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 -> This is the default starting value. V_i
32 has not been processed yet.
34 UNDEFINED -> V_i is a local variable whose definition
35 has not been processed yet. Therefore we
36 don't yet know if its value is a constant
39 CONSTANT -> V_i has been found to hold a constant
42 VARYING -> V_i cannot take a constant value, or if it
43 does, it is not possible to determine it
46 The core of SSA-CCP is in ccp_visit_stmt and ccp_visit_phi_node:
48 1- In ccp_visit_stmt, we are interested in assignments whose RHS
49 evaluates into a constant and conditional jumps whose predicate
50 evaluates into a boolean true or false. When an assignment of
51 the form V_i = CONST is found, V_i's lattice value is set to
52 CONSTANT and CONST is associated with it. This causes the
53 propagation engine to add all the SSA edges coming out the
54 assignment into the worklists, so that statements that use V_i
57 If the statement is a conditional with a constant predicate, we
58 mark the outgoing edges as executable or not executable
59 depending on the predicate's value. This is then used when
60 visiting PHI nodes to know when a PHI argument can be ignored.
63 2- In ccp_visit_phi_node, if all the PHI arguments evaluate to the
64 same constant C, then the LHS of the PHI is set to C. This
65 evaluation is known as the "meet operation". Since one of the
66 goals of this evaluation is to optimistically return constant
67 values as often as possible, it uses two main short cuts:
69 - If an argument is flowing in through a non-executable edge, it
70 is ignored. This is useful in cases like this:
76 a_11 = PHI (a_9, a_10)
78 If PRED is known to always evaluate to false, then we can
79 assume that a_11 will always take its value from a_10, meaning
80 that instead of consider it VARYING (a_9 and a_10 have
81 different values), we can consider it CONSTANT 100.
83 - If an argument has an UNDEFINED value, then it does not affect
84 the outcome of the meet operation. If a variable V_i has an
85 UNDEFINED value, it means that either its defining statement
86 hasn't been visited yet or V_i has no defining statement, in
87 which case the original symbol 'V' is being used
88 uninitialized. Since 'V' is a local variable, the compiler
89 may assume any initial value for it.
92 After propagation, every variable V_i that ends up with a lattice
93 value of CONSTANT will have the associated constant value in the
94 array CONST_VAL[i].VALUE. That is fed into substitute_and_fold for
95 final substitution and folding.
98 Constant propagation in stores and loads (STORE-CCP)
99 ----------------------------------------------------
101 While CCP has all the logic to propagate constants in GIMPLE
102 registers, it is missing the ability to associate constants with
103 stores and loads (i.e., pointer dereferences, structures and
104 global/aliased variables). We don't keep loads and stores in
105 SSA, but we do build a factored use-def web for them (in the
108 For instance, consider the following code fragment:
127 We should be able to deduce that the predicate 'a.a != B' is always
128 false. To achieve this, we associate constant values to the SSA
129 names in the V_MAY_DEF and V_MUST_DEF operands for each store.
130 Additionally, since we also glob partial loads/stores with the base
131 symbol, we also keep track of the memory reference where the
132 constant value was stored (in the MEM_REF field of PROP_VALUE_T).
135 # a_5 = V_MAY_DEF <a_4>
141 In the example above, CCP will associate value '2' with 'a_5', but
142 it would be wrong to replace the load from 'a.b' with '2', because
143 '2' had been stored into a.a.
145 To support STORE-CCP, it is necessary to add a new value to the
146 constant propagation lattice. When evaluating a load for a memory
147 reference we can no longer assume a value of UNDEFINED if we
148 haven't seen a preceding store to the same memory location.
149 Consider, for instance global variables:
157 # A_5 = PHI (A_4, A_2);
165 The value of A_2 cannot be assumed to be UNDEFINED, as it may have
166 been defined outside of foo. If we were to assume it UNDEFINED, we
167 would erroneously optimize the above into 'return 3;'. Therefore,
168 when doing STORE-CCP, we introduce a fifth lattice value
169 (UNKNOWN_VAL), which overrides any other value when computing the
170 meet operation in PHI nodes.
172 Though STORE-CCP is not too expensive, it does have to do more work
173 than regular CCP, so it is only enabled at -O2. Both regular CCP
174 and STORE-CCP use the exact same algorithm. The only distinction
175 is that when doing STORE-CCP, the boolean variable DO_STORE_CCP is
176 set to true. This affects the evaluation of statements and PHI
181 Constant propagation with conditional branches,
182 Wegman and Zadeck, ACM TOPLAS 13(2):181-210.
184 Building an Optimizing Compiler,
185 Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9.
187 Advanced Compiler Design and Implementation,
188 Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */
192 #include "coretypes.h"
199 #include "basic-block.h"
202 #include "function.h"
203 #include "diagnostic.h"
205 #include "tree-dump.h"
206 #include "tree-flow.h"
207 #include "tree-pass.h"
208 #include "tree-ssa-propagate.h"
209 #include "langhooks.h"
214 /* Possible lattice values. */
224 /* Array of propagated constant values. After propagation,
225 CONST_VAL[I].VALUE holds the constant value for SSA_NAME(I). If
226 the constant is held in an SSA name representing a memory store
227 (i.e., a V_MAY_DEF or V_MUST_DEF), CONST_VAL[I].MEM_REF will
228 contain the actual memory reference used to store (i.e., the LHS of
229 the assignment doing the store). */
230 static prop_value_t
*const_val
;
232 /* True if we are also propagating constants in stores and loads. */
233 static bool do_store_ccp
;
235 /* Dump constant propagation value VAL to file OUTF prefixed by PREFIX. */
238 dump_lattice_value (FILE *outf
, const char *prefix
, prop_value_t val
)
240 switch (val
.lattice_val
)
243 fprintf (outf
, "%sUNINITIALIZED", prefix
);
246 fprintf (outf
, "%sUNDEFINED", prefix
);
249 fprintf (outf
, "%sVARYING", prefix
);
252 fprintf (outf
, "%sUNKNOWN_VAL", prefix
);
255 fprintf (outf
, "%sCONSTANT ", prefix
);
256 print_generic_expr (outf
, val
.value
, dump_flags
);
264 /* Print lattice value VAL to stderr. */
266 void debug_lattice_value (prop_value_t val
);
269 debug_lattice_value (prop_value_t val
)
271 dump_lattice_value (stderr
, "", val
);
272 fprintf (stderr
, "\n");
276 /* The regular is_gimple_min_invariant does a shallow test of the object.
277 It assumes that full gimplification has happened, or will happen on the
278 object. For a value coming from DECL_INITIAL, this is not true, so we
279 have to be more strict ourselves. */
282 ccp_decl_initial_min_invariant (tree t
)
284 if (!is_gimple_min_invariant (t
))
286 if (TREE_CODE (t
) == ADDR_EXPR
)
288 /* Inline and unroll is_gimple_addressable. */
291 t
= TREE_OPERAND (t
, 0);
292 if (is_gimple_id (t
))
294 if (!handled_component_p (t
))
302 /* Compute a default value for variable VAR and store it in the
303 CONST_VAL array. The following rules are used to get default
306 1- Global and static variables that are declared constant are
309 2- Any other value is considered UNDEFINED. This is useful when
310 considering PHI nodes. PHI arguments that are undefined do not
311 change the constant value of the PHI node, which allows for more
312 constants to be propagated.
314 3- If SSA_NAME_VALUE is set and it is a constant, its value is
317 4- Variables defined by statements other than assignments and PHI
318 nodes are considered VARYING.
320 5- Variables that are not GIMPLE registers are considered
321 UNKNOWN_VAL, which is really a stronger version of UNDEFINED.
322 It's used to avoid the short circuit evaluation implied by
323 UNDEFINED in ccp_lattice_meet. */
326 get_default_value (tree var
)
328 tree sym
= SSA_NAME_VAR (var
);
329 prop_value_t val
= { UNINITIALIZED
, NULL_TREE
, NULL_TREE
};
331 if (!do_store_ccp
&& !is_gimple_reg (var
))
333 /* Short circuit for regular CCP. We are not interested in any
334 non-register when DO_STORE_CCP is false. */
335 val
.lattice_val
= VARYING
;
337 else if (SSA_NAME_VALUE (var
)
338 && is_gimple_min_invariant (SSA_NAME_VALUE (var
)))
340 val
.lattice_val
= CONSTANT
;
341 val
.value
= SSA_NAME_VALUE (var
);
343 else if (TREE_STATIC (sym
)
344 && TREE_READONLY (sym
)
346 && DECL_INITIAL (sym
)
347 && ccp_decl_initial_min_invariant (DECL_INITIAL (sym
)))
349 /* Globals and static variables declared 'const' take their
351 val
.lattice_val
= CONSTANT
;
352 val
.value
= DECL_INITIAL (sym
);
357 tree stmt
= SSA_NAME_DEF_STMT (var
);
359 if (IS_EMPTY_STMT (stmt
))
361 /* Variables defined by an empty statement are those used
362 before being initialized. If VAR is a local variable, we
363 can assume initially that it is UNDEFINED. If we are
364 doing STORE-CCP, function arguments and non-register
365 variables are initially UNKNOWN_VAL, because we cannot
366 discard the value incoming from outside of this function
367 (see ccp_lattice_meet for details). */
368 if (is_gimple_reg (sym
) && TREE_CODE (sym
) != PARM_DECL
)
369 val
.lattice_val
= UNDEFINED
;
370 else if (do_store_ccp
)
371 val
.lattice_val
= UNKNOWN_VAL
;
373 val
.lattice_val
= VARYING
;
375 else if (TREE_CODE (stmt
) == MODIFY_EXPR
376 || TREE_CODE (stmt
) == PHI_NODE
)
378 /* Any other variable defined by an assignment or a PHI node
379 is considered UNDEFINED (or UNKNOWN_VAL if VAR is not a
381 val
.lattice_val
= is_gimple_reg (sym
) ? UNDEFINED
: UNKNOWN_VAL
;
385 /* Otherwise, VAR will never take on a constant value. */
386 val
.lattice_val
= VARYING
;
394 /* Get the constant value associated with variable VAR. If
395 MAY_USE_DEFAULT_P is true, call get_default_value on variables that
396 have the lattice value UNINITIALIZED. */
398 static prop_value_t
*
399 get_value (tree var
, bool may_use_default_p
)
401 prop_value_t
*val
= &const_val
[SSA_NAME_VERSION (var
)];
402 if (may_use_default_p
&& val
->lattice_val
== UNINITIALIZED
)
403 *val
= get_default_value (var
);
409 /* Set the value for variable VAR to NEW_VAL. Return true if the new
410 value is different from VAR's previous value. */
413 set_lattice_value (tree var
, prop_value_t new_val
)
415 prop_value_t
*old_val
= get_value (var
, false);
417 /* Lattice transitions must always be monotonically increasing in
418 value. We allow two exceptions:
420 1- If *OLD_VAL and NEW_VAL are the same, return false to
421 inform the caller that this was a non-transition.
