blob: ce667ff32b9eac930698fa667e51e887ee6d1215 [file] [log] [blame]
/* Alias analysis for trees.
Copyright (C) 2004-2021 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 3, or (at your option)
any later version.
GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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 COPYING3. If not see
<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "target.h"
#include "rtl.h"
#include "tree.h"
#include "gimple.h"
#include "timevar.h" /* for TV_ALIAS_STMT_WALK */
#include "ssa.h"
#include "cgraph.h"
#include "tree-pretty-print.h"
#include "alias.h"
#include "fold-const.h"
#include "langhooks.h"
#include "dumpfile.h"
#include "tree-eh.h"
#include "tree-dfa.h"
#include "ipa-reference.h"
#include "varasm.h"
#include "ipa-modref-tree.h"
#include "ipa-modref.h"
#include "attr-fnspec.h"
#include "errors.h"
#include "dbgcnt.h"
#include "gimple-pretty-print.h"
#include "print-tree.h"
#include "tree-ssa-alias-compare.h"
#include "builtins.h"
/* Broad overview of how alias analysis on gimple works:
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.
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.
This file contains functions for disambiguating memory references,
the so called alias-oracle and tools for walking of the gimple IL.
The main alias-oracle entry-points are
bool stmt_may_clobber_ref_p (gimple *, tree)
This function queries if a statement may invalidate (parts of)
the memory designated by the reference tree argument.
bool ref_maybe_used_by_stmt_p (gimple *, tree)
This function queries if a statement may need (parts of) the
memory designated by the reference tree argument.
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.
bool refs_may_alias_p (tree, tree)
This function tries to disambiguate two reference trees.
bool ptr_deref_may_alias_global_p (tree)
This function queries if dereferencing a pointer variable may
alias global memory.
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. */
static int nonoverlapping_refs_since_match_p (tree, tree, tree, tree, bool);
static bool nonoverlapping_component_refs_p (const_tree, const_tree);
/* Query statistics for the different low-level disambiguators.
A high-level query may trigger multiple of them. */
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;
unsigned HOST_WIDE_INT aliasing_component_refs_p_may_alias;
unsigned HOST_WIDE_INT aliasing_component_refs_p_no_alias;
unsigned HOST_WIDE_INT nonoverlapping_component_refs_p_may_alias;
unsigned HOST_WIDE_INT nonoverlapping_component_refs_p_no_alias;
unsigned HOST_WIDE_INT nonoverlapping_refs_since_match_p_may_alias;
unsigned HOST_WIDE_INT nonoverlapping_refs_since_match_p_must_overlap;
unsigned HOST_WIDE_INT nonoverlapping_refs_since_match_p_no_alias;
unsigned HOST_WIDE_INT modref_use_may_alias;
unsigned HOST_WIDE_INT modref_use_no_alias;
unsigned HOST_WIDE_INT modref_clobber_may_alias;
unsigned HOST_WIDE_INT modref_clobber_no_alias;
unsigned HOST_WIDE_INT modref_tests;
unsigned HOST_WIDE_INT modref_baseptr_tests;
} alias_stats;
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);
fprintf (s, " nonoverlapping_component_refs_p: "
HOST_WIDE_INT_PRINT_DEC" disambiguations, "
HOST_WIDE_INT_PRINT_DEC" queries\n",
alias_stats.nonoverlapping_component_refs_p_no_alias,
alias_stats.nonoverlapping_component_refs_p_no_alias
+ alias_stats.nonoverlapping_component_refs_p_may_alias);
fprintf (s, " nonoverlapping_refs_since_match_p: "
HOST_WIDE_INT_PRINT_DEC" disambiguations, "
HOST_WIDE_INT_PRINT_DEC" must overlaps, "
HOST_WIDE_INT_PRINT_DEC" queries\n",
