/* Alias analysis for trees.
- Copyright (C) 2004, 2005 Free Software Foundation, Inc.
+ Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009
+ Free Software Foundation, Inc.
Contributed by Diego Novillo <dnovillo@redhat.com>
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 2, or (at your option)
+the Free Software Foundation; either version 3, or (at your option)
any later version.
GCC is distributed in the hope that it will be useful,
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
-along with GCC; see the file COPYING. If not, write to
-the Free Software Foundation, 51 Franklin Street, Fifth Floor,
-Boston, MA 02110-1301, USA. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
#include "function.h"
#include "diagnostic.h"
#include "tree-dump.h"
-#include "tree-gimple.h"
+#include "gimple.h"
#include "tree-flow.h"
#include "tree-inline.h"
#include "tree-pass.h"
-#include "tree-ssa-structalias.h"
#include "convert.h"
#include "params.h"
#include "ipa-type-escape.h"
#include "vec.h"
#include "bitmap.h"
#include "vecprim.h"
+#include "pointer-set.h"
+#include "alloc-pool.h"
+#include "tree-ssa-alias.h"
-/* Obstack used to hold grouping bitmaps and other temporary bitmaps used by
- aliasing */
-static bitmap_obstack alias_obstack;
+/* Broad overview of how alias analysis on gimple works:
-/* 'true' after aliases have been computed (see compute_may_aliases). */
-bool aliases_computed_p;
+ Statements clobbering or using memory are linked through the
+ virtual operand factored use-def chain. The virtual operand
+ is unique per function, its symbol is accessible via gimple_vop (cfun).
+ Virtual operands are used for efficiently walking memory statements
+ in the gimple IL and are useful for things like value-numbering as
+ a generation count for memory references.
-/* Structure to map a variable to its alias set and keep track of the
- virtual operands that will be needed to represent it. */
-struct alias_map_d
-{
- /* Variable and its alias set. */
- tree var;
- HOST_WIDE_INT set;
-
- /* Total number of virtual operands that will be needed to represent
- all the aliases of VAR. */
- long total_alias_vops;
-
- /* Nonzero if the aliases for this memory tag have been grouped
- already. Used in group_aliases. */
- unsigned int grouped_p : 1;
-
- /* Set of variables aliased with VAR. This is the exact same
- information contained in VAR_ANN (VAR)->MAY_ALIASES, but in
- bitmap form to speed up alias grouping. */
- bitmap may_aliases;
-};
-
-
-/* Counters used to display statistics on alias analysis. */
-struct alias_stats_d
-{
- unsigned int alias_queries;
- unsigned int alias_mayalias;
- unsigned int alias_noalias;
- unsigned int simple_queries;
- unsigned int simple_resolved;
- unsigned int tbaa_queries;
- unsigned int tbaa_resolved;
- unsigned int structnoaddress_queries;
- unsigned int structnoaddress_resolved;
-};
-
-
-/* Local variables. */
-static struct alias_stats_d alias_stats;
-
-/* Local functions. */
-static void compute_flow_insensitive_aliasing (struct alias_info *);
-static void finalize_ref_all_pointers (struct alias_info *);
-static void dump_alias_stats (FILE *);
-static bool may_alias_p (tree, HOST_WIDE_INT, tree, HOST_WIDE_INT, bool);
-static tree create_memory_tag (tree type, bool is_type_tag);
-static tree get_tmt_for (tree, struct alias_info *);
-static tree get_nmt_for (tree);
-static void add_may_alias (tree, tree);
-static void replace_may_alias (tree, size_t, tree);
-static struct alias_info *init_alias_info (void);
-static void delete_alias_info (struct alias_info *);
-static void compute_flow_sensitive_aliasing (struct alias_info *);
-static void setup_pointers_and_addressables (struct alias_info *);
-static void create_global_var (void);
-static void maybe_create_global_var (struct alias_info *ai);
-static void group_aliases (struct alias_info *);
-static void set_pt_anything (tree ptr);
-
-/* Global declarations. */
-
-/* Call clobbered variables in the function. If bit I is set, then
- REFERENCED_VARS (I) is call-clobbered. */
-bitmap call_clobbered_vars;
-
-/* Addressable variables in the function. If bit I is set, then
- REFERENCED_VARS (I) has had its address taken. Note that
- CALL_CLOBBERED_VARS and ADDRESSABLE_VARS are not related. An
- addressable variable is not necessarily call-clobbered (e.g., a
- local addressable whose address does not escape) and not all
- call-clobbered variables are addressable (e.g., a local static
- variable). */
-bitmap addressable_vars;
-
-/* When the program has too many call-clobbered variables and call-sites,
- this variable is used to represent the clobbering effects of function
- calls. In these cases, all the call clobbered variables in the program
- are forced to alias this variable. This reduces compile times by not
- having to keep track of too many V_MAY_DEF expressions at call sites. */
-tree global_var;
-
-/* qsort comparison function to sort type/name tags by DECL_UID. */
-
-static int
-sort_tags_by_id (const void *pa, const void *pb)
-{
- tree a = *(tree *)pa;
- tree b = *(tree *)pb;
-
- return DECL_UID (a) - DECL_UID (b);
-}
-
-/* Initialize WORKLIST to contain those memory tags that are marked call
- clobbered. Initialized WORKLIST2 to contain the reasons these
- memory tags escaped. */
-
-static void
-init_transitive_clobber_worklist (VEC (tree, heap) **worklist,
- VEC (int, heap) **worklist2)
-{
- referenced_var_iterator rvi;
- tree curr;
-
- FOR_EACH_REFERENCED_VAR (curr, rvi)
- {
- if (MTAG_P (curr) && is_call_clobbered (curr))
- {
- VEC_safe_push (tree, heap, *worklist, curr);
- VEC_safe_push (int, heap, *worklist2, var_ann (curr)->escape_mask);
- }
- }
-}
-
-/* Add ALIAS to WORKLIST (and the reason for escaping REASON to WORKLIST2) if
- ALIAS is not already marked call clobbered, and is a memory
- tag. */
-
-static void
-add_to_worklist (tree alias, VEC (tree, heap) **worklist,
- VEC (int, heap) **worklist2,
- int reason)
-{
- if (MTAG_P (alias) && !is_call_clobbered (alias))
- {
- VEC_safe_push (tree, heap, *worklist, alias);
- VEC_safe_push (int, heap, *worklist2, reason);
- }
-}
-
-/* Mark aliases of TAG as call clobbered, and place any tags on the
- alias list that were not already call clobbered on WORKLIST. */
-
-static void
-mark_aliases_call_clobbered (tree tag, VEC (tree, heap) **worklist,
- VEC (int, heap) **worklist2)
-{
- unsigned int i;
- VEC (tree, gc) *ma;
- tree entry;
- var_ann_t ta = var_ann (tag);
-
- if (!MTAG_P (tag))
- return;
- ma = may_aliases (tag);
- if (!ma)
- return;
-
- for (i = 0; VEC_iterate (tree, ma, i, entry); i++)
- {
- if (!unmodifiable_var_p (entry))
- {
- add_to_worklist (entry, worklist, worklist2, ta->escape_mask);
- mark_call_clobbered (entry, ta->escape_mask);
- }
- }
-}
-
-/* Tags containing global vars need to be marked as global.
- Tags containing call clobbered vars need to be marked as call
- clobbered. */
-
-static void
-compute_tag_properties (void)
-{
- referenced_var_iterator rvi;
- tree tag;
- bool changed = true;
- VEC (tree, heap) *taglist = NULL;
-
- FOR_EACH_REFERENCED_VAR (tag, rvi)
- {
- if (!MTAG_P (tag) || TREE_CODE (tag) == STRUCT_FIELD_TAG)
- continue;
- VEC_safe_push (tree, heap, taglist, tag);
- }
-
- /* We sort the taglist by DECL_UID, for two reasons.
- 1. To get a sequential ordering to make the bitmap accesses
- faster.
- 2. Because of the way we compute aliases, it's more likely that
- an earlier tag is included in a later tag, and this will reduce
- the number of iterations.
-
- If we had a real tag graph, we would just topo-order it and be
- done with it. */
- qsort (VEC_address (tree, taglist),
- VEC_length (tree, taglist),
- sizeof (tree),
- sort_tags_by_id);
-
- /* Go through each tag not marked as global, and if it aliases
- global vars, mark it global.
-
- If the tag contains call clobbered vars, mark it call
- clobbered.
-
- This loop iterates because tags may appear in the may-aliases
- list of other tags when we group. */
-
- while (changed)
- {
- unsigned int k;
-
- changed = false;
- for (k = 0; VEC_iterate (tree, taglist, k, tag); k++)
- {
- VEC (tree, gc) *ma;
- unsigned int i;
- tree entry;
- bool tagcc = is_call_clobbered (tag);
- bool tagglobal = MTAG_GLOBAL (tag);
-
- if (tagcc && tagglobal)
- continue;
-
- ma = may_aliases (tag);
- if (!ma)
- continue;
-
- for (i = 0; VEC_iterate (tree, ma, i, entry); i++)
- {
- /* Call clobbered entries cause the tag to be marked
- call clobbered. */
- if (!tagcc && is_call_clobbered (entry))
- {
- mark_call_clobbered (tag, var_ann (entry)->escape_mask);
- tagcc = true;
- changed = true;
- }
-
- /* Global vars cause the tag to be marked global. */
- if (!tagglobal && is_global_var (entry))
- {
- MTAG_GLOBAL (tag) = true;
- changed = true;
- tagglobal = true;
- }
-
- /* Early exit once both global and cc are set, since the
- loop can't do any more than that. */
- if (tagcc && tagglobal)
- break;
- }
- }
- }
- VEC_free (tree, heap, taglist);
-}
-
-/* Set up the initial variable clobbers and globalness.
- When this function completes, only tags whose aliases need to be
- clobbered will be set clobbered. Tags clobbered because they
- contain call clobbered vars are handled in compute_tag_properties. */
-
-static void
-set_initial_properties (struct alias_info *ai)
-{
- unsigned int i;
- referenced_var_iterator rvi;
- tree var;
- tree ptr;
-
- FOR_EACH_REFERENCED_VAR (var, rvi)
- {
- if (is_global_var (var)
- && (!var_can_have_subvars (var)
- || get_subvars_for_var (var) == NULL))
- {
- if (!unmodifiable_var_p (var))
- mark_call_clobbered (var, ESCAPE_IS_GLOBAL);
- }
- else if (TREE_CODE (var) == PARM_DECL
- && default_def (var)
- && POINTER_TYPE_P (TREE_TYPE (var)))
- {
- tree def = default_def (var);
- get_ptr_info (def)->value_escapes_p = 1;
- get_ptr_info (def)->escape_mask |= ESCAPE_IS_PARM;
- }
- }
-
- for (i = 0; VEC_iterate (tree, ai->processed_ptrs, i, ptr); i++)
- {
- struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
- var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
-
- if (pi->value_escapes_p)
- {
- /* If PTR escapes then its associated memory tags and
- pointed-to variables are call-clobbered. */
- if (pi->name_mem_tag)
- mark_call_clobbered (pi->name_mem_tag, pi->escape_mask);
-
- if (v_ann->symbol_mem_tag)
- mark_call_clobbered (v_ann->symbol_mem_tag, pi->escape_mask);
-
- if (pi->pt_vars)
- {
- bitmap_iterator bi;
- unsigned int j;
- EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
- if (!unmodifiable_var_p (referenced_var (j)))
- mark_call_clobbered (referenced_var (j), pi->escape_mask);
- }
- }
-
- /* If the name tag is call clobbered, so is the symbol tag
- associated with the base VAR_DECL. */
- if (pi->name_mem_tag
- && v_ann->symbol_mem_tag
- && is_call_clobbered (pi->name_mem_tag))
- mark_call_clobbered (v_ann->symbol_mem_tag, pi->escape_mask);
-
- /* Name tags and symbol tags that we don't know where they point
- to, might point to global memory, and thus, are clobbered.
-
- FIXME: This is not quite right. They should only be
- clobbered if value_escapes_p is true, regardless of whether
- they point to global memory or not.
- So removing this code and fixing all the bugs would be nice.
- It is the cause of a bunch of clobbering. */
- if ((pi->pt_global_mem || pi->pt_anything)
- && pi->is_dereferenced && pi->name_mem_tag)
- {
- mark_call_clobbered (pi->name_mem_tag, ESCAPE_IS_GLOBAL);
- MTAG_GLOBAL (pi->name_mem_tag) = true;
- }
-
- if ((pi->pt_global_mem || pi->pt_anything)
- && pi->is_dereferenced
- && v_ann->symbol_mem_tag)
- {
- mark_call_clobbered (v_ann->symbol_mem_tag, ESCAPE_IS_GLOBAL);
- MTAG_GLOBAL (v_ann->symbol_mem_tag) = true;
- }
- }
-}
-
-
-/* This variable is set to true if we are updating the used alone
- information for SMTs, or are in a pass that is going to break it
- temporarily. */
-bool updating_used_alone;
-
-/* Compute which variables need to be marked call clobbered because
- their tag is call clobbered, and which tags need to be marked
- global because they contain global variables. */
-
-static void
-compute_call_clobbered (struct alias_info *ai)
-{
- VEC (tree, heap) *worklist = NULL;
- VEC(int,heap) *worklist2 = NULL;
-
- set_initial_properties (ai);
- init_transitive_clobber_worklist (&worklist, &worklist2);
- while (VEC_length (tree, worklist) != 0)
- {
- tree curr = VEC_pop (tree, worklist);
- int reason = VEC_pop (int, worklist2);
-
- mark_call_clobbered (curr, reason);
- mark_aliases_call_clobbered (curr, &worklist, &worklist2);
- }
- VEC_free (tree, heap, worklist);
- VEC_free (int, heap, worklist2);
- compute_tag_properties ();
-}
-
-
-/* Helper for recalculate_used_alone. Return a conservatively correct
- answer as to whether STMT may make a store on the LHS to SYM. */
-
-static bool
-lhs_may_store_to (tree stmt, tree sym ATTRIBUTE_UNUSED)
-{
- tree lhs = TREE_OPERAND (stmt, 0);
-
- lhs = get_base_address (lhs);
-
- if (!lhs)
- return false;
-
- if (TREE_CODE (lhs) == SSA_NAME)
- return false;
- /* We could do better here by looking at the type tag of LHS, but it
- is unclear whether this is worth it. */
- return true;
-}
-
-/* Recalculate the used_alone information for SMTs . */
-
-void
-recalculate_used_alone (void)
-{
- VEC (tree, heap) *calls = NULL;
- block_stmt_iterator bsi;
- basic_block bb;
- tree stmt;
- size_t i;
- referenced_var_iterator rvi;
- tree var;
-
- /* First, reset all the SMT used alone bits to zero. */
- updating_used_alone = true;
- FOR_EACH_REFERENCED_VAR (var, rvi)
- if (TREE_CODE (var) == SYMBOL_MEMORY_TAG)
- {
- SMT_OLD_USED_ALONE (var) = SMT_USED_ALONE (var);
- SMT_USED_ALONE (var) = 0;
- }
-
- /* Walk all the statements.
- Calls get put into a list of statements to update, since we will
- need to update operands on them if we make any changes.
- If we see a bare use of a SMT anywhere in a real virtual use or virtual
- def, mark the SMT as used alone, and for renaming. */
- FOR_EACH_BB (bb)
- {
- for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
- {
- bool iscall = false;
- ssa_op_iter iter;
-
- stmt = bsi_stmt (bsi);
-
- if (TREE_CODE (stmt) == CALL_EXPR
- || (TREE_CODE (stmt) == MODIFY_EXPR
- && TREE_CODE (TREE_OPERAND (stmt, 1)) == CALL_EXPR))
- {
- iscall = true;
- VEC_safe_push (tree, heap, calls, stmt);
- }
-
- FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter,
- SSA_OP_VUSE | SSA_OP_VIRTUAL_DEFS)
- {
- tree svar = var;
-
- if (TREE_CODE (var) == SSA_NAME)
- svar = SSA_NAME_VAR (var);
-
- if (TREE_CODE (svar) == SYMBOL_MEMORY_TAG)
- {
- /* We only care about the LHS on calls. */
- if (iscall && !lhs_may_store_to (stmt, svar))
- continue;
-
- if (!SMT_USED_ALONE (svar))
- {
- SMT_USED_ALONE (svar) = true;
-
- /* Only need to mark for renaming if it wasn't
- used alone before. */
- if (!SMT_OLD_USED_ALONE (svar))
- mark_sym_for_renaming (svar);
- }
- }
- }
- }
- }
-
- /* Update the operands on all the calls we saw. */
- if (calls)
- {
- for (i = 0; VEC_iterate (tree, calls, i, stmt); i++)
- update_stmt (stmt);
- }
-
- /* We need to mark SMT's that are no longer used for renaming so the
- symbols go away, or else verification will be angry with us, even
- though they are dead. */
- FOR_EACH_REFERENCED_VAR (var, rvi)
- if (TREE_CODE (var) == SYMBOL_MEMORY_TAG)
- {
- if (SMT_OLD_USED_ALONE (var) && !SMT_USED_ALONE (var))
- mark_sym_for_renaming (var);
- }
-
- VEC_free (tree, heap, calls);
- updating_used_alone = false;
-}
-
-/* Compute may-alias information for every variable referenced in function
- FNDECL.
