1 /* Conditional constant propagation pass for the GNU compiler.
2 Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
3 2010, 2011 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.
104 Constant propagation with conditional branches,
105 Wegman and Zadeck, ACM TOPLAS 13(2):181-210.
107 Building an Optimizing Compiler,
108 Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9.
110 Advanced Compiler Design and Implementation,
111 Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */
115 #include "coretypes.h"
120 #include "basic-block.h"
122 #include "function.h"
123 #include "tree-pretty-print.h"
124 #include "gimple-pretty-print.h"
126 #include "tree-dump.h"
127 #include "tree-flow.h"
128 #include "tree-pass.h"
129 #include "tree-ssa-propagate.h"
130 #include "value-prof.h"
131 #include "langhooks.h"
133 #include "diagnostic-core.h"
135 #include "gimple-fold.h"
138 /* Possible lattice values. */
147 struct prop_value_d
{
149 ccp_lattice_t lattice_val
;
151 /* Propagated value. */
154 /* Mask that applies to the propagated value during CCP. For
155 X with a CONSTANT lattice value X & ~mask == value & ~mask. */
159 typedef struct prop_value_d prop_value_t
;
161 /* Array of propagated constant values. After propagation,
162 CONST_VAL[I].VALUE holds the constant value for SSA_NAME(I). If
163 the constant is held in an SSA name representing a memory store
164 (i.e., a VDEF), CONST_VAL[I].MEM_REF will contain the actual
165 memory reference used to store (i.e., the LHS of the assignment
167 static prop_value_t
*const_val
;
169 static void canonicalize_float_value (prop_value_t
*);
170 static bool ccp_fold_stmt (gimple_stmt_iterator
*);
172 /* Dump constant propagation value VAL to file OUTF prefixed by PREFIX. */
175 dump_lattice_value (FILE *outf
, const char *prefix
, prop_value_t val
)
177 switch (val
.lattice_val
)
180 fprintf (outf
, "%sUNINITIALIZED", prefix
);
183 fprintf (outf
, "%sUNDEFINED", prefix
);
186 fprintf (outf
, "%sVARYING", prefix
);
189 fprintf (outf
, "%sCONSTANT ", prefix
);
190 if (TREE_CODE (val
.value
) != INTEGER_CST
191 || double_int_zero_p (val
.mask
))
192 print_generic_expr (outf
, val
.value
, dump_flags
);
195 double_int cval
= double_int_and_not (tree_to_double_int (val
.value
),
197 fprintf (outf
, "%sCONSTANT " HOST_WIDE_INT_PRINT_DOUBLE_HEX
,
198 prefix
, cval
.high
, cval
.low
);
199 fprintf (outf
, " (" HOST_WIDE_INT_PRINT_DOUBLE_HEX
")",
200 val
.mask
.high
, val
.mask
.low
);
209 /* Print lattice value VAL to stderr. */
211 void debug_lattice_value (prop_value_t val
);
214 debug_lattice_value (prop_value_t val
)
216 dump_lattice_value (stderr
, "", val
);
217 fprintf (stderr
, "\n");
221 /* Compute a default value for variable VAR and store it in the
222 CONST_VAL array. The following rules are used to get default
225 1- Global and static variables that are declared constant are
228 2- Any other value is considered UNDEFINED. This is useful when
229 considering PHI nodes. PHI arguments that are undefined do not
230 change the constant value of the PHI node, which allows for more
231 constants to be propagated.
233 3- Variables defined by statements other than assignments and PHI
234 nodes are considered VARYING.
236 4- Initial values of variables that are not GIMPLE registers are
237 considered VARYING. */
240 get_default_value (tree var
)
242 tree sym
= SSA_NAME_VAR (var
);
243 prop_value_t val
= { UNINITIALIZED
, NULL_TREE
, { 0, 0 } };
246 stmt
= SSA_NAME_DEF_STMT (var
);
248 if (gimple_nop_p (stmt
))
250 /* Variables defined by an empty statement are those used
251 before being initialized. If VAR is a local variable, we
252 can assume initially that it is UNDEFINED, otherwise we must
253 consider it VARYING. */
254 if (is_gimple_reg (sym
)
255 && TREE_CODE (sym
) == VAR_DECL
)
256 val
.lattice_val
= UNDEFINED
;
259 val
.lattice_val
= VARYING
;
260 val
.mask
= double_int_minus_one
;
263 else if (is_gimple_assign (stmt
)
264 /* Value-returning GIMPLE_CALL statements assign to
265 a variable, and are treated similarly to GIMPLE_ASSIGN. */
266 || (is_gimple_call (stmt
)
267 && gimple_call_lhs (stmt
) != NULL_TREE
)
268 || gimple_code (stmt
) == GIMPLE_PHI
)
271 if (gimple_assign_single_p (stmt
)
272 && DECL_P (gimple_assign_rhs1 (stmt
))
273 && (cst
= get_symbol_constant_value (gimple_assign_rhs1 (stmt
))))
275 val
.lattice_val
= CONSTANT
;
279 /* Any other variable defined by an assignment or a PHI node
280 is considered UNDEFINED. */
281 val
.lattice_val
= UNDEFINED
;
285 /* Otherwise, VAR will never take on a constant value. */
286 val
.lattice_val
= VARYING
;
287 val
.mask
= double_int_minus_one
;
294 /* Get the constant value associated with variable VAR. */
296 static inline prop_value_t
*
301 if (const_val
== NULL
)
304 val
= &const_val
[SSA_NAME_VERSION (var
)];
305 if (val
->lattice_val
== UNINITIALIZED
)
306 *val
= get_default_value (var
);
308 canonicalize_float_value (val
);
313 /* Return the constant tree value associated with VAR. */
316 get_constant_value (tree var
)
319 if (TREE_CODE (var
) != SSA_NAME
)
321 if (is_gimple_min_invariant (var
))
325 val
= get_value (var
);
327 && val
->lattice_val
== CONSTANT
328 && (TREE_CODE (val
->value
) != INTEGER_CST
329 || double_int_zero_p (val
->mask
)))
334 /* Sets the value associated with VAR to VARYING. */
337 set_value_varying (tree var
)
339 prop_value_t
*val
= &const_val
[SSA_NAME_VERSION (var
)];
341 val
->lattice_val
= VARYING
;
342 val
->value
= NULL_TREE
;
343 val
->mask
= double_int_minus_one
;
346 /* For float types, modify the value of VAL to make ccp work correctly
347 for non-standard values (-0, NaN):
349 If HONOR_SIGNED_ZEROS is false, and VAL = -0, we canonicalize it to 0.
350 If HONOR_NANS is false, and VAL is NaN, we canonicalize it to UNDEFINED.
351 This is to fix the following problem (see PR 29921): Suppose we have
355 and we set value of y to NaN. This causes value of x to be set to NaN.
356 When we later determine that y is in fact VARYING, fold uses the fact
357 that HONOR_NANS is false, and we try to change the value of x to 0,
358 causing an ICE. With HONOR_NANS being false, the real appearance of
359 NaN would cause undefined behavior, though, so claiming that y (and x)
360 are UNDEFINED initially is correct. */
363 canonicalize_float_value (prop_value_t
*val
)
365 enum machine_mode mode
;
369 if (val
->lattice_val
!= CONSTANT
370 || TREE_CODE (val
->value
) != REAL_CST
)
373 d
= TREE_REAL_CST (val
->value
);
374 type
= TREE_TYPE (val
->value
);
375 mode
= TYPE_MODE (type
);
377 if (!HONOR_SIGNED_ZEROS (mode
)
378 && REAL_VALUE_MINUS_ZERO (d
))
380 val
->value
= build_real (type
, dconst0
);
384 if (!HONOR_NANS (mode
)
385 && REAL_VALUE_ISNAN (d
))
387 val
->lattice_val
= UNDEFINED
;
393 /* Return whether the lattice transition is valid. */
396 valid_lattice_transition (prop_value_t old_val
, prop_value_t new_val
)
398 /* Lattice transitions must always be monotonically increasing in
400 if (old_val
.lattice_val
< new_val
.lattice_val
)
403 if (old_val
.lattice_val
!= new_val
.lattice_val
)
406 if (!old_val
.value
&& !new_val
.value
)
409 /* Now both lattice values are CONSTANT. */
411 /* Allow transitioning from &x to &x & ~3. */
412 if (TREE_CODE (old_val
.value
) != INTEGER_CST
413 && TREE_CODE (new_val
.value
) == INTEGER_CST
)
416 /* Bit-lattices have to agree in the still valid bits. */
417 if (TREE_CODE (old_val
.value
) == INTEGER_CST
418 && TREE_CODE (new_val
.value
) == INTEGER_CST
)
419 return double_int_equal_p
420 (double_int_and_not (tree_to_double_int (old_val
.value
),
422 double_int_and_not (tree_to_double_int (new_val
.value
),
425 /* Otherwise constant values have to agree. */
426 return operand_equal_p (old_val
.value
, new_val
.value
, 0);
429 /* Set the value for variable VAR to NEW_VAL. Return true if the new
430 value is different from VAR's previous value. */
433 set_lattice_value (tree var
, prop_value_t new_val
)
435 /* We can deal with old UNINITIALIZED values just fine here. */
436 prop_value_t
*old_val
= &const_val
[SSA_NAME_VERSION (var
)];
438 canonicalize_float_value (&new_val
);
440 /* We have to be careful to not go up the bitwise lattice
441 represented by the mask.