alias_stats.nonoverlapping_refs_since_match_p_no_alias,
alias_stats.nonoverlapping_refs_since_match_p_must_overlap,
alias_stats.nonoverlapping_refs_since_match_p_no_alias
+ alias_stats.nonoverlapping_refs_since_match_p_may_alias
+ alias_stats.nonoverlapping_refs_since_match_p_must_overlap);
fprintf (s, " aliasing_component_refs_p: "
HOST_WIDE_INT_PRINT_DEC" disambiguations, "
HOST_WIDE_INT_PRINT_DEC" queries\n",
alias_stats.aliasing_component_refs_p_no_alias,
alias_stats.aliasing_component_refs_p_no_alias
+ alias_stats.aliasing_component_refs_p_may_alias);
dump_alias_stats_in_alias_c (s);
fprintf (s, "\nModref stats:\n");
fprintf (s, " modref use: "
HOST_WIDE_INT_PRINT_DEC" disambiguations, "
HOST_WIDE_INT_PRINT_DEC" queries\n",
alias_stats.modref_use_no_alias,
alias_stats.modref_use_no_alias
+ alias_stats.modref_use_may_alias);
fprintf (s, " modref clobber: "
HOST_WIDE_INT_PRINT_DEC" disambiguations, "
HOST_WIDE_INT_PRINT_DEC" queries\n"
" " HOST_WIDE_INT_PRINT_DEC" tbaa queries (%f per modref query)\n"
" " HOST_WIDE_INT_PRINT_DEC" base compares (%f per modref query)\n",
alias_stats.modref_clobber_no_alias,
alias_stats.modref_clobber_no_alias
+ alias_stats.modref_clobber_may_alias,
alias_stats.modref_tests,
((double)alias_stats.modref_tests)
/ (alias_stats.modref_clobber_no_alias
+ alias_stats.modref_clobber_may_alias),
alias_stats.modref_baseptr_tests,
((double)alias_stats.modref_baseptr_tests)
/ (alias_stats.modref_clobber_no_alias
+ alias_stats.modref_clobber_may_alias));
}
/* Return true, if dereferencing PTR may alias with a global variable. */
bool
ptr_deref_may_alias_global_p (tree ptr)
{
struct ptr_info_def *pi;
/* If we end up with a pointer constant here that may point
to global memory. */
if (TREE_CODE (ptr) != SSA_NAME)
return true;
pi = SSA_NAME_PTR_INFO (ptr);
/* If we do not have points-to information for this variable,
we have to punt. */
if (!pi)
return true;
/* ??? This does not use TBAA to prune globals ptr may not access. */
return pt_solution_includes_global (&pi->pt);
}
/* Return true if dereferencing PTR may alias DECL.
The caller is responsible for applying TBAA to see if PTR
may access DECL at all. */
static bool
ptr_deref_may_alias_decl_p (tree ptr, tree decl)
{
struct ptr_info_def *pi;
/* Conversions are irrelevant for points-to information and
data-dependence analysis can feed us those. */
STRIP_NOPS (ptr);
/* Anything we do not explicilty handle aliases. */
if ((TREE_CODE (ptr) != SSA_NAME
&& TREE_CODE (ptr) != ADDR_EXPR
&& TREE_CODE (ptr) != POINTER_PLUS_EXPR)
|| !POINTER_TYPE_P (TREE_TYPE (ptr))
|| (!VAR_P (decl)
&& TREE_CODE (decl) != PARM_DECL
&& TREE_CODE (decl) != RESULT_DECL))
return true;
/* Disregard pointer offsetting. */
if (TREE_CODE (ptr) == POINTER_PLUS_EXPR)
{
do
{
ptr = TREE_OPERAND (ptr, 0);
}
while (TREE_CODE (ptr) == POINTER_PLUS_EXPR);
return ptr_deref_may_alias_decl_p (ptr, decl);
}
/* ADDR_EXPR pointers either just offset another pointer or directly
specify the pointed-to set. */
if (TREE_CODE (ptr) == ADDR_EXPR)
{
tree base = get_base_address (TREE_OPERAND (ptr, 0));
if (base
&& (TREE_CODE (base) == MEM_REF
|| TREE_CODE (base) == TARGET_MEM_REF))
ptr = TREE_OPERAND (base, 0);
else if (base
&& DECL_P (base))
return compare_base_decls (base, decl) != 0;
else if (base
&& CONSTANT_CLASS_P (base))
return false;
else
return true;
}
/* Non-aliased variables cannot be pointed to. */
if (!may_be_aliased (decl))
return false;
/* 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;
return pt_solution_includes (&pi->pt, decl);
}
/* Return true if dereferenced PTR1 and PTR2 may alias.
