1 /* Data flow functions for trees.
2 Copyright (C) 2001, 2002, 2003, 2004, 2005, 2007 Free Software Foundation, Inc.
3 Contributed by Diego Novillo <dnovillo@redhat.com>
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3, or (at your option)
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
23 #include "coretypes.h"
26 #include "pointer-set.h"
30 #include "hard-reg-set.h"
31 #include "basic-block.h"
36 #include "langhooks.h"
39 #include "diagnostic.h"
40 #include "tree-dump.h"
41 #include "tree-gimple.h"
42 #include "tree-flow.h"
43 #include "tree-inline.h"
44 #include "tree-pass.h"
49 /* Build and maintain data flow information for trees. */
51 /* Counters used to display DFA and SSA statistics. */
66 /* Local functions. */
67 static void collect_dfa_stats (struct dfa_stats_d *);
68 static tree collect_dfa_stats_r (tree *, int *, void *);
69 static tree find_vars_r (tree *, int *, void *);
72 /*---------------------------------------------------------------------------
73 Dataflow analysis (DFA) routines
74 ---------------------------------------------------------------------------*/
75 /* Find all the variables referenced in the function. This function
76 builds the global arrays REFERENCED_VARS and CALL_CLOBBERED_VARS.
78 Note that this function does not look for statement operands, it simply
79 determines what variables are referenced in the program and detects
80 various attributes for each variable used by alias analysis and the
84 find_referenced_vars (void)
87 block_stmt_iterator si;
90 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
92 tree *stmt_p = bsi_stmt_ptr (si);
93 walk_tree (stmt_p, find_vars_r, NULL, NULL);
99 struct tree_opt_pass pass_referenced_vars =
103 find_referenced_vars, /* execute */
106 0, /* static_pass_number */
107 TV_FIND_REFERENCED_VARS, /* tv_id */
108 PROP_gimple_leh | PROP_cfg, /* properties_required */
109 PROP_referenced_vars, /* properties_provided */
110 0, /* properties_destroyed */
111 0, /* todo_flags_start */
112 0, /* todo_flags_finish */
117 /*---------------------------------------------------------------------------
119 ---------------------------------------------------------------------------*/
120 /* Create a new annotation for a _DECL node T. */
123 create_var_ann (tree t)
126 struct static_var_ann_d *sann = NULL;
129 gcc_assert (DECL_P (t));
130 gcc_assert (!t->base.ann || t->base.ann->common.type == VAR_ANN);
132 if (!MTAG_P (t) && (TREE_STATIC (t) || DECL_EXTERNAL (t)))
134 sann = GGC_CNEW (struct static_var_ann_d);
138 ann = GGC_CNEW (struct var_ann_d);
140 ann->common.type = VAR_ANN;
142 if (!MTAG_P (t) && (TREE_STATIC (t) || DECL_EXTERNAL (t)))
145 sann->uid = DECL_UID (t);
146 slot = htab_find_slot_with_hash (gimple_var_anns (cfun),
147 t, DECL_UID (t), INSERT);
152 t->base.ann = (tree_ann_t) ann;
157 /* Create a new annotation for a FUNCTION_DECL node T. */
160 create_function_ann (tree t)
165 gcc_assert (TREE_CODE (t) == FUNCTION_DECL);
166 gcc_assert (!t->base.ann || t->base.ann->common.type == FUNCTION_ANN);
168 ann = ggc_alloc (sizeof (*ann));
169 memset ((void *) ann, 0, sizeof (*ann));
171 ann->common.type = FUNCTION_ANN;
173 t->base.ann = (tree_ann_t) ann;
178 /* Create a new annotation for a statement node T. */
181 create_stmt_ann (tree t)
185 gcc_assert (is_gimple_stmt (t));
186 gcc_assert (!t->base.ann || t->base.ann->common.type == STMT_ANN);