-
- Alias analysis proceeds in 3 main phases:
-
- 1- Points-to and escape analysis.
-
- This phase walks the use-def chains in the SSA web looking for three
- things:
-
- * Assignments of the form P_i = &VAR
- * Assignments of the form P_i = malloc()
- * Pointers and ADDR_EXPR that escape the current function.
-
- The concept of 'escaping' is the same one used in the Java world. When
- a pointer or an ADDR_EXPR escapes, it means that it has been exposed
- outside of the current function. So, assignment to global variables,
- function arguments and returning a pointer are all escape sites, as are
- conversions between pointers and integers.
-
- This is where we are currently limited. Since not everything is renamed
- into SSA, we lose track of escape properties when a pointer is stashed
- inside a field in a structure, for instance. In those cases, we are
- assuming that the pointer does escape.
-
- We use escape analysis to determine whether a variable is
- call-clobbered. Simply put, if an ADDR_EXPR escapes, then the variable
- is call-clobbered. If a pointer P_i escapes, then all the variables
- pointed-to by P_i (and its memory tag) also escape.
-
- 2- Compute flow-sensitive aliases
-
- We have two classes of memory tags. Memory tags associated with the
- pointed-to data type of the pointers in the program. These tags are
- called "symbol memory tag" (SMT). The other class are those associated
- with SSA_NAMEs, called "name memory tag" (NMT). The basic idea is that
- when adding operands for an INDIRECT_REF *P_i, we will first check
- whether P_i has a name tag, if it does we use it, because that will have
- more precise aliasing information. Otherwise, we use the standard symbol
- tag.
-
- In this phase, we go through all the pointers we found in points-to
- analysis and create alias sets for the name memory tags associated with
- each pointer P_i. If P_i escapes, we mark call-clobbered the variables
- it points to and its tag.
-
-
- 3- Compute flow-insensitive aliases
-
- This pass will compare the alias set of every symbol memory tag and
- every addressable variable found in the program. Given a symbol
- memory tag SMT and an addressable variable V. If the alias sets of
- SMT and V conflict (as computed by may_alias_p), then V is marked
- as an alias tag and added to the alias set of SMT.
-
- For instance, consider the following function:
-
- foo (int i)
- {
- int *p, a, b;
-
- if (i > 10)
- p = &a;
- else
- p = &b;
-
- *p = 3;
- a = b + 2;
- return *p;
- }
-
- After aliasing analysis has finished, the symbol memory tag for pointer
- 'p' will have two aliases, namely variables 'a' and 'b'. Every time
- pointer 'p' is dereferenced, we want to mark the operation as a
- potential reference to 'a' and 'b'.
-
- foo (int i)
- {
- int *p, a, b;
-
- if (i_2 > 10)
- p_4 = &a;
- else
- p_6 = &b;
- # p_1 = PHI <p_4(1), p_6(2)>;
-
- # a_7 = V_MAY_DEF <a_3>;
- # b_8 = V_MAY_DEF <b_5>;
- *p_1 = 3;
-
- # a_9 = V_MAY_DEF <a_7>
- # VUSE <b_8>
- a_9 = b_8 + 2;
-
- # VUSE <a_9>;
- # VUSE <b_8>;
- return *p_1;
- }
-
- In certain cases, the list of may aliases for a pointer may grow too
- large. This may cause an explosion in the number of virtual operands
- inserted in the code. Resulting in increased memory consumption and
- compilation time.
-
- When the number of virtual operands needed to represent aliased
- loads and stores grows too large (configurable with @option{--param
- max-aliased-vops}), alias sets are grouped to avoid severe
- compile-time slow downs and memory consumption. See group_aliases. */
-
-static unsigned int
-compute_may_aliases (void)
-{
- struct alias_info *ai;
-
- memset (&alias_stats, 0, sizeof (alias_stats));
-
- /* Initialize aliasing information. */
- ai = init_alias_info ();
-
- /* For each pointer P_i, determine the sets of variables that P_i may
- point-to. For every addressable variable V, determine whether the
- address of V escapes the current function, making V call-clobbered
- (i.e., whether &V is stored in a global variable or if its passed as a
- function call argument). */
- compute_points_to_sets (ai);
-
- /* Collect all pointers and addressable variables, compute alias sets,
- create memory tags for pointers and promote variables whose address is
- not needed anymore. */
- setup_pointers_and_addressables (ai);
-
- /* Compute flow-sensitive, points-to based aliasing for all the name
- memory tags. Note that this pass needs to be done before flow
- insensitive analysis because it uses the points-to information
- gathered before to mark call-clobbered symbol tags. */
- compute_flow_sensitive_aliasing (ai);
-
- /* Compute type-based flow-insensitive aliasing for all the type
- memory tags. */
- compute_flow_insensitive_aliasing (ai);
-
- /* Determine if we need to enable alias grouping. */
- if (ai->total_alias_vops >= MAX_ALIASED_VOPS)
- group_aliases (ai);
-
- /* Compute call clobbering information. */
- compute_call_clobbered (ai);
-
- /* If the program has too many call-clobbered variables and/or function
- calls, create .GLOBAL_VAR and use it to model call-clobbering
- semantics at call sites. This reduces the number of virtual operands
- considerably, improving compile times at the expense of lost
- aliasing precision. */
- maybe_create_global_var (ai);
-
- /* If the program contains ref-all pointers, finalize may-alias information
- for them. This pass needs to be run after call-clobbering information
- has been computed. */
- if (ai->ref_all_symbol_mem_tag)
- finalize_ref_all_pointers (ai);
-
- /* Debugging dumps. */
- if (dump_file)
- {
- dump_referenced_vars (dump_file);
- if (dump_flags & TDF_STATS)
- dump_alias_stats (dump_file);
- dump_points_to_info (dump_file);
- dump_alias_info (dump_file);
- }
-
- /* Deallocate memory used by aliasing data structures. */
- delete_alias_info (ai);
-
- updating_used_alone = true;
- {
- block_stmt_iterator bsi;
- basic_block bb;
- FOR_EACH_BB (bb)
- {
- for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
- {
- update_stmt_if_modified (bsi_stmt (bsi));
- }
- }
- }
- recalculate_used_alone ();
- updating_used_alone = false;
- return 0;
-}
-
-
-struct tree_opt_pass pass_may_alias =
-{
- "alias", /* name */
- NULL, /* gate */
- compute_may_aliases, /* execute */
- NULL, /* sub */
- NULL, /* next */
- 0, /* static_pass_number */
- TV_TREE_MAY_ALIAS, /* tv_id */
- PROP_cfg | PROP_ssa, /* properties_required */
- PROP_alias, /* properties_provided */
- 0, /* properties_destroyed */
- 0, /* todo_flags_start */
- TODO_dump_func | TODO_update_ssa
- | TODO_ggc_collect | TODO_verify_ssa
- | TODO_verify_stmts, /* todo_flags_finish */
- 0 /* letter */
-};
-
-
-/* Data structure used to count the number of dereferences to PTR
- inside an expression. */
-struct count_ptr_d
-{
- tree ptr;
- unsigned count;
-};
-
-
-/* Helper for count_uses_and_derefs. Called by walk_tree to look for
- (ALIGN/MISALIGNED_)INDIRECT_REF nodes for the pointer passed in DATA. */
-
-static tree
-count_ptr_derefs (tree *tp, int *walk_subtrees, void *data)
-{
- struct count_ptr_d *count_p = (struct count_ptr_d *) data;
-
- /* Do not walk inside ADDR_EXPR nodes. In the expression &ptr->fld,
- pointer 'ptr' is *not* dereferenced, it is simply used to compute
- the address of 'fld' as 'ptr + offsetof(fld)'. */
- if (TREE_CODE (*tp) == ADDR_EXPR)
- {
- *walk_subtrees = 0;
- return NULL_TREE;
- }
-
- if (INDIRECT_REF_P (*tp) && TREE_OPERAND (*tp, 0) == count_p->ptr)
- count_p->count++;
-
- return NULL_TREE;
-}
-
-
-/* Count the number of direct and indirect uses for pointer PTR in
- statement STMT. The two counts are stored in *NUM_USES_P and
- *NUM_DEREFS_P respectively. *IS_STORE_P is set to 'true' if at
- least one of those dereferences is a store operation. */
-
-void
-count_uses_and_derefs (tree ptr, tree stmt, unsigned *num_uses_p,
- unsigned *num_derefs_p, bool *is_store)
-{
- ssa_op_iter i;
- tree use;
-
- *num_uses_p = 0;
- *num_derefs_p = 0;
- *is_store = false;
-
- /* Find out the total number of uses of PTR in STMT. */
- FOR_EACH_SSA_TREE_OPERAND (use, stmt, i, SSA_OP_USE)
- if (use == ptr)
- (*num_uses_p)++;
-
- /* Now count the number of indirect references to PTR. This is
- truly awful, but we don't have much choice. There are no parent
- pointers inside INDIRECT_REFs, so an expression like
- '*x_1 = foo (x_1, *x_1)' needs to be traversed piece by piece to
- find all the indirect and direct uses of x_1 inside. The only
- shortcut we can take is the fact that GIMPLE only allows
- INDIRECT_REFs inside the expressions below. */
- if (TREE_CODE (stmt) == MODIFY_EXPR
- || (TREE_CODE (stmt) == RETURN_EXPR
- && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR)
- || TREE_CODE (stmt) == ASM_EXPR
- || TREE_CODE (stmt) == CALL_EXPR)
- {
- tree lhs, rhs;
-
- if (TREE_CODE (stmt) == MODIFY_EXPR)
- {
- lhs = TREE_OPERAND (stmt, 0);
- rhs = TREE_OPERAND (stmt, 1);
- }
- else if (TREE_CODE (stmt) == RETURN_EXPR)
- {
- tree e = TREE_OPERAND (stmt, 0);
- lhs = TREE_OPERAND (e, 0);
- rhs = TREE_OPERAND (e, 1);
- }
- else if (TREE_CODE (stmt) == ASM_EXPR)
- {
- lhs = ASM_OUTPUTS (stmt);
- rhs = ASM_INPUTS (stmt);
- }
- else
- {
- lhs = NULL_TREE;
- rhs = stmt;
- }
-
- if (lhs && (TREE_CODE (lhs) == TREE_LIST || EXPR_P (lhs)))
- {
- struct count_ptr_d count;
- count.ptr = ptr;
- count.count = 0;
- walk_tree (&lhs, count_ptr_derefs, &count, NULL);
- *is_store = true;
- *num_derefs_p = count.count;
- }
-
- if (rhs && (TREE_CODE (rhs) == TREE_LIST || EXPR_P (rhs)))
- {
- struct count_ptr_d count;
- count.ptr = ptr;
- count.count = 0;
- walk_tree (&rhs, count_ptr_derefs, &count, NULL);
- *num_derefs_p += count.count;
- }
- }
-
- gcc_assert (*num_uses_p >= *num_derefs_p);
-}
-
-/* Initialize the data structures used for alias analysis. */
-
-static struct alias_info *
-init_alias_info (void)
-{
- struct alias_info *ai;
- referenced_var_iterator rvi;
- tree var;
-
- bitmap_obstack_initialize (&alias_obstack);
- ai = XCNEW (struct alias_info);
- ai->ssa_names_visited = sbitmap_alloc (num_ssa_names);
- sbitmap_zero (ai->ssa_names_visited);
- ai->processed_ptrs = VEC_alloc (tree, heap, 50);
- ai->written_vars = BITMAP_ALLOC (&alias_obstack);
- ai->dereferenced_ptrs_store = BITMAP_ALLOC (&alias_obstack);
- ai->dereferenced_ptrs_load = BITMAP_ALLOC (&alias_obstack);
-
- /* If aliases have been computed before, clear existing information. */
- if (aliases_computed_p)
- {
- unsigned i;
-
- /* Similarly, clear the set of addressable variables. In this
- case, we can just clear the set because addressability is
- only computed here. */
- bitmap_clear (addressable_vars);
-
- /* Clear flow-insensitive alias information from each symbol. */
- FOR_EACH_REFERENCED_VAR (var, rvi)
- {
- var_ann_t ann = var_ann (var);
-
- ann->is_aliased = 0;
- ann->may_aliases = NULL;
- NUM_REFERENCES_CLEAR (ann);
-
- /* Since we are about to re-discover call-clobbered
- variables, clear the call-clobbered flag. Variables that
- are intrinsically call-clobbered (globals, local statics,
- etc) will not be marked by the aliasing code, so we can't
- remove them from CALL_CLOBBERED_VARS.
-
- NB: STRUCT_FIELDS are still call clobbered if they are for
- a global variable, so we *don't* clear their call clobberedness
- just because they are tags, though we will clear it if they
- aren't for global variables. */
- if (TREE_CODE (var) == NAME_MEMORY_TAG
- || TREE_CODE (var) == SYMBOL_MEMORY_TAG
- || !is_global_var (var))
- clear_call_clobbered (var);
- }
-
- /* Clear flow-sensitive points-to information from each SSA name. */
- for (i = 1; i < num_ssa_names; i++)
- {
- tree name = ssa_name (i);
-
- if (!name || !POINTER_TYPE_P (TREE_TYPE (name)))
- continue;
-
- if (SSA_NAME_PTR_INFO (name))
- {
- struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
-
- /* Clear all the flags but keep the name tag to
- avoid creating new temporaries unnecessarily. If
- this pointer is found to point to a subset or
- superset of its former points-to set, then a new
- tag will need to be created in create_name_tags. */
- pi->pt_anything = 0;
- pi->pt_null = 0;
- pi->value_escapes_p = 0;
- pi->is_dereferenced = 0;
- if (pi->pt_vars)
- bitmap_clear (pi->pt_vars);
- }
- }
- }
-
- /* Next time, we will need to reset alias information. */
- aliases_computed_p = true;
-
- return ai;
-}
-
-
-/* Deallocate memory used by alias analysis. */
-
-static void
-delete_alias_info (struct alias_info *ai)
-{
- size_t i;
- referenced_var_iterator rvi;
- tree var;
-
- sbitmap_free (ai->ssa_names_visited);
- VEC_free (tree, heap, ai->processed_ptrs);
-
- for (i = 0; i < ai->num_addressable_vars; i++)
- free (ai->addressable_vars[i]);
-
- FOR_EACH_REFERENCED_VAR(var, rvi)
- {
- var_ann_t ann = var_ann (var);
- NUM_REFERENCES_CLEAR (ann);
- }
-
- free (ai->addressable_vars);
-
- for (i = 0; i < ai->num_pointers; i++)
- free (ai->pointers[i]);
- free (ai->pointers);
-
- BITMAP_FREE (ai->written_vars);
- BITMAP_FREE (ai->dereferenced_ptrs_store);
- BITMAP_FREE (ai->dereferenced_ptrs_load);
- bitmap_obstack_release (&alias_obstack);
- free (ai);
-
- delete_points_to_sets ();
-}
-
-/* Create name tags for all the pointers that have been dereferenced.
- We only create a name tag for a pointer P if P is found to point to
- a set of variables (so that we can alias them to *P) or if it is
- the result of a call to malloc (which means that P cannot point to
- anything else nor alias any other variable).
-
- If two pointers P and Q point to the same set of variables, they
- are assigned the same name tag. */
-
-static void
-create_name_tags (void)
-{
- size_t i;
- VEC (tree, heap) *with_ptvars = NULL;
- tree ptr;
-
- /* Collect the list of pointers with a non-empty points to set. */
- for (i = 1; i < num_ssa_names; i++)
- {
- tree ptr = ssa_name (i);
- struct ptr_info_def *pi;
-
- if (!ptr
- || !POINTER_TYPE_P (TREE_TYPE (ptr))
- || !SSA_NAME_PTR_INFO (ptr))
- continue;
-
- pi = SSA_NAME_PTR_INFO (ptr);
-
- if (pi->pt_anything || !pi->is_dereferenced)
- {
- /* No name tags for pointers that have not been
- dereferenced or point to an arbitrary location. */
- pi->name_mem_tag = NULL_TREE;
- continue;
- }
-
- /* Set pt_anything on the pointers without pt_vars filled in so
- that they are assigned a symbol tag. */
- if (pi->pt_vars && !bitmap_empty_p (pi->pt_vars))
- VEC_safe_push (tree, heap, with_ptvars, ptr);
- else
- set_pt_anything (ptr);
- }
-
- /* If we didn't find any pointers with pt_vars set, we're done. */
- if (!with_ptvars)
- return;
-
- /* Now go through the pointers with pt_vars, and find a name tag
- with the same pt_vars as this pointer, or create one if one
- doesn't exist. */
- for (i = 0; VEC_iterate (tree, with_ptvars, i, ptr); i++)
- {
- struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
- size_t j;
- tree ptr2;
- tree old_name_tag = pi->name_mem_tag;
-
- /* If PTR points to a set of variables, check if we don't
- have another pointer Q with the same points-to set before
- creating a tag. If so, use Q's tag instead of creating a
- new one.
