in (stmt
, NULL
, const_val
);
1021 retval
= fold_call_expr (rhs
, false);
1023 /* Restore operands to their original form. */
1025 FOR_EACH_SSA_USE_OPERAND (var_p
, stmt
, iter
, SSA_OP_USE
)
1026 SET_USE (var_p
, orig
[i
++]);
1033 /* If we got a simplified form, see if we need to convert its type. */
1035 return fold_convert (TREE_TYPE (rhs
), retval
);
1037 /* No simplification was possible. */
1042 /* Return the tree representing the element referenced by T if T is an
1043 ARRAY_REF or COMPONENT_REF into constant aggregates. Return
1044 NULL_TREE otherwise. */
1047 fold_const_aggregate_ref (tree t
)
1049 prop_value_t
*value
;
1050 tree base
, ctor
, idx
, field
;
1051 unsigned HOST_WIDE_INT cnt
;
1054 switch (TREE_CODE (t
))
1057 /* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its
1058 DECL_INITIAL. If BASE is a nested reference into another
1059 ARRAY_REF or COMPONENT_REF, make a recursive call to resolve
1060 the inner reference. */
1061 base
= TREE_OPERAND (t
, 0);
1062 switch (TREE_CODE (base
))
1065 if (!TREE_READONLY (base
)
1066 || TREE_CODE (TREE_TYPE (base
)) != ARRAY_TYPE
1067 || !targetm
.binds_local_p (base
))
1070 ctor
= DECL_INITIAL (base
);
1075 ctor
= fold_const_aggregate_ref (base
);
1087 if (ctor
== NULL_TREE
1088 || (TREE_CODE (ctor
) != CONSTRUCTOR
1089 && TREE_CODE (ctor
) != STRING_CST
)
1090 || !TREE_STATIC (ctor
))
1093 /* Get the index. If we have an SSA_NAME, try to resolve it
1094 with the current lattice value for the SSA_NAME. */
1095 idx
= TREE_OPERAND (t
, 1);
1096 switch (TREE_CODE (idx
))
1099 if ((value
= get_value (idx
))
1100 && value
->lattice_val
== CONSTANT
1101 && TREE_CODE (value
->value
) == INTEGER_CST
)
1114 /* Fold read from constant string. */
1115 if (TREE_CODE (ctor
) == STRING_CST
)
1117 if ((TYPE_MODE (TREE_TYPE (t
))
1118 == TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor
))))
1119 && (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor
))))
1121 && GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor
)))) == 1
1122 && compare_tree_int (idx
, TREE_STRING_LENGTH (ctor
)) < 0)
1123 return build_int_cst_type (TREE_TYPE (t
),
1124 (TREE_STRING_POINTER (ctor
)
1125 [TREE_INT_CST_LOW (idx
)]));
1129 /* Whoo-hoo! I'll fold ya baby. Yeah! */
1130 FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor
), cnt
, cfield
, cval
)
1131 if (tree_int_cst_equal (cfield
, idx
))
1136 /* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its
1137 DECL_INITIAL. If BASE is a nested reference into another
1138 ARRAY_REF or COMPONENT_REF, make a recursive call to resolve
1139 the inner reference. */
1140 base
= TREE_OPERAND (t
, 0);
1141 switch (TREE_CODE (base
))
1144 if (!TREE_READONLY (base
)
1145 || TREE_CODE (TREE_TYPE (base
)) != RECORD_TYPE
1146 || !targetm
.binds_local_p (base
))
1149 ctor
= DECL_INITIAL (base
);
1154 ctor
= fold_const_aggregate_ref (base
);
1161 if (ctor
== NULL_TREE
1162 || TREE_CODE (ctor
) != CONSTRUCTOR
1163 || !TREE_STATIC (ctor
))
1166 field
= TREE_OPERAND (t
, 1);
1168 FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor
), cnt
, cfield
, cval
)
1170 /* FIXME: Handle bit-fields. */
1171 && ! DECL_BIT_FIELD (cfield
))
1178 tree c
= fold_const_aggregate_ref (TREE_OPERAND (t
, 0));
1179 if (c
&& TREE_CODE (c
) == COMPLEX_CST
)
1180 return fold_build1 (TREE_CODE (t
), TREE_TYPE (t
), c
);
1186 tree base
= TREE_OPERAND (t
, 0);
1187 if (TREE_CODE (base
) == SSA_NAME
1188 && (value
= get_value (base
))
1189 && value
->lattice_val
== CONSTANT
1190 && TREE_CODE (value
->value
) == ADDR_EXPR
)
1191 return fold_const_aggregate_ref (TREE_OPERAND (value
->value
, 0));
1202 /* Evaluate statement STMT. */
1205 evaluate_stmt (tree stmt
)
1208 tree simplified
= NULL_TREE
;
1209 ccp_lattice_t likelyvalue
= likely_value (stmt
);
1212 val
.mem_ref
= NULL_TREE
;
1214 fold_defer_overflow_warnings ();
1216 /* If the statement is likely to have a CONSTANT result, then try
1217 to fold the statement to determine the constant value. */
1218 if (likelyvalue
== CONSTANT
)
1219 simplified
= ccp_fold (stmt
);
1220 /* If the statement is likely to have a VARYING result, then do not
1221 bother folding the statement. */
1222 else if (likelyvalue
== VARYING
)
1223 simplified
= get_rhs (stmt
);
1225 is_constant
= simplified
&& is_gimple_min_invariant (simplified
);
1227 fold_undefer_overflow_warnings (is_constant
, stmt
, 0);
1231 /* The statement produced a constant value. */
1232 val
.lattice_val
= CONSTANT
;
1233 val
.value
= simplified
;
1237 /* The statement produced a nonconstant value. If the statement
1238 had UNDEFINED operands, then the result of the statement
1239 should be UNDEFINED. Otherwise, the statement is VARYING. */
1240 if (likelyvalue
== UNDEFINED
)
1241 val
.lattice_val
= likelyvalue
;
1243 val
.lattice_val
= VARYING
;
1245 val
.value
= NULL_TREE
;
1252 /* Visit the assignment statement STMT. Set the value of its LHS to the
1253 value computed by the RHS and store LHS in *OUTPUT_P. If STMT
1254 creates virtual definitions, set the value of each new name to that
1255 of the RHS (if we can derive a constant out of the RHS). */
1257 static enum ssa_prop_result
1258 visit_assignment (tree stmt
, tree
*output_p
)
1262 enum ssa_prop_result retval
;
1264 lhs
= GIMPLE_STMT_OPERAND (stmt
, 0);
1265 rhs
= GIMPLE_STMT_OPERAND (stmt
, 1);
1267 if (TREE_CODE (rhs
) == SSA_NAME
)
1269 /* For a simple copy operation, we copy the lattice values. */
1270 prop_value_t
*nval
= get_value (rhs
);
1273 else if (do_store_ccp
&& stmt_makes_single_load (stmt
))
1275 /* Same as above, but the RHS is not a gimple register and yet
1276 has a known VUSE. If STMT is loading from the same memory
1277 location that created the SSA_NAMEs for the virtual operands,
1278 we can propagate the value on the RHS. */
1279 prop_value_t
*nval
= get_value_loaded_by (stmt
, const_val
);
1283 && operand_equal_p (nval
->mem_ref
, rhs
, 0))
1286 val
= evaluate_stmt (stmt
);
1289 /* Evaluate the statement. */
1290 val
= evaluate_stmt (stmt
);
1292 /* If the original LHS was a VIEW_CONVERT_EXPR, modify the constant
1293 value to be a VIEW_CONVERT_EXPR of the old constant value.