423 2- If we are doing store-ccp (i.e., DOING_STORE_CCP is true),
424 allow CONSTANT->UNKNOWN_VAL. The UNKNOWN_VAL state is a
425 special type of UNDEFINED state which prevents the short
426 circuit evaluation of PHI arguments (see ccp_visit_phi_node
427 and ccp_lattice_meet). */
428 gcc_assert (old_val
->lattice_val
<= new_val
.lattice_val
429 || (old_val
->lattice_val
== new_val
.lattice_val
430 && old_val
->value
== new_val
.value
431 && old_val
->mem_ref
== new_val
.mem_ref
)
433 && old_val
->lattice_val
== CONSTANT
434 && new_val
.lattice_val
== UNKNOWN_VAL
));
436 if (old_val
->lattice_val
!= new_val
.lattice_val
)
438 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
440 dump_lattice_value (dump_file
, "Lattice value changed to ", new_val
);
441 fprintf (dump_file
, ". %sdding SSA edges to worklist.\n",
442 new_val
.lattice_val
!= UNDEFINED
? "A" : "Not a");
447 /* Transitions UNINITIALIZED -> UNDEFINED are never interesting
448 for propagation purposes. In these cases return false to
449 avoid doing useless work. */
450 return (new_val
.lattice_val
!= UNDEFINED
);
457 /* Return the likely CCP lattice value for STMT.
459 If STMT has no operands, then return CONSTANT.
461 Else if any operands of STMT are undefined, then return UNDEFINED.
463 Else if any operands of STMT are constants, then return CONSTANT.
465 Else return VARYING. */
468 likely_value (tree stmt
)
475 ann
= stmt_ann (stmt
);
477 /* If the statement has volatile operands, it won't fold to a
479 if (ann
->has_volatile_ops
)
482 /* If we are not doing store-ccp, statements with loads
483 and/or stores will never fold into a constant. */
485 && !ZERO_SSA_OPERANDS (stmt
, SSA_OP_ALL_VIRTUALS
))
489 /* A CALL_EXPR is assumed to be varying. NOTE: This may be overly
490 conservative, in the presence of const and pure calls. */
491 if (get_call_expr_in (stmt
) != NULL_TREE
)
494 /* Anything other than assignments and conditional jumps are not
495 interesting for CCP. */
496 if (TREE_CODE (stmt
) != MODIFY_EXPR
497 && TREE_CODE (stmt
) != COND_EXPR
498 && TREE_CODE (stmt
) != SWITCH_EXPR
)
501 if (is_gimple_min_invariant (get_rhs (stmt
)))
504 found_constant
= false;
505 FOR_EACH_SSA_TREE_OPERAND (use
, stmt
, iter
, SSA_OP_USE
|SSA_OP_VUSE
)
507 prop_value_t
*val
= get_value (use
, true);
509 if (val
->lattice_val
== VARYING
)
512 if (val
->lattice_val
== UNKNOWN_VAL
)
514 /* UNKNOWN_VAL is invalid when not doing STORE-CCP. */
515 gcc_assert (do_store_ccp
);
519 if (val
->lattice_val
== CONSTANT
)
520 found_constant
= true;
524 || ZERO_SSA_OPERANDS (stmt
, SSA_OP_USE
)
525 || ZERO_SSA_OPERANDS (stmt
, SSA_OP_VUSE
))
532 /* Initialize local data structures for CCP. */
535 ccp_initialize (void)
539 const_val
= XNEWVEC (prop_value_t
, num_ssa_names
);
540 memset (const_val
, 0, num_ssa_names
* sizeof (*const_val
));
542 /* Initialize simulation flags for PHI nodes and statements. */
545 block_stmt_iterator i
;
547 for (i
= bsi_start (bb
); !bsi_end_p (i
); bsi_next (&i
))
549 bool is_varying
= false;
550 tree stmt
= bsi_stmt (i
);
552 if (likely_value (stmt
) == VARYING
)
558 /* If the statement will not produce a constant, mark
559 all its outputs VARYING. */
560 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_ALL_DEFS
)
561 get_value (def
, false)->lattice_val
= VARYING
;
563 /* Never mark conditional jumps with DONT_SIMULATE_AGAIN,
564 otherwise the propagator will never add the outgoing
566 if (TREE_CODE (stmt
) != COND_EXPR
567 && TREE_CODE (stmt
) != SWITCH_EXPR
)
571 DONT_SIMULATE_AGAIN (stmt
) = is_varying
;
575 /* Now process PHI nodes. */
580 for (phi
= phi_nodes (bb
); phi
; phi
= PHI_CHAIN (phi
))
584 prop_value_t
*val
= get_value (PHI_RESULT (phi
), false);
586 for (i
= 0; i
< PHI_NUM_ARGS (phi
); i
++)
588 arg
= PHI_ARG_DEF (phi
, i
);
590 if (TREE_CODE (arg
) == SSA_NAME
591 && get_value (arg
, false)->lattice_val
== VARYING
)
593 val
->lattice_val
= VARYING
;
598 DONT_SIMULATE_AGAIN (phi
) = (val
->lattice_val
== VARYING
);
604 /* Do final substitution of propagated values, cleanup the flowgraph and
605 free allocated storage. */
610 /* Perform substitutions based on the known constant values. */
611 substitute_and_fold (const_val
, false);
617 /* Compute the meet operator between *VAL1 and *VAL2. Store the result
620 any M UNDEFINED = any
621 any M UNKNOWN_VAL = UNKNOWN_VAL
622 any M VARYING = VARYING
623 Ci M Cj = Ci if (i == j)
624 Ci M Cj = VARYING if (i != j)
626 Lattice values UNKNOWN_VAL and UNDEFINED are similar but have
627 different semantics at PHI nodes. Both values imply that we don't
628 know whether the variable is constant or not. However, UNKNOWN_VAL
629 values override all others. For instance, suppose that A is a
639 | A_3 = PHI (A_2, A_1)
644 If the edge into A_2 is not executable, the first visit to A_3 will
645 yield the constant 4. But the second visit to A_3 will be with A_2
646 in state UNKNOWN_VAL. We can no longer conclude that A_3 is 4
647 because A_2 may have been set in another function. If we had used
648 the lattice value UNDEFINED, we would have had wrongly concluded
653 ccp_lattice_meet (prop_value_t
*val1
, prop_value_t
*val2
)
655 if (val1
->lattice_val
== UNDEFINED
)
657 /* UNDEFINED M any = any */
660 else if (val2
->lattice_val
== UNDEFINED
)
662 /* any M UNDEFINED = any
663 Nothing to do. VAL1 already contains the value we want. */
666 else if (val1
->lattice_val
== UNKNOWN_VAL
667 || val2
->lattice_val
== UNKNOWN_VAL
)
669 /* UNKNOWN_VAL values are invalid if we are not doing STORE-CCP. */
670 gcc_assert (do_store_ccp
);
672 /* any M UNKNOWN_VAL = UNKNOWN_VAL. */
673 val1
->lattice_val
= UNKNOWN_VAL
;
674 val1
->value
= NULL_TREE
;
675 val1
->mem_ref
= NULL_TREE
;
677 else if (val1
->lattice_val
== VARYING
678 || val2
->lattice_val
== VARYING
)
680 /* any M VARYING = VARYING. */
681 val1
->lattice_val
= VARYING
;
682 val1
->value
= NULL_TREE
;
683 val1
->mem_ref
= NULL_TREE
;
685 else if (val1
->lattice_val
== CONSTANT
686 && val2
->lattice_val
== CONSTANT
687 && simple_cst_equal (val1
->value
, val2
->value
) == 1
689 || (val1
->mem_ref
&& val2
->mem_ref
690 && operand_equal_p (val1
->mem_ref
, val2
->mem_ref
, 0))))
692 /* Ci M Cj = Ci if (i == j)
693 Ci M Cj = VARYING if (i != j)
695 If these two values come from memory stores, make sure that
696 they come from the same memory reference. */
697 val1
->lattice_val
= CONSTANT
;
698 val1
->value
= val1
->value
;
699 val1
->mem_ref
= val1
->mem_ref
;
703 /* Any other combination is VARYING. */
704 val1
->lattice_val
= VARYING
;
705 val1
->value
= NULL_TREE
;
706 val1
->mem_ref
= NULL_TREE
;
711 /* Loop through the PHI_NODE's parameters for BLOCK and compare their
712 lattice values to determine PHI_NODE's lattice value. The value of a
713 PHI node is determined calling ccp_lattice_meet with all the arguments
714 of the PHI node that are incoming via executable edges. */
716 static enum ssa_prop_result
717 ccp_visit_phi_node (tree phi
)
720 prop_value_t
*old_val
, new_val
;
722 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
724 fprintf (dump_file
, "\nVisiting PHI node: ");
725 print_generic_expr (dump_file
, phi
, dump_flags
);
728 old_val
= get_value (PHI_RESULT (phi
), false);
729 switch (old_val
->lattice_val
)
732 return SSA_PROP_VARYING
;
739 /* To avoid the default value of UNKNOWN_VAL overriding
740 that of its possible constant arguments, temporarily
741 set the PHI node's default lattice value to be
742 UNDEFINED. If the PHI node's old value was UNKNOWN_VAL and
743 the new value is UNDEFINED, then we prevent the invalid
744 transition by not calling set_lattice_value. */
745 gcc_assert (do_store_ccp
);
751 new_val
.lattice_val
= UNDEFINED
;
752 new_val
.value
= NULL_TREE
;
753 new_val
.mem_ref
= NULL_TREE
;
760 for (i
= 0; i
< PHI_NUM_ARGS (phi
); i
++)
762 /* Compute the meet operator over all the PHI arguments flowing
763 through executable edges. */
764 edge e
= PHI_ARG_EDGE (phi
, i
);
766 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
769 "\n Argument #%d (%d -> %d %sexecutable)\n",
770 i
, e
->src
->index
, e
->dest
->index
,
771 (e
->flags
& EDGE_EXECUTABLE
) ? "" : "not ");
774 /* If the incoming edge is executable, Compute the meet operator for
775 the existing value of the PHI node and the current PHI argument. */
776 if (e
->flags
& EDGE_EXECUTABLE
)
778 tree arg
= PHI_ARG_DEF (phi
, i
);
779 prop_value_t arg_val
;
781 if (is_gimple_min_invariant (arg
))
783 arg_val
.lattice_val
= CONSTANT
;
785 arg_val
.mem_ref
= NULL_TREE
;
788 arg_val
= *(get_value (arg
, true));
790 ccp_lattice_meet (&new_val
, &arg_val
);
792 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
794 fprintf (dump_file
, "\t");
795 print_generic_expr (dump_file
, arg
, dump_flags
);
796 dump_lattice_value (dump_file
, "\tValue: ", arg_val
);
797 fprintf (dump_file
, "\n");
800 if (new_val
.lattice_val
== VARYING
)
805 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
807 dump_lattice_value (dump_file
, "\n PHI node value: ", new_val
);
808 fprintf (dump_file
, "\n\n");
811 /* Check for an invalid change from UNKNOWN_VAL to UNDEFINED. */
813 && old_val
->lattice_val
== UNKNOWN_VAL
814 && new_val
.lattice_val
== UNDEFINED
)
815 return SSA_PROP_NOT_INTERESTING
;
817 /* Otherwise, make the transition to the new value. */
818 if (set_lattice_value (PHI_RESULT (phi
), new_val
))
820 if (new_val
.lattice_val
== VARYING
)
821 return SSA_PROP_VARYING
;
823 return SSA_PROP_INTERESTING
;
826 return SSA_PROP_NOT_INTERESTING
;
830 /* CCP specific front-end to the non-destructive constant folding
833 Attempt to simplify the RHS of STMT knowing that one or more
834 operands are constants.