-
- This is important for not creating unnecessary symbols
- and also for copy propagation. If we ever need to
- propagate PTR into Q or vice-versa, we would run into
- problems if they both had different name tags because
- they would have different SSA version numbers (which
- would force us to take the name tags in and out of SSA). */
- for (j = 0; j < i && VEC_iterate (tree, with_ptvars, j, ptr2); j++)
- {
- struct ptr_info_def *qi = SSA_NAME_PTR_INFO (ptr2);
-
- if (bitmap_equal_p (pi->pt_vars, qi->pt_vars))
- {
- pi->name_mem_tag = qi->name_mem_tag;
- break;
- }
- }
-
- /* If we didn't find a pointer with the same points-to set
- as PTR, create a new name tag if needed. */
- if (pi->name_mem_tag == NULL_TREE)
- pi->name_mem_tag = get_nmt_for (ptr);
-
- /* If the new name tag computed for PTR is different than
- the old name tag that it used to have, then the old tag
- needs to be removed from the IL, so we mark it for
- renaming. */
- if (old_name_tag && old_name_tag != pi->name_mem_tag)
- mark_sym_for_renaming (old_name_tag);
-
- TREE_THIS_VOLATILE (pi->name_mem_tag)
- |= TREE_THIS_VOLATILE (TREE_TYPE (TREE_TYPE (ptr)));
-
- /* Mark the new name tag for renaming. */
- mark_sym_for_renaming (pi->name_mem_tag);
- }
-
- VEC_free (tree, heap, with_ptvars);
-}
-
-
-/* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for
- the name memory tag (NMT) associated with P_i. If P_i escapes, then its
- name tag and the variables it points-to are call-clobbered. Finally, if
- P_i escapes and we could not determine where it points to, then all the
- variables in the same alias set as *P_i are marked call-clobbered. This
- is necessary because we must assume that P_i may take the address of any
- variable in the same alias set. */
-
-static void
-compute_flow_sensitive_aliasing (struct alias_info *ai)
-{
- size_t i;
- tree ptr;
-
- for (i = 0; VEC_iterate (tree, ai->processed_ptrs, i, ptr); i++)
- {
- if (!find_what_p_points_to (ptr))
- set_pt_anything (ptr);
- }
-
- create_name_tags ();
-
- for (i = 0; VEC_iterate (tree, ai->processed_ptrs, i, ptr); i++)
- {
- unsigned j;
- struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
- var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
- bitmap_iterator bi;
-
-
- /* Set up aliasing information for PTR's name memory tag (if it has
- one). Note that only pointers that have been dereferenced will
- have a name memory tag. */
- if (pi->name_mem_tag && pi->pt_vars)
- EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
- {
- add_may_alias (pi->name_mem_tag, referenced_var (j));
- add_may_alias (v_ann->symbol_mem_tag, referenced_var (j));
- }
- }
-}
-
-
-/* Compute type-based alias sets. Traverse all the pointers and
- addressable variables found in setup_pointers_and_addressables.
-
- For every pointer P in AI->POINTERS and addressable variable V in
- AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's symbol
- memory tag (SMT) if their alias sets conflict. V is then marked as
- an alias tag so that the operand scanner knows that statements
- containing V have aliased operands. */
-
-static void
-compute_flow_insensitive_aliasing (struct alias_info *ai)
-{
- size_t i;
-
- /* Initialize counter for the total number of virtual operands that
- aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the
- threshold set by --params max-alias-vops, we enable alias
- grouping. */
- ai->total_alias_vops = 0;
-
- /* For every pointer P, determine which addressable variables may alias
- with P's symbol memory tag. */
- for (i = 0; i < ai->num_pointers; i++)
- {
- size_t j;
- struct alias_map_d *p_map = ai->pointers[i];
- tree tag = var_ann (p_map->var)->symbol_mem_tag;
- var_ann_t tag_ann = var_ann (tag);
- tree var;
-
- /* Call-clobbering information is not finalized yet at this point. */
- if (PTR_IS_REF_ALL (p_map->var))
- continue;
-
- p_map->total_alias_vops = 0;
- p_map->may_aliases = BITMAP_ALLOC (&alias_obstack);
-
- /* Add any pre-existing may_aliases to the bitmap used to represent
- TAG's alias set in case we need to group aliases. */
- for (j = 0; VEC_iterate (tree, tag_ann->may_aliases, j, var); ++j)
- bitmap_set_bit (p_map->may_aliases, DECL_UID (var));
-
- for (j = 0; j < ai->num_addressable_vars; j++)
- {
- struct alias_map_d *v_map;
- var_ann_t v_ann;
- bool tag_stored_p, var_stored_p;
-
- v_map = ai->addressable_vars[j];
- var = v_map->var;
- v_ann = var_ann (var);
-
- /* Skip memory tags and variables that have never been
- written to. We also need to check if the variables are
- call-clobbered because they may be overwritten by
- function calls.
-
- Note this is effectively random accessing elements in
- the sparse bitset, which can be highly inefficient.
- So we first check the call_clobbered status of the
- tag and variable before querying the bitmap. */
- tag_stored_p = is_call_clobbered (tag)
- || bitmap_bit_p (ai->written_vars, DECL_UID (tag));
- var_stored_p = is_call_clobbered (var)
- || bitmap_bit_p (ai->written_vars, DECL_UID (var));
- if (!tag_stored_p && !var_stored_p)
- continue;
-
- if (may_alias_p (p_map->var, p_map->set, var, v_map->set, false))
- {
- size_t num_tag_refs, num_var_refs;
-
- num_tag_refs = NUM_REFERENCES (tag_ann);
- num_var_refs = NUM_REFERENCES (v_ann);
-
- /* Add VAR to TAG's may-aliases set. */
-
- /* We should never have a var with subvars here, because
- they shouldn't get into the set of addressable vars */
- gcc_assert (!var_can_have_subvars (var)
- || get_subvars_for_var (var) == NULL);
-
- add_may_alias (tag, var);
- /* Update the bitmap used to represent TAG's alias set
- in case we need to group aliases. */
- bitmap_set_bit (p_map->may_aliases, DECL_UID (var));
-
- /* Update the total number of virtual operands due to
- aliasing. Since we are adding one more alias to TAG's
- may-aliases set, the total number of virtual operands due
- to aliasing will be increased by the number of references
- made to VAR and TAG (every reference to TAG will also
- count as a reference to VAR). */
- ai->total_alias_vops += (num_var_refs + num_tag_refs);
- p_map->total_alias_vops += (num_var_refs + num_tag_refs);
-
-
- }
- }
- }
+ SSA_NAME pointers may have associated points-to information
+ accessible via the SSA_NAME_PTR_INFO macro. Flow-insensitive
+ points-to information is (re-)computed by the TODO_rebuild_alias
+ pass manager todo. Points-to information is also used for more
+ precise tracking of call-clobbered and call-used variables and
+ related disambiguations.
- /* Since this analysis is based exclusively on symbols, it fails to
- handle cases where two pointers P and Q have different memory
- tags with conflicting alias set numbers but no aliased symbols in
- common.
-
- For example, suppose that we have two memory tags SMT.1 and SMT.2
- such that
-
- may-aliases (SMT.1) = { a }
- may-aliases (SMT.2) = { b }
-
- and the alias set number of SMT.1 conflicts with that of SMT.2.
- Since they don't have symbols in common, loads and stores from
- SMT.1 and SMT.2 will seem independent of each other, which will
- lead to the optimizers making invalid transformations (see
- testsuite/gcc.c-torture/execute/pr15262-[12].c).
-
- To avoid this problem, we do a final traversal of AI->POINTERS
- looking for pairs of pointers that have no aliased symbols in
- common and yet have conflicting alias set numbers. */
- for (i = 0; i < ai->num_pointers; i++)
- {
- size_t j;
- struct alias_map_d *p_map1 = ai->pointers[i];
- tree tag1 = var_ann (p_map1->var)->symbol_mem_tag;
- bitmap may_aliases1 = p_map1->may_aliases;
-
- if (PTR_IS_REF_ALL (p_map1->var))
- continue;
-
- for (j = i + 1; j < ai->num_pointers; j++)
- {
- struct alias_map_d *p_map2 = ai->pointers[j];
- tree tag2 = var_ann (p_map2->var)->symbol_mem_tag;
- bitmap may_aliases2 = p_map2->may_aliases;
-
- if (PTR_IS_REF_ALL (p_map2->var))
- continue;
-
- /* If the pointers may not point to each other, do nothing. */
- if (!may_alias_p (p_map1->var, p_map1->set, tag2, p_map2->set, true))
- continue;
-
- /* The two pointers may alias each other. If they already have
- symbols in common, do nothing. */
- if (bitmap_intersect_p (may_aliases1, may_aliases2))
- continue;
-
- if (!bitmap_empty_p (may_aliases2))
- {
- unsigned int k;
- bitmap_iterator bi;
-
- /* Add all the aliases for TAG2 into TAG1's alias set.
- FIXME, update grouping heuristic counters. */
- EXECUTE_IF_SET_IN_BITMAP (may_aliases2, 0, k, bi)
- add_may_alias (tag1, referenced_var (k));
- bitmap_ior_into (may_aliases1, may_aliases2);
- }
- else
- {
- /* Since TAG2 does not have any aliases of its own, add
- TAG2 itself to the alias set of TAG1. */
- add_may_alias (tag1, tag2);
- bitmap_set_bit (may_aliases1, DECL_UID (tag2));
- }
- }
- }
-
- if (dump_file)
- fprintf (dump_file, "\n%s: Total number of aliased vops: %ld\n",
- get_name (current_function_decl),
- ai->total_alias_vops);
-}
-
-
-/* Finalize may-alias information for ref-all pointers. Traverse all
- the addressable variables found in setup_pointers_and_addressables.
-
- If flow-sensitive alias analysis has attached a name memory tag to
- a ref-all pointer, we will use it for the dereferences because that
- will have more precise aliasing information. But if there is no
- name tag, we will use a special symbol tag that aliases all the
- call-clobbered addressable variables. */
-
-static void
-finalize_ref_all_pointers (struct alias_info *ai)
-{
- size_t i;
-
- if (global_var)
- add_may_alias (ai->ref_all_symbol_mem_tag, global_var);
- else
- {
- /* First add the real call-clobbered variables. */
- for (i = 0; i < ai->num_addressable_vars; i++)
- {
- tree var = ai->addressable_vars[i]->var;
- if (is_call_clobbered (var))
- add_may_alias (ai->ref_all_symbol_mem_tag, var);
- }
-
- /* Then add the call-clobbered pointer memory tags. See
- compute_flow_insensitive_aliasing for the rationale. */
- for (i = 0; i < ai->num_pointers; i++)
- {
- tree ptr = ai->pointers[i]->var, tag;
- if (PTR_IS_REF_ALL (ptr))
- continue;
- tag = var_ann (ptr)->symbol_mem_tag;
- if (is_call_clobbered (tag))
- add_may_alias (ai->ref_all_symbol_mem_tag, tag);
- }
- }
-}
-
-
-/* Comparison function for qsort used in group_aliases. */
-
-static int
-total_alias_vops_cmp (const void *p, const void *q)
-{
- const struct alias_map_d **p1 = (const struct alias_map_d **)p;
- const struct alias_map_d **p2 = (const struct alias_map_d **)q;
- long n1 = (*p1)->total_alias_vops;
- long n2 = (*p2)->total_alias_vops;
-
- /* We want to sort in descending order. */
- return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1);
-}
-
-/* Group all the aliases for TAG to make TAG represent all the
- variables in its alias set. Update the total number
- of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
- function will make TAG be the unique alias tag for all the
- variables in its may-aliases. So, given:
-
- may-aliases(TAG) = { V1, V2, V3 }
-
- This function will group the variables into:
-
- may-aliases(V1) = { TAG }
- may-aliases(V2) = { TAG }
- may-aliases(V2) = { TAG } */
-
-static void
-group_aliases_into (tree tag, bitmap tag_aliases, struct alias_info *ai)
-{
- unsigned int i;
- var_ann_t tag_ann = var_ann (tag);
- size_t num_tag_refs = NUM_REFERENCES (tag_ann);
- bitmap_iterator bi;
-
- EXECUTE_IF_SET_IN_BITMAP (tag_aliases, 0, i, bi)
- {
- tree var = referenced_var (i);
- var_ann_t ann = var_ann (var);
-
- /* Make TAG the unique alias of VAR. */
- ann->is_aliased = 0;
- ann->may_aliases = NULL;
-
- /* Note that VAR and TAG may be the same if the function has no
- addressable variables (see the discussion at the end of
- setup_pointers_and_addressables). */
- if (var != tag)
- add_may_alias (var, tag);
-
- /* Reduce total number of virtual operands contributed
- by TAG on behalf of VAR. Notice that the references to VAR
- itself won't be removed. We will merely replace them with
- references to TAG. */
- ai->total_alias_vops -= num_tag_refs;
- }
-
- /* We have reduced the number of virtual operands that TAG makes on
- behalf of all the variables formerly aliased with it. However,
- we have also "removed" all the virtual operands for TAG itself,
- so we add them back. */
- ai->total_alias_vops += num_tag_refs;
-
- /* TAG no longer has any aliases. */
- tag_ann->may_aliases = NULL;
-}
-
-
-/* Group may-aliases sets to reduce the number of virtual operands due
- to aliasing.
-
- 1- Sort the list of pointers in decreasing number of contributed
- virtual operands.
-
- 2- Take the first entry in AI->POINTERS and revert the role of
- the memory tag and its aliases. Usually, whenever an aliased
- variable Vi is found to alias with a memory tag T, we add Vi
- to the may-aliases set for T. Meaning that after alias
- analysis, we will have:
-
- may-aliases(T) = { V1, V2, V3, ..., Vn }
-
- This means that every statement that references T, will get 'n'
- virtual operands for each of the Vi tags. But, when alias
- grouping is enabled, we make T an alias tag and add it to the
- alias set of all the Vi variables:
-
- may-aliases(V1) = { T }
- may-aliases(V2) = { T }
- ...
- may-aliases(Vn) = { T }
-
- This has two effects: (a) statements referencing T will only get
- a single virtual operand, and, (b) all the variables Vi will now
- appear to alias each other. So, we lose alias precision to
- improve compile time. But, in theory, a program with such a high
- level of aliasing should not be very optimizable in the first
- place.
-
- 3- Since variables may be in the alias set of more than one
- memory tag, the grouping done in step (2) needs to be extended
- to all the memory tags that have a non-empty intersection with
- the may-aliases set of tag T. For instance, if we originally
- had these may-aliases sets:
-
- may-aliases(T) = { V1, V2, V3 }
- may-aliases(R) = { V2, V4 }
-
- In step (2) we would have reverted the aliases for T as:
-
- may-aliases(V1) = { T }
- may-aliases(V2) = { T }
- may-aliases(V3) = { T }
-
- But note that now V2 is no longer aliased with R. We could
- add R to may-aliases(V2), but we are in the process of
- grouping aliases to reduce virtual operands so what we do is
- add V4 to the grouping to obtain:
-
- may-aliases(V1) = { T }
- may-aliases(V2) = { T }
- may-aliases(V3) = { T }
- may-aliases(V4) = { T }
-
- 4- If the total number of virtual operands due to aliasing is
- still above the threshold set by max-alias-vops, go back to (2). */
-
-static void
-group_aliases (struct alias_info *ai)
-{
- size_t i;
- tree ptr;
-
- /* Sort the POINTERS array in descending order of contributed
- virtual operands. */
- qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *),
- total_alias_vops_cmp);
-
- /* For every pointer in AI->POINTERS, reverse the roles of its tag
- and the tag's may-aliases set. */
- for (i = 0; i < ai->num_pointers; i++)
- {
- size_t j;
- tree tag1 = var_ann (ai->pointers[i]->var)->symbol_mem_tag;
- bitmap tag1_aliases = ai->pointers[i]->may_aliases;
-
- /* Skip tags that have been grouped already. */
- if (ai->pointers[i]->grouped_p)
- continue;
+ This file contains functions for disambiguating memory references,
+ the so called alias-oracle and tools for walking of the gimple IL.
- /* See if TAG1 had any aliases in common with other symbol tags.
- If we find a TAG2 with common aliases with TAG1, add TAG2's
- aliases into TAG1. */
- for (j = i + 1; j < ai->num_pointers; j++)
- {
- bitmap tag2_aliases = ai->pointers[j]->may_aliases;
-
- if (bitmap_intersect_p (tag1_aliases, tag2_aliases))
- {
- tree tag2 = var_ann (ai->pointers[j]->var)->symbol_mem_tag;
+ The main alias-oracle entry-points are
- bitmap_ior_into (tag1_aliases, tag2_aliases);
+ bool stmt_may_clobber_ref_p (gimple, tree)
- /* TAG2 does not need its aliases anymore. */
- bitmap_clear (tag2_aliases);
- var_ann (tag2)->may_aliases = NULL;
+ This function queries if a statement may invalidate (parts of)
+ the memory designated by the reference tree argument.
