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"
139 /* Possible lattice values. */
148 struct prop_value_d {
150 ccp_lattice_t lattice_val;
152 /* Propagated value. */
155 /* Mask that applies to the propagated value during CCP. For
156 X with a CONSTANT lattice value X & ~mask == value & ~mask. */
160 typedef struct prop_value_d prop_value_t;
162 /* Array of propagated constant values. After propagation,
163 CONST_VAL[I].VALUE holds the constant value for SSA_NAME(I). If
164 the constant is held in an SSA name representing a memory store
165 (i.e., a VDEF), CONST_VAL[I].MEM_REF will contain the actual
166 memory reference used to store (i.e., the LHS of the assignment
168 static prop_value_t *const_val;
170 static void canonicalize_float_value (prop_value_t *);
171 static bool ccp_fold_stmt (gimple_stmt_iterator *);
173 /* Dump constant propagation value VAL to file OUTF prefixed by PREFIX. */
176 dump_lattice_value (FILE *outf, const char *prefix, prop_value_t val)
178 switch (val.lattice_val)
181 fprintf (outf, "%sUNINITIALIZED", prefix);
184 fprintf (outf, "%sUNDEFINED", prefix);
187 fprintf (outf, "%sVARYING", prefix);
190 fprintf (outf, "%sCONSTANT ", prefix);
191 if (TREE_CODE (val.value) != INTEGER_CST
192 || double_int_zero_p (val.mask))
193 print_generic_expr (outf, val.value, dump_flags);
196 double_int cval = double_int_and_not (tree_to_double_int (val.value),
198 fprintf (outf, "%sCONSTANT " HOST_WIDE_INT_PRINT_DOUBLE_HEX,
199 prefix, cval.high, cval.low);
200 fprintf (outf, " (" HOST_WIDE_INT_PRINT_DOUBLE_HEX ")",
201 val.mask.high, val.mask.low);
210 /* Print lattice value VAL to stderr. */
212 void debug_lattice_value (prop_value_t val);
215 debug_lattice_value (prop_value_t val)
217 dump_lattice_value (stderr, "", val);
218 fprintf (stderr, "\n");
222 /* Compute a default value for variable VAR and store it in the
223 CONST_VAL array. The following rules are used to get default
226 1- Global and static variables that are declared constant are
229 2- Any other value is considered UNDEFINED. This is useful when
230 considering PHI nodes. PHI arguments that are undefined do not
231 change the constant value of the PHI node, which allows for more
232 constants to be propagated.
234 3- Variables defined by statements other than assignments and PHI
235 nodes are considered VARYING.
237 4- Initial values of variables that are not GIMPLE registers are
238 considered VARYING. */
241 get_default_value (tree var)
243 tree sym = SSA_NAME_VAR (var);
244 prop_value_t val = { UNINITIALIZED, NULL_TREE, { 0, 0 } };
247 stmt = SSA_NAME_DEF_STMT (var);
249 if (gimple_nop_p (stmt))
251 /* Variables defined by an empty statement are those used
252 before being initialized. If VAR is a local variable, we
253 can assume initially that it is UNDEFINED, otherwise we must
254 consider it VARYING. */
255 if (is_gimple_reg (sym)
256 && TREE_CODE (sym) == VAR_DECL)
257 val.lattice_val = UNDEFINED;
260 val.lattice_val = VARYING;
261 val.mask = double_int_minus_one;
264 else if (is_gimple_assign (stmt)
265 /* Value-returning GIMPLE_CALL statements assign to
266 a variable, and are treated similarly to GIMPLE_ASSIGN. */
267 || (is_gimple_call (stmt)
268 && gimple_call_lhs (stmt) != NULL_TREE)
269 || gimple_code (stmt) == GIMPLE_PHI)
272 if (gimple_assign_single_p (stmt)
273 && DECL_P (gimple_assign_rhs1 (stmt))
274 && (cst = get_symbol_constant_value (gimple_assign_rhs1 (stmt))))
276 val.lattice_val = CONSTANT;
280 /* Any other variable defined by an assignment or a PHI node
281 is considered UNDEFINED. */
282 val.lattice_val = UNDEFINED;
286 /* Otherwise, VAR will never take on a constant value. */
287 val.lattice_val = VARYING;
288 val.mask = double_int_minus_one;
295 /* Get the constant value associated with variable VAR. */
297 static inline prop_value_t *
302 if (const_val == NULL)
305 val = &const_val[SSA_NAME_VERSION (var)];
306 if (val->lattice_val == UNINITIALIZED)
307 *val = get_default_value (var);
309 canonicalize_float_value (val);
314 /* Return the constant tree value associated with VAR. */
317 get_constant_value (tree var)
320 if (TREE_CODE (var) != SSA_NAME)
322 if (is_gimple_min_invariant (var))
326 val = get_value (var);
328 && val->lattice_val == CONSTANT
329 && (TREE_CODE (val->value) != INTEGER_CST
330 || double_int_zero_p (val->mask)))
335 /* Sets the value associated with VAR to VARYING. */
338 set_value_varying (tree var)
340 prop_value_t *val = &const_val[SSA_NAME_VERSION (var)];
342 val->lattice_val = VARYING;
343 val->value = NULL_TREE;
344 val->mask = double_int_minus_one;
347 /* For float types, modify the value of VAL to make ccp work correctly
348 for non-standard values (-0, NaN):
350 If HONOR_SIGNED_ZEROS is false, and VAL = -0, we canonicalize it to 0.
351 If HONOR_NANS is false, and VAL is NaN, we canonicalize it to UNDEFINED.
352 This is to fix the following problem (see PR 29921): Suppose we have
356 and we set value of y to NaN. This causes value of x to be set to NaN.
357 When we later determine that y is in fact VARYING, fold uses the fact
358 that HONOR_NANS is false, and we try to change the value of x to 0,
359 causing an ICE. With HONOR_NANS being false, the real appearance of
360 NaN would cause undefined behavior, though, so claiming that y (and x)
361 are UNDEFINED initially is correct. */
364 canonicalize_float_value (prop_value_t *val)
366 enum machine_mode mode;
370 if (val->lattice_val != CONSTANT
371 || TREE_CODE (val->value) != REAL_CST)
374 d = TREE_REAL_CST (val->value);
375 type = TREE_TYPE (val->value);
376 mode = TYPE_MODE (type);
378 if (!HONOR_SIGNED_ZEROS (mode)
379 && REAL_VALUE_MINUS_ZERO (d))
381 val->value = build_real (type, dconst0);
385 if (!HONOR_NANS (mode)
386 && REAL_VALUE_ISNAN (d))
388 val->lattice_val = UNDEFINED;
394 /* Return whether the lattice transition is valid. */
397 valid_lattice_transition (prop_value_t old_val, prop_value_t new_val)
399 /* Lattice transitions must always be monotonically increasing in
401 if (old_val.lattice_val < new_val.lattice_val)
404 if (old_val.lattice_val != new_val.lattice_val)
407 if (!old_val.value && !new_val.value)
410 /* Now both lattice values are CONSTANT. */
412 /* Allow transitioning from &x to &x & ~3. */
413 if (TREE_CODE (old_val.value) != INTEGER_CST
414 && TREE_CODE (new_val.value) == INTEGER_CST)
417 /* Bit-lattices have to agree in the still valid bits. */
418 if (TREE_CODE (old_val.value) == INTEGER_CST
419 && TREE_CODE (new_val.value) == INTEGER_CST)
420 return double_int_equal_p
421 (double_int_and_not (tree_to_double_int (old_val.value),
423 double_int_and_not (tree_to_double_int (new_val.value),
426 /* Otherwise constant values have to agree. */
427 return operand_equal_p (old_val.value, new_val.value, 0);
430 /* Set the value for variable VAR to NEW_VAL. Return true if the new
431 value is different from VAR's previous value. */
434 set_lattice_value (tree var, prop_value_t new_val)
436 /* We can deal with old UNINITIALIZED values just fine here. */
437 prop_value_t *old_val = &const_val[SSA_NAME_VERSION (var)];
439 canonicalize_float_value (&new_val);
441 /* We have to be careful to not go up the bitwise lattice
442 represented by the mask.