1295 ??? Also, if this was a definition of a bitfield, we need to widen
1296 the constant value into the type of the destination variable. This
1297 should not be necessary if GCC represented bitfields properly. */
1299 tree orig_lhs
= GIMPLE_STMT_OPERAND (stmt
, 0);
1301 if (TREE_CODE (orig_lhs
) == VIEW_CONVERT_EXPR
1302 && val
.lattice_val
== CONSTANT
)
1304 tree w
= fold_unary (VIEW_CONVERT_EXPR
,
1305 TREE_TYPE (TREE_OPERAND (orig_lhs
, 0)),
1308 orig_lhs
= TREE_OPERAND (orig_lhs
, 0);
1309 if (w
&& is_gimple_min_invariant (w
))
1313 val
.lattice_val
= VARYING
;
1318 if (val
.lattice_val
== CONSTANT
1319 && TREE_CODE (orig_lhs
) == COMPONENT_REF
1320 && DECL_BIT_FIELD (TREE_OPERAND (orig_lhs
, 1)))
1322 tree w
= widen_bitfield (val
.value
, TREE_OPERAND (orig_lhs
, 1),
1325 if (w
&& is_gimple_min_invariant (w
))
1329 val
.lattice_val
= VARYING
;
1330 val
.value
= NULL_TREE
;
1331 val
.mem_ref
= NULL_TREE
;
1336 retval
= SSA_PROP_NOT_INTERESTING
;
1338 /* Set the lattice value of the statement's output. */
1339 if (TREE_CODE (lhs
) == SSA_NAME
)
1341 /* If STMT is an assignment to an SSA_NAME, we only have one
1343 if (set_lattice_value (lhs
, val
))
1346 if (val
.lattice_val
== VARYING
)
1347 retval
= SSA_PROP_VARYING
;
1349 retval
= SSA_PROP_INTERESTING
;
1352 else if (do_store_ccp
&& stmt_makes_single_store (stmt
))
1354 /* Otherwise, set the names in VDEF operands to the new
1355 constant value and mark the LHS as the memory reference
1356 associated with VAL. */
1361 /* Mark VAL as stored in the LHS of this assignment. */
1362 if (val
.lattice_val
== CONSTANT
)
1365 /* Set the value of every VDEF to VAL. */
1367 FOR_EACH_SSA_TREE_OPERAND (vdef
, stmt
, i
, SSA_OP_VIRTUAL_DEFS
)
1369 /* See PR 29801. We may have VDEFs for read-only variables
1370 (see the handling of unmodifiable variables in
1371 add_virtual_operand); do not attempt to change their value. */
1372 if (get_symbol_constant_value (SSA_NAME_VAR (vdef
)) != NULL_TREE
)
1375 changed
|= set_lattice_value (vdef
, val
);
1378 /* Note that for propagation purposes, we are only interested in
1379 visiting statements that load the exact same memory reference
1380 stored here. Those statements will have the exact same list
1381 of virtual uses, so it is enough to set the output of this
1382 statement to be its first virtual definition. */
1383 *output_p
= first_vdef (stmt
);
1386 if (val
.lattice_val
== VARYING
)
1387 retval
= SSA_PROP_VARYING
;
1389 retval
= SSA_PROP_INTERESTING
;
1397 /* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING
1398 if it can determine which edge will be taken. Otherwise, return
1399 SSA_PROP_VARYING. */
1401 static enum ssa_prop_result
1402 visit_cond_stmt (tree stmt
, edge
*taken_edge_p
)
1407 block
= bb_for_stmt (stmt
);
1408 val
= evaluate_stmt (stmt
);
1410 /* Find which edge out of the conditional block will be taken and add it
1411 to the worklist. If no single edge can be determined statically,
1412 return SSA_PROP_VARYING to feed all the outgoing edges to the
1413 propagation engine. */
1414 *taken_edge_p
= val
.value
? find_taken_edge (block
, val
.value
) : 0;
1416 return SSA_PROP_INTERESTING
;
1418 return SSA_PROP_VARYING
;
1422 /* Evaluate statement STMT. If the statement produces an output value and
1423 its evaluation changes the lattice value of its output, return
1424 SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the
1427 If STMT is a conditional branch and we can determine its truth
1428 value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying
1429 value, return SSA_PROP_VARYING. */
1431 static enum ssa_prop_result
1432 ccp_visit_stmt (tree stmt
, edge
*taken_edge_p
, tree
*output_p
)
1437 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1439 fprintf (dump_file
, "\nVisiting statement:\n");
1440 print_generic_stmt (dump_file
, stmt
, dump_flags
);
1441 fprintf (dump_file
, "\n");
1444 if (TREE_CODE (stmt
) == GIMPLE_MODIFY_STMT
)
1446 /* If the statement is an assignment that produces a single
1447 output value, evaluate its RHS to see if the lattice value of
1448 its output has changed. */
1449 return visit_assignment (stmt
, output_p
);
1451 else if (TREE_CODE (stmt
) == COND_EXPR
|| TREE_CODE (stmt
) == SWITCH_EXPR
)
1453 /* If STMT is a conditional branch, see if we can determine
1454 which branch will be taken. */
1455 return visit_cond_stmt (stmt
, taken_edge_p
);
1458 /* Any other kind of statement is not interesting for constant
1459 propagation and, therefore, not worth simulating. */
1460 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1461 fprintf (dump_file
, "No interesting values produced. Marked VARYING.\n");
1463 /* Definitions made by statements other than assignments to
1464 SSA_NAMEs represent unknown modifications to their outputs.
1465 Mark them VARYING. */
1466 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_ALL_DEFS
)
1468 prop_value_t v
= { VARYING
, NULL_TREE
, NULL_TREE
};
1469 set_lattice_value (def
, v
);
1472 return SSA_PROP_VARYING
;
1476 /* Main entry point for SSA Conditional Constant Propagation. */
1479 execute_ssa_ccp (bool store_ccp
)
1481 do_store_ccp
= store_ccp
;
1483 ssa_propagate (ccp_visit_stmt
, ccp_visit_phi_node
);
1484 if (ccp_finalize ())
1485 return (TODO_cleanup_cfg
| TODO_update_ssa
| TODO_remove_unused_locals
);
1494 return execute_ssa_ccp (false);
1501 return flag_tree_ccp
!= 0;
1505 struct gimple_opt_pass pass_ccp
=
1510 gate_ccp
, /* gate */
1511 do_ssa_ccp
, /* execute */
1514 0, /* static_pass_number */
1515 TV_TREE_CCP
, /* tv_id */
1516 PROP_cfg
| PROP_ssa
, /* properties_required */
1517 0, /* properties_provided */
1518 0, /* properties_destroyed */
1519 0, /* todo_flags_start */
1520 TODO_dump_func
| TODO_verify_ssa
1521 | TODO_verify_stmts
| TODO_ggc_collect
/* todo_flags_finish */
1527 do_ssa_store_ccp (void)
1529 /* If STORE-CCP is not enabled, we just run regular CCP. */
1530 return execute_ssa_ccp (flag_tree_store_ccp
!= 0);
1534 gate_store_ccp (void)
1536 /* STORE-CCP is enabled only with -ftree-store-ccp, but when
1537 -fno-tree-store-ccp is specified, we should run regular CCP.
1538 That's why the pass is enabled with either flag. */
1539 return flag_tree_store_ccp
!= 0 || flag_tree_ccp
!= 0;
1543 struct gimple_opt_pass pass_store_ccp
=
1547 "store_ccp", /* name */
1548 gate_store_ccp
, /* gate */
1549 do_ssa_store_ccp
, /* execute */
1552 0, /* static_pass_number */
1553 TV_TREE_STORE_CCP
, /* tv_id */
1554 PROP_cfg
| PROP_ssa
| PROP_alias
, /* properties_required */
1555 0, /* properties_provided */
1556 0, /* properties_destroyed */
1557 0, /* todo_flags_start */
1558 TODO_dump_func
| TODO_verify_ssa
1559 | TODO_verify_stmts
| TODO_ggc_collect
/* todo_flags_finish */
1563 /* Given a constant value VAL for bitfield FIELD, and a destination
1564 variable VAR, return VAL appropriately widened to fit into VAR. If
1565 FIELD is wider than HOST_WIDE_INT, NULL is returned. */
1568 widen_bitfield (tree val
, tree field
, tree var
)
1570 unsigned HOST_WIDE_INT var_size
, field_size
;
1572 unsigned HOST_WIDE_INT mask
;
1575 /* We can only do this if the size of the type and field and VAL are
1576 all constants representable in HOST_WIDE_INT. */
1577 if (!host_integerp (TYPE_SIZE (TREE_TYPE (var
)), 1)
1578 || !host_integerp (DECL_SIZE (field
), 1)
1579 || !host_integerp (val
, 0))
1582 var_size
= tree_low_cst (TYPE_SIZE (TREE_TYPE (var
)), 1);
1583 field_size
= tree_low_cst (DECL_SIZE (field
), 1);
1585 /* Give up if either the bitfield or the variable are too wide. */
1586 if (field_size
> HOST_BITS_PER_WIDE_INT
|| var_size
> HOST_BITS_PER_WIDE_INT
)
1589 gcc_assert (var_size
>= field_size
);
1591 /* If the sign bit of the value is not set or the field's type is unsigned,
1592 just mask off the high order bits of the value. */
1593 if (DECL_UNSIGNED (field
)
1594 || !(tree_low_cst (val
, 0) & (((HOST_WIDE_INT
)1) << (field_size
- 1))))
1596 /* Zero extension. Build a mask with the lower 'field_size' bits
1597 set and a BIT_AND_EXPR node to clear the high order bits of
1599 for (i
= 0, mask
= 0; i
< field_size
; i
++)
1600 mask
|= ((HOST_WIDE_INT
) 1) << i
;
1602 wide_val
= fold_build2 (BIT_AND_EXPR
, TREE_TYPE (var
), val
,
1603 build_int_cst (TREE_TYPE (var
), mask
));
1607 /* Sign extension. Create a mask with the upper 'field_size'
1608 bits set and a BIT_IOR_EXPR to set the high order bits of the
1610 for (i
= 0, mask
= 0; i
< (var_size
- field_size
); i
++)
1611 mask
|= ((HOST_WIDE_INT
) 1) << (var_size
- i
- 1);
1613 wide_val
= fold_build2 (BIT_IOR_EXPR
, TREE_TYPE (var
), val
,
1614 build_int_cst (TREE_TYPE (var
), mask
));
1621 /* A subroutine of fold_stmt_r. Attempts to fold *(A+O) to A[X].