The caller is responsible for applying TBAA to see if accesses
through PTR1 and PTR2 may conflict at all. */
bool
ptr_derefs_may_alias_p (tree ptr1, tree ptr2)
{
struct ptr_info_def *pi1, *pi2;
/* Conversions are irrelevant for points-to information and
data-dependence analysis can feed us those. */
STRIP_NOPS (ptr1);
STRIP_NOPS (ptr2);
/* Disregard pointer offsetting. */
if (TREE_CODE (ptr1) == POINTER_PLUS_EXPR)
{
do
{
ptr1 = TREE_OPERAND (ptr1, 0);
}
while (TREE_CODE (ptr1) == POINTER_PLUS_EXPR);
return ptr_derefs_may_alias_p (ptr1, ptr2);
}
if (TREE_CODE (ptr2) == POINTER_PLUS_EXPR)
{
do
{
ptr2 = TREE_OPERAND (ptr2, 0);
}
while (TREE_CODE (ptr2) == POINTER_PLUS_EXPR);
return ptr_derefs_may_alias_p (ptr1, ptr2);
}
/* ADDR_EXPR pointers either just offset another pointer or directly
specify the pointed-to set. */
if (TREE_CODE (ptr1) == ADDR_EXPR)
{
tree base = get_base_address (TREE_OPERAND (ptr1, 0));
if (base
&& (TREE_CODE (base) == MEM_REF
|| TREE_CODE (base) == TARGET_MEM_REF))
return ptr_derefs_may_alias_p (TREE_OPERAND (base, 0), ptr2);
else if (base
&& DECL_P (base))
return ptr_deref_may_alias_decl_p (ptr2, base);
else
return true;
}
if (TREE_CODE (ptr2) == ADDR_EXPR)
{
tree base = get_base_address (TREE_OPERAND (ptr2, 0));
if (base
&& (TREE_CODE (base) == MEM_REF
|| TREE_CODE (base) == TARGET_MEM_REF))
return ptr_derefs_may_alias_p (ptr1, TREE_OPERAND (base, 0));
else if (base
&& DECL_P (base))
return ptr_deref_may_alias_decl_p (ptr1, base);
else
return true;
}
/* From here we require SSA name pointers. Anything else aliases. */
if (TREE_CODE (ptr1) != SSA_NAME
|| TREE_CODE (ptr2) != SSA_NAME
|| !POINTER_TYPE_P (TREE_TYPE (ptr1))
|| !POINTER_TYPE_P (TREE_TYPE (ptr2)))
return true;
/* 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;
/* 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;
/* ??? This does not use TBAA to prune decls from the intersection
that not both pointers may access. */
return pt_solutions_intersect (&pi1->pt, &pi2->pt);
}
/* Return true if dereferencing PTR may alias *REF.
The caller is responsible for applying TBAA to see if PTR
may access *REF at all. */
static bool
ptr_deref_may_alias_ref_p_1 (tree ptr, ao_ref *ref)
{
tree base = ao_ref_base (ref);
if (TREE_CODE (base) == MEM_REF
|| TREE_CODE (base) == TARGET_MEM_REF)
return ptr_derefs_may_alias_p (ptr, TREE_OPERAND (base, 0));
else if (DECL_P (base))
return ptr_deref_may_alias_decl_p (ptr, base);
return true;
}
/* Returns true if PTR1 and PTR2 compare unequal because of points-to. */
bool
ptrs_compare_unequal (tree ptr1, tree ptr2)
{
/* First resolve the pointers down to a SSA name pointer base or
a VAR_DECL, PARM_DECL or RESULT_DECL. This explicitely does
not yet try to handle LABEL_DECLs, FUNCTION_DECLs, CONST_DECLs
or STRING_CSTs which needs points-to adjustments to track them
in the points-to sets. */
tree obj1 = NULL_TREE;
tree obj2 = NULL_TREE;
if (TREE_CODE (ptr1) == ADDR_EXPR)
{
tree tem = get_base_address (TREE_OPERAND (ptr1, 0));
if (! tem)
return false;
if (VAR_P (tem)
|| TREE_CODE (tem) == PARM_DECL
|| TREE_CODE (tem) == RESULT_DECL)
obj1 = tem;
else if (TREE_CODE (tem) == MEM_REF)
ptr1 = TREE_OPERAND (tem, 0);
}
if (TREE_CODE (ptr2) == ADDR_EXPR)
{
tree tem = get_base_address (TREE_OPERAND (ptr2, 0));
if (! tem)
return false;
if (VAR_P (tem)
|| TREE_CODE (tem) == PARM_DECL
|| TREE_CODE (tem) == RESULT_DECL)
obj2 = tem;
else if (TREE_CODE (tem) == MEM_REF)
ptr2 = TREE_OPERAND (tem, 0);
}
/* Canonicalize ptr vs. object. */
if (TREE_CODE (ptr1) == SSA_NAME && obj2)
{
std::swap (ptr1, ptr2);
std::swap (obj1, obj2);
}
if (obj1 && obj2)
/* Other code handles this correctly, no need to duplicate it here. */;
else if (obj1 && TREE_CODE (ptr2) == SSA_NAME)
{
struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr2);
/* We may not use restrict to optimize pointer comparisons.
