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1 /* Conditional constant propagation pass for the GNU compiler.
2 Copyright (C) 2000-2014 Free Software Foundation, Inc.
3 Adapted from original RTL SSA-CCP by Daniel Berlin <dberlin@dberlin.org>
4 Adapted to GIMPLE trees by Diego Novillo <dnovillo@redhat.com>
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it
9 under the terms of the GNU General Public License as published by the
10 Free Software Foundation; either version 3, or (at your option) any
11 later version.
13 GCC is distributed in the hope that it will be useful, but WITHOUT
14 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 for more details.
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
22 /* Conditional constant propagation (CCP) is based on the SSA
23 propagation engine (tree-ssa-propagate.c). Constant assignments of
24 the form VAR = CST are propagated from the assignments into uses of
25 VAR, which in turn may generate new constants. The simulation uses
26 a four level lattice to keep track of constant values associated
27 with SSA names. Given an SSA name V_i, it may take one of the
28 following values:
30 UNINITIALIZED -> the initial state of the value. This value
31 is replaced with a correct initial value
32 the first time the value is used, so the
33 rest of the pass does not need to care about
34 it. Using this value simplifies initialization
35 of the pass, and prevents us from needlessly
36 scanning statements that are never reached.
38 UNDEFINED -> V_i is a local variable whose definition
39 has not been processed yet. Therefore we
40 don't yet know if its value is a constant
41 or not.
43 CONSTANT -> V_i has been found to hold a constant
44 value C.
46 VARYING -> V_i cannot take a constant value, or if it
47 does, it is not possible to determine it
48 at compile time.
50 The core of SSA-CCP is in ccp_visit_stmt and ccp_visit_phi_node:
52 1- In ccp_visit_stmt, we are interested in assignments whose RHS
53 evaluates into a constant and conditional jumps whose predicate
54 evaluates into a boolean true or false. When an assignment of
55 the form V_i = CONST is found, V_i's lattice value is set to
56 CONSTANT and CONST is associated with it. This causes the
57 propagation engine to add all the SSA edges coming out the
58 assignment into the worklists, so that statements that use V_i
59 can be visited.
61 If the statement is a conditional with a constant predicate, we
62 mark the outgoing edges as executable or not executable
63 depending on the predicate's value. This is then used when
64 visiting PHI nodes to know when a PHI argument can be ignored.
67 2- In ccp_visit_phi_node, if all the PHI arguments evaluate to the
68 same constant C, then the LHS of the PHI is set to C. This
69 evaluation is known as the "meet operation". Since one of the
70 goals of this evaluation is to optimistically return constant
71 values as often as possible, it uses two main short cuts:
73 - If an argument is flowing in through a non-executable edge, it
74 is ignored. This is useful in cases like this:
76 if (PRED)
77 a_9 = 3;
78 else
79 a_10 = 100;
80 a_11 = PHI (a_9, a_10)
82 If PRED is known to always evaluate to false, then we can
83 assume that a_11 will always take its value from a_10, meaning
84 that instead of consider it VARYING (a_9 and a_10 have
85 different values), we can consider it CONSTANT 100.
87 - If an argument has an UNDEFINED value, then it does not affect
88 the outcome of the meet operation. If a variable V_i has an
89 UNDEFINED value, it means that either its defining statement
90 hasn't been visited yet or V_i has no defining statement, in
91 which case the original symbol 'V' is being used
92 uninitialized. Since 'V' is a local variable, the compiler
93 may assume any initial value for it.
96 After propagation, every variable V_i that ends up with a lattice
97 value of CONSTANT will have the associated constant value in the
98 array CONST_VAL[i].VALUE. That is fed into substitute_and_fold for
99 final substitution and folding.
101 References:
103 Constant propagation with conditional branches,
104 Wegman and Zadeck, ACM TOPLAS 13(2):181-210.
106 Building an Optimizing Compiler,
107 Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9.
109 Advanced Compiler Design and Implementation,
110 Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */
112 #include "config.h"
113 #include "system.h"
114 #include "coretypes.h"
115 #include "tm.h"
116 #include "tree.h"
117 #include "stor-layout.h"
118 #include "flags.h"
119 #include "tm_p.h"
120 #include "basic-block.h"
121 #include "function.h"
122 #include "gimple-pretty-print.h"
123 #include "hash-table.h"
124 #include "tree-ssa-alias.h"
125 #include "internal-fn.h"
126 #include "gimple-fold.h"
127 #include "tree-eh.h"
128 #include "gimple-expr.h"
129 #include "is-a.h"
130 #include "gimple.h"
131 #include "gimplify.h"
132 #include "gimple-iterator.h"
133 #include "gimple-ssa.h"
134 #include "tree-cfg.h"
135 #include "tree-phinodes.h"
136 #include "ssa-iterators.h"
137 #include "stringpool.h"
138 #include "tree-ssanames.h"
139 #include "tree-pass.h"
140 #include "tree-ssa-propagate.h"
141 #include "value-prof.h"
142 #include "langhooks.h"
143 #include "target.h"
144 #include "diagnostic-core.h"
145 #include "dbgcnt.h"
146 #include "params.h"
149 /* Possible lattice values. */
150 typedef enum
152 UNINITIALIZED,
153 UNDEFINED,
154 CONSTANT,
155 VARYING
156 } ccp_lattice_t;
158 struct prop_value_d {
159 /* Lattice value. */
160 ccp_lattice_t lattice_val;
162 /* Propagated value. */
163 tree value;
165 /* Mask that applies to the propagated value during CCP. For
166 X with a CONSTANT lattice value X & ~mask == value & ~mask. */
167 double_int mask;
170 typedef struct prop_value_d prop_value_t;
172 /* Array of propagated constant values. After propagation,
173 CONST_VAL[I].VALUE holds the constant value for SSA_NAME(I). If
174 the constant is held in an SSA name representing a memory store
175 (i.e., a VDEF), CONST_VAL[I].MEM_REF will contain the actual
176 memory reference used to store (i.e., the LHS of the assignment
177 doing the store). */
178 static prop_value_t *const_val;
179 static unsigned n_const_val;
181 static void canonicalize_value (prop_value_t *);
182 static bool ccp_fold_stmt (gimple_stmt_iterator *);
184 /* Dump constant propagation value VAL to file OUTF prefixed by PREFIX. */
186 static void
187 dump_lattice_value (FILE *outf, const char *prefix, prop_value_t val)
189 switch (val.lattice_val)
191 case UNINITIALIZED:
192 fprintf (outf, "%sUNINITIALIZED", prefix);
193 break;
194 case UNDEFINED:
195 fprintf (outf, "%sUNDEFINED", prefix);
196 break;
197 case VARYING:
198 fprintf (outf, "%sVARYING", prefix);
199 break;
200 case CONSTANT:
201 if (TREE_CODE (val.value) != INTEGER_CST
202 || val.mask.is_zero ())
204 fprintf (outf, "%sCONSTANT ", prefix);
205 print_generic_expr (outf, val.value, dump_flags);
207 else
209 double_int cval = tree_to_double_int (val.value).and_not (val.mask);
210 fprintf (outf, "%sCONSTANT " HOST_WIDE_INT_PRINT_DOUBLE_HEX,
211 prefix, cval.high, cval.low);
212 fprintf (outf, " (" HOST_WIDE_INT_PRINT_DOUBLE_HEX ")",
213 val.mask.high, val.mask.low);
215 break;
216 default:
217 gcc_unreachable ();
222 /* Print lattice value VAL to stderr. */
224 void debug_lattice_value (prop_value_t val);
226 DEBUG_FUNCTION void
227 debug_lattice_value (prop_value_t val)
229 dump_lattice_value (stderr, "", val);
230 fprintf (stderr, "\n");
234 /* Compute a default value for variable VAR and store it in the
235 CONST_VAL array. The following rules are used to get default
236 values:
238 1- Global and static variables that are declared constant are
239 considered CONSTANT.
241 2- Any other value is considered UNDEFINED. This is useful when
242 considering PHI nodes. PHI arguments that are undefined do not
243 change the constant value of the PHI node, which allows for more
244 constants to be propagated.
246 3- Variables defined by statements other than assignments and PHI
247 nodes are considered VARYING.
249 4- Initial values of variables that are not GIMPLE registers are
250 considered VARYING. */
252 static prop_value_t
253 get_default_value (tree var)
255 prop_value_t val = { UNINITIALIZED, NULL_TREE, { 0, 0 } };
256 gimple stmt;
258 stmt = SSA_NAME_DEF_STMT (var);
260 if (gimple_nop_p (stmt))
262 /* Variables defined by an empty statement are those used
263 before being initialized. If VAR is a local variable, we
264 can assume initially that it is UNDEFINED, otherwise we must
265 consider it VARYING. */
266 if (!virtual_operand_p (var)
267 && TREE_CODE (SSA_NAME_VAR (var)) == VAR_DECL)
268 val.lattice_val = UNDEFINED;
269 else
271 val.lattice_val = VARYING;
272 val.mask = double_int_minus_one;
273 if (flag_tree_bit_ccp)
275 double_int nonzero_bits = get_nonzero_bits (var);
276 double_int mask
277 = double_int::mask (TYPE_PRECISION (TREE_TYPE (var)));
278 if (nonzero_bits != double_int_minus_one && nonzero_bits != mask)
280 val.lattice_val = CONSTANT;
281 val.value = build_zero_cst (TREE_TYPE (var));
282 /* CCP wants the bits above precision set. */
283 val.mask = nonzero_bits | ~mask;
288 else if (is_gimple_assign (stmt))
290 tree cst;
291 if (gimple_assign_single_p (stmt)
292 && DECL_P (gimple_assign_rhs1 (stmt))
293 && (cst = get_symbol_constant_value (gimple_assign_rhs1 (stmt))))
295 val.lattice_val = CONSTANT;
296 val.value = cst;
298 else
300 /* Any other variable defined by an assignment is considered
301 UNDEFINED. */
302 val.lattice_val = UNDEFINED;
305 else if ((is_gimple_call (stmt)
306 && gimple_call_lhs (stmt) != NULL_TREE)
307 || gimple_code (stmt) == GIMPLE_PHI)
309 /* A variable defined by a call or a PHI node is considered
310 UNDEFINED. */
311 val.lattice_val = UNDEFINED;
313 else
315 /* Otherwise, VAR will never take on a constant value. */
316 val.lattice_val = VARYING;
317 val.mask = double_int_minus_one;
320 return val;
324 /* Get the constant value associated with variable VAR. */
326 static inline prop_value_t *
327 get_value (tree var)
329 prop_value_t *val;
331 if (const_val == NULL
332 || SSA_NAME_VERSION (var) >= n_const_val)
333 return NULL;
335 val = &const_val[SSA_NAME_VERSION (var)];
336 if (val->lattice_val == UNINITIALIZED)
337 *val = get_default_value (var);
339 canonicalize_value (val);
341 return val;
344 /* Return the constant tree value associated with VAR. */
346 static inline tree
347 get_constant_value (tree var)
349 prop_value_t *val;
350 if (TREE_CODE (var) != SSA_NAME)
352 if (is_gimple_min_invariant (var))
353 return var;
354 return NULL_TREE;
356 val = get_value (var);
357 if (val
358 && val->lattice_val == CONSTANT
359 && (TREE_CODE (val->value) != INTEGER_CST
360 || val->mask.is_zero ()))
361 return val->value;
362 return NULL_TREE;
365 /* Sets the value associated with VAR to VARYING. */
367 static inline void
368 set_value_varying (tree var)
370 prop_value_t *val = &const_val[SSA_NAME_VERSION (var)];
372 val->lattice_val = VARYING;
373 val->value = NULL_TREE;
374 val->mask = double_int_minus_one;
377 /* For float types, modify the value of VAL to make ccp work correctly
378 for non-standard values (-0, NaN):
380 If HONOR_SIGNED_ZEROS is false, and VAL = -0, we canonicalize it to 0.
381 If HONOR_NANS is false, and VAL is NaN, we canonicalize it to UNDEFINED.
382 This is to fix the following problem (see PR 29921): Suppose we have
384 x = 0.0 * y
386 and we set value of y to NaN. This causes value of x to be set to NaN.