1622 BASE is an array type. OFFSET is a byte displacement. ORIG_TYPE
1623 is the desired result type. */
1626 maybe_fold_offset_to_array_ref (tree base
, tree offset
, tree orig_type
,
1627 bool allow_negative_idx
)
1629 tree min_idx
, idx
, idx_type
, elt_offset
= integer_zero_node
;
1630 tree array_type
, elt_type
, elt_size
;
1633 /* If BASE is an ARRAY_REF, we can pick up another offset (this time
1634 measured in units of the size of elements type) from that ARRAY_REF).
1635 We can't do anything if either is variable.
1637 The case we handle here is *(&A[N]+O). */
1638 if (TREE_CODE (base
) == ARRAY_REF
)
1640 tree low_bound
= array_ref_low_bound (base
);
1642 elt_offset
= TREE_OPERAND (base
, 1);
1643 if (TREE_CODE (low_bound
) != INTEGER_CST
1644 || TREE_CODE (elt_offset
) != INTEGER_CST
)
1647 elt_offset
= int_const_binop (MINUS_EXPR
, elt_offset
, low_bound
, 0);
1648 base
= TREE_OPERAND (base
, 0);
1651 /* Ignore stupid user tricks of indexing non-array variables. */
1652 array_type
= TREE_TYPE (base
);
1653 if (TREE_CODE (array_type
) != ARRAY_TYPE
)
1655 elt_type
= TREE_TYPE (array_type
);
1656 if (!useless_type_conversion_p (orig_type
, elt_type
))
1659 /* Use signed size type for intermediate computation on the index. */
1660 idx_type
= signed_type_for (size_type_node
);
1662 /* If OFFSET and ELT_OFFSET are zero, we don't care about the size of the
1663 element type (so we can use the alignment if it's not constant).
1664 Otherwise, compute the offset as an index by using a division. If the
1665 division isn't exact, then don't do anything. */
1666 elt_size
= TYPE_SIZE_UNIT (elt_type
);
1669 if (integer_zerop (offset
))
1671 if (TREE_CODE (elt_size
) != INTEGER_CST
)
1672 elt_size
= size_int (TYPE_ALIGN (elt_type
));
1674 idx
= build_int_cst (idx_type
, 0);
1678 unsigned HOST_WIDE_INT lquo
, lrem
;
1679 HOST_WIDE_INT hquo
, hrem
;
1682 /* The final array offset should be signed, so we need
1683 to sign-extend the (possibly pointer) offset here
1684 and use signed division. */
1685 soffset
= double_int_sext (tree_to_double_int (offset
),
1686 TYPE_PRECISION (TREE_TYPE (offset
)));
1687 if (TREE_CODE (elt_size
) != INTEGER_CST
1688 || div_and_round_double (TRUNC_DIV_EXPR
, 0,
1689 soffset
.low
, soffset
.high
,
1690 TREE_INT_CST_LOW (elt_size
),
1691 TREE_INT_CST_HIGH (elt_size
),
1692 &lquo
, &hquo
, &lrem
, &hrem
)
1696 idx
= build_int_cst_wide (idx_type
, lquo
, hquo
);
1699 /* Assume the low bound is zero. If there is a domain type, get the
1700 low bound, if any, convert the index into that type, and add the
1702 min_idx
= build_int_cst (idx_type
, 0);
1703 domain_type
= TYPE_DOMAIN (array_type
);
1706 idx_type
= domain_type
;
1707 if (TYPE_MIN_VALUE (idx_type
))
1708 min_idx
= TYPE_MIN_VALUE (idx_type
);
1710 min_idx
= fold_convert (idx_type
, min_idx
);
1712 if (TREE_CODE (min_idx
) != INTEGER_CST
)
1715 elt_offset
= fold_convert (idx_type
, elt_offset
);
1718 if (!integer_zerop (min_idx
))
1719 idx
= int_const_binop (PLUS_EXPR
, idx
, min_idx
, 0);
1720 if (!integer_zerop (elt_offset
))
1721 idx
= int_const_binop (PLUS_EXPR
, idx
, elt_offset
, 0);
1723 /* Make sure to possibly truncate late after offsetting. */
1724 idx
= fold_convert (idx_type
, idx
);
1726 /* We don't want to construct access past array bounds. For example
1729 should not be simplified into (*c)[14] or tree-vrp will
1730 give false warnings. The same is true for
1731 struct A { long x; char d[0]; } *a;
1733 which should be not folded to &a->d[-8]. */
1735 && TYPE_MAX_VALUE (domain_type
)
1736 && TREE_CODE (TYPE_MAX_VALUE (domain_type
)) == INTEGER_CST
)
1738 tree up_bound
= TYPE_MAX_VALUE (domain_type
);
1740 if (tree_int_cst_lt (up_bound
, idx
)
1741 /* Accesses after the end of arrays of size 0 (gcc
1742 extension) and 1 are likely intentional ("struct
1744 && compare_tree_int (up_bound
, 1) > 0)
1748 && TYPE_MIN_VALUE (domain_type
))
1750 if (!allow_negative_idx
1751 && TREE_CODE (TYPE_MIN_VALUE (domain_type
)) == INTEGER_CST
1752 && tree_int_cst_lt (idx
, TYPE_MIN_VALUE (domain_type
)))
1755 else if (!allow_negative_idx
1756 && compare_tree_int (idx
, 0) < 0)
1759 return build4 (ARRAY_REF
, elt_type
, base
, idx
, NULL_TREE
, NULL_TREE
);
1763 /* Attempt to fold *(S+O) to S.X.
1764 BASE is a record type. OFFSET is a byte displacement. ORIG_TYPE
1765 is the desired result type. */
1768 maybe_fold_offset_to_component_ref (tree record_type
, tree base
, tree offset
,
1769 tree orig_type
, bool base_is_ptr
)
1771 tree f
, t
, field_type
, tail_array_field
, field_offset
;
1775 if (TREE_CODE (record_type
) != RECORD_TYPE
1776 && TREE_CODE (record_type
) != UNION_TYPE
1777 && TREE_CODE (record_type
) != QUAL_UNION_TYPE
)
1780 /* Short-circuit silly cases. */
1781 if (useless_type_conversion_p (record_type
, orig_type
))
1784 tail_array_field
= NULL_TREE
;
1785 for (f
= TYPE_FIELDS (record_type
); f
; f
= TREE_CHAIN (f
))
1789 if (TREE_CODE (f
) != FIELD_DECL
)
1791 if (DECL_BIT_FIELD (f
))
1794 if (!DECL_FIELD_OFFSET (f
))
1796 field_offset
= byte_position (f
);
1797 if (TREE_CODE (field_offset
) != INTEGER_CST
)
1800 /* ??? Java creates "interesting" fields for representing base classes.