See PR71062. So we have to assume that restrict-pointed-to
may be in fact obj1. */
if (!pi
|| pi->pt.vars_contains_restrict
|| pi->pt.vars_contains_interposable)
return false;
if (VAR_P (obj1)
&& (TREE_STATIC (obj1) || DECL_EXTERNAL (obj1)))
{
varpool_node *node = varpool_node::get (obj1);
/* If obj1 may bind to NULL give up (see below). */
if (! node
|| ! node->nonzero_address ()
|| ! decl_binds_to_current_def_p (obj1))
return false;
}
return !pt_solution_includes (&pi->pt, obj1);
}
/* ??? We'd like to handle ptr1 != NULL and ptr1 != ptr2
but those require pt.null to be conservatively correct. */
return false;
}
/* Returns whether reference REF to BASE may refer to global memory. */
static bool
ref_may_alias_global_p_1 (tree base)
{
if (DECL_P (base))
return is_global_var (base);
else if (TREE_CODE (base) == MEM_REF
|| TREE_CODE (base) == TARGET_MEM_REF)
return ptr_deref_may_alias_global_p (TREE_OPERAND (base, 0));
return true;
}
bool
ref_may_alias_global_p (ao_ref *ref)
{
tree base = ao_ref_base (ref);
return ref_may_alias_global_p_1 (base);
}
bool
ref_may_alias_global_p (tree ref)
{
tree base = get_base_address (ref);
return ref_may_alias_global_p_1 (base);
}
/* Return true whether STMT may clobber global memory. */
bool
stmt_may_clobber_global_p (gimple *stmt)
{
tree lhs;
if (!gimple_vdef (stmt))
return false;
/* ??? We can ask the oracle whether an artificial pointer
dereference with a pointer with points-to information covering
all global memory (what about non-address taken memory?) maybe
clobbered by this call. As there is at the moment no convenient
way of doing that without generating garbage do some manual
checking instead.