836 If simplification is possible, return the simplified RHS,
837 otherwise return the original RHS. */
842 tree rhs
= get_rhs (stmt
);
843 enum tree_code code
= TREE_CODE (rhs
);
844 enum tree_code_class kind
= TREE_CODE_CLASS (code
);
845 tree retval
= NULL_TREE
;
847 if (TREE_CODE (rhs
) == SSA_NAME
)
849 /* If the RHS is an SSA_NAME, return its known constant value,
851 return get_value (rhs
, true)->value
;
853 else if (do_store_ccp
&& stmt_makes_single_load (stmt
))
855 /* If the RHS is a memory load, see if the VUSEs associated with
856 it are a valid constant for that memory load. */
857 prop_value_t
*val
= get_value_loaded_by (stmt
, const_val
);
858 if (val
&& val
->mem_ref
)
860 if (operand_equal_p (val
->mem_ref
, rhs
, 0))
863 /* If RHS is extracting REALPART_EXPR or IMAGPART_EXPR of a
864 complex type with a known constant value, return it. */
865 if ((TREE_CODE (rhs
) == REALPART_EXPR
866 || TREE_CODE (rhs
) == IMAGPART_EXPR
)
867 && operand_equal_p (val
->mem_ref
, TREE_OPERAND (rhs
, 0), 0))
868 return fold_build1 (TREE_CODE (rhs
), TREE_TYPE (rhs
), val
->value
);
873 /* Unary operators. Note that we know the single operand must
874 be a constant. So this should almost always return a
876 if (kind
== tcc_unary
)
878 /* Handle unary operators which can appear in GIMPLE form. */
879 tree op0
= TREE_OPERAND (rhs
, 0);
881 /* Simplify the operand down to a constant. */
882 if (TREE_CODE (op0
) == SSA_NAME
)
884 prop_value_t
*val
= get_value (op0
, true);
885 if (val
->lattice_val
== CONSTANT
)
886 op0
= get_value (op0
, true)->value
;
889 if ((code
== NOP_EXPR
|| code
== CONVERT_EXPR
)
890 && tree_ssa_useless_type_conversion_1 (TREE_TYPE (rhs
),
893 return fold_unary (code
, TREE_TYPE (rhs
), op0
);
896 /* Binary and comparison operators. We know one or both of the
897 operands are constants. */
898 else if (kind
== tcc_binary
899 || kind
== tcc_comparison
900 || code
== TRUTH_AND_EXPR
901 || code
== TRUTH_OR_EXPR
902 || code
== TRUTH_XOR_EXPR
)
904 /* Handle binary and comparison operators that can appear in
906 tree op0
= TREE_OPERAND (rhs
, 0);
907 tree op1
= TREE_OPERAND (rhs
, 1);
909 /* Simplify the operands down to constants when appropriate. */
910 if (TREE_CODE (op0
) == SSA_NAME
)
912 prop_value_t
*val
= get_value (op0
, true);
913 if (val
->lattice_val
== CONSTANT
)
917 if (TREE_CODE (op1
) == SSA_NAME
)
919 prop_value_t
*val
= get_value (op1
, true);
920 if (val
->lattice_val
== CONSTANT
)
924 return fold_binary (code
, TREE_TYPE (rhs
), op0
, op1
);
927 /* We may be able to fold away calls to builtin functions if their
928 arguments are constants. */
929 else if (code
== CALL_EXPR
930 && TREE_CODE (TREE_OPERAND (rhs
, 0)) == ADDR_EXPR
931 && (TREE_CODE (TREE_OPERAND (TREE_OPERAND (rhs
, 0), 0))
933 && DECL_BUILT_IN (TREE_OPERAND (TREE_OPERAND (rhs
, 0), 0)))
935 if (!ZERO_SSA_OPERANDS (stmt
, SSA_OP_USE
))
938 tree fndecl
, arglist
;
943 /* Preserve the original values of every operand. */
944 orig
= XNEWVEC (tree
, NUM_SSA_OPERANDS (stmt
, SSA_OP_USE
));
945 FOR_EACH_SSA_TREE_OPERAND (var
, stmt
, iter
, SSA_OP_USE
)
948 /* Substitute operands with their values and try to fold. */
949 replace_uses_in (stmt
, NULL
, const_val
);
950 fndecl
= get_callee_fndecl (rhs
);
951 arglist
= TREE_OPERAND (rhs
, 1);
952 retval
= fold_builtin (fndecl
, arglist
, false);
954 /* Restore operands to their original form. */
956 FOR_EACH_SSA_USE_OPERAND (var_p
, stmt
, iter
, SSA_OP_USE
)
957 SET_USE (var_p
, orig
[i
++]);
964 /* If we got a simplified form, see if we need to convert its type. */
966 return fold_convert (TREE_TYPE (rhs
), retval
);
968 /* No simplification was possible. */
973 /* Return the tree representing the element referenced by T if T is an
974 ARRAY_REF or COMPONENT_REF into constant aggregates. Return
975 NULL_TREE otherwise. */
978 fold_const_aggregate_ref (tree t
)
981 tree base
, ctor
, idx
, field
;
982 unsigned HOST_WIDE_INT cnt
;
985 switch (TREE_CODE (t
))
988 /* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its
989 DECL_INITIAL. If BASE is a nested reference into another
990 ARRAY_REF or COMPONENT_REF, make a recursive call to resolve
991 the inner reference. */
992 base
= TREE_OPERAND (t
, 0);
993 switch (TREE_CODE (base
))
996 if (!TREE_READONLY (base
)
997 || TREE_CODE (TREE_TYPE (base
)) != ARRAY_TYPE
998 || !targetm
.binds_local_p (base
))
1001 ctor
= DECL_INITIAL (base
);
1006 ctor
= fold_const_aggregate_ref (base
);
1013 if (ctor
== NULL_TREE
1014 || (TREE_CODE (ctor
) != CONSTRUCTOR
1015 && TREE_CODE (ctor
) != STRING_CST
)
1016 || !TREE_STATIC (ctor
))
1019 /* Get the index. If we have an SSA_NAME, try to resolve it
1020 with the current lattice value for the SSA_NAME. */
1021 idx
= TREE_OPERAND (t
, 1);
1022 switch (TREE_CODE (idx
))
1025 if ((value
= get_value (idx
, true))
1026 && value
->lattice_val
== CONSTANT
1027 && TREE_CODE (value
->value
) == INTEGER_CST
)
1040 /* Fold read from constant string. */
1041 if (TREE_CODE (ctor
) == STRING_CST
)
1043 if ((TYPE_MODE (TREE_TYPE (t
))
1044 == TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor
))))
1045 && (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor
))))
1047 && GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor
)))) == 1
1048 && compare_tree_int (idx
, TREE_STRING_LENGTH (ctor
)) < 0)
1049 return build_int_cst (TREE_TYPE (t
), (TREE_STRING_POINTER (ctor
)
1050 [TREE_INT_CST_LOW (idx
)]));
1054 /* Whoo-hoo! I'll fold ya baby. Yeah! */
1055 FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor
), cnt
, cfield
, cval
)
1056 if (tree_int_cst_equal (cfield
, idx
))
1061 /* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its
1062 DECL_INITIAL. If BASE is a nested reference into another
1063 ARRAY_REF or COMPONENT_REF, make a recursive call to resolve
1064 the inner reference. */
1065 base
= TREE_OPERAND (t
, 0);
1066 switch (TREE_CODE (base
))
1069 if (!TREE_READONLY (base
)
1070 || TREE_CODE (TREE_TYPE (base
)) != RECORD_TYPE
1071 || !targetm
.binds_local_p (base
))
1074 ctor
= DECL_INITIAL (base
);
1079 ctor
= fold_const_aggregate_ref (base
);
1086 if (ctor
== NULL_TREE
1087 || TREE_CODE (ctor
) != CONSTRUCTOR
1088 || !TREE_STATIC (ctor
))
1091 field
= TREE_OPERAND (t
, 1);
1093 FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor
), cnt
, cfield
, cval
)
1095 /* FIXME: Handle bit-fields. */
1096 && ! DECL_BIT_FIELD (cfield
))
1103 tree c
= fold_const_aggregate_ref (TREE_OPERAND (t
, 0));
1104 if (c
&& TREE_CODE (c
) == COMPLEX_CST
)
1105 return fold_build1 (TREE_CODE (t
), TREE_TYPE (t
), c
);
1116 /* Evaluate statement STMT. */
1119 evaluate_stmt (tree stmt
)
1122 tree simplified
= NULL_TREE
;
1123 ccp_lattice_t likelyvalue
= likely_value (stmt
);
1126 val
.mem_ref
= NULL_TREE
;
1128 fold_defer_overflow_warnings ();
1130 /* If the statement is likely to have a CONSTANT result, then try
1131 to fold the statement to determine the constant value. */
1132 if (likelyvalue
== CONSTANT
)
1133 simplified
= ccp_fold (stmt
);
