1 /* Conditional constant propagation pass for the GNU compiler.
2 Copyright (C) 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
3 Adapted from original RTL SSA-CCP by Daniel Berlin <dberlin@dberlin.org>
4 Adapted to GIMPLE trees by Diego Novillo <dnovillo@redhat.com>
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it
9 under the terms of the GNU General Public License as published by the
10 Free Software Foundation; either version 2, or (at your option) any
13 GCC is distributed in the hope that it will be useful, but WITHOUT
14 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING. If not, write to the Free
20 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
23 /* Conditional constant propagation.
27 Constant propagation with conditional branches,
28 Wegman and Zadeck, ACM TOPLAS 13(2):181-210.
30 Building an Optimizing Compiler,
31 Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9.
33 Advanced Compiler Design and Implementation,
34 Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */
38 #include "coretypes.h"
43 #include "langhooks.h"
45 /* These RTL headers are needed for basic-block.h. */
48 #include "hard-reg-set.h"
49 #include "basic-block.h"
51 #include "diagnostic.h"
52 #include "tree-inline.h"
53 #include "tree-flow.h"
54 #include "tree-gimple.h"
55 #include "tree-dump.h"
56 #include "tree-pass.h"
62 /* Possible lattice values. */
71 /* Use the TREE_VISITED bitflag to mark statements and PHI nodes that have
72 been deemed VARYING and shouldn't be simulated again. */
73 #define DONT_SIMULATE_AGAIN(T) TREE_VISITED (T)
75 /* Main structure for CCP. Contains the lattice value and, if it's a
76 constant, the constant value. */
79 latticevalue lattice_val;
83 /* A bitmap to keep track of executable blocks in the CFG. */
84 static sbitmap executable_blocks;
86 /* Array of control flow edges on the worklist. */
87 static GTY(()) varray_type cfg_blocks = NULL;
89 static unsigned int cfg_blocks_num = 0;
90 static int cfg_blocks_tail;
91 static int cfg_blocks_head;
93 static sbitmap bb_in_list;
95 /* This is used to track the current value of each variable. */
96 static value *value_vector;
98 /* Worklist of SSA edges which will need reexamination as their definition
99 has changed. SSA edges are def-use edges in the SSA web. For each
100 edge, we store the definition statement or PHI node D. The destination
101 nodes that need to be visited are accessed using immediate_uses
103 static GTY(()) varray_type ssa_edges;
105 /* Identical to SSA_EDGES. For performance reasons, the list of SSA
106 edges is split into two. One contains all SSA edges who need to be
107 reexamined because their lattice value changed to varying (this
108 worklist), and the other contains all other SSA edges to be
109 reexamined (ssa_edges).
111 Since most values in the program are varying, the ideal situation
112 is to move them to that lattice value as quickly as possible.
113 Thus, it doesn't make sense to process any other type of lattice
114 value until all varying values are propagated fully, which is one
115 thing using the varying worklist achieves. In addition, if you
116 don't use a separate worklist for varying edges, you end up with
117 situations where lattice values move from
118 undefined->constant->varying instead of undefined->varying.
120 static GTY(()) varray_type varying_ssa_edges;
123 static void initialize (void);
124 static void finalize (void);
125 static void visit_phi_node (tree);
126 static tree ccp_fold (tree);
127 static value cp_lattice_meet (value, value);
128 static void visit_stmt (tree);
129 static void visit_cond_stmt (tree);
130 static void visit_assignment (tree);
131 static void add_var_to_ssa_edges_worklist (tree, value);
132 static void add_outgoing_control_edges (basic_block);
133 static void add_control_edge (edge);
134 static void def_to_varying (tree);
135 static void set_lattice_value (tree, value);
136 static void simulate_block (basic_block);
137 static void simulate_stmt (tree);
138 static void substitute_and_fold (void);
139 static value evaluate_stmt (tree);
140 static void dump_lattice_value (FILE *, const char *, value);
141 static bool replace_uses_in (tree, bool *);
142 static latticevalue likely_value (tree);
143 static tree get_rhs (tree);
144 static void set_rhs (tree *, tree);
145 static value *get_value (tree);
146 static value get_default_value (tree);
147 static tree ccp_fold_builtin (tree, tree);
148 static bool get_strlen (tree, tree *, bitmap);
149 static inline bool cfg_blocks_empty_p (void);
150 static void cfg_blocks_add (basic_block);
151 static basic_block cfg_blocks_get (void);
152 static bool need_imm_uses_for (tree var);
154 /* Process an SSA edge worklist. WORKLIST is the SSA edge worklist to
155 drain. This pops statements off the given WORKLIST and processes
156 them until there are no more statements on WORKLIST. */
159 process_ssa_edge_worklist (varray_type *worklist)
161 /* Drain the entire worklist. */
162 while (VARRAY_ACTIVE_SIZE (*worklist) > 0)
164 /* Pull the statement to simulate off the worklist. */
165 tree stmt = VARRAY_TOP_TREE (*worklist);
166 stmt_ann_t ann = stmt_ann (stmt);
167 VARRAY_POP (*worklist);
169 /* visit_stmt can "cancel" reevaluation of some statements.
170 If it does, then in_ccp_worklist will be zero. */
171 if (ann->in_ccp_worklist)
173 ann->in_ccp_worklist = 0;
174 simulate_stmt (stmt);
179 /* Main entry point for SSA Conditional Constant Propagation. FNDECL is
180 the declaration for the function to optimize.
182 On exit, VARS_TO_RENAME will contain the symbols that have been exposed by
183 the propagation of ADDR_EXPR expressions into pointer dereferences and need
184 to be renamed into SSA.
186 PHASE indicates which dump file from the DUMP_FILES array to use when
187 dumping debugging information. */
194 /* Iterate until the worklists are empty. */
195 while (!cfg_blocks_empty_p ()
196 || VARRAY_ACTIVE_SIZE (ssa_edges) > 0
197 || VARRAY_ACTIVE_SIZE (varying_ssa_edges) > 0)
199 if (!cfg_blocks_empty_p ())
201 /* Pull the next block to simulate off the worklist. */
202 basic_block dest_block = cfg_blocks_get ();
203 simulate_block (dest_block);
206 /* In order to move things to varying as quickly as
207 possible,process the VARYING_SSA_EDGES worklist first. */
208 process_ssa_edge_worklist (&varying_ssa_edges);
210 /* Now process the SSA_EDGES worklist. */
211 process_ssa_edge_worklist (&ssa_edges);
214 /* Now perform substitutions based on the known constant values. */
215 substitute_and_fold ();
217 /* Now cleanup any unreachable code. */
220 /* Free allocated memory. */
223 /* Debugging dumps. */
224 if (dump_file && (dump_flags & TDF_DETAILS))
226 dump_referenced_vars (dump_file);
227 fprintf (dump_file, "\n\n");
234 return flag_tree_ccp != 0;
237 struct tree_opt_pass pass_ccp =
241 tree_ssa_ccp, /* execute */
244 0, /* static_pass_number */
245 TV_TREE_CCP, /* tv_id */
246 PROP_cfg | PROP_ssa, /* properties_required */
247 0, /* properties_provided */
248 0, /* properties_destroyed */
249 0, /* todo_flags_start */
250 TODO_dump_func | TODO_rename_vars
251 | TODO_ggc_collect | TODO_verify_ssa /* todo_flags_finish */
255 /* Get the constant value associated with variable VAR. */
262 #if defined ENABLE_CHECKING
263 if (TREE_CODE (var) != SSA_NAME)
267 val = &value_vector[SSA_NAME_VERSION (var)];
268 if (val->lattice_val == UNINITIALIZED)
269 *val = get_default_value (var);
275 /* Simulate the execution of BLOCK. Evaluate the statement associated
276 with each variable reference inside the block. */
279 simulate_block (basic_block block)
283 /* There is nothing to do for the exit block. */
284 if (block == EXIT_BLOCK_PTR)
287 if (dump_file && (dump_flags & TDF_DETAILS))
288 fprintf (dump_file, "\nSimulating block %d\n", block->index);
290 /* Always simulate PHI nodes, even if we have simulated this block
292 for (phi = phi_nodes (block); phi; phi = PHI_CHAIN (phi))
293 visit_phi_node (phi);
295 /* If this is the first time we've simulated this block, then we
296 must simulate each of its statements. */
297 if (!TEST_BIT (executable_blocks, block->index))
299 block_stmt_iterator j;
300 unsigned int normal_edge_count;
303 /* Note that we have simulated this block. */
304 SET_BIT (executable_blocks, block->index);
306 for (j = bsi_start (block); !bsi_end_p (j); bsi_next (&j))
307 visit_stmt (bsi_stmt (j));
309 /* We can not predict when abnormal edges will be executed, so
310 once a block is considered executable, we consider any
311 outgoing abnormal edges as executable.