442 ??? This doesn't seem to be the best place to enforce this. */
443 if (new_val
.lattice_val
== CONSTANT
444 && old_val
->lattice_val
== CONSTANT
445 && TREE_CODE (new_val
.value
) == INTEGER_CST
446 && TREE_CODE (old_val
->value
) == INTEGER_CST
)
449 diff
= double_int_xor (tree_to_double_int (new_val
.value
),
450 tree_to_double_int (old_val
->value
));
451 new_val
.mask
= double_int_ior (new_val
.mask
,
452 double_int_ior (old_val
->mask
, diff
));
455 gcc_assert (valid_lattice_transition (*old_val
, new_val
));
457 /* If *OLD_VAL and NEW_VAL are the same, return false to inform the
458 caller that this was a non-transition. */
459 if (old_val
->lattice_val
!= new_val
.lattice_val
460 || (new_val
.lattice_val
== CONSTANT
461 && TREE_CODE (new_val
.value
) == INTEGER_CST
462 && (TREE_CODE (old_val
->value
) != INTEGER_CST
463 || !double_int_equal_p (new_val
.mask
, old_val
->mask
))))
465 /* ??? We would like to delay creation of INTEGER_CSTs from
466 partially constants here. */
468 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
470 dump_lattice_value (dump_file
, "Lattice value changed to ", new_val
);
471 fprintf (dump_file
, ". Adding SSA edges to worklist.\n");
476 gcc_assert (new_val
.lattice_val
!= UNINITIALIZED
);
483 static prop_value_t
get_value_for_expr (tree
, bool);
484 static prop_value_t
bit_value_binop (enum tree_code
, tree
, tree
, tree
);
485 static void bit_value_binop_1 (enum tree_code
, tree
, double_int
*, double_int
*,
486 tree
, double_int
, double_int
,
487 tree
, double_int
, double_int
);
489 /* Return a double_int that can be used for bitwise simplifications
493 value_to_double_int (prop_value_t val
)
496 && TREE_CODE (val
.value
) == INTEGER_CST
)
497 return tree_to_double_int (val
.value
);
499 return double_int_zero
;
502 /* Return the value for the address expression EXPR based on alignment
506 get_value_from_alignment (tree expr
)
509 HOST_WIDE_INT bitsize
, bitpos
;
511 enum machine_mode mode
;
514 gcc_assert (TREE_CODE (expr
) == ADDR_EXPR
);
516 base
= get_inner_reference (TREE_OPERAND (expr
, 0),
517 &bitsize
, &bitpos
, &offset
,
518 &mode
, &align
, &align
, false);
519 if (TREE_CODE (base
) == MEM_REF
)
520 val
= bit_value_binop (PLUS_EXPR
, TREE_TYPE (expr
),
521 TREE_OPERAND (base
, 0), TREE_OPERAND (base
, 1));
523 && ((align
= get_object_alignment (base
, BIGGEST_ALIGNMENT
))
526 val
.lattice_val
= CONSTANT
;
527 /* We assume pointers are zero-extended. */
528 val
.mask
= double_int_and_not
529 (double_int_mask (TYPE_PRECISION (TREE_TYPE (expr
))),
530 uhwi_to_double_int (align
/ BITS_PER_UNIT
- 1));
531 val
.value
= build_int_cst (TREE_TYPE (expr
), 0);
535 val
.lattice_val
= VARYING
;
536 val
.mask
= double_int_minus_one
;
537 val
.value
= NULL_TREE
;
541 double_int value
, mask
;
542 bit_value_binop_1 (PLUS_EXPR
, TREE_TYPE (expr
), &value
, &mask
,
543 TREE_TYPE (expr
), value_to_double_int (val
), val
.mask
,
545 shwi_to_double_int (bitpos
/ BITS_PER_UNIT
),
547 val
.lattice_val
= double_int_minus_one_p (mask
) ? VARYING
: CONSTANT
;
549 if (val
.lattice_val
== CONSTANT
)
550 val
.value
= double_int_to_tree (TREE_TYPE (expr
), value
);
552 val
.value
= NULL_TREE
;
554 /* ??? We should handle i * 4 and more complex expressions from
555 the offset, possibly by just expanding get_value_for_expr. */
556 if (offset
!= NULL_TREE
)
558 double_int value
, mask
;
559 prop_value_t oval
= get_value_for_expr (offset
, true);
560 bit_value_binop_1 (PLUS_EXPR
, TREE_TYPE (expr
), &value
, &mask
,
561 TREE_TYPE (expr
), value_to_double_int (val
), val
.mask
,
562 TREE_TYPE (expr
), value_to_double_int (oval
),
565 if (double_int_minus_one_p (mask
))
567 val
.lattice_val
= VARYING
;
568 val
.value
= NULL_TREE
;
572 val
.lattice_val
= CONSTANT
;
573 val
.value
= double_int_to_tree (TREE_TYPE (expr
), value
);
580 /* Return the value for the tree operand EXPR. If FOR_BITS_P is true
581 return constant bits extracted from alignment information for
582 invariant addresses. */
585 get_value_for_expr (tree expr
, bool for_bits_p
)
589 if (TREE_CODE (expr
) == SSA_NAME
)
591 val
= *get_value (expr
);
593 && val
.lattice_val
== CONSTANT
594 && TREE_CODE (val
.value
) == ADDR_EXPR
)
595 val
= get_value_from_alignment (val
.value
);
597 else if (is_gimple_min_invariant (expr
)
598 && (!for_bits_p
|| TREE_CODE (expr
) != ADDR_EXPR
))
600 val
.lattice_val
= CONSTANT
;
602 val
.mask
= double_int_zero
;
603 canonicalize_float_value (&val
);
605 else if (TREE_CODE (expr
) == ADDR_EXPR
)
606 val
= get_value_from_alignment (expr
);
609 val
.lattice_val
= VARYING
;
610 val
.mask
= double_int_minus_one
;
611 val
.value
= NULL_TREE
;
616 /* Return the likely CCP lattice value for STMT.
618 If STMT has no operands, then return CONSTANT.
620 Else if undefinedness of operands of STMT cause its value to be
621 undefined, then return UNDEFINED.
623 Else if any operands of STMT are constants, then return CONSTANT.
625 Else return VARYING. */
628 likely_value (gimple stmt
)
630 bool has_constant_operand
, has_undefined_operand
, all_undefined_operands
;
635 enum gimple_code code
= gimple_code (stmt
);
637 /* This function appears to be called only for assignments, calls,
638 conditionals, and switches, due to the logic in visit_stmt. */
639 gcc_assert (code
== GIMPLE_ASSIGN
640 || code
== GIMPLE_CALL
641 || code
== GIMPLE_COND
642 || code
== GIMPLE_SWITCH
);
644 /* If the statement has volatile operands, it won't fold to a
646 if (gimple_has_volatile_ops (stmt
))
649 /* Arrive here for more complex cases. */
650 has_constant_operand
= false;
651 has_undefined_operand
= false;
652 all_undefined_operands
= true;
653 FOR_EACH_SSA_TREE_OPERAND (use
, stmt
, iter
, SSA_OP_USE
)
655 prop_value_t
*val
= get_value (use
);
657 if (val
->lattice_val
== UNDEFINED
)
658 has_undefined_operand
= true;
660 all_undefined_operands
= false;
662 if (val
->lattice_val
== CONSTANT
)
663 has_constant_operand
= true;
666 /* There may be constants in regular rhs operands. For calls we
667 have to ignore lhs, fndecl and static chain, otherwise only
669 for (i
= (is_gimple_call (stmt
) ? 2 : 0) + gimple_has_lhs (stmt
);
670 i
< gimple_num_ops (stmt
); ++i
)
672 tree op
= gimple_op (stmt
, i
);
673 if (!op
|| TREE_CODE (op
) == SSA_NAME
)
675 if (is_gimple_min_invariant (op
))
676 has_constant_operand
= true;
679 if (has_constant_operand
)
680 all_undefined_operands
= false;
682 /* If the operation combines operands like COMPLEX_EXPR make sure to
683 not mark the result UNDEFINED if only one part of the result is
685 if (has_undefined_operand
&& all_undefined_operands
)
687 else if (code
== GIMPLE_ASSIGN
&& has_undefined_operand
)
689 switch (gimple_assign_rhs_code (stmt
))
691 /* Unary operators are handled with all_undefined_operands. */
694 case POINTER_PLUS_EXPR
:
695 /* Not MIN_EXPR, MAX_EXPR. One VARYING operand may be selected.