??? We could make a NULL ao_ref argument to the various
predicates special, meaning any global memory. */
switch (gimple_code (stmt))
{
case GIMPLE_ASSIGN:
lhs = gimple_assign_lhs (stmt);
return (TREE_CODE (lhs) != SSA_NAME
&& ref_may_alias_global_p (lhs));
case GIMPLE_CALL:
return true;
default:
return true;
}
}
/* Dump alias information on FILE. */
void
dump_alias_info (FILE *file)
{
unsigned i;
tree ptr;
const char *funcname
= lang_hooks.decl_printable_name (current_function_decl, 2);
tree var;
fprintf (file, "\n\nAlias information for %s\n\n", funcname);
fprintf (file, "Aliased symbols\n\n");
FOR_EACH_LOCAL_DECL (cfun, i, var)
{
if (may_be_aliased (var))
dump_variable (file, var);
}
fprintf (file, "\nCall clobber information\n");
fprintf (file, "\nESCAPED");
dump_points_to_solution (file, &cfun->gimple_df->escaped);
fprintf (file, "\n\nFlow-insensitive points-to information\n\n");
FOR_EACH_SSA_NAME (i, ptr, cfun)
{
struct ptr_info_def *pi;
if (!POINTER_TYPE_P (TREE_TYPE (ptr))
|| SSA_NAME_IN_FREE_LIST (ptr))
continue;
pi = SSA_NAME_PTR_INFO (ptr);
if (pi)
dump_points_to_info_for (file, ptr);
}
fprintf (file, "\n");
}
/* Dump alias information on stderr. */
DEBUG_FUNCTION void
debug_alias_info (void)
{
dump_alias_info (stderr);
}
/* Dump the points-to set *PT into FILE. */
void
dump_points_to_solution (FILE *file, struct pt_solution *pt)
{
if (pt->anything)
fprintf (file, ", points-to anything");
if (pt->nonlocal)
fprintf (file, ", points-to non-local");
if (pt->escaped)
fprintf (file, ", points-to escaped");
if (pt->ipa_escaped)
fprintf (file, ", points-to unit escaped");
if (pt->null)
fprintf (file, ", points-to NULL");
if (pt->vars)
{
fprintf (file, ", points-to vars: ");
dump_decl_set (file, pt->vars);
if (pt->vars_contains_nonlocal
|| pt->vars_contains_escaped
|| pt->vars_contains_escaped_heap
|| pt->vars_contains_restrict)
{
const char *comma = "";
fprintf (file, " (");
if (pt->vars_contains_nonlocal)
{
fprintf (file, "nonlocal");
comma = ", ";
}
if (pt->vars_contains_escaped)
{
fprintf (file, "%sescaped", comma);
comma = ", ";
}
if (pt->vars_contains_escaped_heap)
{
fprintf (file, "%sescaped heap", comma);
comma = ", ";
}
if (pt->vars_contains_restrict)
{
fprintf (file, "%srestrict", comma);
comma = ", ";
}
if (pt->vars_contains_interposable)
fprintf (file, "%sinterposable", comma);
fprintf (file, ")");
}
}
}
/* Unified dump function for pt_solution. */
DEBUG_FUNCTION void
debug (pt_solution &ref)
{
dump_points_to_solution (stderr, &ref);
}
DEBUG_FUNCTION void
debug (pt_solution *ptr)
{
if (ptr)
debug (*ptr);
else
fprintf (stderr, "<nil>\n");
}
/* Dump points-to information for SSA_NAME PTR into FILE. */
void
dump_points_to_info_for (FILE *file, tree ptr)
{
struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
print_generic_expr (file, ptr, dump_flags);
if (pi)
dump_points_to_solution (file, &pi->pt);
else
fprintf (file, ", points-to anything");
fprintf (file, "\n");
}
/* Dump points-to information for VAR into stderr. */
DEBUG_FUNCTION void
debug_points_to_info_for (tree var)
{
dump_points_to_info_for (stderr, var);
}
/* Initializes the alias-oracle reference representation *R from REF. */
void
ao_ref_init (ao_ref *r, tree ref)
{
r->ref = ref;
r->base = NULL_TREE;
r->offset = 0;
r->size = -1;
r->max_size = -1;
r->ref_alias_set = -1;
r->base_alias_set = -1;
r->volatile_p = ref ? TREE_THIS_VOLATILE (ref) : false;
}
/* Returns the base object of the memory reference *REF. */
tree
ao_ref_base (ao_ref *ref)
{
bool reverse;
if (ref->base)
return ref->base;
ref->base = get_ref_base_and_extent (ref->ref, &ref->offset, &ref->size,
&ref->max_size, &reverse);
return ref->base;
}
/* Returns the base object alias set of the memory reference *REF. */
alias_set_type
ao_ref_base_alias_set (ao_ref *ref)
{
tree base_ref;
if (ref->base_alias_set != -1)
return ref->base_alias_set;