313 At the same time, if this block has only one successor that is
314 reached by non-abnormal edges, then add that successor to the
316 normal_edge_count = 0;
318 for (e = block->succ; e; e = e->succ_next)
320 if (e->flags & EDGE_ABNORMAL)
322 add_control_edge (e);
331 if (normal_edge_count == 1)
332 add_control_edge (normal_edge);
337 /* Follow the def-use edges for statement DEF_STMT and simulate all the
338 statements reached by it. */
341 simulate_stmt (tree use_stmt)
343 basic_block use_bb = bb_for_stmt (use_stmt);
345 if (dump_file && (dump_flags & TDF_DETAILS))
347 fprintf (dump_file, "\nSimulating statement (from ssa_edges): ");
348 print_generic_stmt (dump_file, use_stmt, dump_flags);
351 if (TREE_CODE (use_stmt) == PHI_NODE)
353 /* PHI nodes are always visited, regardless of whether or not the
354 destination block is executable. */
355 visit_phi_node (use_stmt);
357 else if (TEST_BIT (executable_blocks, use_bb->index))
359 /* Otherwise, visit the statement containing the use reached by
360 DEF, only if the destination block is marked executable. */
361 visit_stmt (use_stmt);
366 /* Perform final substitution and folding. After this pass the program
367 should still be in SSA form. */
370 substitute_and_fold (void)
374 if (dump_file && (dump_flags & TDF_DETAILS))
376 "\nSubstituing constants and folding statements\n\n");
378 /* Substitute constants in every statement of every basic block. */
381 block_stmt_iterator i;
384 /* Propagate our known constants into PHI nodes. */
385 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
389 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
392 tree *orig_p = &PHI_ARG_DEF (phi, i);
394 if (! SSA_VAR_P (*orig_p))
397 new_val = get_value (*orig_p);
398 if (new_val->lattice_val == CONSTANT
399 && may_propagate_copy (*orig_p, new_val->const_val))
400 *orig_p = new_val->const_val;
404 for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
406 bool replaced_address;
407 tree stmt = bsi_stmt (i);
409 /* Skip statements that have been folded already. */
410 if (stmt_modified_p (stmt) || !is_exec_stmt (stmt))
413 /* Replace the statement with its folded version and mark it
415 if (dump_file && (dump_flags & TDF_DETAILS))
417 fprintf (dump_file, "Line %d: replaced ", get_lineno (stmt));
418 print_generic_stmt (dump_file, stmt, TDF_SLIM);
421 if (replace_uses_in (stmt, &replaced_address))
423 bool changed = fold_stmt (bsi_stmt_ptr (i));
426 /* If we folded a builtin function, we'll likely
427 need to rename VDEFs. */
428 if (replaced_address || changed)
429 mark_new_vars_to_rename (stmt, vars_to_rename);
432 if (dump_file && (dump_flags & TDF_DETAILS))
434 fprintf (dump_file, " with ");
435 print_generic_stmt (dump_file, stmt, TDF_SLIM);
436 fprintf (dump_file, "\n");
443 /* Loop through the PHI_NODE's parameters for BLOCK and compare their
444 lattice values to determine PHI_NODE's lattice value. The value of a
445 PHI node is determined calling cp_lattice_meet() with all the arguments
446 of the PHI node that are incoming via executable edges. */
449 visit_phi_node (tree phi)
451 bool short_circuit = 0;
452 value phi_val, *curr_val;
455 /* If the PHI node has already been deemed to be VARYING, don't simulate
457 if (DONT_SIMULATE_AGAIN (phi))
460 if (dump_file && (dump_flags & TDF_DETAILS))
462 fprintf (dump_file, "\nVisiting PHI node: ");
463 print_generic_expr (dump_file, phi, dump_flags);
466 curr_val = get_value (PHI_RESULT (phi));
467 switch (curr_val->lattice_val)
470 if (dump_file && (dump_flags & TDF_DETAILS))
471 fprintf (dump_file, "\n Shortcircuit. Default of VARYING.");
481 phi_val.lattice_val = UNDEFINED;
482 phi_val.const_val = NULL_TREE;
489 /* If the variable is volatile or the variable is never referenced in a
490 real operand, then consider the PHI node VARYING. */
491 if (short_circuit || TREE_THIS_VOLATILE (SSA_NAME_VAR (PHI_RESULT (phi))))
493 phi_val.lattice_val = VARYING;
494 phi_val.const_val = NULL;
497 for (i = 0; i < PHI_NUM_ARGS (phi); i++)
499 /* Compute the meet operator over all the PHI arguments. */
500 edge e = PHI_ARG_EDGE (phi, i);
502 if (dump_file && (dump_flags & TDF_DETAILS))
505 "\n Argument #%d (%d -> %d %sexecutable)\n",
506 i, e->src->index, e->dest->index,
507 (e->flags & EDGE_EXECUTABLE) ? "" : "not ");
510 /* If the incoming edge is executable, Compute the meet operator for
511 the existing value of the PHI node and the current PHI argument. */
512 if (e->flags & EDGE_EXECUTABLE)
514 tree rdef = PHI_ARG_DEF (phi, i);
515 value *rdef_val, val;
517 if (is_gimple_min_invariant (rdef))
519 val.lattice_val = CONSTANT;
520 val.const_val = rdef;
524 rdef_val = get_value (rdef);
526 phi_val = cp_lattice_meet (phi_val, *rdef_val);
528 if (dump_file && (dump_flags & TDF_DETAILS))
530 fprintf (dump_file, "\t");
531 print_generic_expr (dump_file, rdef, dump_flags);
532 dump_lattice_value (dump_file, "\tValue: ", *rdef_val);
533 fprintf (dump_file, "\n");
536 if (phi_val.lattice_val == VARYING)
541 if (dump_file && (dump_flags & TDF_DETAILS))
543 dump_lattice_value (dump_file, "\n PHI node value: ", phi_val);
544 fprintf (dump_file, "\n\n");
547 set_lattice_value (PHI_RESULT (phi), phi_val);
548 if (phi_val.lattice_val == VARYING)
549 DONT_SIMULATE_AGAIN (phi) = 1;
553 /* Compute the meet operator between VAL1 and VAL2:
555 any M UNDEFINED = any
556 any M VARYING = VARYING
557 Ci M Cj = Ci if (i == j)
558 Ci M Cj = VARYING if (i != j) */
560 cp_lattice_meet (value val1, value val2)
564 /* any M UNDEFINED = any. */
565 if (val1.lattice_val == UNDEFINED)
567 else if (val2.lattice_val == UNDEFINED)
570 /* any M VARYING = VARYING. */
571 if (val1.lattice_val == VARYING || val2.lattice_val == VARYING)
573 result.lattice_val = VARYING;
574 result.const_val = NULL_TREE;
578 /* Ci M Cj = Ci if (i == j)
579 Ci M Cj = VARYING if (i != j) */
580 if (simple_cst_equal (val1.const_val, val2.const_val) == 1)
582 result.lattice_val = CONSTANT;
583 result.const_val = val1.const_val;
587 result.lattice_val = VARYING;
588 result.const_val = NULL_TREE;
595 /* Evaluate statement STMT. If the statement produces an output value and
596 its evaluation changes the lattice value of its output, do the following:
598 - If the statement is an assignment, add all the SSA edges starting at
601 - If the statement is a conditional branch:
602 . If the statement evaluates to non-constant, add all edges to
604 . If the statement is constant, add the edge executed as the
605 result of the branch. */
608 visit_stmt (tree stmt)
613 v_may_def_optype v_may_defs;
614 v_must_def_optype v_must_defs;
616 /* If the statement has already been deemed to be VARYING, don't simulate
618 if (DONT_SIMULATE_AGAIN (stmt))
621 if (dump_file && (dump_flags & TDF_DETAILS))
623 fprintf (dump_file, "\nVisiting statement: ");
624 print_generic_stmt (dump_file, stmt, TDF_SLIM);
625 fprintf (dump_file, "\n");
628 ann = stmt_ann (stmt);
630 /* If this statement is already in the worklist then "cancel" it. The
631 reevaluation implied by the worklist entry will produce the same