696 Not bitwise operators, one VARYING operand may specify the
697 result completely. Not logical operators for the same reason.
698 Not COMPLEX_EXPR as one VARYING operand makes the result partly
699 not UNDEFINED. Not *DIV_EXPR, comparisons and shifts because
700 the undefined operand may be promoted. */
707 /* If there was an UNDEFINED operand but the result may be not UNDEFINED
708 fall back to VARYING even if there were CONSTANT operands. */
709 if (has_undefined_operand
)
712 /* We do not consider virtual operands here -- load from read-only
713 memory may have only VARYING virtual operands, but still be
715 if (has_constant_operand
716 || gimple_references_memory_p (stmt
))
722 /* Returns true if STMT cannot be constant. */
725 surely_varying_stmt_p (gimple stmt
)
727 /* If the statement has operands that we cannot handle, it cannot be
729 if (gimple_has_volatile_ops (stmt
))
732 /* If it is a call and does not return a value or is not a
733 builtin and not an indirect call, it is varying. */
734 if (is_gimple_call (stmt
))
737 if (!gimple_call_lhs (stmt
)
738 || ((fndecl
= gimple_call_fndecl (stmt
)) != NULL_TREE
739 && !DECL_BUILT_IN (fndecl
)))
743 /* Any other store operation is not interesting. */
744 else if (gimple_vdef (stmt
))
747 /* Anything other than assignments and conditional jumps are not
748 interesting for CCP. */
749 if (gimple_code (stmt
) != GIMPLE_ASSIGN
750 && gimple_code (stmt
) != GIMPLE_COND
751 && gimple_code (stmt
) != GIMPLE_SWITCH
752 && gimple_code (stmt
) != GIMPLE_CALL
)
758 /* Initialize local data structures for CCP. */
761 ccp_initialize (void)
765 const_val
= XCNEWVEC (prop_value_t
, num_ssa_names
);
767 /* Initialize simulation flags for PHI nodes and statements. */
770 gimple_stmt_iterator i
;
772 for (i
= gsi_start_bb (bb
); !gsi_end_p (i
); gsi_next (&i
))
774 gimple stmt
= gsi_stmt (i
);
777 /* If the statement is a control insn, then we do not
778 want to avoid simulating the statement once. Failure
779 to do so means that those edges will never get added. */
780 if (stmt_ends_bb_p (stmt
))
783 is_varying
= surely_varying_stmt_p (stmt
);
790 /* If the statement will not produce a constant, mark
791 all its outputs VARYING. */
792 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_ALL_DEFS
)
793 set_value_varying (def
);
795 prop_set_simulate_again (stmt
, !is_varying
);
799 /* Now process PHI nodes. We never clear the simulate_again flag on
800 phi nodes, since we do not know which edges are executable yet,
801 except for phi nodes for virtual operands when we do not do store ccp. */
804 gimple_stmt_iterator i
;
806 for (i
= gsi_start_phis (bb
); !gsi_end_p (i
); gsi_next (&i
))
808 gimple phi
= gsi_stmt (i
);
810 if (!is_gimple_reg (gimple_phi_result (phi
)))
811 prop_set_simulate_again (phi
, false);
813 prop_set_simulate_again (phi
, true);
818 /* Debug count support. Reset the values of ssa names
819 VARYING when the total number ssa names analyzed is
820 beyond the debug count specified. */
826 for (i
= 0; i
< num_ssa_names
; i
++)
830 const_val
[i
].lattice_val
= VARYING
;
831 const_val
[i
].mask
= double_int_minus_one
;
832 const_val
[i
].value
= NULL_TREE
;
838 /* Do final substitution of propagated values, cleanup the flowgraph and
839 free allocated storage.
841 Return TRUE when something was optimized. */
846 bool something_changed
;
851 /* Derive alignment and misalignment information from partially
852 constant pointers in the lattice. */
853 for (i
= 1; i
< num_ssa_names
; ++i
)
855 tree name
= ssa_name (i
);
857 struct ptr_info_def
*pi
;
858 unsigned int tem
, align
;
861 || !POINTER_TYPE_P (TREE_TYPE (name
)))
864 val
= get_value (name
);
865 if (val
->lattice_val
!= CONSTANT
866 || TREE_CODE (val
->value
) != INTEGER_CST
)
869 /* Trailing constant bits specify the alignment, trailing value
870 bits the misalignment. */
872 align
= (tem
& -tem
);
876 pi
= get_ptr_info (name
);
878 pi
->misalign
= TREE_INT_CST_LOW (val
->value
) & (align
- 1);
881 /* Perform substitutions based on the known constant values. */
882 something_changed
= substitute_and_fold (get_constant_value
,
883 ccp_fold_stmt
, true);
887 return something_changed
;;
891 /* Compute the meet operator between *VAL1 and *VAL2. Store the result
894 any M UNDEFINED = any
895 any M VARYING = VARYING
896 Ci M Cj = Ci if (i == j)
897 Ci M Cj = VARYING if (i != j)
901 ccp_lattice_meet (prop_value_t
*val1
, prop_value_t
*val2
)
903 if (val1
->lattice_val
== UNDEFINED
)
905 /* UNDEFINED M any = any */
908 else if (val2
->lattice_val
== UNDEFINED
)
910 /* any M UNDEFINED = any
911 Nothing to do. VAL1 already contains the value we want. */
914 else if (val1
->lattice_val
== VARYING
915 || val2
->lattice_val
== VARYING
)
917 /* any M VARYING = VARYING. */
918 val1
->lattice_val
= VARYING
;
919 val1
->mask
= double_int_minus_one
;
920 val1
->value
= NULL_TREE
;
922 else if (val1
->lattice_val
== CONSTANT
923 && val2
->lattice_val
== CONSTANT
924 && TREE_CODE (val1
->value
) == INTEGER_CST
925 && TREE_CODE (val2
->value
) == INTEGER_CST
)
927 /* Ci M Cj = Ci if (i == j)
928 Ci M Cj = VARYING if (i != j)
930 For INTEGER_CSTs mask unequal bits. If no equal bits remain,
933 = double_int_ior (double_int_ior (val1
->mask
,
935 double_int_xor (tree_to_double_int (val1
->value
),
936 tree_to_double_int (val2
->value
)));
937 if (double_int_minus_one_p (val1
->mask
))
939 val1
->lattice_val
= VARYING
;
940 val1
->value
= NULL_TREE
;
943 else if (val1
->lattice_val
== CONSTANT
944 && val2
->lattice_val
== CONSTANT
945 && simple_cst_equal (val1
->value
, val2
->value
) == 1)
947 /* Ci M Cj = Ci if (i == j)
948 Ci M Cj = VARYING if (i != j)
950 VAL1 already contains the value we want for equivalent values. */
952 else if (val1
->lattice_val
== CONSTANT
953 && val2
->lattice_val
== CONSTANT
954 && (TREE_CODE (val1
->value
) == ADDR_EXPR
955 || TREE_CODE (val2
->value
) == ADDR_EXPR
))
957 /* When not equal addresses are involved try meeting for
959 prop_value_t tem
= *val2
;
960 if (TREE_CODE (val1
->value
) == ADDR_EXPR
)
961 *val1
= get_value_for_expr (val1
->value
, true);
962 if (TREE_CODE (val2
->value
) == ADDR_EXPR
)
963 tem
= get_value_for_expr (val2
->value
, true);
964 ccp_lattice_meet (val1
, &tem
);
968 /* Any other combination is VARYING. */
969 val1
->lattice_val
= VARYING
;
970 val1
->mask
= double_int_minus_one
;
971 val1
->value
= NULL_TREE
;
976 /* Loop through the PHI_NODE's parameters for BLOCK and compare their
977 lattice values to determine PHI_NODE's lattice value. The value of a
978 PHI node is determined calling ccp_lattice_meet with all the arguments
979 of the PHI node that are incoming via executable edges. */
981 static enum ssa_prop_result
982 ccp_visit_phi_node (gimple phi
)
985 prop_value_t
*old_val
, new_val
;
987 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
989 fprintf (dump_file
, "\nVisiting PHI node: ");
990 print_gimple_stmt (dump_file
, phi
, 0, dump_flags
);
993 old_val
= get_value (gimple_phi_result (phi
));
994 switch (old_val
->lattice_val
)
997 return SSA_PROP_VARYING
;
1004 new_val
.lattice_val
= UNDEFINED
;
1005 new_val
.value
= NULL_TREE
;
1012 for (i
= 0; i
< gimple_phi_num_args (phi
); i
++)
1014 /* Compute the meet operator over all the PHI arguments flowing
1015 through executable edges. */
1016 edge e
= gimple_phi_arg_edge (phi
, i
);
1018 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1021 "\n Argument #%d (%d -> %d %sexecutable)\n",
1022 i
, e
->src
->index
, e
->dest
->index
,
1023 (e
->flags
& EDGE_EXECUTABLE
) ? "" : "not ");
1026 /* If the incoming edge is executable, Compute the meet operator for
1027 the existing value of the PHI node and the current PHI argument. */
1028 if (e
->flags
& EDGE_EXECUTABLE
)
1030 tree arg
= gimple_phi_arg (phi
, i
)->def
;
1031 prop_value_t arg_val
= get_value_for_expr (arg
, false);
1033 ccp_lattice_meet (&new_val
, &arg_val
);
1035 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1037 fprintf (dump_file
, "\t");
1038 print_generic_expr (dump_file
, arg
, dump_flags
);
1039 dump_lattice_value (dump_file
, "\tValue: ", arg_val
);
1040 fprintf (dump_file
, "\n");
1043 if (new_val
.lattice_val
== VARYING
)
1048 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1050 dump_lattice_value (dump_file
, "\n PHI node value: ", new_val
);
1051 fprintf (dump_file
, "\n\n");
1054 /* Make the transition to the new value. */
1055 if (set_lattice_value (gimple_phi_result (phi
), new_val
))
1057 if (new_val
.lattice_val
== VARYING
)
1058 return SSA_PROP_VARYING
;
1060 return SSA_PROP_INTERESTING
;
1063 return SSA_PROP_NOT_INTERESTING
;
1066 /* Return the constant value for OP or OP otherwise. */
1069 valueize_op (tree op
)
1071 if (TREE_CODE (op
) == SSA_NAME
)
1073 tree tem
= get_constant_value (op
);
1080 /* CCP specific front-end to the non-destructive constant folding
1083 Attempt to simplify the RHS of STMT knowing that one or more
1084 operands are constants.
