1 /* Conditional constant propagation pass for the GNU compiler.
2 Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005
3 Free Software Foundation, Inc.
4 Adapted from original RTL SSA-CCP by Daniel Berlin <dberlin@dberlin.org>
5 Adapted to GIMPLE trees by Diego Novillo <dnovillo@redhat.com>
7 This file is part of GCC.
9 GCC is free software; you can redistribute it and/or modify it
10 under the terms of the GNU General Public License as published by the
11 Free Software Foundation; either version 2, 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 COPYING. If not, write to the Free
21 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
24 /* Conditional constant propagation.
28 Constant propagation with conditional branches,
29 Wegman and Zadeck, ACM TOPLAS 13(2):181-210.
31 Building an Optimizing Compiler,
32 Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9.
34 Advanced Compiler Design and Implementation,
35 Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */
39 #include "coretypes.h"
46 #include "basic-block.h"
51 #include "diagnostic.h"
53 #include "tree-dump.h"
54 #include "tree-flow.h"
55 #include "tree-pass.h"
56 #include "tree-ssa-propagate.h"
57 #include "langhooks.h"
60 /* Possible lattice values. */
70 /* Main structure for CCP. Contains the lattice value and, if it's a
71 constant, the constant value. */
74 latticevalue lattice_val
;
78 /* This is used to track the current value of each variable. */
79 static value
*value_vector
;
82 /* Dump lattice value VAL to file OUTF prefixed by PREFIX. */
85 dump_lattice_value (FILE *outf
, const char *prefix
, value val
)
87 switch (val
.lattice_val
)
90 fprintf (outf
, "%sUNDEFINED", prefix
);
93 fprintf (outf
, "%sVARYING", prefix
);
96 fprintf (outf
, "%sUNKNOWN_VAL", prefix
);
99 fprintf (outf
, "%sCONSTANT ", prefix
);
100 print_generic_expr (outf
, val
.const_val
, dump_flags
);
108 /* Return a default value for variable VAR using the following rules:
110 1- Function arguments are considered VARYING.
112 2- Global and static variables that are declared constant are
115 3- Any other virtually defined variable is considered UNKNOWN_VAL.
117 4- Any other value is considered UNDEFINED. This is useful when
118 considering PHI nodes. PHI arguments that are undefined do not
119 change the constant value of the PHI node, which allows for more
120 constants to be propagated. */
123 get_default_value (tree var
)
128 if (TREE_CODE (var
) == SSA_NAME
)
129 sym
= SSA_NAME_VAR (var
);
132 gcc_assert (DECL_P (var
));
136 val
.lattice_val
= UNDEFINED
;
137 val
.const_val
= NULL_TREE
;
139 if (TREE_CODE (var
) == SSA_NAME
140 && SSA_NAME_VALUE (var
)
141 && is_gimple_min_invariant (SSA_NAME_VALUE (var
)))
143 val
.lattice_val
= CONSTANT
;
144 val
.const_val
= SSA_NAME_VALUE (var
);
146 else if (TREE_CODE (sym
) == PARM_DECL
|| TREE_THIS_VOLATILE (sym
))
148 /* Function arguments and volatile variables are considered VARYING. */
149 val
.lattice_val
= VARYING
;
151 else if (TREE_STATIC (sym
))
153 /* Globals and static variables are considered UNKNOWN_VAL,
154 unless they are declared 'const'. */
155 if (TREE_READONLY (sym
)
156 && DECL_INITIAL (sym
)
157 && is_gimple_min_invariant (DECL_INITIAL (sym
)))
159 val
.lattice_val
= CONSTANT
;
160 val
.const_val
= DECL_INITIAL (sym
);
164 val
.const_val
= NULL_TREE
;
165 val
.lattice_val
= UNKNOWN_VAL
;
168 else if (!is_gimple_reg (sym
))
170 val
.const_val
= NULL_TREE
;
171 val
.lattice_val
= UNKNOWN_VAL
;
176 tree stmt
= SSA_NAME_DEF_STMT (var
);
178 if (!IS_EMPTY_STMT (stmt
))
180 code
= TREE_CODE (stmt
);
181 if (code
!= MODIFY_EXPR
&& code
!= PHI_NODE
)
182 val
.lattice_val
= VARYING
;
189 /* Get the constant value associated with variable VAR. */
196 gcc_assert (TREE_CODE (var
) == SSA_NAME
);
198 val
= &value_vector
[SSA_NAME_VERSION (var
)];
199 if (val
->lattice_val
== UNINITIALIZED
)
200 *val
= get_default_value (var
);
206 /* Set the lattice value for variable VAR to VAL. Return true if VAL
207 is different from VAR's previous value. */
210 set_lattice_value (tree var
, value val
)
212 value
*old
= get_value (var
);
214 if (val
.lattice_val
== UNDEFINED
)
216 /* CONSTANT->UNDEFINED is never a valid state transition. */
217 gcc_assert (old
->lattice_val
!= CONSTANT
);
219 /* UNKNOWN_VAL->UNDEFINED is never a valid state transition. */
220 gcc_assert (old
->lattice_val
!= UNKNOWN_VAL
);
222 /* VARYING->UNDEFINED is generally not a valid state transition,
223 except for values which are initialized to VARYING. */
224 gcc_assert (old
->lattice_val
!= VARYING
225 || get_default_value (var
).lattice_val
== VARYING
);
227 else if (val
.lattice_val
== CONSTANT
)
228 /* VARYING -> CONSTANT is an invalid state transition, except
229 for objects which start off in a VARYING state. */
230 gcc_assert (old
->lattice_val
!= VARYING
231 || get_default_value (var
).lattice_val
== VARYING
);
233 /* If the constant for VAR has changed, then this VAR is really varying. */
234 if (old
->lattice_val
== CONSTANT
235 && val
.lattice_val
== CONSTANT
236 && !simple_cst_equal (old
->const_val
, val
.const_val
))
238 val
.lattice_val
= VARYING
;
239 val
.const_val
= NULL_TREE
;
242 if (old
->lattice_val
!= val
.lattice_val
)
244 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
246 dump_lattice_value (dump_file
, "Lattice value changed to ", val
);
247 fprintf (dump_file
, ". Adding definition to SSA edges.\n");
258 /* Set the lattice value for the variable VAR to VARYING. */
261 def_to_varying (tree var
)
264 val
.lattice_val
= VARYING
;
265 val
.const_val
= NULL_TREE
;
266 set_lattice_value (var
, val
);
270 /* Return the likely latticevalue for STMT.
272 If STMT has no operands, then return CONSTANT.
274 Else if any operands of STMT are undefined, then return UNDEFINED.
276 Else if any operands of STMT are constants, then return CONSTANT.
278 Else return VARYING. */
281 likely_value (tree stmt
)
284 int found_constant
= 0;
289 /* If the statement makes aliased loads or has volatile operands, it
290 won't fold to a constant value. */
291 ann
= stmt_ann (stmt
);
292 if (ann
->makes_aliased_loads
|| ann
->has_volatile_ops
)
295 /* A CALL_EXPR is assumed to be varying. This may be overly conservative,
296 in the presence of const and pure calls. */
297 if (get_call_expr_in (stmt
) != NULL_TREE
)
300 get_stmt_operands (stmt
);
302 FOR_EACH_SSA_TREE_OPERAND (use
, stmt
, iter
, SSA_OP_USE
)
304 value
*val
= get_value (use
);
306 if (val
->lattice_val
== UNDEFINED
)
309 if (val
->lattice_val
== CONSTANT
)
313 vuses
= VUSE_OPS (ann
);
315 if (NUM_VUSES (vuses
))
317 tree vuse
= VUSE_OP (vuses
, 0);
318 value
*val
= get_value (vuse
);
320 if (val
->lattice_val
== UNKNOWN_VAL
)
323 /* There should be no VUSE operands that are UNDEFINED. */
324 gcc_assert (val
->lattice_val
!= UNDEFINED
);
326 if (val
->lattice_val
== CONSTANT
)
330 return ((found_constant
|| (!USE_OPS (ann
) && !vuses
)) ? CONSTANT
: VARYING
);
334 /* Initialize local data structures for CCP. */
337 ccp_initialize (void)
342 value_vector
= (value
*) xmalloc (num_ssa_names
* sizeof (value
));
343 memset (value_vector
, 0, num_ssa_names
* sizeof (value
));
345 /* Set of SSA_NAMEs that are defined by a V_MAY_DEF. */
346 is_may_def
= sbitmap_alloc (num_ssa_names
);
347 sbitmap_zero (is_may_def
);
349 /* Initialize simulation flags for PHI nodes and statements. */
352 block_stmt_iterator i
;
354 /* Mark all V_MAY_DEF operands VARYING. */
355 for (i
= bsi_start (bb
); !bsi_end_p (i
); bsi_next (&i
))
357 bool is_varying
= false;
358 tree stmt
= bsi_stmt (i
);
362 get_stmt_operands (stmt
);
364 /* Get the default value for each DEF and V_MUST_DEF. */
365 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
,
366 (SSA_OP_DEF
| SSA_OP_VMUSTDEF
))
368 if (get_value (def
)->lattice_val
== VARYING
)
372 /* Mark all V_MAY_DEF operands VARYING. */
373 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_VMAYDEF
)
375 get_value (def
)->lattice_val
= VARYING
;
376 SET_BIT (is_may_def
, SSA_NAME_VERSION (def
));