188 ann = GGC_CNEW (struct stmt_ann_d);
190 ann->common.type = STMT_ANN;
192 /* Since we just created the annotation, mark the statement modified. */
193 ann->modified = true;
195 t->base.ann = (tree_ann_t) ann;
200 /* Create a new annotation for a tree T. */
203 create_tree_common_ann (tree t)
205 tree_ann_common_t ann;
208 gcc_assert (!t->base.ann || t->base.ann->common.type == TREE_ANN_COMMON);
210 ann = GGC_CNEW (struct tree_ann_common_d);
212 ann->type = TREE_ANN_COMMON;
213 t->base.ann = (tree_ann_t) ann;
218 /* Build a temporary. Make sure and register it to be renamed. */
221 make_rename_temp (tree type, const char *prefix)
223 tree t = create_tmp_var (type, prefix);
225 if (TREE_CODE (TREE_TYPE (t)) == COMPLEX_TYPE
226 || TREE_CODE (TREE_TYPE (t)) == VECTOR_TYPE)
227 DECL_GIMPLE_REG_P (t) = 1;
229 if (gimple_referenced_vars (cfun))
231 add_referenced_var (t);
232 mark_sym_for_renaming (t);
240 /*---------------------------------------------------------------------------
242 ---------------------------------------------------------------------------*/
243 /* Dump the list of all the referenced variables in the current function to
247 dump_referenced_vars (FILE *file)
250 referenced_var_iterator rvi;
252 fprintf (file, "\nReferenced variables in %s: %u\n\n",
253 get_name (current_function_decl), (unsigned) num_referenced_vars);
255 FOR_EACH_REFERENCED_VAR (var, rvi)
257 fprintf (file, "Variable: ");
258 dump_variable (file, var);
259 fprintf (file, "\n");
264 /* Dump the list of all the referenced variables to stderr. */
267 debug_referenced_vars (void)
269 dump_referenced_vars (stderr);
273 /* Dump sub-variables for VAR to FILE. */
276 dump_subvars_for (FILE *file, tree var)
278 subvar_t sv = get_subvars_for_var (var);
283 fprintf (file, "{ ");
285 for (; sv; sv = sv->next)
287 print_generic_expr (file, sv->var, dump_flags);
295 /* Dumb sub-variables for VAR to stderr. */
298 debug_subvars_for (tree var)
300 dump_subvars_for (stderr, var);
304 /* Dump variable VAR and its may-aliases to FILE. */
307 dump_variable (FILE *file, tree var)
311 if (TREE_CODE (var) == SSA_NAME)
313 if (POINTER_TYPE_P (TREE_TYPE (var)))
314 dump_points_to_info_for (file, var);
315 var = SSA_NAME_VAR (var);
318 if (var == NULL_TREE)
320 fprintf (file, "<nil>");
324 print_generic_expr (file, var, dump_flags);
328 fprintf (file, ", UID D.%u", (unsigned) DECL_UID (var));
330 fprintf (file, ", ");
331 print_generic_expr (file, TREE_TYPE (var), dump_flags);
333 if (ann && ann->symbol_mem_tag)
335 fprintf (file, ", symbol memory tag: ");
336 print_generic_expr (file, ann->symbol_mem_tag, dump_flags);
339 if (TREE_ADDRESSABLE (var))
340 fprintf (file, ", is addressable");
342 if (is_global_var (var))
343 fprintf (file, ", is global");
345 if (TREE_THIS_VOLATILE (var))
346 fprintf (file, ", is volatile");
348 dump_mem_sym_stats_for_var (file, var);
350 if (is_call_clobbered (var))
353 var_ann_t va = var_ann (var);
354 unsigned int escape_mask = va->escape_mask;
356 fprintf (file, ", call clobbered");
357 fprintf (file, " (");
358 if (escape_mask & ESCAPE_STORED_IN_GLOBAL)
359 { fprintf (file, "%sstored in global", s); s = ", "; }
360 if (escape_mask & ESCAPE_TO_ASM)
361 { fprintf (file, "%sgoes through ASM", s); s = ", "; }
362 if (escape_mask & ESCAPE_TO_CALL)
363 { fprintf (file, "%spassed to call", s); s = ", "; }