1801 They have no name, and have no context. With no context, we get into
1802 trouble with nonoverlapping_component_refs_p. Skip them. */
1803 if (!DECL_FIELD_CONTEXT (f
))
1806 /* The previous array field isn't at the end. */
1807 tail_array_field
= NULL_TREE
;
1809 /* Check to see if this offset overlaps with the field. */
1810 cmp
= tree_int_cst_compare (field_offset
, offset
);
1814 field_type
= TREE_TYPE (f
);
1816 /* Here we exactly match the offset being checked. If the types match,
1817 then we can return that field. */
1819 && useless_type_conversion_p (orig_type
, field_type
))
1822 base
= build1 (INDIRECT_REF
, record_type
, base
);
1823 t
= build3 (COMPONENT_REF
, field_type
, base
, f
, NULL_TREE
);
1827 /* Don't care about offsets into the middle of scalars. */
1828 if (!AGGREGATE_TYPE_P (field_type
))
1831 /* Check for array at the end of the struct. This is often
1832 used as for flexible array members. We should be able to
1833 turn this into an array access anyway. */
1834 if (TREE_CODE (field_type
) == ARRAY_TYPE
)
1835 tail_array_field
= f
;
1837 /* Check the end of the field against the offset. */
1838 if (!DECL_SIZE_UNIT (f
)
1839 || TREE_CODE (DECL_SIZE_UNIT (f
)) != INTEGER_CST
)
1841 t
= int_const_binop (MINUS_EXPR
, offset
, field_offset
, 1);
1842 if (!tree_int_cst_lt (t
, DECL_SIZE_UNIT (f
)))
1845 /* If we matched, then set offset to the displacement into
1848 new_base
= build1 (INDIRECT_REF
, record_type
, base
);
1851 new_base
= build3 (COMPONENT_REF
, field_type
, new_base
, f
, NULL_TREE
);
1853 /* Recurse to possibly find the match. */
1854 ret
= maybe_fold_offset_to_array_ref (new_base
, t
, orig_type
,
1855 f
== TYPE_FIELDS (record_type
));
1858 ret
= maybe_fold_offset_to_component_ref (field_type
, new_base
, t
,
1864 if (!tail_array_field
)
1867 f
= tail_array_field
;
1868 field_type
= TREE_TYPE (f
);
1869 offset
= int_const_binop (MINUS_EXPR
, offset
, byte_position (f
), 1);
1871 /* If we get here, we've got an aggregate field, and a possibly
1872 nonzero offset into them. Recurse and hope for a valid match. */
1874 base
= build1 (INDIRECT_REF
, record_type
, base
);
1875 base
= build3 (COMPONENT_REF
, field_type
, base
, f
, NULL_TREE
);
1877 t
= maybe_fold_offset_to_array_ref (base
, offset
, orig_type
,
1878 f
== TYPE_FIELDS (record_type
));
1881 return maybe_fold_offset_to_component_ref (field_type
, base
, offset
,
1885 /* Attempt to express (ORIG_TYPE)BASE+OFFSET as BASE->field_of_orig_type
1886 or BASE[index] or by combination of those.
1888 Before attempting the conversion strip off existing ADDR_EXPRs and
1889 handled component refs. */
1892 maybe_fold_offset_to_reference (tree base
, tree offset
, tree orig_type
)
1896 bool base_is_ptr
= true;
1899 if (TREE_CODE (base
) == ADDR_EXPR
)
1901 base_is_ptr
= false;
1903 base
= TREE_OPERAND (base
, 0);
1905 /* Handle case where existing COMPONENT_REF pick e.g. wrong field of union,
1906 so it needs to be removed and new COMPONENT_REF constructed.
1907 The wrong COMPONENT_REF are often constructed by folding the
1908 (type *)&object within the expression (type *)&object+offset */
1909 if (handled_component_p (base
) && 0)
1911 HOST_WIDE_INT sub_offset
, size
, maxsize
;
1913 newbase
= get_ref_base_and_extent (base
, &sub_offset
,
1915 gcc_assert (newbase
);
1916 gcc_assert (!(sub_offset
& (BITS_PER_UNIT
- 1)));
1917 if (size
== maxsize
)
1921 offset
= int_const_binop (PLUS_EXPR
, offset
,
1922 build_int_cst (TREE_TYPE (offset
),
1923 sub_offset
/ BITS_PER_UNIT
), 1);
1926 if (useless_type_conversion_p (orig_type
, TREE_TYPE (base
))
1927 && integer_zerop (offset
))
1929 type
= TREE_TYPE (base
);
1934 if (!POINTER_TYPE_P (TREE_TYPE (base
)))
1936 type
= TREE_TYPE (TREE_TYPE (base
));
1938 ret
= maybe_fold_offset_to_component_ref (type
, base
, offset
,
1939 orig_type
, base_is_ptr
);
1943 base
= build1 (INDIRECT_REF
, type
, base
);
1944 ret
= maybe_fold_offset_to_array_ref (base
, offset
, orig_type
, true);
1949 /* A subroutine of fold_stmt_r. Attempt to simplify *(BASE+OFFSET).
1950 Return the simplified expression, or NULL if nothing could be done. */
1953 maybe_fold_stmt_indirect (tree expr
, tree base
, tree offset
)
1956 bool volatile_p
= TREE_THIS_VOLATILE (expr
);
1958 /* We may well have constructed a double-nested PLUS_EXPR via multiple
1959 substitutions. Fold that down to one. Remove NON_LVALUE_EXPRs that
1960 are sometimes added. */
1962 STRIP_TYPE_NOPS (base
);
1963 TREE_OPERAND (expr
, 0) = base
;
1965 /* One possibility is that the address reduces to a string constant. */
1966 t
= fold_read_from_constant_string (expr
);
1970 /* Add in any offset from a POINTER_PLUS_EXPR. */
1971 if (TREE_CODE (base
) == POINTER_PLUS_EXPR
)
1975 offset2
= TREE_OPERAND (base
, 1);
1976 if (TREE_CODE (offset2
) != INTEGER_CST
)
1978 base
= TREE_OPERAND (base
, 0);
1980 offset
= fold_convert (sizetype
,
1981 int_const_binop (PLUS_EXPR
, offset
, offset2
, 1));
1984 if (TREE_CODE (base
) == ADDR_EXPR
)
1986 tree base_addr
= base
;
1988 /* Strip the ADDR_EXPR. */
1989 base
= TREE_OPERAND (base
, 0);
1991 /* Fold away CONST_DECL to its value, if the type is scalar. */
1992 if (TREE_CODE (base
) == CONST_DECL
1993 && ccp_decl_initial_min_invariant (DECL_INITIAL (base
)))
1994 return DECL_INITIAL (base
);
1996 /* Try folding *(&B+O) to B.X. */
1997 t
= maybe_fold_offset_to_reference (base_addr
, offset
,
2001 TREE_THIS_VOLATILE (t
) = volatile_p
;
2007 /* We can get here for out-of-range string constant accesses,
2008 such as "_"[3]. Bail out of the entire substitution search
2009 and arrange for the entire statement to be replaced by a
2010 call to __builtin_trap. In all likelihood this will all be
2011 constant-folded away, but in the meantime we can't leave with
2012 something that get_expr_operands can't understand. */
2016 if (TREE_CODE (t
) == ADDR_EXPR
2017 && TREE_CODE (TREE_OPERAND (t
, 0)) == STRING_CST
)
2019 /* FIXME: Except that this causes problems elsewhere with dead
2020 code not being deleted, and we die in the rtl expanders
2021 because we failed to remove some ssa_name. In the meantime,
2022 just return zero. */
2023 /* FIXME2: This condition should be signaled by
2024 fold_read_from_constant_string directly, rather than
2025 re-checking for it here. */
2026 return integer_zero_node
;
2029 /* Try folding *(B+O) to B->X. Still an improvement. */
2030 if (POINTER_TYPE_P (TREE_TYPE (base
)))
2032 t
= maybe_fold_offset_to_reference (base
, offset
,
2039 /* Otherwise we had an offset that we could not simplify. */
2044 /* A subroutine of fold_stmt_r. EXPR is a POINTER_PLUS_EXPR.
2046 A quaint feature extant in our address arithmetic is that there
2047 can be hidden type changes here. The type of the result need
2048 not be the same as the type of the input pointer.