379 /* Statements other than MODIFY_EXPR, COND_EXPR and
380 SWITCH_EXPR are not interesting for constant propagation.
381 Mark them VARYING. */
382 if (TREE_CODE (stmt
) != MODIFY_EXPR
383 && TREE_CODE (stmt
) != COND_EXPR
384 && TREE_CODE (stmt
) != SWITCH_EXPR
)
387 DONT_SIMULATE_AGAIN (stmt
) = is_varying
;
391 /* Now process PHI nodes. */
397 for (phi
= phi_nodes (bb
); phi
; phi
= PHI_CHAIN (phi
))
399 value
*val
= get_value (PHI_RESULT (phi
));
401 for (x
= 0; x
< PHI_NUM_ARGS (phi
); x
++)
403 var
= PHI_ARG_DEF (phi
, x
);
405 /* If one argument has a V_MAY_DEF, the result is
407 if (TREE_CODE (var
) == SSA_NAME
)
409 if (TEST_BIT (is_may_def
, SSA_NAME_VERSION (var
)))
411 val
->lattice_val
= VARYING
;
412 SET_BIT (is_may_def
, SSA_NAME_VERSION (PHI_RESULT (phi
)));
418 DONT_SIMULATE_AGAIN (phi
) = (val
->lattice_val
== VARYING
);
422 sbitmap_free (is_may_def
);
426 /* Replace USE references in statement STMT with their immediate reaching
427 definition. Return true if at least one reference was replaced. If
428 REPLACED_ADDRESSES_P is given, it will be set to true if an address
429 constant was replaced. */
432 replace_uses_in (tree stmt
, bool *replaced_addresses_p
)
434 bool replaced
= false;
438 if (replaced_addresses_p
)
439 *replaced_addresses_p
= false;
441 get_stmt_operands (stmt
);
443 FOR_EACH_SSA_USE_OPERAND (use
, stmt
, iter
, SSA_OP_USE
)
445 tree tuse
= USE_FROM_PTR (use
);
446 value
*val
= get_value (tuse
);
448 if (val
->lattice_val
!= CONSTANT
)
451 if (TREE_CODE (stmt
) == ASM_EXPR
452 && !may_propagate_copy_into_asm (tuse
))
455 SET_USE (use
, val
->const_val
);
458 if (POINTER_TYPE_P (TREE_TYPE (tuse
)) && replaced_addresses_p
)
459 *replaced_addresses_p
= true;
466 /* Replace the VUSE references in statement STMT with its immediate reaching
467 definition. Return true if the reference was replaced. If
468 REPLACED_ADDRESSES_P is given, it will be set to true if an address
469 constant was replaced. */
472 replace_vuse_in (tree stmt
, bool *replaced_addresses_p
)
474 bool replaced
= false;
479 if (replaced_addresses_p
)
480 *replaced_addresses_p
= false;
482 get_stmt_operands (stmt
);
484 vuses
= STMT_VUSE_OPS (stmt
);
486 if (NUM_VUSES (vuses
) != 1)
489 vuse
= VUSE_OP_PTR (vuses
, 0);
490 val
= get_value (USE_FROM_PTR (vuse
));
492 if (val
->lattice_val
== CONSTANT
493 && TREE_CODE (stmt
) == MODIFY_EXPR
494 && DECL_P (TREE_OPERAND (stmt
, 1))
495 && TREE_OPERAND (stmt
, 1) == SSA_NAME_VAR (USE_FROM_PTR (vuse
)))
497 TREE_OPERAND (stmt
, 1) = val
->const_val
;
499 if (POINTER_TYPE_P (TREE_TYPE (USE_FROM_PTR (vuse
)))
500 && replaced_addresses_p
)
501 *replaced_addresses_p
= true;
508 /* Perform final substitution and folding. After this pass the program
509 should still be in SSA form. */
512 substitute_and_fold (void)
517 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
519 "\nSubstituing constants and folding statements\n\n");
521 /* Substitute constants in every statement of every basic block. */
524 block_stmt_iterator i
;
527 /* Propagate our known constants into PHI nodes. */
528 for (phi
= phi_nodes (bb
); phi
; phi
= PHI_CHAIN (phi
))
532 for (i
= 0; i
< PHI_NUM_ARGS (phi
); i
++)
535 use_operand_p orig_p
= PHI_ARG_DEF_PTR (phi
, i
);
536 tree orig
= USE_FROM_PTR (orig_p
);
538 if (! SSA_VAR_P (orig
))
541 new_val
= get_value (orig
);
542 if (new_val
->lattice_val
== CONSTANT
543 && may_propagate_copy (orig
, new_val
->const_val
))
544 SET_USE (orig_p
, new_val
->const_val
);
548 for (i
= bsi_start (bb
); !bsi_end_p (i
); bsi_next (&i
))
550 bool replaced_address
;
551 tree stmt
= bsi_stmt (i
);
553 /* Skip statements that have been folded already. */
554 if (stmt_modified_p (stmt
) || !is_exec_stmt (stmt
))
557 /* Replace the statement with its folded version and mark it
559 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
561 fprintf (dump_file
, "Line %d: replaced ", get_lineno (stmt
));
562 print_generic_stmt (dump_file
, stmt
, TDF_SLIM
);
565 if (replace_uses_in (stmt
, &replaced_address
)
566 || replace_vuse_in (stmt
, &replaced_address
))
568 bool changed
= fold_stmt (bsi_stmt_ptr (i
));
571 /* If we folded a builtin function, we'll likely
572 need to rename VDEFs. */
573 if (replaced_address
|| changed
)
574 mark_new_vars_to_rename (stmt
, vars_to_rename
);
576 /* If we cleaned up EH information from the statement,
578 if (maybe_clean_eh_stmt (stmt
))
579 tree_purge_dead_eh_edges (bb
);
584 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
586 fprintf (dump_file
, " with ");
587 print_generic_stmt (dump_file
, stmt
, TDF_SLIM
);
588 fprintf (dump_file
, "\n");
593 /* And transfer what we learned from VALUE_VECTOR into the
594 SSA_NAMEs themselves. This probably isn't terribly important
595 since we probably constant propagated the values to their
597 for (i
= 0; i
< num_ssa_names
; i
++)
599 tree name
= ssa_name (i
);
605 value
= get_value (name
);
606 if (value
->lattice_val
== CONSTANT
607 && is_gimple_reg (name
)
608 && is_gimple_min_invariant (value
->const_val
))
609 SSA_NAME_VALUE (name
) = value
->const_val
;
614 /* Free allocated storage. */
619 /* Perform substitutions based on the known constant values. */
620 substitute_and_fold ();
627 /* Compute the meet operator between VAL1 and VAL2:
629 any M UNDEFINED = any
630 any M VARYING = VARYING
631 any M UNKNOWN_VAL = UNKNOWN_VAL
632 Ci M Cj = Ci if (i == j)
633 Ci M Cj = VARYING if (i != j) */
635 ccp_lattice_meet (value val1
, value val2
)
639 /* any M UNDEFINED = any. */
640 if (val1
.lattice_val
== UNDEFINED
)
642 else if (val2
.lattice_val
== UNDEFINED
)
645 /* any M VARYING = VARYING. */
646 if (val1
.lattice_val
== VARYING
|| val2
.lattice_val
== VARYING
)
648 result
.lattice_val
= VARYING
;
649 result
.const_val
= NULL_TREE
;
653 /* any M UNKNOWN_VAL = UNKNOWN_VAL. */
654 if (val1
.lattice_val
== UNKNOWN_VAL
655 || val2
.lattice_val
== UNKNOWN_VAL
)
657 result
.lattice_val
= UNKNOWN_VAL
;
658 result
.const_val
= NULL_TREE
;
662 /* Ci M Cj = Ci if (i == j)
663 Ci M Cj = VARYING if (i != j) */
664 if (simple_cst_equal (val1
.const_val
, val2
.const_val