632 value we generate here and thus reevaluating it again from the
633 worklist is pointless. */
634 if (ann->in_ccp_worklist)
635 ann->in_ccp_worklist = 0;
637 /* Now examine the statement. If the statement is an assignment that
638 produces a single output value, evaluate its RHS to see if the lattice
639 value of its output has changed. */
640 if (TREE_CODE (stmt) == MODIFY_EXPR
641 && TREE_CODE (TREE_OPERAND (stmt, 0)) == SSA_NAME)
642 visit_assignment (stmt);
644 /* Definitions made by statements other than assignments to SSA_NAMEs
645 represent unknown modifications to their outputs. Mark them VARYING. */
646 else if (NUM_DEFS (defs = DEF_OPS (ann)) != 0)
648 DONT_SIMULATE_AGAIN (stmt) = 1;
649 for (i = 0; i < NUM_DEFS (defs); i++)
651 tree def = DEF_OP (defs, i);
652 def_to_varying (def);
656 /* If STMT is a conditional branch, see if we can determine which branch
658 else if (TREE_CODE (stmt) == COND_EXPR || TREE_CODE (stmt) == SWITCH_EXPR)
659 visit_cond_stmt (stmt);
661 /* Any other kind of statement is not interesting for constant
662 propagation and, therefore, not worth simulating. */
665 DONT_SIMULATE_AGAIN (stmt) = 1;
667 /* If STMT is a computed goto, then mark all the output edges
669 if (computed_goto_p (stmt))
670 add_outgoing_control_edges (bb_for_stmt (stmt));
673 /* Mark all V_MAY_DEF operands VARYING. */
674 v_may_defs = V_MAY_DEF_OPS (ann);
675 for (i = 0; i < NUM_V_MAY_DEFS (v_may_defs); i++)
676 def_to_varying (V_MAY_DEF_RESULT (v_may_defs, i));
678 /* Mark all V_MUST_DEF operands VARYING. */
679 v_must_defs = V_MUST_DEF_OPS (ann);
680 for (i = 0; i < NUM_V_MUST_DEFS (v_must_defs); i++)
681 def_to_varying (V_MUST_DEF_OP (v_must_defs, i));
685 /* Visit the assignment statement STMT. Set the value of its LHS to the
686 value computed by the RHS. */
689 visit_assignment (tree stmt)
694 lhs = TREE_OPERAND (stmt, 0);
695 rhs = TREE_OPERAND (stmt, 1);
697 if (TREE_THIS_VOLATILE (SSA_NAME_VAR (lhs)))
699 /* Volatile variables are always VARYING. */
700 val.lattice_val = VARYING;
701 val.const_val = NULL_TREE;
703 else if (TREE_CODE (rhs) == SSA_NAME)
705 /* For a simple copy operation, we copy the lattice values. */
706 value *nval = get_value (rhs);
711 /* Evaluate the statement. */
712 val = evaluate_stmt (stmt);
715 /* FIXME: Hack. If this was a definition of a bitfield, we need to widen
716 the constant value into the type of the destination variable. This
717 should not be necessary if GCC represented bitfields properly. */
719 tree lhs = TREE_OPERAND (stmt, 0);
720 if (val.lattice_val == CONSTANT
721 && TREE_CODE (lhs) == COMPONENT_REF
722 && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))
724 tree w = widen_bitfield (val.const_val, TREE_OPERAND (lhs, 1), lhs);
726 if (w && is_gimple_min_invariant (w))
730 val.lattice_val = VARYING;
731 val.const_val = NULL;
736 /* Set the lattice value of the statement's output. */
737 set_lattice_value (lhs, val);
738 if (val.lattice_val == VARYING)
739 DONT_SIMULATE_AGAIN (stmt) = 1;
743 /* Visit the conditional statement STMT. If it evaluates to a constant value,
744 mark outgoing edges appropriately. */
747 visit_cond_stmt (tree stmt)
753 block = bb_for_stmt (stmt);
754 val = evaluate_stmt (stmt);
756 /* Find which edge out of the conditional block will be taken and add it
757 to the worklist. If no single edge can be determined statically, add
758 all outgoing edges from BLOCK. */
759 e = find_taken_edge (block, val.const_val);
761 add_control_edge (e);
764 DONT_SIMULATE_AGAIN (stmt) = 1;
765 add_outgoing_control_edges (block);
770 /* Add all the edges coming out of BB to the control flow worklist. */
773 add_outgoing_control_edges (basic_block bb)
777 for (e = bb->succ; e; e = e->succ_next)
778 add_control_edge (e);
782 /* Add edge E to the control flow worklist. */
785 add_control_edge (edge e)
787 basic_block bb = e->dest;
788 if (bb == EXIT_BLOCK_PTR)
791 /* If the edge had already been executed, skip it. */
792 if (e->flags & EDGE_EXECUTABLE)
795 e->flags |= EDGE_EXECUTABLE;
797 /* If the block is already in the list, we're done. */
798 if (TEST_BIT (bb_in_list, bb->index))
803 if (dump_file && (dump_flags & TDF_DETAILS))
804 fprintf (dump_file, "Adding Destination of edge (%d -> %d) to worklist\n\n",
805 e->src->index, e->dest->index);
809 /* CCP specific front-end to the non-destructive constant folding routines.
811 Attempt to simplify the RHS of STMT knowing that one or more
812 operands are constants.
814 If simplification is possible, return the simplified RHS,
815 otherwise return the original RHS. */
820 tree rhs = get_rhs (stmt);
821 enum tree_code code = TREE_CODE (rhs);
822 int kind = TREE_CODE_CLASS (code);
823 tree retval = NULL_TREE;
825 /* If the RHS is just a variable, then that variable must now have
826 a constant value that we can return directly. */
827 if (TREE_CODE (rhs) == SSA_NAME)
828 return get_value (rhs)->const_val;
830 /* Unary operators. Note that we know the single operand must
831 be a constant. So this should almost always return a
835 /* Handle unary operators which can appear in GIMPLE form. */
836 tree op0 = TREE_OPERAND (rhs, 0);
838 /* Simplify the operand down to a constant. */
839 if (TREE_CODE (op0) == SSA_NAME)
841 value *val = get_value (op0);
842 if (val->lattice_val == CONSTANT)
843 op0 = get_value (op0)->const_val;
846 retval = nondestructive_fold_unary_to_constant (code,
850 /* If we folded, but did not create an invariant, then we can not
851 use this expression. */
852 if (retval && ! is_gimple_min_invariant (retval))
855 /* If we could not fold the expression, but the arguments are all
856 constants and gimple values, then build and return the new
859 In some cases the new expression is still something we can
860 use as a replacement for an argument. This happens with
861 NOP conversions of types for example.
863 In other cases the new expression can not be used as a
864 replacement for an argument (as it would create non-gimple
865 code). But the new expression can still be used to derive
867 if (! retval && is_gimple_min_invariant (op0))
868 return build1 (code, TREE_TYPE (rhs), op0);
871 /* Binary and comparison operators. We know one or both of the
872 operands are constants. */
875 || code == TRUTH_AND_EXPR
876 || code == TRUTH_OR_EXPR
877 || code == TRUTH_XOR_EXPR)
879 /* Handle binary and comparison operators that can appear in
881 tree op0 = TREE_OPERAND (rhs, 0);
882 tree op1 = TREE_OPERAND (rhs, 1);
884 /* Simplify the operands down to constants when appropriate. */
885 if (TREE_CODE (op0) == SSA_NAME)
887 value *val = get_value (op0);
888 if (val->lattice_val == CONSTANT)
889 op0 = val->const_val;
892 if (TREE_CODE (op1) == SSA_NAME)
894 value *val = get_value (op1);
895 if (val->lattice_val == CONSTANT)
896 op1 = val->const_val;
899 retval = nondestructive_fold_binary_to_constant (code,
903 /* If we folded, but did not create an invariant, then we can not
904 use this expression. */
905 if (retval && ! is_gimple_min_invariant (retval))