2050 What we're after here is an expression of the form
2051 (T *)(&array + const)
2052 where the cast doesn't actually exist, but is implicit in the
2053 type of the POINTER_PLUS_EXPR. We'd like to turn this into
2055 which may be able to propagate further. */
2058 maybe_fold_stmt_addition (tree expr
)
2060 tree op0
= TREE_OPERAND (expr
, 0);
2061 tree op1
= TREE_OPERAND (expr
, 1);
2062 tree ptr_type
= TREE_TYPE (expr
);
2066 gcc_assert (TREE_CODE (expr
) == POINTER_PLUS_EXPR
);
2068 /* It had better be a constant. */
2069 if (TREE_CODE (op1
) != INTEGER_CST
)
2071 /* The first operand should be an ADDR_EXPR. */
2072 if (TREE_CODE (op0
) != ADDR_EXPR
)
2074 op0
= TREE_OPERAND (op0
, 0);
2076 /* If the first operand is an ARRAY_REF, expand it so that we can fold
2077 the offset into it. */
2078 while (TREE_CODE (op0
) == ARRAY_REF
)
2080 tree array_obj
= TREE_OPERAND (op0
, 0);
2081 tree array_idx
= TREE_OPERAND (op0
, 1);
2082 tree elt_type
= TREE_TYPE (op0
);
2083 tree elt_size
= TYPE_SIZE_UNIT (elt_type
);
2086 if (TREE_CODE (array_idx
) != INTEGER_CST
)
2088 if (TREE_CODE (elt_size
) != INTEGER_CST
)
2091 /* Un-bias the index by the min index of the array type. */
2092 min_idx
= TYPE_DOMAIN (TREE_TYPE (array_obj
));
2095 min_idx
= TYPE_MIN_VALUE (min_idx
);
2098 if (TREE_CODE (min_idx
) != INTEGER_CST
)
2101 array_idx
= fold_convert (TREE_TYPE (min_idx
), array_idx
);
2102 if (!integer_zerop (min_idx
))
2103 array_idx
= int_const_binop (MINUS_EXPR
, array_idx
,
2108 /* Convert the index to a byte offset. */
2109 array_idx
= fold_convert (sizetype
, array_idx
);
2110 array_idx
= int_const_binop (MULT_EXPR
, array_idx
, elt_size
, 0);
2112 /* Update the operands for the next round, or for folding. */
2113 op1
= int_const_binop (PLUS_EXPR
,
2118 ptd_type
= TREE_TYPE (ptr_type
);
2119 /* If we want a pointer to void, reconstruct the reference from the
2120 array element type. A pointer to that can be trivially converted
2121 to void *. This happens as we fold (void *)(ptr p+ off). */
2122 if (VOID_TYPE_P (ptd_type
)
2123 && TREE_CODE (TREE_TYPE (op0
)) == ARRAY_TYPE
)
2124 ptd_type
= TREE_TYPE (TREE_TYPE (op0
));
2126 /* At which point we can try some of the same things as for indirects. */
2127 t
= maybe_fold_offset_to_array_ref (op0
, op1
, ptd_type
, true);
2129 t
= maybe_fold_offset_to_component_ref (TREE_TYPE (op0
), op0
, op1
,
2132 t
= build1 (ADDR_EXPR
, ptr_type
, t
);
2137 /* For passing state through walk_tree into fold_stmt_r and its
2140 struct fold_stmt_r_data
2144 bool *inside_addr_expr_p
;
2147 /* Subroutine of fold_stmt called via walk_tree. We perform several
2148 simplifications of EXPR_P, mostly having to do with pointer arithmetic. */
2151 fold_stmt_r (tree
*expr_p
, int *walk_subtrees
, void *data
)
2153 struct fold_stmt_r_data
*fold_stmt_r_data
= (struct fold_stmt_r_data
*) data
;
2154 bool *inside_addr_expr_p
= fold_stmt_r_data
->inside_addr_expr_p
;
2155 bool *changed_p
= fold_stmt_r_data
->changed_p
;
2156 tree expr
= *expr_p
, t
;
2157 bool volatile_p
= TREE_THIS_VOLATILE (expr
);
2159 /* ??? It'd be nice if walk_tree had a pre-order option. */
2160 switch (TREE_CODE (expr
))
2163 t
= walk_tree (&TREE_OPERAND (expr
, 0), fold_stmt_r
, data
, NULL
);
2168 t
= maybe_fold_stmt_indirect (expr
, TREE_OPERAND (expr
, 0),
2171 && TREE_CODE (TREE_OPERAND (expr
, 0)) == ADDR_EXPR
)
2172 /* If we had a good reason for propagating the address here,
2173 make sure we end up with valid gimple. See PR34989. */
2174 t
= TREE_OPERAND (TREE_OPERAND (expr
, 0), 0);
2178 t
= walk_tree (&TREE_OPERAND (expr
, 0), fold_stmt_r
, data
, NULL
);
2183 if (POINTER_TYPE_P (TREE_TYPE (expr
))
2184 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (expr
, 0)))
2185 && (t
= maybe_fold_offset_to_reference
2186 (TREE_OPERAND (expr
, 0),
2188 TREE_TYPE (TREE_TYPE (expr
)))))
2190 tree ptr_type
= build_pointer_type (TREE_TYPE (t
));
2191 if (!useless_type_conversion_p (TREE_TYPE (expr
), ptr_type
))
2193 t
= build_fold_addr_expr_with_type (t
, ptr_type
);
2197 /* ??? Could handle more ARRAY_REFs here, as a variant of INDIRECT_REF.
2198 We'd only want to bother decomposing an existing ARRAY_REF if
2199 the base array is found to have another offset contained within.
2200 Otherwise we'd be wasting time. */
2202 /* If we are not processing expressions found within an
2203 ADDR_EXPR, then we can fold constant array references. */
2204 if (!*inside_addr_expr_p
)
2205 t
= fold_read_from_constant_string (expr
);
2211 *inside_addr_expr_p
= true;
2212 t
= walk_tree (&TREE_OPERAND (expr
, 0), fold_stmt_r
, data
, NULL
);
2213 *inside_addr_expr_p
= false;
2218 /* Set TREE_INVARIANT properly so that the value is properly
2219 considered constant, and so gets propagated as expected. */
2221 recompute_tree_invariant_for_addr_expr (expr
);
2224 case POINTER_PLUS_EXPR
:
2225 t
= walk_tree (&TREE_OPERAND (expr
, 0), fold_stmt_r
, data
, NULL
);
2228 t
= walk_tree (&TREE_OPERAND (expr
, 1), fold_stmt_r
, data
, NULL
);
2233 t
= maybe_fold_stmt_addition (expr
);
2237 t
= walk_tree (&TREE_OPERAND (expr
, 0), fold_stmt_r
, data
, NULL
);
2242 /* Make sure the FIELD_DECL is actually a field in the type on the lhs.
2243 We've already checked that the records are compatible, so we should
2244 come up with a set of compatible fields. */
2246 tree expr_record
= TREE_TYPE (TREE_OPERAND (expr
, 0));
2247 tree expr_field
= TREE_OPERAND (expr
, 1);
2249 if (DECL_FIELD_CONTEXT (expr_field
) != TYPE_MAIN_VARIANT (expr_record
))
2251 expr_field
= find_compatible_field (expr_record
, expr_field
);
2252 TREE_OPERAND (expr
, 1) = expr_field
;
2257 case TARGET_MEM_REF
:
2258 t
= maybe_fold_tmr (expr
);
2262 if (COMPARISON_CLASS_P (TREE_OPERAND (expr
, 0)))
2264 tree op0
= TREE_OPERAND (expr
, 0);
2268 fold_defer_overflow_warnings ();
2269 tem
= fold_binary (TREE_CODE (op0
), TREE_TYPE (op0
),
2270 TREE_OPERAND (op0
, 0),
2271 TREE_OPERAND (op0
, 1));
2272 set
= tem
&& set_rhs (expr_p
, tem
);
2273 fold_undefer_overflow_warnings (set
, fold_stmt_r_data
->stmt
, 0);
2288 /* Preserve volatileness of the original expression. */
2289 TREE_THIS_VOLATILE (t
) = volatile_p
;
2298 /* Return the string length, maximum string length or maximum value of
2300 If ARG is an SSA name variable, follow its use-def chains. If LENGTH
2301 is not NULL and, for TYPE == 0, its value is not equal to the length
2302 we determine or if we are unable to determine the length or value,
2303 return false. VISITED is a bitmap of visited variables.