if (!ref->ref)
return 0;
base_ref = ref->ref;
if (TREE_CODE (base_ref) == WITH_SIZE_EXPR)
base_ref = TREE_OPERAND (base_ref, 0);
while (handled_component_p (base_ref))
base_ref = TREE_OPERAND (base_ref, 0);
ref->base_alias_set = get_alias_set (base_ref);
return ref->base_alias_set;
}
/* Returns the reference alias set of the memory reference *REF. */
alias_set_type
ao_ref_alias_set (ao_ref *ref)
{
if (ref->ref_alias_set != -1)
return ref->ref_alias_set;
if (!ref->ref)
return 0;
ref->ref_alias_set = get_alias_set (ref->ref);
return ref->ref_alias_set;
}
/* Returns a type satisfying
get_deref_alias_set (type) == ao_ref_base_alias_set (REF). */
tree
ao_ref_base_alias_ptr_type (ao_ref *ref)
{
tree base_ref;
if (!ref->ref)
return NULL_TREE;
base_ref = ref->ref;
if (TREE_CODE (base_ref) == WITH_SIZE_EXPR)
base_ref = TREE_OPERAND (base_ref, 0);
while (handled_component_p (base_ref))
base_ref = TREE_OPERAND (base_ref, 0);
tree ret = reference_alias_ptr_type (base_ref);
return ret;
}
/* Returns a type satisfying
get_deref_alias_set (type) == ao_ref_alias_set (REF). */
tree
ao_ref_alias_ptr_type (ao_ref *ref)
{
if (!ref->ref)
return NULL_TREE;
tree ret = reference_alias_ptr_type (ref->ref);
return ret;
}
/* Init an alias-oracle reference representation from a gimple pointer
PTR a range specified by OFFSET, SIZE and MAX_SIZE under the assumption
that RANGE_KNOWN is set.
The access is assumed to be only to or after of the pointer target adjusted
by the offset, not before it (even in the case RANGE_KNOWN is false). */
static void
ao_ref_init_from_ptr_and_range (ao_ref *ref, tree ptr,
bool range_known,
poly_int64 offset,
poly_int64 size,
poly_int64 max_size)
{
poly_int64 t, extra_offset = 0;
ref->ref = NULL_TREE;
if (TREE_CODE (ptr) == SSA_NAME)
{
gimple *stmt = SSA_NAME_DEF_STMT (ptr);
if (gimple_assign_single_p (stmt)
&& gimple_assign_rhs_code (stmt) == ADDR_EXPR)
ptr = gimple_assign_rhs1 (stmt);
else if (is_gimple_assign (stmt)
&& gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR
&& ptrdiff_tree_p (gimple_assign_rhs2 (stmt), &extra_offset))
{
ptr = gimple_assign_rhs1 (stmt);
extra_offset *= BITS_PER_UNIT;
}
}
if (TREE_CODE (ptr) == ADDR_EXPR)
{
ref->base = get_addr_base_and_unit_offset (TREE_OPERAND (ptr, 0), &t);
if (ref->base)
ref->offset = BITS_PER_UNIT * t;
else
{
range_known = false;
ref->offset = 0;
ref->base = get_base_address (TREE_OPERAND (ptr, 0));
}
}
else
{
gcc_assert (POINTER_TYPE_P (TREE_TYPE (ptr)));
ref->base = build2 (MEM_REF, char_type_node,
ptr, null_pointer_node);
ref->offset = 0;
}
ref->offset += extra_offset + offset;
if (range_known)
{
ref->max_size = max_size;
ref->size = size;
}
else
ref->max_size = ref->size = -1;
ref->ref_alias_set = 0;
ref->base_alias_set = 0;
ref->volatile_p = false;
}
/* Init an alias-oracle reference representation from a gimple pointer
PTR and a gimple size SIZE in bytes. If SIZE is NULL_TREE then the
size is assumed to be unknown. The access is assumed to be only
to or after of the pointer target, not before it. */
void
ao_ref_init_from_ptr_and_size (ao_ref *ref, tree ptr, tree size)
{
poly_int64 size_hwi;
if (size
&& poly_int_tree_p (size, &size_hwi)
&& coeffs_in_range_p (size_hwi, 0, HOST_WIDE_INT_MAX / BITS_PER_UNIT))
{
size_hwi = size_hwi * BITS_PER_UNIT;
ao_ref_init_from_ptr_and_range (ref, ptr, true, 0, size_hwi, size_hwi);
}
else
ao_ref_init_from_ptr_and_range (ref, ptr, false, 0, -1, -1);
}
/* S1 and S2 are TYPE_SIZE or DECL_SIZE. Compare them:
Return -1 if S1 < S2
Return 1 if S1 > S2
Return 0 if equal or incomparable. */
static int
compare_sizes (tree s1, tree s2)
{
if (!s1 || !s2)
return 0;
poly_uint64 size1;
poly_uint64 size2;
if (!poly_int_tree_p (s1, &size1) || !poly_int_tree_p (s2, &size2))
return 0;
if (known_lt (size1, size2))
return -1;
if (known_lt (size2, size1))
return 1;
return 0;
}
/* Compare TYPE1 and TYPE2 by its size.