) == 1)
666 result
.lattice_val
= CONSTANT
;
667 result
.const_val
= val1
.const_val
;
671 result
.lattice_val
= VARYING
;
672 result
.const_val
= NULL_TREE
;
679 /* Loop through the PHI_NODE's parameters for BLOCK and compare their
680 lattice values to determine PHI_NODE's lattice value. The value of a
681 PHI node is determined calling ccp_lattice_meet() with all the arguments
682 of the PHI node that are incoming via executable edges. */
684 static enum ssa_prop_result
685 ccp_visit_phi_node (tree phi
)
687 value new_val
, *old_val
;
690 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
692 fprintf (dump_file
, "\nVisiting PHI node: ");
693 print_generic_expr (dump_file
, phi
, dump_flags
);
696 old_val
= get_value (PHI_RESULT (phi
));
697 switch (old_val
->lattice_val
)
700 return SSA_PROP_NOT_INTERESTING
;
707 /* To avoid the default value of UNKNOWN_VAL overriding
708 that of its possible constant arguments, temporarily
709 set the PHI node's default lattice value to be
710 UNDEFINED. If the PHI node's old value was UNKNOWN_VAL and
711 the new value is UNDEFINED, then we prevent the invalid
712 transition by not calling set_lattice_value. */
713 new_val
.lattice_val
= UNDEFINED
;
714 new_val
.const_val
= NULL_TREE
;
719 new_val
.lattice_val
= UNDEFINED
;
720 new_val
.const_val
= NULL_TREE
;
727 for (i
= 0; i
< PHI_NUM_ARGS (phi
); i
++)
729 /* Compute the meet operator over all the PHI arguments. */
730 edge e
= PHI_ARG_EDGE (phi
, i
);
732 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
735 "\n Argument #%d (%d -> %d %sexecutable)\n",
736 i
, e
->src
->index
, e
->dest
->index
,
737 (e
->flags
& EDGE_EXECUTABLE
) ? "" : "not ");
740 /* If the incoming edge is executable, Compute the meet operator for
741 the existing value of the PHI node and the current PHI argument. */
742 if (e
->flags
& EDGE_EXECUTABLE
)
744 tree rdef
= PHI_ARG_DEF (phi
, i
);
745 value
*rdef_val
, val
;
747 if (is_gimple_min_invariant (rdef
))
749 val
.lattice_val
= CONSTANT
;
750 val
.const_val
= rdef
;
754 rdef_val
= get_value (rdef
);
756 new_val
= ccp_lattice_meet (new_val
, *rdef_val
);
758 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
760 fprintf (dump_file
, "\t");
761 print_generic_expr (dump_file
, rdef
, dump_flags
);
762 dump_lattice_value (dump_file
, "\tValue: ", *rdef_val
);
763 fprintf (dump_file
, "\n");
766 if (new_val
.lattice_val
== VARYING
)
771 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
773 dump_lattice_value (dump_file
, "\n PHI node value: ", new_val
);
774 fprintf (dump_file
, "\n\n");
777 /* Check for an invalid change from UNKNOWN_VAL to UNDEFINED. */
778 if (old_val
->lattice_val
== UNKNOWN_VAL
779 && new_val
.lattice_val
== UNDEFINED
)
780 return SSA_PROP_NOT_INTERESTING
;
782 /* Otherwise, make the transition to the new value. */
783 if (set_lattice_value (PHI_RESULT (phi
), new_val
))
785 if (new_val
.lattice_val
== VARYING
)
786 return SSA_PROP_VARYING
;
788 return SSA_PROP_INTERESTING
;
791 return SSA_PROP_NOT_INTERESTING
;
795 /* CCP specific front-end to the non-destructive constant folding
798 Attempt to simplify the RHS of STMT knowing that one or more
799 operands are constants.
801 If simplification is possible, return the simplified RHS,
802 otherwise return the original RHS. */
807 tree rhs
= get_rhs (stmt
);
808 enum tree_code code
= TREE_CODE (rhs
);
809 enum tree_code_class kind
= TREE_CODE_CLASS (code
);
810 tree retval
= NULL_TREE
;
813 vuses
= STMT_VUSE_OPS (stmt
);
815 /* If the RHS is just a variable, then that variable must now have
816 a constant value that we can return directly. */
817 if (TREE_CODE (rhs
) == SSA_NAME
)
818 return get_value (rhs
)->const_val
;
819 else if (DECL_P (rhs
)
820 && NUM_VUSES (vuses
) == 1
821 && rhs
== SSA_NAME_VAR (VUSE_OP (vuses
, 0)))
822 return get_value (VUSE_OP (vuses
, 0))->const_val
;
824 /* Unary operators. Note that we know the single operand must
825 be a constant. So this should almost always return a
827 if (kind
== tcc_unary
)
829 /* Handle unary operators which can appear in GIMPLE form. */
830 tree op0
= TREE_OPERAND (rhs
, 0);
832 /* Simplify the operand down to a constant. */
833 if (TREE_CODE (op0
) == SSA_NAME
)
835 value
*val
= get_value (op0
);
836 if (val
->lattice_val
== CONSTANT
)
837 op0
= get_value (op0
)->const_val
;
840 retval
= fold_unary_to_constant (code
, TREE_TYPE (rhs
), op0
);
842 /* If we folded, but did not create an invariant, then we can not
843 use this expression. */
844 if (retval
&& ! is_gimple_min_invariant (retval
))
847 /* If we could not fold the expression, but the arguments are all
848 constants and gimple values, then build and return the new
851 In some cases the new expression is still something we can
852 use as a replacement for an argument. This happens with
853 NOP conversions of types for example.
855 In other cases the new expression can not be used as a
856 replacement for an argument (as it would create non-gimple
857 code). But the new expression can still be used to derive
859 if (! retval
&& is_gimple_min_invariant (op0
))
860 return build1 (code
, TREE_TYPE (rhs
), op0
);
863 /* Binary and comparison operators. We know one or both of the
864 operands are constants. */
865 else if (kind
== tcc_binary
866 || kind
== tcc_comparison
867 || code
== TRUTH_AND_EXPR
868 || code
== TRUTH_OR_EXPR
869 || code
== TRUTH_XOR_EXPR
)
871 /* Handle binary and comparison operators that can appear in
873 tree op0
= TREE_OPERAND (rhs
, 0);
874 tree op1
= TREE_OPERAND (rhs
, 1);
876 /* Simplify the operands down to constants when appropriate. */
877 if (TREE_CODE (op0
) == SSA_NAME
)
879 value
*val
= get_value (op0
);
880 if (val
->lattice_val
== CONSTANT
)
881 op0
= val
->const_val
;
884 if (TREE_CODE (op1
) == SSA_NAME
)
886 value
*val
= get_value (op1
);
887 if (val
->lattice_val
== CONSTANT
)
888 op1
= val
->const_val
;
891 retval
= fold_binary_to_constant (code
, TREE_TYPE (rhs
), op0
, op1
);
893 /* If we folded, but did not create an invariant, then we can not
894 use this expression. */
895 if (retval
&& ! is_gimple_min_invariant (retval
))