2304 TYPE is 0 if string length should be returned, 1 for maximum string
2305 length and 2 for maximum value ARG can have. */
2308 get_maxval_strlen (tree arg
, tree
*length
, bitmap visited
, int type
)
2310 tree var
, def_stmt
, val
;
2312 if (TREE_CODE (arg
) != SSA_NAME
)
2314 if (TREE_CODE (arg
) == COND_EXPR
)
2315 return get_maxval_strlen (COND_EXPR_THEN (arg
), length
, visited
, type
)
2316 && get_maxval_strlen (COND_EXPR_ELSE (arg
), length
, visited
, type
);
2317 /* We can end up with &(*iftmp_1)[0] here as well, so handle it. */
2318 else if (TREE_CODE (arg
) == ADDR_EXPR
2319 && TREE_CODE (TREE_OPERAND (arg
, 0)) == ARRAY_REF
2320 && integer_zerop (TREE_OPERAND (TREE_OPERAND (arg
, 0), 1)))
2322 tree aop0
= TREE_OPERAND (TREE_OPERAND (arg
, 0), 0);
2323 if (TREE_CODE (aop0
) == INDIRECT_REF
2324 && TREE_CODE (TREE_OPERAND (aop0
, 0)) == SSA_NAME
)
2325 return get_maxval_strlen (TREE_OPERAND (aop0
, 0),
2326 length
, visited
, type
);
2332 if (TREE_CODE (val
) != INTEGER_CST
2333 || tree_int_cst_sgn (val
) < 0)
2337 val
= c_strlen (arg
, 1);
2345 if (TREE_CODE (*length
) != INTEGER_CST
2346 || TREE_CODE (val
) != INTEGER_CST
)
2349 if (tree_int_cst_lt (*length
, val
))
2353 else if (simple_cst_equal (val
, *length
) != 1)
2361 /* If we were already here, break the infinite cycle. */
2362 if (bitmap_bit_p (visited
, SSA_NAME_VERSION (arg
)))
2364 bitmap_set_bit (visited
, SSA_NAME_VERSION (arg
));
2367 def_stmt
= SSA_NAME_DEF_STMT (var
);
2369 switch (TREE_CODE (def_stmt
))
2371 case GIMPLE_MODIFY_STMT
:
2375 /* The RHS of the statement defining VAR must either have a
2376 constant length or come from another SSA_NAME with a constant
2378 rhs
= GIMPLE_STMT_OPERAND (def_stmt
, 1);
2380 return get_maxval_strlen (rhs
, length
, visited
, type
);
2385 /* All the arguments of the PHI node must have the same constant
2389 for (i
= 0; i
< PHI_NUM_ARGS (def_stmt
); i
++)
2391 tree arg
= PHI_ARG_DEF (def_stmt
, i
);
2393 /* If this PHI has itself as an argument, we cannot
2394 determine the string length of this argument. However,
2395 if we can find a constant string length for the other
2396 PHI args then we can still be sure that this is a
2397 constant string length. So be optimistic and just
2398 continue with the next argument. */
2399 if (arg
== PHI_RESULT (def_stmt
))
2402 if (!get_maxval_strlen (arg
, length
, visited
, type
))
2418 /* Fold builtin call FN in statement STMT. If it cannot be folded into a
2419 constant, return NULL_TREE. Otherwise, return its constant value. */
2422 ccp_fold_builtin (tree stmt
, tree fn
)
2424 tree result
, val
[3];
2426 int arg_mask
, i
, type
;
2429 call_expr_arg_iterator iter
;
2432 ignore
= TREE_CODE (stmt
) != GIMPLE_MODIFY_STMT
;
2434 /* First try the generic builtin folder. If that succeeds, return the
2436 result
= fold_call_expr (fn
, ignore
);
2440 STRIP_NOPS (result
);
2444 /* Ignore MD builtins. */
2445 callee
= get_callee_fndecl (fn
);
2446 if (DECL_BUILT_IN_CLASS (callee
) == BUILT_IN_MD
)
2449 /* If the builtin could not be folded, and it has no argument list,
2451 nargs
= call_expr_nargs (fn
);
2455 /* Limit the work only for builtins we know how to simplify. */
2456 switch (DECL_FUNCTION_CODE (callee
))
2458 case BUILT_IN_STRLEN
:
2459 case BUILT_IN_FPUTS
:
2460 case BUILT_IN_FPUTS_UNLOCKED
:
2464 case BUILT_IN_STRCPY
:
2465 case BUILT_IN_STRNCPY
:
2469 case BUILT_IN_MEMCPY_CHK
:
2470 case BUILT_IN_MEMPCPY_CHK
:
2471 case BUILT_IN_MEMMOVE_CHK
:
2472 case BUILT_IN_MEMSET_CHK
:
2473 case BUILT_IN_STRNCPY_CHK
:
2477 case BUILT_IN_STRCPY_CHK
:
2478 case BUILT_IN_STPCPY_CHK
:
2482 case BUILT_IN_SNPRINTF_CHK
:
2483 case BUILT_IN_VSNPRINTF_CHK
:
2491 /* Try to use the dataflow information gathered by the CCP process. */
2492 visited
= BITMAP_ALLOC (NULL
);
2494 memset (val
, 0, sizeof (val
));
2495 init_call_expr_arg_iterator (fn
, &iter
);
2496 for (i
= 0; arg_mask
; i
++, arg_mask
>>= 1)
2498 a
= next_call_expr_arg (&iter
);
2501 bitmap_clear (visited
);
2502 if (!get_maxval_strlen (a
, &val
[i
], visited
, type
))
2507 BITMAP_FREE (visited
);
2510 switch (DECL_FUNCTION_CODE (callee
))
2512 case BUILT_IN_STRLEN
:
2515 tree new_val
= fold_convert (TREE_TYPE (fn
), val
[0]);
2517 /* If the result is not a valid gimple value, or not a cast
2518 of a valid gimple value, then we can not use the result. */
2519 if (is_gimple_val (new_val
)
2520 || (is_gimple_cast (new_val
)
2521 && is_gimple_val (TREE_OPERAND (new_val
, 0))))
2526 case BUILT_IN_STRCPY
:
2527 if (val
[1] && is_gimple_val (val
[1]) && nargs
== 2)
2528 result
= fold_builtin_strcpy (callee
,
2529 CALL_EXPR_ARG (fn
, 0),
2530 CALL_EXPR_ARG (fn
, 1),
2534 case BUILT_IN_STRNCPY
:
2535 if (val
[1] && is_gimple_val (val
[1]) && nargs
== 3)
2536 result
= fold_builtin_strncpy (callee
,
2537 CALL_EXPR_ARG (fn
, 0),
2538 CALL_EXPR_ARG (fn
, 1),
2539 CALL_EXPR_ARG (fn
, 2),
2543 case BUILT_IN_FPUTS
:
2544 result
= fold_builtin_fputs (CALL_EXPR_ARG (fn
, 0),
2545 CALL_EXPR_ARG (fn
, 1),
2546 TREE_CODE (stmt
) != GIMPLE_MODIFY_STMT
, 0,
2550 case BUILT_IN_FPUTS_UNLOCKED
:
2551 result
= fold_builtin_fputs (CALL_EXPR_ARG (fn
, 0),
2552 CALL_EXPR_ARG (fn
, 1),
2553 TREE_CODE (stmt
) != GIMPLE_MODIFY_STMT
, 1,
2557 case BUILT_IN_MEMCPY_CHK
:
2558 case BUILT_IN_MEMPCPY_CHK
:
2559 case BUILT_IN_MEMMOVE_CHK
:
2560 case BUILT_IN_MEMSET_CHK
:
2561 if (val
[2] && is_gimple_val (val
[2]))
2562 result
= fold_builtin_memory_chk (callee
,
2563 CALL_EXPR_ARG (fn
, 0),
2564 CALL_EXPR_ARG (fn
, 1),
2565 CALL_EXPR_ARG (fn
, 2),
2566 CALL_EXPR_ARG (fn
, 3),
2568 DECL_FUNCTION_CODE (callee
));
2571 case BUILT_IN_STRCPY_CHK
:
2572 case BUILT_IN_STPCPY_CHK
:
2573 if (val
[1] && is_gimple_val (val
[1]))
2574 result
= fold_builtin_stxcpy_chk (callee
,
2575 CALL_EXPR_ARG (fn
, 0),
2576 CALL_EXPR_ARG (fn
, 1),
2577 CALL_EXPR_ARG (fn
, 2),
2579 DECL_FUNCTION_CODE (callee
));
2582 case BUILT_IN_STRNCPY_CHK
:
2583 if (val
[2] && is_gimple_val (val
[2]))
2584 result