387 When we later determine that y is in fact VARYING, fold uses the fact
388 that HONOR_NANS is false, and we try to change the value of x to 0,
389 causing an ICE. With HONOR_NANS being false, the real appearance of
390 NaN would cause undefined behavior, though, so claiming that y (and x)
391 are UNDEFINED initially is correct.
393 For other constants, make sure to drop TREE_OVERFLOW. */
395 static void
396 canonicalize_value (prop_value_t *val)
398 enum machine_mode mode;
399 tree type;
400 REAL_VALUE_TYPE d;
402 if (val->lattice_val != CONSTANT)
403 return;
405 if (TREE_OVERFLOW_P (val->value))
406 val->value = drop_tree_overflow (val->value);
408 if (TREE_CODE (val->value) != REAL_CST)
409 return;
411 d = TREE_REAL_CST (val->value);
412 type = TREE_TYPE (val->value);
413 mode = TYPE_MODE (type);
415 if (!HONOR_SIGNED_ZEROS (mode)
416 && REAL_VALUE_MINUS_ZERO (d))
418 val->value = build_real (type, dconst0);
419 return;
422 if (!HONOR_NANS (mode)
423 && REAL_VALUE_ISNAN (d))
425 val->lattice_val = UNDEFINED;
426 val->value = NULL;
427 return;
431 /* Return whether the lattice transition is valid. */
433 static bool
434 valid_lattice_transition (prop_value_t old_val, prop_value_t new_val)
436 /* Lattice transitions must always be monotonically increasing in
437 value. */
438 if (old_val.lattice_val < new_val.lattice_val)
439 return true;
441 if (old_val.lattice_val != new_val.lattice_val)
442 return false;
444 if (!old_val.value && !new_val.value)
445 return true;
447 /* Now both lattice values are CONSTANT. */
449 /* Allow transitioning from PHI <&x, not executable> == &x
450 to PHI <&x, &y> == common alignment. */
451 if (TREE_CODE (old_val.value) != INTEGER_CST
452 && TREE_CODE (new_val.value) == INTEGER_CST)
453 return true;
455 /* Bit-lattices have to agree in the still valid bits. */
456 if (TREE_CODE (old_val.value) == INTEGER_CST
457 && TREE_CODE (new_val.value) == INTEGER_CST)
458 return tree_to_double_int (old_val.value).and_not (new_val.mask)
459 == tree_to_double_int (new_val.value).and_not (new_val.mask);
461 /* Otherwise constant values have to agree. */
462 return operand_equal_p (old_val.value, new_val.value, 0);
465 /* Set the value for variable VAR to NEW_VAL. Return true if the new
466 value is different from VAR's previous value. */
468 static bool
469 set_lattice_value (tree var, prop_value_t new_val)
471 /* We can deal with old UNINITIALIZED values just fine here. */
472 prop_value_t *old_val = &const_val[SSA_NAME_VERSION (var)];
474 canonicalize_value (&new_val);
476 /* We have to be careful to not go up the bitwise lattice
477 represented by the mask.
478 ??? This doesn't seem to be the best place to enforce this. */
479 if (new_val.lattice_val == CONSTANT
480 && old_val->lattice_val == CONSTANT
481 && TREE_CODE (new_val.value) == INTEGER_CST
482 && TREE_CODE (old_val->value) == INTEGER_CST)
484 double_int diff;
485 diff = tree_to_double_int (new_val.value)
486 ^ tree_to_double_int (old_val->value);
487 new_val.mask = new_val.mask | old_val->mask | diff;
490 gcc_assert (valid_lattice_transition (*old_val, new_val));
492 /* If *OLD_VAL and NEW_VAL are the same, return false to inform the
493 caller that this was a non-transition. */
494 if (old_val->lattice_val != new_val.lattice_val
495 || (new_val.lattice_val == CONSTANT
496 && TREE_CODE (new_val.value) == INTEGER_CST
497 && (TREE_CODE (old_val->value) != INTEGER_CST
498 || new_val.mask != old_val->mask)))
500 /* ??? We would like to delay creation of INTEGER_CSTs from
501 partially constants here. */
503 if (dump_file && (dump_flags & TDF_DETAILS))
505 dump_lattice_value (dump_file, "Lattice value changed to ", new_val);
506 fprintf (dump_file, ". Adding SSA edges to worklist.\n");
509 *old_val = new_val;
511 gcc_assert (new_val.lattice_val != UNINITIALIZED);
512 return true;
515 return false;
518 static prop_value_t get_value_for_expr (tree, bool);
519 static prop_value_t bit_value_binop (enum tree_code, tree, tree, tree);
520 static void bit_value_binop_1 (enum tree_code, tree, double_int *, double_int *,
521 tree, double_int, double_int,
522 tree, double_int, double_int);
524 /* Return a double_int that can be used for bitwise simplifications
525 from VAL. */
527 static double_int
528 value_to_double_int (prop_value_t val)
530 if (val.value
531 && TREE_CODE (val.value) == INTEGER_CST)
532 return tree_to_double_int (val.value);
533 else
534 return double_int_zero;
537 /* Return the value for the address expression EXPR based on alignment
538 information. */
540 static prop_value_t
541 get_value_from_alignment (tree expr)
543 tree type = TREE_TYPE (expr);
544 prop_value_t val;
545 unsigned HOST_WIDE_INT bitpos;
546 unsigned int align;
548 gcc_assert (TREE_CODE (expr) == ADDR_EXPR);
550 get_pointer_alignment_1 (expr, &align, &bitpos);
551 val.mask = (POINTER_TYPE_P (type) || TYPE_UNSIGNED (type)
552 ? double_int::mask (TYPE_PRECISION (type))
553 : double_int_minus_one)
554 .and_not (double_int::from_uhwi (align / BITS_PER_UNIT - 1));
555 val.lattice_val = val.mask.is_minus_one () ? VARYING : CONSTANT;
556 if (val.lattice_val == CONSTANT)
557 val.value
558 = double_int_to_tree (type,
559 double_int::from_uhwi (bitpos / BITS_PER_UNIT));
560 else
561 val.value = NULL_TREE;
563 return val;
566 /* Return the value for the tree operand EXPR. If FOR_BITS_P is true
567 return constant bits extracted from alignment information for
568 invariant addresses. */
570 static prop_value_t
571 get_value_for_expr (tree expr, bool for_bits_p)
573 prop_value_t val;
575 if (TREE_CODE (expr) == SSA_NAME)
577 val = *get_value (expr);
578 if (for_bits_p
579 && val.lattice_val == CONSTANT
580 && TREE_CODE (val.value) == ADDR_EXPR)
581 val = get_value_from_alignment (val.value);
583 else if (is_gimple_min_invariant (expr)
584 && (!for_bits_p || TREE_CODE (expr) != ADDR_EXPR))
586 val.lattice_val = CONSTANT;
587 val.value = expr;
588 val.mask = double_int_zero;
589 canonicalize_value (&val);
591 else if (TREE_CODE (expr) == ADDR_EXPR)
592 val = get_value_from_alignment (expr);
593 else
595 val.lattice_val = VARYING;
596 val.mask = double_int_minus_one;
597 val.value = NULL_TREE;
599 return val;
602 /* Return the likely CCP lattice value for STMT.
604 If STMT has no operands, then return CONSTANT.
606 Else if undefinedness of operands of STMT cause its value to be
607 undefined, then return UNDEFINED.
609 Else if any operands of STMT are constants, then return CONSTANT.
611 Else return VARYING. */
613 static ccp_lattice_t
614 likely_value (gimple stmt)
616 bool has_constant_operand, has_undefined_operand, all_undefined_operands;
617 tree use;
618 ssa_op_iter iter;
619 unsigned i;
621 enum gimple_code code = gimple_code (stmt);
623 /* This function appears to be called only for assignments, calls,
624 conditionals, and switches, due to the logic in visit_stmt. */
625 gcc_assert (code == GIMPLE_ASSIGN
626 || code == GIMPLE_CALL
627 || code == GIMPLE_COND
628 || code == GIMPLE_SWITCH);
630 /* If the statement has volatile operands, it won't fold to a
631 constant value. */
632 if (gimple_has_volatile_ops (stmt))
633 return VARYING;
635 /* Arrive here for more complex cases. */
636 has_constant_operand = false;
637 has_undefined_operand = false;
638 all_undefined_operands = true;
639 FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
641 prop_value_t *val = get_value (use);
643 if (val->lattice_val == UNDEFINED)
644 has_undefined_operand = true;
645 else
646 all_undefined_operands = false;
648 if (val->lattice_val == CONSTANT)
649 has_constant_operand = true;
652 /* There may be constants in regular rhs operands. For calls we
653 have to ignore lhs, fndecl and static chain, otherwise only
654 the lhs. */
655 for (i = (is_gimple_call (stmt) ? 2 : 0) + gimple_has_lhs (stmt);
656 i < gimple_num_ops (stmt); ++i)
658 tree op = gimple_op (stmt, i);
659 if (!op || TREE_CODE (op) == SSA_NAME)
660 continue;
661 if (is_gimple_min_invariant (op))
662 has_constant_operand = true;
665 if (has_constant_operand)
666 all_undefined_operands = false;
668 if (has_undefined_operand
669 && code == GIMPLE_CALL
670 && gimple_call_internal_p (stmt))
671 switch (gimple_call_internal_fn (stmt))
673 /* These 3 builtins use the first argument just as a magic
674 way how to find out a decl uid. */
675 case IFN_GOMP_SIMD_LANE:
676 case IFN_GOMP_SIMD_VF:
677 case IFN_GOMP_SIMD_LAST_LANE:
678 has_undefined_operand = false;
679 break;
680 default:
681 break;
684 /* If the operation combines operands like COMPLEX_EXPR make sure to
685 not mark the result UNDEFINED if only one part of the result is
686 undefined. */
687 if (has_undefined_operand && all_undefined_operands)
688 return UNDEFINED;
689 else if (code == GIMPLE_ASSIGN && has_undefined_operand)
691 switch (gimple_assign_rhs_code (stmt))
693 /* Unary operators are handled with all_undefined_operands. */
694 case PLUS_EXPR:
695 case MINUS_EXPR:
696 case POINTER_PLUS_EXPR:
697 /* Not MIN_EXPR, MAX_EXPR. One VARYING operand may be selected.
698 Not bitwise operators, one VARYING operand may specify the
699 result completely. Not logical operators for the same reason.