364 if (escape_mask & ESCAPE_BAD_CAST)
365 { fprintf (file, "%sbad cast", s); s = ", "; }
366 if (escape_mask & ESCAPE_TO_RETURN)
367 { fprintf (file, "%sreturned from func", s); s = ", "; }
368 if (escape_mask & ESCAPE_TO_PURE_CONST)
369 { fprintf (file, "%spassed to pure/const", s); s = ", "; }
370 if (escape_mask & ESCAPE_IS_GLOBAL)
371 { fprintf (file, "%sis global var", s); s = ", "; }
372 if (escape_mask & ESCAPE_IS_PARM)
373 { fprintf (file, "%sis incoming pointer", s); s = ", "; }
374 if (escape_mask & ESCAPE_UNKNOWN)
375 { fprintf (file, "%sunknown escape", s); s = ", "; }
379 if (ann->noalias_state == NO_ALIAS)
380 fprintf (file, ", NO_ALIAS (does not alias other NO_ALIAS symbols)");
381 else if (ann->noalias_state == NO_ALIAS_GLOBAL)
382 fprintf (file, ", NO_ALIAS_GLOBAL (does not alias other NO_ALIAS symbols"
383 " and global vars)");
384 else if (ann->noalias_state == NO_ALIAS_ANYTHING)
385 fprintf (file, ", NO_ALIAS_ANYTHING (does not alias any other symbols)");
387 if (gimple_default_def (cfun, var))
389 fprintf (file, ", default def: ");
390 print_generic_expr (file, gimple_default_def (cfun, var), dump_flags);
393 if (MTAG_P (var) && may_aliases (var))
395 fprintf (file, ", may aliases: ");
396 dump_may_aliases_for (file, var);
399 if (get_subvars_for_var (var))
401 fprintf (file, ", sub-vars: ");
402 dump_subvars_for (file, var);
405 if (!is_gimple_reg (var))
407 if (memory_partition (var))
409 fprintf (file, ", belongs to partition: ");
410 print_generic_expr (file, memory_partition (var), dump_flags);
413 if (TREE_CODE (var) == MEMORY_PARTITION_TAG)
415 fprintf (file, ", partition symbols: ");
416 dump_decl_set (file, MPT_SYMBOLS (var));
420 fprintf (file, "\n");
424 /* Dump variable VAR and its may-aliases to stderr. */
427 debug_variable (tree var)
429 dump_variable (stderr, var);
433 /* Dump various DFA statistics to FILE. */
436 dump_dfa_stats (FILE *file)
438 struct dfa_stats_d dfa_stats;
440 unsigned long size, total = 0;
441 const char * const fmt_str = "%-30s%-13s%12s\n";
442 const char * const fmt_str_1 = "%-30s%13lu%11lu%c\n";
443 const char * const fmt_str_3 = "%-43s%11lu%c\n";
445 = lang_hooks.decl_printable_name (current_function_decl, 2);
447 collect_dfa_stats (&dfa_stats);
449 fprintf (file, "\nDFA Statistics for %s\n\n", funcname);
451 fprintf (file, "---------------------------------------------------------\n");
452 fprintf (file, fmt_str, "", " Number of ", "Memory");
453 fprintf (file, fmt_str, "", " instances ", "used ");
454 fprintf (file, "---------------------------------------------------------\n");
456 size = num_referenced_vars * sizeof (tree);
458 fprintf (file, fmt_str_1, "Referenced variables", (unsigned long)num_referenced_vars,
459 SCALE (size), LABEL (size));
461 size = dfa_stats.num_stmt_anns * sizeof (struct stmt_ann_d);
463 fprintf (file, fmt_str_1, "Statements annotated", dfa_stats.num_stmt_anns,
464 SCALE (size), LABEL (size));
466 size = dfa_stats.num_var_anns * sizeof (struct var_ann_d);
468 fprintf (file, fmt_str_1, "Variables annotated", dfa_stats.num_var_anns,
469 SCALE (size), LABEL (size));
471 size = dfa_stats.num_uses * sizeof (tree *);
473 fprintf (file, fmt_str_1, "USE operands", dfa_stats.num_uses,
474 SCALE (size), LABEL (size));
476 size = dfa_stats.num_defs * sizeof (tree *);