- /* TAG1 is the unique alias of TAG2. */
- add_may_alias (tag2, tag1);
-
- ai->pointers[j]->grouped_p = true;
- }
- }
+ bool ref_maybe_used_by_stmt_p (gimple, tree)
- /* Now group all the aliases we collected into TAG1. */
- group_aliases_into (tag1, tag1_aliases, ai);
+ This function queries if a statement may need (parts of) the
+ memory designated by the reference tree argument.
- /* If we've reduced total number of virtual operands below the
- threshold, stop. */
- if (ai->total_alias_vops < MAX_ALIASED_VOPS)
- break;
- }
+ There are variants of these functions that only handle the call
+ part of a statement, call_may_clobber_ref_p and ref_maybe_used_by_call_p.
+ Note that these do not disambiguate against a possible call lhs.
- /* Finally, all the variables that have been grouped cannot be in
- the may-alias set of name memory tags. Suppose that we have
- grouped the aliases in this code so that may-aliases(a) = SMT.20
-
- p_5 = &a;
- ...
- # a_9 = V_MAY_DEF <a_8>
- p_5->field = 0
- ... Several modifications to SMT.20 ...
- # VUSE <a_9>
- x_30 = p_5->field
-
- Since p_5 points to 'a', the optimizers will try to propagate 0
- into p_5->field, but that is wrong because there have been
- modifications to 'SMT.20' in between. To prevent this we have to
- replace 'a' with 'SMT.20' in the name tag of p_5. */
- for (i = 0; VEC_iterate (tree, ai->processed_ptrs, i, ptr); i++)
- {
- size_t j;
- tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag;
- VEC(tree,gc) *aliases;
- tree alias;
-
- if (name_tag == NULL_TREE)
- continue;
+ bool refs_may_alias_p (tree, tree)
- aliases = var_ann (name_tag)->may_aliases;
- for (j = 0; VEC_iterate (tree, aliases, j, alias); j++)
- {
- var_ann_t ann = var_ann (alias);
+ This function tries to disambiguate two reference trees.
- if ((!MTAG_P (alias)
- || TREE_CODE (alias) == STRUCT_FIELD_TAG)
- && ann->may_aliases)
- {
- tree new_alias;
+ bool ptr_deref_may_alias_global_p (tree)
- gcc_assert (VEC_length (tree, ann->may_aliases) == 1);
+ This function queries if dereferencing a pointer variable may
+ alias global memory.
- new_alias = VEC_index (tree, ann->may_aliases, 0);
- replace_may_alias (name_tag, j, new_alias);
- }
- }
- }
+ More low-level disambiguators are available and documented in
+ this file. Low-level disambiguators dealing with points-to
+ information are in tree-ssa-structalias.c. */
- if (dump_file)
- fprintf (dump_file,
- "%s: Total number of aliased vops after grouping: %ld%s\n",
- get_name (current_function_decl),
- ai->total_alias_vops,
- (ai->total_alias_vops < 0) ? " (negative values are OK)" : "");
-}
+/* Query statistics for the different low-level disambiguators.
+ A high-level query may trigger multiple of them. */
-/* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
+static struct {
+ unsigned HOST_WIDE_INT refs_may_alias_p_may_alias;
+ unsigned HOST_WIDE_INT refs_may_alias_p_no_alias;
+ unsigned HOST_WIDE_INT ref_maybe_used_by_call_p_may_alias;
+ unsigned HOST_WIDE_INT ref_maybe_used_by_call_p_no_alias;
+ unsigned HOST_WIDE_INT call_may_clobber_ref_p_may_alias;
+ unsigned HOST_WIDE_INT call_may_clobber_ref_p_no_alias;
+} alias_stats;
-static void
-create_alias_map_for (tree var, struct alias_info *ai)
-{
- struct alias_map_d *alias_map;
- alias_map = XCNEW (struct alias_map_d);
- alias_map->var = var;
- alias_map->set = get_alias_set (var);
- ai->addressable_vars[ai->num_addressable_vars++] = alias_map;
+void
+dump_alias_stats (FILE *s)
+{
+ fprintf (s, "\nAlias oracle query stats:\n");
+ fprintf (s, " refs_may_alias_p: "
+ HOST_WIDE_INT_PRINT_DEC" disambiguations, "
+ HOST_WIDE_INT_PRINT_DEC" queries\n",
+ alias_stats.refs_may_alias_p_no_alias,
+ alias_stats.refs_may_alias_p_no_alias
+ + alias_stats.refs_may_alias_p_may_alias);
+ fprintf (s, " ref_maybe_used_by_call_p: "
+ HOST_WIDE_INT_PRINT_DEC" disambiguations, "
+ HOST_WIDE_INT_PRINT_DEC" queries\n",
+ alias_stats.ref_maybe_used_by_call_p_no_alias,
+ alias_stats.refs_may_alias_p_no_alias
+ + alias_stats.ref_maybe_used_by_call_p_may_alias);
+ fprintf (s, " call_may_clobber_ref_p: "
+ HOST_WIDE_INT_PRINT_DEC" disambiguations, "
+ HOST_WIDE_INT_PRINT_DEC" queries\n",
+ alias_stats.call_may_clobber_ref_p_no_alias,
+ alias_stats.call_may_clobber_ref_p_no_alias
+ + alias_stats.call_may_clobber_ref_p_may_alias);
}
-/* Create memory tags for all the dereferenced pointers and build the
- ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
- sets. Based on the address escape and points-to information collected
- earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
- variables whose address is not needed anymore. */
+/* Return true, if dereferencing PTR may alias with a global variable. */
-static void
-setup_pointers_and_addressables (struct alias_info *ai)
+bool
+ptr_deref_may_alias_global_p (tree ptr)
{
- size_t n_vars, num_addressable_vars, num_pointers;
- referenced_var_iterator rvi;
- tree var;
- VEC (tree, heap) *varvec = NULL;
- safe_referenced_var_iterator srvi;
-
- /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
- num_addressable_vars = num_pointers = 0;
-
- FOR_EACH_REFERENCED_VAR (var, rvi)
- {
- if (may_be_aliased (var))
- num_addressable_vars++;
-
- if (POINTER_TYPE_P (TREE_TYPE (var)))
- {
- /* Since we don't keep track of volatile variables, assume that
- these pointers are used in indirect store operations. */
- if (TREE_THIS_VOLATILE (var))
- bitmap_set_bit (ai->dereferenced_ptrs_store, DECL_UID (var));
-
- num_pointers++;
- }
- }
-
- /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
- always going to be slightly bigger than we actually need them
- because some TREE_ADDRESSABLE variables will be marked
- non-addressable below and only pointers with unique symbol tags are
- going to be added to POINTERS. */
- ai->addressable_vars = XCNEWVEC (struct alias_map_d *, num_addressable_vars);
- ai->pointers = XCNEWVEC (struct alias_map_d *, num_pointers);
- ai->num_addressable_vars = 0;
- ai->num_pointers = 0;
-
- /* Since we will be creating symbol memory tags within this loop,
- cache the value of NUM_REFERENCED_VARS to avoid processing the
- additional tags unnecessarily. */
- n_vars = num_referenced_vars;
-
- FOR_EACH_REFERENCED_VAR_SAFE (var, varvec, srvi)
- {
- var_ann_t v_ann = var_ann (var);
- subvar_t svars;
-
- /* Name memory tags already have flow-sensitive aliasing
- information, so they need not be processed by
- compute_flow_insensitive_aliasing. Similarly, symbol memory
- tags are already accounted for when we process their
- associated pointer.
-
- Structure fields, on the other hand, have to have some of this
- information processed for them, but it's pointless to mark them
- non-addressable (since they are fake variables anyway). */
- if (MTAG_P (var) && TREE_CODE (var) != STRUCT_FIELD_TAG)
- continue;
-
- /* Remove the ADDRESSABLE flag from every addressable variable whose
- address is not needed anymore. This is caused by the propagation
- of ADDR_EXPR constants into INDIRECT_REF expressions and the
- removal of dead pointer assignments done by the early scalar
- cleanup passes. */
- if (TREE_ADDRESSABLE (var))
- {
- if (!bitmap_bit_p (addressable_vars, DECL_UID (var))
- && TREE_CODE (var) != RESULT_DECL
- && !is_global_var (var))
- {
- bool okay_to_mark = true;
-
- /* Since VAR is now a regular GIMPLE register, we will need
- to rename VAR into SSA afterwards. */
- mark_sym_for_renaming (var);
-
- /* If VAR can have sub-variables, and any of its
- sub-variables has its address taken, then we cannot
- remove the addressable flag from VAR. */
- if (var_can_have_subvars (var)
- && (svars = get_subvars_for_var (var)))
- {
- subvar_t sv;
-
- for (sv = svars; sv; sv = sv->next)
- {
- if (bitmap_bit_p (addressable_vars, DECL_UID (sv->var)))
- okay_to_mark = false;
- mark_sym_for_renaming (sv->var);
- }
- }
-
- /* The address of VAR is not needed, remove the
- addressable bit, so that it can be optimized as a
- regular variable. */
- if (okay_to_mark)
- mark_non_addressable (var);
- }
- }
-
- /* Global variables and addressable locals may be aliased. Create an
- entry in ADDRESSABLE_VARS for VAR. */
- if (may_be_aliased (var)
- && (!var_can_have_subvars (var)
- || get_subvars_for_var (var) == NULL))
- {
- create_alias_map_for (var, ai);
- mark_sym_for_renaming (var);
- }
-
- /* Add pointer variables that have been dereferenced to the POINTERS
- array and create a symbol memory tag for them. */
- if (POINTER_TYPE_P (TREE_TYPE (var)))
- {
- if ((bitmap_bit_p (ai->dereferenced_ptrs_store, DECL_UID (var))
- || bitmap_bit_p (ai->dereferenced_ptrs_load, DECL_UID (var))))
- {
- tree tag;
- var_ann_t t_ann;
-
- /* If pointer VAR still doesn't have a memory tag
- associated with it, create it now or re-use an
- existing one. */
- tag = get_tmt_for (var, ai);
- t_ann = var_ann (tag);
-
- /* The symbol tag will need to be renamed into SSA
- afterwards. Note that we cannot do this inside
- get_tmt_for because aliasing may run multiple times
- and we only create symbol tags the first time. */
- mark_sym_for_renaming (tag);
-
- /* Similarly, if pointer VAR used to have another type
- tag, we will need to process it in the renamer to
- remove the stale virtual operands. */
- if (v_ann->symbol_mem_tag)
- mark_sym_for_renaming (v_ann->symbol_mem_tag);
-
- /* Associate the tag with pointer VAR. */
- v_ann->symbol_mem_tag = tag;
-
- /* If pointer VAR has been used in a store operation,
- then its memory tag must be marked as written-to. */
- if (bitmap_bit_p (ai->dereferenced_ptrs_store, DECL_UID (var)))
- bitmap_set_bit (ai->written_vars, DECL_UID (tag));
-
- /* All the dereferences of pointer VAR count as
- references of TAG. Since TAG can be associated with
- several pointers, add the dereferences of VAR to the
- TAG. */
- NUM_REFERENCES_SET (t_ann,
- NUM_REFERENCES (t_ann)
- + NUM_REFERENCES (v_ann));
- }
- else
- {
- /* The pointer has not been dereferenced. If it had a
- symbol memory tag, remove it and mark the old tag for
- renaming to remove it out of the IL. */
- var_ann_t ann = var_ann (var);
- tree tag = ann->symbol_mem_tag;
- if (tag)
- {
- mark_sym_for_renaming (tag);
- ann->symbol_mem_tag = NULL_TREE;
- }
- }
- }
- }
- VEC_free (tree, heap, varvec);
-}
-
-
-/* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
- every call site, we need to emit V_MAY_DEF expressions to represent the
- clobbering effects of the call for variables whose address escapes the
- current function.
-
- One approach is to group all call-clobbered variables into a single
- representative that is used as an alias of every call-clobbered variable
- (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
- references to any call clobbered variable is a reference to .GLOBAL_VAR.
-
- The second approach is to emit a clobbering V_MAY_DEF for every
- call-clobbered variable at call sites. This is the preferred way in terms
- of optimization opportunities but it may create too many V_MAY_DEF operands
- if there are many call clobbered variables and function calls in the
- function.
-
- To decide whether or not to use .GLOBAL_VAR we multiply the number of
- function calls found by the number of call-clobbered variables. If that
- product is beyond a certain threshold, as determined by the parameterized
- values shown below, we use .GLOBAL_VAR.
-
- FIXME. This heuristic should be improved. One idea is to use several
- .GLOBAL_VARs of different types instead of a single one. The thresholds
- have been derived from a typical bootstrap cycle, including all target
- libraries. Compile times were found increase by ~1% compared to using
- .GLOBAL_VAR. */
+ struct ptr_info_def *pi;
-static void
-maybe_create_global_var (struct alias_info *ai)
-{
- unsigned i, n_clobbered;
- bitmap_iterator bi;
-
- /* No need to create it, if we have one already. */
- if (global_var == NULL_TREE)
- {
- /* Count all the call-clobbered variables. */
- n_clobbered = 0;
- EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
- {
- n_clobbered++;
- }
+ /* If we end up with a pointer constant here that may point
+ to global memory. */
+ if (TREE_CODE (ptr) != SSA_NAME)
+ return true;
- /* If the number of virtual operands that would be needed to
- model all the call-clobbered variables is larger than
- GLOBAL_VAR_THRESHOLD, create .GLOBAL_VAR.
-
- Also create .GLOBAL_VAR if there are no call-clobbered
- variables and the program contains a mixture of pure/const
- and regular function calls. This is to avoid the problem
- described in PR 20115:
-
- int X;
- int func_pure (void) { return X; }
- int func_non_pure (int a) { X += a; }
- int foo ()
- {
- int a = func_pure ();
- func_non_pure (a);
- a = func_pure ();
- return a;
- }
-
- Since foo() has no call-clobbered variables, there is
- no relationship between the calls to func_pure and
- func_non_pure. Since func_pure has no side-effects, value
- numbering optimizations elide the second call to func_pure.
- So, if we have some pure/const and some regular calls in the
- program we create .GLOBAL_VAR to avoid missing these
- relations. */
- if (ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD
- || (n_clobbered == 0
- && ai->num_calls_found > 0
- && ai->num_pure_const_calls_found > 0
- && ai->num_calls_found > ai->num_pure_const_calls_found))
- create_global_var ();
- }
+ pi = SSA_NAME_PTR_INFO (ptr);
- /* Mark all call-clobbered symbols for renaming. Since the initial
- rewrite into SSA ignored all call sites, we may need to rename
- .GLOBAL_VAR and the call-clobbered variables. */
- EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
- {
- tree var = referenced_var (i);
+ /* If we do not have points-to information for this variable,
+ we have to punt. */
+ if (!pi)
+ return true;
- /* If the function has calls to clobbering functions and
- .GLOBAL_VAR has been created, make it an alias for all
- call-clobbered variables. */
- if (global_var && var != global_var)
- {
- add_may_alias (var, global_var);
- gcc_assert (!get_subvars_for_var (var));
- }
-
- mark_sym_for_renaming (var);
- }
+ return pt_solution_includes_global (&pi->pt);
}
-
-/* Return TRUE if pointer PTR may point to variable VAR.
-
- MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
- This is needed because when checking for type conflicts we are
- interested in the alias set of the memory location pointed-to by
- PTR. The alias set of PTR itself is irrelevant.