1086 If simplification is possible, return the simplified RHS,
1087 otherwise return the original RHS or NULL_TREE. */
1090 ccp_fold (gimple stmt
)
1092 location_t loc
= gimple_location (stmt
);
1093 switch (gimple_code (stmt
))
1097 /* Handle comparison operators that can appear in GIMPLE form. */
1098 tree op0
= valueize_op (gimple_cond_lhs (stmt
));
1099 tree op1
= valueize_op (gimple_cond_rhs (stmt
));
1100 enum tree_code code
= gimple_cond_code (stmt
);
1101 return fold_binary_loc (loc
, code
, boolean_type_node
, op0
, op1
);
1106 /* Return the constant switch index. */
1107 return valueize_op (gimple_switch_index (stmt
));
1112 return gimple_fold_stmt_to_constant_1 (stmt
, valueize_op
);
1119 /* Apply the operation CODE in type TYPE to the value, mask pair
1120 RVAL and RMASK representing a value of type RTYPE and set
1121 the value, mask pair *VAL and *MASK to the result. */
1124 bit_value_unop_1 (enum tree_code code
, tree type
,
1125 double_int
*val
, double_int
*mask
,
1126 tree rtype
, double_int rval
, double_int rmask
)
1132 *val
= double_int_not (rval
);
1137 double_int temv
, temm
;
1138 /* Return ~rval + 1. */
1139 bit_value_unop_1 (BIT_NOT_EXPR
, type
, &temv
, &temm
, type
, rval
, rmask
);
1140 bit_value_binop_1 (PLUS_EXPR
, type
, val
, mask
,
1142 type
, double_int_one
, double_int_zero
);
1150 /* First extend mask and value according to the original type. */
1151 uns
= (TREE_CODE (rtype
) == INTEGER_TYPE
&& TYPE_IS_SIZETYPE (rtype
)
1152 ? 0 : TYPE_UNSIGNED (rtype
));
1153 *mask
= double_int_ext (rmask
, TYPE_PRECISION (rtype
), uns
);
1154 *val
= double_int_ext (rval
, TYPE_PRECISION (rtype
), uns
);
1156 /* Then extend mask and value according to the target type. */
1157 uns
= (TREE_CODE (type
) == INTEGER_TYPE
&& TYPE_IS_SIZETYPE (type
)
1158 ? 0 : TYPE_UNSIGNED (type
));
1159 *mask
= double_int_ext (*mask
, TYPE_PRECISION (type
), uns
);
1160 *val
= double_int_ext (*val
, TYPE_PRECISION (type
), uns
);
1165 *mask
= double_int_minus_one
;
1170 /* Apply the operation CODE in type TYPE to the value, mask pairs
1171 R1VAL, R1MASK and R2VAL, R2MASK representing a values of type R1TYPE
1172 and R2TYPE and set the value, mask pair *VAL and *MASK to the result. */
1175 bit_value_binop_1 (enum tree_code code
, tree type
,
1176 double_int
*val
, double_int
*mask
,
1177 tree r1type
, double_int r1val
, double_int r1mask
,
1178 tree r2type
, double_int r2val
, double_int r2mask
)
1180 bool uns
= (TREE_CODE (type
) == INTEGER_TYPE
1181 && TYPE_IS_SIZETYPE (type
) ? 0 : TYPE_UNSIGNED (type
));
1182 /* Assume we'll get a constant result. Use an initial varying value,
1183 we fall back to varying in the end if necessary. */
1184 *mask
= double_int_minus_one
;
1188 /* The mask is constant where there is a known not
1189 set bit, (m1 | m2) & ((v1 | m1) & (v2 | m2)) */
1190 *mask
= double_int_and (double_int_ior (r1mask
, r2mask
),
1191 double_int_and (double_int_ior (r1val
, r1mask
),
1192 double_int_ior (r2val
, r2mask
)));
1193 *val
= double_int_and (r1val
, r2val
);
1197 /* The mask is constant where there is a known
1198 set bit, (m1 | m2) & ~((v1 & ~m1) | (v2 & ~m2)). */
1199 *mask
= double_int_and_not
1200 (double_int_ior (r1mask
, r2mask
),
1201 double_int_ior (double_int_and_not (r1val
, r1mask
),
1202 double_int_and_not (r2val
, r2mask
)));
1203 *val
= double_int_ior (r1val
, r2val
);
1208 *mask
= double_int_ior (r1mask
, r2mask
);
1209 *val
= double_int_xor (r1val
, r2val
);
1214 if (double_int_zero_p (r2mask
))
1216 HOST_WIDE_INT shift
= r2val
.low
;
1217 if (code
== RROTATE_EXPR
)
1219 *mask
= double_int_lrotate (r1mask
, shift
, TYPE_PRECISION (type
));
1220 *val
= double_int_lrotate (r1val
, shift
, TYPE_PRECISION (type
));
1226 /* ??? We can handle partially known shift counts if we know
1227 its sign. That way we can tell that (x << (y | 8)) & 255
1229 if (double_int_zero_p (r2mask
))
1231 HOST_WIDE_INT shift
= r2val
.low
;
1232 if (code
== RSHIFT_EXPR
)
1234 /* We need to know if we are doing a left or a right shift
1235 to properly shift in zeros for left shift and unsigned
1236 right shifts and the sign bit for signed right shifts.