Return -1 if size of TYPE1 < size of TYPE2
Return 1 if size of TYPE1 > size of TYPE2
Return 0 if types are of equal sizes or we can not compare them. */
static int
compare_type_sizes (tree type1, tree type2)
{
/* Be conservative for arrays and vectors. We want to support partial
overlap on int[3] and int[3] as tested in gcc.dg/torture/alias-2.c. */
while (TREE_CODE (type1) == ARRAY_TYPE
|| TREE_CODE (type1) == VECTOR_TYPE)
type1 = TREE_TYPE (type1);
while (TREE_CODE (type2) == ARRAY_TYPE
|| TREE_CODE (type2) == VECTOR_TYPE)
type2 = TREE_TYPE (type2);
return compare_sizes (TYPE_SIZE (type1), TYPE_SIZE (type2));
}
/* 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. */
static inline int
same_type_for_tbaa (tree type1, tree type2)
{
type1 = TYPE_MAIN_VARIANT (type1);
type2 = TYPE_MAIN_VARIANT (type2);
/* Handle the most common case first. */
if (type1 == type2)
return 1;
/* If we would have to do structural comparison bail out. */
if (TYPE_STRUCTURAL_EQUALITY_P (type1)
|| TYPE_STRUCTURAL_EQUALITY_P (type2))
return -1;
/* Compare the canonical types. */
if (TYPE_CANONICAL (type1) == TYPE_CANONICAL (type2))
return 1;
/* ??? 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;
/* ??? In Ada, an lvalue of an unconstrained type can be used to access an
object of one of its constrained subtypes, e.g. when a function with an
unconstrained parameter passed by reference is called on an object and
inlined. But, even in the case of a fixed size, type and subtypes are
not equivalent enough as to share the same TYPE_CANONICAL, since this
would mean that conversions between them are useless, whereas they are
not (e.g. type and subtypes can have different modes). So, in the end,
they are only guaranteed to have the same alias set. */
alias_set_type set1 = get_alias_set (type1);
alias_set_type set2 = get_alias_set (type2);
if (set1 == set2)
return -1;
/* Pointers to void are considered compatible with all other pointers,
so for two pointers see what the alias set resolution thinks. */
if (POINTER_TYPE_P (type1)
&& POINTER_TYPE_P (type2)
&& alias_sets_conflict_p (set1, set2))
return -1;
/* The types are known to be not equal. */
return 0;
}
/* Return true if TYPE is a composite type (i.e. we may apply one of handled
components on it). */
static bool
type_has_components_p (tree type)
{
return AGGREGATE_TYPE_P (type) || VECTOR_TYPE_P (type)
|| TREE_CODE (type) == COMPLEX_TYPE;
}
/* MATCH1 and MATCH2 which are part of access path of REF1 and REF2
respectively are either pointing to same address or are completely
disjoint. If PARTIAL_OVERLAP is true, assume that outermost arrays may
just partly overlap.
Try to disambiguate using the access path starting from the match
and return false if there is no conflict.