700 Not COMPLEX_EXPR as one VARYING operand makes the result partly
701 not UNDEFINED. Not *DIV_EXPR, comparisons and shifts because
702 the undefined operand may be promoted. */
703 return UNDEFINED;
705 case ADDR_EXPR:
706 /* If any part of an address is UNDEFINED, like the index
707 of an ARRAY_EXPR, then treat the result as UNDEFINED. */
708 return UNDEFINED;
710 default:
714 /* If there was an UNDEFINED operand but the result may be not UNDEFINED
715 fall back to CONSTANT. During iteration UNDEFINED may still drop
716 to CONSTANT. */
717 if (has_undefined_operand)
718 return CONSTANT;
720 /* We do not consider virtual operands here -- load from read-only
721 memory may have only VARYING virtual operands, but still be
722 constant. */
723 if (has_constant_operand
724 || gimple_references_memory_p (stmt))
725 return CONSTANT;
727 return VARYING;
730 /* Returns true if STMT cannot be constant. */
732 static bool
733 surely_varying_stmt_p (gimple stmt)
735 /* If the statement has operands that we cannot handle, it cannot be
736 constant. */
737 if (gimple_has_volatile_ops (stmt))
738 return true;
740 /* If it is a call and does not return a value or is not a
741 builtin and not an indirect call, it is varying. */
742 if (is_gimple_call (stmt))
744 tree fndecl;
745 if (!gimple_call_lhs (stmt)
746 || ((fndecl = gimple_call_fndecl (stmt)) != NULL_TREE
747 && !DECL_BUILT_IN (fndecl)))
748 return true;
751 /* Any other store operation is not interesting. */
752 else if (gimple_vdef (stmt))
753 return true;
755 /* Anything other than assignments and conditional jumps are not
756 interesting for CCP. */
757 if (gimple_code (stmt) != GIMPLE_ASSIGN
758 && gimple_code (stmt) != GIMPLE_COND
759 && gimple_code (stmt) != GIMPLE_SWITCH
760 && gimple_code (stmt) != GIMPLE_CALL)
761 return true;
763 return false;
766 /* Initialize local data structures for CCP. */
768 static void
769 ccp_initialize (void)
771 basic_block bb;
773 n_const_val = num_ssa_names;
774 const_val = XCNEWVEC (prop_value_t, n_const_val);
776 /* Initialize simulation flags for PHI nodes and statements. */
777 FOR_EACH_BB_FN (bb, cfun)
779 gimple_stmt_iterator i;
781 for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
783 gimple stmt = gsi_stmt (i);
784 bool is_varying;
786 /* If the statement is a control insn, then we do not
787 want to avoid simulating the statement once. Failure
788 to do so means that those edges will never get added. */
789 if (stmt_ends_bb_p (stmt))
790 is_varying = false;
791 else
792 is_varying = surely_varying_stmt_p (stmt);
794 if (is_varying)
796 tree def;
797 ssa_op_iter iter;
799 /* If the statement will not produce a constant, mark
800 all its outputs VARYING. */
801 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
802 set_value_varying (def);
804 prop_set_simulate_again (stmt, !is_varying);
808 /* Now process PHI nodes. We never clear the simulate_again flag on
809 phi nodes, since we do not know which edges are executable yet,
810 except for phi nodes for virtual operands when we do not do store ccp. */
811 FOR_EACH_BB_FN (bb, cfun)
813 gimple_stmt_iterator i;
815 for (i = gsi_start_phis (bb); !gsi_end_p (i); gsi_next (&i))
817 gimple phi = gsi_stmt (i);
819 if (virtual_operand_p (gimple_phi_result (phi)))
820 prop_set_simulate_again (phi, false);
821 else
822 prop_set_simulate_again (phi, true);
827 /* Debug count support. Reset the values of ssa names
828 VARYING when the total number ssa names analyzed is
829 beyond the debug count specified. */
831 static void
832 do_dbg_cnt (void)
834 unsigned i;
835 for (i = 0; i < num_ssa_names; i++)
837 if (!dbg_cnt (ccp))
839 const_val[i].lattice_val = VARYING;
840 const_val[i].mask = double_int_minus_one;
841 const_val[i].value = NULL_TREE;
847 /* Do final substitution of propagated values, cleanup the flowgraph and
848 free allocated storage.
850 Return TRUE when something was optimized. */
852 static bool
853 ccp_finalize (void)
855 bool something_changed;
856 unsigned i;
858 do_dbg_cnt ();
860 /* Derive alignment and misalignment information from partially
861 constant pointers in the lattice or nonzero bits from partially
862 constant integers. */
863 for (i = 1; i < num_ssa_names; ++i)
865 tree name = ssa_name (i);
866 prop_value_t *val;
867 unsigned int tem, align;
869 if (!name
870 || (!POINTER_TYPE_P (TREE_TYPE (name))
871 && (!INTEGRAL_TYPE_P (TREE_TYPE (name))
872 /* Don't record nonzero bits before IPA to avoid
873 using too much memory. */
874 || first_pass_instance)))
875 continue;
877 val = get_value (name);
878 if (val->lattice_val != CONSTANT
879 || TREE_CODE (val->value) != INTEGER_CST)
880 continue;
882 if (POINTER_TYPE_P (TREE_TYPE (name)))
884 /* Trailing mask bits specify the alignment, trailing value
885 bits the misalignment. */
886 tem = val->mask.low;
887 align = (tem & -tem);
888 if (align > 1)
889 set_ptr_info_alignment (get_ptr_info (name), align,
890 (TREE_INT_CST_LOW (val->value)
891 & (align - 1)));
893 else
895 double_int nonzero_bits = val->mask;
896 nonzero_bits = nonzero_bits | tree_to_double_int (val->value);
897 nonzero_bits &= get_nonzero_bits (name);
898 set_nonzero_bits (name, nonzero_bits);
902 /* Perform substitutions based on the known constant values. */
903 something_changed = substitute_and_fold (get_constant_value,
904 ccp_fold_stmt, true);
906 free (const_val);
907 const_val = NULL;
908 return something_changed;;
912 /* Compute the meet operator between *VAL1 and *VAL2. Store the result
913 in VAL1.
915 any M UNDEFINED = any
916 any M VARYING = VARYING
917 Ci M Cj = Ci if (i == j)
918 Ci M Cj = VARYING if (i != j)
921 static void
922 ccp_lattice_meet (prop_value_t *val1, prop_value_t *val2)
924 if (val1->lattice_val == UNDEFINED)
926 /* UNDEFINED M any = any */
927 *val1 = *val2;
929 else if (val2->lattice_val == UNDEFINED)
931 /* any M UNDEFINED = any
932 Nothing to do. VAL1 already contains the value we want. */
935 else if (val1->lattice_val == VARYING
936 || val2->lattice_val == VARYING)
938 /* any M VARYING = VARYING. */
939 val1->lattice_val = VARYING;
940 val1->mask = double_int_minus_one;
941 val1->value = NULL_TREE;
943 else if (val1->lattice_val == CONSTANT
944 && val2->lattice_val == CONSTANT
945 && TREE_CODE (val1->value) == INTEGER_CST
946 && TREE_CODE (val2->value) == INTEGER_CST)
948 /* Ci M Cj = Ci if (i == j)
949 Ci M Cj = VARYING if (i != j)
951 For INTEGER_CSTs mask unequal bits. If no equal bits remain,
952 drop to varying. */
953 val1->mask = val1->mask | val2->mask
954 | (tree_to_double_int (val1->value)
955 ^ tree_to_double_int (val2->value));
956 if (val1->mask.is_minus_one ())
958 val1->lattice_val = VARYING;
959 val1->value = NULL_TREE;
962 else if (val1->lattice_val == CONSTANT
963 && val2->lattice_val == CONSTANT
964 && simple_cst_equal (val1->value, val2->value) == 1)
966 /* Ci M Cj = Ci if (i == j)
967 Ci M Cj = VARYING if (i != j)
969 VAL1 already contains the value we want for equivalent values. */
971 else if (val1->lattice_val == CONSTANT
972 && val2->lattice_val == CONSTANT
973 && (TREE_CODE (val1->value) == ADDR_EXPR
974 || TREE_CODE (val2->value) == ADDR_EXPR))
976 /* When not equal addresses are involved try meeting for
977 alignment. */
978 prop_value_t tem = *val2;
979 if (TREE_CODE (val1->value) == ADDR_EXPR)
980 *val1 = get_value_for_expr (val1->value, true);
981 if (TREE_CODE (val2->value) == ADDR_EXPR)
982 tem = get_value_for_expr (val2->value, true);
983 ccp_lattice_meet (val1, &tem);
985 else
987 /* Any other combination is VARYING. */
988 val1->lattice_val = VARYING;
989 val1->mask = double_int_minus_one;
990 val1->value = NULL_TREE;
995 /* Loop through the PHI_NODE's parameters for BLOCK and compare their
996 lattice values to determine PHI_NODE's lattice value. The value of a
997 PHI node is determined calling ccp_lattice_meet with all the arguments
998 of the PHI node that are incoming via executable edges. */
1000 static enum ssa_prop_result
1001 ccp_visit_phi_node (gimple phi)
1003 unsigned i;
1004 prop_value_t *old_val, new_val;
1006 if (dump_file && (dump_flags & TDF_DETAILS))
1008 fprintf (dump_file, "\nVisiting PHI node: ");
1009 print_gimple_stmt (dump_file, phi, 0, dump_flags);
1012 old_val = get_value (gimple_phi_result (phi));
1013 switch (old_val->lattice_val)
1015 case VARYING:
1016 return SSA_PROP_VARYING;
1018 case CONSTANT:
1019 new_val = *old_val;
1020 break;
1022 case UNDEFINED:
1023 new_val.lattice_val = UNDEFINED;
1024 new_val.value = NULL_TREE;
1025 break;
1027 default:
1028 gcc_unreachable ();
1031 for (i = 0; i < gimple_phi_num_args (phi); i++)
1033 /* Compute the meet operator over all the PHI arguments flowing
1034 through executable edges. */
1035 edge e = gimple_phi_arg_edge (phi, i);
1037 if (dump_file && (dump_flags & TDF_DETAILS))
1039 fprintf (dump_file,
1040 "\n Argument #%d (%d -> %d %sexecutable)\n",
1041 i, e->src->index, e->dest->index,
1042 (e->flags & EDGE_EXECUTABLE) ? "" : "not ");
1045 /* If the incoming edge is executable, Compute the meet operator for
1046 the existing value of the PHI node and the current PHI argument. */
1047 if (e->flags & EDGE_EXECUTABLE)
1049 tree arg = gimple_phi_arg (phi, i)->def;
1050 prop_value_t arg_val = get_value_for_expr (arg, false);
1052 ccp_lattice_meet (&new_val, &arg_val);
1054 if (dump_file && (dump_flags & TDF_DETAILS))
1056 fprintf (dump_file, "\t");
1057 print_generic_expr (dump_file, arg, dump_flags);
1058 dump_lattice_value (dump_file, "\tValue: ", arg_val);
1059 fprintf (dump_file, "\n");
1062 if (new_val.lattice_val == VARYING)
1063 break;
1067 if (dump_file && (dump_flags & TDF_DETAILS))
1069 dump_lattice_value (dump_file, "\n PHI node value: ", new_val);
1070 fprintf (dump_file, "\n\n");
1073 /* Make the transition to the new value. */
1074 if (set_lattice_value (gimple_phi_result (phi), new_val))
1076 if (new_val.lattice_val == VARYING)
1077 return SSA_PROP_VARYING;
1078 else
1079 return SSA_PROP_INTERESTING;
1081 else
1082 return SSA_PROP_NOT_INTERESTING;
1085 /* Return the constant value for OP or OP otherwise. */
1087 static tree
1088 valueize_op (tree op)
1090 if (TREE_CODE (op) == SSA_NAME)
1092 tree tem = get_constant_value (op);
1093 if (tem)
1094 return tem;
1096 return op;
1099 /* CCP specific front-end to the non-destructive constant folding
1100 routines.