1237 For signed right shifts we shift in varying in case
1238 the sign bit was varying. */
1241 *mask
= double_int_lshift (r1mask
, shift
,
1242 TYPE_PRECISION (type
), false);
1243 *val
= double_int_lshift (r1val
, shift
,
1244 TYPE_PRECISION (type
), false);
1248 /* ??? We can have sizetype related inconsistencies in
1250 if ((TREE_CODE (r1type
) == INTEGER_TYPE
1251 && (TYPE_IS_SIZETYPE (r1type
)
1252 ? 0 : TYPE_UNSIGNED (r1type
))) != uns
)
1256 *mask
= double_int_rshift (r1mask
, shift
,
1257 TYPE_PRECISION (type
), !uns
);
1258 *val
= double_int_rshift (r1val
, shift
,
1259 TYPE_PRECISION (type
), !uns
);
1270 case POINTER_PLUS_EXPR
:
1273 /* Do the addition with unknown bits set to zero, to give carry-ins of
1274 zero wherever possible. */
1275 lo
= double_int_add (double_int_and_not (r1val
, r1mask
),
1276 double_int_and_not (r2val
, r2mask
));
1277 lo
= double_int_ext (lo
, TYPE_PRECISION (type
), uns
);
1278 /* Do the addition with unknown bits set to one, to give carry-ins of
1279 one wherever possible. */
1280 hi
= double_int_add (double_int_ior (r1val
, r1mask
),
1281 double_int_ior (r2val
, r2mask
));
1282 hi
= double_int_ext (hi
, TYPE_PRECISION (type
), uns
);
1283 /* Each bit in the result is known if (a) the corresponding bits in
1284 both inputs are known, and (b) the carry-in to that bit position
1285 is known. We can check condition (b) by seeing if we got the same
1286 result with minimised carries as with maximised carries. */
1287 *mask
= double_int_ior (double_int_ior (r1mask
, r2mask
),
1288 double_int_xor (lo
, hi
));
1289 *mask
= double_int_ext (*mask
, TYPE_PRECISION (type
), uns
);
1290 /* It shouldn't matter whether we choose lo or hi here. */
1297 double_int temv
, temm
;
1298 bit_value_unop_1 (NEGATE_EXPR
, r2type
, &temv
, &temm
,
1299 r2type
, r2val
, r2mask
);
1300 bit_value_binop_1 (PLUS_EXPR
, type
, val
, mask
,
1301 r1type
, r1val
, r1mask
,
1302 r2type
, temv
, temm
);
1308 /* Just track trailing zeros in both operands and transfer
1309 them to the other. */
1310 int r1tz
= double_int_ctz (double_int_ior (r1val
, r1mask
));
1311 int r2tz
= double_int_ctz (double_int_ior (r2val
, r2mask
));
1312 if (r1tz
+ r2tz
>= HOST_BITS_PER_DOUBLE_INT
)
1314 *mask
= double_int_zero
;
1315 *val
= double_int_zero
;
1317 else if (r1tz
+ r2tz
> 0)
1319 *mask
= double_int_not (double_int_mask (r1tz
+ r2tz
));
1320 *mask
= double_int_ext (*mask
, TYPE_PRECISION (type
), uns
);
1321 *val
= double_int_zero
;
1329 double_int m
= double_int_ior (r1mask
, r2mask
);
1330 if (!double_int_equal_p (double_int_and_not (r1val
, m
),
1331 double_int_and_not (r2val
, m
)))
1333 *mask
= double_int_zero
;
1334 *val
= ((code
== EQ_EXPR
) ? double_int_zero
: double_int_one
);
1338 /* We know the result of a comparison is always one or zero. */
1339 *mask
= double_int_one
;
1340 *val
= double_int_zero
;
1348 double_int tem
= r1val
;
1354 code
= swap_tree_comparison (code
);
1361 /* If the most significant bits are not known we know nothing. */
1362 if (double_int_negative_p (r1mask
) || double_int_negative_p (r2mask
))
1365 /* For comparisons the signedness is in the comparison operands. */
1366 uns
= (TREE_CODE (r1type
) == INTEGER_TYPE
1367 && TYPE_IS_SIZETYPE (r1type
) ? 0 : TYPE_UNSIGNED (r1type
));
1368 /* ??? We can have sizetype related inconsistencies in the IL. */
1369 if ((TREE_CODE (r2type
) == INTEGER_TYPE
1370 && TYPE_IS_SIZETYPE (r2type
) ? 0 : TYPE_UNSIGNED (r2type
)) != uns
)
1373 /* If we know the most significant bits we know the values
1374 value ranges by means of treating varying bits as zero
1375 or one. Do a cross comparison of the max/min pairs. */
1376 maxmin
= double_int_cmp (double_int_ior (r1val
, r1mask
),
1377 double_int_and_not (r2val
, r2mask
), uns
);
1378 minmax
= double_int_cmp (double_int_and_not (r1val
, r1mask
),
1379 double_int_ior (r2val
, r2mask
), uns
);
1380 if (maxmin
< 0) /* r1 is less than r2. */
1382 *mask
= double_int_zero
;
1383 *val
= double_int_one
;
1385 else if (minmax
> 0) /* r1 is not less or equal to r2. */
1387 *mask
= double_int_zero
;
1388 *val
= double_int_zero
;
1390 else if (maxmin
== minmax
) /* r1 and r2 are equal. */
1392 /* This probably should never happen as we'd have
1393 folded the thing during fully constant value folding. */
1394 *mask
= double_int_zero
;
1395 *val
= (code
== LE_EXPR
? double_int_one
: double_int_zero
);
1399 /* We know the result of a comparison is always one or zero. */
1400 *mask
= double_int_one
;
1401 *val
= double_int_zero
;
1410 /* Return the propagation value when applying the operation CODE to
1411 the value RHS yielding type TYPE. */
1414 bit_value_unop (enum tree_code code
, tree type
, tree rhs
)
1416 prop_value_t rval
= get_value_for_expr (rhs
, true);
1417 double_int value
, mask
;
1419 gcc_assert ((rval
.lattice_val
== CONSTANT
1420 && TREE_CODE (rval
.value
) == INTEGER_CST
)
1421 || double_int_minus_one_p (rval
.mask
));
1422 bit_value_unop_1 (code
, type
, &value
, &mask
,
1423 TREE_TYPE (rhs
), value_to_double_int (rval
), rval
.mask
);
1424 if (!double_int_minus_one_p (mask
))
1426 val
.lattice_val
= CONSTANT
;
1428 /* ??? Delay building trees here. */
1429 val
.value
= double_int_to_tree (type
, value
);
1433 val
.lattice_val
= VARYING
;
1434 val
.value
= NULL_TREE
;
1435 val
.mask
= double_int_minus_one
;
1440 /* Return the propagation value when applying the operation CODE to
1441 the values RHS1 and RHS2 yielding type TYPE. */
1444 bit_value_binop (enum tree_code code
, tree type
, tree rhs1
, tree rhs2
)
1446 prop_value_t r1val
= get_value_for_expr (rhs1
, true);
1447 prop_value_t r2val
= get_value_for_expr (rhs2
, true);
1448 double_int value
, mask
;
1450 gcc_assert ((r1val
.lattice_val
== CONSTANT
1451 && TREE_CODE (r1val
.value
) == INTEGER_CST
)
1452 || double_int_minus_one_p (r1val
.mask
));
1453 gcc_assert ((r2val
.lattice_val
== CONSTANT
1454 && TREE_CODE (r2val
.value
) == INTEGER_CST
)
1455 || double_int_minus_one_p (r2val
.mask
));
1456 bit_value_binop_1 (code
, type
, &value
, &mask
,
1457 TREE_TYPE (rhs1
), value_to_double_int (r1val
), r1val
.mask
,
1458 TREE_TYPE (rhs2
), value_to_double_int (r2val
), r2val
.mask
);
1459 if (!double_int_minus_one_p (mask
))
1461 val
.lattice_val
= CONSTANT
;
1463 /* ??? Delay building trees here. */
1464 val
.value
= double_int_to_tree (type
, value
);
1468 val
.lattice_val
= VARYING
;
1469 val
.value
= NULL_TREE
;
1470 val
.mask
= double_int_minus_one
;
1475 /* Return the propagation value when applying __builtin_assume_aligned to
1479 bit_value_assume_aligned (gimple stmt
)
1481 tree ptr
= gimple_call_arg (stmt
, 0), align
, misalign
= NULL_TREE
;
1482 tree type
= TREE_TYPE (ptr
);
1483 unsigned HOST_WIDE_INT aligni
, misaligni
= 0;
1484 prop_value_t ptrval
= get_value_for_expr (ptr
, true);
1485 prop_value_t alignval
;
1486 double_int value
, mask
;
1488 if (ptrval
.lattice_val
== UNDEFINED
)
1490 gcc_assert ((ptrval
.lattice_val
== CONSTANT
1491 && TREE_CODE (ptrval
.value
) == INTEGER_CST
)
1492 || double_int_minus_one_p (ptrval
.mask
));
1493 align
= gimple_call_arg (stmt
, 1);
1494 if (!host_integerp (align
, 1))
1496 aligni
= tree_low_cst (align
, 1);
1498 || (aligni
& (aligni
- 1)) != 0)
1500 if (gimple_call_num_args (stmt
) > 2)
1502 misalign
= gimple_call_arg (stmt
, 2);
1503 if (!host_integerp (misalign
, 1))
1505 misaligni
= tree_low_cst (misalign
, 1);
1506 if (misaligni
>= aligni
)
1509 align
= build_int_cst_type (type
, -aligni
);
1510 alignval
= get_value_for_expr (align
, true);
1511 bit_value_binop_1 (BIT_AND_EXPR
, type
, &value
, &mask
,
1512 type
, value_to_double_int (ptrval
), ptrval
.mask
,
1513 type
, value_to_double_int (alignval
), alignval
.mask
);
1514 if (!double_int_minus_one_p (mask
))
1516 val
.lattice_val
= CONSTANT
;
1518 gcc_assert ((mask
.low
& (aligni
- 1)) == 0);
1519 gcc_assert ((value
.low
& (aligni
- 1)) == 0);
1520 value
.low
|= misaligni
;
1521 /* ??? Delay building trees here. */
1522 val
.value
= double_int_to_tree (type
, value
);
1526 val
.lattice_val
= VARYING
;
1527 val
.value
= NULL_TREE
;
1528 val
.mask
= double_int_minus_one
;
1533 /* Evaluate statement STMT.