478 fprintf (file, fmt_str_1, "DEF operands", dfa_stats.num_defs,
479 SCALE (size), LABEL (size));
481 size = dfa_stats.num_vuses * sizeof (tree *);
483 fprintf (file, fmt_str_1, "VUSE operands", dfa_stats.num_vuses,
484 SCALE (size), LABEL (size));
486 size = dfa_stats.num_vdefs * sizeof (tree *);
488 fprintf (file, fmt_str_1, "VDEF operands", dfa_stats.num_vdefs,
489 SCALE (size), LABEL (size));
491 size = dfa_stats.num_phis * sizeof (struct tree_phi_node);
493 fprintf (file, fmt_str_1, "PHI nodes", dfa_stats.num_phis,
494 SCALE (size), LABEL (size));
496 size = dfa_stats.num_phi_args * sizeof (struct phi_arg_d);
498 fprintf (file, fmt_str_1, "PHI arguments", dfa_stats.num_phi_args,
499 SCALE (size), LABEL (size));
501 fprintf (file, "---------------------------------------------------------\n");
502 fprintf (file, fmt_str_3, "Total memory used by DFA/SSA data", SCALE (total),
504 fprintf (file, "---------------------------------------------------------\n");
505 fprintf (file, "\n");
507 if (dfa_stats.num_phis)
508 fprintf (file, "Average number of arguments per PHI node: %.1f (max: %d)\n",
509 (float) dfa_stats.num_phi_args / (float) dfa_stats.num_phis,
510 dfa_stats.max_num_phi_args);
512 fprintf (file, "\n");
516 /* Dump DFA statistics on stderr. */
519 debug_dfa_stats (void)
521 dump_dfa_stats (stderr);
525 /* Collect DFA statistics and store them in the structure pointed to by
529 collect_dfa_stats (struct dfa_stats_d *dfa_stats_p)
531 struct pointer_set_t *pset;
533 block_stmt_iterator i;
535 gcc_assert (dfa_stats_p);
537 memset ((void *)dfa_stats_p, 0, sizeof (struct dfa_stats_d));
539 /* Walk all the trees in the function counting references. Start at
540 basic block NUM_FIXED_BLOCKS, but don't stop at block boundaries. */
541 pset = pointer_set_create ();
543 for (i = bsi_start (BASIC_BLOCK (NUM_FIXED_BLOCKS));
544 !bsi_end_p (i); bsi_next (&i))
545 walk_tree (bsi_stmt_ptr (i), collect_dfa_stats_r, (void *) dfa_stats_p,
548 pointer_set_destroy (pset);
553 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
555 dfa_stats_p->num_phis++;
556 dfa_stats_p->num_phi_args += PHI_NUM_ARGS (phi);
557 if (PHI_NUM_ARGS (phi) > dfa_stats_p->max_num_phi_args)
558 dfa_stats_p->max_num_phi_args = PHI_NUM_ARGS (phi);
564 /* Callback for walk_tree to collect DFA statistics for a tree and its
568 collect_dfa_stats_r (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED,
572 struct dfa_stats_d *dfa_stats_p = (struct dfa_stats_d *)data;
576 switch (ann_type (t->base.ann))
580 dfa_stats_p->num_stmt_anns++;
581 dfa_stats_p->num_defs += NUM_SSA_OPERANDS (t, SSA_OP_DEF);
582 dfa_stats_p->num_uses += NUM_SSA_OPERANDS (t, SSA_OP_USE);
583 dfa_stats_p->num_vdefs += NUM_SSA_OPERANDS (t, SSA_OP_VDEF);
584 dfa_stats_p->num_vuses += NUM_SSA_OPERANDS (t, SSA_OP_VUSE);
589 dfa_stats_p->num_var_anns++;
601 /*---------------------------------------------------------------------------
602 Miscellaneous helpers
603 ---------------------------------------------------------------------------*/
604 /* Callback for walk_tree. Used to collect variables referenced in
608 find_vars_r (tree *tp, int *walk_subtrees, void *data ATTRIBUTE_UNUSED)
610 /* If T is a regular variable that the optimizers are interested
611 in, add it to the list of variables. */
613 add_referenced_var (*tp);
615 /* Type, _DECL and constant nodes have no interesting children.