443 ??? This doesn't seem to be the best place to enforce this. */
444 if (new_val.lattice_val == CONSTANT
445 && old_val->lattice_val == CONSTANT
446 && TREE_CODE (new_val.value) == INTEGER_CST
447 && TREE_CODE (old_val->value) == INTEGER_CST)
450 diff = double_int_xor (tree_to_double_int (new_val.value),
451 tree_to_double_int (old_val->value));
452 new_val.mask = double_int_ior (new_val.mask,
453 double_int_ior (old_val->mask, diff));
456 gcc_assert (valid_lattice_transition (*old_val, new_val));
458 /* If *OLD_VAL and NEW_VAL are the same, return false to inform the
459 caller that this was a non-transition. */
460 if (old_val->lattice_val != new_val.lattice_val
461 || (new_val.lattice_val == CONSTANT
462 && TREE_CODE (new_val.value) == INTEGER_CST
463 && (TREE_CODE (old_val->value) != INTEGER_CST
464 || !double_int_equal_p (new_val.mask, old_val->mask))))
466 /* ??? We would like to delay creation of INTEGER_CSTs from
467 partially constants here. */
469 if (dump_file && (dump_flags & TDF_DETAILS))
471 dump_lattice_value (dump_file, "Lattice value changed to ", new_val);
472 fprintf (dump_file, ". Adding SSA edges to worklist.\n");
477 gcc_assert (new_val.lattice_val != UNINITIALIZED);
484 static prop_value_t get_value_for_expr (tree, bool);
485 static prop_value_t bit_value_binop (enum tree_code, tree, tree, tree);
486 static void bit_value_binop_1 (enum tree_code, tree, double_int *, double_int *,
487 tree, double_int, double_int,
488 tree, double_int, double_int);
490 /* Return a double_int that can be used for bitwise simplifications
494 value_to_double_int (prop_value_t val)
497 && TREE_CODE (val.value) == INTEGER_CST)
498 return tree_to_double_int (val.value);
500 return double_int_zero;
503 /* Return the value for the address expression EXPR based on alignment
507 get_value_from_alignment (tree expr)
509 tree type = TREE_TYPE (expr);
511 unsigned HOST_WIDE_INT bitpos;
514 gcc_assert (TREE_CODE (expr) == ADDR_EXPR);
516 align = get_object_alignment_1 (TREE_OPERAND (expr, 0), &bitpos);
518 = double_int_and_not (POINTER_TYPE_P (type) || TYPE_UNSIGNED (type)
519 ? double_int_mask (TYPE_PRECISION (type))
520 : double_int_minus_one,
521 uhwi_to_double_int (align / BITS_PER_UNIT - 1));
522 val.lattice_val = double_int_minus_one_p (val.mask) ? VARYING : CONSTANT;
523 if (val.lattice_val == CONSTANT)
525 = double_int_to_tree (type, uhwi_to_double_int (bitpos / BITS_PER_UNIT));
527 val.value = NULL_TREE;
532 /* Return the value for the tree operand EXPR. If FOR_BITS_P is true
533 return constant bits extracted from alignment information for
534 invariant addresses. */
537 get_value_for_expr (tree expr, bool for_bits_p)
541 if (TREE_CODE (expr) == SSA_NAME)
543 val = *get_value (expr);
545 && val.lattice_val == CONSTANT
546 && TREE_CODE (val.value) == ADDR_EXPR)
547 val = get_value_from_alignment (val.value);
549 else if (is_gimple_min_invariant (expr)
550 && (!for_bits_p || TREE_CODE (expr) != ADDR_EXPR))
552 val.lattice_val = CONSTANT;
554 val.mask = double_int_zero;
555 canonicalize_float_value (&val);
557 else if (TREE_CODE (expr) == ADDR_EXPR)
558 val = get_value_from_alignment (expr);
561 val.lattice_val = VARYING;
562 val.mask = double_int_minus_one;
563 val.value = NULL_TREE;
568 /* Return the likely CCP lattice value for STMT.
570 If STMT has no operands, then return CONSTANT.
572 Else if undefinedness of operands of STMT cause its value to be
573 undefined, then return UNDEFINED.
575 Else if any operands of STMT are constants, then return CONSTANT.
577 Else return VARYING. */
580 likely_value (gimple stmt)
582 bool has_constant_operand, has_undefined_operand, all_undefined_operands;
587 enum gimple_code code = gimple_code (stmt);
589 /* This function appears to be called only for assignments, calls,
590 conditionals, and switches, due to the logic in visit_stmt. */
591 gcc_assert (code == GIMPLE_ASSIGN
592 || code == GIMPLE_CALL
593 || code == GIMPLE_COND
594 || code == GIMPLE_SWITCH);
596 /* If the statement has volatile operands, it won't fold to a
598 if (gimple_has_volatile_ops (stmt))
601 /* Arrive here for more complex cases. */
602 has_constant_operand = false;
603 has_undefined_operand = false;
604 all_undefined_operands = true;
605 FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
607 prop_value_t *val = get_value (use);
609 if (val->lattice_val == UNDEFINED)
610 has_undefined_operand = true;
612 all_undefined_operands = false;
614 if (val->lattice_val == CONSTANT)
615 has_constant_operand = true;
618 /* There may be constants in regular rhs operands. For calls we
619 have to ignore lhs, fndecl and static chain, otherwise only
621 for (i = (is_gimple_call (stmt) ? 2 : 0) + gimple_has_lhs (stmt);
622 i < gimple_num_ops (stmt); ++i)
624 tree op = gimple_op (stmt, i);
625 if (!op || TREE_CODE (op) == SSA_NAME)
627 if (is_gimple_min_invariant (op))
628 has_constant_operand = true;
631 if (has_constant_operand)
632 all_undefined_operands = false;
634 /* If the operation combines operands like COMPLEX_EXPR make sure to
635 not mark the result UNDEFINED if only one part of the result is
637 if (has_undefined_operand && all_undefined_operands)
639 else if (code == GIMPLE_ASSIGN && has_undefined_operand)
641 switch (gimple_assign_rhs_code (stmt))
643 /* Unary operators are handled with all_undefined_operands. */
646 case POINTER_PLUS_EXPR:
647 /* Not MIN_EXPR, MAX_EXPR. One VARYING operand may be selected.
648 Not bitwise operators, one VARYING operand may specify the
649 result completely. Not logical operators for the same reason.
650 Not COMPLEX_EXPR as one VARYING operand makes the result partly
651 not UNDEFINED. Not *DIV_EXPR, comparisons and shifts because
652 the undefined operand may be promoted. */
659 /* If there was an UNDEFINED operand but the result may be not UNDEFINED
660 fall back to VARYING even if there were CONSTANT operands. */
661 if (has_undefined_operand)
664 /* We do not consider virtual operands here -- load from read-only
665 memory may have only VARYING virtual operands, but still be
667 if (has_constant_operand
668 || gimple_references_memory_p (stmt))
674 /* Returns true if STMT cannot be constant. */
677 surely_varying_stmt_p (gimple stmt)
679 /* If the statement has operands that we cannot handle, it cannot be
681 if (gimple_has_volatile_ops (stmt))
684 /* If it is a call and does not return a value or is not a
685 builtin and not an indirect call, it is varying. */
686 if (is_gimple_call (stmt))
689 if (!gimple_call_lhs (stmt)
690 || ((fndecl = gimple_call_fndecl (stmt)) != NULL_TREE
691 && !DECL_BUILT_IN (fndecl)))
695 /* Any other store operation is not interesting. */
696 else if (gimple_vdef (stmt))
699 /* Anything other than assignments and conditional jumps are not
700 interesting for CCP. */
701 if (gimple_code (stmt) != GIMPLE_ASSIGN
702 && gimple_code (stmt) != GIMPLE_COND
703 && gimple_code (stmt) != GIMPLE_SWITCH
704 && gimple_code (stmt) != GIMPLE_CALL)
710 /* Initialize local data structures for CCP. */
713 ccp_initialize (void)
717 const_val = XCNEWVEC (prop_value_t, num_ssa_names);
719 /* Initialize simulation flags for PHI nodes and statements. */
722 gimple_stmt_iterator i;
724 for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
726 gimple stmt = gsi_stmt (i);
729 /* If the statement is a control insn, then we do not
730 want to avoid simulating the statement once. Failure
731 to do so means that those edges will never get added. */
732 if (stmt_ends_bb_p (stmt))
735 is_varying = surely_varying_stmt_p (stmt);
742 /* If the statement will not produce a constant, mark
743 all its outputs VARYING. */
744 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
745 set_value_varying (def);
747 prop_set_simulate_again (stmt, !is_varying);
751 /* Now process PHI nodes. We never clear the simulate_again flag on
752 phi nodes, since we do not know which edges are executable yet,
753 except for phi nodes for virtual operands when we do not do store ccp. */
756 gimple_stmt_iterator i;
758 for (i = gsi_start_phis (bb); !gsi_end_p (i); gsi_next (&i))
760 gimple phi = gsi_stmt (i);
762 if (!is_gimple_reg (gimple_phi_result (phi)))
763 prop_set_simulate_again (phi, false);
765 prop_set_simulate_again (phi, true);
770 /* Debug count support. Reset the values of ssa names
771 VARYING when the total number ssa names analyzed is
772 beyond the debug count specified. */
778 for (i = 0; i < num_ssa_names; i++)
782 const_val[i].lattice_val = VARYING;
783 const_val[i].mask = double_int_minus_one;
784 const_val[i].value = NULL_TREE;
790 /* Do final substitution of propagated values, cleanup the flowgraph and
791 free allocated storage.