1134 /* If the statement is likely to have a VARYING result, then do not
1135 bother folding the statement. */
1136 if (likelyvalue
== VARYING
)
1137 simplified
= get_rhs (stmt
);
1138 /* If the statement is an ARRAY_REF or COMPONENT_REF into constant
1139 aggregates, extract the referenced constant. Otherwise the
1140 statement is likely to have an UNDEFINED value, and there will be
1141 nothing to do. Note that fold_const_aggregate_ref returns
1142 NULL_TREE if the first case does not match. */
1143 else if (!simplified
)
1144 simplified
= fold_const_aggregate_ref (get_rhs (stmt
));
1146 is_constant
= simplified
&& is_gimple_min_invariant (simplified
);
1148 fold_undefer_overflow_warnings (is_constant
, stmt
, 0);
1152 /* The statement produced a constant value. */
1153 val
.lattice_val
= CONSTANT
;
1154 val
.value
= simplified
;
1158 /* The statement produced a nonconstant value. If the statement
1159 had UNDEFINED operands, then the result of the statement
1160 should be UNDEFINED. Otherwise, the statement is VARYING. */
1161 if (likelyvalue
== UNDEFINED
|| likelyvalue
== UNKNOWN_VAL
)
1162 val
.lattice_val
= likelyvalue
;
1164 val
.lattice_val
= VARYING
;
1166 val
.value
= NULL_TREE
;
1173 /* Visit the assignment statement STMT. Set the value of its LHS to the
1174 value computed by the RHS and store LHS in *OUTPUT_P. If STMT
1175 creates virtual definitions, set the value of each new name to that
1176 of the RHS (if we can derive a constant out of the RHS). */
1178 static enum ssa_prop_result
1179 visit_assignment (tree stmt
, tree
*output_p
)
1183 enum ssa_prop_result retval
;
1185 lhs
= TREE_OPERAND (stmt
, 0);
1186 rhs
= TREE_OPERAND (stmt
, 1);
1188 if (TREE_CODE (rhs
) == SSA_NAME
)
1190 /* For a simple copy operation, we copy the lattice values. */
1191 prop_value_t
*nval
= get_value (rhs
, true);
1194 else if (do_store_ccp
&& stmt_makes_single_load (stmt
))
1196 /* Same as above, but the RHS is not a gimple register and yet
1197 has a known VUSE. If STMT is loading from the same memory
1198 location that created the SSA_NAMEs for the virtual operands,
1199 we can propagate the value on the RHS. */
1200 prop_value_t
*nval
= get_value_loaded_by (stmt
, const_val
);
1202 if (nval
&& nval
->mem_ref
1203 && operand_equal_p (nval
->mem_ref
, rhs
, 0))
1206 val
= evaluate_stmt (stmt
);
1209 /* Evaluate the statement. */
1210 val
= evaluate_stmt (stmt
);
1212 /* If the original LHS was a VIEW_CONVERT_EXPR, modify the constant
1213 value to be a VIEW_CONVERT_EXPR of the old constant value.
1215 ??? Also, if this was a definition of a bitfield, we need to widen
1216 the constant value into the type of the destination variable. This
1217 should not be necessary if GCC represented bitfields properly. */
1219 tree orig_lhs
= TREE_OPERAND (stmt
, 0);
1221 if (TREE_CODE (orig_lhs
) == VIEW_CONVERT_EXPR
1222 && val
.lattice_val
== CONSTANT
)
1224 tree w
= fold_unary (VIEW_CONVERT_EXPR
,
1225 TREE_TYPE (TREE_OPERAND (orig_lhs
, 0)),
1228 orig_lhs
= TREE_OPERAND (orig_lhs
, 0);
1229 if (w
&& is_gimple_min_invariant (w
))
1233 val
.lattice_val
= VARYING
;
1238 if (val
.lattice_val
== CONSTANT
1239 && TREE_CODE (orig_lhs
) == COMPONENT_REF
1240 && DECL_BIT_FIELD (TREE_OPERAND (orig_lhs
, 1)))
1242 tree w
= widen_bitfield (val
.value
, TREE_OPERAND (orig_lhs
, 1),
1245 if (w
&& is_gimple_min_invariant (w
))
1249 val
.lattice_val
= VARYING
;
1250 val
.value
= NULL_TREE
;
1251 val
.mem_ref
= NULL_TREE
;
1256 retval
= SSA_PROP_NOT_INTERESTING
;
1258 /* Set the lattice value of the statement's output. */
1259 if (TREE_CODE (lhs
) == SSA_NAME
)
1261 /* If STMT is an assignment to an SSA_NAME, we only have one
1263 if (set_lattice_value (lhs
, val
))
1266 if (val
.lattice_val
== VARYING
)
1267 retval
= SSA_PROP_VARYING
;
1269 retval
= SSA_PROP_INTERESTING
;
1272 else if (do_store_ccp
&& stmt_makes_single_store (stmt
))
1274 /* Otherwise, set the names in V_MAY_DEF/V_MUST_DEF operands
1275 to the new constant value and mark the LHS as the memory
1276 reference associated with VAL. */
1281 /* Stores cannot take on an UNDEFINED value. */
1282 if (val
.lattice_val
== UNDEFINED
)
1283 val
.lattice_val
= UNKNOWN_VAL
;
1285 /* Mark VAL as stored in the LHS of this assignment. */
1288 /* Set the value of every VDEF to VAL. */
1290 FOR_EACH_SSA_TREE_OPERAND (vdef
, stmt
, i
, SSA_OP_VIRTUAL_DEFS
)
1291 changed
|= set_lattice_value (vdef
, val
);
1293 /* Note that for propagation purposes, we are only interested in
1294 visiting statements that load the exact same memory reference
1295 stored here. Those statements will have the exact same list
1296 of virtual uses, so it is enough to set the output of this
1297 statement to be its first virtual definition. */
1298 *output_p
= first_vdef (stmt
);
1301 if (val
.lattice_val
== VARYING
)
1302 retval
= SSA_PROP_VARYING
;
1304 retval
= SSA_PROP_INTERESTING
;
1312 /* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING
1313 if it can determine which edge will be taken. Otherwise, return
1314 SSA_PROP_VARYING. */
1316 static enum ssa_prop_result
1317 visit_cond_stmt (tree stmt
, edge
*taken_edge_p
)
1322 block
= bb_for_stmt (stmt
);
1323 val
= evaluate_stmt (stmt
);
1325 /* Find which edge out of the conditional block will be taken and add it
1326 to the worklist. If no single edge can be determined statically,
1327 return SSA_PROP_VARYING to feed all the outgoing edges to the
1328 propagation engine. */
1329 *taken_edge_p
= val
.value
? find_taken_edge (block
, val
.value
) : 0;
1331 return SSA_PROP_INTERESTING
;
1333 return SSA_PROP_VARYING
;
1337 /* Evaluate statement STMT. If the statement produces an output value and
1338 its evaluation changes the lattice value of its output, return
1339 SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the
1342 If STMT is a conditional branch and we can determine its truth
1343 value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying
1344 value, return SSA_PROP_VARYING. */
1346 static enum ssa_prop_result
1347 ccp_visit_stmt (tree stmt
, edge
*taken_edge_p
, tree
*output_p
)
1352 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1354 fprintf (dump_file
, "\nVisiting statement:\n");
1355 print_generic_stmt (dump_file
, stmt
, dump_flags
);
1356 fprintf (dump_file
, "\n");
1359 if (TREE_CODE (stmt
) == MODIFY_EXPR
)
1361 /* If the statement is an assignment that produces a single
1362 output value, evaluate its RHS to see if the lattice value of
1363 its output has changed. */
1364 return visit_assignment (stmt
, output_p
);
1366 else if (TREE_CODE (stmt
) == COND_EXPR
|| TREE_CODE (stmt
) == SWITCH_EXPR
)
1368 /* If STMT is a conditional branch, see if we can determine
1369 which branch will be taken. */
1370 return visit_cond_stmt (stmt
, taken_edge_p
);
1373 /* Any other kind of statement is not interesting for constant
1374 propagation and, therefore, not worth simulating. */
1375 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1376 fprintf (dump_file
, "No interesting values produced. Marked VARYING.\n");