617 else if (IS_TYPE_OR_DECL_P (*tp) || CONSTANT_CLASS_P (*tp))
623 /* Lookup UID in the referenced_vars hashtable and return the associated
627 referenced_var_lookup (unsigned int uid)
630 struct tree_decl_minimal in;
632 h = (tree) htab_find_with_hash (gimple_referenced_vars (cfun), &in, uid);
633 gcc_assert (h || uid == 0);
637 /* Check if TO is in the referenced_vars hash table and insert it if not.
638 Return true if it required insertion. */
641 referenced_var_check_and_insert (tree to)
644 struct tree_decl_minimal in;
645 unsigned int uid = DECL_UID (to);
648 h = (tree) htab_find_with_hash (gimple_referenced_vars (cfun), &in, uid);
651 /* DECL_UID has already been entered in the table. Verify that it is
652 the same entry as TO. See PR 27793. */
653 gcc_assert (h == to);
657 loc = (tree *) htab_find_slot_with_hash (gimple_referenced_vars (cfun),
663 /* Lookup VAR UID in the default_defs hashtable and return the associated
667 gimple_default_def (struct function *fn, tree var)
669 struct tree_decl_minimal ind;
670 struct tree_ssa_name in;
671 gcc_assert (SSA_VAR_P (var));
673 ind.uid = DECL_UID (var);
674 return (tree) htab_find_with_hash (DEFAULT_DEFS (fn), &in, DECL_UID (var));
677 /* Insert the pair VAR's UID, DEF into the default_defs hashtable. */
680 set_default_def (tree var, tree def)
682 struct tree_decl_minimal ind;
683 struct tree_ssa_name in;
686 gcc_assert (SSA_VAR_P (var));
688 ind.uid = DECL_UID (var);
691 loc = htab_find_slot_with_hash (DEFAULT_DEFS (cfun), &in,
692 DECL_UID (var), INSERT);
694 htab_remove_elt (DEFAULT_DEFS (cfun), *loc);
697 gcc_assert (TREE_CODE (def) == SSA_NAME && SSA_NAME_VAR (def) == var);
698 loc = htab_find_slot_with_hash (DEFAULT_DEFS (cfun), &in,
699 DECL_UID (var), INSERT);
701 /* Default definition might be changed by tail call optimization. */
703 SSA_NAME_IS_DEFAULT_DEF (*(tree *) loc) = false;
706 /* Mark DEF as the default definition for VAR. */
707 SSA_NAME_IS_DEFAULT_DEF (def) = true;
710 /* Add VAR to the list of referenced variables if it isn't already there. */
713 add_referenced_var (tree var)
717 v_ann = get_var_ann (var);
718 gcc_assert (DECL_P (var));
720 /* Insert VAR into the referenced_vars has table if it isn't present. */
721 if (referenced_var_check_and_insert (var))
723 /* This is the first time we found this variable, annotate it with
724 attributes that are intrinsic to the variable. */
726 /* Tag's don't have DECL_INITIAL. */
730 /* Scan DECL_INITIAL for pointer variables as they may contain
731 address arithmetic referencing the address of other
733 Even non-constant intializers need to be walked, because
734 IPA passes might prove that their are invariant later on. */
735 if (DECL_INITIAL (var)
736 /* Initializers of external variables are not useful to the
738 && !DECL_EXTERNAL (var))
739 walk_tree (&DECL_INITIAL (var), find_vars_r, NULL, 0);
743 /* Remove VAR from the list. */
746 remove_referenced_var (tree var)
749 struct tree_decl_minimal in;
751 unsigned int uid = DECL_UID (var);