793 Return TRUE when something was optimized. */
798 bool something_changed;
803 /* Derive alignment and misalignment information from partially
804 constant pointers in the lattice. */
805 for (i = 1; i < num_ssa_names; ++i)
807 tree name = ssa_name (i);
809 struct ptr_info_def *pi;
810 unsigned int tem, align;
813 || !POINTER_TYPE_P (TREE_TYPE (name)))
816 val = get_value (name);
817 if (val->lattice_val != CONSTANT
818 || TREE_CODE (val->value) != INTEGER_CST)
821 /* Trailing constant bits specify the alignment, trailing value
822 bits the misalignment. */
824 align = (tem & -tem);
828 pi = get_ptr_info (name);
830 pi->misalign = TREE_INT_CST_LOW (val->value) & (align - 1);
833 /* Perform substitutions based on the known constant values. */
834 something_changed = substitute_and_fold (get_constant_value,
835 ccp_fold_stmt, true);
839 return something_changed;;
843 /* Compute the meet operator between *VAL1 and *VAL2. Store the result
846 any M UNDEFINED = any
847 any M VARYING = VARYING
848 Ci M Cj = Ci if (i == j)
849 Ci M Cj = VARYING if (i != j)
853 ccp_lattice_meet (prop_value_t *val1, prop_value_t *val2)
855 if (val1->lattice_val == UNDEFINED)
857 /* UNDEFINED M any = any */
860 else if (val2->lattice_val == UNDEFINED)
862 /* any M UNDEFINED = any
863 Nothing to do. VAL1 already contains the value we want. */
866 else if (val1->lattice_val == VARYING
867 || val2->lattice_val == VARYING)
869 /* any M VARYING = VARYING. */
870 val1->lattice_val = VARYING;
871 val1->mask = double_int_minus_one;
872 val1->value = NULL_TREE;
874 else if (val1->lattice_val == CONSTANT
875 && val2->lattice_val == CONSTANT
876 && TREE_CODE (val1->value) == INTEGER_CST
877 && TREE_CODE (val2->value) == INTEGER_CST)
879 /* Ci M Cj = Ci if (i == j)
880 Ci M Cj = VARYING if (i != j)
882 For INTEGER_CSTs mask unequal bits. If no equal bits remain,
885 = double_int_ior (double_int_ior (val1->mask,
887 double_int_xor (tree_to_double_int (val1->value),
888 tree_to_double_int (val2->value)));
889 if (double_int_minus_one_p (val1->mask))
891 val1->lattice_val = VARYING;
892 val1->value = NULL_TREE;
895 else if (val1->lattice_val == CONSTANT
896 && val2->lattice_val == CONSTANT
897 && simple_cst_equal (val1->value, val2->value) == 1)
899 /* Ci M Cj = Ci if (i == j)
900 Ci M Cj = VARYING if (i != j)
902 VAL1 already contains the value we want for equivalent values. */
904 else if (val1->lattice_val == CONSTANT
905 && val2->lattice_val == CONSTANT
906 && (TREE_CODE (val1->value) == ADDR_EXPR
907 || TREE_CODE (val2->value) == ADDR_EXPR))
909 /* When not equal addresses are involved try meeting for
911 prop_value_t tem = *val2;
912 if (TREE_CODE (val1->value) == ADDR_EXPR)
913 *val1 = get_value_for_expr (val1->value, true);
914 if (TREE_CODE (val2->value) == ADDR_EXPR)
915 tem = get_value_for_expr (val2->value, true);
916 ccp_lattice_meet (val1, &tem);
920 /* Any other combination is VARYING. */
921 val1->lattice_val = VARYING;
922 val1->mask = double_int_minus_one;
923 val1->value = NULL_TREE;
928 /* Loop through the PHI_NODE's parameters for BLOCK and compare their
929 lattice values to determine PHI_NODE's lattice value. The value of a
930 PHI node is determined calling ccp_lattice_meet with all the arguments
931 of the PHI node that are incoming via executable edges. */
933 static enum ssa_prop_result
934 ccp_visit_phi_node (gimple phi)
937 prop_value_t *old_val, new_val;
939 if (dump_file && (dump_flags & TDF_DETAILS))
941 fprintf (dump_file, "\nVisiting PHI node: ");
942 print_gimple_stmt (dump_file, phi, 0, dump_flags);
945 old_val = get_value (gimple_phi_result (phi));
946 switch (old_val->lattice_val)
949 return SSA_PROP_VARYING;
956 new_val.lattice_val = UNDEFINED;
957 new_val.value = NULL_TREE;
964 for (i = 0; i < gimple_phi_num_args (phi); i++)
966 /* Compute the meet operator over all the PHI arguments flowing
967 through executable edges. */
968 edge e = gimple_phi_arg_edge (phi, i);
970 if (dump_file && (dump_flags & TDF_DETAILS))
973 "\n Argument #%d (%d -> %d %sexecutable)\n",
974 i, e->src->index, e->dest->index,
975 (e->flags & EDGE_EXECUTABLE) ? "" : "not ");
978 /* If the incoming edge is executable, Compute the meet operator for
979 the existing value of the PHI node and the current PHI argument. */
980 if (e->flags & EDGE_EXECUTABLE)
982 tree arg = gimple_phi_arg (phi, i)->def;
983 prop_value_t arg_val = get_value_for_expr (arg, false);
985 ccp_lattice_meet (&new_val, &arg_val);
987 if (dump_file && (dump_flags & TDF_DETAILS))
989 fprintf (dump_file, "\t");
990 print_generic_expr (dump_file, arg, dump_flags);
991 dump_lattice_value (dump_file, "\tValue: ", arg_val);
992 fprintf (dump_file, "\n");
995 if (new_val.lattice_val == VARYING)
1000 if (dump_file && (dump_flags & TDF_DETAILS))
1002 dump_lattice_value (dump_file, "\n PHI node value: ", new_val);
1003 fprintf (dump_file, "\n\n");
1006 /* Make the transition to the new value. */
1007 if (set_lattice_value (gimple_phi_result (phi), new_val))
1009 if (new_val.lattice_val == VARYING)
1010 return SSA_PROP_VARYING;
1012 return SSA_PROP_INTERESTING;
1015 return SSA_PROP_NOT_INTERESTING;
1018 /* Return the constant value for OP or OP otherwise. */
1021 valueize_op (tree op)
1023 if (TREE_CODE (op) == SSA_NAME)
1025 tree tem = get_constant_value (op);
1032 /* CCP specific front-end to the non-destructive constant folding
1035 Attempt to simplify the RHS of STMT knowing that one or more
1036 operands are constants.