1534 Valid only for assignments, calls, conditionals, and switches. */
1537 evaluate_stmt (gimple stmt
)
1540 tree simplified
= NULL_TREE
;
1541 ccp_lattice_t likelyvalue
= likely_value (stmt
);
1542 bool is_constant
= false;
1544 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1546 fprintf (dump_file
, "which is likely ");
1547 switch (likelyvalue
)
1550 fprintf (dump_file
, "CONSTANT");
1553 fprintf (dump_file
, "UNDEFINED");
1556 fprintf (dump_file
, "VARYING");
1560 fprintf (dump_file
, "\n");
1563 /* If the statement is likely to have a CONSTANT result, then try
1564 to fold the statement to determine the constant value. */
1565 /* FIXME. This is the only place that we call ccp_fold.
1566 Since likely_value never returns CONSTANT for calls, we will
1567 not attempt to fold them, including builtins that may profit. */
1568 if (likelyvalue
== CONSTANT
)
1570 fold_defer_overflow_warnings ();
1571 simplified
= ccp_fold (stmt
);
1572 is_constant
= simplified
&& is_gimple_min_invariant (simplified
);
1573 fold_undefer_overflow_warnings (is_constant
, stmt
, 0);
1576 /* The statement produced a constant value. */
1577 val
.lattice_val
= CONSTANT
;
1578 val
.value
= simplified
;
1579 val
.mask
= double_int_zero
;
1582 /* If the statement is likely to have a VARYING result, then do not
1583 bother folding the statement. */
1584 else if (likelyvalue
== VARYING
)
1586 enum gimple_code code
= gimple_code (stmt
);
1587 if (code
== GIMPLE_ASSIGN
)
1589 enum tree_code subcode
= gimple_assign_rhs_code (stmt
);
1591 /* Other cases cannot satisfy is_gimple_min_invariant
1593 if (get_gimple_rhs_class (subcode
) == GIMPLE_SINGLE_RHS
)
1594 simplified
= gimple_assign_rhs1 (stmt
);
1596 else if (code
== GIMPLE_SWITCH
)
1597 simplified
= gimple_switch_index (stmt
);
1599 /* These cannot satisfy is_gimple_min_invariant without folding. */
1600 gcc_assert (code
== GIMPLE_CALL
|| code
== GIMPLE_COND
);
1601 is_constant
= simplified
&& is_gimple_min_invariant (simplified
);
1604 /* The statement produced a constant value. */
1605 val
.lattice_val
= CONSTANT
;
1606 val
.value
= simplified
;
1607 val
.mask
= double_int_zero
;
1611 /* Resort to simplification for bitwise tracking. */
1612 if (flag_tree_bit_ccp
1613 && (likelyvalue
== CONSTANT
|| is_gimple_call (stmt
))
1616 enum gimple_code code
= gimple_code (stmt
);
1618 val
.lattice_val
= VARYING
;
1619 val
.value
= NULL_TREE
;
1620 val
.mask
= double_int_minus_one
;
1621 if (code
== GIMPLE_ASSIGN
)
1623 enum tree_code subcode
= gimple_assign_rhs_code (stmt
);
1624 tree rhs1
= gimple_assign_rhs1 (stmt
);
1625 switch (get_gimple_rhs_class (subcode
))
1627 case GIMPLE_SINGLE_RHS
:
1628 if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1
))
1629 || POINTER_TYPE_P (TREE_TYPE (rhs1
)))
1630 val
= get_value_for_expr (rhs1
, true);
1633 case GIMPLE_UNARY_RHS
:
1634 if ((INTEGRAL_TYPE_P (TREE_TYPE (rhs1
))
1635 || POINTER_TYPE_P (TREE_TYPE (rhs1
)))
1636 && (INTEGRAL_TYPE_P (gimple_expr_type (stmt
))
1637 || POINTER_TYPE_P (gimple_expr_type (stmt
))))
1638 val
= bit_value_unop (subcode
, gimple_expr_type (stmt
), rhs1
);
1641 case GIMPLE_BINARY_RHS
:
1642 if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1
))
1643 || POINTER_TYPE_P (TREE_TYPE (rhs1
)))
1645 tree lhs
= gimple_assign_lhs (stmt
);
1646 tree rhs2
= gimple_assign_rhs2 (stmt
);
1647 val
= bit_value_binop (subcode
,
1648 TREE_TYPE (lhs
), rhs1
, rhs2
);
1655 else if (code
== GIMPLE_COND
)
1657 enum tree_code code
= gimple_cond_code (stmt
);
1658 tree rhs1
= gimple_cond_lhs (stmt
);
1659 tree rhs2
= gimple_cond_rhs (stmt
);
1660 if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1
))
1661 || POINTER_TYPE_P (TREE_TYPE (rhs1
)))
1662 val
= bit_value_binop (code
, TREE_TYPE (rhs1
), rhs1
, rhs2
);
1664 else if (code
== GIMPLE_CALL
1665 && (fndecl
= gimple_call_fndecl (stmt
))
1666 && DECL_BUILT_IN_CLASS (fndecl
) == BUILT_IN_NORMAL
)
1668 switch (DECL_FUNCTION_CODE (fndecl
))
1670 case BUILT_IN_MALLOC
:
1671 case BUILT_IN_REALLOC
:
1672 case BUILT_IN_CALLOC
:
1673 case BUILT_IN_STRDUP
:
1674 case BUILT_IN_STRNDUP
:
1675 val
.lattice_val
= CONSTANT
;
1676 val
.value
= build_int_cst (TREE_TYPE (gimple_get_lhs (stmt
)), 0);
1677 val
.mask
= shwi_to_double_int
1678 (~(((HOST_WIDE_INT
) MALLOC_ABI_ALIGNMENT
)
1679 / BITS_PER_UNIT
- 1));
1682 case BUILT_IN_ALLOCA
:
1683 val
.lattice_val
= CONSTANT
;
1684 val
.value
= build_int_cst (TREE_TYPE (gimple_get_lhs (stmt
)), 0);
1685 val
.mask
= shwi_to_double_int
1686 (~(((HOST_WIDE_INT
) BIGGEST_ALIGNMENT
)
1687 / BITS_PER_UNIT
- 1));
1690 /* These builtins return their first argument, unmodified. */
1691 case BUILT_IN_MEMCPY
:
1692 case BUILT_IN_MEMMOVE
:
1693 case BUILT_IN_MEMSET
:
1694 case BUILT_IN_STRCPY
:
1695 case BUILT_IN_STRNCPY
:
1696 case BUILT_IN_MEMCPY_CHK
:
1697 case BUILT_IN_MEMMOVE_CHK
:
1698 case BUILT_IN_MEMSET_CHK
:
1699 case BUILT_IN_STRCPY_CHK
:
1700 case BUILT_IN_STRNCPY_CHK
:
1701 val
= get_value_for_expr (gimple_call_arg (stmt
, 0), true);
1704 case BUILT_IN_ASSUME_ALIGNED
:
1705 val
= bit_value_assume_aligned (stmt
);
1711 is_constant
= (val
.lattice_val
== CONSTANT
);
1716 /* The statement produced a nonconstant value. If the statement
1717 had UNDEFINED operands, then the result of the statement
1718 should be UNDEFINED. Otherwise, the statement is VARYING. */
1719 if (likelyvalue
== UNDEFINED
)
1721 val
.lattice_val
= likelyvalue
;
1722 val
.mask
= double_int_zero
;
1726 val
.lattice_val
= VARYING
;
1727 val
.mask
= double_int_minus_one
;
1730 val
.value
= NULL_TREE
;
1736 /* Fold the stmt at *GSI with CCP specific information that propagating
1737 and regular folding does not catch. */
1740 ccp_fold_stmt (gimple_stmt_iterator
*gsi
)
1742 gimple stmt
= gsi_stmt (*gsi
);
1744 switch (gimple_code (stmt
))
1749 /* Statement evaluation will handle type mismatches in constants
1750 more gracefully than the final propagation. This allows us to
1751 fold more conditionals here. */
1752 val
= evaluate_stmt (stmt
);
1753 if (val
.lattice_val
!= CONSTANT
1754 || !double_int_zero_p (val
.mask
))
1759 fprintf (dump_file
, "Folding predicate ");
1760 print_gimple_expr (dump_file
, stmt
, 0, 0);
1761 fprintf (dump_file
, " to ");
1762 print_generic_expr (dump_file
, val
.value
, 0);
1763 fprintf (dump_file
, "\n");
1766 if (integer_zerop (val
.value
))
1767 gimple_cond_make_false (stmt
);
1769 gimple_cond_make_true (stmt
);
1776 tree lhs
= gimple_call_lhs (stmt
);
1779 bool changed
= false;
1782 /* If the call was folded into a constant make sure it goes
1783 away even if we cannot propagate into all uses because of
1786 && TREE_CODE (lhs
) == SSA_NAME
1787 && (val
= get_constant_value (lhs
)))
1789 tree new_rhs
= unshare_expr (val
);
1791 if (!useless_type_conversion_p (TREE_TYPE (lhs
),
1792 TREE_TYPE (new_rhs
)))
1793 new_rhs
= fold_convert (TREE_TYPE (lhs
), new_rhs
);
1794 res
= update_call_from_tree (gsi
, new_rhs
);
1799 /* Internal calls provide no argument types, so the extra laxity
1800 for normal calls does not apply. */
1801 if (gimple_call_internal_p (stmt
))
1804 /* Propagate into the call arguments. Compared to replace_uses_in
1805 this can use the argument slot types for type verification
1806 instead of the current argument type. We also can safely