908 /* If we could not fold the expression, but the arguments are all
909 constants and gimple values, then build and return the new
912 In some cases the new expression is still something we can
913 use as a replacement for an argument. This happens with
914 NOP conversions of types for example.
916 In other cases the new expression can not be used as a
917 replacement for an argument (as it would create non-gimple
918 code). But the new expression can still be used to derive
921 && is_gimple_min_invariant (op0)
922 && is_gimple_min_invariant (op1))
923 return build (code, TREE_TYPE (rhs), op0, op1);
926 /* We may be able to fold away calls to builtin functions if their
927 arguments are constants. */
928 else if (code == CALL_EXPR
929 && TREE_CODE (TREE_OPERAND (rhs, 0)) == ADDR_EXPR
930 && (TREE_CODE (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0))
932 && DECL_BUILT_IN (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0)))
934 use_optype uses = STMT_USE_OPS (stmt);
935 if (NUM_USES (uses) != 0)
940 /* Preserve the original values of every operand. */
941 orig = xmalloc (sizeof (tree) * NUM_USES (uses));
942 for (i = 0; i < NUM_USES (uses); i++)
943 orig[i] = USE_OP (uses, i);
945 /* Substitute operands with their values and try to fold. */
946 replace_uses_in (stmt, NULL);
947 retval = fold_builtin (rhs);
949 /* Restore operands to their original form. */
950 for (i = 0; i < NUM_USES (uses); i++)
951 *(USE_OP_PTR (uses, i)) = orig[i];
958 /* If we got a simplified form, see if we need to convert its type. */
961 if (TREE_TYPE (retval) != TREE_TYPE (rhs))
962 retval = fold_convert (TREE_TYPE (rhs), retval);
964 if (TREE_TYPE (retval) == TREE_TYPE (rhs))
968 /* No simplification was possible. */
973 /* Evaluate statement STMT. */
976 evaluate_stmt (tree stmt)
980 latticevalue likelyvalue = likely_value (stmt);
982 /* If the statement is likely to have a CONSTANT result, then try
983 to fold the statement to determine the constant value. */
984 if (likelyvalue == CONSTANT)
985 simplified = ccp_fold (stmt);
986 /* If the statement is likely to have a VARYING result, then do not
987 bother folding the statement. */
988 else if (likelyvalue == VARYING)
989 simplified = get_rhs (stmt);
990 /* Otherwise the statement is likely to have an UNDEFINED value and
991 there will be nothing to do. */
993 simplified = NULL_TREE;
995 if (simplified && is_gimple_min_invariant (simplified))
997 /* The statement produced a constant value. */
998 val.lattice_val = CONSTANT;
999 val.const_val = simplified;
1003 /* The statement produced a nonconstant value. If the statement
1004 had undefined operands, then the result of the statement should
1005 be undefined. Else the result of the statement is VARYING. */
1006 val.lattice_val = (likelyvalue == UNDEFINED ? UNDEFINED : VARYING);
1007 val.const_val = NULL_TREE;
1014 /* Debugging dumps. */
1017 dump_lattice_value (FILE *outf, const char *prefix, value val)
1019 switch (val.lattice_val)
1022 fprintf (outf, "%sUNDEFINED", prefix);
1025 fprintf (outf, "%sVARYING", prefix);
1028 fprintf (outf, "%sCONSTANT ", prefix);
1029 print_generic_expr (outf, val.const_val, dump_flags);
1036 /* Given a constant value VAL for bitfield FIELD, and a destination
1037 variable VAR, return VAL appropriately widened to fit into VAR. If
1038 FIELD is wider than HOST_WIDE_INT, NULL is returned. */
1041 widen_bitfield (tree val, tree field, tree var)
1043 unsigned var_size, field_size;
1045 unsigned HOST_WIDE_INT mask;
1048 var_size = TREE_INT_CST_LOW (TYPE_SIZE (TREE_TYPE ((var))));
1049 field_size = TREE_INT_CST_LOW (DECL_SIZE (field));
1051 /* Give up if either the bitfield or the variable are too wide. */
1052 if (field_size > HOST_BITS_PER_WIDE_INT || var_size > HOST_BITS_PER_WIDE_INT)
1055 #if defined ENABLE_CHECKING
1056 if (var_size < field_size)
1060 /* If VAL is not an integer constant, then give up. */
1061 if (TREE_CODE (val) != INTEGER_CST)
1064 /* If the sign bit of the value is not set, or the field's type is
1065 unsigned, then just mask off the high order bits of the value. */
1066 if ((TREE_INT_CST_LOW (val) & (1 << (field_size - 1))) == 0
1067 || DECL_UNSIGNED (field))
1069 /* Zero extension. Build a mask with the lower 'field_size' bits
1070 set and a BIT_AND_EXPR node to clear the high order bits of
1072 for (i = 0, mask = 0; i < field_size; i++)
1075 wide_val = build (BIT_AND_EXPR, TREE_TYPE (var), val,
1076 build_int_2 (mask, 0));
1080 /* Sign extension. Create a mask with the upper 'field_size'
1081 bits set and a BIT_IOR_EXPR to set the high order bits of the
1083 for (i = 0, mask = 0; i < (var_size - field_size); i++)
1084 mask |= 1 << (var_size - i - 1);
1086 wide_val = build (BIT_IOR_EXPR, TREE_TYPE (var), val,
1087 build_int_2 (mask, 0));
1090 return fold (wide_val);
1094 /* Function indicating whether we ought to include information for 'var'
1095 when calculating immediate uses. */
1098 need_imm_uses_for (tree var)
1100 return get_value (var)->lattice_val != VARYING;
1104 /* Initialize local data structures and worklists for CCP. */
1111 sbitmap virtual_var;
1113 /* Worklists of SSA edges. */
1114 VARRAY_TREE_INIT (ssa_edges, 20, "ssa_edges");
1115 VARRAY_TREE_INIT (varying_ssa_edges, 20, "varying_ssa_edges");
1117 executable_blocks = sbitmap_alloc (last_basic_block);
1118 sbitmap_zero (executable_blocks);
1120 bb_in_list = sbitmap_alloc (last_basic_block);
1121 sbitmap_zero (bb_in_list);
1123 value_vector = (value *) xmalloc (num_ssa_names * sizeof (value));
1124 memset (value_vector, 0, num_ssa_names * sizeof (value));
1126 /* 1 if ssa variable is used in a virtual variable context. */
1127 virtual_var = sbitmap_alloc (num_ssa_names);
1128 sbitmap_zero (virtual_var);
1130 /* Initialize default values and simulation flags for PHI nodes, statements
1134 block_stmt_iterator i;
1138 v_may_def_optype v_may_defs;
1139 v_must_def_optype v_must_defs;
1143 /* Get the default value for each definition. */
1144 for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
1147 stmt = bsi_stmt (i);
1148 get_stmt_operands (stmt);
1149 ann = stmt_ann (stmt);
1150 defs = DEF_OPS (ann);
1151 for (x = 0; x < NUM_DEFS (defs); x++)
1153 tree def = DEF_OP (defs, x);
1154 if (get_value (def)->lattice_val == VARYING)
1157 DONT_SIMULATE_AGAIN (stmt) = vary;
1159 /* Mark all V_MAY_DEF operands VARYING. */
1160 v_may_defs = V_MAY_DEF_OPS (ann);
1161 for (x = 0; x < NUM_V_MAY_DEFS (v_may_defs); x++)
1163 tree res = V_MAY_DEF_RESULT (v_may_defs, x);
1164 get_value (res)->lattice_val = VARYING;
1165 SET_BIT (virtual_var, SSA_NAME_VERSION (res));
1168 /* Mark all V_MUST_DEF operands VARYING. */
1169 v_must_defs = V_MUST_DEF_OPS (ann);
1170 for (x = 0; x < NUM_V_MUST_DEFS (v_must_defs); x++)
1172 tree v_must_def = V_MUST_DEF_OP (v_must_defs, x);
1173 get_value (v_must_def)->lattice_val = VARYING;
1174 SET_BIT (virtual_var, SSA_NAME_VERSION (v_must_def));
1178 for (e = bb->succ; e; e = e->succ_next)
1179 e->flags &= ~EDGE_EXECUTABLE;
1182 /* Now process PHI nodes. */
1187 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
1190 val = get_value (PHI_RESULT (phi));
1191 if (val->lattice_val != VARYING)
1193 for (x = 0; x < PHI_NUM_ARGS (phi); x++)
1195 var = PHI_ARG_DEF (phi, x);
1196 /* If one argument is virtual, the result is virtual, and
1197 therefore varying. */
1198 if (TREE_CODE (var) == SSA_NAME)
1200 if (TEST_BIT (virtual_var, SSA_NAME_VERSION (var)))
1202 val->lattice_val = VARYING;
1203 SET_BIT (virtual_var,
1204 SSA_NAME_VERSION (PHI_RESULT (phi)));