1378 /* Definitions made by statements other than assignments to
1379 SSA_NAMEs represent unknown modifications to their outputs.
1380 Mark them VARYING. */
1381 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_ALL_DEFS
)
1383 prop_value_t v
= { VARYING
, NULL_TREE
, NULL_TREE
};
1384 set_lattice_value (def
, v
);
1387 return SSA_PROP_VARYING
;
1391 /* Main entry point for SSA Conditional Constant Propagation. */
1394 execute_ssa_ccp (bool store_ccp
)
1396 do_store_ccp
= store_ccp
;
1398 ssa_propagate (ccp_visit_stmt
, ccp_visit_phi_node
);
1406 execute_ssa_ccp (false);
1414 return flag_tree_ccp
!= 0;
1418 struct tree_opt_pass pass_ccp
=
1421 gate_ccp
, /* gate */
1422 do_ssa_ccp
, /* execute */
1425 0, /* static_pass_number */
1426 TV_TREE_CCP
, /* tv_id */
1427 PROP_cfg
| PROP_ssa
| PROP_alias
, /* properties_required */
1428 0, /* properties_provided */
1429 PROP_smt_usage
, /* properties_destroyed */
1430 0, /* todo_flags_start */
1431 TODO_cleanup_cfg
| TODO_dump_func
| TODO_update_ssa
1432 | TODO_ggc_collect
| TODO_verify_ssa
1433 | TODO_verify_stmts
| TODO_update_smt_usage
, /* todo_flags_finish */
1439 do_ssa_store_ccp (void)
1441 /* If STORE-CCP is not enabled, we just run regular CCP. */
1442 execute_ssa_ccp (flag_tree_store_ccp
!= 0);
1447 gate_store_ccp (void)
1449 /* STORE-CCP is enabled only with -ftree-store-ccp, but when
1450 -fno-tree-store-ccp is specified, we should run regular CCP.
1451 That's why the pass is enabled with either flag. */
1452 return flag_tree_store_ccp
!= 0 || flag_tree_ccp
!= 0;
1456 struct tree_opt_pass pass_store_ccp
=
1458 "store_ccp", /* name */
1459 gate_store_ccp
, /* gate */
1460 do_ssa_store_ccp
, /* execute */
1463 0, /* static_pass_number */
1464 TV_TREE_STORE_CCP
, /* tv_id */
1465 PROP_cfg
| PROP_ssa
| PROP_alias
, /* properties_required */
1466 0, /* properties_provided */
1467 PROP_smt_usage
, /* properties_destroyed */
1468 0, /* todo_flags_start */
1469 TODO_dump_func
| TODO_update_ssa
1470 | TODO_ggc_collect
| TODO_verify_ssa
1472 | TODO_verify_stmts
| TODO_update_smt_usage
, /* todo_flags_finish */
1476 /* Given a constant value VAL for bitfield FIELD, and a destination
1477 variable VAR, return VAL appropriately widened to fit into VAR. If
1478 FIELD is wider than HOST_WIDE_INT, NULL is returned. */
1481 widen_bitfield (tree val
, tree field
, tree var
)
1483 unsigned HOST_WIDE_INT var_size
, field_size
;
1485 unsigned HOST_WIDE_INT mask
;
1488 /* We can only do this if the size of the type and field and VAL are
1489 all constants representable in HOST_WIDE_INT. */
1490 if (!host_integerp (TYPE_SIZE (TREE_TYPE (var
)), 1)
1491 || !host_integerp (DECL_SIZE (field
), 1)
1492 || !host_integerp (val
, 0))
1495 var_size
= tree_low_cst (TYPE_SIZE (TREE_TYPE (var
)), 1);
1496 field_size
= tree_low_cst (DECL_SIZE (field
), 1);
1498 /* Give up if either the bitfield or the variable are too wide. */
1499 if (field_size
> HOST_BITS_PER_WIDE_INT
|| var_size
> HOST_BITS_PER_WIDE_INT
)
1502 gcc_assert (var_size
>= field_size
);
1504 /* If the sign bit of the value is not set or the field's type is unsigned,
1505 just mask off the high order bits of the value. */
1506 if (DECL_UNSIGNED (field
)
1507 || !(tree_low_cst (val
, 0) & (((HOST_WIDE_INT
)1) << (field_size
- 1))))
1509 /* Zero extension. Build a mask with the lower 'field_size' bits
1510 set and a BIT_AND_EXPR node to clear the high order bits of
1512 for (i
= 0, mask
= 0; i
< field_size
; i
++)
1513 mask
|= ((HOST_WIDE_INT
) 1) << i
;
1515 wide_val
= fold_build2 (BIT_AND_EXPR
, TREE_TYPE (var
), val
,
1516 build_int_cst (TREE_TYPE (var
), mask
));
1520 /* Sign extension. Create a mask with the upper 'field_size'
1521 bits set and a BIT_IOR_EXPR to set the high order bits of the
1523 for (i
= 0, mask
= 0; i
< (var_size
- field_size
); i
++)
1524 mask
|= ((HOST_WIDE_INT
) 1) << (var_size
- i
- 1);
1526 wide_val
= fold_build2 (BIT_IOR_EXPR
, TREE_TYPE (var
), val
,
1527 build_int_cst (TREE_TYPE (var
), mask
));
1534 /* A subroutine of fold_stmt_r. Attempts to fold *(A+O) to A[X].
1535 BASE is an array type. OFFSET is a byte displacement. ORIG_TYPE
1536 is the desired result type. */
1539 maybe_fold_offset_to_array_ref (tree base
, tree offset
, tree orig_type
)
1541 tree min_idx
, idx
, elt_offset
= integer_zero_node
;
1542 tree array_type
, elt_type
, elt_size
;
1544 /* If BASE is an ARRAY_REF, we can pick up another offset (this time
1545 measured in units of the size of elements type) from that ARRAY_REF).
1546 We can't do anything if either is variable.
1548 The case we handle here is *(&A[N]+O). */
1549 if (TREE_CODE (base
) == ARRAY_REF
)
1551 tree low_bound
= array_ref_low_bound (base
);
1553 elt_offset
= TREE_OPERAND (base
, 1);
1554 if (TREE_CODE (low_bound
) != INTEGER_CST
1555 || TREE_CODE (elt_offset
) != INTEGER_CST
)
1558 elt_offset
= int_const_binop (MINUS_EXPR
, elt_offset
, low_bound
, 0);
1559 base
= TREE_OPERAND (base
, 0);
1562 /* Ignore stupid user tricks of indexing non-array variables. */
1563 array_type
= TREE_TYPE (base
);
1564 if (TREE_CODE (array_type
) != ARRAY_TYPE
)
1566 elt_type
= TREE_TYPE (array_type
);
1567 if (!lang_hooks
.types_compatible_p (orig_type
, elt_type
))
1570 /* If OFFSET and ELT_OFFSET are zero, we don't care about the size of the
1571 element type (so we can use the alignment if it's not constant).
1572 Otherwise, compute the offset as an index by using a division. If the
1573 division isn't exact, then don't do anything. */
1574 elt_size
= TYPE_SIZE_UNIT (elt_type
);
1575 if (integer_zerop (offset
))
1577 if (TREE_CODE (elt_size
) != INTEGER_CST
)
1578 elt_size
= size_int (TYPE_ALIGN (elt_type
));
1580 idx
= integer_zero_node
;
1584 unsigned HOST_WIDE_INT lquo
, lrem
;
1585 HOST_WIDE_INT hquo
, hrem
;
1587 if (TREE_CODE (elt_size
) != INTEGER_CST
1588 || div_and_round_double (TRUNC_DIV_EXPR
, 1,
1589 TREE_INT_CST_LOW (offset
),
1590 TREE_INT_CST_HIGH (offset
),
1591 TREE_INT_CST_LOW (elt_size
),
1592 TREE_INT_CST_HIGH (elt_size
),
1593 &lquo
, &hquo
, &lrem
, &hrem
)
1597 idx
= build_int_cst_wide (NULL_TREE
, lquo
, hquo
);
1600 /* Assume the low bound is zero. If there is a domain type, get the
1601 low bound, if any, convert the index into that type, and add the
1603 min_idx
= integer_zero_node
;
1604 if (TYPE_DOMAIN (array_type
))
1606 if (TYPE_MIN_VALUE (TYPE_DOMAIN (array_type
)))
1607 min_idx
= TYPE_MIN_VALUE (TYPE_DOMAIN (array_type
));
1609 min_idx
= fold_convert (TYPE_DOMAIN (array_type
), min_idx
);
1611 if (TREE_CODE (min_idx
) != INTEGER_CST
)
1614 idx
= fold_convert (TYPE_DOMAIN (array_type
), idx
);
1615 elt_offset
= fold_convert (TYPE_DOMAIN (array_type
), elt_offset
);
1618 if (!integer_zerop (min_idx
))
1619 idx
= int_const_binop (PLUS_EXPR
, idx
, min_idx
, 0);
1620 if (!integer_zerop (elt_offset
))
1621 idx
= int_const_binop (PLUS_EXPR
, idx
, elt_offset
, 0);
1623 return build4 (ARRAY_REF
, orig_type
, base
, idx
, NULL_TREE
, NULL_TREE
);
1627 /* A subroutine of fold_stmt_r. Attempts to fold *(S+O) to S.X.
1628 BASE is a record type. OFFSET is a byte displacement. ORIG_TYPE
1629 is the desired result type. */
1630 /* ??? This doesn't handle class inheritance. */
1633 maybe_fold_offset_to_component_ref (tree record_type
, tree base
, tree offset
,
1634 tree orig_type
, bool base_is_ptr
)
1636 tree f
, t
, field_type
, tail_array_field
, field_offset
;
1638 if (TREE_CODE (record_type
) != RECORD_TYPE
1639 && TREE_CODE (record_type
) != UNION_TYPE
1640 && TREE_CODE (record_type
) != QUAL_UNION_TYPE
)
1643 /* Short-circuit silly cases. */
1644 if (lang_hooks
.types_compatible_p (record_type
, orig_type
))
1647 tail_array_field
= NULL_TREE
;
1648 for (f
= TYPE_FIELDS (record_type
); f
; f
= TREE_CHAIN (f
))
1652 if (TREE_CODE (f
) != FIELD_DECL
)
1654 if (DECL_BIT_FIELD (f
))
1657 field_offset
= byte_position (f
);
1658 if (TREE_CODE (field_offset
) != INTEGER_CST
)
1661 /* ??? Java creates "interesting" fields for representing base classes.