753 clear_call_clobbered (var);
754 v_ann = get_var_ann (var);
756 var->base.ann = NULL;
757 gcc_assert (DECL_P (var));
759 loc = htab_find_slot_with_hash (gimple_referenced_vars (cfun), &in, uid,
761 htab_clear_slot (gimple_referenced_vars (cfun), loc);
765 /* Return the virtual variable associated to the non-scalar variable VAR. */
768 get_virtual_var (tree var)
772 if (TREE_CODE (var) == SSA_NAME)
773 var = SSA_NAME_VAR (var);
775 while (TREE_CODE (var) == REALPART_EXPR || TREE_CODE (var) == IMAGPART_EXPR
776 || handled_component_p (var))
777 var = TREE_OPERAND (var, 0);
779 /* Treating GIMPLE registers as virtual variables makes no sense.
780 Also complain if we couldn't extract a _DECL out of the original
782 gcc_assert (SSA_VAR_P (var));
783 gcc_assert (!is_gimple_reg (var));
788 /* Mark all the naked symbols in STMT for SSA renaming.
790 NOTE: This function should only be used for brand new statements.
791 If the caller is modifying an existing statement, it should use the
792 combination push_stmt_changes/pop_stmt_changes. */
795 mark_symbols_for_renaming (tree stmt)
802 /* Mark all the operands for renaming. */
803 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_ALL_OPERANDS)
805 mark_sym_for_renaming (op);
809 /* Find all variables within the gimplified statement that were not previously
810 visible to the function and add them to the referenced variables list. */
813 find_new_referenced_vars_1 (tree *tp, int *walk_subtrees,
814 void *data ATTRIBUTE_UNUSED)
818 if (TREE_CODE (t) == VAR_DECL && !var_ann (t))
820 add_referenced_var (t);
821 mark_sym_for_renaming (t);
824 if (IS_TYPE_OR_DECL_P (t))
831 find_new_referenced_vars (tree *stmt_p)
833 walk_tree (stmt_p, find_new_referenced_vars_1, NULL, NULL);
837 /* If EXP is a handled component reference for a structure, return the
838 base variable. The access range is delimited by bit positions *POFFSET and
839 *POFFSET + *PMAX_SIZE. The access size is *PSIZE bits. If either
840 *PSIZE or *PMAX_SIZE is -1, they could not be determined. If *PSIZE
841 and *PMAX_SIZE are equal, the access is non-variable. */
844 get_ref_base_and_extent (tree exp, HOST_WIDE_INT *poffset,
845 HOST_WIDE_INT *psize,
846 HOST_WIDE_INT *pmax_size)
848 HOST_WIDE_INT bitsize = -1;
849 HOST_WIDE_INT maxsize = -1;
850 tree size_tree = NULL_TREE;
851 HOST_WIDE_INT bit_offset = 0;
852 bool seen_variable_array_ref = false;
854 gcc_assert (!SSA_VAR_P (exp));
856 /* First get the final access size from just the outermost expression. */
857 if (TREE_CODE (exp) == COMPONENT_REF)
858 size_tree = DECL_SIZE (TREE_OPERAND (exp, 1));
859 else if (TREE_CODE (exp) == BIT_FIELD_REF)
860 size_tree = TREE_OPERAND (exp, 1);
863 enum machine_mode mode = TYPE_MODE (TREE_TYPE (exp));
865 size_tree = TYPE_SIZE (TREE_TYPE (exp));
867 bitsize = GET_MODE_BITSIZE (mode);
869 if (size_tree != NULL_TREE)
871 if (! host_integerp (size_tree, 1))
874 bitsize = TREE_INT_CST_LOW (size_tree);
877 /* Initially, maxsize is the same as the accessed element size.