= fold_builtin_strncpy_chk (CALL_EXPR_ARG (fn
, 0),
2585 CALL_EXPR_ARG (fn
, 1),
2586 CALL_EXPR_ARG (fn
, 2),
2587 CALL_EXPR_ARG (fn
, 3),
2591 case BUILT_IN_SNPRINTF_CHK
:
2592 case BUILT_IN_VSNPRINTF_CHK
:
2593 if (val
[1] && is_gimple_val (val
[1]))
2594 result
= fold_builtin_snprintf_chk (fn
, val
[1],
2595 DECL_FUNCTION_CODE (callee
));
2602 if (result
&& ignore
)
2603 result
= fold_ignored_result (result
);
2608 /* Fold the statement pointed to by STMT_P. In some cases, this function may
2609 replace the whole statement with a new one. Returns true iff folding
2610 makes any changes. */
2613 fold_stmt (tree
*stmt_p
)
2615 tree rhs
, result
, stmt
;
2616 struct fold_stmt_r_data fold_stmt_r_data
;
2617 bool changed
= false;
2618 bool inside_addr_expr
= false;
2622 fold_stmt_r_data
.stmt
= stmt
;
2623 fold_stmt_r_data
.changed_p
= &changed
;
2624 fold_stmt_r_data
.inside_addr_expr_p
= &inside_addr_expr
;
2626 /* If we replaced constants and the statement makes pointer dereferences,
2627 then we may need to fold instances of *&VAR into VAR, etc. */
2628 if (walk_tree (stmt_p
, fold_stmt_r
, &fold_stmt_r_data
, NULL
))
2630 *stmt_p
= build_call_expr (implicit_built_in_decls
[BUILT_IN_TRAP
], 0);
2634 rhs
= get_rhs (stmt
);
2639 if (TREE_CODE (rhs
) == CALL_EXPR
)
2643 /* Check for builtins that CCP can handle using information not
2644 available in the generic fold routines. */
2645 callee
= get_callee_fndecl (rhs
);
2646 if (callee
&& DECL_BUILT_IN (callee
))
2647 result
= ccp_fold_builtin (stmt
, rhs
);
2650 /* Check for resolvable OBJ_TYPE_REF. The only sorts we can resolve
2651 here are when we've propagated the address of a decl into the
2653 /* ??? Should perhaps do this in fold proper. However, doing it
2654 there requires that we create a new CALL_EXPR, and that requires
2655 copying EH region info to the new node. Easier to just do it
2656 here where we can just smash the call operand. Also
2657 CALL_EXPR_RETURN_SLOT_OPT needs to be handled correctly and
2658 copied, fold_call_expr does not have not information. */
2659 callee
= CALL_EXPR_FN (rhs
);
2660 if (TREE_CODE (callee
) == OBJ_TYPE_REF
2661 && lang_hooks
.fold_obj_type_ref
2662 && TREE_CODE (OBJ_TYPE_REF_OBJECT (callee
)) == ADDR_EXPR
2663 && DECL_P (TREE_OPERAND
2664 (OBJ_TYPE_REF_OBJECT (callee
), 0)))
2668 /* ??? Caution: Broken ADDR_EXPR semantics means that
2669 looking at the type of the operand of the addr_expr
2670 can yield an array type. See silly exception in
2671 check_pointer_types_r. */
2673 t
= TREE_TYPE (TREE_TYPE (OBJ_TYPE_REF_OBJECT (callee
)));
2674 t
= lang_hooks
.fold_obj_type_ref (callee
, t
);
2677 CALL_EXPR_FN (rhs
) = t
;
2683 else if (TREE_CODE (rhs
) == COND_EXPR
)
2685 tree temp
= fold (COND_EXPR_COND (rhs
));
2686 if (temp
!= COND_EXPR_COND (rhs
))
2687 result
= fold_build3 (COND_EXPR
, TREE_TYPE (rhs
), temp
,
2688 COND_EXPR_THEN (rhs
), COND_EXPR_ELSE (rhs
));
2691 /* If we couldn't fold the RHS, hand over to the generic fold routines. */
2692 if (result
== NULL_TREE
)
2693 result
= fold (rhs
);
2695 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
2696 may have been added by fold, and "useless" type conversions that might
2697 now be apparent due to propagation. */
2698 STRIP_USELESS_TYPE_CONVERSION (result
);
2701 changed
|= set_rhs (stmt_p
, result
);
2706 /* Perform the minimal folding on statement STMT. Only operations like
2707 *&x created by constant propagation are handled. The statement cannot
2708 be replaced with a new one. */
2711 fold_stmt_inplace (tree stmt
)
2713 tree old_stmt
= stmt
, rhs
, new_rhs
;
2714 struct fold_stmt_r_data fold_stmt_r_data
;
2715 bool changed
= false;
2716 bool inside_addr_expr
= false;
2718 fold_stmt_r_data
.stmt
= stmt
;
2719 fold_stmt_r_data
.changed_p
= &changed
;
2720 fold_stmt_r_data
.inside_addr_expr_p
= &inside_addr_expr
;
2722 walk_tree (&stmt
, fold_stmt_r
, &fold_stmt_r_data
, NULL
);
2723 gcc_assert (stmt
== old_stmt
);
2725 rhs
= get_rhs (stmt
);
2726 if (!rhs
|| rhs
== stmt
)
2729 new_rhs
= fold (rhs
);
2730 STRIP_USELESS_TYPE_CONVERSION (new_rhs
);
2734 changed
|= set_rhs (&stmt
, new_rhs
);
2735 gcc_assert (stmt
== old_stmt
);
2740 /* Try to optimize out __builtin_stack_restore. Optimize it out
2741 if there is another __builtin_stack_restore in the same basic
2742 block and no calls or ASM_EXPRs are in between, or if this block's
2743 only outgoing edge is to EXIT_BLOCK and there are no calls or
2744 ASM_EXPRs after this __builtin_stack_restore. */
2747 optimize_stack_restore (basic_block bb
, tree call
, block_stmt_iterator i
)
2749 tree stack_save
, stmt
, callee
;
2751 if (TREE_CODE (call
) != CALL_EXPR
2752 || call_expr_nargs (call
) != 1
2753 || TREE_CODE (CALL_EXPR_ARG (call
, 0)) != SSA_NAME
2754 || !POINTER_TYPE_P (TREE_TYPE (CALL_EXPR_ARG (call
, 0))))
2757 for (bsi_next (&i
); !bsi_end_p (i
); bsi_next (&i
))
2761 stmt
= bsi_stmt (i
);
2762 if (TREE_CODE (stmt
) == ASM_EXPR
)
2764 call
= get_call_expr_in (stmt
);
2768 callee
= get_callee_fndecl (call
);
2769 if (!callee
|| DECL_BUILT_IN_CLASS (callee
) != BUILT_IN_NORMAL
)
2772 if (DECL_FUNCTION_CODE (callee
) == BUILT_IN_STACK_RESTORE
)
2777 && (! single_succ_p (bb
)
2778 || single_succ_edge (bb
)->dest
!= EXIT_BLOCK_PTR
))
2781 stack_save
= SSA_NAME_DEF_STMT (CALL_EXPR_ARG (call
, 0));
2782 if (TREE_CODE (stack_save
) != GIMPLE_MODIFY_STMT
2783 || GIMPLE_STMT_OPERAND (stack_save
, 0) != CALL_EXPR_ARG (call
, 0)
2784 || TREE_CODE (GIMPLE_STMT_OPERAND (stack_save
, 1)) != CALL_EXPR
2785 || tree_could_throw_p (stack_save
)
2786 || !has_single_use (CALL_EXPR_ARG (call
, 0)))
2789 callee
= get_callee_fndecl (GIMPLE_STMT_OPERAND (stack_save
, 1));
2791 || DECL_BUILT_IN_CLASS (callee
) != BUILT_IN_NORMAL
2792 || DECL_FUNCTION_CODE (callee
) != BUILT_IN_STACK_SAVE
2793 || call_expr_nargs (GIMPLE_STMT_OPERAND (stack_save
, 1)) != 0)
2797 push_stmt_changes (&stmt
);
2798 if (!set_rhs (&stmt
,
2799 build_int_cst (TREE_TYPE (CALL_EXPR_ARG (call