1662 They have no name, and have no context. With no context, we get into
1663 trouble with nonoverlapping_component_refs_p. Skip them. */
1664 if (!DECL_FIELD_CONTEXT (f
))
1667 /* The previous array field isn't at the end. */
1668 tail_array_field
= NULL_TREE
;
1670 /* Check to see if this offset overlaps with the field. */
1671 cmp
= tree_int_cst_compare (field_offset
, offset
);
1675 field_type
= TREE_TYPE (f
);
1677 /* Here we exactly match the offset being checked. If the types match,
1678 then we can return that field. */
1680 && lang_hooks
.types_compatible_p (orig_type
, field_type
))
1683 base
= build1 (INDIRECT_REF
, record_type
, base
);
1684 t
= build3 (COMPONENT_REF
, field_type
, base
, f
, NULL_TREE
);
1688 /* Don't care about offsets into the middle of scalars. */
1689 if (!AGGREGATE_TYPE_P (field_type
))
1692 /* Check for array at the end of the struct. This is often
1693 used as for flexible array members. We should be able to
1694 turn this into an array access anyway. */
1695 if (TREE_CODE (field_type
) == ARRAY_TYPE
)
1696 tail_array_field
= f
;
1698 /* Check the end of the field against the offset. */
1699 if (!DECL_SIZE_UNIT (f
)
1700 || TREE_CODE (DECL_SIZE_UNIT (f
)) != INTEGER_CST
)
1702 t
= int_const_binop (MINUS_EXPR
, offset
, field_offset
, 1);
1703 if (!tree_int_cst_lt (t
, DECL_SIZE_UNIT (f
)))
1706 /* If we matched, then set offset to the displacement into
1712 if (!tail_array_field
)
1715 f
= tail_array_field
;
1716 field_type
= TREE_TYPE (f
);
1717 offset
= int_const_binop (MINUS_EXPR
, offset
, byte_position (f
), 1);
1720 /* If we get here, we've got an aggregate field, and a possibly
1721 nonzero offset into them. Recurse and hope for a valid match. */
1723 base
= build1 (INDIRECT_REF
, record_type
, base
);
1724 base
= build3 (COMPONENT_REF
, field_type
, base
, f
, NULL_TREE
);
1726 t
= maybe_fold_offset_to_array_ref (base
, offset
, orig_type
);
1729 return maybe_fold_offset_to_component_ref (field_type
, base
, offset
,
1734 /* A subroutine of fold_stmt_r. Attempt to simplify *(BASE+OFFSET).
1735 Return the simplified expression, or NULL if nothing could be done. */
1738 maybe_fold_stmt_indirect (tree expr
, tree base
, tree offset
)
1742 /* We may well have constructed a double-nested PLUS_EXPR via multiple
1743 substitutions. Fold that down to one. Remove NON_LVALUE_EXPRs that
1744 are sometimes added. */
1746 STRIP_TYPE_NOPS (base
);
1747 TREE_OPERAND (expr
, 0) = base
;
1749 /* One possibility is that the address reduces to a string constant. */
1750 t
= fold_read_from_constant_string (expr
);
1754 /* Add in any offset from a PLUS_EXPR. */
1755 if (TREE_CODE (base
) == PLUS_EXPR
)
1759 offset2
= TREE_OPERAND (base
, 1);
1760 if (TREE_CODE (offset2
) != INTEGER_CST
)
1762 base
= TREE_OPERAND (base
, 0);
1764 offset
= int_const_binop (PLUS_EXPR
, offset
, offset2
, 1);
1767 if (TREE_CODE (base
) == ADDR_EXPR
)
1769 /* Strip the ADDR_EXPR. */
1770 base
= TREE_OPERAND (base
, 0);
1772 /* Fold away CONST_DECL to its value, if the type is scalar. */
1773 if (TREE_CODE (base
) == CONST_DECL
1774 && ccp_decl_initial_min_invariant (DECL_INITIAL (base
)))
1775 return DECL_INITIAL (base
);
1777 /* Try folding *(&B+O) to B[X]. */
1778 t
= maybe_fold_offset_to_array_ref (base
, offset
, TREE_TYPE (expr
));
1782 /* Try folding *(&B+O) to B.X. */
1783 t
= maybe_fold_offset_to_component_ref (TREE_TYPE (base
), base
, offset
,
1784 TREE_TYPE (expr
), false);
1788 /* Fold *&B to B. We can only do this if EXPR is the same type
1789 as BASE. We can't do this if EXPR is the element type of an array
1790 and BASE is the array. */
1791 if (integer_zerop (offset
)
1792 && lang_hooks
.types_compatible_p (TREE_TYPE (base
),
1798 /* We can get here for out-of-range string constant accesses,
1799 such as "_"[3]. Bail out of the entire substitution search
1800 and arrange for the entire statement to be replaced by a
1801 call to __builtin_trap. In all likelihood this will all be
1802 constant-folded away, but in the meantime we can't leave with
1803 something that get_expr_operands can't understand. */
1807 if (TREE_CODE (t
) == ADDR_EXPR
1808 && TREE_CODE (TREE_OPERAND (t
, 0)) == STRING_CST
)
1810 /* FIXME: Except that this causes problems elsewhere with dead
1811 code not being deleted, and we die in the rtl expanders
1812 because we failed to remove some ssa_name. In the meantime,
1813 just return zero. */
1814 /* FIXME2: This condition should be signaled by
1815 fold_read_from_constant_string directly, rather than
1816 re-checking for it here. */
1817 return integer_zero_node
;
1820 /* Try folding *(B+O) to B->X. Still an improvement. */
1821 if (POINTER_TYPE_P (TREE_TYPE (base
)))
1823 t
= maybe_fold_offset_to_component_ref (TREE_TYPE (TREE_TYPE (base
)),
1825 TREE_TYPE (expr
), true);
1831 /* Otherwise we had an offset that we could not simplify. */
1836 /* A subroutine of fold_stmt_r. EXPR is a PLUS_EXPR.
1838 A quaint feature extant in our address arithmetic is that there
1839 can be hidden type changes here. The type of the result need
1840 not be the same as the type of the input pointer.
1842 What we're after here is an expression of the form
1843 (T *)(&array + const)
1844 where the cast doesn't actually exist, but is implicit in the
1845 type of the PLUS_EXPR. We'd like to turn this into
1847 which may be able to propagate further. */
1850 maybe_fold_stmt_addition (tree expr
)
1852 tree op0
= TREE_OPERAND (expr
, 0);
1853 tree op1
= TREE_OPERAND (expr
, 1);
1854 tree ptr_type
= TREE_TYPE (expr
);
1857 bool subtract
= (TREE_CODE (expr
) == MINUS_EXPR
);
1859 /* We're only interested in pointer arithmetic. */
1860 if (!POINTER_TYPE_P (ptr_type
))
1862 /* Canonicalize the integral operand to op1. */
1863 if (INTEGRAL_TYPE_P (TREE_TYPE (op0
)))
1867 t
= op0
, op0
= op1
, op1
= t
;
1869 /* It had better be a constant. */
1870 if (TREE_CODE (op1
) != INTEGER_CST
)
1872 /* The first operand should be an ADDR_EXPR. */
1873 if (TREE_CODE (op0
) != ADDR_EXPR
)
1875 op0
= TREE_OPERAND (op0
, 0);
1877 /* If the first operand is an ARRAY_REF, expand it so that we can fold
1878 the offset into it. */
1879 while (TREE_CODE (op0
) == ARRAY_REF
)
1881 tree array_obj
= TREE_OPERAND (op0
, 0);
1882 tree array_idx
= TREE_OPERAND (op0
, 1);
1883 tree elt_type
= TREE_TYPE (op0
);
1884 tree elt_size
= TYPE_SIZE_UNIT (elt_type
);
1887 if (TREE_CODE (array_idx
) != INTEGER_CST
)
1889 if (TREE_CODE (elt_size
) != INTEGER_CST
)
1892 /* Un-bias the index by the min index of the array type. */
1893 min_idx
= TYPE_DOMAIN (TREE_TYPE (array_obj
));
1896 min_idx
= TYPE_MIN_VALUE (min_idx
);
1899 if (TREE_CODE (min_idx
) != INTEGER_CST
)
1902 array_idx
= fold_convert (TREE_TYPE (min_idx
), array_idx
);
1903 if (!integer_zerop (min_idx
))
1904 array_idx
= int_const_binop (MINUS_EXPR
, array_idx
,
1909 /* Convert the index to a byte offset. */
1910 array_idx
= fold_convert (sizetype
, array_idx
);
1911 array_idx
= int_const_binop (MULT_EXPR
, array_idx
, elt_size
, 0);
1913 /* Update the operands for the next round, or for folding. */
1914 /* If we're manipulating unsigned types, then folding into negative
1915 values can produce incorrect results. Particularly if the type
1916 is smaller than the width of the pointer. */
1918 && TYPE_UNSIGNED (TREE_TYPE (op1
))
1919 && tree_int_cst_lt (array_idx
, op1
))
1921 op1
= int_const_binop (subtract
? MINUS_EXPR
: PLUS_EXPR
,
1927 /* If we weren't able to fold the subtraction into another array reference,
1928 canonicalize the integer for passing to the array and component ref
1929 simplification functions. */
1932 if (TYPE_UNSIGNED (TREE_TYPE (op1
)))
1934 op1
= fold_unary (NEGATE_EXPR
, TREE_TYPE (op1
), op1
);
1935 /* ??? In theory fold should always produce another integer. */
1936 if (op1
== NULL
|| TREE_CODE (op1
) != INTEGER_CST
)
1940 ptd_type
= TREE_TYPE (ptr_type
);
1942 /* At which point we can try some of the same things as for indirects. */
1943 t
= maybe_fold_offset_to_array_ref (op0
, op1
, ptd_type
);
1945 t
= maybe_fold_offset_to_component_ref (TREE_TYPE (op0
), op0
, op1
,
1948 t
= build1 (ADDR_EXPR
, ptr_type
, t
);
1953 /* For passing state through walk_tree into fold_stmt_r and its
1956 struct fold_stmt_r_data
1960 bool *inside_addr_expr_p
;
1963 /* Subroutine of fold_stmt called via walk_tree. We perform several
1964 simplifications of EXPR_P, mostly having to do with pointer arithmetic. */
1967 fold_stmt_r (tree
*expr_p
, int *walk_subtrees
, void *data
)
1969 struct fold_stmt_r_data
*fold_stmt_r_data
= (struct fold_stmt_r_data
*) data
;
1970 bool *inside_addr_expr_p
= fold_stmt_r_data
->inside_addr_expr_p
;
1971 bool *changed_p
= fold_stmt_r_data
->changed_p
;
1972 tree expr
= *expr_p
, t
;
1974 /* ??? It'd be nice if walk_tree had a pre-order option. */
1975 switch (TREE_CODE (expr
))
1978 t
= walk_tree (&TREE_OPERAND (expr
, 0), fold_stmt_r
, data
, NULL
);
1983 t
= maybe_fold_stmt_indirect (expr
, TREE_OPERAND (expr
, 0),
1987 /* ??? Could handle more ARRAY_REFs here, as a variant of INDIRECT_REF.