878 In the following it will only grow (or become -1). */
881 /* Compute cumulative bit-offset for nested component-refs and array-refs,
882 and find the ultimate containing object. */
885 switch (TREE_CODE (exp))
888 bit_offset += tree_low_cst (TREE_OPERAND (exp, 2), 0);
893 tree field = TREE_OPERAND (exp, 1);
894 tree this_offset = component_ref_field_offset (exp);
896 if (this_offset && TREE_CODE (this_offset) == INTEGER_CST)
898 HOST_WIDE_INT hthis_offset = tree_low_cst (this_offset, 0);
900 hthis_offset *= BITS_PER_UNIT;
901 bit_offset += hthis_offset;
902 bit_offset += tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 0);
906 tree csize = TYPE_SIZE (TREE_TYPE (TREE_OPERAND (exp, 0)));
907 /* We need to adjust maxsize to the whole structure bitsize.
908 But we can subtract any constant offset seen sofar,
909 because that would get us out of the structure otherwise. */
910 if (maxsize != -1 && csize && host_integerp (csize, 1))
911 maxsize = TREE_INT_CST_LOW (csize) - bit_offset;
919 case ARRAY_RANGE_REF:
921 tree index = TREE_OPERAND (exp, 1);
922 tree low_bound = array_ref_low_bound (exp);
923 tree unit_size = array_ref_element_size (exp);
925 /* If the resulting bit-offset is constant, track it. */
926 if (host_integerp (index, 0)
927 && host_integerp (low_bound, 0)
928 && host_integerp (unit_size, 1))
930 HOST_WIDE_INT hindex = tree_low_cst (index, 0);
932 hindex -= tree_low_cst (low_bound, 0);
933 hindex *= tree_low_cst (unit_size, 1);
934 hindex *= BITS_PER_UNIT;
935 bit_offset += hindex;
937 /* An array ref with a constant index up in the structure
938 hierarchy will constrain the size of any variable array ref
939 lower in the access hierarchy. */
940 seen_variable_array_ref = false;
944 tree asize = TYPE_SIZE (TREE_TYPE (TREE_OPERAND (exp, 0)));
945 /* We need to adjust maxsize to the whole array bitsize.
946 But we can subtract any constant offset seen sofar,
947 because that would get us outside of the array otherwise. */
948 if (maxsize != -1 && asize && host_integerp (asize, 1))
949 maxsize = TREE_INT_CST_LOW (asize) - bit_offset;
953 /* Remember that we have seen an array ref with a variable
955 seen_variable_array_ref = true;
964 bit_offset += bitsize;
967 case VIEW_CONVERT_EXPR:
968 /* ??? We probably should give up here and bail out. */
975 exp = TREE_OPERAND (exp, 0);
979 /* We need to deal with variable arrays ending structures such as
980 struct { int length; int a[1]; } x; x.a[d]
981 struct { struct { int a; int b; } a[1]; } x; x.a[d].a
982 struct { struct { int a[1]; } a[1]; } x; x.a[0][d], x.a[d][0]
983 where we do not know maxsize for variable index accesses to
984 the array. The simplest way to conservatively deal with this
985 is to punt in the case that offset + maxsize reaches the
986 base type boundary. */
987 if (seen_variable_array_ref
989 && host_integerp (TYPE_SIZE (TREE_TYPE (exp)), 1)
990 && bit_offset + maxsize
991 == (signed)TREE_INT_CST_LOW (TYPE_SIZE (TREE_TYPE (exp))))
994 /* ??? Due to negative offsets in ARRAY_REF we can end up with
995 negative bit_offset here. We might want to store a zero offset
997 *poffset = bit_offset;
999 *pmax_size = maxsize;