1210 DONT_SIMULATE_AGAIN (phi) = ((val->lattice_val == VARYING) ? 1 : 0);
1214 sbitmap_free (virtual_var);
1215 /* Compute immediate uses for variables we care about. */
1216 compute_immediate_uses (TDFA_USE_OPS, need_imm_uses_for);
1218 if (dump_file && (dump_flags & TDF_DETAILS))
1219 dump_immediate_uses (dump_file);
1221 VARRAY_BB_INIT (cfg_blocks, 20, "cfg_blocks");
1223 /* Seed the algorithm by adding the successors of the entry block to the
1225 for (e = ENTRY_BLOCK_PTR->succ; e; e = e->succ_next)
1227 if (e->dest != EXIT_BLOCK_PTR)
1229 e->flags |= EDGE_EXECUTABLE;
1230 cfg_blocks_add (e->dest);
1236 /* Free allocated storage. */
1242 varying_ssa_edges = NULL;
1244 free (value_vector);
1245 sbitmap_free (bb_in_list);
1246 sbitmap_free (executable_blocks);
1250 /* Is the block worklist empty. */
1253 cfg_blocks_empty_p (void)
1255 return (cfg_blocks_num == 0);
1258 /* Add a basic block to the worklist. */
1261 cfg_blocks_add (basic_block bb)
1263 if (bb == ENTRY_BLOCK_PTR || bb == EXIT_BLOCK_PTR)
1266 if (TEST_BIT (bb_in_list, bb->index))
1269 if (cfg_blocks_empty_p ())
1271 cfg_blocks_tail = cfg_blocks_head = 0;
1277 if (cfg_blocks_num > VARRAY_SIZE (cfg_blocks))
1279 /* We have to grow the array now. Adjust to queue to occupy the
1280 full space of the original array. */
1281 cfg_blocks_tail = VARRAY_SIZE (cfg_blocks);
1282 cfg_blocks_head = 0;
1283 VARRAY_GROW (cfg_blocks, 2 * VARRAY_SIZE (cfg_blocks));
1286 cfg_blocks_tail = (cfg_blocks_tail + 1) % VARRAY_SIZE (cfg_blocks);
1288 VARRAY_BB (cfg_blocks, cfg_blocks_tail) = bb;
1289 SET_BIT (bb_in_list, bb->index);
1292 /* Remove a block from the worklist. */
1295 cfg_blocks_get (void)
1299 bb = VARRAY_BB (cfg_blocks, cfg_blocks_head);
1301 #ifdef ENABLE_CHECKING
1302 if (cfg_blocks_empty_p () || !bb)
1306 cfg_blocks_head = (cfg_blocks_head + 1) % VARRAY_SIZE (cfg_blocks);
1308 RESET_BIT (bb_in_list, bb->index);
1313 /* We have just defined a new value for VAR. Add all immediate uses
1314 of VAR to the ssa_edges or varying_ssa_edges worklist. */
1316 add_var_to_ssa_edges_worklist (tree var, value val)
1318 tree stmt = SSA_NAME_DEF_STMT (var);
1319 dataflow_t df = get_immediate_uses (stmt);
1320 int num_uses = num_immediate_uses (df);
1323 for (i = 0; i < num_uses; i++)
1325 tree use = immediate_use (df, i);
1327 if (!DONT_SIMULATE_AGAIN (use))
1329 stmt_ann_t ann = stmt_ann (use);
1330 if (ann->in_ccp_worklist == 0)
1332 ann->in_ccp_worklist = 1;
1333 if (val.lattice_val == VARYING)
1334 VARRAY_PUSH_TREE (varying_ssa_edges, use);
1336 VARRAY_PUSH_TREE (ssa_edges, use);
1342 /* Set the lattice value for the variable VAR to VARYING. */
1345 def_to_varying (tree var)
1348 val.lattice_val = VARYING;
1349 val.const_val = NULL_TREE;
1350 set_lattice_value (var, val);
1353 /* Set the lattice value for variable VAR to VAL. */
1356 set_lattice_value (tree var, value val)
1358 value *old = get_value (var);
1360 #ifdef ENABLE_CHECKING
1361 if (val.lattice_val == UNDEFINED)
1363 /* CONSTANT->UNDEFINED is never a valid state transition. */
1364 if (old->lattice_val == CONSTANT)
1367 /* VARYING->UNDEFINED is generally not a valid state transition,
1368 except for values which are initialized to VARYING. */
1369 if (old->lattice_val == VARYING
1370 && get_default_value (var).lattice_val != VARYING)
1373 else if (val.lattice_val == CONSTANT)
1375 /* VARYING -> CONSTANT is an invalid state transition, except
1376 for objects which start off in a VARYING state. */
1377 if (old->lattice_val == VARYING
1378 && get_default_value (var).lattice_val != VARYING)
1383 /* If the constant for VAR has changed, then this VAR is really varying. */
1384 if (old->lattice_val == CONSTANT && val.lattice_val == CONSTANT
1385 && !simple_cst_equal (old->const_val, val.const_val))
1387 val.lattice_val = VARYING;
1388 val.const_val = NULL_TREE;
1391 if (old->lattice_val != val.lattice_val)
1393 if (dump_file && (dump_flags & TDF_DETAILS))
1395 dump_lattice_value (dump_file,
1396 "Lattice value changed to ", val);
1397 fprintf (dump_file, ". Adding definition to SSA edges.\n");
1400 add_var_to_ssa_edges_worklist (var, val);
1405 /* Replace USE references in statement STMT with their immediate reaching
1406 definition. Return true if at least one reference was replaced. If
1407 REPLACED_ADDRESSES_P is given, it will be set to true if an address
1408 constant was replaced. */
1411 replace_uses_in (tree stmt, bool *replaced_addresses_p)
1413 bool replaced = false;
1417 if (replaced_addresses_p)
1418 *replaced_addresses_p = false;
1420 get_stmt_operands (stmt);
1422 uses = STMT_USE_OPS (stmt);
1423 for (i = 0; i < NUM_USES (uses); i++)
1425 tree *use = USE_OP_PTR (uses, i);
1426 value *val = get_value (*use);
1428 if (val->lattice_val == CONSTANT)
1430 *use = val->const_val;
1432 if (POINTER_TYPE_P (TREE_TYPE (*use)) && replaced_addresses_p)
1433 *replaced_addresses_p = true;
1440 /* Return the likely latticevalue for STMT.
1442 If STMT has no operands, then return CONSTANT.
1444 Else if any operands of STMT are undefined, then return UNDEFINED.
1446 Else if any operands of STMT are constants, then return CONSTANT.
1448 Else return VARYING. */
1451 likely_value (tree stmt)
1455 int found_constant = 0;
1458 /* If the statement makes aliased loads or has volatile operands, it
1459 won't fold to a constant value. */
1460 ann = stmt_ann (stmt);
1461 if (ann->makes_aliased_loads || ann->has_volatile_ops)
1464 /* A CALL_EXPR is assumed to be varying. This may be overly conservative,
1465 in the presence of const and pure calls. */
1466 if (get_call_expr_in (stmt) != NULL_TREE)
1469 get_stmt_operands (stmt);
1471 uses = USE_OPS (ann);
1472 for (i = 0; i < NUM_USES (uses); i++)
1474 tree use = USE_OP (uses, i);
1475 value *val = get_value (use);
1477 if (val->lattice_val == UNDEFINED)
1480 if (val->lattice_val == CONSTANT)
1484 return ((found_constant || !uses) ? CONSTANT : VARYING);
1487 /* A subroutine of fold_stmt_r. Attempts to fold *(A+O) to A[X].
1488 BASE is an array type. OFFSET is a byte displacement. ORIG_TYPE
1489 is the desired result type. */
1492 maybe_fold_offset_to_array_ref (tree base, tree offset, tree orig_type)
1494 unsigned HOST_WIDE_INT lquo, lrem;
1495 HOST_WIDE_INT hquo, hrem;
1496 tree elt_size, min_idx, idx;
1497 tree array_type, elt_type;
1499 /* Ignore stupid user tricks of indexing non-array variables. */
1500 array_type = TREE_TYPE (base);
1501 if (TREE_CODE (array_type) != ARRAY_TYPE)
1503 elt_type = TREE_TYPE (array_type);
1504 if (!lang_hooks.types_compatible_p (orig_type, elt_type))
1507 /* Whee. Ignore indexing of variable sized types. */
1508 elt_size = TYPE_SIZE_UNIT (elt_type);
1509 if (TREE_CODE (elt_size) != INTEGER_CST)
1512 /* If the division isn't exact, then don't do anything. Equally
1513 invalid as the above indexing of non-array variables. */
1514 if (div_and_round_double (TRUNC_DIV_EXPR, 1,
1515 TREE_INT_CST_LOW (offset),
1516 TREE_INT_CST_HIGH (offset),
1517 TREE_INT_CST_LOW (elt_size),
1518 TREE_INT_CST_HIGH (elt_size),
1519 &lquo, &hquo, &lrem, &hrem)
1522 idx = build_int_2_wide (lquo, hquo);
1524 /* Re-bias the index by the min index of the array type. */
1525 min_idx = TYPE_DOMAIN (TREE_TYPE (base));
1528 min_idx = TYPE_MIN_VALUE (min_idx);
1531 idx = convert (TREE_TYPE (min_idx), idx);
1532 if (!integer_zerop (min_idx))
1533 idx = int_const_binop (PLUS_EXPR, idx, min_idx, 1);
1537 return build (ARRAY_REF, orig_type, base, idx);
1540 /* A subroutine of fold_stmt_r. Attempts to fold *(S+O) to S.X.