1988 We'd only want to bother decomposing an existing ARRAY_REF if
1989 the base array is found to have another offset contained within.
1990 Otherwise we'd be wasting time. */
1992 /* If we are not processing expressions found within an
1993 ADDR_EXPR, then we can fold constant array references. */
1994 if (!*inside_addr_expr_p
)
1995 t
= fold_read_from_constant_string (expr
);
2001 *inside_addr_expr_p
= true;
2002 t
= walk_tree (&TREE_OPERAND (expr
, 0), fold_stmt_r
, data
, NULL
);
2003 *inside_addr_expr_p
= false;
2008 /* Set TREE_INVARIANT properly so that the value is properly
2009 considered constant, and so gets propagated as expected. */
2011 recompute_tree_invariant_for_addr_expr (expr
);
2016 t
= walk_tree (&TREE_OPERAND (expr
, 0), fold_stmt_r
, data
, NULL
);
2019 t
= walk_tree (&TREE_OPERAND (expr
, 1), fold_stmt_r
, data
, NULL
);
2024 t
= maybe_fold_stmt_addition (expr
);
2028 t
= walk_tree (&TREE_OPERAND (expr
, 0), fold_stmt_r
, data
, NULL
);
2033 /* Make sure the FIELD_DECL is actually a field in the type on the lhs.
2034 We've already checked that the records are compatible, so we should
2035 come up with a set of compatible fields. */
2037 tree expr_record
= TREE_TYPE (TREE_OPERAND (expr
, 0));
2038 tree expr_field
= TREE_OPERAND (expr
, 1);
2040 if (DECL_FIELD_CONTEXT (expr_field
) != TYPE_MAIN_VARIANT (expr_record
))
2042 expr_field
= find_compatible_field (expr_record
, expr_field
);
2043 TREE_OPERAND (expr
, 1) = expr_field
;
2048 case TARGET_MEM_REF
:
2049 t
= maybe_fold_tmr (expr
);
2053 if (COMPARISON_CLASS_P (TREE_OPERAND (expr
, 0)))
2055 tree op0
= TREE_OPERAND (expr
, 0);
2059 fold_defer_overflow_warnings ();
2060 tem
= fold_binary (TREE_CODE (op0
), TREE_TYPE (op0
),
2061 TREE_OPERAND (op0
, 0),
2062 TREE_OPERAND (op0
, 1));
2063 set
= tem
&& set_rhs (expr_p
, tem
);
2064 fold_undefer_overflow_warnings (set
, fold_stmt_r_data
->stmt
, 0);
2086 /* Return the string length, maximum string length or maximum value of
2088 If ARG is an SSA name variable, follow its use-def chains. If LENGTH
2089 is not NULL and, for TYPE == 0, its value is not equal to the length
2090 we determine or if we are unable to determine the length or value,
2091 return false. VISITED is a bitmap of visited variables.
2092 TYPE is 0 if string length should be returned, 1 for maximum string
2093 length and 2 for maximum value ARG can have. */
2096 get_maxval_strlen (tree arg
, tree
*length
, bitmap visited
, int type
)
2098 tree var
, def_stmt
, val
;
2100 if (TREE_CODE (arg
) != SSA_NAME
)
2105 if (TREE_CODE (val
) != INTEGER_CST
2106 || tree_int_cst_sgn (val
) < 0)
2110 val
= c_strlen (arg
, 1);
2118 if (TREE_CODE (*length
) != INTEGER_CST
2119 || TREE_CODE (val
) != INTEGER_CST
)
2122 if (tree_int_cst_lt (*length
, val
))
2126 else if (simple_cst_equal (val
, *length
) != 1)
2134 /* If we were already here, break the infinite cycle. */
2135 if (bitmap_bit_p (visited
, SSA_NAME_VERSION (arg
)))
2137 bitmap_set_bit (visited
, SSA_NAME_VERSION (arg
));
2140 def_stmt
= SSA_NAME_DEF_STMT (var
);
2142 switch (TREE_CODE (def_stmt
))
2148 /* The RHS of the statement defining VAR must either have a
2149 constant length or come from another SSA_NAME with a constant
2151 rhs
= TREE_OPERAND (def_stmt
, 1);
2153 return get_maxval_strlen (rhs
, length
, visited
, type
);
2158 /* All the arguments of the PHI node must have the same constant
2162 for (i
= 0; i
< PHI_NUM_ARGS (def_stmt
); i
++)
2164 tree arg
= PHI_ARG_DEF (def_stmt
, i
);
2166 /* If this PHI has itself as an argument, we cannot
2167 determine the string length of this argument. However,
2168 if we can find a constant string length for the other
2169 PHI args then we can still be sure that this is a
2170 constant string length. So be optimistic and just
2171 continue with the next argument. */
2172 if (arg
== PHI_RESULT (def_stmt
))
2175 if (!get_maxval_strlen (arg
, length
, visited
, type
))
2191 /* Fold builtin call FN in statement STMT. If it cannot be folded into a
2192 constant, return NULL_TREE. Otherwise, return its constant value. */
2195 ccp_fold_builtin (tree stmt
, tree fn
)
2197 tree result
, val
[3];
2198 tree callee
, arglist
, a
;
2199 int arg_mask
, i
, type
;
2203 ignore
= TREE_CODE (stmt
) != MODIFY_EXPR
;
2205 /* First try the generic builtin folder. If that succeeds, return the
2207 callee
= get_callee_fndecl (fn
);
2208 arglist
= TREE_OPERAND (fn
, 1);
2209 result
= fold_builtin (callee
, arglist
, ignore
);
2213 STRIP_NOPS (result
);
2217 /* Ignore MD builtins. */
2218 if (DECL_BUILT_IN_CLASS (callee
) == BUILT_IN_MD
)
2221 /* If the builtin could not be folded, and it has no argument list,
2226 /* Limit the work only for builtins we know how to simplify. */
2227 switch (DECL_FUNCTION_CODE (callee
))
2229 case BUILT_IN_STRLEN
:
2230 case BUILT_IN_FPUTS
:
2231 case BUILT_IN_FPUTS_UNLOCKED
:
2235 case BUILT_IN_STRCPY
:
2236 case BUILT_IN_STRNCPY
:
2240 case BUILT_IN_MEMCPY_CHK
:
2241 case BUILT_IN_MEMPCPY_CHK
:
2242 case BUILT_IN_MEMMOVE_CHK
:
2243 case BUILT_IN_MEMSET_CHK
:
2244 case BUILT_IN_STRNCPY_CHK
:
2248 case BUILT_IN_STRCPY_CHK
:
2249 case BUILT_IN_STPCPY_CHK
:
2253 case BUILT_IN_SNPRINTF_CHK
:
2254 case BUILT_IN_VSNPRINTF_CHK
:
2262 /* Try to use the dataflow information gathered by the CCP process. */
2263 visited
= BITMAP_ALLOC (NULL
);
2265 memset (val
, 0, sizeof (val
));
2266 for (i
= 0, a
= arglist
;
2268 i
++, arg_mask
>>= 1, a
= TREE_CHAIN (a
))
2271 bitmap_clear (visited
);
2272 if (!get_maxval_strlen (TREE_VALUE (a
), &val
[i
], visited
, type
))
2276 BITMAP_FREE (visited
);
2279 switch (DECL_FUNCTION_CODE (callee
))
2281 case BUILT_IN_STRLEN
:
2284 tree
new = fold_convert (TREE_TYPE (fn
), val
[0]);
2286 /* If the result is not a valid gimple value, or not a cast
2287 of a valid gimple value, then we can not use the result. */
2288 if (is_gimple_val (new)
2289 || (is_gimple_cast (new)
2290 && is_gimple_val (TREE_OPERAND (new, 0))))
2295 case BUILT_IN_STRCPY
:
2296 if (val
[1] && is_gimple_val (val
[1]))
2297 result
= fold_builtin_strcpy (callee
, arglist
, val
[1]);
2300 case BUILT_IN_STRNCPY
:
2301 if (val
[1] && is_gimple_val (val
[1]))
2302 result
= fold_builtin_strncpy (callee
, arglist
, val
[1]);
2305 case BUILT_IN_FPUTS
:
2306 result
= fold_builtin_fputs (arglist
,
2307 TREE_CODE (stmt
) != MODIFY_EXPR
, 0,
2311 case BUILT_IN_FPUTS_UNLOCKED
:
2312 result
= fold_builtin_fputs (arglist
,
2313 TREE_CODE (stmt
) != MODIFY_EXPR
, 1,
2317 case BUILT_IN_MEMCPY_CHK
:
2318 case BUILT_IN_MEMPCPY_CHK
:
2319 case BUILT_IN_MEMMOVE_CHK
:
2320 case BUILT_IN_MEMSET_CHK
:
2321 if (val
[2] && is_gimple_val (val
[2]))
2322 result
= fold_builtin_memory_chk (callee
, arglist
, val
[2], ignore
,
2323 DECL_FUNCTION_CODE (callee
));
2326 case BUILT_IN_STRCPY_CHK
:
2327 case BUILT_IN_STPCPY_CHK
:
2328 if (val
[1] && is_gimple_val (val
[1]))
2329 result
= fold_builtin_stxcpy_chk (callee
, arglist
, val
[1], ignore
,
2330 DECL_FUNCTION_CODE (callee
));
2333 case BUILT_IN_STRNCPY_CHK
:
2334 if (val
[2] && is_gimple_val (val
[2]))
2335 result