1102 Attempt to simplify the RHS of STMT knowing that one or more
1103 operands are constants.
1105 If simplification is possible, return the simplified RHS,
1106 otherwise return the original RHS or NULL_TREE. */
1108 static tree
1109 ccp_fold (gimple stmt)
1111 location_t loc = gimple_location (stmt);
1112 switch (gimple_code (stmt))
1114 case GIMPLE_COND:
1116 /* Handle comparison operators that can appear in GIMPLE form. */
1117 tree op0 = valueize_op (gimple_cond_lhs (stmt));
1118 tree op1 = valueize_op (gimple_cond_rhs (stmt));
1119 enum tree_code code = gimple_cond_code (stmt);
1120 return fold_binary_loc (loc, code, boolean_type_node, op0, op1);
1123 case GIMPLE_SWITCH:
1125 /* Return the constant switch index. */
1126 return valueize_op (gimple_switch_index (stmt));
1129 case GIMPLE_ASSIGN:
1130 case GIMPLE_CALL:
1131 return gimple_fold_stmt_to_constant_1 (stmt, valueize_op);
1133 default:
1134 gcc_unreachable ();
1138 /* Apply the operation CODE in type TYPE to the value, mask pair
1139 RVAL and RMASK representing a value of type RTYPE and set
1140 the value, mask pair *VAL and *MASK to the result. */
1142 static void
1143 bit_value_unop_1 (enum tree_code code, tree type,
1144 double_int *val, double_int *mask,
1145 tree rtype, double_int rval, double_int rmask)
1147 switch (code)
1149 case BIT_NOT_EXPR:
1150 *mask = rmask;
1151 *val = ~rval;
1152 break;
1154 case NEGATE_EXPR:
1156 double_int temv, temm;
1157 /* Return ~rval + 1. */
1158 bit_value_unop_1 (BIT_NOT_EXPR, type, &temv, &temm, type, rval, rmask);
1159 bit_value_binop_1 (PLUS_EXPR, type, val, mask,
1160 type, temv, temm,
1161 type, double_int_one, double_int_zero);
1162 break;
1165 CASE_CONVERT:
1167 bool uns;
1169 /* First extend mask and value according to the original type. */
1170 uns = TYPE_UNSIGNED (rtype);
1171 *mask = rmask.ext (TYPE_PRECISION (rtype), uns);
1172 *val = rval.ext (TYPE_PRECISION (rtype), uns);
1174 /* Then extend mask and value according to the target type. */
1175 uns = TYPE_UNSIGNED (type);
1176 *mask = (*mask).ext (TYPE_PRECISION (type), uns);
1177 *val = (*val).ext (TYPE_PRECISION (type), uns);
1178 break;
1181 default:
1182 *mask = double_int_minus_one;
1183 break;
1187 /* Apply the operation CODE in type TYPE to the value, mask pairs
1188 R1VAL, R1MASK and R2VAL, R2MASK representing a values of type R1TYPE
1189 and R2TYPE and set the value, mask pair *VAL and *MASK to the result. */
1191 static void
1192 bit_value_binop_1 (enum tree_code code, tree type,
1193 double_int *val, double_int *mask,
1194 tree r1type, double_int r1val, double_int r1mask,
1195 tree r2type, double_int r2val, double_int r2mask)
1197 bool uns = TYPE_UNSIGNED (type);
1198 /* Assume we'll get a constant result. Use an initial varying value,
1199 we fall back to varying in the end if necessary. */
1200 *mask = double_int_minus_one;
1201 switch (code)
1203 case BIT_AND_EXPR:
1204 /* The mask is constant where there is a known not
1205 set bit, (m1 | m2) & ((v1 | m1) & (v2 | m2)) */
1206 *mask = (r1mask | r2mask) & (r1val | r1mask) & (r2val | r2mask);
1207 *val = r1val & r2val;
1208 break;
1210 case BIT_IOR_EXPR:
1211 /* The mask is constant where there is a known
1212 set bit, (m1 | m2) & ~((v1 & ~m1) | (v2 & ~m2)). */
1213 *mask = (r1mask | r2mask)
1214 .and_not (r1val.and_not (r1mask) | r2val.and_not (r2mask));
1215 *val = r1val | r2val;
1216 break;
1218 case BIT_XOR_EXPR:
1219 /* m1 | m2 */
1220 *mask = r1mask | r2mask;
1221 *val = r1val ^ r2val;
1222 break;
1224 case LROTATE_EXPR:
1225 case RROTATE_EXPR:
1226 if (r2mask.is_zero ())
1228 HOST_WIDE_INT shift = r2val.low;
1229 if (code == RROTATE_EXPR)
1230 shift = -shift;
1231 *mask = r1mask.lrotate (shift, TYPE_PRECISION (type));
1232 *val = r1val.lrotate (shift, TYPE_PRECISION (type));
1234 break;
1236 case LSHIFT_EXPR:
1237 case RSHIFT_EXPR:
1238 /* ??? We can handle partially known shift counts if we know
1239 its sign. That way we can tell that (x << (y | 8)) & 255
1240 is zero. */
1241 if (r2mask.is_zero ())
1243 HOST_WIDE_INT shift = r2val.low;
1244 if (code == RSHIFT_EXPR)
1245 shift = -shift;
1246 /* We need to know if we are doing a left or a right shift
1247 to properly shift in zeros for left shift and unsigned
1248 right shifts and the sign bit for signed right shifts.
1249 For signed right shifts we shift in varying in case
1250 the sign bit was varying. */
1251 if (shift > 0)
1253 *mask = r1mask.llshift (shift, TYPE_PRECISION (type));
1254 *val = r1val.llshift (shift, TYPE_PRECISION (type));
1256 else if (shift < 0)
1258 shift = -shift;
1259 *mask = r1mask.rshift (shift, TYPE_PRECISION (type), !uns);
1260 *val = r1val.rshift (shift, TYPE_PRECISION (type), !uns);
1262 else
1264 *mask = r1mask;
1265 *val = r1val;
1268 break;
1270 case PLUS_EXPR:
1271 case POINTER_PLUS_EXPR:
1273 double_int lo, hi;
1274 /* Do the addition with unknown bits set to zero, to give carry-ins of
1275 zero wherever possible. */
1276 lo = r1val.and_not (r1mask) + r2val.and_not (r2mask);
1277 lo = lo.ext (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 = (r1val | r1mask) + (r2val | r2mask);
1281 hi = hi.ext (TYPE_PRECISION (type), uns);
1282 /* Each bit in the result is known if (a) the corresponding bits in
1283 both inputs are known, and (b) the carry-in to that bit position
1284 is known. We can check condition (b) by seeing if we got the same
1285 result with minimised carries as with maximised carries. */
1286 *mask = r1mask | r2mask | (lo ^ hi);
1287 *mask = (*mask).ext (TYPE_PRECISION (type), uns);
1288 /* It shouldn't matter whether we choose lo or hi here. */
1289 *val = lo;
1290 break;
1293 case MINUS_EXPR:
1295 double_int temv, temm;
1296 bit_value_unop_1 (NEGATE_EXPR, r2type, &temv, &temm,
1297 r2type, r2val, r2mask);
1298 bit_value_binop_1 (PLUS_EXPR, type, val, mask,
1299 r1type, r1val, r1mask,
1300 r2type, temv, temm);
1301 break;
1304 case MULT_EXPR:
1306 /* Just track trailing zeros in both operands and transfer
1307 them to the other. */
1308 int r1tz = (r1val | r1mask).trailing_zeros ();
1309 int r2tz = (r2val | r2mask).trailing_zeros ();
1310 if (r1tz + r2tz >= HOST_BITS_PER_DOUBLE_INT)
1312 *mask = double_int_zero;
1313 *val = double_int_zero;
1315 else if (r1tz + r2tz > 0)
1317 *mask = ~double_int::mask (r1tz + r2tz);
1318 *mask = (*mask).ext (TYPE_PRECISION (type), uns);
1319 *val = double_int_zero;
1321 break;
1324 case EQ_EXPR:
1325 case NE_EXPR:
1327 double_int m = r1mask | r2mask;
1328 if (r1val.and_not (m) != r2val.and_not (m))
1330 *mask = double_int_zero;
1331 *val = ((code == EQ_EXPR) ? double_int_zero : double_int_one);
1333 else
1335 /* We know the result of a comparison is always one or zero. */
1336 *mask = double_int_one;
1337 *val = double_int_zero;
1339 break;
1342 case GE_EXPR:
1343 case GT_EXPR:
1345 double_int tem = r1val;
1346 r1val = r2val;
1347 r2val = tem;
1348 tem = r1mask;
1349 r1mask = r2mask;
1350 r2mask = tem;
1351 code = swap_tree_comparison (code);
1353 /* Fallthru. */
1354 case LT_EXPR:
1355 case LE_EXPR:
1357 int minmax, maxmin;
1358 /* If the most significant bits are not known we know nothing. */
1359 if (r1mask.is_negative () || r2mask.is_negative ())
1360 break;
1362 /* For comparisons the signedness is in the comparison operands. */
1363 uns = TYPE_UNSIGNED (r1type);
1365 /* If we know the most significant bits we know the values
1366 value ranges by means of treating varying bits as zero
1367 or one. Do a cross comparison of the max/min pairs. */
1368 maxmin = (r1val | r1mask).cmp (r2val.and_not (r2mask), uns);
1369 minmax = r1val.and_not (r1mask).cmp (r2val | r2mask, uns);
1370 if (maxmin < 0) /* r1 is less than r2. */
1372 *mask = double_int_zero;
1373 *val = double_int_one;
1375 else if (minmax > 0) /* r1 is not less or equal to r2. */
1377 *mask = double_int_zero;
1378 *val = double_int_zero;
1380 else if (maxmin == minmax) /* r1 and r2 are equal. */
1382 /* This probably should never happen as we'd have
1383 folded the thing during fully constant value folding. */
1384 *mask = double_int_zero;
1385 *val = (code == LE_EXPR ? double_int_one : double_int_zero);
1387 else
1389 /* We know the result of a comparison is always one or zero. */
1390 *mask = double_int_one;
1391 *val = double_int_zero;
1393 break;
1396 default:;
1400 /* Return the propagation value when applying the operation CODE to
1401 the value RHS yielding type TYPE. */
1403 static prop_value_t
1404 bit_value_unop (enum tree_code code, tree type, tree rhs)
1406 prop_value_t rval = get_value_for_expr (rhs, true);
1407 double_int value, mask;
1408 prop_value_t val;
1410 if (rval.lattice_val == UNDEFINED)
1411 return rval;
1413 gcc_assert ((rval.lattice_val == CONSTANT
1414 && TREE_CODE (rval.value) == INTEGER_CST)
1415 || rval.mask.is_minus_one ());
1416 bit_value_unop_1 (code, type, &value, &mask,
1417 TREE_TYPE (rhs), value_to_double_int (rval), rval.mask);
1418 if (!mask.is_minus_one ())
1420 val.lattice_val = CONSTANT;
1421 val.mask = mask;
1422 /* ??? Delay building trees here. */
1423 val.value = double_int_to_tree (type, value);
1425 else
1427 val.lattice_val = VARYING;
1428 val.value = NULL_TREE;
1429 val.mask = double_int_minus_one;
1431 return val;
1434 /* Return the propagation value when applying the operation CODE to
1435 the values RHS1 and RHS2 yielding type TYPE. */
1437 static prop_value_t
1438 bit_value_binop (enum tree_code code, tree type, tree rhs1, tree rhs2)