1038 If simplification is possible, return the simplified RHS,
1039 otherwise return the original RHS or NULL_TREE. */
1042 ccp_fold (gimple stmt)
1044 location_t loc = gimple_location (stmt);
1045 switch (gimple_code (stmt))
1049 /* Handle comparison operators that can appear in GIMPLE form. */
1050 tree op0 = valueize_op (gimple_cond_lhs (stmt));
1051 tree op1 = valueize_op (gimple_cond_rhs (stmt));
1052 enum tree_code code = gimple_cond_code (stmt);
1053 return fold_binary_loc (loc, code, boolean_type_node, op0, op1);
1058 /* Return the constant switch index. */
1059 return valueize_op (gimple_switch_index (stmt));
1064 return gimple_fold_stmt_to_constant_1 (stmt, valueize_op);
1071 /* Apply the operation CODE in type TYPE to the value, mask pair
1072 RVAL and RMASK representing a value of type RTYPE and set
1073 the value, mask pair *VAL and *MASK to the result. */
1076 bit_value_unop_1 (enum tree_code code, tree type,
1077 double_int *val, double_int *mask,
1078 tree rtype, double_int rval, double_int rmask)
1084 *val = double_int_not (rval);
1089 double_int temv, temm;
1090 /* Return ~rval + 1. */
1091 bit_value_unop_1 (BIT_NOT_EXPR, type, &temv, &temm, type, rval, rmask);
1092 bit_value_binop_1 (PLUS_EXPR, type, val, mask,
1094 type, double_int_one, double_int_zero);
1102 /* First extend mask and value according to the original type. */
1103 uns = (TREE_CODE (rtype) == INTEGER_TYPE && TYPE_IS_SIZETYPE (rtype)
1104 ? 0 : TYPE_UNSIGNED (rtype));
1105 *mask = double_int_ext (rmask, TYPE_PRECISION (rtype), uns);
1106 *val = double_int_ext (rval, TYPE_PRECISION (rtype), uns);
1108 /* Then extend mask and value according to the target type. */
1109 uns = (TREE_CODE (type) == INTEGER_TYPE && TYPE_IS_SIZETYPE (type)
1110 ? 0 : TYPE_UNSIGNED (type));
1111 *mask = double_int_ext (*mask, TYPE_PRECISION (type), uns);
1112 *val = double_int_ext (*val, TYPE_PRECISION (type), uns);
1117 *mask = double_int_minus_one;
1122 /* Apply the operation CODE in type TYPE to the value, mask pairs
1123 R1VAL, R1MASK and R2VAL, R2MASK representing a values of type R1TYPE
1124 and R2TYPE and set the value, mask pair *VAL and *MASK to the result. */
1127 bit_value_binop_1 (enum tree_code code, tree type,
1128 double_int *val, double_int *mask,
1129 tree r1type, double_int r1val, double_int r1mask,
1130 tree r2type, double_int r2val, double_int r2mask)
1132 bool uns = (TREE_CODE (type) == INTEGER_TYPE
1133 && TYPE_IS_SIZETYPE (type) ? 0 : TYPE_UNSIGNED (type));
1134 /* Assume we'll get a constant result. Use an initial varying value,
1135 we fall back to varying in the end if necessary. */
1136 *mask = double_int_minus_one;
1140 /* The mask is constant where there is a known not
1141 set bit, (m1 | m2) & ((v1 | m1) & (v2 | m2)) */
1142 *mask = double_int_and (double_int_ior (r1mask, r2mask),
1143 double_int_and (double_int_ior (r1val, r1mask),
1144 double_int_ior (r2val, r2mask)));
1145 *val = double_int_and (r1val, r2val);
1149 /* The mask is constant where there is a known
1150 set bit, (m1 | m2) & ~((v1 & ~m1) | (v2 & ~m2)). */
1151 *mask = double_int_and_not
1152 (double_int_ior (r1mask, r2mask),
1153 double_int_ior (double_int_and_not (r1val, r1mask),
1154 double_int_and_not (r2val, r2mask)));
1155 *val = double_int_ior (r1val, r2val);
1160 *mask = double_int_ior (r1mask, r2mask);
1161 *val = double_int_xor (r1val, r2val);
1166 if (double_int_zero_p (r2mask))
1168 HOST_WIDE_INT shift = r2val.low;
1169 if (code == RROTATE_EXPR)
1171 *mask = double_int_lrotate (r1mask, shift, TYPE_PRECISION (type));
1172 *val = double_int_lrotate (r1val, shift, TYPE_PRECISION (type));
1178 /* ??? We can handle partially known shift counts if we know
1179 its sign. That way we can tell that (x << (y | 8)) & 255
1181 if (double_int_zero_p (r2mask))
1183 HOST_WIDE_INT shift = r2val.low;
1184 if (code == RSHIFT_EXPR)
1186 /* We need to know if we are doing a left or a right shift
1187 to properly shift in zeros for left shift and unsigned
1188 right shifts and the sign bit for signed right shifts.
1189 For signed right shifts we shift in varying in case
1190 the sign bit was varying. */
1193 *mask = double_int_lshift (r1mask, shift,
1194 TYPE_PRECISION (type), false);
1195 *val = double_int_lshift (r1val, shift,
1196 TYPE_PRECISION (type), false);
1200 /* ??? We can have sizetype related inconsistencies in
1202 if ((TREE_CODE (r1type) == INTEGER_TYPE
1203 && (TYPE_IS_SIZETYPE (r1type)
1204 ? 0 : TYPE_UNSIGNED (r1type))) != uns)
1208 *mask = double_int_rshift (r1mask, shift,
1209 TYPE_PRECISION (type), !uns);
1210 *val = double_int_rshift (r1val, shift,
1211 TYPE_PRECISION (type), !uns);
1222 case POINTER_PLUS_EXPR:
1225 /* Do the addition with unknown bits set to zero, to give carry-ins of
1226 zero wherever possible. */
1227 lo = double_int_add (double_int_and_not (r1val, r1mask),
1228 double_int_and_not (r2val, r2mask));
1229 lo = double_int_ext (lo, TYPE_PRECISION (type), uns);
1230 /* Do the addition with unknown bits set to one, to give carry-ins of
1231 one wherever possible. */
1232 hi = double_int_add (double_int_ior (r1val, r1mask),
1233 double_int_ior (r2val, r2mask));
1234 hi = double_int_ext (hi, TYPE_PRECISION (type), uns);
1235 /* Each bit in the result is known if (a) the corresponding bits in
1236 both inputs are known, and (b) the carry-in to that bit position
1237 is known. We can check condition (b) by seeing if we got the same
1238 result with minimised carries as with maximised carries. */
1239 *mask = double_int_ior (double_int_ior (r1mask, r2mask),
1240 double_int_xor (lo, hi));
1241 *mask = double_int_ext (*mask, TYPE_PRECISION (type), uns);
1242 /* It shouldn't matter whether we choose lo or hi here. */
1249 double_int temv, temm;
1250 bit_value_unop_1 (NEGATE_EXPR, r2type, &temv, &temm,
1251 r2type, r2val, r2mask);
1252 bit_value_binop_1 (PLUS_EXPR, type, val, mask,
1253 r1type, r1val, r1mask,
1254 r2type, temv, temm);
1260 /* Just track trailing zeros in both operands and transfer
1261 them to the other. */
1262 int r1tz = double_int_ctz (double_int_ior (r1val, r1mask));
1263 int r2tz = double_int_ctz (double_int_ior (r2val, r2mask));
1264 if (r1tz + r2tz >= HOST_BITS_PER_DOUBLE_INT)
1266 *mask = double_int_zero;
1267 *val = double_int_zero;
1269 else if (r1tz + r2tz > 0)