898 /* If we could not fold the expression, but the arguments are all
899 constants and gimple values, then build and return the new
902 In some cases the new expression is still something we can
903 use as a replacement for an argument. This happens with
904 NOP conversions of types for example.
906 In other cases the new expression can not be used as a
907 replacement for an argument (as it would create non-gimple
908 code). But the new expression can still be used to derive
911 && is_gimple_min_invariant (op0
)
912 && is_gimple_min_invariant (op1
))
913 return build (code
, TREE_TYPE (rhs
), op0
, op1
);
916 /* We may be able to fold away calls to builtin functions if their
917 arguments are constants. */
918 else if (code
== CALL_EXPR
919 && TREE_CODE (TREE_OPERAND (rhs
, 0)) == ADDR_EXPR
920 && (TREE_CODE (TREE_OPERAND (TREE_OPERAND (rhs
, 0), 0))
922 && DECL_BUILT_IN (TREE_OPERAND (TREE_OPERAND (rhs
, 0), 0)))
924 use_optype uses
= STMT_USE_OPS (stmt
);
925 if (NUM_USES (uses
) != 0)
928 tree fndecl
, arglist
;
931 /* Preserve the original values of every operand. */
932 orig
= xmalloc (sizeof (tree
) * NUM_USES (uses
));
933 for (i
= 0; i
< NUM_USES (uses
); i
++)
934 orig
[i
] = USE_OP (uses
, i
);
936 /* Substitute operands with their values and try to fold. */
937 replace_uses_in (stmt
, NULL
);
938 fndecl
= get_callee_fndecl (rhs
);
939 arglist
= TREE_OPERAND (rhs
, 1);
940 retval
= fold_builtin (fndecl
, arglist
, false);
942 /* Restore operands to their original form. */
943 for (i
= 0; i
< NUM_USES (uses
); i
++)
944 SET_USE_OP (uses
, i
, orig
[i
]);
951 /* If we got a simplified form, see if we need to convert its type. */
953 return fold_convert (TREE_TYPE (rhs
), retval
);
955 /* No simplification was possible. */
960 /* Evaluate statement STMT. */
963 evaluate_stmt (tree stmt
)
967 latticevalue likelyvalue
= likely_value (stmt
);
969 /* If the statement is likely to have a CONSTANT result, then try
970 to fold the statement to determine the constant value. */
971 if (likelyvalue
== CONSTANT
)
972 simplified
= ccp_fold (stmt
);
973 /* If the statement is likely to have a VARYING result, then do not
974 bother folding the statement. */
975 else if (likelyvalue
== VARYING
)
976 simplified
= get_rhs (stmt
);
977 /* Otherwise the statement is likely to have an UNDEFINED value and
978 there will be nothing to do. */
980 simplified
= NULL_TREE
;
982 if (simplified
&& is_gimple_min_invariant (simplified
))
984 /* The statement produced a constant value. */
985 val
.lattice_val
= CONSTANT
;
986 val
.const_val
= simplified
;
990 /* The statement produced a nonconstant value. If the statement
991 had undefined or virtual operands, then the result of the
992 statement should be undefined or virtual respectively.
993 Else the result of the statement is VARYING. */
994 val
.lattice_val
= (likelyvalue
== UNDEFINED
? UNDEFINED
: VARYING
);
995 val
.lattice_val
= (likelyvalue
== UNKNOWN_VAL
996 ? UNKNOWN_VAL
: val
.lattice_val
);
997 val
.const_val
= NULL_TREE
;
1004 /* Visit the assignment statement STMT. Set the value of its LHS to the
1005 value computed by the RHS and store LHS in *OUTPUT_P. */
1007 static enum ssa_prop_result
1008 visit_assignment (tree stmt
, tree
*output_p
)
1013 v_must_def_optype v_must_defs
;
1015 lhs
= TREE_OPERAND (stmt
, 0);
1016 rhs
= TREE_OPERAND (stmt
, 1);
1017 vuses
= STMT_VUSE_OPS (stmt
);
1018 v_must_defs
= STMT_V_MUST_DEF_OPS (stmt
);
1020 gcc_assert (NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt
)) == 0);
1021 gcc_assert (NUM_V_MUST_DEFS (v_must_defs
) == 1
1022 || TREE_CODE (lhs
) == SSA_NAME
);
1024 /* We require the SSA version number of the lhs for the value_vector.
1025 Make sure we have it. */
1026 if (TREE_CODE (lhs
) != SSA_NAME
)
1028 /* If we make it here, then stmt only has one definition:
1030 lhs
= V_MUST_DEF_RESULT (v_must_defs
, 0);
1033 if (TREE_CODE (rhs
) == SSA_NAME
)
1035 /* For a simple copy operation, we copy the lattice values. */
1036 value
*nval
= get_value (rhs
);
1039 else if (DECL_P (rhs
)
1040 && NUM_VUSES (vuses
) == 1
1041 && rhs
== SSA_NAME_VAR (VUSE_OP (vuses
, 0)))
1043 /* Same as above, but the rhs is not a gimple register and yet
1044 has a known VUSE. */
1045 value
*nval
= get_value (VUSE_OP (vuses
, 0));
1049 /* Evaluate the statement. */
1050 val
= evaluate_stmt (stmt
);
1052 /* If the original LHS was a VIEW_CONVERT_EXPR, modify the constant
1053 value to be a VIEW_CONVERT_EXPR of the old constant value.
1055 ??? Also, if this was a definition of a bitfield, we need to widen
1056 the constant value into the type of the destination variable. This
1057 should not be necessary if GCC represented bitfields properly. */
1059 tree orig_lhs
= TREE_OPERAND (stmt
, 0);
1061 if (TREE_CODE (orig_lhs
) == VIEW_CONVERT_EXPR
1062 && val
.lattice_val
== CONSTANT
)
1064 tree w
= fold (build1 (VIEW_CONVERT_EXPR
,
1065 TREE_TYPE (TREE_OPERAND (orig_lhs
, 0)),
1068 orig_lhs
= TREE_OPERAND (orig_lhs
, 1);
1069 if (w
&& is_gimple_min_invariant (w
))
1073 val
.lattice_val
= VARYING
;
1074 val
.const_val
= NULL
;
1078 if (val
.lattice_val
== CONSTANT
1079 && TREE_CODE (orig_lhs
) == COMPONENT_REF
1080 && DECL_BIT_FIELD (TREE_OPERAND (orig_lhs
, 1)))
1082 tree w
= widen_bitfield (val
.const_val
, TREE_OPERAND (orig_lhs
, 1),
1085 if (w
&& is_gimple_min_invariant (w
))
1089 val
.lattice_val
= VARYING
;
1090 val
.const_val
= NULL
;
1095 /* If LHS is not a gimple register, then it cannot take on an
1097 if (!is_gimple_reg (SSA_NAME_VAR (lhs
))
1098 && val
.lattice_val
== UNDEFINED
)
1099 val
.lattice_val
= UNKNOWN_VAL
;
1101 /* Set the lattice value of the statement's output. */
1102 if (set_lattice_value (lhs
, val
))
1105 if (val
.lattice_val
== VARYING
)
1106 return SSA_PROP_VARYING
;
1108 return SSA_PROP_INTERESTING
;
1111 return SSA_PROP_NOT_INTERESTING
;
1115 /* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING
1116 if it can determine which edge will be taken. Otherwise, return
1117 SSA_PROP_VARYING. */
1119 static enum ssa_prop_result
1120 visit_cond_stmt (tree stmt
, edge
*taken_edge_p
)
1125 block
= bb_for_stmt (stmt
);
1126 val
= evaluate_stmt (stmt
);
1128 /* Find which edge out of the conditional block will be taken and add it
1129 to the worklist. If no single edge can be determined statically,
1130 return SSA_PROP_VARYING to feed all the outgoing edges to the
1131 propagation engine. */
1132 *taken_edge_p
= val
.const_val
? find_taken_edge (block
, val
.const_val
) : 0;
1134 return SSA_PROP_INTERESTING
;
1136 return SSA_PROP_VARYING
;
1140 /* Evaluate statement STMT. If the statement produces an output value and
1141 its evaluation changes the lattice value of its output, return
1142 SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the
1145 If STMT is a conditional branch and we can determine its truth
1146 value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying
1147 value, return SSA_PROP_VARYING. */
1149 static enum ssa_prop_result
1150 ccp_visit_stmt (tree stmt
, edge
*taken_edge_p
, tree
*output_p
)
1153 v_may_def_optype v_may_defs
;
1154 v_must_def_optype v_must_defs
;
1158 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1160 fprintf (dump_file
, "\nVisiting statement: ");
1161 print_generic_stmt (dump_file
, stmt
, TDF_SLIM
);
1162 fprintf (dump_file
, "\n");
1165 ann
= stmt_ann (stmt
);
1167 v_must_defs
= V_MUST_DEF_OPS (ann
);
1168 v_may_defs
= V_MAY_DEF_OPS (ann
);
1169 if (TREE_CODE (stmt
) == MODIFY_EXPR
1170 && NUM_V_MAY_DEFS (v_may_defs
) == 0
1171 && (NUM_V_MUST_DEFS (v_must_defs
) == 1
1172 || TREE_CODE (TREE_OPERAND (stmt
, 0)) == SSA_NAME
))
1174 /* If the statement is an assignment that produces a single
1175 output value, evaluate its RHS to see if the lattice value of
1176 its output has changed. */
1177 return visit_assignment (stmt
, output_p
);
1179 else if (TREE_CODE (stmt
) == COND_EXPR
|| TREE_CODE (stmt
) == SWITCH_EXPR
)
1181 /* If STMT is a conditional branch, see if we can determine
1182 which branch will be taken. */
1183 return visit_cond_stmt (stmt
, taken_edge_p
);
1186 /* Any other kind of statement is not interesting for constant
1187 propagation and, therefore, not worth simulating. */
1188 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1189 fprintf (dump_file
, "No interesting values produced. Marked VARYING.\n");
1191 /* Definitions made by statements other than assignments to
1192 SSA_NAMEs represent unknown modifications to their outputs.
1193 Mark them VARYING. */
1194 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_DEF
)
1195 def_to_varying (def
);
1197 /* Mark all V_MAY_DEF operands VARYING. */
1198 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_VMAYDEF
)
1199 def_to_varying (def
);
1201 return SSA_PROP_VARYING
;
1205 /* Main entry point for SSA Conditional Constant Propagation.