1440 prop_value_t r1val = get_value_for_expr (rhs1, true);
1441 prop_value_t r2val = get_value_for_expr (rhs2, true);
1442 double_int value, mask;
1443 prop_value_t val;
1445 if (r1val.lattice_val == UNDEFINED
1446 || r2val.lattice_val == UNDEFINED)
1448 val.lattice_val = VARYING;
1449 val.value = NULL_TREE;
1450 val.mask = double_int_minus_one;
1451 return val;
1454 gcc_assert ((r1val.lattice_val == CONSTANT
1455 && TREE_CODE (r1val.value) == INTEGER_CST)
1456 || r1val.mask.is_minus_one ());
1457 gcc_assert ((r2val.lattice_val == CONSTANT
1458 && TREE_CODE (r2val.value) == INTEGER_CST)
1459 || r2val.mask.is_minus_one ());
1460 bit_value_binop_1 (code, type, &value, &mask,
1461 TREE_TYPE (rhs1), value_to_double_int (r1val), r1val.mask,
1462 TREE_TYPE (rhs2), value_to_double_int (r2val), r2val.mask);
1463 if (!mask.is_minus_one ())
1465 val.lattice_val = CONSTANT;
1466 val.mask = mask;
1467 /* ??? Delay building trees here. */
1468 val.value = double_int_to_tree (type, value);
1470 else
1472 val.lattice_val = VARYING;
1473 val.value = NULL_TREE;
1474 val.mask = double_int_minus_one;
1476 return val;
1479 /* Return the propagation value when applying __builtin_assume_aligned to
1480 its arguments. */
1482 static prop_value_t
1483 bit_value_assume_aligned (gimple stmt)
1485 tree ptr = gimple_call_arg (stmt, 0), align, misalign = NULL_TREE;
1486 tree type = TREE_TYPE (ptr);
1487 unsigned HOST_WIDE_INT aligni, misaligni = 0;
1488 prop_value_t ptrval = get_value_for_expr (ptr, true);
1489 prop_value_t alignval;
1490 double_int value, mask;
1491 prop_value_t val;
1492 if (ptrval.lattice_val == UNDEFINED)
1493 return ptrval;
1494 gcc_assert ((ptrval.lattice_val == CONSTANT
1495 && TREE_CODE (ptrval.value) == INTEGER_CST)
1496 || ptrval.mask.is_minus_one ());
1497 align = gimple_call_arg (stmt, 1);
1498 if (!tree_fits_uhwi_p (align))
1499 return ptrval;
1500 aligni = tree_to_uhwi (align);
1501 if (aligni <= 1
1502 || (aligni & (aligni - 1)) != 0)
1503 return ptrval;
1504 if (gimple_call_num_args (stmt) > 2)
1506 misalign = gimple_call_arg (stmt, 2);
1507 if (!tree_fits_uhwi_p (misalign))
1508 return ptrval;
1509 misaligni = tree_to_uhwi (misalign);
1510 if (misaligni >= aligni)
1511 return ptrval;
1513 align = build_int_cst_type (type, -aligni);
1514 alignval = get_value_for_expr (align, true);
1515 bit_value_binop_1 (BIT_AND_EXPR, type, &value, &mask,
1516 type, value_to_double_int (ptrval), ptrval.mask,
1517 type, value_to_double_int (alignval), alignval.mask);
1518 if (!mask.is_minus_one ())
1520 val.lattice_val = CONSTANT;
1521 val.mask = mask;
1522 gcc_assert ((mask.low & (aligni - 1)) == 0);
1523 gcc_assert ((value.low & (aligni - 1)) == 0);
1524 value.low |= misaligni;
1525 /* ??? Delay building trees here. */
1526 val.value = double_int_to_tree (type, value);
1528 else
1530 val.lattice_val = VARYING;
1531 val.value = NULL_TREE;
1532 val.mask = double_int_minus_one;
1534 return val;
1537 /* Evaluate statement STMT.
1538 Valid only for assignments, calls, conditionals, and switches. */
1540 static prop_value_t
1541 evaluate_stmt (gimple stmt)
1543 prop_value_t val;
1544 tree simplified = NULL_TREE;
1545 ccp_lattice_t likelyvalue = likely_value (stmt);
1546 bool is_constant = false;
1547 unsigned int align;
1549 if (dump_file && (dump_flags & TDF_DETAILS))
1551 fprintf (dump_file, "which is likely ");
1552 switch (likelyvalue)
1554 case CONSTANT:
1555 fprintf (dump_file, "CONSTANT");
1556 break;
1557 case UNDEFINED:
1558 fprintf (dump_file, "UNDEFINED");
1559 break;
1560 case VARYING:
1561 fprintf (dump_file, "VARYING");
1562 break;
1563 default:;
1565 fprintf (dump_file, "\n");
1568 /* If the statement is likely to have a CONSTANT result, then try
1569 to fold the statement to determine the constant value. */
1570 /* FIXME. This is the only place that we call ccp_fold.
1571 Since likely_value never returns CONSTANT for calls, we will
1572 not attempt to fold them, including builtins that may profit. */
1573 if (likelyvalue == CONSTANT)
1575 fold_defer_overflow_warnings ();
1576 simplified = ccp_fold (stmt);
1577 is_constant = simplified && is_gimple_min_invariant (simplified);
1578 fold_undefer_overflow_warnings (is_constant, stmt, 0);
1579 if (is_constant)
1581 /* The statement produced a constant value. */
1582 val.lattice_val = CONSTANT;
1583 val.value = simplified;
1584 val.mask = double_int_zero;
1587 /* If the statement is likely to have a VARYING result, then do not
1588 bother folding the statement. */
1589 else if (likelyvalue == VARYING)
1591 enum gimple_code code = gimple_code (stmt);
1592 if (code == GIMPLE_ASSIGN)
1594 enum tree_code subcode = gimple_assign_rhs_code (stmt);
1596 /* Other cases cannot satisfy is_gimple_min_invariant
1597 without folding. */
1598 if (get_gimple_rhs_class (subcode) == GIMPLE_SINGLE_RHS)
1599 simplified = gimple_assign_rhs1 (stmt);
1601 else if (code == GIMPLE_SWITCH)
1602 simplified = gimple_switch_index (stmt);
1603 else
1604 /* These cannot satisfy is_gimple_min_invariant without folding. */
1605 gcc_assert (code == GIMPLE_CALL || code == GIMPLE_COND);
1606 is_constant = simplified && is_gimple_min_invariant (simplified);
1607 if (is_constant)
1609 /* The statement produced a constant value. */
1610 val.lattice_val = CONSTANT;
1611 val.value = simplified;
1612 val.mask = double_int_zero;
1616 /* Resort to simplification for bitwise tracking. */
1617 if (flag_tree_bit_ccp
1618 && (likelyvalue == CONSTANT || is_gimple_call (stmt))
1619 && !is_constant)
1621 enum gimple_code code = gimple_code (stmt);
1622 val.lattice_val = VARYING;
1623 val.value = NULL_TREE;
1624 val.mask = double_int_minus_one;
1625 if (code == GIMPLE_ASSIGN)
1627 enum tree_code subcode = gimple_assign_rhs_code (stmt);
1628 tree rhs1 = gimple_assign_rhs1 (stmt);
1629 switch (get_gimple_rhs_class (subcode))
1631 case GIMPLE_SINGLE_RHS:
1632 if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
1633 || POINTER_TYPE_P (TREE_TYPE (rhs1)))
1634 val = get_value_for_expr (rhs1, true);
1635 break;
1637 case GIMPLE_UNARY_RHS:
1638 if ((INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
1639 || POINTER_TYPE_P (TREE_TYPE (rhs1)))
1640 && (INTEGRAL_TYPE_P (gimple_expr_type (stmt))
1641 || POINTER_TYPE_P (gimple_expr_type (stmt))))
1642 val = bit_value_unop (subcode, gimple_expr_type (stmt), rhs1);
1643 break;
1645 case GIMPLE_BINARY_RHS:
1646 if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
1647 || POINTER_TYPE_P (TREE_TYPE (rhs1)))
1649 tree lhs = gimple_assign_lhs (stmt);
1650 tree rhs2 = gimple_assign_rhs2 (stmt);
1651 val = bit_value_binop (subcode,
1652 TREE_TYPE (lhs), rhs1, rhs2);
1654 break;
1656 default:;
1659 else if (code == GIMPLE_COND)
1661 enum tree_code code = gimple_cond_code (stmt);
1662 tree rhs1 = gimple_cond_lhs (stmt);
1663 tree rhs2 = gimple_cond_rhs (stmt);
1664 if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
1665 || POINTER_TYPE_P (TREE_TYPE (rhs1)))
1666 val = bit_value_binop (code, TREE_TYPE (rhs1), rhs1, rhs2);
1668 else if (gimple_call_builtin_p (stmt, BUILT_IN_NORMAL))
1670 tree fndecl = gimple_call_fndecl (stmt);
1671 switch (DECL_FUNCTION_CODE (fndecl))
1673 case BUILT_IN_MALLOC:
1674 case BUILT_IN_REALLOC:
1675 case BUILT_IN_CALLOC:
1676 case BUILT_IN_STRDUP:
1677 case BUILT_IN_STRNDUP:
1678 val.lattice_val = CONSTANT;
1679 val.value = build_int_cst (TREE_TYPE (gimple_get_lhs (stmt)), 0);
1680 val.mask = double_int::from_shwi
1681 (~(((HOST_WIDE_INT) MALLOC_ABI_ALIGNMENT)
1682 / BITS_PER_UNIT - 1));
1683 break;
1685 case BUILT_IN_ALLOCA:
1686 case BUILT_IN_ALLOCA_WITH_ALIGN:
1687 align = (DECL_FUNCTION_CODE (fndecl) == BUILT_IN_ALLOCA_WITH_ALIGN
1688 ? TREE_INT_CST_LOW (gimple_call_arg (stmt, 1))
1689 : BIGGEST_ALIGNMENT);
1690 val.lattice_val = CONSTANT;
1691 val.value = build_int_cst (TREE_TYPE (gimple_get_lhs (stmt)), 0);
1692 val.mask = double_int::from_shwi (~(((HOST_WIDE_INT) align)
1693 / BITS_PER_UNIT - 1));
1694 break;
1696 /* These builtins return their first argument, unmodified. */
1697 case BUILT_IN_MEMCPY:
1698 case BUILT_IN_MEMMOVE:
1699 case BUILT_IN_MEMSET:
1700 case BUILT_IN_STRCPY:
1701 case BUILT_IN_STRNCPY:
1702 case BUILT_IN_MEMCPY_CHK:
1703 case BUILT_IN_MEMMOVE_CHK:
1704 case BUILT_IN_MEMSET_CHK:
1705 case BUILT_IN_STRCPY_CHK:
1706 case BUILT_IN_STRNCPY_CHK:
1707 val = get_value_for_expr (gimple_call_arg (stmt, 0), true);
1708 break;
1710 case BUILT_IN_ASSUME_ALIGNED:
1711 val = bit_value_assume_aligned (stmt);
1712 break;
1714 default:;
1717 is_constant = (val.lattice_val == CONSTANT);
1720 if (flag_tree_bit_ccp
1721 && ((is_constant && TREE_CODE (val.value) == INTEGER_CST)
1722 || (!is_constant && likelyvalue != UNDEFINED))
1723 && gimple_get_lhs (stmt)
1724 && TREE_CODE (gimple_get_lhs (stmt)) == SSA_NAME)
1726 tree lhs = gimple_get_lhs (stmt);
1727 double_int nonzero_bits = get_nonzero_bits (lhs);
1728 double_int mask = double_int::mask (TYPE_PRECISION (TREE_TYPE (lhs)));
1729 if (nonzero_bits != double_int_minus_one && nonzero_bits != mask)
1731 if (!is_constant)
1733 val.lattice_val = CONSTANT;
1734 val.value = build_zero_cst (TREE_TYPE (lhs));
1735 /* CCP wants the bits above precision set. */
1736 val.mask = nonzero_bits | ~mask;
1737 is_constant = true;
1739 else
1741 double_int valv = tree_to_double_int (val.value);
1742 if (!(valv & ~nonzero_bits & mask).is_zero ())
1743 val.value = double_int_to_tree (TREE_TYPE (lhs),