, 0)), 0)))
2801 discard_stmt_changes (&stmt
);
2804 gcc_assert (stmt
== stack_save
);
2805 pop_stmt_changes (&stmt
);
2807 return integer_zero_node
;
2810 /* If va_list type is a simple pointer and nothing special is needed,
2811 optimize __builtin_va_start (&ap, 0) into ap = __builtin_next_arg (0),
2812 __builtin_va_end (&ap) out as NOP and __builtin_va_copy into a simple
2813 pointer assignment. */
2816 optimize_stdarg_builtin (tree call
)
2818 tree callee
, lhs
, rhs
;
2819 bool va_list_simple_ptr
;
2821 if (TREE_CODE (call
) != CALL_EXPR
)
2824 va_list_simple_ptr
= POINTER_TYPE_P (va_list_type_node
)
2825 && (TREE_TYPE (va_list_type_node
) == void_type_node
2826 || TREE_TYPE (va_list_type_node
) == char_type_node
);
2828 callee
= get_callee_fndecl (call
);
2829 switch (DECL_FUNCTION_CODE (callee
))
2831 case BUILT_IN_VA_START
:
2832 if (!va_list_simple_ptr
2833 || targetm
.expand_builtin_va_start
!= NULL
2834 || built_in_decls
[BUILT_IN_NEXT_ARG
] == NULL
)
2837 if (call_expr_nargs (call
) != 2)
2840 lhs
= CALL_EXPR_ARG (call
, 0);
2841 if (!POINTER_TYPE_P (TREE_TYPE (lhs
))
2842 || TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs
)))
2843 != TYPE_MAIN_VARIANT (va_list_type_node
))
2846 lhs
= build_fold_indirect_ref (lhs
);
2847 rhs
= build_call_expr (built_in_decls
[BUILT_IN_NEXT_ARG
],
2848 1, integer_zero_node
);
2849 rhs
= fold_convert (TREE_TYPE (lhs
), rhs
);
2850 return build2 (MODIFY_EXPR
, TREE_TYPE (lhs
), lhs
, rhs
);
2852 case BUILT_IN_VA_COPY
:
2853 if (!va_list_simple_ptr
)
2856 if (call_expr_nargs (call
) != 2)
2859 lhs
= CALL_EXPR_ARG (call
, 0);
2860 if (!POINTER_TYPE_P (TREE_TYPE (lhs
))
2861 || TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs
)))
2862 != TYPE_MAIN_VARIANT (va_list_type_node
))
2865 lhs
= build_fold_indirect_ref (lhs
);
2866 rhs
= CALL_EXPR_ARG (call
, 1);
2867 if (TYPE_MAIN_VARIANT (TREE_TYPE (rhs
))
2868 != TYPE_MAIN_VARIANT (va_list_type_node
))
2871 rhs
= fold_convert (TREE_TYPE (lhs
), rhs
);
2872 return build2 (MODIFY_EXPR
, TREE_TYPE (lhs
), lhs
, rhs
);
2874 case BUILT_IN_VA_END
:
2875 return integer_zero_node
;
2882 /* Convert EXPR into a GIMPLE value suitable for substitution on the
2883 RHS of an assignment. Insert the necessary statements before
2885 When IGNORE is set, don't worry about the return value. */
2888 convert_to_gimple_builtin (block_stmt_iterator
*si_p
, tree expr
, bool ignore
)
2890 tree_stmt_iterator ti
;
2891 tree stmt
= bsi_stmt (*si_p
);
2892 tree tmp
, stmts
= NULL
;
2894 push_gimplify_context ();
2897 tmp
= build_empty_stmt ();
2898 gimplify_and_add (expr
, &stmts
);
2901 tmp
= get_initialized_tmp_var (expr
, &stmts
, NULL
);
2902 pop_gimplify_context (NULL
);
2904 if (EXPR_HAS_LOCATION (stmt
))
2905 annotate_all_with_locus (&stmts
, EXPR_LOCATION (stmt
));
2907 /* The replacement can expose previously unreferenced variables. */
2908 for (ti
= tsi_start (stmts
); !tsi_end_p (ti
); tsi_next (&ti
))
2910 tree new_stmt
= tsi_stmt (ti
);
2911 find_new_referenced_vars (tsi_stmt_ptr (ti
));
2912 bsi_insert_before (si_p
, new_stmt
, BSI_NEW_STMT
);
2913 mark_symbols_for_renaming (new_stmt
);
2921 /* A simple pass that attempts to fold all builtin functions. This pass
2922 is run after we've propagated as many constants as we can. */
2925 execute_fold_all_builtins (void)
2927 bool cfg_changed
= false;
2929 unsigned int todoflags
= 0;
2933 block_stmt_iterator i
;
2934 for (i
= bsi_start (bb
); !bsi_end_p (i
); )
2936 tree
*stmtp
= bsi_stmt_ptr (i
);
2937 tree old_stmt
= *stmtp
;
2938 tree call
= get_rhs (*stmtp
);
2939 tree callee
, result
;
2940 enum built_in_function fcode
;
2942 if (!call
|| TREE_CODE (call
) != CALL_EXPR
)
2947 callee
= get_callee_fndecl (call
);
2948 if (!callee
|| DECL_BUILT_IN_CLASS (callee
) != BUILT_IN_NORMAL
)
2953 fcode
= DECL_FUNCTION_CODE (callee
);
2955 result
= ccp_fold_builtin (*stmtp
, call
);
2957 switch (DECL_FUNCTION_CODE (callee
))
2959 case BUILT_IN_CONSTANT_P
:
2960 /* Resolve __builtin_constant_p. If it hasn't been
2961 folded to integer_one_node by now, it's fairly
2962 certain that the value simply isn't constant. */
2963 result
= integer_zero_node
;
2966 case BUILT_IN_STACK_RESTORE
:
2967 result
= optimize_stack_restore (bb
, *stmtp
, i
);
2973 case BUILT_IN_VA_START
:
2974 case BUILT_IN_VA_END
:
2975 case BUILT_IN_VA_COPY
:
2976 /* These shouldn't be folded before pass_stdarg. */
2977 result
= optimize_stdarg_builtin (*stmtp
);
2987 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2989 fprintf (dump_file
, "Simplified\n ");
2990 print_generic_stmt (dump_file
, *stmtp
, dump_flags
);
2993 push_stmt_changes (stmtp
);
2995 if (!set_rhs (stmtp
, result
))
2997 result
= convert_to_gimple_builtin (&i
, result
,
2998 TREE_CODE (old_stmt
)
2999 != GIMPLE_MODIFY_STMT
);
3002 bool ok
= set_rhs (stmtp
, result
);
3004 todoflags
|= TODO_rebuild_alias
;
3008 pop_stmt_changes (stmtp
);
3010 if (maybe_clean_or_replace_eh_stmt (old_stmt
, *stmtp
)
3011 && tree_purge_dead_eh_edges (bb
))
3014 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3016 fprintf (dump_file
, "to\n ");
3017 print_generic_stmt (dump_file
, *stmtp
, dump_flags
);
3018 fprintf (dump_file
, "\n");
3021 /* Retry the same statement if it changed into another
3022 builtin, there might be new opportunities now. */
3023 call
= get_rhs (*stmtp
);
3024 if (!call
|| TREE_CODE (call
) != CALL_EXPR
)
3029 callee
= get_callee_fndecl (call
);
3031 || DECL_BUILT_IN_CLASS (callee
) != BUILT_IN_NORMAL
3032 || DECL_FUNCTION_CODE (callee
) == fcode
)
3037 /* Delete unreachable blocks. */
3039 todoflags
|= TODO_cleanup_cfg
;
3045 struct gimple_opt_pass pass_fold_builtins
=
3051 execute_fold_all_builtins
, /* execute */
3054 0, /* static_pass_number */
3056 PROP_cfg
| PROP_ssa
, /* properties_required */
3057 0, /* properties_provided */
3058 0, /* properties_destroyed */
3059 0, /* todo_flags_start */
3062 | TODO_update_ssa
/* todo_flags_finish */