1207 [ DESCRIBE MAIN ALGORITHM HERE ] */
1210 execute_ssa_ccp (void)
1213 ssa_propagate (ccp_visit_stmt
, ccp_visit_phi_node
);
1221 return flag_tree_ccp
!= 0;
1225 struct tree_opt_pass pass_ccp
=
1228 gate_ccp
, /* gate */
1229 execute_ssa_ccp
, /* execute */
1232 0, /* static_pass_number */
1233 TV_TREE_CCP
, /* tv_id */
1234 PROP_cfg
| PROP_ssa
| PROP_alias
, /* properties_required */
1235 0, /* properties_provided */
1236 0, /* properties_destroyed */
1237 0, /* todo_flags_start */
1238 TODO_cleanup_cfg
| TODO_dump_func
| TODO_rename_vars
1239 | TODO_ggc_collect
| TODO_verify_ssa
1240 | TODO_verify_stmts
, /* todo_flags_finish */
1245 /* Given a constant value VAL for bitfield FIELD, and a destination
1246 variable VAR, return VAL appropriately widened to fit into VAR. If
1247 FIELD is wider than HOST_WIDE_INT, NULL is returned. */
1250 widen_bitfield (tree val
, tree field
, tree var
)
1252 unsigned HOST_WIDE_INT var_size
, field_size
;
1254 unsigned HOST_WIDE_INT mask
;
1257 /* We can only do this if the size of the type and field and VAL are
1258 all constants representable in HOST_WIDE_INT. */
1259 if (!host_integerp (TYPE_SIZE (TREE_TYPE (var
)), 1)
1260 || !host_integerp (DECL_SIZE (field
), 1)
1261 || !host_integerp (val
, 0))
1264 var_size
= tree_low_cst (TYPE_SIZE (TREE_TYPE (var
)), 1);
1265 field_size
= tree_low_cst (DECL_SIZE (field
), 1);
1267 /* Give up if either the bitfield or the variable are too wide. */
1268 if (field_size
> HOST_BITS_PER_WIDE_INT
|| var_size
> HOST_BITS_PER_WIDE_INT
)
1271 gcc_assert (var_size
>= field_size
);
1273 /* If the sign bit of the value is not set or the field's type is unsigned,
1274 just mask off the high order bits of the value. */
1275 if (DECL_UNSIGNED (field
)
1276 || !(tree_low_cst (val
, 0) & (((HOST_WIDE_INT
)1) << (field_size
- 1))))
1278 /* Zero extension. Build a mask with the lower 'field_size' bits
1279 set and a BIT_AND_EXPR node to clear the high order bits of
1281 for (i
= 0, mask
= 0; i
< field_size
; i
++)
1282 mask
|= ((HOST_WIDE_INT
) 1) << i
;
1284 wide_val
= build2 (BIT_AND_EXPR
, TREE_TYPE (var
), val
,
1285 build_int_cst (TREE_TYPE (var
), mask
));
1289 /* Sign extension. Create a mask with the upper 'field_size'
1290 bits set and a BIT_IOR_EXPR to set the high order bits of the
1292 for (i
= 0, mask
= 0; i
< (var_size
- field_size
); i
++)
1293 mask
|= ((HOST_WIDE_INT
) 1) << (var_size
- i
- 1);
1295 wide_val
= build2 (BIT_IOR_EXPR
, TREE_TYPE (var
), val
,
1296 build_int_cst (TREE_TYPE (var
), mask
));
1299 return fold (wide_val
);
1303 /* A subroutine of fold_stmt_r. Attempts to fold *(A+O) to A[X].
1304 BASE is an array type. OFFSET is a byte displacement. ORIG_TYPE
1305 is the desired result type. */
1308 maybe_fold_offset_to_array_ref (tree base
, tree offset
, tree orig_type
)
1310 tree min_idx
, idx
, elt_offset
= integer_zero_node
;
1311 tree array_type
, elt_type
, elt_size
;
1313 /* If BASE is an ARRAY_REF, we can pick up another offset (this time
1314 measured in units of the size of elements type) from that ARRAY_REF).
1315 We can't do anything if either is variable.
1317 The case we handle here is *(&A[N]+O). */
1318 if (TREE_CODE (base
) == ARRAY_REF
)
1320 tree low_bound
= array_ref_low_bound (base
);
1322 elt_offset
= TREE_OPERAND (base
, 1);
1323 if (TREE_CODE (low_bound
) != INTEGER_CST
1324 || TREE_CODE (elt_offset
) != INTEGER_CST
)
1327 elt_offset
= int_const_binop (MINUS_EXPR
, elt_offset
, low_bound
, 0);
1328 base
= TREE_OPERAND (base
, 0);
1331 /* Ignore stupid user tricks of indexing non-array variables. */
1332 array_type
= TREE_TYPE (base
);
1333 if (TREE_CODE (array_type
) != ARRAY_TYPE
)
1335 elt_type
= TREE_TYPE (array_type
);
1336 if (!lang_hooks
.types_compatible_p (orig_type
, elt_type
))
1339 /* If OFFSET and ELT_OFFSET are zero, we don't care about the size of the
1340 element type (so we can use the alignment if it's not constant).
1341 Otherwise, compute the offset as an index by using a division. If the
1342 division isn't exact, then don't do anything. */
1343 elt_size
= TYPE_SIZE_UNIT (elt_type
);
1344 if (integer_zerop (offset
))
1346 if (TREE_CODE (elt_size
) != INTEGER_CST
)
1347 elt_size
= size_int (TYPE_ALIGN (elt_type
));
1349 idx
= integer_zero_node
;
1353 unsigned HOST_WIDE_INT lquo
, lrem
;
1354 HOST_WIDE_INT hquo
, hrem
;
1356 if (TREE_CODE (elt_size
) != INTEGER_CST
1357 || div_and_round_double (TRUNC_DIV_EXPR
, 1,
1358 TREE_INT_CST_LOW (offset
),
1359 TREE_INT_CST_HIGH (offset
),
1360 TREE_INT_CST_LOW (elt_size
),
1361 TREE_INT_CST_HIGH (elt_size
),
1362 &lquo
, &hquo
, &lrem
, &hrem
)
1366 idx
= build_int_cst_wide (NULL_TREE
, lquo
, hquo
);
1369 /* Assume the low bound is zero. If there is a domain type, get the
1370 low bound, if any, convert the index into that type, and add the
1372 min_idx
= integer_zero_node
;
1373 if (TYPE_DOMAIN (array_type
))
1375 if (TYPE_MIN_VALUE (TYPE_DOMAIN (array_type
)))
1376 min_idx
= TYPE_MIN_VALUE (TYPE_DOMAIN (array_type
));
1378 min_idx
= fold_convert (TYPE_DOMAIN (array_type
), min_idx
);
1380 if (TREE_CODE (min_idx
) != INTEGER_CST
)
1383 idx
= fold_convert (TYPE_DOMAIN (array_type
), idx
);
1384 elt_offset
= fold_convert (TYPE_DOMAIN (array_type
), elt_offset
);
1387 if (!integer_zerop (min_idx
))
1388 idx
= int_const_binop (PLUS_EXPR
, idx
, min_idx
, 0);
1389 if (!integer_zerop (elt_offset
))
1390 idx
= int_const_binop (PLUS_EXPR
, idx
, elt_offset
, 0);
1392 return build (ARRAY_REF
, orig_type
, base
, idx
, min_idx
,
1393 size_int (tree_low_cst (elt_size
, 1)
1394 / (TYPE_ALIGN_UNIT (elt_type
))));
1398 /* A subroutine of fold_stmt_r. Attempts to fold *(S+O) to S.X.