1807 drop qualifiers here as we are dealing with constants anyway. */
1808 argt
= TYPE_ARG_TYPES (gimple_call_fntype (stmt
));
1809 for (i
= 0; i
< gimple_call_num_args (stmt
) && argt
;
1810 ++i
, argt
= TREE_CHAIN (argt
))
1812 tree arg
= gimple_call_arg (stmt
, i
);
1813 if (TREE_CODE (arg
) == SSA_NAME
1814 && (val
= get_constant_value (arg
))
1815 && useless_type_conversion_p
1816 (TYPE_MAIN_VARIANT (TREE_VALUE (argt
)),
1817 TYPE_MAIN_VARIANT (TREE_TYPE (val
))))
1819 gimple_call_set_arg (stmt
, i
, unshare_expr (val
));
1829 tree lhs
= gimple_assign_lhs (stmt
);
1832 /* If we have a load that turned out to be constant replace it
1833 as we cannot propagate into all uses in all cases. */
1834 if (gimple_assign_single_p (stmt
)
1835 && TREE_CODE (lhs
) == SSA_NAME
1836 && (val
= get_constant_value (lhs
)))
1838 tree rhs
= unshare_expr (val
);
1839 if (!useless_type_conversion_p (TREE_TYPE (lhs
), TREE_TYPE (rhs
)))
1840 rhs
= fold_build1 (VIEW_CONVERT_EXPR
, TREE_TYPE (lhs
), rhs
);
1841 gimple_assign_set_rhs_from_tree (gsi
, rhs
);
1853 /* Visit the assignment statement STMT. Set the value of its LHS to the
1854 value computed by the RHS and store LHS in *OUTPUT_P. If STMT
1855 creates virtual definitions, set the value of each new name to that
1856 of the RHS (if we can derive a constant out of the RHS).
1857 Value-returning call statements also perform an assignment, and
1858 are handled here. */
1860 static enum ssa_prop_result
1861 visit_assignment (gimple stmt
, tree
*output_p
)
1864 enum ssa_prop_result retval
;
1866 tree lhs
= gimple_get_lhs (stmt
);
1868 gcc_assert (gimple_code (stmt
) != GIMPLE_CALL
1869 || gimple_call_lhs (stmt
) != NULL_TREE
);
1871 if (gimple_assign_single_p (stmt
)
1872 && gimple_assign_rhs_code (stmt
) == SSA_NAME
)
1873 /* For a simple copy operation, we copy the lattice values. */
1874 val
= *get_value (gimple_assign_rhs1 (stmt
));
1876 /* Evaluate the statement, which could be
1877 either a GIMPLE_ASSIGN or a GIMPLE_CALL. */
1878 val
= evaluate_stmt (stmt
);
1880 retval
= SSA_PROP_NOT_INTERESTING
;
1882 /* Set the lattice value of the statement's output. */
1883 if (TREE_CODE (lhs
) == SSA_NAME
)
1885 /* If STMT is an assignment to an SSA_NAME, we only have one
1887 if (set_lattice_value (lhs
, val
))
1890 if (val
.lattice_val
== VARYING
)
1891 retval
= SSA_PROP_VARYING
;
1893 retval
= SSA_PROP_INTERESTING
;
1901 /* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING
1902 if it can determine which edge will be taken. Otherwise, return
1903 SSA_PROP_VARYING. */
1905 static enum ssa_prop_result
1906 visit_cond_stmt (gimple stmt
, edge
*taken_edge_p
)
1911 block
= gimple_bb (stmt
);
1912 val
= evaluate_stmt (stmt
);
1913 if (val
.lattice_val
!= CONSTANT
1914 || !double_int_zero_p (val
.mask
))
1915 return SSA_PROP_VARYING
;
1917 /* Find which edge out of the conditional block will be taken and add it
1918 to the worklist. If no single edge can be determined statically,
1919 return SSA_PROP_VARYING to feed all the outgoing edges to the
1920 propagation engine. */
1921 *taken_edge_p
= find_taken_edge (block
, val
.value
);
1923 return SSA_PROP_INTERESTING
;
1925 return SSA_PROP_VARYING
;
1929 /* Evaluate statement STMT. If the statement produces an output value and
1930 its evaluation changes the lattice value of its output, return
1931 SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the
1934 If STMT is a conditional branch and we can determine its truth
1935 value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying
1936 value, return SSA_PROP_VARYING. */
1938 static enum ssa_prop_result
1939 ccp_visit_stmt (gimple stmt
, edge
*taken_edge_p
, tree
*output_p
)
1944 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1946 fprintf (dump_file
, "\nVisiting statement:\n");
1947 print_gimple_stmt (dump_file
, stmt
, 0, dump_flags
);
1950 switch (gimple_code (stmt
))
1953 /* If the statement is an assignment that produces a single
1954 output value, evaluate its RHS to see if the lattice value of
1955 its output has changed. */
1956 return visit_assignment (stmt
, output_p
);
1959 /* A value-returning call also performs an assignment. */
1960 if (gimple_call_lhs (stmt
) != NULL_TREE
)
1961 return visit_assignment (stmt
, output_p
);
1966 /* If STMT is a conditional branch, see if we can determine
1967 which branch will be taken. */
1968 /* FIXME. It appears that we should be able to optimize
1969 computed GOTOs here as well. */
1970 return visit_cond_stmt (stmt
, taken_edge_p
);
1976 /* Any other kind of statement is not interesting for constant
1977 propagation and, therefore, not worth simulating. */
1978 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1979 fprintf (dump_file
, "No interesting values produced. Marked VARYING.\n");
1981 /* Definitions made by statements other than assignments to
1982 SSA_NAMEs represent unknown modifications to their outputs.
1983 Mark them VARYING. */
1984 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_ALL_DEFS
)
1986 prop_value_t v
= { VARYING
, NULL_TREE
, { -1, (HOST_WIDE_INT
) -1 } };
1987 set_lattice_value (def
, v
);
1990 return SSA_PROP_VARYING
;
1994 /* Main entry point for SSA Conditional Constant Propagation. */
2000 ssa_propagate (ccp_visit_stmt
, ccp_visit_phi_node
);
2001 if (ccp_finalize ())
2002 return (TODO_cleanup_cfg
| TODO_update_ssa
| TODO_remove_unused_locals
);
2011 return flag_tree_ccp
!= 0;
2015 struct gimple_opt_pass pass_ccp
=
2020 gate_ccp
, /* gate */
2021 do_ssa_ccp
, /* execute */
2024 0, /* static_pass_number */
2025 TV_TREE_CCP
, /* tv_id */
2026 PROP_cfg
| PROP_ssa
, /* properties_required */
2027 0, /* properties_provided */
2028 0, /* properties_destroyed */
2029 0, /* todo_flags_start */
2031 | TODO_verify_stmts
| TODO_ggc_collect
/* todo_flags_finish */
2037 /* Try to optimize out __builtin_stack_restore. Optimize it out
2038 if there is another __builtin_stack_restore in the same basic
2039 block and no calls or ASM_EXPRs are in between, or if this block's
2040 only outgoing edge is to EXIT_BLOCK and there are no calls or
2041 ASM_EXPRs after this __builtin_stack_restore. */
2044 optimize_stack_restore (gimple_stmt_iterator i
)
2049 basic_block bb
= gsi_bb (i
);
2050 gimple call
= gsi_stmt (i
);
2052 if (gimple_code (call
) != GIMPLE_CALL
2053 || gimple_call_num_args (call
) != 1
2054 || TREE_CODE (gimple_call_arg (call
, 0)) != SSA_NAME
2055 || !POINTER_TYPE_P (TREE_TYPE (gimple_call_arg (call
, 0))))
2058 for (gsi_next (&i
); !gsi_end_p (i
); gsi_next (&i
))
2060 stmt
= gsi_stmt (i
);
2061 if (gimple_code (stmt
) == GIMPLE_ASM
)
2063 if (gimple_code (stmt
) != GIMPLE_CALL
)
2066 callee
= gimple_call_fndecl (stmt
);
2068 || DECL_BUILT_IN_CLASS (callee
) != BUILT_IN_NORMAL
2069 /* All regular builtins are ok, just obviously not alloca. */
2070 || DECL_FUNCTION_CODE (callee
) == BUILT_IN_ALLOCA
)
2073 if (DECL_FUNCTION_CODE (callee
) == BUILT_IN_STACK_RESTORE
)
2074 goto second_stack_restore
;
2080 /* Allow one successor of the exit block, or zero successors. */
2081 switch (EDGE_COUNT (bb
->succs
))
2086 if (single_succ_edge (bb
)->dest
!= EXIT_BLOCK_PTR
)
2092 second_stack_restore
:
2094 /* If there's exactly one use, then zap the call to __builtin_stack_save.