1271 *mask = double_int_not (double_int_mask (r1tz + r2tz));
1272 *mask = double_int_ext (*mask, TYPE_PRECISION (type), uns);
1273 *val = double_int_zero;
1281 double_int m = double_int_ior (r1mask, r2mask);
1282 if (!double_int_equal_p (double_int_and_not (r1val, m),
1283 double_int_and_not (r2val, m)))
1285 *mask = double_int_zero;
1286 *val = ((code == EQ_EXPR) ? double_int_zero : double_int_one);
1290 /* We know the result of a comparison is always one or zero. */
1291 *mask = double_int_one;
1292 *val = double_int_zero;
1300 double_int tem = r1val;
1306 code = swap_tree_comparison (code);
1313 /* If the most significant bits are not known we know nothing. */
1314 if (double_int_negative_p (r1mask) || double_int_negative_p (r2mask))
1317 /* For comparisons the signedness is in the comparison operands. */
1318 uns = (TREE_CODE (r1type) == INTEGER_TYPE
1319 && TYPE_IS_SIZETYPE (r1type) ? 0 : TYPE_UNSIGNED (r1type));
1320 /* ??? We can have sizetype related inconsistencies in the IL. */
1321 if ((TREE_CODE (r2type) == INTEGER_TYPE
1322 && TYPE_IS_SIZETYPE (r2type) ? 0 : TYPE_UNSIGNED (r2type)) != uns)
1325 /* If we know the most significant bits we know the values
1326 value ranges by means of treating varying bits as zero
1327 or one. Do a cross comparison of the max/min pairs. */
1328 maxmin = double_int_cmp (double_int_ior (r1val, r1mask),
1329 double_int_and_not (r2val, r2mask), uns);
1330 minmax = double_int_cmp (double_int_and_not (r1val, r1mask),
1331 double_int_ior (r2val, r2mask), uns);
1332 if (maxmin < 0) /* r1 is less than r2. */
1334 *mask = double_int_zero;
1335 *val = double_int_one;
1337 else if (minmax > 0) /* r1 is not less or equal to r2. */
1339 *mask = double_int_zero;
1340 *val = double_int_zero;
1342 else if (maxmin == minmax) /* r1 and r2 are equal. */
1344 /* This probably should never happen as we'd have
1345 folded the thing during fully constant value folding. */
1346 *mask = double_int_zero;
1347 *val = (code == LE_EXPR ? double_int_one : double_int_zero);
1351 /* We know the result of a comparison is always one or zero. */
1352 *mask = double_int_one;
1353 *val = double_int_zero;
1362 /* Return the propagation value when applying the operation CODE to
1363 the value RHS yielding type TYPE. */
1366 bit_value_unop (enum tree_code code, tree type, tree rhs)
1368 prop_value_t rval = get_value_for_expr (rhs, true);
1369 double_int value, mask;
1371 gcc_assert ((rval.lattice_val == CONSTANT
1372 && TREE_CODE (rval.value) == INTEGER_CST)
1373 || double_int_minus_one_p (rval.mask));
1374 bit_value_unop_1 (code, type, &value, &mask,
1375 TREE_TYPE (rhs), value_to_double_int (rval), rval.mask);
1376 if (!double_int_minus_one_p (mask))
1378 val.lattice_val = CONSTANT;
1380 /* ??? Delay building trees here. */
1381 val.value = double_int_to_tree (type, value);
1385 val.lattice_val = VARYING;
1386 val.value = NULL_TREE;
1387 val.mask = double_int_minus_one;
1392 /* Return the propagation value when applying the operation CODE to
1393 the values RHS1 and RHS2 yielding type TYPE. */
1396 bit_value_binop (enum tree_code code, tree type, tree rhs1, tree rhs2)
1398 prop_value_t r1val = get_value_for_expr (rhs1, true);
1399 prop_value_t r2val = get_value_for_expr (rhs2, true);
1400 double_int value, mask;
1402 gcc_assert ((r1val.lattice_val == CONSTANT
1403 && TREE_CODE (r1val.value) == INTEGER_CST)
1404 || double_int_minus_one_p (r1val.mask));
1405 gcc_assert ((r2val.lattice_val == CONSTANT
1406 && TREE_CODE (r2val.value) == INTEGER_CST)
1407 || double_int_minus_one_p (r2val.mask));
1408 bit_value_binop_1 (code, type, &value, &mask,
1409 TREE_TYPE (rhs1), value_to_double_int (r1val), r1val.mask,
1410 TREE_TYPE (rhs2), value_to_double_int (r2val), r2val.mask);
1411 if (!double_int_minus_one_p (mask))
1413 val.lattice_val = CONSTANT;
1415 /* ??? Delay building trees here. */
1416 val.value = double_int_to_tree (type, value);
1420 val.lattice_val = VARYING;
1421 val.value = NULL_TREE;
1422 val.mask = double_int_minus_one;
1427 /* Return the propagation value when applying __builtin_assume_aligned to
1431 bit_value_assume_aligned (gimple stmt)
1433 tree ptr = gimple_call_arg (stmt, 0), align, misalign = NULL_TREE;
1434 tree type = TREE_TYPE (ptr);
1435 unsigned HOST_WIDE_INT aligni, misaligni = 0;
1436 prop_value_t ptrval = get_value_for_expr (ptr, true);
1437 prop_value_t alignval;
1438 double_int value, mask;
1440 if (ptrval.lattice_val == UNDEFINED)
1442 gcc_assert ((ptrval.lattice_val == CONSTANT
1443 && TREE_CODE (ptrval.value) == INTEGER_CST)
1444 || double_int_minus_one_p (ptrval.mask));
1445 align = gimple_call_arg (stmt, 1);
1446 if (!host_integerp (align, 1))
1448 aligni = tree_low_cst (align, 1);
1450 || (aligni & (aligni - 1)) != 0)
1452 if (gimple_call_num_args (stmt) > 2)
1454 misalign = gimple_call_arg (stmt, 2);
1455 if (!host_integerp (misalign, 1))
1457 misaligni = tree_low_cst (misalign, 1);
1458 if (misaligni >= aligni)
1461 align = build_int_cst_type (type, -aligni);
1462 alignval = get_value_for_expr (align, true);
1463 bit_value_binop_1 (BIT_AND_EXPR, type, &value, &mask,
1464 type, value_to_double_int (ptrval), ptrval.mask,
1465 type, value_to_double_int (alignval), alignval.mask);
1466 if (!double_int_minus_one_p (mask))
1468 val.lattice_val = CONSTANT;
1470 gcc_assert ((mask.low & (aligni - 1)) == 0);
1471 gcc_assert ((value.low & (aligni - 1)) == 0);
1472 value.low |= misaligni;
1473 /* ??? Delay building trees here. */
1474 val.value = double_int_to_tree (type, value);
1478 val.lattice_val = VARYING;
1479 val.value = NULL_TREE;
1480 val.mask = double_int_minus_one;
1485 /* Evaluate statement STMT.
1486 Valid only for assignments, calls, conditionals, and switches. */
1489 evaluate_stmt (gimple stmt)
1492 tree simplified = NULL_TREE;
1493 ccp_lattice_t likelyvalue = likely_value (stmt);
1494 bool is_constant = false;
1496 if (dump_file && (dump_flags & TDF_DETAILS))
1498 fprintf (dump_file, "which is likely ");
1499 switch (likelyvalue)
1502 fprintf (dump_file, "CONSTANT");
1505 fprintf (dump_file, "UNDEFINED");
1508 fprintf (dump_file, "VARYING");
1512 fprintf (dump_file, "\n");
1515 /* If the statement is likely to have a CONSTANT result, then try
1516 to fold the statement to determine the constant value. */
1517 /* FIXME. This is the only place that we call ccp_fold.