-
- VAR_ALIAS_SET is the alias set for VAR. */
+/* Return true if dereferencing PTR may alias DECL. */
static bool
-may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
- tree var, HOST_WIDE_INT var_alias_set,
- bool alias_set_only)
+ptr_deref_may_alias_decl_p (tree ptr, tree decl)
{
- tree mem;
-
- alias_stats.alias_queries++;
- alias_stats.simple_queries++;
-
- /* By convention, a variable cannot alias itself. */
- mem = var_ann (ptr)->symbol_mem_tag;
- if (mem == var)
- {
- alias_stats.alias_noalias++;
- alias_stats.simple_resolved++;
- return false;
- }
-
- /* If -fargument-noalias-global is > 2, pointer arguments may
- not point to anything else. */
- if (flag_argument_noalias > 2 && TREE_CODE (ptr) == PARM_DECL)
- {
- alias_stats.alias_noalias++;
- alias_stats.simple_resolved++;
- return false;
- }
-
- /* If -fargument-noalias-global is > 1, pointer arguments may
- not point to global variables. */
- if (flag_argument_noalias > 1 && is_global_var (var)
- && TREE_CODE (ptr) == PARM_DECL)
- {
- alias_stats.alias_noalias++;
- alias_stats.simple_resolved++;
- return false;
- }
-
- /* If either MEM or VAR is a read-only global and the other one
- isn't, then PTR cannot point to VAR. */
- if ((unmodifiable_var_p (mem) && !unmodifiable_var_p (var))
- || (unmodifiable_var_p (var) && !unmodifiable_var_p (mem)))
- {
- alias_stats.alias_noalias++;
- alias_stats.simple_resolved++;
- return false;
- }
-
- gcc_assert (TREE_CODE (mem) == SYMBOL_MEMORY_TAG);
-
- alias_stats.tbaa_queries++;
-
- /* If the alias sets don't conflict then MEM cannot alias VAR. */
- if (!alias_sets_conflict_p (mem_alias_set, var_alias_set))
- {
- alias_stats.alias_noalias++;
- alias_stats.tbaa_resolved++;
- return false;
- }
-
- /* If var is a record or union type, ptr cannot point into var
- unless there is some operation explicit address operation in the
- program that can reference a field of the ptr's dereferenced
- type. This also assumes that the types of both var and ptr are
- contained within the compilation unit, and that there is no fancy
- addressing arithmetic associated with any of the types
- involved. */
+ struct ptr_info_def *pi;
- if ((mem_alias_set != 0) && (var_alias_set != 0))
- {
- tree ptr_type = TREE_TYPE (ptr);
- tree var_type = TREE_TYPE (var);
-
- /* The star count is -1 if the type at the end of the pointer_to
- chain is not a record or union type. */
- if ((!alias_set_only) &&
- ipa_type_escape_star_count_of_interesting_type (var_type) >= 0)
- {
- int ptr_star_count = 0;
-
- /* Ipa_type_escape_star_count_of_interesting_type is a little to
- restrictive for the pointer type, need to allow pointers to
- primitive types as long as those types cannot be pointers
- to everything. */
- while (POINTER_TYPE_P (ptr_type))
- /* Strip the *'s off. */
- {
- ptr_type = TREE_TYPE (ptr_type);
- ptr_star_count++;
- }
-
- /* There does not appear to be a better test to see if the
- pointer type was one of the pointer to everything
- types. */
-
- if (ptr_star_count > 0)
- {
- alias_stats.structnoaddress_queries++;
- if (ipa_type_escape_field_does_not_clobber_p (var_type,
- TREE_TYPE (ptr)))
- {
- alias_stats.structnoaddress_resolved++;
- alias_stats.alias_noalias++;
- return false;
- }
- }
- else if (ptr_star_count == 0)
- {
- /* If ptr_type was not really a pointer to type, it cannot
- alias. */
- alias_stats.structnoaddress_queries++;
- alias_stats.structnoaddress_resolved++;
- alias_stats.alias_noalias++;
- return false;
- }
- }
- }
+ /* ??? During SCCVN/PRE we can end up with *&x during valueizing
+ operands. Likewise we can end up with dereferencing constant
+ pointers. Just bail out in these cases for now. */
+ if (TREE_CODE (ptr) == ADDR_EXPR
+ || TREE_CODE (ptr) == INTEGER_CST)
+ return true;
- alias_stats.alias_mayalias++;
- return true;
-}
+ gcc_assert (TREE_CODE (ptr) == SSA_NAME
+ && (TREE_CODE (decl) == VAR_DECL
+ || TREE_CODE (decl) == PARM_DECL
+ || TREE_CODE (decl) == RESULT_DECL));
+ /* Non-aliased variables can not be pointed to. */
+ if (!may_be_aliased (decl))
+ return false;
-/* Add ALIAS to the set of variables that may alias VAR. */
+ /* If we do not have useful points-to information for this pointer
+ we cannot disambiguate anything else. */
+ pi = SSA_NAME_PTR_INFO (ptr);
+ if (!pi)
+ return true;
-static void
-add_may_alias (tree var, tree alias)
-{
- size_t i;
- var_ann_t v_ann = get_var_ann (var);
- var_ann_t a_ann = get_var_ann (alias);
- tree al;
-
- /* Don't allow self-referential aliases. */
- gcc_assert (var != alias);
-
- /* ALIAS must be addressable if it's being added to an alias set. */
-#if 1
- TREE_ADDRESSABLE (alias) = 1;
-#else
- gcc_assert (may_be_aliased (alias));
-#endif
-
- if (v_ann->may_aliases == NULL)
- v_ann->may_aliases = VEC_alloc (tree, gc, 2);
-
- /* Avoid adding duplicates. */
- for (i = 0; VEC_iterate (tree, v_ann->may_aliases, i, al); i++)
- if (alias == al)
- return;
-
- VEC_safe_push (tree, gc, v_ann->may_aliases, alias);
- a_ann->is_aliased = 1;
+ return pt_solution_includes (&pi->pt, decl);
}
+/* Return true if dereferenced PTR1 and PTR2 may alias. */
-/* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
-
-static void
-replace_may_alias (tree var, size_t i, tree new_alias)
+static bool
+ptr_derefs_may_alias_p (tree ptr1, tree ptr2)
{
- var_ann_t v_ann = var_ann (var);
- VEC_replace (tree, v_ann->may_aliases, i, new_alias);
-}
+ struct ptr_info_def *pi1, *pi2;
+ /* ??? During SCCVN/PRE we can end up with *&x during valueizing
+ operands. Likewise we can end up with dereferencing constant
+ pointers. Just bail out in these cases for now. */
+ if (TREE_CODE (ptr1) == ADDR_EXPR
+ || TREE_CODE (ptr1) == INTEGER_CST
+ || TREE_CODE (ptr2) == ADDR_EXPR
+ || TREE_CODE (ptr2) == INTEGER_CST)
+ return true;
-/* Mark pointer PTR as pointing to an arbitrary memory location. */
+ gcc_assert (TREE_CODE (ptr1) == SSA_NAME
+ && TREE_CODE (ptr2) == SSA_NAME);
-static void
-set_pt_anything (tree ptr)
-{
- struct ptr_info_def *pi = get_ptr_info (ptr);
+ /* We may end up with two empty points-to solutions for two same pointers.
+ In this case we still want to say both pointers alias, so shortcut
+ that here. */
+ if (ptr1 == ptr2)
+ return true;
- pi->pt_anything = 1;
- pi->pt_vars = NULL;
+ /* If we do not have useful points-to information for either pointer
+ we cannot disambiguate anything else. */
+ pi1 = SSA_NAME_PTR_INFO (ptr1);
+ pi2 = SSA_NAME_PTR_INFO (ptr2);
+ if (!pi1 || !pi2)
+ return true;
- /* The pointer used to have a name tag, but we now found it pointing
- to an arbitrary location. The name tag needs to be renamed and
- disassociated from PTR. */
- if (pi->name_mem_tag)
- {
- mark_sym_for_renaming (pi->name_mem_tag);
- pi->name_mem_tag = NULL_TREE;
- }
+ return pt_solutions_intersect (&pi1->pt, &pi2->pt);
}
-
/* Return true if STMT is an "escape" site from the current function. Escape
sites those statements which might expose the address of a variable
outside the current function. STMT is an escape site iff:
3- STMT is an assignment to a non-local variable, or
4- STMT is a return statement.
- AI points to the alias information collected so far.
-
Return the type of escape site found, if we found one, or NO_ESCAPE
if none. */
enum escape_type
-is_escape_site (tree stmt, struct alias_info *ai)
+is_escape_site (gimple stmt)
{
- tree call = get_call_expr_in (stmt);
- if (call != NULL_TREE)
+ if (is_gimple_call (stmt))
{
- ai->num_calls_found++;
-
- if (!TREE_SIDE_EFFECTS (call))
- {
- ai->num_pure_const_calls_found++;
- return ESCAPE_TO_PURE_CONST;
- }
+ if (gimple_call_flags (stmt) & (ECF_PURE | ECF_CONST))
+ return ESCAPE_TO_PURE_CONST;
return ESCAPE_TO_CALL;
}
- else if (TREE_CODE (stmt) == ASM_EXPR)
+ else if (gimple_code (stmt) == GIMPLE_ASM)
return ESCAPE_TO_ASM;
- else if (TREE_CODE (stmt) == MODIFY_EXPR)
+ else if (is_gimple_assign (stmt))
{
- tree lhs = TREE_OPERAND (stmt, 0);
+ tree lhs = gimple_assign_lhs (stmt);
/* Get to the base of _REF nodes. */
if (TREE_CODE (lhs) != SSA_NAME)
lhs = get_base_address (lhs);
- /* If we couldn't recognize the LHS of the assignment, assume that it
- is a non-local store. */
- if (lhs == NULL_TREE)
- return ESCAPE_UNKNOWN;
-
- if (TREE_CODE (TREE_OPERAND (stmt, 1)) == NOP_EXPR
- || TREE_CODE (TREE_OPERAND (stmt, 1)) == CONVERT_EXPR
- || TREE_CODE (TREE_OPERAND (stmt, 1)) == VIEW_CONVERT_EXPR)
- {
- tree from = TREE_TYPE (TREE_OPERAND (TREE_OPERAND (stmt, 1), 0));
- tree to = TREE_TYPE (TREE_OPERAND (stmt, 1));
-
- /* If the RHS is a conversion between a pointer and an integer, the
- pointer escapes since we can't track the integer. */
- if (POINTER_TYPE_P (from) && !POINTER_TYPE_P (to))
- return ESCAPE_BAD_CAST;
-
- /* Same if the RHS is a conversion between a regular pointer and a
- ref-all pointer since we can't track the SMT of the former. */
- if (POINTER_TYPE_P (from) && !TYPE_REF_CAN_ALIAS_ALL (from)
- && POINTER_TYPE_P (to) && TYPE_REF_CAN_ALIAS_ALL (to))
- return ESCAPE_BAD_CAST;
- }
-
- /* If the LHS is an SSA name, it can't possibly represent a non-local
- memory store. */
- if (TREE_CODE (lhs) == SSA_NAME)
- return NO_ESCAPE;
-
- /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
- local variables we cannot be sure if it will escape, because we
- don't have information about objects not in SSA form. Need to
- implement something along the lines of
-
- J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
- Midkiff, ``Escape analysis for java,'' in Proceedings of the
- Conference on Object-Oriented Programming Systems, Languages, and
- Applications (OOPSLA), pp. 1-19, 1999. */
- return ESCAPE_STORED_IN_GLOBAL;
- }
- else if (TREE_CODE (stmt) == RETURN_EXPR)
- return ESCAPE_TO_RETURN;
-
- return NO_ESCAPE;
-}
-
-/* Create a new memory tag of type TYPE.
- Does NOT push it into the current binding. */
-
-static tree
-create_tag_raw (enum tree_code code, tree type, const char *prefix)
-{
- tree tmp_var;
- tree new_type;
-
- /* Make the type of the variable writable. */
- new_type = build_type_variant (type, 0, 0);
- TYPE_ATTRIBUTES (new_type) = TYPE_ATTRIBUTES (type);
-
- tmp_var = build_decl (code, create_tmp_var_name (prefix),
- type);
- /* Make the variable writable. */
- TREE_READONLY (tmp_var) = 0;
-
- /* It doesn't start out global. */
- MTAG_GLOBAL (tmp_var) = 0;
- TREE_STATIC (tmp_var) = 0;
- TREE_USED (tmp_var) = 1;
-
- return tmp_var;
-}
-
-/* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
- is considered to represent all the pointers whose pointed-to types are
- in the same alias set class. Otherwise, the tag represents a single
- SSA_NAME pointer variable. */
-
-static tree
-create_memory_tag (tree type, bool is_type_tag)
-{
- var_ann_t ann;
- tree tag = create_tag_raw (is_type_tag ? SYMBOL_MEMORY_TAG : NAME_MEMORY_TAG,
- type, (is_type_tag) ? "SMT" : "NMT");
-
- /* By default, memory tags are local variables. Alias analysis will
- determine whether they should be considered globals. */
- DECL_CONTEXT (tag) = current_function_decl;
-
- /* Memory tags are by definition addressable. */
- TREE_ADDRESSABLE (tag) = 1;
-
- ann = get_var_ann (tag);
- ann->symbol_mem_tag = NULL_TREE;
-
- /* Add the tag to the symbol table. */
- add_referenced_var (tag);
-
- return tag;
-}
-
-
-/* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
- This is used if P_i has been found to point to a specific set of
- variables or to a non-aliased memory location like the address returned
- by malloc functions. */
-
-static tree
-get_nmt_for (tree ptr)
-{
- struct ptr_info_def *pi = get_ptr_info (ptr);
- tree tag = pi->name_mem_tag;
-
- if (tag == NULL_TREE)
- tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false);
- return tag;
-}
-
-
-/* Return the symbol memory tag associated to pointer PTR. A memory
- tag is an artificial variable that represents the memory location
- pointed-to by PTR. It is used to model the effects of pointer
- de-references on addressable variables.
-
- AI points to the data gathered during alias analysis. This
- function populates the array AI->POINTERS. */
-
-static tree
-get_tmt_for (tree ptr, struct alias_info *ai)
-{
- size_t i;
- tree tag;
- tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
- HOST_WIDE_INT tag_set = get_alias_set (tag_type);
-
- /* We use a unique memory tag for all the ref-all pointers. */
- if (PTR_IS_REF_ALL (ptr))
- {
- if (!ai->ref_all_symbol_mem_tag)
- ai->ref_all_symbol_mem_tag = create_memory_tag (void_type_node, true);
- return ai->ref_all_symbol_mem_tag;
- }
-
- /* To avoid creating unnecessary memory tags, only create one memory tag
- per alias set class. Note that it may be tempting to group
- memory tags based on conflicting alias sets instead of
- equivalence. That would be wrong because alias sets are not
- necessarily transitive (as demonstrated by the libstdc++ test
- 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
- such that conflicts (A, B) == true and conflicts (A, C) == true,
- it does not necessarily follow that conflicts (B, C) == true. */
- for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++)
- {
- struct alias_map_d *curr = ai->pointers[i];
- tree curr_tag = var_ann (curr->var)->symbol_mem_tag;
- if (tag_set == curr->set)
- {
- tag = curr_tag;
- break;
- }
- }
-
- /* If VAR cannot alias with any of the existing memory tags, create a new
- tag for PTR and add it to the POINTERS array. */
- if (tag == NULL_TREE)
- {
- struct alias_map_d *alias_map;
-
- /* If PTR did not have a symbol tag already, create a new SMT.*
- artificial variable representing the memory location
- pointed-to by PTR. */
- if (var_ann (ptr)->symbol_mem_tag == NULL_TREE)
- tag = create_memory_tag (tag_type, true);
- else
- tag = var_ann (ptr)->symbol_mem_tag;
-
- /* Add PTR to the POINTERS array. Note that we are not interested in
- PTR's alias set. Instead, we cache the alias set for the memory that
- PTR points to. */
- alias_map = XCNEW (struct alias_map_d);
- alias_map->var = ptr;
- alias_map->set = tag_set;
- ai->pointers[ai->num_pointers++] = alias_map;
- }
-
- /* If the pointed-to type is volatile, so is the tag. */
- TREE_THIS_VOLATILE (tag) |= TREE_THIS_VOLATILE (tag_type);
-
- /* Make sure that the symbol tag has the same alias set as the
- pointed-to type. */
- gcc_assert (tag_set == get_alias_set (tag));
+ /* If we couldn't recognize the LHS of the assignment, assume that it
+ is a non-local store. */
+ if (lhs == NULL_TREE)
+ return ESCAPE_UNKNOWN;
- return tag;
-}
+ if (gimple_assign_cast_p (stmt))
+ {
+ tree from = TREE_TYPE (gimple_assign_rhs1 (stmt));
+ tree to = TREE_TYPE (lhs);
+ /* If the RHS is a conversion between a pointer and an integer, the
+ pointer escapes since we can't track the integer. */
+ if (POINTER_TYPE_P (from) && !POINTER_TYPE_P (to))
+ return ESCAPE_BAD_CAST;
+ }
-/* Create GLOBAL_VAR, an artificial global variable to act as a
- representative of all the variables that may be clobbered by function
- calls. */
+ /* If the LHS is an SSA name, it can't possibly represent a non-local
+ memory store. */
+ if (TREE_CODE (lhs) == SSA_NAME)
+ return NO_ESCAPE;
-static void
-create_global_var (void)
-{
- global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"),
- void_type_node);
- DECL_ARTIFICIAL (global_var) = 1;
- TREE_READONLY (global_var) = 0;
- DECL_EXTERNAL (global_var) = 1;
- TREE_STATIC (global_var) = 1;
- TREE_USED (global_var) = 1;
- DECL_CONTEXT (global_var) = NULL_TREE;
- TREE_THIS_VOLATILE (global_var) = 0;
- TREE_ADDRESSABLE (global_var) = 0;
-
- create_var_ann (global_var);
- mark_call_clobbered (global_var, ESCAPE_UNKNOWN);
- add_referenced_var (global_var);
- mark_sym_for_renaming (global_var);
-}
+ /* If the LHS is a non-global decl, it isn't a non-local memory store.