2095 If there are multiple uses, then the last one should remove the call.
2096 In any case, whether the call to __builtin_stack_save can be removed
2097 or not is irrelevant to removing the call to __builtin_stack_restore. */
2098 if (has_single_use (gimple_call_arg (call
, 0)))
2100 gimple stack_save
= SSA_NAME_DEF_STMT (gimple_call_arg (call
, 0));
2101 if (is_gimple_call (stack_save
))
2103 callee
= gimple_call_fndecl (stack_save
);
2105 && DECL_BUILT_IN_CLASS (callee
) == BUILT_IN_NORMAL
2106 && DECL_FUNCTION_CODE (callee
) == BUILT_IN_STACK_SAVE
)
2108 gimple_stmt_iterator stack_save_gsi
;
2111 stack_save_gsi
= gsi_for_stmt (stack_save
);
2112 rhs
= build_int_cst (TREE_TYPE (gimple_call_arg (call
, 0)), 0);
2113 update_call_from_tree (&stack_save_gsi
, rhs
);
2118 /* No effect, so the statement will be deleted. */
2119 return integer_zero_node
;
2122 /* If va_list type is a simple pointer and nothing special is needed,
2123 optimize __builtin_va_start (&ap, 0) into ap = __builtin_next_arg (0),
2124 __builtin_va_end (&ap) out as NOP and __builtin_va_copy into a simple
2125 pointer assignment. */
2128 optimize_stdarg_builtin (gimple call
)
2130 tree callee
, lhs
, rhs
, cfun_va_list
;
2131 bool va_list_simple_ptr
;
2132 location_t loc
= gimple_location (call
);
2134 if (gimple_code (call
) != GIMPLE_CALL
)
2137 callee
= gimple_call_fndecl (call
);
2139 cfun_va_list
= targetm
.fn_abi_va_list (callee
);
2140 va_list_simple_ptr
= POINTER_TYPE_P (cfun_va_list
)
2141 && (TREE_TYPE (cfun_va_list
) == void_type_node
2142 || TREE_TYPE (cfun_va_list
) == char_type_node
);
2144 switch (DECL_FUNCTION_CODE (callee
))
2146 case BUILT_IN_VA_START
:
2147 if (!va_list_simple_ptr
2148 || targetm
.expand_builtin_va_start
!= NULL
2149 || built_in_decls
[BUILT_IN_NEXT_ARG
] == NULL
)
2152 if (gimple_call_num_args (call
) != 2)
2155 lhs
= gimple_call_arg (call
, 0);
2156 if (!POINTER_TYPE_P (TREE_TYPE (lhs
))
2157 || TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs
)))
2158 != TYPE_MAIN_VARIANT (cfun_va_list
))
2161 lhs
= build_fold_indirect_ref_loc (loc
, lhs
);
2162 rhs
= build_call_expr_loc (loc
, built_in_decls
[BUILT_IN_NEXT_ARG
],
2163 1, integer_zero_node
);
2164 rhs
= fold_convert_loc (loc
, TREE_TYPE (lhs
), rhs
);
2165 return build2 (MODIFY_EXPR
, TREE_TYPE (lhs
), lhs
, rhs
);
2167 case BUILT_IN_VA_COPY
:
2168 if (!va_list_simple_ptr
)
2171 if (gimple_call_num_args (call
) != 2)
2174 lhs
= gimple_call_arg (call
, 0);
2175 if (!POINTER_TYPE_P (TREE_TYPE (lhs
))
2176 || TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs
)))
2177 != TYPE_MAIN_VARIANT (cfun_va_list
))
2180 lhs
= build_fold_indirect_ref_loc (loc
, lhs
);
2181 rhs
= gimple_call_arg (call
, 1);
2182 if (TYPE_MAIN_VARIANT (TREE_TYPE (rhs
))
2183 != TYPE_MAIN_VARIANT (cfun_va_list
))
2186 rhs
= fold_convert_loc (loc
, TREE_TYPE (lhs
), rhs
);
2187 return build2 (MODIFY_EXPR
, TREE_TYPE (lhs
), lhs
, rhs
);
2189 case BUILT_IN_VA_END
:
2190 /* No effect, so the statement will be deleted. */
2191 return integer_zero_node
;
2198 /* A simple pass that attempts to fold all builtin functions. This pass
2199 is run after we've propagated as many constants as we can. */
2202 execute_fold_all_builtins (void)
2204 bool cfg_changed
= false;
2206 unsigned int todoflags
= 0;
2210 gimple_stmt_iterator i
;
2211 for (i
= gsi_start_bb (bb
); !gsi_end_p (i
); )
2213 gimple stmt
, old_stmt
;
2214 tree callee
, result
;
2215 enum built_in_function fcode
;
2217 stmt
= gsi_stmt (i
);
2219 if (gimple_code (stmt
) != GIMPLE_CALL
)
2224 callee
= gimple_call_fndecl (stmt
);
2225 if (!callee
|| DECL_BUILT_IN_CLASS (callee
) != BUILT_IN_NORMAL
)
2230 fcode
= DECL_FUNCTION_CODE (callee
);
2232 result
= gimple_fold_builtin (stmt
);
2235 gimple_remove_stmt_histograms (cfun
, stmt
);
2238 switch (DECL_FUNCTION_CODE (callee
))
2240 case BUILT_IN_CONSTANT_P
:
2241 /* Resolve __builtin_constant_p. If it hasn't been
2242 folded to integer_one_node by now, it's fairly
2243 certain that the value simply isn't constant. */
2244 result
= integer_zero_node
;
2247 case BUILT_IN_ASSUME_ALIGNED
:
2248 /* Remove __builtin_assume_aligned. */
2249 result
= gimple_call_arg (stmt
, 0);
2252 case BUILT_IN_STACK_RESTORE
:
2253 result
= optimize_stack_restore (i
);
2259 case BUILT_IN_VA_START
:
2260 case BUILT_IN_VA_END
:
2261 case BUILT_IN_VA_COPY
:
2262 /* These shouldn't be folded before pass_stdarg. */
2263 result
= optimize_stdarg_builtin (stmt
);
2273 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2275 fprintf (dump_file
, "Simplified\n ");
2276 print_gimple_stmt (dump_file
, stmt
, 0, dump_flags
);
2280 if (!update_call_from_tree (&i
, result
))
2282 gimplify_and_update_call_from_tree (&i
, result
);
2283 todoflags
|= TODO_update_address_taken
;
2286 stmt
= gsi_stmt (i
);
2289 if (maybe_clean_or_replace_eh_stmt (old_stmt
, stmt
)
2290 && gimple_purge_dead_eh_edges (bb
))
2293 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2295 fprintf (dump_file
, "to\n ");
2296 print_gimple_stmt (dump_file
, stmt
, 0, dump_flags
);
2297 fprintf (dump_file
, "\n");
2300 /* Retry the same statement if it changed into another
2301 builtin, there might be new opportunities now. */
2302 if (gimple_code (stmt
) != GIMPLE_CALL
)
2307 callee
= gimple_call_fndecl (stmt
);
2309 || DECL_BUILT_IN_CLASS (callee
) != BUILT_IN_NORMAL
2310 || DECL_FUNCTION_CODE (callee
) == fcode
)
2315 /* Delete unreachable blocks. */
2317 todoflags
|= TODO_cleanup_cfg
;
2323 struct gimple_opt_pass pass_fold_builtins
=
2329 execute_fold_all_builtins
, /* execute */
2332 0, /* static_pass_number */
2333 TV_NONE
, /* tv_id */
2334 PROP_cfg
| PROP_ssa
, /* properties_required */
2335 0, /* properties_provided */
2336 0, /* properties_destroyed */
2337 0, /* todo_flags_start */
2339 | TODO_update_ssa
/* todo_flags_finish */