1518 Since likely_value never returns CONSTANT for calls, we will
1519 not attempt to fold them, including builtins that may profit. */
1520 if (likelyvalue == CONSTANT)
1522 fold_defer_overflow_warnings ();
1523 simplified = ccp_fold (stmt);
1524 is_constant = simplified && is_gimple_min_invariant (simplified);
1525 fold_undefer_overflow_warnings (is_constant, stmt, 0);
1528 /* The statement produced a constant value. */
1529 val.lattice_val = CONSTANT;
1530 val.value = simplified;
1531 val.mask = double_int_zero;
1534 /* If the statement is likely to have a VARYING result, then do not
1535 bother folding the statement. */
1536 else if (likelyvalue == VARYING)
1538 enum gimple_code code = gimple_code (stmt);
1539 if (code == GIMPLE_ASSIGN)
1541 enum tree_code subcode = gimple_assign_rhs_code (stmt);
1543 /* Other cases cannot satisfy is_gimple_min_invariant
1545 if (get_gimple_rhs_class (subcode) == GIMPLE_SINGLE_RHS)
1546 simplified = gimple_assign_rhs1 (stmt);
1548 else if (code == GIMPLE_SWITCH)
1549 simplified = gimple_switch_index (stmt);
1551 /* These cannot satisfy is_gimple_min_invariant without folding. */
1552 gcc_assert (code == GIMPLE_CALL || code == GIMPLE_COND);
1553 is_constant = simplified && is_gimple_min_invariant (simplified);
1556 /* The statement produced a constant value. */
1557 val.lattice_val = CONSTANT;
1558 val.value = simplified;
1559 val.mask = double_int_zero;
1563 /* Resort to simplification for bitwise tracking. */
1564 if (flag_tree_bit_ccp
1565 && (likelyvalue == CONSTANT || is_gimple_call (stmt))
1568 enum gimple_code code = gimple_code (stmt);
1570 val.lattice_val = VARYING;
1571 val.value = NULL_TREE;
1572 val.mask = double_int_minus_one;
1573 if (code == GIMPLE_ASSIGN)
1575 enum tree_code subcode = gimple_assign_rhs_code (stmt);
1576 tree rhs1 = gimple_assign_rhs1 (stmt);
1577 switch (get_gimple_rhs_class (subcode))
1579 case GIMPLE_SINGLE_RHS:
1580 if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
1581 || POINTER_TYPE_P (TREE_TYPE (rhs1)))
1582 val = get_value_for_expr (rhs1, true);
1585 case GIMPLE_UNARY_RHS:
1586 if ((INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
1587 || POINTER_TYPE_P (TREE_TYPE (rhs1)))
1588 && (INTEGRAL_TYPE_P (gimple_expr_type (stmt))
1589 || POINTER_TYPE_P (gimple_expr_type (stmt))))
1590 val = bit_value_unop (subcode, gimple_expr_type (stmt), rhs1);
1593 case GIMPLE_BINARY_RHS:
1594 if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
1595 || POINTER_TYPE_P (TREE_TYPE (rhs1)))
1597 tree lhs = gimple_assign_lhs (stmt);
1598 tree rhs2 = gimple_assign_rhs2 (stmt);
1599 val = bit_value_binop (subcode,
1600 TREE_TYPE (lhs), rhs1, rhs2);
1607 else if (code == GIMPLE_COND)
1609 enum tree_code code = gimple_cond_code (stmt);
1610 tree rhs1 = gimple_cond_lhs (stmt);
1611 tree rhs2 = gimple_cond_rhs (stmt);
1612 if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
1613 || POINTER_TYPE_P (TREE_TYPE (rhs1)))
1614 val = bit_value_binop (code, TREE_TYPE (rhs1), rhs1, rhs2);
1616 else if (code == GIMPLE_CALL
1617 && (fndecl = gimple_call_fndecl (stmt))
1618 && DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL)
1620 switch (DECL_FUNCTION_CODE (fndecl))
1622 case BUILT_IN_MALLOC:
1623 case BUILT_IN_REALLOC:
1624 case BUILT_IN_CALLOC:
1625 case BUILT_IN_STRDUP:
1626 case BUILT_IN_STRNDUP:
1627 val.lattice_val = CONSTANT;
1628 val.value = build_int_cst (TREE_TYPE (gimple_get_lhs (stmt)), 0);
1629 val.mask = shwi_to_double_int
1630 (~(((HOST_WIDE_INT) MALLOC_ABI_ALIGNMENT)
1631 / BITS_PER_UNIT - 1));
1634 case BUILT_IN_ALLOCA:
1635 val.lattice_val = CONSTANT;
1636 val.value = build_int_cst (TREE_TYPE (gimple_get_lhs (stmt)), 0);
1637 val.mask = shwi_to_double_int
1638 (~(((HOST_WIDE_INT) BIGGEST_ALIGNMENT)
1639 / BITS_PER_UNIT - 1));
1642 /* These builtins return their first argument, unmodified. */
1643 case BUILT_IN_MEMCPY:
1644 case BUILT_IN_MEMMOVE:
1645 case BUILT_IN_MEMSET:
1646 case BUILT_IN_STRCPY:
1647 case BUILT_IN_STRNCPY:
1648 case BUILT_IN_MEMCPY_CHK:
1649 case BUILT_IN_MEMMOVE_CHK:
1650 case BUILT_IN_MEMSET_CHK:
1651 case BUILT_IN_STRCPY_CHK:
1652 case BUILT_IN_STRNCPY_CHK:
1653 val = get_value_for_expr (gimple_call_arg (stmt, 0), true);
1656 case BUILT_IN_ASSUME_ALIGNED:
1657 val = bit_value_assume_aligned (stmt);
1663 is_constant = (val.lattice_val == CONSTANT);
1668 /* The statement produced a nonconstant value. If the statement
1669 had UNDEFINED operands, then the result of the statement
1670 should be UNDEFINED. Otherwise, the statement is VARYING. */
1671 if (likelyvalue == UNDEFINED)
1673 val.lattice_val = likelyvalue;
1674 val.mask = double_int_zero;
1678 val.lattice_val = VARYING;
1679 val.mask = double_int_minus_one;
1682 val.value = NULL_TREE;
1688 /* Detects a vla-related alloca with a constant argument. Declares fixed-size
1689 array and return the address, if found, otherwise returns NULL_TREE. */
1692 fold_builtin_alloca_for_var (gimple stmt)
1694 unsigned HOST_WIDE_INT size, threshold, n_elem;
1695 tree lhs, arg, block, var, elem_type, array_type;
1699 lhs = gimple_call_lhs (stmt);
1700 if (lhs == NULL_TREE)
1703 /* Detect constant argument. */
1704 arg = get_constant_value (gimple_call_arg (stmt, 0));
1705 if (arg == NULL_TREE || TREE_CODE (arg) != INTEGER_CST
1706 || !host_integerp (arg, 1))
1708 size = TREE_INT_CST_LOW (arg);
1710 /* Heuristic: don't fold large vlas. */
1711 threshold = (unsigned HOST_WIDE_INT)PARAM_VALUE (PARAM_LARGE_STACK_FRAME);
1712 /* In case a vla is declared at function scope, it has the same lifetime as a
1713 declared array, so we allow a larger size. */
1714 block = gimple_block (stmt);
1715 if (!(cfun->after_inlining
1716 && TREE_CODE (BLOCK_SUPERCONTEXT (block)) == FUNCTION_DECL))
1718 if (size > threshold)
1721 /* Declare array. */
1722 elem_type = build_nonstandard_integer_type (BITS_PER_UNIT, 1);
1723 n_elem = size * 8 / BITS_PER_UNIT;
1724 align = MIN (size * 8, BIGGEST_ALIGNMENT);
1725 array_type = build_array_type_nelts (elem_type, n_elem);
1726 var = create_tmp_var (array_type, NULL);
1727 DECL_ALIGN (var) = align;
1729 /* Fold alloca to the address of the array. */
1730 return fold_convert (TREE_TYPE (lhs), build_fold_addr_expr (var));
1733 /* Fold the stmt at *GSI with CCP specific information that propagating
1734 and regular folding does not catch. */
1737 ccp_fold_stmt (gimple_stmt_iterator *gsi)
1739 gimple stmt = gsi_stmt (*gsi);
1741 switch (gimple_code (stmt))
1746 /* Statement evaluation will handle type mismatches in constants
1747 more gracefully than the final propagation. This allows us to
1748 fold more conditionals here. */
1749 val = evaluate_stmt (stmt);
1750 if (val.lattice_val != CONSTANT
1751 || !double_int_zero_p (val.mask))
1756 fprintf (dump_file, "Folding predicate ");
1757 print_gimple_expr (dump_file, stmt, 0, 0);
1758 fprintf (dump_file, " to ");
1759 print_generic_expr (dump_file, val.value, 0);
1760 fprintf (dump_file, "\n");
1763 if (integer_zerop (val.value))
1764 gimple_cond_make_false (stmt);
1766 gimple_cond_make_true (stmt);
1773 tree lhs = gimple_call_lhs (stmt);
1776 bool changed = false;
1779 /* If the call was folded into a constant make sure it goes
1780 away even if we cannot propagate into all uses because of
1783 && TREE_CODE (lhs) == SSA_NAME
1784 && (val = get_constant_value (lhs)))
1786 tree new_rhs = unshare_expr (val);
1788 if (!useless_type_conversion_p (TREE_TYPE (lhs),
1789 TREE_TYPE (new_rhs)))
1790 new_rhs = fold_convert (TREE_TYPE (lhs), new_rhs);
1791 res = update_call_from_tree (gsi, new_rhs);
1796 /* Internal calls provide no argument types, so the extra laxity
1797 for normal calls does not apply. */
1798 if (gimple_call_internal_p (stmt))