1744 valv & nonzero_bits);
1745 if (nonzero_bits.is_zero ())
1746 val.mask = double_int_zero;
1747 else
1748 val.mask = val.mask & (nonzero_bits | ~mask);
1753 if (!is_constant)
1755 /* The statement produced a nonconstant value. If the statement
1756 had UNDEFINED operands, then the result of the statement
1757 should be UNDEFINED. Otherwise, the statement is VARYING. */
1758 if (likelyvalue == UNDEFINED)
1760 val.lattice_val = likelyvalue;
1761 val.mask = double_int_zero;
1763 else
1765 val.lattice_val = VARYING;
1766 val.mask = double_int_minus_one;
1769 val.value = NULL_TREE;
1772 return val;
1775 typedef hash_table <pointer_hash <gimple_statement_base> > gimple_htab;
1777 /* Given a BUILT_IN_STACK_SAVE value SAVED_VAL, insert a clobber of VAR before
1778 each matching BUILT_IN_STACK_RESTORE. Mark visited phis in VISITED. */
1780 static void
1781 insert_clobber_before_stack_restore (tree saved_val, tree var,
1782 gimple_htab *visited)
1784 gimple stmt, clobber_stmt;
1785 tree clobber;
1786 imm_use_iterator iter;
1787 gimple_stmt_iterator i;
1788 gimple *slot;
1790 FOR_EACH_IMM_USE_STMT (stmt, iter, saved_val)
1791 if (gimple_call_builtin_p (stmt, BUILT_IN_STACK_RESTORE))
1793 clobber = build_constructor (TREE_TYPE (var),
1794 NULL);
1795 TREE_THIS_VOLATILE (clobber) = 1;
1796 clobber_stmt = gimple_build_assign (var, clobber);
1798 i = gsi_for_stmt (stmt);
1799 gsi_insert_before (&i, clobber_stmt, GSI_SAME_STMT);
1801 else if (gimple_code (stmt) == GIMPLE_PHI)
1803 if (!visited->is_created ())
1804 visited->create (10);
1806 slot = visited->find_slot (stmt, INSERT);
1807 if (*slot != NULL)
1808 continue;
1810 *slot = stmt;
1811 insert_clobber_before_stack_restore (gimple_phi_result (stmt), var,
1812 visited);
1814 else if (gimple_assign_ssa_name_copy_p (stmt))
1815 insert_clobber_before_stack_restore (gimple_assign_lhs (stmt), var,
1816 visited);
1817 else
1818 gcc_assert (is_gimple_debug (stmt));
1821 /* Advance the iterator to the previous non-debug gimple statement in the same
1822 or dominating basic block. */
1824 static inline void
1825 gsi_prev_dom_bb_nondebug (gimple_stmt_iterator *i)
1827 basic_block dom;
1829 gsi_prev_nondebug (i);
1830 while (gsi_end_p (*i))
1832 dom = get_immediate_dominator (CDI_DOMINATORS, i->bb);
1833 if (dom == NULL || dom == ENTRY_BLOCK_PTR_FOR_FN (cfun))
1834 return;
1836 *i = gsi_last_bb (dom);
1840 /* Find a BUILT_IN_STACK_SAVE dominating gsi_stmt (I), and insert
1841 a clobber of VAR before each matching BUILT_IN_STACK_RESTORE.
1843 It is possible that BUILT_IN_STACK_SAVE cannot be find in a dominator when a
1844 previous pass (such as DOM) duplicated it along multiple paths to a BB. In
1845 that case the function gives up without inserting the clobbers. */
1847 static void
1848 insert_clobbers_for_var (gimple_stmt_iterator i, tree var)
1850 gimple stmt;
1851 tree saved_val;
1852 gimple_htab visited;
1854 for (; !gsi_end_p (i); gsi_prev_dom_bb_nondebug (&i))
1856 stmt = gsi_stmt (i);
1858 if (!gimple_call_builtin_p (stmt, BUILT_IN_STACK_SAVE))
1859 continue;
1861 saved_val = gimple_call_lhs (stmt);
1862 if (saved_val == NULL_TREE)
1863 continue;
1865 insert_clobber_before_stack_restore (saved_val, var, &visited);
1866 break;
1869 if (visited.is_created ())
1870 visited.dispose ();
1873 /* Detects a __builtin_alloca_with_align with constant size argument. Declares
1874 fixed-size array and returns the address, if found, otherwise returns
1875 NULL_TREE. */
1877 static tree
1878 fold_builtin_alloca_with_align (gimple stmt)
1880 unsigned HOST_WIDE_INT size, threshold, n_elem;
1881 tree lhs, arg, block, var, elem_type, array_type;
1883 /* Get lhs. */
1884 lhs = gimple_call_lhs (stmt);
1885 if (lhs == NULL_TREE)
1886 return NULL_TREE;
1888 /* Detect constant argument. */
1889 arg = get_constant_value (gimple_call_arg (stmt, 0));
1890 if (arg == NULL_TREE
1891 || TREE_CODE (arg) != INTEGER_CST
1892 || !tree_fits_uhwi_p (arg))
1893 return NULL_TREE;
1895 size = tree_to_uhwi (arg);
1897 /* Heuristic: don't fold large allocas. */
1898 threshold = (unsigned HOST_WIDE_INT)PARAM_VALUE (PARAM_LARGE_STACK_FRAME);
1899 /* In case the alloca is located at function entry, it has the same lifetime
1900 as a declared array, so we allow a larger size. */
1901 block = gimple_block (stmt);
1902 if (!(cfun->after_inlining
1903 && TREE_CODE (BLOCK_SUPERCONTEXT (block)) == FUNCTION_DECL))
1904 threshold /= 10;
1905 if (size > threshold)
1906 return NULL_TREE;
1908 /* Declare array. */
1909 elem_type = build_nonstandard_integer_type (BITS_PER_UNIT, 1);
1910 n_elem = size * 8 / BITS_PER_UNIT;
1911 array_type = build_array_type_nelts (elem_type, n_elem);
1912 var = create_tmp_var (array_type, NULL);
1913 DECL_ALIGN (var) = TREE_INT_CST_LOW (gimple_call_arg (stmt, 1));
1915 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (lhs);
1916 if (pi != NULL && !pi->pt.anything)
1918 bool singleton_p;
1919 unsigned uid;
1920 singleton_p = pt_solution_singleton_p (&pi->pt, &uid);
1921 gcc_assert (singleton_p);
1922 SET_DECL_PT_UID (var, uid);
1926 /* Fold alloca to the address of the array. */
1927 return fold_convert (TREE_TYPE (lhs), build_fold_addr_expr (var));
1930 /* Fold the stmt at *GSI with CCP specific information that propagating
1931 and regular folding does not catch. */
1933 static bool
1934 ccp_fold_stmt (gimple_stmt_iterator *gsi)
1936 gimple stmt = gsi_stmt (*gsi);
1938 switch (gimple_code (stmt))
1940 case GIMPLE_COND:
1942 prop_value_t val;
1943 /* Statement evaluation will handle type mismatches in constants
1944 more gracefully than the final propagation. This allows us to
1945 fold more conditionals here. */
1946 val = evaluate_stmt (stmt);
1947 if (val.lattice_val != CONSTANT
1948 || !val.mask.is_zero ())
1949 return false;
1951 if (dump_file)
1953 fprintf (dump_file, "Folding predicate ");
1954 print_gimple_expr (dump_file, stmt, 0, 0);
1955 fprintf (dump_file, " to ");
1956 print_generic_expr (dump_file, val.value, 0);
1957 fprintf (dump_file, "\n");
1960 if (integer_zerop (val.value))
1961 gimple_cond_make_false (stmt);
1962 else
1963 gimple_cond_make_true (stmt);
1965 return true;
1968 case GIMPLE_CALL:
1970 tree lhs = gimple_call_lhs (stmt);
1971 int flags = gimple_call_flags (stmt);
1972 tree val;
1973 tree argt;
1974 bool changed = false;
1975 unsigned i;
1977 /* If the call was folded into a constant make sure it goes
1978 away even if we cannot propagate into all uses because of
1979 type issues. */
1980 if (lhs
1981 && TREE_CODE (lhs) == SSA_NAME
1982 && (val = get_constant_value (lhs))
1983 /* Don't optimize away calls that have side-effects. */
1984 && (flags & (ECF_CONST|ECF_PURE)) != 0
1985 && (flags & ECF_LOOPING_CONST_OR_PURE) == 0)
1987 tree new_rhs = unshare_expr (val);
1988 bool res;
1989 if (!useless_type_conversion_p (TREE_TYPE (lhs),
1990 TREE_TYPE (new_rhs)))
1991 new_rhs = fold_convert (TREE_TYPE (lhs), new_rhs);
1992 res = update_call_from_tree (gsi, new_rhs);
1993 gcc_assert (res);
1994 return true;
1997 /* Internal calls provide no argument types, so the extra laxity
1998 for normal calls does not apply. */
1999 if (gimple_call_internal_p (stmt))
2000 return false;
2002 /* The heuristic of fold_builtin_alloca_with_align differs before and
2003 after inlining, so we don't require the arg to be changed into a
2004 constant for folding, but just to be constant. */
2005 if (gimple_call_builtin_p (stmt, BUILT_IN_ALLOCA_WITH_ALIGN))
2007 tree new_rhs = fold_builtin_alloca_with_align (stmt);
2008 if (new_rhs)
2010 bool res = update_call_from_tree (gsi, new_rhs);
2011 tree var = TREE_OPERAND (TREE_OPERAND (new_rhs, 0),0);
2012 gcc_assert (res);
2013 insert_clobbers_for_var (*gsi, var);
2014 return true;
2018 /* Propagate into the call arguments. Compared to replace_uses_in
2019 this can use the argument slot types for type verification
2020 instead of the current argument type. We also can safely
2021 drop qualifiers here as we are dealing with constants anyway. */
2022 argt = TYPE_ARG_TYPES (gimple_call_fntype (stmt));
2023 for (i = 0; i < gimple_call_num_args (stmt) && argt;
2024 ++i, argt = TREE_CHAIN (argt))
2026 tree arg = gimple_call_arg (stmt, i);
2027 if (TREE_CODE (arg) == SSA_NAME
2028 && (val = get_constant_value (arg))
2029 && useless_type_conversion_p
2030 (TYPE_MAIN_VARIANT (TREE_VALUE (argt)),
2031 TYPE_MAIN_VARIANT (TREE_TYPE (val))))
2033 gimple_call_set_arg (stmt, i, unshare_expr (val));
2034 changed = true;
2038 return changed;
2041 case GIMPLE_ASSIGN:
2043 tree lhs = gimple_assign_lhs (stmt);
2044 tree val;
2046 /* If we have a load that turned out to be constant replace it
2047 as we cannot propagate into all uses in all cases. */
2048 if (gimple_assign_single_p (stmt)
2049 && TREE_CODE (lhs) == SSA_NAME
2050 && (val = get_constant_value (lhs)))
2052 tree rhs = unshare_expr (val);
2053 if (!useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (rhs)))
2054 rhs = fold_build1 (VIEW_CONVERT_EXPR, TREE_TYPE (lhs), rhs);
2055 gimple_assign_set_rhs_from_tree (gsi, rhs);
2056 return true;
2059 return false;
2062 default:
2063 return false;
2067 /* Visit the assignment statement STMT. Set the value of its LHS to the
2068 value computed by the RHS and store LHS in *OUTPUT_P. If STMT
2069 creates virtual definitions, set the value of each new name to that
2070 of the RHS (if we can derive a constant out of the RHS).