1541 BASE is a record type. OFFSET is a byte displacement. ORIG_TYPE
1542 is the desired result type. */
1543 /* ??? This doesn't handle class inheritance. */
1546 maybe_fold_offset_to_component_ref (tree record_type, tree base, tree offset,
1547 tree orig_type, bool base_is_ptr)
1549 tree f, t, field_type, tail_array_field;
1551 if (TREE_CODE (record_type) != RECORD_TYPE
1552 && TREE_CODE (record_type) != UNION_TYPE
1553 && TREE_CODE (record_type) != QUAL_UNION_TYPE)
1556 /* Short-circuit silly cases. */
1557 if (lang_hooks.types_compatible_p (record_type, orig_type))
1560 tail_array_field = NULL_TREE;
1561 for (f = TYPE_FIELDS (record_type); f ; f = TREE_CHAIN (f))
1565 if (TREE_CODE (f) != FIELD_DECL)
1567 if (DECL_BIT_FIELD (f))
1569 if (TREE_CODE (DECL_FIELD_OFFSET (f)) != INTEGER_CST)
1572 /* ??? Java creates "interesting" fields for representing base classes.
1573 They have no name, and have no context. With no context, we get into
1574 trouble with nonoverlapping_component_refs_p. Skip them. */
1575 if (!DECL_FIELD_CONTEXT (f))
1578 /* The previous array field isn't at the end. */
1579 tail_array_field = NULL_TREE;
1581 /* Check to see if this offset overlaps with the field. */
1582 cmp = tree_int_cst_compare (DECL_FIELD_OFFSET (f), offset);
1586 field_type = TREE_TYPE (f);
1589 /* Don't care about offsets into the middle of scalars. */
1590 if (!AGGREGATE_TYPE_P (field_type))
1593 /* Check for array at the end of the struct. This is often
1594 used as for flexible array members. We should be able to
1595 turn this into an array access anyway. */
1596 if (TREE_CODE (field_type) == ARRAY_TYPE)
1597 tail_array_field = f;
1599 /* Check the end of the field against the offset. */
1600 if (!DECL_SIZE_UNIT (f)
1601 || TREE_CODE (DECL_SIZE_UNIT (f)) != INTEGER_CST)
1603 t = int_const_binop (MINUS_EXPR, offset, DECL_FIELD_OFFSET (f), 1);
1604 if (!tree_int_cst_lt (t, DECL_SIZE_UNIT (f)))
1607 /* If we matched, then set offset to the displacement into
1612 /* Here we exactly match the offset being checked. If the types match,
1613 then we can return that field. */
1614 else if (lang_hooks.types_compatible_p (orig_type, field_type))
1617 base = build1 (INDIRECT_REF, record_type, base);
1618 t = build (COMPONENT_REF, field_type, base, f);
1622 /* Don't care about type-punning of scalars. */
1623 else if (!AGGREGATE_TYPE_P (field_type))
1629 if (!tail_array_field)
1632 f = tail_array_field;
1633 field_type = TREE_TYPE (f);
1636 /* If we get here, we've got an aggregate field, and a possibly
1637 nonzero offset into them. Recurse and hope for a valid match. */
1639 base = build1 (INDIRECT_REF, record_type, base);
1640 base = build (COMPONENT_REF, field_type, base, f);
1642 t = maybe_fold_offset_to_array_ref (base, offset, orig_type);
1645 return maybe_fold_offset_to_component_ref (field_type, base, offset,
1649 /* A subroutine of fold_stmt_r. Attempt to simplify *(BASE+OFFSET).
1650 Return the simplified expression, or NULL if nothing could be done. */
1653 maybe_fold_stmt_indirect (tree expr, tree base, tree offset)
1657 /* We may well have constructed a double-nested PLUS_EXPR via multiple
1658 substitutions. Fold that down to one. Remove NON_LVALUE_EXPRs that
1659 are sometimes added. */
1662 TREE_OPERAND (expr, 0) = base;
1664 /* One possibility is that the address reduces to a string constant. */
1665 t = fold_read_from_constant_string (expr);
1669 /* Add in any offset from a PLUS_EXPR. */
1670 if (TREE_CODE (base) == PLUS_EXPR)
1674 offset2 = TREE_OPERAND (base, 1);
1675 if (TREE_CODE (offset2) != INTEGER_CST)
1677 base = TREE_OPERAND (base, 0);
1679 offset = int_const_binop (PLUS_EXPR, offset, offset2, 1);
1682 if (TREE_CODE (base) == ADDR_EXPR)
1684 /* Strip the ADDR_EXPR. */
1685 base = TREE_OPERAND (base, 0);
1687 /* Try folding *(&B+O) to B[X]. */
1688 t = maybe_fold_offset_to_array_ref (base, offset, TREE_TYPE (expr));
1692 /* Try folding *(&B+O) to B.X. */
1693 t = maybe_fold_offset_to_component_ref (TREE_TYPE (base), base, offset,
1694 TREE_TYPE (expr), false);
1698 /* Fold *&B to B. */
1699 if (integer_zerop (offset))
1704 /* We can get here for out-of-range string constant accesses,
1705 such as "_"[3]. Bail out of the entire substitution search
1706 and arrange for the entire statement to be replaced by a
1707 call to __builtin_trap. In all likelyhood this will all be
1708 constant-folded away, but in the meantime we can't leave with
1709 something that get_expr_operands can't understand. */
1713 if (TREE_CODE (t) == ADDR_EXPR
1714 && TREE_CODE (TREE_OPERAND (t, 0)) == STRING_CST)
1716 /* FIXME: Except that this causes problems elsewhere with dead
1717 code not being deleted, and we abort in the rtl expanders
1718 because we failed to remove some ssa_name. In the meantime,
1719 just return zero. */
1720 /* FIXME2: This condition should be signaled by
1721 fold_read_from_constant_string directly, rather than
1722 re-checking for it here. */
1723 return integer_zero_node;
1726 /* Try folding *(B+O) to B->X. Still an improvement. */
1727 if (POINTER_TYPE_P (TREE_TYPE (base)))
1729 t = maybe_fold_offset_to_component_ref (TREE_TYPE (TREE_TYPE (base)),
1731 TREE_TYPE (expr), true);
1737 /* Otherwise we had an offset that we could not simplify. */
1741 /* A subroutine of fold_stmt_r. EXPR is a PLUS_EXPR.
1743 A quaint feature extant in our address arithmetic is that there
1744 can be hidden type changes here. The type of the result need
1745 not be the same as the type of the input pointer.
1747 What we're after here is an expression of the form
1748 (T *)(&array + const)
1749 where the cast doesn't actually exist, but is implicit in the
1750 type of the PLUS_EXPR. We'd like to turn this into
1752 which may be able to propagate further. */
1755 maybe_fold_stmt_addition (tree expr)
1757 tree op0 = TREE_OPERAND (expr, 0);
1758 tree op1 = TREE_OPERAND (expr, 1);
1759 tree ptr_type = TREE_TYPE (expr);
1762 bool subtract = (TREE_CODE (expr) == MINUS_EXPR);
1764 /* We're only interested in pointer arithmetic. */
1765 if (!POINTER_TYPE_P (ptr_type))
1767 /* Canonicalize the integral operand to op1. */
1768 if (INTEGRAL_TYPE_P (TREE_TYPE (op0)))
1772 t = op0, op0 = op1, op1 = t;
1774 /* It had better be a constant. */
1775 if (TREE_CODE (op1) != INTEGER_CST)
1777 /* The first operand should be an ADDR_EXPR. */
1778 if (TREE_CODE (op0) != ADDR_EXPR)
1780 op0 = TREE_OPERAND (op0, 0);
1782 /* If the first operand is an ARRAY_REF, expand it so that we can fold
1783 the offset into it. */
1784 while (TREE_CODE (op0) == ARRAY_REF)
1786 tree array_obj = TREE_OPERAND (op0, 0);
1787 tree array_idx = TREE_OPERAND (op0, 1);
1788 tree elt_type = TREE_TYPE (op0);
1789 tree elt_size = TYPE_SIZE_UNIT (elt_type);
1792 if (TREE_CODE (array_idx) != INTEGER_CST)
1794 if (TREE_CODE (elt_size) != INTEGER_CST)
1797 /* Un-bias the index by the min index of the array type. */
1798 min_idx = TYPE_DOMAIN (TREE_TYPE (array_obj));
1801 min_idx = TYPE_MIN_VALUE (min_idx);
1804 array_idx = convert (TREE_TYPE (min_idx), array_idx);
1805 if (!integer_zerop (min_idx))
1806 array_idx = int_const_binop (MINUS_EXPR, array_idx,
1811 /* Convert the index to a byte offset. */
1812 array_idx = convert (sizetype, array_idx);
1813 array_idx = int_const_binop (MULT_EXPR, array_idx, elt_size, 0);
1815 /* Update the operands for the next round, or for folding. */
1816 /* If we're manipulating unsigned types, then folding into negative
1817 values can produce incorrect results. Particularly if the type
1818 is smaller than the width of the pointer. */
1820 && TYPE_UNSIGNED (TREE_TYPE (op1))
1821 && tree_int_cst_lt (array_idx, op1))
1823 op1 = int_const_binop (subtract ? MINUS_EXPR : PLUS_EXPR,
1829 /* If we weren't able to fold the subtraction into another array reference,
1830 canonicalize the integer for passing to the array and component ref
1831 simplification functions. */
1834 if (TYPE_UNSIGNED (TREE_TYPE (op1)))
1836 op1 = fold (build1 (NEGATE_EXPR, TREE_TYPE (op1), op1));
1837 /* ??? In theory fold should always produce another integer. */
1838 if (TREE_CODE (op1) != INTEGER_CST)
1842 ptd_type = TREE_TYPE (ptr_type);
1844 /* At which point we can try some of the same things as for indirects. */
1845 t = maybe_fold_offset_to_array_ref (op0, op1, ptd_type);
1847 t = maybe_fold_offset_to_component_ref (TREE_TYPE (op0), op0, op1,
1850 t = build1 (ADDR_EXPR, ptr_type, t);
1855 /* Subroutine of fold_stmt called via walk_tree. We perform several
1856 simplifications of EXPR_P, mostly having to do with pointer arithmetic. */
1859 fold_stmt_r (tree *expr_p, int *walk_subtrees, void *data)
1861 bool *changed_p = data;
1862 tree expr = *expr_p, t;
1864 /* ??? It'd be nice if walk_tree had a pre-order option. */
1865 switch (TREE_CODE (expr))
1868 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1873 t = maybe_fold_stmt_indirect (expr, TREE_OPERAND (expr, 0),
1877 /* ??? Could handle ARRAY_REF here, as a variant of INDIRECT_REF.