1801 /* The heuristic of fold_builtin_alloca_for_var differs before and after
1802 inlining, so we don't require the arg to be changed into a constant
1803 for folding, but just to be constant. */
1804 if (gimple_call_alloca_for_var_p (stmt))
1806 tree new_rhs = fold_builtin_alloca_for_var (stmt);
1808 if (new_rhs == NULL_TREE)
1810 res = update_call_from_tree (gsi, new_rhs);
1815 /* Propagate into the call arguments. Compared to replace_uses_in
1816 this can use the argument slot types for type verification
1817 instead of the current argument type. We also can safely
1818 drop qualifiers here as we are dealing with constants anyway. */
1819 argt = TYPE_ARG_TYPES (gimple_call_fntype (stmt));
1820 for (i = 0; i < gimple_call_num_args (stmt) && argt;
1821 ++i, argt = TREE_CHAIN (argt))
1823 tree arg = gimple_call_arg (stmt, i);
1824 if (TREE_CODE (arg) == SSA_NAME
1825 && (val = get_constant_value (arg))
1826 && useless_type_conversion_p
1827 (TYPE_MAIN_VARIANT (TREE_VALUE (argt)),
1828 TYPE_MAIN_VARIANT (TREE_TYPE (val))))
1830 gimple_call_set_arg (stmt, i, unshare_expr (val));
1840 tree lhs = gimple_assign_lhs (stmt);
1843 /* If we have a load that turned out to be constant replace it
1844 as we cannot propagate into all uses in all cases. */
1845 if (gimple_assign_single_p (stmt)
1846 && TREE_CODE (lhs) == SSA_NAME
1847 && (val = get_constant_value (lhs)))
1849 tree rhs = unshare_expr (val);
1850 if (!useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (rhs)))
1851 rhs = fold_build1 (VIEW_CONVERT_EXPR, TREE_TYPE (lhs), rhs);
1852 gimple_assign_set_rhs_from_tree (gsi, rhs);
1864 /* Visit the assignment statement STMT. Set the value of its LHS to the
1865 value computed by the RHS and store LHS in *OUTPUT_P. If STMT
1866 creates virtual definitions, set the value of each new name to that
1867 of the RHS (if we can derive a constant out of the RHS).
1868 Value-returning call statements also perform an assignment, and
1869 are handled here. */
1871 static enum ssa_prop_result
1872 visit_assignment (gimple stmt, tree *output_p)
1875 enum ssa_prop_result retval;
1877 tree lhs = gimple_get_lhs (stmt);
1879 gcc_assert (gimple_code (stmt) != GIMPLE_CALL
1880 || gimple_call_lhs (stmt) != NULL_TREE);
1882 if (gimple_assign_single_p (stmt)
1883 && gimple_assign_rhs_code (stmt) == SSA_NAME)
1884 /* For a simple copy operation, we copy the lattice values. */
1885 val = *get_value (gimple_assign_rhs1 (stmt));
1887 /* Evaluate the statement, which could be
1888 either a GIMPLE_ASSIGN or a GIMPLE_CALL. */
1889 val = evaluate_stmt (stmt);
1891 retval = SSA_PROP_NOT_INTERESTING;
1893 /* Set the lattice value of the statement's output. */
1894 if (TREE_CODE (lhs) == SSA_NAME)
1896 /* If STMT is an assignment to an SSA_NAME, we only have one
1898 if (set_lattice_value (lhs, val))
1901 if (val.lattice_val == VARYING)
1902 retval = SSA_PROP_VARYING;
1904 retval = SSA_PROP_INTERESTING;
1912 /* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING
1913 if it can determine which edge will be taken. Otherwise, return
1914 SSA_PROP_VARYING. */
1916 static enum ssa_prop_result
1917 visit_cond_stmt (gimple stmt, edge *taken_edge_p)
1922 block = gimple_bb (stmt);
1923 val = evaluate_stmt (stmt);
1924 if (val.lattice_val != CONSTANT
1925 || !double_int_zero_p (val.mask))
1926 return SSA_PROP_VARYING;
1928 /* Find which edge out of the conditional block will be taken and add it
1929 to the worklist. If no single edge can be determined statically,
1930 return SSA_PROP_VARYING to feed all the outgoing edges to the
1931 propagation engine. */
1932 *taken_edge_p = find_taken_edge (block, val.value);
1934 return SSA_PROP_INTERESTING;
1936 return SSA_PROP_VARYING;
1940 /* Evaluate statement STMT. If the statement produces an output value and
1941 its evaluation changes the lattice value of its output, return
1942 SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the
1945 If STMT is a conditional branch and we can determine its truth
1946 value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying
1947 value, return SSA_PROP_VARYING. */
1949 static enum ssa_prop_result
1950 ccp_visit_stmt (gimple stmt, edge *taken_edge_p, tree *output_p)
1955 if (dump_file && (dump_flags & TDF_DETAILS))
1957 fprintf (dump_file, "\nVisiting statement:\n");
1958 print_gimple_stmt (dump_file, stmt, 0, dump_flags);
1961 switch (gimple_code (stmt))
1964 /* If the statement is an assignment that produces a single
1965 output value, evaluate its RHS to see if the lattice value of
1966 its output has changed. */
1967 return visit_assignment (stmt, output_p);
1970 /* A value-returning call also performs an assignment. */
1971 if (gimple_call_lhs (stmt) != NULL_TREE)
1972 return visit_assignment (stmt, output_p);
1977 /* If STMT is a conditional branch, see if we can determine
1978 which branch will be taken. */
1979 /* FIXME. It appears that we should be able to optimize
1980 computed GOTOs here as well. */
1981 return visit_cond_stmt (stmt, taken_edge_p);
1987 /* Any other kind of statement is not interesting for constant
1988 propagation and, therefore, not worth simulating. */
1989 if (dump_file && (dump_flags & TDF_DETAILS))
1990 fprintf (dump_file, "No interesting values produced. Marked VARYING.\n");
1992 /* Definitions made by statements other than assignments to
1993 SSA_NAMEs represent unknown modifications to their outputs.
1994 Mark them VARYING. */
1995 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
1997 prop_value_t v = { VARYING, NULL_TREE, { -1, (HOST_WIDE_INT) -1 } };
1998 set_lattice_value (def, v);
2001 return SSA_PROP_VARYING;
2005 /* Main entry point for SSA Conditional Constant Propagation. */
2011 ssa_propagate (ccp_visit_stmt, ccp_visit_phi_node);
2012 if (ccp_finalize ())
2013 return (TODO_cleanup_cfg | TODO_update_ssa | TODO_remove_unused_locals);
2022 return flag_tree_ccp != 0;
2026 struct gimple_opt_pass pass_ccp =
2031 gate_ccp, /* gate */
2032 do_ssa_ccp, /* execute */
2035 0, /* static_pass_number */
2036 TV_TREE_CCP, /* tv_id */
2037 PROP_cfg | PROP_ssa, /* properties_required */
2038 0, /* properties_provided */
2039 0, /* properties_destroyed */
2040 0, /* todo_flags_start */
2042 | TODO_verify_stmts | TODO_ggc_collect/* todo_flags_finish */
2048 /* Try to optimize out __builtin_stack_restore. Optimize it out
2049 if there is another __builtin_stack_restore in the same basic
2050 block and no calls or ASM_EXPRs are in between, or if this block's
2051 only outgoing edge is to EXIT_BLOCK and there are no calls or
2052 ASM_EXPRs after this __builtin_stack_restore. */
2055 optimize_stack_restore (gimple_stmt_iterator i)
2060 basic_block bb = gsi_bb (i);
2061 gimple call = gsi_stmt (i);
2063 if (gimple_code (call) != GIMPLE_CALL
2064 || gimple_call_num_args (call) != 1
2065 || TREE_CODE (gimple_call_arg (call, 0)) != SSA_NAME
2066 || !POINTER_TYPE_P (TREE_TYPE (gimple_call_arg (call, 0))))
2069 for (gsi_next (&i); !gsi_end_p (i); gsi_next (&i))
2071 stmt = gsi_stmt (i);
2072 if (gimple_code (stmt) == GIMPLE_ASM)
2074 if (gimple_code (stmt) != GIMPLE_CALL)
2077 callee = gimple_call_fndecl (stmt);
2079 || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL
2080 /* All regular builtins are ok, just obviously not alloca. */
2081 || DECL_FUNCTION_CODE (callee) == BUILT_IN_ALLOCA)
2084 if (DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_RESTORE)
2085 goto second_stack_restore;
2091 /* Allow one successor of the exit block, or zero successors. */
2092 switch (EDGE_COUNT (bb->succs))
2097 if (single_succ_edge (bb)->dest != EXIT_BLOCK_PTR)
2103 second_stack_restore:
2105 /* If there's exactly one use, then zap the call to __builtin_stack_save.