2071 Value-returning call statements also perform an assignment, and
2072 are handled here. */
2074 static enum ssa_prop_result
2075 visit_assignment (gimple stmt, tree *output_p)
2077 prop_value_t val;
2078 enum ssa_prop_result retval;
2080 tree lhs = gimple_get_lhs (stmt);
2082 gcc_assert (gimple_code (stmt) != GIMPLE_CALL
2083 || gimple_call_lhs (stmt) != NULL_TREE);
2085 if (gimple_assign_single_p (stmt)
2086 && gimple_assign_rhs_code (stmt) == SSA_NAME)
2087 /* For a simple copy operation, we copy the lattice values. */
2088 val = *get_value (gimple_assign_rhs1 (stmt));
2089 else
2090 /* Evaluate the statement, which could be
2091 either a GIMPLE_ASSIGN or a GIMPLE_CALL. */
2092 val = evaluate_stmt (stmt);
2094 retval = SSA_PROP_NOT_INTERESTING;
2096 /* Set the lattice value of the statement's output. */
2097 if (TREE_CODE (lhs) == SSA_NAME)
2099 /* If STMT is an assignment to an SSA_NAME, we only have one
2100 value to set. */
2101 if (set_lattice_value (lhs, val))
2103 *output_p = lhs;
2104 if (val.lattice_val == VARYING)
2105 retval = SSA_PROP_VARYING;
2106 else
2107 retval = SSA_PROP_INTERESTING;
2111 return retval;
2115 /* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING
2116 if it can determine which edge will be taken. Otherwise, return
2117 SSA_PROP_VARYING. */
2119 static enum ssa_prop_result
2120 visit_cond_stmt (gimple stmt, edge *taken_edge_p)
2122 prop_value_t val;
2123 basic_block block;
2125 block = gimple_bb (stmt);
2126 val = evaluate_stmt (stmt);
2127 if (val.lattice_val != CONSTANT
2128 || !val.mask.is_zero ())
2129 return SSA_PROP_VARYING;
2131 /* Find which edge out of the conditional block will be taken and add it
2132 to the worklist. If no single edge can be determined statically,
2133 return SSA_PROP_VARYING to feed all the outgoing edges to the
2134 propagation engine. */
2135 *taken_edge_p = find_taken_edge (block, val.value);
2136 if (*taken_edge_p)
2137 return SSA_PROP_INTERESTING;
2138 else
2139 return SSA_PROP_VARYING;
2143 /* Evaluate statement STMT. If the statement produces an output value and
2144 its evaluation changes the lattice value of its output, return
2145 SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the
2146 output value.
2148 If STMT is a conditional branch and we can determine its truth
2149 value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying
2150 value, return SSA_PROP_VARYING. */
2152 static enum ssa_prop_result
2153 ccp_visit_stmt (gimple stmt, edge *taken_edge_p, tree *output_p)
2155 tree def;
2156 ssa_op_iter iter;
2158 if (dump_file && (dump_flags & TDF_DETAILS))
2160 fprintf (dump_file, "\nVisiting statement:\n");
2161 print_gimple_stmt (dump_file, stmt, 0, dump_flags);
2164 switch (gimple_code (stmt))
2166 case GIMPLE_ASSIGN:
2167 /* If the statement is an assignment that produces a single
2168 output value, evaluate its RHS to see if the lattice value of
2169 its output has changed. */
2170 return visit_assignment (stmt, output_p);
2172 case GIMPLE_CALL:
2173 /* A value-returning call also performs an assignment. */
2174 if (gimple_call_lhs (stmt) != NULL_TREE)
2175 return visit_assignment (stmt, output_p);
2176 break;
2178 case GIMPLE_COND:
2179 case GIMPLE_SWITCH:
2180 /* If STMT is a conditional branch, see if we can determine
2181 which branch will be taken. */
2182 /* FIXME. It appears that we should be able to optimize
2183 computed GOTOs here as well. */
2184 return visit_cond_stmt (stmt, taken_edge_p);
2186 default:
2187 break;
2190 /* Any other kind of statement is not interesting for constant
2191 propagation and, therefore, not worth simulating. */
2192 if (dump_file && (dump_flags & TDF_DETAILS))
2193 fprintf (dump_file, "No interesting values produced. Marked VARYING.\n");
2195 /* Definitions made by statements other than assignments to
2196 SSA_NAMEs represent unknown modifications to their outputs.
2197 Mark them VARYING. */
2198 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
2200 prop_value_t v = { VARYING, NULL_TREE, { -1, (HOST_WIDE_INT) -1 } };
2201 set_lattice_value (def, v);
2204 return SSA_PROP_VARYING;
2208 /* Main entry point for SSA Conditional Constant Propagation. */
2210 static unsigned int
2211 do_ssa_ccp (void)
2213 unsigned int todo = 0;
2214 calculate_dominance_info (CDI_DOMINATORS);
2215 ccp_initialize ();
2216 ssa_propagate (ccp_visit_stmt, ccp_visit_phi_node);
2217 if (ccp_finalize ())
2218 todo = (TODO_cleanup_cfg | TODO_update_ssa);
2219 free_dominance_info (CDI_DOMINATORS);
2220 return todo;
2224 static bool
2225 gate_ccp (void)
2227 return flag_tree_ccp != 0;
2231 namespace {
2233 const pass_data pass_data_ccp =
2235 GIMPLE_PASS, /* type */
2236 "ccp", /* name */
2237 OPTGROUP_NONE, /* optinfo_flags */
2238 true, /* has_gate */
2239 true, /* has_execute */
2240 TV_TREE_CCP, /* tv_id */
2241 ( PROP_cfg | PROP_ssa ), /* properties_required */
2242 0, /* properties_provided */
2243 0, /* properties_destroyed */
2244 0, /* todo_flags_start */
2245 ( TODO_verify_ssa | TODO_update_address_taken
2246 | TODO_verify_stmts ), /* todo_flags_finish */
2249 class pass_ccp : public gimple_opt_pass
2251 public:
2252 pass_ccp (gcc::context *ctxt)
2253 : gimple_opt_pass (pass_data_ccp, ctxt)
2256 /* opt_pass methods: */
2257 opt_pass * clone () { return new pass_ccp (m_ctxt); }
2258 bool gate () { return gate_ccp (); }
2259 unsigned int execute () { return do_ssa_ccp (); }
2261 }; // class pass_ccp
2263 } // anon namespace
2265 gimple_opt_pass *
2266 make_pass_ccp (gcc::context *ctxt)
2268 return new pass_ccp (ctxt);
2273 /* Try to optimize out __builtin_stack_restore. Optimize it out
2274 if there is another __builtin_stack_restore in the same basic
2275 block and no calls or ASM_EXPRs are in between, or if this block's
2276 only outgoing edge is to EXIT_BLOCK and there are no calls or
2277 ASM_EXPRs after this __builtin_stack_restore. */
2279 static tree
2280 optimize_stack_restore (gimple_stmt_iterator i)
2282 tree callee;
2283 gimple stmt;
2285 basic_block bb = gsi_bb (i);
2286 gimple call = gsi_stmt (i);
2288 if (gimple_code (call) != GIMPLE_CALL
2289 || gimple_call_num_args (call) != 1
2290 || TREE_CODE (gimple_call_arg (call, 0)) != SSA_NAME
2291 || !POINTER_TYPE_P (TREE_TYPE (gimple_call_arg (call, 0))))
2292 return NULL_TREE;
2294 for (gsi_next (&i); !gsi_end_p (i); gsi_next (&i))
2296 stmt = gsi_stmt (i);
2297 if (gimple_code (stmt) == GIMPLE_ASM)
2298 return NULL_TREE;
2299 if (gimple_code (stmt) != GIMPLE_CALL)
2300 continue;
2302 callee = gimple_call_fndecl (stmt);
2303 if (!callee
2304 || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL
2305 /* All regular builtins are ok, just obviously not alloca. */
2306 || DECL_FUNCTION_CODE (callee) == BUILT_IN_ALLOCA
2307 || DECL_FUNCTION_CODE (callee) == BUILT_IN_ALLOCA_WITH_ALIGN)
2308 return NULL_TREE;
2310 if (DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_RESTORE)
2311 goto second_stack_restore;
2314 if (!gsi_end_p (i))
2315 return NULL_TREE;
2317 /* Allow one successor of the exit block, or zero successors. */
2318 switch (EDGE_COUNT (bb->succs))
2320 case 0:
2321 break;
2322 case 1:
2323 if (single_succ_edge (bb)->dest != EXIT_BLOCK_PTR_FOR_FN (cfun))
2324 return NULL_TREE;
2325 break;
2326 default:
2327 return NULL_TREE;
2329 second_stack_restore:
2331 /* If there's exactly one use, then zap the call to __builtin_stack_save.