1399 BASE is a record type. OFFSET is a byte displacement. ORIG_TYPE
1400 is the desired result type. */
1401 /* ??? This doesn't handle class inheritance. */
1404 maybe_fold_offset_to_component_ref (tree record_type
, tree base
, tree offset
,
1405 tree orig_type
, bool base_is_ptr
)
1407 tree f
, t
, field_type
, tail_array_field
, field_offset
;
1409 if (TREE_CODE (record_type
) != RECORD_TYPE
1410 && TREE_CODE (record_type
) != UNION_TYPE
1411 && TREE_CODE (record_type
) != QUAL_UNION_TYPE
)
1414 /* Short-circuit silly cases. */
1415 if (lang_hooks
.types_compatible_p (record_type
, orig_type
))
1418 tail_array_field
= NULL_TREE
;
1419 for (f
= TYPE_FIELDS (record_type
); f
; f
= TREE_CHAIN (f
))
1423 if (TREE_CODE (f
) != FIELD_DECL
)
1425 if (DECL_BIT_FIELD (f
))
1428 field_offset
= byte_position (f
);
1429 if (TREE_CODE (field_offset
) != INTEGER_CST
)
1432 /* ??? Java creates "interesting" fields for representing base classes.
1433 They have no name, and have no context. With no context, we get into
1434 trouble with nonoverlapping_component_refs_p. Skip them. */
1435 if (!DECL_FIELD_CONTEXT (f
))
1438 /* The previous array field isn't at the end. */
1439 tail_array_field
= NULL_TREE
;
1441 /* Check to see if this offset overlaps with the field. */
1442 cmp
= tree_int_cst_compare (field_offset
, offset
);
1446 field_type
= TREE_TYPE (f
);
1448 /* Here we exactly match the offset being checked. If the types match,
1449 then we can return that field. */
1451 && lang_hooks
.types_compatible_p (orig_type
, field_type
))
1454 base
= build1 (INDIRECT_REF
, record_type
, base
);
1455 t
= build (COMPONENT_REF
, field_type
, base
, f
, NULL_TREE
);
1459 /* Don't care about offsets into the middle of scalars. */
1460 if (!AGGREGATE_TYPE_P (field_type
))
1463 /* Check for array at the end of the struct. This is often
1464 used as for flexible array members. We should be able to
1465 turn this into an array access anyway. */
1466 if (TREE_CODE (field_type
) == ARRAY_TYPE
)
1467 tail_array_field
= f
;
1469 /* Check the end of the field against the offset. */
1470 if (!DECL_SIZE_UNIT (f
)
1471 || TREE_CODE (DECL_SIZE_UNIT (f
)) != INTEGER_CST
)
1473 t
= int_const_binop (MINUS_EXPR
, offset
, field_offset
, 1);
1474 if (!tree_int_cst_lt (t
, DECL_SIZE_UNIT (f
)))
1477 /* If we matched, then set offset to the displacement into
1483 if (!tail_array_field
)
1486 f
= tail_array_field
;
1487 field_type
= TREE_TYPE (f
);
1488 offset
= int_const_binop (MINUS_EXPR
, offset
, byte_position (f
), 1);
1491 /* If we get here, we've got an aggregate field, and a possibly
1492 nonzero offset into them. Recurse and hope for a valid match. */
1494 base
= build1 (INDIRECT_REF
, record_type
, base
);
1495 base
= build (COMPONENT_REF
, field_type
, base
, f
, NULL_TREE
);
1497 t
= maybe_fold_offset_to_array_ref (base
, offset
, orig_type
);
1500 return maybe_fold_offset_to_component_ref (field_type
, base
, offset
,
1505 /* A subroutine of fold_stmt_r. Attempt to simplify *(BASE+OFFSET).
1506 Return the simplified expression, or NULL if nothing could be done. */
1509 maybe_fold_stmt_indirect (tree expr
, tree base
, tree offset
)
1513 /* We may well have constructed a double-nested PLUS_EXPR via multiple
1514 substitutions. Fold that down to one. Remove NON_LVALUE_EXPRs that
1515 are sometimes added. */
1518 TREE_OPERAND (expr
, 0) = base
;
1520 /* One possibility is that the address reduces to a string constant. */
1521 t
= fold_read_from_constant_string (expr
);
1525 /* Add in any offset from a PLUS_EXPR. */
1526 if (TREE_CODE (base
) == PLUS_EXPR
)
1530 offset2
= TREE_OPERAND (base
, 1);
1531 if (TREE_CODE (offset2
) != INTEGER_CST
)
1533 base
= TREE_OPERAND (base
, 0);
1535 offset
= int_const_binop (PLUS_EXPR
, offset
, offset2
, 1);
1538 if (TREE_CODE (base
) == ADDR_EXPR
)
1540 /* Strip the ADDR_EXPR. */
1541 base
= TREE_OPERAND (base
, 0);
1543 /* Fold away CONST_DECL to its value, if the type is scalar. */
1544 if (TREE_CODE (base
) == CONST_DECL
1545 && is_gimple_min_invariant (DECL_INITIAL (base
)))
1546 return DECL_INITIAL (base
);
1548 /* Try folding *(&B+O) to B[X]. */
1549 t
= maybe_fold_offset_to_array_ref (base
, offset
, TREE_TYPE (expr
));
1553 /* Try folding *(&B+O) to B.X. */
1554 t
= maybe_fold_offset_to_component_ref (TREE_TYPE (base
), base
, offset
,
1555 TREE_TYPE (expr
), false);
1559 /* Fold *&B to B. We can only do this if EXPR is the same type
1560 as BASE. We can't do this if EXPR is the element type of an array
1561 and BASE is the array. */
1562 if (integer_zerop (offset
)
1563 && lang_hooks
.types_compatible_p (TREE_TYPE (base
),
1569 /* We can get here for out-of-range string constant accesses,
1570 such as "_"[3]. Bail out of the entire substitution search
1571 and arrange for the entire statement to be replaced by a
1572 call to __builtin_trap. In all likelihood this will all be
1573 constant-folded away, but in the meantime we can't leave with
1574 something that get_expr_operands can't understand. */
1578 if (TREE_CODE (t
) == ADDR_EXPR
1579 && TREE_CODE (TREE_OPERAND (t
, 0)) == STRING_CST
)
1581 /* FIXME: Except that this causes problems elsewhere with dead
1582 code not being deleted, and we abort in the rtl expanders
1583 because we failed to remove some ssa_name. In the meantime,
1584 just return zero. */
1585 /* FIXME2: This condition should be signaled by
1586 fold_read_from_constant_string directly, rather than
1587 re-checking for it here. */
1588 return integer_zero_node
;
1591 /* Try folding *(B+O) to B->X. Still an improvement. */
1592 if (POINTER_TYPE_P (TREE_TYPE (base
)))
1594 t
= maybe_fold_offset_to_component_ref (TREE_TYPE (TREE_TYPE (base
)),
1596 TREE_TYPE (expr
), true);
1602 /* Otherwise we had an offset that we could not simplify. */
1607 /* A subroutine of fold_stmt_r. EXPR is a PLUS_EXPR.
1609 A quaint feature extant in our address arithmetic is that there
1610 can be hidden type changes here. The type of the result need
1611 not be the same as the type of the input pointer.