+ If the LHS escapes, the RHS escape is dealt with in the PTA solver. */
+ if (DECL_P (lhs)
+ && !is_global_var (lhs))
+ return NO_ESCAPE;
+ /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
+ local variables we cannot be sure if it will escape, because we
+ don't have information about objects not in SSA form. Need to
+ implement something along the lines of
-/* Dump alias statistics on FILE. */
+ J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
+ Midkiff, ``Escape analysis for java,'' in Proceedings of the
+ Conference on Object-Oriented Programming Systems, Languages, and
+ Applications (OOPSLA), pp. 1-19, 1999. */
+ return ESCAPE_STORED_IN_GLOBAL;
+ }
+ else if (gimple_code (stmt) == GIMPLE_RETURN)
+ return ESCAPE_TO_RETURN;
-static void
-dump_alias_stats (FILE *file)
-{
- const char *funcname
- = lang_hooks.decl_printable_name (current_function_decl, 2);
- fprintf (file, "\nAlias statistics for %s\n\n", funcname);
- fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries);
- fprintf (file, "Total alias mayalias results:\t%u\n",
- alias_stats.alias_mayalias);
- fprintf (file, "Total alias noalias results:\t%u\n",
- alias_stats.alias_noalias);
- fprintf (file, "Total simple queries:\t%u\n",
- alias_stats.simple_queries);
- fprintf (file, "Total simple resolved:\t%u\n",
- alias_stats.simple_resolved);
- fprintf (file, "Total TBAA queries:\t%u\n",
- alias_stats.tbaa_queries);
- fprintf (file, "Total TBAA resolved:\t%u\n",
- alias_stats.tbaa_resolved);
- fprintf (file, "Total non-addressable structure type queries:\t%u\n",
- alias_stats.structnoaddress_queries);
- fprintf (file, "Total non-addressable structure type resolved:\t%u\n",
- alias_stats.structnoaddress_resolved);
+ return NO_ESCAPE;
}
-
+
/* Dump alias information on FILE. */
referenced_var_iterator rvi;
tree var;
- fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname);
+ fprintf (file, "\n\nAlias information for %s\n\n", funcname);
fprintf (file, "Aliased symbols\n\n");
dump_variable (file, var);
}
- fprintf (file, "\nDereferenced pointers\n\n");
-
- FOR_EACH_REFERENCED_VAR (var, rvi)
- {
- var_ann_t ann = var_ann (var);
- if (ann->symbol_mem_tag)
- dump_variable (file, var);
- }
-
- fprintf (file, "\nSymbol memory tags\n\n");
-
- FOR_EACH_REFERENCED_VAR (var, rvi)
- {
- if (TREE_CODE (var) == SYMBOL_MEMORY_TAG)
- dump_variable (file, var);
- }
-
- fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname);
+ fprintf (file, "\n\nFlow-insensitive points-to information for %s\n\n", funcname);
- fprintf (file, "SSA_NAME pointers\n\n");
for (i = 1; i < num_ssa_names; i++)
{
tree ptr = ssa_name (i);
struct ptr_info_def *pi;
- if (ptr == NULL_TREE)
+ if (ptr == NULL_TREE
+ || SSA_NAME_IN_FREE_LIST (ptr))
continue;
pi = SSA_NAME_PTR_INFO (ptr);
- if (!SSA_NAME_IN_FREE_LIST (ptr)
- && pi
- && pi->name_mem_tag)
+ if (pi)
dump_points_to_info_for (file, ptr);
}
- fprintf (file, "\nName memory tags\n\n");
-
- FOR_EACH_REFERENCED_VAR (var, rvi)
- {
- if (TREE_CODE (var) == NAME_MEMORY_TAG)
- dump_variable (file, var);
- }
-
fprintf (file, "\n");
}
pi = SSA_NAME_PTR_INFO (t);
if (pi == NULL)
{
- pi = GGC_NEW (struct ptr_info_def);
- memset ((void *)pi, 0, sizeof (*pi));
+ pi = GGC_CNEW (struct ptr_info_def);
+ pt_solution_reset (&pi->pt);
SSA_NAME_PTR_INFO (t) = pi;
}
return pi;
}
-
/* Dump points-to information for SSA_NAME PTR into FILE. */
void
if (pi)
{
- if (pi->name_mem_tag)
- {
- fprintf (file, ", name memory tag: ");
- print_generic_expr (file, pi->name_mem_tag, dump_flags);
- }
-
- if (pi->is_dereferenced)
- fprintf (file, ", is dereferenced");
+ if (pi->pt.anything)
+ fprintf (file, ", points-to anything");
- if (pi->value_escapes_p)
- fprintf (file, ", its value escapes");
+ if (pi->pt.nonlocal)
+ fprintf (file, ", points-to non-local");
- if (pi->pt_anything)
- fprintf (file, ", points-to anything");
+ if (pi->pt.escaped)
+ fprintf (file, ", points-to escaped");
- if (pi->pt_null)
+ if (pi->pt.null)
fprintf (file, ", points-to NULL");
- if (pi->pt_vars)
+ if (pi->pt.vars)
{
- unsigned ix;
- bitmap_iterator bi;
-
- fprintf (file, ", points-to vars: { ");
- EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix, bi)
- {
- print_generic_expr (file, referenced_var (ix), dump_flags);
- fprintf (file, " ");
- }
- fprintf (file, "}");
+ fprintf (file, ", points-to vars: ");
+ dump_decl_set (file, pi->pt.vars);
+ if (pi->pt.vars_contains_global)
+ fprintf (file, " (includes global vars)");
}
}
dump_points_to_info_for (stderr, var);
}
+/* Return 1 if TYPE1 and TYPE2 are to be considered equivalent for the
+ purpose of TBAA. Return 0 if they are distinct and -1 if we cannot
+ decide. */
-/* Dump points-to information into FILE. NOTE: This function is slow, as
- it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */
-
-void
-dump_points_to_info (FILE *file)
+static inline int
+same_type_for_tbaa (tree type1, tree type2)
{
- basic_block bb;
- block_stmt_iterator si;
- ssa_op_iter iter;
- const char *fname =
- lang_hooks.decl_printable_name (current_function_decl, 2);
- referenced_var_iterator rvi;
- tree var;
+ type1 = TYPE_MAIN_VARIANT (type1);
+ type2 = TYPE_MAIN_VARIANT (type2);
- fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname);
+ /* If we would have to do structural comparison bail out. */
+ if (TYPE_STRUCTURAL_EQUALITY_P (type1)
+ || TYPE_STRUCTURAL_EQUALITY_P (type2))
+ return -1;
- /* First dump points-to information for the default definitions of
- pointer variables. This is necessary because default definitions are
- not part of the code. */
- FOR_EACH_REFERENCED_VAR (var, rvi)
- {
- if (POINTER_TYPE_P (TREE_TYPE (var)))
- {
- tree def = default_def (var);
- if (def)
- dump_points_to_info_for (file, def);
- }
- }
+ /* Compare the canonical types. */
+ if (TYPE_CANONICAL (type1) == TYPE_CANONICAL (type2))
+ return 1;
- /* Dump points-to information for every pointer defined in the program. */
- FOR_EACH_BB (bb)
- {
- tree phi;
+ /* ??? Array types are not properly unified in all cases as we have
+ spurious changes in the index types for example. Removing this
+ causes all sorts of problems with the Fortran frontend. */
+ if (TREE_CODE (type1) == ARRAY_TYPE
+ && TREE_CODE (type2) == ARRAY_TYPE)
+ return -1;
- for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
- {
- tree ptr = PHI_RESULT (phi);
- if (POINTER_TYPE_P (TREE_TYPE (ptr)))
- dump_points_to_info_for (file, ptr);
- }
+ /* The types are known to be not equal. */
+ return 0;
+}
- for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
- {
- tree stmt = bsi_stmt (si);
- tree def;
- FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
- if (POINTER_TYPE_P (TREE_TYPE (def)))
- dump_points_to_info_for (file, def);
- }
- }
+/* Determine if the two component references REF1 and REF2 which are
+ based on access types TYPE1 and TYPE2 and of which at least one is based
+ on an indirect reference may alias. */
- fprintf (file, "\n");
+static bool
+nonaliasing_component_refs_p (tree ref1, tree type1,
+ HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
+ tree ref2, tree type2,
+ HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2)
+{
+ /* If one reference is a component references through pointers try to find a
+ common base and apply offset based disambiguation. This handles
+ for example
+ struct A { int i; int j; } *q;
+ struct B { struct A a; int k; } *p;
+ disambiguating q->i and p->a.j. */
+ tree *refp;
+ int same_p;
+
+ /* Now search for the type1 in the access path of ref2. This
+ would be a common base for doing offset based disambiguation on. */
+ /* Skip the outermost ref - we would have caught that earlier. */
+ refp = &TREE_OPERAND (ref2, 0);
+ while (handled_component_p (*refp)
+ && same_type_for_tbaa (TREE_TYPE (*refp), type1) == 0)
+ refp = &TREE_OPERAND (*refp, 0);
+ same_p = same_type_for_tbaa (TREE_TYPE (*refp), type1);
+ /* If we couldn't compare types we have to bail out. */
+ if (same_p == -1)
+ return true;
+ else if (same_p == 1)
+ {
+ HOST_WIDE_INT offadj, sztmp, msztmp;
+ get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp);
+ offset2 -= offadj;
+ return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
+ }
+ /* If we didn't find a common base, try the other way around. */
+ refp = &TREE_OPERAND (ref1, 0);
+ while (handled_component_p (*refp)
+ && same_type_for_tbaa (TREE_TYPE (*refp), type2) == 0)
+ refp = &TREE_OPERAND (*refp, 0);
+ same_p = same_type_for_tbaa (TREE_TYPE (*refp), type2);
+ /* If we couldn't compare types we have to bail out. */
+ if (same_p == -1)
+ return true;
+ else if (same_p == 1)
+ {
+ HOST_WIDE_INT offadj, sztmp, msztmp;
+ get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp);
+ offset1 -= offadj;
+ return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
+ }
+ /* If we have two type access paths B1.path1 and B2.path2 they may
+ only alias if either B1 is in B2.path2 or B2 is in B1.path1. */
+ return false;
}
+/* Return true if two memory references based on the variables BASE1
+ and BASE2 constrained to [OFFSET1, OFFSET1 + MAX_SIZE1[ and
+ [OFFSET2, OFFSET2 + MAX_SIZE2[ may alias. */
-/* Dump points-to info pointed to by PTO into STDERR. */
-
-void
-debug_points_to_info (void)
+static bool
+decl_refs_may_alias_p (tree base1,
+ HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
+ tree base2,
+ HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2)
{
- dump_points_to_info (stderr);
+ gcc_assert (SSA_VAR_P (base1) && SSA_VAR_P (base2));
+
+ /* If both references are based on different variables, they cannot alias. */
+ if (!operand_equal_p (base1, base2, 0))
+ return false;
+
+ /* If both references are based on the same variable, they cannot alias if
+ the accesses do not overlap. */
+ return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
}
-/* Dump to FILE the list of variables that may be aliasing VAR. */
+/* Return true if an indirect reference based on *PTR1 constrained
+ to [OFFSET1, OFFSET1 + MAX_SIZE1[ may alias a variable based on BASE2
+ constrained to [OFFSET2, OFFSET2 + MAX_SIZE2[. *PTR1 and BASE2 have
+ the alias sets BASE1_ALIAS_SET and BASE2_ALIAS_SET which can be -1
+ in which case they are computed on-demand. REF1 and REF2
+ if non-NULL are the complete memory reference trees. */
-void
-dump_may_aliases_for (FILE *file, tree var)
-{
- VEC(tree, gc) *aliases;
-
- if (TREE_CODE (var) == SSA_NAME)
- var = SSA_NAME_VAR (var);
+static bool
+indirect_ref_may_alias_decl_p (tree ref1, tree ptr1,
+ HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
+ alias_set_type base1_alias_set,
+ tree ref2, tree base2,
+ HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2,
+ alias_set_type base2_alias_set)
+{
+ /* If only one reference is based on a variable, they cannot alias if
+ the pointer access is beyond the extent of the variable access.
+ (the pointer base cannot validly point to an offset less than zero
+ of the variable).
+ They also cannot alias if the pointer may not point to the decl. */
+ if (max_size2 != -1
+ && !ranges_overlap_p (offset1, max_size1, 0, offset2 + max_size2))
+ return false;
+ if (!ptr_deref_may_alias_decl_p (ptr1, base2))
+ return false;
- aliases = var_ann (var)->may_aliases;
- if (aliases)
- {
- size_t i;
- tree al;
- fprintf (file, "{ ");
- for (i = 0; VEC_iterate (tree, aliases, i, al); i++)
- {
- print_generic_expr (file, al, dump_flags);
- fprintf (file, " ");
- }
- fprintf (file, "}");
- }
-}
+ /* Disambiguations that rely on strict aliasing rules follow. */
+ if (!flag_strict_aliasing)
+ return true;
+ /* If the alias set for a pointer access is zero all bets are off. */
+ if (base1_alias_set == -1)
+ base1_alias_set = get_deref_alias_set (ptr1);
+ if (base1_alias_set == 0)
+ return true;
+ if (base2_alias_set == -1)
+ base2_alias_set = get_alias_set (base2);
+
+ /* If both references are through the same type, they do not alias
+ if the accesses do not overlap. This does extra disambiguation
+ for mixed/pointer accesses but requires strict aliasing. */
+ if (same_type_for_tbaa (TREE_TYPE (TREE_TYPE (ptr1)),
+ TREE_TYPE (base2)) == 1)
+ return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
+
+ /* The only way to access a variable is through a pointer dereference
+ of the same alias set or a subset of it. */
+ if (base1_alias_set != base2_alias_set
+ && !alias_set_subset_of (base1_alias_set, base2_alias_set))
+ return false;
-/* Dump to stderr the list of variables that may be aliasing VAR. */
+ /* Do access-path based disambiguation. */
+ if (ref1 && ref2
+ && handled_component_p (ref1)
+ && handled_component_p (ref2))
+ return nonaliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)),
+ offset1, max_size1,
+ ref2, TREE_TYPE (base2),
+ offset2, max_size2);
-void
-debug_may_aliases_for (tree var)
-{
- dump_may_aliases_for (stderr, var);
+ return true;
}
-/* Return true if VAR may be aliased. */
+/* Return true if two indirect references based on *PTR1
+ and *PTR2 constrained to [OFFSET1, OFFSET1 + MAX_SIZE1[ and
+ [OFFSET2, OFFSET2 + MAX_SIZE2[ may alias. *PTR1 and *PTR2 have
+ the alias sets BASE1_ALIAS_SET and BASE2_ALIAS_SET which can be -1
+ in which case they are computed on-demand. REF1 and REF2
+ if non-NULL are the complete memory reference trees. */
-bool
-may_be_aliased (tree var)
-{
- /* Obviously. */
- if (TREE_ADDRESSABLE (var))
- return true;
+static bool
+indirect_refs_may_alias_p (tree ref1, tree ptr1,
+ HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
+ alias_set_type base1_alias_set,
+ tree ref2, tree ptr2,
+ HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2,
+ alias_set_type base2_alias_set)
+{
+ /* If both bases are based on pointers they cannot alias if they may not
+ point to the same memory object or if they point to the same object
+ and the accesses do not overlap. */
+ if (operand_equal_p (ptr1, ptr2, 0))
+ return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
+ if (!ptr_derefs_may_alias_p (ptr1, ptr2))
+ return false;
- /* Globally visible variables can have their addresses taken by other
- translation units. */
+ /* Disambiguations that rely on strict aliasing rules follow. */
+ if (!flag_strict_aliasing)
+ return true;
- if (MTAG_P (var)
- && (MTAG_GLOBAL (var) || TREE_PUBLIC (var)))
+ /* If the alias set for a pointer access is zero all bets are off. */
+ if (base1_alias_set == -1)
+ base1_alias_set = get_deref_alias_set (ptr1);
+ if (base1_alias_set == 0)
return true;
- else if (!MTAG_P (var)
- && (DECL_EXTERNAL (var) || TREE_PUBLIC (var)))
+ if (base2_alias_set == -1)
+ base2_alias_set = get_deref_alias_set (ptr2);
+ if (base2_alias_set == 0)
return true;
- /* Automatic variables can't have their addresses escape any other way.