1878 We'd only want to bother decomposing an existing ARRAY_REF if
1879 the base array is found to have another offset contained within.
1880 Otherwise we'd be wasting time. */
1883 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1888 /* Set TREE_INVARIANT properly so that the value is properly
1889 considered constant, and so gets propagated as expected. */
1891 recompute_tree_invarant_for_addr_expr (expr);
1896 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1899 t = walk_tree (&TREE_OPERAND (expr, 1), fold_stmt_r, data, NULL);
1904 t = maybe_fold_stmt_addition (expr);
1908 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL);
1913 /* Make sure the FIELD_DECL is actually a field in the type on
1914 the lhs. In cases with IMA it is possible that it came
1915 from another, equivalent type at this point. We have
1916 already checked the equivalence in this case.
1917 Match on type plus offset, to allow for unnamed fields.
1918 We won't necessarily get the corresponding field for
1919 unions; this is believed to be harmless. */
1921 if ((current_file_decl && TREE_CHAIN (current_file_decl))
1922 && (DECL_FIELD_CONTEXT (TREE_OPERAND (expr, 1)) !=
1923 TREE_TYPE (TREE_OPERAND (expr, 0))))
1926 tree orig_field = TREE_OPERAND (expr, 1);
1927 tree orig_type = TREE_TYPE (orig_field);
1928 for (f = TYPE_FIELDS (TREE_TYPE (TREE_OPERAND (expr, 0)));
1929 f; f = TREE_CHAIN (f))
1931 if (lang_hooks.types_compatible_p (TREE_TYPE (f), orig_type)
1932 && tree_int_cst_compare (DECL_FIELD_BIT_OFFSET (f),
1933 DECL_FIELD_BIT_OFFSET (orig_field))
1935 && tree_int_cst_compare (DECL_FIELD_OFFSET (f),
1936 DECL_FIELD_OFFSET (orig_field))
1939 TREE_OPERAND (expr, 1) = f;
1943 /* Fall through is an error; it will be detected in tree-sra. */
1960 /* Fold the statement pointed by STMT_P. In some cases, this function may
1961 replace the whole statement with a new one. Returns true iff folding
1962 makes any changes. */
1965 fold_stmt (tree *stmt_p)
1967 tree rhs, result, stmt;
1968 bool changed = false;
1972 /* If we replaced constants and the statement makes pointer dereferences,
1973 then we may need to fold instances of *&VAR into VAR, etc. */
1974 if (walk_tree (stmt_p, fold_stmt_r, &changed, NULL))
1977 = build_function_call_expr (implicit_built_in_decls[BUILT_IN_TRAP],
1982 rhs = get_rhs (stmt);
1987 /* Check for builtins that CCP can handle using information not
1988 available in the generic fold routines. */
1989 if (TREE_CODE (rhs) == CALL_EXPR)
1991 tree callee = get_callee_fndecl (rhs);
1992 if (callee && DECL_BUILT_IN (callee))
1993 result = ccp_fold_builtin (stmt, rhs);
1996 /* If we couldn't fold the RHS, hand over to the generic fold routines. */
1997 if (result == NULL_TREE)
1998 result = fold (rhs);
2000 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that
2001 may have been added by fold, and "useless" type conversions that might
2002 now be apparent due to propagation. */
2003 STRIP_MAIN_TYPE_NOPS (result);
2004 STRIP_USELESS_TYPE_CONVERSION (result);
2009 set_rhs (stmt_p, result);
2015 /* Get the main expression from statement STMT. */
2020 enum tree_code code = TREE_CODE (stmt);
2022 if (code == MODIFY_EXPR)
2023 return TREE_OPERAND (stmt, 1);
2024 if (code == COND_EXPR)
2025 return COND_EXPR_COND (stmt);
2026 else if (code == SWITCH_EXPR)
2027 return SWITCH_COND (stmt);
2028 else if (code == RETURN_EXPR)
2030 if (!TREE_OPERAND (stmt, 0))
2032 if (TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR)
2033 return TREE_OPERAND (TREE_OPERAND (stmt, 0), 1);
2035 return TREE_OPERAND (stmt, 0);
2037 else if (code == GOTO_EXPR)
2038 return GOTO_DESTINATION (stmt);
2039 else if (code == LABEL_EXPR)
2040 return LABEL_EXPR_LABEL (stmt);
2046 /* Set the main expression of *STMT_P to EXPR. */
2049 set_rhs (tree *stmt_p, tree expr)
2051 tree stmt = *stmt_p;
2052 enum tree_code code = TREE_CODE (stmt);
2054 if (code == MODIFY_EXPR)
2055 TREE_OPERAND (stmt, 1) = expr;
2056 else if (code == COND_EXPR)
2057 COND_EXPR_COND (stmt) = expr;
2058 else if (code == SWITCH_EXPR)
2059 SWITCH_COND (stmt) = expr;
2060 else if (code == RETURN_EXPR)
2062 if (TREE_OPERAND (stmt, 0)
2063 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR)
2064 TREE_OPERAND (TREE_OPERAND (stmt, 0), 1) = expr;
2066 TREE_OPERAND (stmt, 0) = expr;
2068 else if (code == GOTO_EXPR)
2069 GOTO_DESTINATION (stmt) = expr;
2070 else if (code == LABEL_EXPR)
2071 LABEL_EXPR_LABEL (stmt) = expr;
2074 /* Replace the whole statement with EXPR. If EXPR has no side
2075 effects, then replace *STMT_P with an empty statement. */
2076 stmt_ann_t ann = stmt_ann (stmt);
2077 *stmt_p = TREE_SIDE_EFFECTS (expr) ? expr : build_empty_stmt ();
2078 (*stmt_p)->common.ann = (tree_ann) ann;
2080 if (TREE_SIDE_EFFECTS (expr))
2083 v_may_def_optype v_may_defs;
2084 v_must_def_optype v_must_defs;
2087 /* Fix all the SSA_NAMEs created by *STMT_P to point to its new
2089 defs = DEF_OPS (ann);
2090 for (i = 0; i < NUM_DEFS (defs); i++)
2092 tree var = DEF_OP (defs, i);
2093 if (TREE_CODE (var) == SSA_NAME)
2094 SSA_NAME_DEF_STMT (var) = *stmt_p;
2097 v_may_defs = V_MAY_DEF_OPS (ann);
2098 for (i = 0; i < NUM_V_MAY_DEFS (v_may_defs); i++)
2100 tree var = V_MAY_DEF_RESULT (v_may_defs, i);
2101 if (TREE_CODE (var) == SSA_NAME)
2102 SSA_NAME_DEF_STMT (var) = *stmt_p;
2105 v_must_defs = V_MUST_DEF_OPS (ann);
2106 for (i = 0; i < NUM_V_MUST_DEFS (v_must_defs); i++)
2108 tree var = V_MUST_DEF_OP (v_must_defs, i);
2109 if (TREE_CODE (var) == SSA_NAME)
2110 SSA_NAME_DEF_STMT (var) = *stmt_p;
2117 /* Return a default value for variable VAR using the following rules:
2119 1- Global and static variables are considered VARYING, unless they are
2122 2- Function arguments are considered VARYING.