1613 What we're after here is an expression of the form
1614 (T *)(&array + const)
1615 where the cast doesn't actually exist, but is implicit in the
1616 type of the PLUS_EXPR. We'd like to turn this into
1618 which may be able to propagate further. */
1621 maybe_fold_stmt_addition (tree expr
)
1623 tree op0
= TREE_OPERAND (expr
, 0);
1624 tree op1
= TREE_OPERAND (expr
, 1);
1625 tree ptr_type
= TREE_TYPE (expr
);
1628 bool subtract
= (TREE_CODE (expr
) == MINUS_EXPR
);
1630 /* We're only interested in pointer arithmetic. */
1631 if (!POINTER_TYPE_P (ptr_type
))
1633 /* Canonicalize the integral operand to op1. */
1634 if (INTEGRAL_TYPE_P (TREE_TYPE (op0
)))
1638 t
= op0
, op0
= op1
, op1
= t
;
1640 /* It had better be a constant. */
1641 if (TREE_CODE (op1
) != INTEGER_CST
)
1643 /* The first operand should be an ADDR_EXPR. */
1644 if (TREE_CODE (op0
) != ADDR_EXPR
)
1646 op0
= TREE_OPERAND (op0
, 0);
1648 /* If the first operand is an ARRAY_REF, expand it so that we can fold
1649 the offset into it. */
1650 while (TREE_CODE (op0
) == ARRAY_REF
)
1652 tree array_obj
= TREE_OPERAND (op0
, 0);
1653 tree array_idx
= TREE_OPERAND (op0
, 1);
1654 tree elt_type
= TREE_TYPE (op0
);
1655 tree elt_size
= TYPE_SIZE_UNIT (elt_type
);
1658 if (TREE_CODE (array_idx
) != INTEGER_CST
)
1660 if (TREE_CODE (elt_size
) != INTEGER_CST
)
1663 /* Un-bias the index by the min index of the array type. */
1664 min_idx
= TYPE_DOMAIN (TREE_TYPE (array_obj
));
1667 min_idx
= TYPE_MIN_VALUE (min_idx
);
1670 if (TREE_CODE (min_idx
) != INTEGER_CST
)
1673 array_idx
= convert (TREE_TYPE (min_idx
), array_idx
);
1674 if (!integer_zerop (min_idx
))
1675 array_idx
= int_const_binop (MINUS_EXPR
, array_idx
,
1680 /* Convert the index to a byte offset. */
1681 array_idx
= convert (sizetype
, array_idx
);
1682 array_idx
= int_const_binop (MULT_EXPR
, array_idx
, elt_size
, 0);
1684 /* Update the operands for the next round, or for folding. */
1685 /* If we're manipulating unsigned types, then folding into negative
1686 values can produce incorrect results. Particularly if the type
1687 is smaller than the width of the pointer. */
1689 && TYPE_UNSIGNED (TREE_TYPE (op1
))
1690 && tree_int_cst_lt (array_idx
, op1
))
1692 op1
= int_const_binop (subtract
? MINUS_EXPR
: PLUS_EXPR
,
1698 /* If we weren't able to fold the subtraction into another array reference,
1699 canonicalize the integer for passing to the array and component ref
1700 simplification functions. */
1703 if (TYPE_UNSIGNED (TREE_TYPE (op1
)))
1705 op1
= fold (build1 (NEGATE_EXPR
, TREE_TYPE (op1
), op1
));
1706 /* ??? In theory fold should always produce another integer. */
1707 if (TREE_CODE (op1
) != INTEGER_CST
)
1711 ptd_type
= TREE_TYPE (ptr_type
);
1713 /* At which point we can try some of the same things as for indirects. */
1714 t
= maybe_fold_offset_to_array_ref (op0
, op1
, ptd_type
);
1716 t
= maybe_fold_offset_to_component_ref (TREE_TYPE (op0
), op0
, op1
,
1719 t
= build1 (ADDR_EXPR
, ptr_type
, t
);
1725 /* Subroutine of fold_stmt called via walk_tree. We perform several
1726 simplifications of EXPR_P, mostly having to do with pointer arithmetic. */
1729 fold_stmt_r (tree
*expr_p
, int *walk_subtrees
, void *data
)
1731 bool *changed_p
= data
;
1732 tree expr
= *expr_p
, t
;
1734 /* ??? It'd be nice if walk_tree had a pre-order option. */
1735 switch (TREE_CODE (expr
))
1738 t
= walk_tree (&TREE_OPERAND (expr
, 0), fold_stmt_r
, data
, NULL
);
1743 t
= maybe_fold_stmt_indirect (expr
, TREE_OPERAND (expr
, 0),
1747 /* ??? Could handle ARRAY_REF here, as a variant of INDIRECT_REF.
1748 We'd only want to bother decomposing an existing ARRAY_REF if
1749 the base array is found to have another offset contained within.
1750 Otherwise we'd be wasting time. */
1753 t
= walk_tree (&TREE_OPERAND (expr
, 0), fold_stmt_r
, data
, NULL
);
1758 /* Set TREE_INVARIANT properly so that the value is properly
1759 considered constant, and so gets propagated as expected. */
1761 recompute_tree_invarant_for_addr_expr (expr
);
1766 t
= walk_tree (&TREE_OPERAND (expr
, 0), fold_stmt_r
, data
, NULL
);
1769 t
= walk_tree (&TREE_OPERAND (expr
, 1), fold_stmt_r
, data
, NULL
);
1774 t
= maybe_fold_stmt_addition (expr
);
1778 t
= walk_tree (&TREE_OPERAND (expr
, 0), fold_stmt_r
, data
, NULL
);
1783 /* Make sure the FIELD_DECL is actually a field in the type on the lhs.
1784 We've already checked that the records are compatible, so we should
1785 come up with a set of compatible fields. */
1787 tree expr_record
= TREE_TYPE (TREE_OPERAND (expr
, 0));
1788 tree expr_field
= TREE_OPERAND (expr
, 1);
1790 if (DECL_FIELD_CONTEXT (expr_field
) != TYPE_MAIN_VARIANT (expr_record
))
1792 expr_field
= find_compatible_field (expr_record
, expr_field
);
1793 TREE_OPERAND (expr
, 1) = expr_field
;
1812 /* Return the string length of ARG in LENGTH. If ARG is an SSA name variable,
1813 follow its use-def chains. If LENGTH is not NULL and its value is not
1814 equal to the length we determine, or if we are unable to determine the
1815 length, return false. VISITED is a bitmap of visited variables. */
1818 get_strlen (tree arg
, tree
*length
, bitmap visited
)
1820 tree var
, def_stmt
, val
;
1822 if (TREE_CODE (arg
) != SSA_NAME
)
1824 val
= c_strlen (arg
, 1);
1828 if (*length
&& simple_cst_equal (val
, *length
) != 1)
1835 /* If we were already here, break the infinite cycle. */
1836 if (bitmap_bit_p (visited
, SSA_NAME_VERSION (arg
)))
1838 bitmap_set_bit (visited
, SSA_NAME_VERSION (arg
));
1841 def_stmt
= SSA_NAME_DEF_STMT (var
);
1843 switch (TREE_CODE (def_stmt
))
1849 /* The RHS of the statement defining VAR must either have a
1850 constant length or come from another SSA_NAME with a constant
1852 rhs
= TREE_OPERAND (def_stmt
, 1);
1854 if (TREE_CODE (rhs
) == SSA_NAME
)
1855 return get_strlen (rhs
, length
, visited
);
1857 /* See if the RHS is a constant length. */
1858 len
= c_strlen (rhs
, 1);
1861 if (*length
&& simple_cst_equal (len
, *length
) != 1)
1873 /* All the arguments of the PHI node must have the same constant
1877 for (i
= 0; i
< PHI_NUM_ARGS (def_stmt
); i
++)
1879 tree arg
= PHI_ARG_DEF (def_stmt
, i
);
1881 /* If this PHI has itself as an argument, we cannot
1882 determine the string length of this argument. However,
1883 if we can find a constant string length for the other
1884 PHI args then we can still be sure that this is a
1885 constant string length. So be optimistic and just
1886 continue with the next argument. */
1887 if (arg
== PHI_RESULT (def_stmt
))
1890 if (!get_strlen (arg
, length
, visited
))
1906 /* Fold builtin call FN in statement STMT. If it cannot be folded into a
1907 constant, return NULL_TREE. Otherwise, return its constant value. */
1910 ccp_fold_builtin (tree stmt
, tree fn
)
1912 tree result
, strlen_val
[2];
1913 tree callee
, arglist
, a
;
1918 ignore
= TREE_CODE (stmt
) != MODIFY_EXPR
;
1920 /* First try the generic builtin folder. If that succeeds, return the
1922 callee
= get_callee_fndecl (fn
);
1923 arglist
= TREE_OPERAND (fn
, 1);
1924 result
= fold_builtin (callee
, arglist