2332 If there are multiple uses, then the last one should remove the call.
2333 In any case, whether the call to __builtin_stack_save can be removed
2334 or not is irrelevant to removing the call to __builtin_stack_restore. */
2335 if (has_single_use (gimple_call_arg (call, 0)))
2337 gimple stack_save = SSA_NAME_DEF_STMT (gimple_call_arg (call, 0));
2338 if (is_gimple_call (stack_save))
2340 callee = gimple_call_fndecl (stack_save);
2341 if (callee
2342 && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL
2343 && DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_SAVE)
2345 gimple_stmt_iterator stack_save_gsi;
2346 tree rhs;
2348 stack_save_gsi = gsi_for_stmt (stack_save);
2349 rhs = build_int_cst (TREE_TYPE (gimple_call_arg (call, 0)), 0);
2350 update_call_from_tree (&stack_save_gsi, rhs);
2355 /* No effect, so the statement will be deleted. */
2356 return integer_zero_node;
2359 /* If va_list type is a simple pointer and nothing special is needed,
2360 optimize __builtin_va_start (&ap, 0) into ap = __builtin_next_arg (0),
2361 __builtin_va_end (&ap) out as NOP and __builtin_va_copy into a simple
2362 pointer assignment. */
2364 static tree
2365 optimize_stdarg_builtin (gimple call)
2367 tree callee, lhs, rhs, cfun_va_list;
2368 bool va_list_simple_ptr;
2369 location_t loc = gimple_location (call);
2371 if (gimple_code (call) != GIMPLE_CALL)
2372 return NULL_TREE;
2374 callee = gimple_call_fndecl (call);
2376 cfun_va_list = targetm.fn_abi_va_list (callee);
2377 va_list_simple_ptr = POINTER_TYPE_P (cfun_va_list)
2378 && (TREE_TYPE (cfun_va_list) == void_type_node
2379 || TREE_TYPE (cfun_va_list) == char_type_node);
2381 switch (DECL_FUNCTION_CODE (callee))
2383 case BUILT_IN_VA_START:
2384 if (!va_list_simple_ptr
2385 || targetm.expand_builtin_va_start != NULL
2386 || !builtin_decl_explicit_p (BUILT_IN_NEXT_ARG))
2387 return NULL_TREE;
2389 if (gimple_call_num_args (call) != 2)
2390 return NULL_TREE;
2392 lhs = gimple_call_arg (call, 0);
2393 if (!POINTER_TYPE_P (TREE_TYPE (lhs))
2394 || TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs)))
2395 != TYPE_MAIN_VARIANT (cfun_va_list))
2396 return NULL_TREE;
2398 lhs = build_fold_indirect_ref_loc (loc, lhs);
2399 rhs = build_call_expr_loc (loc, builtin_decl_explicit (BUILT_IN_NEXT_ARG),
2400 1, integer_zero_node);
2401 rhs = fold_convert_loc (loc, TREE_TYPE (lhs), rhs);
2402 return build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, rhs);
2404 case BUILT_IN_VA_COPY:
2405 if (!va_list_simple_ptr)
2406 return NULL_TREE;
2408 if (gimple_call_num_args (call) != 2)
2409 return NULL_TREE;
2411 lhs = gimple_call_arg (call, 0);
2412 if (!POINTER_TYPE_P (TREE_TYPE (lhs))
2413 || TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs)))
2414 != TYPE_MAIN_VARIANT (cfun_va_list))
2415 return NULL_TREE;
2417 lhs = build_fold_indirect_ref_loc (loc, lhs);
2418 rhs = gimple_call_arg (call, 1);
2419 if (TYPE_MAIN_VARIANT (TREE_TYPE (rhs))
2420 != TYPE_MAIN_VARIANT (cfun_va_list))
2421 return NULL_TREE;
2423 rhs = fold_convert_loc (loc, TREE_TYPE (lhs), rhs);
2424 return build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, rhs);
2426 case BUILT_IN_VA_END:
2427 /* No effect, so the statement will be deleted. */
2428 return integer_zero_node;
2430 default:
2431 gcc_unreachable ();
2435 /* Attemp to make the block of __builtin_unreachable I unreachable by changing
2436 the incoming jumps. Return true if at least one jump was changed. */
2438 static bool
2439 optimize_unreachable (gimple_stmt_iterator i)
2441 basic_block bb = gsi_bb (i);
2442 gimple_stmt_iterator gsi;
2443 gimple stmt;
2444 edge_iterator ei;
2445 edge e;
2446 bool ret;
2448 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
2450 stmt = gsi_stmt (gsi);
2452 if (is_gimple_debug (stmt))
2453 continue;
2455 if (gimple_code (stmt) == GIMPLE_LABEL)
2457 /* Verify we do not need to preserve the label. */
2458 if (FORCED_LABEL (gimple_label_label (stmt)))
2459 return false;
2461 continue;
2464 /* Only handle the case that __builtin_unreachable is the first statement
2465 in the block. We rely on DCE to remove stmts without side-effects
2466 before __builtin_unreachable. */
2467 if (gsi_stmt (gsi) != gsi_stmt (i))
2468 return false;
2471 ret = false;
2472 FOR_EACH_EDGE (e, ei, bb->preds)
2474 gsi = gsi_last_bb (e->src);
2475 if (gsi_end_p (gsi))
2476 continue;
2478 stmt = gsi_stmt (gsi);
2479 if (gimple_code (stmt) == GIMPLE_COND)
2481 if (e->flags & EDGE_TRUE_VALUE)
2482 gimple_cond_make_false (stmt);
2483 else if (e->flags & EDGE_FALSE_VALUE)
2484 gimple_cond_make_true (stmt);
2485 else
2486 gcc_unreachable ();
2487 update_stmt (stmt);
2489 else
2491 /* Todo: handle other cases, f.i. switch statement. */
2492 continue;
2495 ret = true;
2498 return ret;
2501 /* A simple pass that attempts to fold all builtin functions. This pass
2502 is run after we've propagated as many constants as we can. */
2504 static unsigned int
2505 execute_fold_all_builtins (void)
2507 bool cfg_changed = false;
2508 basic_block bb;
2509 unsigned int todoflags = 0;
2511 FOR_EACH_BB_FN (bb, cfun)
2513 gimple_stmt_iterator i;
2514 for (i = gsi_start_bb (bb); !gsi_end_p (i); )
2516 gimple stmt, old_stmt;
2517 tree callee, result;
2518 enum built_in_function fcode;
2520 stmt = gsi_stmt (i);
2522 if (gimple_code (stmt) != GIMPLE_CALL)
2524 /* Remove all *ssaname_N ={v} {CLOBBER}; stmts,
2525 after the last GIMPLE DSE they aren't needed and might
2526 unnecessarily keep the SSA_NAMEs live. */
2527 if (gimple_clobber_p (stmt))
2529 tree lhs = gimple_assign_lhs (stmt);
2530 if (TREE_CODE (lhs) == MEM_REF
2531 && TREE_CODE (TREE_OPERAND (lhs, 0)) == SSA_NAME)
2533 unlink_stmt_vdef (stmt);
2534 gsi_remove (&i, true);
2535 release_defs (stmt);
2536 continue;
2539 gsi_next (&i);
2540 continue;
2542 callee = gimple_call_fndecl (stmt);
2543 if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)
2545 gsi_next (&i);
2546 continue;
2548 fcode = DECL_FUNCTION_CODE (callee);
2550 result = gimple_fold_builtin (stmt);
2552 if (result)
2553 gimple_remove_stmt_histograms (cfun, stmt);
2555 if (!result)
2556 switch (DECL_FUNCTION_CODE (callee))
2558 case BUILT_IN_CONSTANT_P:
2559 /* Resolve __builtin_constant_p. If it hasn't been
2560 folded to integer_one_node by now, it's fairly
2561 certain that the value simply isn't constant. */
2562 result = integer_zero_node;
2563 break;
2565 case BUILT_IN_ASSUME_ALIGNED:
2566 /* Remove __builtin_assume_aligned. */
2567 result = gimple_call_arg (stmt, 0);
2568 break;
2570 case BUILT_IN_STACK_RESTORE:
2571 result = optimize_stack_restore (i);
2572 if (result)
2573 break;
2574 gsi_next (&i);
2575 continue;
2577 case BUILT_IN_UNREACHABLE:
2578 if (optimize_unreachable (i))
2579 cfg_changed = true;
2580 break;
2582 case BUILT_IN_VA_START:
2583 case BUILT_IN_VA_END:
2584 case BUILT_IN_VA_COPY:
2585 /* These shouldn't be folded before pass_stdarg. */
2586 result = optimize_stdarg_builtin (stmt);
2587 if (result)
2588 break;
2589 /* FALLTHRU */
2591 default:
2592 gsi_next (&i);
2593 continue;
2596 if (result == NULL_TREE)
2597 break;
2599 if (dump_file && (dump_flags & TDF_DETAILS))
2601 fprintf (dump_file, "Simplified\n ");
2602 print_gimple_stmt (dump_file, stmt, 0, dump_flags);
2605 old_stmt = stmt;
2606 if (!update_call_from_tree (&i, result))
2608 gimplify_and_update_call_from_tree (&i, result);
2609 todoflags |= TODO_update_address_taken;
2612 stmt = gsi_stmt (i);
2613 update_stmt (stmt);
2615 if (maybe_clean_or_replace_eh_stmt (old_stmt, stmt)
2616 && gimple_purge_dead_eh_edges (bb))
2617 cfg_changed = true;
2619 if (dump_file && (dump_flags & TDF_DETAILS))
2621 fprintf (dump_file, "to\n ");
2622 print_gimple_stmt (dump_file, stmt, 0, dump_flags);
2623 fprintf (dump_file, "\n");
2626 /* Retry the same statement if it changed into another
2627 builtin, there might be new opportunities now. */
2628 if (gimple_code (stmt) != GIMPLE_CALL)
2630 gsi_next (&i);
2631 continue;
2633 callee = gimple_call_fndecl (stmt);
2634 if (!callee
2635 || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL
2636 || DECL_FUNCTION_CODE (callee) == fcode)
2637 gsi_next (&i);
2641 /* Delete unreachable blocks. */
2642 if (cfg_changed)
2643 todoflags |= TODO_cleanup_cfg;
2645 return todoflags;
2649 namespace {
2651 const pass_data pass_data_fold_builtins =
2653 GIMPLE_PASS, /* type */
2654 "fab", /* name */
2655 OPTGROUP_NONE, /* optinfo_flags */
2656 false, /* has_gate */
2657 true, /* has_execute */
2658 TV_NONE, /* tv_id */
2659 ( PROP_cfg | PROP_ssa ), /* properties_required */
2660 0, /* properties_provided */
2661 0, /* properties_destroyed */
2662 0, /* todo_flags_start */
2663 ( TODO_verify_ssa | TODO_update_ssa ), /* todo_flags_finish */
2666 class pass_fold_builtins : public gimple_opt_pass
2668 public:
2669 pass_fold_builtins (gcc::context *ctxt)
2670 : gimple_opt_pass (pass_data_fold_builtins, ctxt)
2673 /* opt_pass methods: */
2674 opt_pass * clone () { return new pass_fold_builtins (m_ctxt); }
2675 unsigned int execute () { return execute_fold_all_builtins (); }
2677 }; // class pass_fold_builtins
2679 } // anon namespace
2681 gimple_opt_pass *
2682 make_pass_fold_builtins (gcc::context *ctxt)
2684 return new pass_fold_builtins (ctxt);