- This must be after the check for global variables, as extern declarations
- do not have TREE_STATIC set. */
- if (!TREE_STATIC (var))
- return false;
+ /* If both references are through the same type, they do not alias
+ if the accesses do not overlap. This does extra disambiguation
+ for mixed/pointer accesses but requires strict aliasing. */
+ if (same_type_for_tbaa (TREE_TYPE (TREE_TYPE (ptr1)),
+ TREE_TYPE (TREE_TYPE (ptr2))) == 1)
+ return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
- /* If we're in unit-at-a-time mode, then we must have seen all occurrences
- of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise
- we can only be sure the variable isn't addressable if it's local to the
- current function. */
- if (flag_unit_at_a_time)
- return false;
- if (decl_function_context (var) == current_function_decl)
+ /* Do type-based disambiguation. */
+ if (base1_alias_set != base2_alias_set
+ && !alias_sets_conflict_p (base1_alias_set, base2_alias_set))
return false;
+ /* Do access-path based disambiguation. */
+ if (ref1 && ref2
+ && handled_component_p (ref1)
+ && handled_component_p (ref2))
+ return nonaliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)),
+ offset1, max_size1,
+ ref2, TREE_TYPE (TREE_TYPE (ptr2)),
+ offset2, max_size2);
+
return true;
}
+/* Return true, if the two memory references REF1 and REF2 may alias. */
+
+static bool
+refs_may_alias_p_1 (tree ref1, tree ref2)
+{
+ tree base1, base2;
+ HOST_WIDE_INT offset1 = 0, offset2 = 0;
+ HOST_WIDE_INT size1 = -1, size2 = -1;
+ HOST_WIDE_INT max_size1 = -1, max_size2 = -1;
+ bool var1_p, var2_p, ind1_p, ind2_p;
+
+ gcc_assert ((SSA_VAR_P (ref1)
+ || handled_component_p (ref1)
+ || INDIRECT_REF_P (ref1)
+ || TREE_CODE (ref1) == TARGET_MEM_REF)
+ && (SSA_VAR_P (ref2)
+ || handled_component_p (ref2)
+ || INDIRECT_REF_P (ref2)
+ || TREE_CODE (ref2) == TARGET_MEM_REF));
+
+ /* Decompose the references into their base objects and the access. */
+ base1 = get_ref_base_and_extent (ref1, &offset1, &size1, &max_size1);
+ base2 = get_ref_base_and_extent (ref2, &offset2, &size2, &max_size2);
+
+ /* We can end up with registers or constants as bases for example from
+ *D.1663_44 = VIEW_CONVERT_EXPR<struct DB_LSN>(__tmp$B0F64_59);
+ which is seen as a struct copy. */
+ if (TREE_CODE (base1) == SSA_NAME
+ || TREE_CODE (base2) == SSA_NAME
+ || is_gimple_min_invariant (base1)
+ || is_gimple_min_invariant (base2))
+ return false;
+
+ /* Defer to simple offset based disambiguation if we have
+ references based on two decls. Do this before defering to
+ TBAA to handle must-alias cases in conformance with the
+ GCC extension of allowing type-punning through unions. */
+ var1_p = SSA_VAR_P (base1);
+ var2_p = SSA_VAR_P (base2);
+ if (var1_p && var2_p)
+ return decl_refs_may_alias_p (base1, offset1, max_size1,
+ base2, offset2, max_size2);
+
+ /* First defer to TBAA if possible. */
+ if (flag_strict_aliasing
+ && !alias_sets_conflict_p (get_alias_set (ref1), get_alias_set (ref2)))
+ return false;
+
+ /* If one reference is a TARGET_MEM_REF weird things are allowed. Still
+ TBAA disambiguation based on the access type is possible, so bail
+ out only after that check. */
+ if (TREE_CODE (ref1) == TARGET_MEM_REF
+ || TREE_CODE (ref2) == TARGET_MEM_REF)
+ return true;
+
+ /* Dispatch to the pointer-vs-decl or pointer-vs-pointer disambiguators. */
+ ind1_p = INDIRECT_REF_P (base1);
+ ind2_p = INDIRECT_REF_P (base2);
+ if (var1_p && ind2_p)
+ return indirect_ref_may_alias_decl_p (ref2, TREE_OPERAND (base2, 0),
+ offset2, max_size2, -1,
+ ref1, base1,
+ offset1, max_size1, -1);
+ else if (ind1_p && var2_p)
+ return indirect_ref_may_alias_decl_p (ref1, TREE_OPERAND (base1, 0),
+ offset1, max_size1, -1,
+ ref2, base2,
+ offset2, max_size2, -1);
+ else if (ind1_p && ind2_p)
+ return indirect_refs_may_alias_p (ref1, TREE_OPERAND (base1, 0),
+ offset1, max_size1, -1,
+ ref2, TREE_OPERAND (base2, 0),
+ offset2, max_size2, -1);
+
+ gcc_unreachable ();
+}
-/* Given two symbols return TRUE if one is in the alias set of the other. */
bool
-is_aliased_with (tree tag, tree sym)
+refs_may_alias_p (tree ref1, tree ref2)
{
- size_t i;
- VEC(tree,gc) *aliases;
- tree al;
+ bool res = refs_may_alias_p_1 (ref1, ref2);
+ if (res)
+ ++alias_stats.refs_may_alias_p_may_alias;
+ else
+ ++alias_stats.refs_may_alias_p_no_alias;
+ return res;
+}
- if (var_ann (sym)->is_aliased)
- {
- aliases = var_ann (tag)->may_aliases;
- if (aliases == NULL)
- return false;
+/* If the call CALL may use the memory reference REF return true,
+ otherwise return false. */
+
+static bool
+ref_maybe_used_by_call_p_1 (gimple call, tree ref)
+{
+ tree base;
+ unsigned i;
+ int flags = gimple_call_flags (call);
+
+ /* Const functions without a static chain do not implicitly use memory. */
+ if (!gimple_call_chain (call)
+ && (flags & (ECF_CONST|ECF_NOVOPS)))
+ goto process_args;
+
+ /* If the reference is not based on a decl give up.
+ ??? Handle indirect references by intersecting the call-used
+ solution with that of the pointer. */
+ base = get_base_address (ref);
+ if (!base
+ || !DECL_P (base))
+ return true;
- for (i = 0; VEC_iterate (tree, aliases, i, al); i++)
- if (al == sym)
- return true;
+ /* If the reference is based on a decl that is not aliased the call
+ cannot possibly use it. */
+ if (DECL_P (base)
+ && !may_be_aliased (base)
+ /* But local statics can be used through recursion. */
+ && !is_global_var (base))
+ goto process_args;
+
+ /* Check if base is a global static variable that is not read
+ by the function. */
+ if (TREE_CODE (base) == VAR_DECL
+ && TREE_STATIC (base)
+ && !TREE_PUBLIC (base))
+ {
+ tree callee = gimple_call_fndecl (call);
+ bitmap not_read;
+
+ if (callee != NULL_TREE
+ && (not_read
+ = ipa_reference_get_not_read_global (cgraph_node (callee)))
+ && bitmap_bit_p (not_read, DECL_UID (base)))
+ goto process_args;
+ }
+
+ /* If the base variable is call-used or call-clobbered then
+ it may be used. */
+ if (flags & (ECF_PURE|ECF_CONST|ECF_LOOPING_CONST_OR_PURE|ECF_NOVOPS))
+ {
+ if (is_call_used (base))
+ return true;
}
else
{
- aliases = var_ann (sym)->may_aliases;
+ if (is_call_clobbered (base))
+ return true;
+ }
- if (aliases == NULL)
- return false;
+ /* Inspect call arguments for passed-by-value aliases. */
+process_args:
+ for (i = 0; i < gimple_call_num_args (call); ++i)
+ {
+ tree op = gimple_call_arg (call, i);
+
+ if (TREE_CODE (op) == EXC_PTR_EXPR
+ || TREE_CODE (op) == FILTER_EXPR)
+ continue;
+
+ if (TREE_CODE (op) == WITH_SIZE_EXPR)
+ op = TREE_OPERAND (op, 0);
- for (i = 0; VEC_iterate (tree, aliases, i, al); i++)
- if (al == tag)
- return true;
+ if (TREE_CODE (op) != SSA_NAME
+ && !is_gimple_min_invariant (op)
+ && refs_may_alias_p (op, ref))
+ return true;
}
return false;
}
+static bool
+ref_maybe_used_by_call_p (gimple call, tree ref)
+{
+ bool res = ref_maybe_used_by_call_p_1 (call, ref);
+ if (res)
+ ++alias_stats.ref_maybe_used_by_call_p_may_alias;
+ else
+ ++alias_stats.ref_maybe_used_by_call_p_no_alias;
+ return res;
+}
-/* Create a new symbol tag for PTR. Construct the may-alias list of this type
- tag so that it has the aliasing of VAR.
- Note, the set of aliases represented by the new symbol tag are not marked
- for renaming. */
+/* If the statement STMT may use the memory reference REF return
+ true, otherwise return false. */
-void
-new_type_alias (tree ptr, tree var)
+bool
+ref_maybe_used_by_stmt_p (gimple stmt, tree ref)
{
- var_ann_t p_ann = var_ann (ptr);
- tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
- var_ann_t v_ann = var_ann (var);
- tree tag;
- subvar_t svars;
-
- gcc_assert (p_ann->symbol_mem_tag == NULL_TREE);
- gcc_assert (!MTAG_P (var));
-
- /* Add VAR to the may-alias set of PTR's new symbol tag. If VAR has
- subvars, add the subvars to the tag instead of the actual var. */
- if (var_can_have_subvars (var)
- && (svars = get_subvars_for_var (var)))
+ if (is_gimple_assign (stmt))
{
- subvar_t sv;
+ tree rhs;
- tag = create_memory_tag (tag_type, true);
- p_ann->symbol_mem_tag = tag;
+ /* All memory assign statements are single. */
+ if (!gimple_assign_single_p (stmt))
+ return false;
+
+ rhs = gimple_assign_rhs1 (stmt);
+ if (is_gimple_reg (rhs)
+ || is_gimple_min_invariant (rhs)
+ || gimple_assign_rhs_code (stmt) == CONSTRUCTOR)
+ return false;
- for (sv = svars; sv; sv = sv->next)
- add_may_alias (tag, sv->var);
+ return refs_may_alias_p (rhs, ref);
}
- else
- {
- /* The following is based on code in add_stmt_operand to ensure that the
- same defs/uses/vdefs/vuses will be found after replacing a reference
- to var (or ARRAY_REF to var) with an INDIRECT_REF to ptr whose value
- is the address of var. */
- VEC(tree, gc) *aliases = v_ann->may_aliases;
-
- if ((aliases != NULL)
- && (VEC_length (tree, aliases) == 1))
- {
- tree ali = VEC_index (tree, aliases, 0);
+ else if (is_gimple_call (stmt))
+ return ref_maybe_used_by_call_p (stmt, ref);
- if (TREE_CODE (ali) == SYMBOL_MEMORY_TAG)
- {
- p_ann->symbol_mem_tag = ali;
- return;
- }
- }
+ return true;
+}
- tag = create_memory_tag (tag_type, true);
- p_ann->symbol_mem_tag = tag;
+/* If the call in statement CALL may clobber the memory reference REF
+ return true, otherwise return false. */
- if (aliases == NULL)
- add_may_alias (tag, var);
- else
- {
- unsigned i;
- tree al;
+static bool
+call_may_clobber_ref_p_1 (gimple call, tree ref)
+{
+ tree base;
- for (i = 0; VEC_iterate (tree, aliases, i, al); i++)
- add_may_alias (tag, al);
- }
- }
+ /* If the call is pure or const it cannot clobber anything. */
+ if (gimple_call_flags (call)
+ & (ECF_PURE|ECF_CONST|ECF_LOOPING_CONST_OR_PURE|ECF_NOVOPS))
+ return false;
- TREE_READONLY (tag) = TREE_READONLY (var);
- MTAG_GLOBAL (tag) = is_global_var (var);
-}
+ base = get_base_address (ref);
+ if (!base)
+ return true;
+ if (TREE_CODE (base) == SSA_NAME
+ || CONSTANT_CLASS_P (base))
+ return false;
+ /* If the reference is based on a decl that is not aliased the call
+ cannot possibly clobber it. */
+ if (DECL_P (base)
+ && !may_be_aliased (base)
+ /* But local non-readonly statics can be modified through recursion
+ or the call may implement a threading barrier which we must
+ treat as may-def. */
+ && (TREE_READONLY (base)
+ || !is_global_var (base)))
+ return false;
-/* This represents the used range of a variable. */
+ /* Check if base is a global static variable that is not written
+ by the function. */
+ if (TREE_CODE (base) == VAR_DECL
+ && TREE_STATIC (base)
+ && !TREE_PUBLIC (base))
+ {
+ tree callee = gimple_call_fndecl (call);
+ bitmap not_written;
-typedef struct used_part
-{
- HOST_WIDE_INT minused;
- HOST_WIDE_INT maxused;
- /* True if we have an explicit use/def of some portion of this variable,
- even if it is all of it. i.e. a.b = 5 or temp = a.b. */
- bool explicit_uses;
- /* True if we have an implicit use/def of some portion of this
- variable. Implicit uses occur when we can't tell what part we
- are referencing, and have to make conservative assumptions. */
- bool implicit_uses;
- /* True if the structure is only written to or taken its address. */
- bool write_only;
-} *used_part_t;
-
-/* An array of used_part structures, indexed by variable uid. */
-
-static htab_t used_portions;
-
-struct used_part_map
-{
- unsigned int uid;
- used_part_t to;
-};
+ if (callee != NULL_TREE
+ && (not_written
+ = ipa_reference_get_not_written_global (cgraph_node (callee)))
+ && bitmap_bit_p (not_written, DECL_UID (base)))
+ return false;
+ }
-/* Return true if the uid in the two used part maps are equal. */
+ if (DECL_P (base))
+ return is_call_clobbered (base);
-static int
-used_part_map_eq (const void *va, const void *vb)
-{
- const struct used_part_map *a = (const struct used_part_map *) va;
- const struct used_part_map *b = (const struct used_part_map *) vb;
- return (a->uid == b->uid);
+ return true;
}
-/* Hash a from uid in a used_part_map. */
-
-static unsigned int
-used_part_map_hash (const void *item)
+static bool
+call_may_clobber_ref_p (gimple call, tree ref)
{
- return ((const struct used_part_map *)item)->uid;
+ bool res = call_may_clobber_ref_p_1 (call, ref);
+ if (res)
+ ++alias_stats.call_may_clobber_ref_p_may_alias;
+ else
+ ++alias_stats.call_may_clobber_ref_p_no_alias;
+ return res;
}
-/* Free a used part map element. */
-
-static void
-free_used_part_map (void *item)
-{
- free (((struct used_part_map *)item)->to);
- free (item);
-}
-/* Lookup a used_part structure for a UID. */
+/* If the statement STMT may clobber the memory reference REF return true,
+ otherwise return false. */
-static used_part_t
-up_lookup (unsigned int uid)
+bool
+stmt_may_clobber_ref_p (gimple stmt, tree ref)
{
- struct used_part_map *h, in;
- in.uid = uid;
- h = (struct used_part_map *) htab_find_with_hash (used_portions, &in, uid);
- if (!h)
- return NULL;
- return h->to;
-}
+ if (is_gimple_call (stmt))
+ {
+ tree lhs = gimple_call_lhs (stmt);
+ if (lhs
+ && !is_gimple_reg (lhs)
+ && refs_may_alias_p (ref, lhs))
+ return true;
+
+ return call_may_clobber_ref_p (stmt, ref);
+ }
+ else if (is_gimple_assign (stmt))
+ return refs_may_alias_p (ref, gimple_assign_lhs (stmt));
+ else if (gimple_code (stmt) == GIMPLE_ASM)
+ return true;
-/* Insert the pair UID, TO into the used part hashtable. */
-
-static void
-up_insert (unsigned int uid, used_part_t to)
-{
- struct used_part_map *h;
- void **loc;
-
- h = XNEW (struct used_part_map);
- h->uid = uid;
- h->to = to;
- loc = htab_find_slot_with_hash (used_portions, h,
- uid, INSERT);
- if (*loc != NULL)
- free (*loc);
- *(struct used_part_map **) loc = h;
+ return false;
}
+static tree get_continuation_for_phi (gimple, tree, bitmap *);
-/* Given a variable uid, UID, get or create the entry in the used portions
- table for the variable. */
+/* Walk the virtual use-def chain of VUSE until hitting the virtual operand
+ TARGET or a statement clobbering the memory reference REF in which
+ case false is returned. The walk starts with VUSE, one argument of PHI. */
-static used_part_t
-get_or_create_used_part_for (size_t uid)
+static bool
+maybe_skip_until (gimple phi, tree target, tree ref, tree vuse, bitmap *visited)
{
- used_part_t up;
- if ((up = up_lookup (uid)) == NULL)
+ if (!*visited)
+ *visited = BITMAP_ALLOC (NULL);
+
+ bitmap_set_bit (*visited, SSA_NAME_VERSION (PHI_RESULT (phi)));
+
+ /* Walk until we hit the target. */
+ while (vuse != target)
{
- up = XCNEW (struct used_part);
- up->minused = INT_MAX;
- up->maxused = 0;
- up->explicit_uses = false;
- up->implicit_uses = false;
- up->write_only = true;
+ gimple def_stmt = SSA_NAME_DEF_STMT (vuse);
+ /* Recurse for PHI nodes. */
+ if (gimple_code (def_stmt) == GIMPLE_PHI)
+ {
+ /* An already visited PHI node ends the walk successfully. */
+ if (bitmap_bit_p (*visited, SSA_NAME_VERSION (PHI_RESULT (def_stmt))))
+ return true;
+ vuse = get_continuation_for_phi (def_stmt, ref, visited);
+ if (!vuse)
+ return false;
+ continue;
+ }
+ /* A clobbering statement or the end of the IL ends it failing. */
+ else if (gimple_nop_p (def_stmt)
+ || stmt_may_clobber_ref_p (def_stmt, ref))
+ return false;
+ vuse = gimple_vuse (def_stmt);
}
-
- return up;
+ return true;
}
-
-/* Create and return a structure sub-variable for field type FIELD at
- offset OFFSET, with size SIZE, of variable VAR. */
+/* Starting from a PHI node for the virtual operand of the memory reference
+ REF find a continuation virtual operand that allows to continue walking
+ statements dominating PHI skipping only statements that cannot possibly
+ clobber REF. Returns NULL_TREE if no suitable virtual operand can
+ be found. */
static tree
-create_sft (tree var, tree field, unsigned HOST_WIDE_INT offset,
- unsigned HOST_WIDE_INT size)
+get_continuation_for_phi (gimple phi, tree ref, bitmap *visited)
{
- var_ann_t ann;
- tree subvar = create_tag_raw (STRUCT_FIELD_TAG, field, "SFT");
-
- /* We need to copy the various flags from VAR to SUBVAR, so that
- they are is_global_var iff the original variable was. */
- DECL_CONTEXT (subvar) = DECL_CONTEXT (var);
- MTAG_GLOBAL (subvar) = DECL_EXTERNAL (var);
- TREE_PUBLIC (subvar) = TREE_PUBLIC (var);
- TREE_STATIC (subvar) = TREE_STATIC (var);
- TREE_READONLY (subvar) = TREE_READONLY (var);
- TREE_ADDRESSABLE (subvar) = TREE_ADDRESSABLE (var);
-
- /* Add the new variable to REFERENCED_VARS. */
- ann = get_var_ann (subvar);
- ann->symbol_mem_tag = NULL;
- add_referenced_var (subvar);
- SFT_PARENT_VAR (subvar) = var;
- SFT_OFFSET (subvar) = offset;
- SFT_SIZE (subvar) = size;
- return subvar;
+ unsigned nargs = gimple_phi_num_args (phi);
+
+ /* Through a single-argument PHI we can simply look through. */
+ if (nargs == 1)
+ return PHI_ARG_DEF (phi, 0);
+
+ /* For two arguments try to skip non-aliasing code until we hit
+ the phi argument definition that dominates the other one. */
+ if (nargs == 2)
+ {
+ tree arg0 = PHI_ARG_DEF (phi, 0);
+ tree arg1 = PHI_ARG_DEF (phi, 1);
+ gimple def0 = SSA_NAME_DEF_STMT (arg0);
+ gimple def1 = SSA_NAME_DEF_STMT (arg1);
+
+ if (arg0 == arg1)
+ return arg0;
+ else if (gimple_nop_p (def0)
+ || (!gimple_nop_p (def1)
+ && dominated_by_p (CDI_DOMINATORS,
+ gimple_bb (def1), gimple_bb (def0))))
+ {
+ if (maybe_skip_until (phi, arg0, ref, arg1, visited))
+ return arg0;
+ }
+ else if (gimple_nop_p (def1)
+ || dominated_by_p (CDI_DOMINATORS,
+ gimple_bb (def0), gimple_bb (def1)))
+ {
+ if (maybe_skip_until (phi, arg1, ref, arg0, visited))
+ return arg1;
+ }
+ }
+
+ return NULL_TREE;
}
+/* Based on the memory reference REF and its virtual use VUSE call
+ WALKER for each virtual use that is equivalent to VUSE, including VUSE
+ itself. That is, for each virtual use for which its defining statement
+ does not clobber REF.