, ignore
);
1928 STRIP_NOPS (result
);
1932 /* Ignore MD builtins. */
1933 if (DECL_BUILT_IN_CLASS (callee
) == BUILT_IN_MD
)
1936 /* If the builtin could not be folded, and it has no argument list,
1941 /* Limit the work only for builtins we know how to simplify. */
1942 switch (DECL_FUNCTION_CODE (callee
))
1944 case BUILT_IN_STRLEN
:
1945 case BUILT_IN_FPUTS
:
1946 case BUILT_IN_FPUTS_UNLOCKED
:
1949 case BUILT_IN_STRCPY
:
1950 case BUILT_IN_STRNCPY
:
1957 /* Try to use the dataflow information gathered by the CCP process. */
1958 visited
= BITMAP_ALLOC (NULL
);
1960 memset (strlen_val
, 0, sizeof (strlen_val
));
1961 for (i
= 0, a
= arglist
;
1963 i
++, strlen_arg
>>= 1, a
= TREE_CHAIN (a
))
1966 bitmap_clear (visited
);
1967 if (!get_strlen (TREE_VALUE (a
), &strlen_val
[i
], visited
))
1968 strlen_val
[i
] = NULL_TREE
;
1971 BITMAP_FREE (visited
);
1974 switch (DECL_FUNCTION_CODE (callee
))
1976 case BUILT_IN_STRLEN
:
1979 tree
new = fold_convert (TREE_TYPE (fn
), strlen_val
[0]);
1981 /* If the result is not a valid gimple value, or not a cast
1982 of a valid gimple value, then we can not use the result. */
1983 if (is_gimple_val (new)
1984 || (is_gimple_cast (new)
1985 && is_gimple_val (TREE_OPERAND (new, 0))))
1990 case BUILT_IN_STRCPY
:
1991 if (strlen_val
[1] && is_gimple_val (strlen_val
[1]))
1993 tree fndecl
= get_callee_fndecl (fn
);
1994 tree arglist
= TREE_OPERAND (fn
, 1);
1995 result
= fold_builtin_strcpy (fndecl
, arglist
, strlen_val
[1]);
1999 case BUILT_IN_STRNCPY
:
2000 if (strlen_val
[1] && is_gimple_val (strlen_val
[1]))
2002 tree fndecl
= get_callee_fndecl (fn
);
2003 tree arglist
= TREE_OPERAND (fn
, 1);
2004 result
= fold_builtin_strncpy (fndecl
, arglist
, strlen_val
[1]);
2008 case BUILT_IN_FPUTS
:
2009 result
= fold_builtin_fputs (arglist
,
2010 TREE_CODE (stmt
) != MODIFY_EXPR
, 0,
2014 case BUILT_IN_FPUTS_UNLOCKED
:
2015 result
= fold_builtin_fputs (arglist
,
2016 TREE_CODE (stmt
) != MODIFY_EXPR
, 1,
2024 if (result
&& ignore
)
2025 result
= fold_ignored_result (result
);
2030 /* Fold the statement pointed by STMT_P. In some cases, this function may
2031 replace the whole statement with a new one. Returns true iff folding
2032 makes any changes. */
2035 fold_stmt (tree
*stmt_p
)
2037 tree rhs
, result
, stmt
;
2038 bool changed
= false;
2042 /* If we replaced constants and the statement makes pointer dereferences,
2043 then we may need to fold instances of *&VAR into VAR, etc. */
2044 if (walk_tree (stmt_p
, fold_stmt_r
, &changed
, NULL
))
2047 = build_function_call_expr (implicit_built_in_decls
[BUILT_IN_TRAP
],
2052 rhs
= get_rhs (stmt
);
2057 if (TREE_CODE (rhs
) == CALL_EXPR
)
2061 /* Check for builtins that CCP can handle using information not
2062 available in the generic fold routines. */
2063 callee
= get_callee_fndecl (rhs
);
2064 if (callee
&& DECL_BUILT_IN (callee
))
2065 result
= ccp_fold_builtin (stmt
, rhs
);
2068 /* Check for resolvable OBJ_TYPE_REF. The only sorts we can resolve
2069 here are when we've propagated the address of a decl into the
2071 /* ??? Should perhaps do this in fold proper. However, doing it
2072 there requires that we create a new CALL_EXPR, and that requires
2073 copying EH region info to the new node. Easier to just do it
2074 here where we can just smash the call operand. */
2075 callee
= TREE_OPERAND (rhs
, 0);
2076 if (TREE_CODE (callee
) == OBJ_TYPE_REF
2077 && lang_hooks
.fold_obj_type_ref
2078 && TREE_CODE (OBJ_TYPE_REF_OBJECT (callee
)) == ADDR_EXPR
2079 && DECL_P (TREE_OPERAND
2080 (OBJ_TYPE_REF_OBJECT (callee
), 0)))
2084 /* ??? Caution: Broken ADDR_EXPR semantics means that
2085 looking at the type of the operand of the addr_expr
2086 can yield an array type. See silly exception in
2087 check_pointer_types_r. */
2089 t
= TREE_TYPE (TREE_TYPE (OBJ_TYPE_REF_OBJECT (callee
)));
2090 t
= lang_hooks
.fold_obj_type_ref (callee
, t
);
2093 TREE_OPERAND (rhs
, 0) = t
;
2100 /* If we couldn't fold the RHS, hand over to the generic fold routines. */
2101 if (result
== NULL_TREE
)
2102 result
= fold (rhs
);
2104 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
2105 may have been added by fold, and "useless" type conversions that might
2106 now be apparent due to propagation. */
2107 STRIP_USELESS_TYPE_CONVERSION (result
);
2110 changed
|= set_rhs (stmt_p
, result
);
2116 /* Convert EXPR into a GIMPLE value suitable for substitution on the
2117 RHS of an assignment. Insert the necessary statements before
2121 convert_to_gimple_builtin (block_stmt_iterator
*si_p
, tree expr
)
2123 tree_stmt_iterator ti
;
2124 tree stmt
= bsi_stmt (*si_p
);
2125 tree tmp
, stmts
= NULL
;
2127 push_gimplify_context ();
2128 tmp
= get_initialized_tmp_var (expr
, &stmts
, NULL
);
2129 pop_gimplify_context (NULL
);
2131 /* The replacement can expose previously unreferenced variables. */
2132 for (ti
= tsi_start (stmts
); !tsi_end_p (ti
); tsi_next (&ti
))
2134 find_new_referenced_vars (tsi_stmt_ptr (ti
));
2135 mark_new_vars_to_rename (tsi_stmt (ti
), vars_to_rename
);
2138 if (EXPR_HAS_LOCATION (stmt
))
2139 annotate_all_with_locus (&stmts
, EXPR_LOCATION (stmt
));
2141 bsi_insert_before (si_p
, stmts
, BSI_SAME_STMT
);
2147 /* A simple pass that attempts to fold all builtin functions. This pass
2148 is run after we've propagated as many constants as we can. */
2151 execute_fold_all_builtins (void)
2153 bool cfg_changed
= false;
2157 block_stmt_iterator i
;
2158 for (i
= bsi_start (bb
); !bsi_end_p (i
); bsi_next (&i
))
2160 tree
*stmtp
= bsi_stmt_ptr (i
);
2161 tree call
= get_rhs (*stmtp
);
2162 tree callee
, result
;
2164 if (!call
|| TREE_CODE (call
) != CALL_EXPR
)
2166 callee
= get_callee_fndecl (call
);
2167 if (!callee
|| DECL_BUILT_IN_CLASS (callee
) != BUILT_IN_NORMAL
)
2170 result
= ccp_fold_builtin (*stmtp
, call
);
2172 switch (DECL_FUNCTION_CODE (callee
))
2174 case BUILT_IN_CONSTANT_P
:
2175 /* Resolve __builtin_constant_p. If it hasn't been
2176 folded to integer_one_node by now, it's fairly
2177 certain that the value simply isn't constant. */
2178 result
= integer_zero_node
;
2185 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2187 fprintf (dump_file
, "Simplified\n ");
2188 print_generic_stmt (dump_file
, *stmtp
, dump_flags
);
2191 if (!set_rhs (stmtp
, result
))
2193 result
= convert_to_gimple_builtin (&i
, result
);
2196 bool ok
= set_rhs (stmtp
, result
);
2201 update_stmt (*stmtp
);
2202 if (maybe_clean_eh_stmt (*stmtp
)
2203 && tree_purge_dead_eh_edges (bb
))
2206 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2208 fprintf (dump_file
, "to\n ");
2209 print_generic_stmt (dump_file
, *stmtp
, dump_flags
);
2210 fprintf (dump_file
, "\n");
2215 /* Delete unreachable blocks. */
2217 cleanup_tree_cfg ();
2221 struct tree_opt_pass pass_fold_builtins
=
2225 execute_fold_all_builtins
, /* execute */
2228 0, /* static_pass_number */
2230 PROP_cfg
| PROP_ssa
| PROP_alias
, /* properties_required */
2231 0, /* properties_provided */
2232 0, /* properties_destroyed */
2233 0, /* todo_flags_start */
2236 | TODO_rename_vars
, /* todo_flags_finish */