2106 If there are multiple uses, then the last one should remove the call.
2107 In any case, whether the call to __builtin_stack_save can be removed
2108 or not is irrelevant to removing the call to __builtin_stack_restore. */
2109 if (has_single_use (gimple_call_arg (call, 0)))
2111 gimple stack_save = SSA_NAME_DEF_STMT (gimple_call_arg (call, 0));
2112 if (is_gimple_call (stack_save))
2114 callee = gimple_call_fndecl (stack_save);
2116 && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL
2117 && DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_SAVE)
2119 gimple_stmt_iterator stack_save_gsi;
2122 stack_save_gsi = gsi_for_stmt (stack_save);
2123 rhs = build_int_cst (TREE_TYPE (gimple_call_arg (call, 0)), 0);
2124 update_call_from_tree (&stack_save_gsi, rhs);
2129 /* No effect, so the statement will be deleted. */
2130 return integer_zero_node;
2133 /* If va_list type is a simple pointer and nothing special is needed,
2134 optimize __builtin_va_start (&ap, 0) into ap = __builtin_next_arg (0),
2135 __builtin_va_end (&ap) out as NOP and __builtin_va_copy into a simple
2136 pointer assignment. */
2139 optimize_stdarg_builtin (gimple call)
2141 tree callee, lhs, rhs, cfun_va_list;
2142 bool va_list_simple_ptr;
2143 location_t loc = gimple_location (call);
2145 if (gimple_code (call) != GIMPLE_CALL)
2148 callee = gimple_call_fndecl (call);
2150 cfun_va_list = targetm.fn_abi_va_list (callee);
2151 va_list_simple_ptr = POINTER_TYPE_P (cfun_va_list)
2152 && (TREE_TYPE (cfun_va_list) == void_type_node
2153 || TREE_TYPE (cfun_va_list) == char_type_node);
2155 switch (DECL_FUNCTION_CODE (callee))
2157 case BUILT_IN_VA_START:
2158 if (!va_list_simple_ptr
2159 || targetm.expand_builtin_va_start != NULL
2160 || built_in_decls[BUILT_IN_NEXT_ARG] == NULL)
2163 if (gimple_call_num_args (call) != 2)
2166 lhs = gimple_call_arg (call, 0);
2167 if (!POINTER_TYPE_P (TREE_TYPE (lhs))
2168 || TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs)))
2169 != TYPE_MAIN_VARIANT (cfun_va_list))
2172 lhs = build_fold_indirect_ref_loc (loc, lhs);
2173 rhs = build_call_expr_loc (loc, built_in_decls[BUILT_IN_NEXT_ARG],
2174 1, integer_zero_node);
2175 rhs = fold_convert_loc (loc, TREE_TYPE (lhs), rhs);
2176 return build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, rhs);
2178 case BUILT_IN_VA_COPY:
2179 if (!va_list_simple_ptr)
2182 if (gimple_call_num_args (call) != 2)
2185 lhs = gimple_call_arg (call, 0);
2186 if (!POINTER_TYPE_P (TREE_TYPE (lhs))
2187 || TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (lhs)))
2188 != TYPE_MAIN_VARIANT (cfun_va_list))
2191 lhs = build_fold_indirect_ref_loc (loc, lhs);
2192 rhs = gimple_call_arg (call, 1);
2193 if (TYPE_MAIN_VARIANT (TREE_TYPE (rhs))
2194 != TYPE_MAIN_VARIANT (cfun_va_list))
2197 rhs = fold_convert_loc (loc, TREE_TYPE (lhs), rhs);
2198 return build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, rhs);
2200 case BUILT_IN_VA_END:
2201 /* No effect, so the statement will be deleted. */
2202 return integer_zero_node;
2209 /* A simple pass that attempts to fold all builtin functions. This pass
2210 is run after we've propagated as many constants as we can. */
2213 execute_fold_all_builtins (void)
2215 bool cfg_changed = false;
2217 unsigned int todoflags = 0;
2221 gimple_stmt_iterator i;
2222 for (i = gsi_start_bb (bb); !gsi_end_p (i); )
2224 gimple stmt, old_stmt;
2225 tree callee, result;
2226 enum built_in_function fcode;
2228 stmt = gsi_stmt (i);
2230 if (gimple_code (stmt) != GIMPLE_CALL)
2235 callee = gimple_call_fndecl (stmt);
2236 if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)
2241 fcode = DECL_FUNCTION_CODE (callee);
2243 result = gimple_fold_builtin (stmt);
2246 gimple_remove_stmt_histograms (cfun, stmt);
2249 switch (DECL_FUNCTION_CODE (callee))
2251 case BUILT_IN_CONSTANT_P:
2252 /* Resolve __builtin_constant_p. If it hasn't been
2253 folded to integer_one_node by now, it's fairly
2254 certain that the value simply isn't constant. */
2255 result = integer_zero_node;
2258 case BUILT_IN_ASSUME_ALIGNED:
2259 /* Remove __builtin_assume_aligned. */
2260 result = gimple_call_arg (stmt, 0);
2263 case BUILT_IN_STACK_RESTORE:
2264 result = optimize_stack_restore (i);
2270 case BUILT_IN_VA_START:
2271 case BUILT_IN_VA_END:
2272 case BUILT_IN_VA_COPY:
2273 /* These shouldn't be folded before pass_stdarg. */
2274 result = optimize_stdarg_builtin (stmt);
2284 if (dump_file && (dump_flags & TDF_DETAILS))
2286 fprintf (dump_file, "Simplified\n ");
2287 print_gimple_stmt (dump_file, stmt, 0, dump_flags);
2291 if (!update_call_from_tree (&i, result))
2293 gimplify_and_update_call_from_tree (&i, result);
2294 todoflags |= TODO_update_address_taken;
2297 stmt = gsi_stmt (i);
2300 if (maybe_clean_or_replace_eh_stmt (old_stmt, stmt)
2301 && gimple_purge_dead_eh_edges (bb))
2304 if (dump_file && (dump_flags & TDF_DETAILS))
2306 fprintf (dump_file, "to\n ");
2307 print_gimple_stmt (dump_file, stmt, 0, dump_flags);
2308 fprintf (dump_file, "\n");
2311 /* Retry the same statement if it changed into another
2312 builtin, there might be new opportunities now. */
2313 if (gimple_code (stmt) != GIMPLE_CALL)
2318 callee = gimple_call_fndecl (stmt);
2320 || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL
2321 || DECL_FUNCTION_CODE (callee) == fcode)
2326 /* Delete unreachable blocks. */
2328 todoflags |= TODO_cleanup_cfg;
2334 struct gimple_opt_pass pass_fold_builtins =
2340 execute_fold_all_builtins, /* execute */
2343 0, /* static_pass_number */
2344 TV_NONE, /* tv_id */
2345 PROP_cfg | PROP_ssa, /* properties_required */
2346 0, /* properties_provided */
2347 0, /* properties_destroyed */
2348 0, /* todo_flags_start */
2350 | TODO_update_ssa /* todo_flags_finish */