2124 3- Any other value is considered UNDEFINED. This is useful when
2125 considering PHI nodes. PHI arguments that are undefined do not
2126 change the constant value of the PHI node, which allows for more
2127 constants to be propagated. */
2130 get_default_value (tree var)
2135 if (TREE_CODE (var) == SSA_NAME)
2136 sym = SSA_NAME_VAR (var);
2139 #ifdef ENABLE_CHECKING
2146 val.lattice_val = UNDEFINED;
2147 val.const_val = NULL_TREE;
2149 if (TREE_CODE (sym) == PARM_DECL || TREE_THIS_VOLATILE (sym))
2151 /* Function arguments and volatile variables are considered VARYING. */
2152 val.lattice_val = VARYING;
2154 else if (decl_function_context (sym) != current_function_decl
2155 || TREE_STATIC (sym))
2157 /* Globals and static variables are considered VARYING, unless they
2158 are declared 'const'. */
2159 val.lattice_val = VARYING;
2161 if (TREE_READONLY (sym)
2162 && DECL_INITIAL (sym)
2163 && is_gimple_min_invariant (DECL_INITIAL (sym)))
2165 val.lattice_val = CONSTANT;
2166 val.const_val = DECL_INITIAL (sym);
2171 enum tree_code code;
2172 tree stmt = SSA_NAME_DEF_STMT (var);
2174 if (!IS_EMPTY_STMT (stmt))
2176 code = TREE_CODE (stmt);
2177 if (code != MODIFY_EXPR && code != PHI_NODE)
2178 val.lattice_val = VARYING;
2186 /* Fold builtin call FN in statement STMT. If it cannot be folded into a
2187 constant, return NULL_TREE. Otherwise, return its constant value. */
2190 ccp_fold_builtin (tree stmt, tree fn)
2192 tree result, strlen_val[2];
2193 tree arglist = TREE_OPERAND (fn, 1), a;
2194 tree callee = get_callee_fndecl (fn);
2198 /* Ignore MD builtins. */
2199 if (DECL_BUILT_IN_CLASS (callee) == BUILT_IN_MD)
2202 /* First try the generic builtin folder. If that succeeds, return the
2204 result = fold_builtin (fn);
2208 /* If the builtin could not be folded, and it has no argument list,
2213 /* Limit the work only for builtins we know how to simplify. */
2214 switch (DECL_FUNCTION_CODE (callee))
2216 case BUILT_IN_STRLEN:
2217 case BUILT_IN_FPUTS:
2218 case BUILT_IN_FPUTS_UNLOCKED:
2221 case BUILT_IN_STRCPY:
2222 case BUILT_IN_STRNCPY:
2229 /* Try to use the dataflow information gathered by the CCP process. */
2230 visited = BITMAP_XMALLOC ();
2232 memset (strlen_val, 0, sizeof (strlen_val));
2233 for (i = 0, a = arglist;
2235 i++, strlen_arg >>= 1, a = TREE_CHAIN (a))
2238 bitmap_clear (visited);
2239 if (!get_strlen (TREE_VALUE (a), &strlen_val[i], visited))
2240 strlen_val[i] = NULL_TREE;
2243 BITMAP_XFREE (visited);
2245 /* FIXME. All this code looks dangerous in the sense that it might
2246 create non-gimple expressions. */
2247 switch (DECL_FUNCTION_CODE (callee))
2249 case BUILT_IN_STRLEN:
2250 /* Convert from the internal "sizetype" type to "size_t". */
2254 tree new = convert (size_type_node, strlen_val[0]);
2256 /* If the result is not a valid gimple value, or not a cast
2257 of a valid gimple value, then we can not use the result. */
2258 if (is_gimple_val (new)
2259 || (is_gimple_cast (new)
2260 && is_gimple_val (TREE_OPERAND (new, 0))))
2265 return strlen_val[0];
2266 case BUILT_IN_STRCPY:
2268 && is_gimple_val (strlen_val[1]))
2269 return simplify_builtin_strcpy (arglist, strlen_val[1]);
2270 case BUILT_IN_STRNCPY:
2272 && is_gimple_val (strlen_val[1]))
2273 return simplify_builtin_strncpy (arglist, strlen_val[1]);
2274 case BUILT_IN_FPUTS:
2275 return simplify_builtin_fputs (arglist,
2276 TREE_CODE (stmt) != MODIFY_EXPR, 0,
2278 case BUILT_IN_FPUTS_UNLOCKED:
2279 return simplify_builtin_fputs (arglist,
2280 TREE_CODE (stmt) != MODIFY_EXPR, 1,
2291 /* Return the string length of ARG in LENGTH. If ARG is an SSA name variable,
2292 follow its use-def chains. If LENGTH is not NULL and its value is not
2293 equal to the length we determine, or if we are unable to determine the
2294 length, return false. VISITED is a bitmap of visited variables. */
2297 get_strlen (tree arg, tree *length, bitmap visited)
2299 tree var, def_stmt, val;
2301 if (TREE_CODE (arg) != SSA_NAME)
2303 val = c_strlen (arg, 1);
2307 if (*length && simple_cst_equal (val, *length) != 1)
2314 /* If we were already here, break the infinite cycle. */
2315 if (bitmap_bit_p (visited, SSA_NAME_VERSION (arg)))
2317 bitmap_set_bit (visited, SSA_NAME_VERSION (arg));
2320 def_stmt = SSA_NAME_DEF_STMT (var);
2322 switch (TREE_CODE (def_stmt))
2328 /* The RHS of the statement defining VAR must either have a
2329 constant length or come from another SSA_NAME with a constant
2331 rhs = TREE_OPERAND (def_stmt, 1);
2333 if (TREE_CODE (rhs) == SSA_NAME)
2334 return get_strlen (rhs, length, visited);
2336 /* See if the RHS is a constant length. */
2337 len = c_strlen (rhs, 1);
2340 if (*length && simple_cst_equal (len, *length) != 1)
2352 /* All the arguments of the PHI node must have the same constant
2356 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++)
2358 tree arg = PHI_ARG_DEF (def_stmt, i);
2360 /* If this PHI has itself as an argument, we cannot
2361 determine the string length of this argument. However,
2362 if we can find a constant string length for the other
2363 PHI args then we can still be sure that this is a
2364 constant string length. So be optimistic and just
2365 continue with the next argument. */
2366 if (arg == PHI_RESULT (def_stmt))
2369 if (!get_strlen (arg, length, visited))
2385 /* A simple pass that attempts to fold all builtin functions. This pass
2386 is run after we've propagated as many constants as we can. */
2389 execute_fold_all_builtins (void)
2394 block_stmt_iterator i;
2395 for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i))
2397 tree *stmtp = bsi_stmt_ptr (i);
2398 tree call = get_rhs (*stmtp);
2399 tree callee, result;
2401 if (!call || TREE_CODE (call) != CALL_EXPR)
2403 callee = get_callee_fndecl (call);
2404 if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)
2407 result = ccp_fold_builtin (*stmtp, call);
2409 switch (DECL_FUNCTION_CODE (callee))
2411 case BUILT_IN_CONSTANT_P:
2412 /* Resolve __builtin_constant_p. If it hasn't been
2413 folded to integer_one_node by now, it's fairly
2414 certain that the value simply isn't constant. */
2415 result = integer_zero_node;
2422 if (dump_file && (dump_flags & TDF_DETAILS))
2424 fprintf (dump_file, "Simplified\n ");
2425 print_generic_stmt (dump_file, *stmtp, dump_flags);
2428 set_rhs (stmtp, result);
2429 modify_stmt (*stmtp);
2431 if (dump_file && (dump_flags & TDF_DETAILS))
2433 fprintf (dump_file, "to\n ");
2434 print_generic_stmt (dump_file, *stmtp, dump_flags);
2435 fprintf (dump_file, "\n");
2441 struct tree_opt_pass pass_fold_builtins =
2445 execute_fold_all_builtins, /* execute */
2448 0, /* static_pass_number */
2450 PROP_cfg | PROP_ssa, /* properties_required */
2451 0, /* properties_provided */
2452 0, /* properties_destroyed */
2453 0, /* todo_flags_start */
2454 TODO_dump_func | TODO_verify_ssa /* todo_flags_finish */
2458 #include "gt-tree-ssa-ccp.h"