+
+ WALKER is called with REF, the current virtual use and DATA. If
+ WALKER returns non-NULL the walk stops and its result is returned.
+ At the end of a non-successful walk NULL is returned.
-/* Given an aggregate VAR, create the subvariables that represent its
- fields. */
+ TODO: Cache the vector of equivalent vuses per ref, vuse pair. */
-static void
-create_overlap_variables_for (tree var)
+void *
+walk_non_aliased_vuses (tree ref, tree vuse,
+ void *(*walker)(tree, tree, void *), void *data)
{
- VEC(fieldoff_s,heap) *fieldstack = NULL;
- used_part_t up;
- size_t uid = DECL_UID (var);
+ bitmap visited = NULL;
+ void *res;
- up = up_lookup (uid);
- if (!up
- || up->write_only)
- return;
+ timevar_push (TV_ALIAS_STMT_WALK);
- push_fields_onto_fieldstack (TREE_TYPE (var), &fieldstack, 0, NULL);
- if (VEC_length (fieldoff_s, fieldstack) != 0)
+ do
{
- subvar_t *subvars;
- fieldoff_s *fo;
- bool notokay = false;
- int fieldcount = 0;
- int i;
- HOST_WIDE_INT lastfooffset = -1;
- HOST_WIDE_INT lastfosize = -1;
- tree lastfotype = NULL_TREE;
-
- /* Not all fields have DECL_SIZE set, and those that don't, we don't
- know their size, and thus, can't handle.
- The same is true of fields with DECL_SIZE that is not an integer
- constant (such as variable sized fields).
- Fields with offsets which are not constant will have an offset < 0
- We *could* handle fields that are constant sized arrays, but
- currently don't. Doing so would require some extra changes to
- tree-ssa-operands.c. */
-
- for (i = 0; VEC_iterate (fieldoff_s, fieldstack, i, fo); i++)
- {
- if (!fo->size
- || TREE_CODE (fo->size) != INTEGER_CST
- || fo->offset < 0)
- {
- notokay = true;
- break;
- }
- fieldcount++;
- }
+ gimple def_stmt;
- /* The current heuristic we use is as follows:
- If the variable has no used portions in this function, no
- structure vars are created for it.
- Otherwise,
- If the variable has less than SALIAS_MAX_IMPLICIT_FIELDS,
- we always create structure vars for them.
- If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
- some explicit uses, we create structure vars for them.
- If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
- no explicit uses, we do not create structure vars for them.
- */
-
- if (fieldcount >= SALIAS_MAX_IMPLICIT_FIELDS
- && !up->explicit_uses)
- {
- if (dump_file && (dump_flags & TDF_DETAILS))
- {
- fprintf (dump_file, "Variable ");
- print_generic_expr (dump_file, var, 0);
- fprintf (dump_file, " has no explicit uses in this function, and is > SALIAS_MAX_IMPLICIT_FIELDS, so skipping\n");
- }
- notokay = true;
- }
-
- /* Bail out, if we can't create overlap variables. */
- if (notokay)
- {
- VEC_free (fieldoff_s, heap, fieldstack);
- return;
- }
-
- /* Otherwise, create the variables. */
- subvars = lookup_subvars_for_var (var);
-
- sort_fieldstack (fieldstack);
+ /* ??? Do we want to account this to TV_ALIAS_STMT_WALK? */
+ res = (*walker) (ref, vuse, data);
+ if (res)
+ break;
- for (i = VEC_length (fieldoff_s, fieldstack);
- VEC_iterate (fieldoff_s, fieldstack, --i, fo);)
+ def_stmt = SSA_NAME_DEF_STMT (vuse);
+ if (gimple_nop_p (def_stmt))
+ break;
+ else if (gimple_code (def_stmt) == GIMPLE_PHI)
+ vuse = get_continuation_for_phi (def_stmt, ref, &visited);
+ else
{
- subvar_t sv;
- HOST_WIDE_INT fosize;
- tree currfotype;
-
- fosize = TREE_INT_CST_LOW (fo->size);
- currfotype = fo->type;
-
- /* If this field isn't in the used portion,
- or it has the exact same offset and size as the last
- field, skip it. */
-
- if (((fo->offset <= up->minused
- && fo->offset + fosize <= up->minused)
- || fo->offset >= up->maxused)
- || (fo->offset == lastfooffset
- && fosize == lastfosize
- && currfotype == lastfotype))
- continue;
- sv = GGC_NEW (struct subvar);
- sv->next = *subvars;
- sv->var = create_sft (var, fo->type, fo->offset, fosize);
-
- if (dump_file)
- {
- fprintf (dump_file, "structure field tag %s created for var %s",
- get_name (sv->var), get_name (var));
- fprintf (dump_file, " offset " HOST_WIDE_INT_PRINT_DEC,
- SFT_OFFSET (sv->var));
- fprintf (dump_file, " size " HOST_WIDE_INT_PRINT_DEC,
- SFT_SIZE (sv->var));
- fprintf (dump_file, "\n");
- }
-
- lastfotype = currfotype;
- lastfooffset = fo->offset;
- lastfosize = fosize;
- *subvars = sv;
+ if (stmt_may_clobber_ref_p (def_stmt, ref))
+ break;
+ vuse = gimple_vuse (def_stmt);
}
+ }
+ while (vuse);
- /* Once we have created subvars, the original is no longer call
- clobbered on its own. Its call clobbered status depends
- completely on the call clobbered status of the subvars.
+ if (visited)
+ BITMAP_FREE (visited);
- add_referenced_var in the above loop will take care of
- marking subvars of global variables as call clobbered for us
- to start, since they are global as well. */
- clear_call_clobbered (var);
- }
+ timevar_pop (TV_ALIAS_STMT_WALK);
- VEC_free (fieldoff_s, heap, fieldstack);
+ return res;
}
-/* Find the conservative answer to the question of what portions of what
- structures are used by this statement. We assume that if we have a
- component ref with a known size + offset, that we only need that part
- of the structure. For unknown cases, or cases where we do something
- to the whole structure, we assume we need to create fields for the
- entire structure. */
+/* Based on the memory reference REF call WALKER for each vdef which
+ defining statement may clobber REF, starting with VDEF. If REF
+ is NULL_TREE, each defining statement is visited.
-static tree
-find_used_portions (tree *tp, int *walk_subtrees, void *lhs_p)
-{
- switch (TREE_CODE (*tp))
- {
- case MODIFY_EXPR:
- /* Recurse manually here to track whether the use is in the
- LHS of an assignment. */
- find_used_portions (&TREE_OPERAND (*tp, 0), walk_subtrees, tp);
- return find_used_portions (&TREE_OPERAND (*tp, 1), walk_subtrees, NULL);
- case REALPART_EXPR:
- case IMAGPART_EXPR:
- case COMPONENT_REF:
- case ARRAY_REF:
- {
- HOST_WIDE_INT bitsize;
- HOST_WIDE_INT bitmaxsize;
- HOST_WIDE_INT bitpos;
- tree ref;
- ref = get_ref_base_and_extent (*tp, &bitpos, &bitsize, &bitmaxsize);
- if (DECL_P (ref)
- && var_can_have_subvars (ref)
- && bitmaxsize != -1)
- {
- size_t uid = DECL_UID (ref);
- used_part_t up;
-
- up = get_or_create_used_part_for (uid);
-
- if (bitpos <= up->minused)
- up->minused = bitpos;
- if ((bitpos + bitmaxsize >= up->maxused))
- up->maxused = bitpos + bitmaxsize;
-
- if (bitsize == bitmaxsize)
- up->explicit_uses = true;
- else
- up->implicit_uses = true;
- if (!lhs_p)
- up->write_only = false;
- up_insert (uid, up);
-
- *walk_subtrees = 0;
- return NULL_TREE;
- }
- }
- break;
- /* This is here to make sure we mark the entire base variable as used
- when you take its address. Because our used portion analysis is
- simple, we aren't looking at casts or pointer arithmetic to see what
- happens when you take the address. */
- case ADDR_EXPR:
- {
- tree var = get_base_address (TREE_OPERAND (*tp, 0));
-
- if (var
- && DECL_P (var)
- && DECL_SIZE (var)
- && var_can_have_subvars (var)
- && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
- {
- used_part_t up;
- size_t uid = DECL_UID (var);
-
- up = get_or_create_used_part_for (uid);
-
- up->minused = 0;
- up->maxused = TREE_INT_CST_LOW (DECL_SIZE (var));
- up->implicit_uses = true;
- if (!lhs_p)
- up->write_only = false;
-
- up_insert (uid, up);
- *walk_subtrees = 0;
- return NULL_TREE;
- }
- }
- break;
- case CALL_EXPR:
- {
- tree *arg;
- for (arg = &TREE_OPERAND (*tp, 1); *arg; arg = &TREE_CHAIN (*arg))
- {
- if (TREE_CODE (TREE_VALUE (*arg)) != ADDR_EXPR)
- find_used_portions (&TREE_VALUE (*arg), walk_subtrees, NULL);
- }
- *walk_subtrees = 0;
- return NULL_TREE;
- }
- case VAR_DECL:
- case PARM_DECL:
- case RESULT_DECL:
- {
- tree var = *tp;
- if (DECL_SIZE (var)
- && var_can_have_subvars (var)
- && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
- {
- used_part_t up;
- size_t uid = DECL_UID (var);
-
- up = get_or_create_used_part_for (uid);
-
- up->minused = 0;
- up->maxused = TREE_INT_CST_LOW (DECL_SIZE (var));
- up->implicit_uses = true;
-
- up_insert (uid, up);
- *walk_subtrees = 0;
- return NULL_TREE;
- }
- }
- break;
-
- default:
- break;
-
- }
- return NULL_TREE;
-}
+ WALKER is called with REF, the current vdef and DATA. If WALKER
+ returns true the walk is stopped, otherwise it continues.
+
+ At PHI nodes walk_aliased_vdefs forks into one walk for reach
+ PHI argument (but only one walk continues on merge points), the
+ return value is true if any of the walks was successful.
-/* Create structure field variables for structures used in this function. */
+ The function returns the number of statements walked. */
static unsigned int
-create_structure_vars (void)
+walk_aliased_vdefs_1 (tree ref, tree vdef,
+ bool (*walker)(tree, tree, void *), void *data,
+ bitmap *visited, unsigned int cnt)
{
- basic_block bb;
- safe_referenced_var_iterator rvi;
- VEC (tree, heap) *varvec = NULL;
- tree var;
-
- used_portions = htab_create (10, used_part_map_hash, used_part_map_eq,
- free_used_part_map);
-
- FOR_EACH_BB (bb)
+ do
{
- block_stmt_iterator bsi;
- for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
+ gimple def_stmt = SSA_NAME_DEF_STMT (vdef);
+
+ if (*visited
+ && !bitmap_set_bit (*visited, SSA_NAME_VERSION (vdef)))
+ return cnt;
+
+ if (gimple_nop_p (def_stmt))
+ return cnt;
+ else if (gimple_code (def_stmt) == GIMPLE_PHI)
{
- walk_tree_without_duplicates (bsi_stmt_ptr (bsi),
- find_used_portions,
- NULL);
+ unsigned i;
+ if (!*visited)
+ *visited = BITMAP_ALLOC (NULL);
+ for (i = 0; i < gimple_phi_num_args (def_stmt); ++i)
+ cnt += walk_aliased_vdefs_1 (ref, gimple_phi_arg_def (def_stmt, i),
+ walker, data, visited, 0);
+ return cnt;
}
+
+ /* ??? Do we want to account this to TV_ALIAS_STMT_WALK? */
+ cnt++;
+ if ((!ref
+ || stmt_may_clobber_ref_p (def_stmt, ref))
+ && (*walker) (ref, vdef, data))
+ return cnt;
+
+ vdef = gimple_vuse (def_stmt);
}
- FOR_EACH_REFERENCED_VAR_SAFE (var, varvec, rvi)
- {
- /* The C++ FE creates vars without DECL_SIZE set, for some reason. */
- if (var
- && DECL_SIZE (var)
- && var_can_have_subvars (var)
- && !MTAG_P (var)
- && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
- create_overlap_variables_for (var);
- }
- htab_delete (used_portions);
- VEC_free (tree, heap, varvec);
- return 0;
+ while (1);
}
-static bool
-gate_structure_vars (void)
+unsigned int
+walk_aliased_vdefs (tree ref, tree vdef,
+ bool (*walker)(tree, tree, void *), void *data,
+ bitmap *visited)
{
- return flag_tree_salias != 0;
-}
+ bitmap local_visited = NULL;
+ unsigned int ret;
-struct tree_opt_pass pass_create_structure_vars =
-{
- "salias", /* name */
- gate_structure_vars, /* gate */
- create_structure_vars, /* execute */
- NULL, /* sub */
- NULL, /* next */
- 0, /* static_pass_number */
- 0, /* tv_id */
- PROP_cfg, /* properties_required */
- 0, /* properties_provided */
- 0, /* properties_destroyed */
- 0, /* todo_flags_start */
- TODO_dump_func, /* todo_flags_finish */
- 0 /* letter */
-};
-
-/* Reset the DECL_CALL_CLOBBERED flags on our referenced vars. In
- theory, this only needs to be done for globals. */
+ timevar_push (TV_ALIAS_STMT_WALK);
-static unsigned int
-reset_cc_flags (void)
-{
- tree var;
- referenced_var_iterator rvi;
+ ret = walk_aliased_vdefs_1 (ref, vdef, walker, data,
+ visited ? visited : &local_visited, 0);
+ if (local_visited)
+ BITMAP_FREE (local_visited);
- FOR_EACH_REFERENCED_VAR (var, rvi)
- DECL_CALL_CLOBBERED (var) = false;
- return 0;
+ timevar_pop (TV_ALIAS_STMT_WALK);
+
+ return ret;
}
-struct tree_opt_pass pass_reset_cc_flags =
-{
- NULL, /* name */
- NULL, /* gate */
- reset_cc_flags, /* execute */
- NULL, /* sub */
- NULL, /* next */
- 0, /* static_pass_number */
- 0, /* tv_id */
- PROP_referenced_vars |PROP_cfg, /* properties_required */
- 0, /* properties_provided */
- 0, /* properties_destroyed */
- 0, /* todo_flags_start */
- 0, /* todo_flags_finish */
- 0 /* letter */
-};
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