= fold_builtin_strncpy_chk (arglist
, val
[2]);
2338 case BUILT_IN_SNPRINTF_CHK
:
2339 case BUILT_IN_VSNPRINTF_CHK
:
2340 if (val
[1] && is_gimple_val (val
[1]))
2341 result
= fold_builtin_snprintf_chk (arglist
, val
[1],
2342 DECL_FUNCTION_CODE (callee
));
2349 if (result
&& ignore
)
2350 result
= fold_ignored_result (result
);
2355 /* Fold the statement pointed to by STMT_P. In some cases, this function may
2356 replace the whole statement with a new one. Returns true iff folding
2357 makes any changes. */
2360 fold_stmt (tree
*stmt_p
)
2362 tree rhs
, result
, stmt
;
2363 struct fold_stmt_r_data fold_stmt_r_data
;
2364 bool changed
= false;
2365 bool inside_addr_expr
= false;
2369 fold_stmt_r_data
.stmt
= stmt
;
2370 fold_stmt_r_data
.changed_p
= &changed
;
2371 fold_stmt_r_data
.inside_addr_expr_p
= &inside_addr_expr
;
2373 /* If we replaced constants and the statement makes pointer dereferences,
2374 then we may need to fold instances of *&VAR into VAR, etc. */
2375 if (walk_tree (stmt_p
, fold_stmt_r
, &fold_stmt_r_data
, NULL
))
2378 = build_function_call_expr (implicit_built_in_decls
[BUILT_IN_TRAP
],
2383 rhs
= get_rhs (stmt
);
2388 if (TREE_CODE (rhs
) == CALL_EXPR
)
2392 /* Check for builtins that CCP can handle using information not
2393 available in the generic fold routines. */
2394 callee
= get_callee_fndecl (rhs
);
2395 if (callee
&& DECL_BUILT_IN (callee
))
2396 result
= ccp_fold_builtin (stmt
, rhs
);
2399 /* Check for resolvable OBJ_TYPE_REF. The only sorts we can resolve
2400 here are when we've propagated the address of a decl into the
2402 /* ??? Should perhaps do this in fold proper. However, doing it
2403 there requires that we create a new CALL_EXPR, and that requires
2404 copying EH region info to the new node. Easier to just do it
2405 here where we can just smash the call operand. Also
2406 CALL_EXPR_RETURN_SLOT_OPT needs to be handled correctly and
2407 copied, fold_ternary does not have not information. */
2408 callee
= TREE_OPERAND (rhs
, 0);
2409 if (TREE_CODE (callee
) == OBJ_TYPE_REF
2410 && lang_hooks
.fold_obj_type_ref
2411 && TREE_CODE (OBJ_TYPE_REF_OBJECT (callee
)) == ADDR_EXPR
2412 && DECL_P (TREE_OPERAND
2413 (OBJ_TYPE_REF_OBJECT (callee
), 0)))
2417 /* ??? Caution: Broken ADDR_EXPR semantics means that
2418 looking at the type of the operand of the addr_expr
2419 can yield an array type. See silly exception in
2420 check_pointer_types_r. */
2422 t
= TREE_TYPE (TREE_TYPE (OBJ_TYPE_REF_OBJECT (callee
)));
2423 t
= lang_hooks
.fold_obj_type_ref (callee
, t
);
2426 TREE_OPERAND (rhs
, 0) = t
;
2433 /* If we couldn't fold the RHS, hand over to the generic fold routines. */
2434 if (result
== NULL_TREE
)
2435 result
= fold (rhs
);
2437 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
2438 may have been added by fold, and "useless" type conversions that might
2439 now be apparent due to propagation. */
2440 STRIP_USELESS_TYPE_CONVERSION (result
);
2443 changed
|= set_rhs (stmt_p
, result
);
2448 /* Perform the minimal folding on statement STMT. Only operations like
2449 *&x created by constant propagation are handled. The statement cannot
2450 be replaced with a new one. */
2453 fold_stmt_inplace (tree stmt
)
2455 tree old_stmt
= stmt
, rhs
, new_rhs
;
2456 struct fold_stmt_r_data fold_stmt_r_data
;
2457 bool changed
= false;
2458 bool inside_addr_expr
= false;
2460 fold_stmt_r_data
.stmt
= stmt
;
2461 fold_stmt_r_data
.changed_p
= &changed
;
2462 fold_stmt_r_data
.inside_addr_expr_p
= &inside_addr_expr
;
2464 walk_tree (&stmt
, fold_stmt_r
, &fold_stmt_r_data
, NULL
);
2465 gcc_assert (stmt
== old_stmt
);
2467 rhs
= get_rhs (stmt
);
2468 if (!rhs
|| rhs
== stmt
)
2471 new_rhs
= fold (rhs
);
2472 STRIP_USELESS_TYPE_CONVERSION (new_rhs
);
2476 changed
|= set_rhs (&stmt
, new_rhs
);
2477 gcc_assert (stmt
== old_stmt
);
2482 /* Convert EXPR into a GIMPLE value suitable for substitution on the
2483 RHS of an assignment. Insert the necessary statements before
2487 convert_to_gimple_builtin (block_stmt_iterator
*si_p
, tree expr
)
2489 tree_stmt_iterator ti
;
2490 tree stmt
= bsi_stmt (*si_p
);
2491 tree tmp
, stmts
= NULL
;
2493 push_gimplify_context ();
2494 tmp
= get_initialized_tmp_var (expr
, &stmts
, NULL
);
2495 pop_gimplify_context (NULL
);
2497 if (EXPR_HAS_LOCATION (stmt
))
2498 annotate_all_with_locus (&stmts
, EXPR_LOCATION (stmt
));
2500 /* The replacement can expose previously unreferenced variables. */
2501 for (ti
= tsi_start (stmts
); !tsi_end_p (ti
); tsi_next (&ti
))
2503 tree new_stmt
= tsi_stmt (ti
);
2504 find_new_referenced_vars (tsi_stmt_ptr (ti
));
2505 bsi_insert_before (si_p
, new_stmt
, BSI_NEW_STMT
);
2506 mark_new_vars_to_rename (bsi_stmt (*si_p
));
2514 /* A simple pass that attempts to fold all builtin functions. This pass
2515 is run after we've propagated as many constants as we can. */
2518 execute_fold_all_builtins (void)
2520 bool cfg_changed
= false;
2524 block_stmt_iterator i
;
2525 for (i
= bsi_start (bb
); !bsi_end_p (i
); )
2527 tree
*stmtp
= bsi_stmt_ptr (i
);
2528 tree old_stmt
= *stmtp
;
2529 tree call
= get_rhs (*stmtp
);
2530 tree callee
, result
;
2531 enum built_in_function fcode
;
2533 if (!call
|| TREE_CODE (call
) != CALL_EXPR
)
2538 callee
= get_callee_fndecl (call
);
2539 if (!callee
|| DECL_BUILT_IN_CLASS (callee
) != BUILT_IN_NORMAL
)
2544 fcode
= DECL_FUNCTION_CODE (callee
);
2546 result
= ccp_fold_builtin (*stmtp
, call
);
2548 switch (DECL_FUNCTION_CODE (callee
))
2550 case BUILT_IN_CONSTANT_P
:
2551 /* Resolve __builtin_constant_p. If it hasn't been
2552 folded to integer_one_node by now, it's fairly
2553 certain that the value simply isn't constant. */
2554 result
= integer_zero_node
;
2562 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2564 fprintf (dump_file
, "Simplified\n ");
2565 print_generic_stmt (dump_file
, *stmtp
, dump_flags
);
2568 if (!set_rhs (stmtp
, result
))
2570 result
= convert_to_gimple_builtin (&i
, result
);
2573 bool ok
= set_rhs (stmtp
, result
);
2578 mark_new_vars_to_rename (*stmtp
);
2579 if (maybe_clean_or_replace_eh_stmt (old_stmt
, *stmtp
)
2580 && tree_purge_dead_eh_edges (bb
))
2583 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2585 fprintf (dump_file
, "to\n ");
2586 print_generic_stmt (dump_file
, *stmtp
, dump_flags
);
2587 fprintf (dump_file
, "\n");
2590 /* Retry the same statement if it changed into another
2591 builtin, there might be new opportunities now. */
2592 call
= get_rhs (*stmtp
);
2593 if (!call
|| TREE_CODE (call
) != CALL_EXPR
)
2598 callee
= get_callee_fndecl (call
);
2600 || DECL_BUILT_IN_CLASS (callee
) != BUILT_IN_NORMAL
2601 || DECL_FUNCTION_CODE (callee
) == fcode
)
2606 /* Delete unreachable blocks. */
2608 cleanup_tree_cfg ();
2613 struct tree_opt_pass pass_fold_builtins
=
2617 execute_fold_all_builtins
, /* execute */
2620 0, /* static_pass_number */
2622 PROP_cfg
| PROP_ssa
| PROP_alias
, /* properties_required */
2623 0, /* properties_provided */
2624 0, /* properties_destroyed */
2625 0, /* todo_flags_start */
2628 | TODO_update_ssa
, /* todo_flags_finish */