Helper for aliasing_component_refs_p. */
static bool
aliasing_matching_component_refs_p (tree match1, tree ref1,
poly_int64 offset1, poly_int64 max_size1,
tree match2, tree ref2,
poly_int64 offset2, poly_int64 max_size2,
bool partial_overlap)
{
poly_int64 offadj, sztmp, msztmp;
bool reverse;
if (!partial_overlap)
{
get_ref_base_and_extent (match2, &offadj, &sztmp, &msztmp, &reverse);
offset2 -= offadj;
get_ref_base_and_extent (match1, &offadj, &sztmp, &msztmp, &reverse);
offset1 -= offadj;
if (!ranges_maybe_overlap_p (offset1, max_size1, offset2, max_size2))
{
++alias_stats.aliasing_component_refs_p_no_alias;
return false;
}
}
int cmp = nonoverlapping_refs_since_match_p (match1, ref1, match2, ref2,
partial_overlap);
if (cmp == 1
|| (cmp == -1 && nonoverlapping_component_refs_p (ref1, ref2)))
{
++alias_stats.aliasing_component_refs_p_no_alias;
return false;
}
++alias_stats.aliasing_component_refs_p_may_alias;
return true;
}
/* Return true if REF is reference to zero sized trailing array. I.e.
struct foo {int bar; int array[0];} *fooptr;
fooptr->array. */
static bool
component_ref_to_zero_sized_trailing_array_p (tree ref)
{
return (TREE_CODE (ref) == COMPONENT_REF
&& TREE_CODE (TREE_TYPE (TREE_OPERAND (ref, 1))) == ARRAY_TYPE
&& (!TYPE_SIZE (TREE_TYPE (TREE_OPERAND (ref, 1)))
|| integer_zerop (TYPE_SIZE (TREE_TYPE (TREE_OPERAND (ref, 1)))))
&& array_at_struct_end_p (ref));
}
/* Worker for aliasing_component_refs_p. Most parameters match parameters of
aliasing_component_refs_p.
Walk access path REF2 and try to find type matching TYPE1
(which is a start of possibly aliasing access path REF1).
If match is found, try to disambiguate.
Return 0 for sucessful disambiguation.
Return 1 if match was found but disambiguation failed
Return -1 if there is no match.
In this case MAYBE_MATCH is set to 0 if there is no type matching TYPE1
in access patch REF2 and -1 if we are not sure. */
static int
aliasing_component_refs_walk (tree ref1, tree type1, tree base1,
poly_int64 offset1, poly_int64 max_size1,
tree end_struct_ref1,
tree ref2, tree base2,
poly_int64 offset2, poly_int64 max_size2,
bool *maybe_match)
{
tree ref = ref2;
int same_p = 0;
while (true)
{
/* We walk from inner type to the outer types. If type we see is
already too large to be part of type1, terminate the search. */
int cmp = compare_type_sizes (type1, TREE_TYPE (ref));
if (cmp < 0
&& (!end_struct_ref1
|| compare_type_sizes (TREE_TYPE (end_struct_ref1),
TREE_TYPE (ref)) < 0))
break;
/* If types may be of same size, see if we can decide about their
equality. */
if (cmp == 0)
{
same_p = same_type_for_tbaa (TREE_TYPE (ref), type1);
if (same_p == 1)
break;
/* In case we can't decide whether types are same try to
continue looking for the exact match.
Remember however that we possibly saw a match
to bypass the access path continuations tests we do later. */
if (same_p == -1)
*maybe_match = true;
}
if (!handled_component_p (ref))
break;
ref = TREE_OPERAND (ref, 0);
}
if (same_p == 1)
{
bool partial_overlap = false;
/* We assume that arrays can overlap by multiple of their elements
size as tested in gcc.dg/torture/alias-2.c.
This partial overlap happen only when both arrays are bases of
the access and not contained within another component ref.
To be safe we also assume partial overlap for VLAs. */
if (TREE_CODE (TREE_TYPE (base1)) == ARRAY_TYPE
&& (!TYPE_SIZE (TREE_TYPE (base1))
|| TREE_CODE (TYPE_SIZE (TREE_TYPE (base1))) != INTEGER_CST
|| ref == base2))
{
/* Setting maybe_match to true triggers
nonoverlapping_component_refs_p test later that still may do
useful disambiguation. */
*maybe_match = true;
partial_overlap = true;
}
return aliasing_matching_component_refs_p (base1, ref1,
offset1, max_size1,
ref, ref2,
offset2, max_size2,
partial_overlap);
}
return -1;
}
/* Consider access path1 base1....ref1 and access path2 base2...ref2.
Return true if they can be composed to single access path
base1...ref1...base2...ref2.
REF_TYPE1 if type of REF1. END_STRUCT_PAST_END1 is true if there is
a trailing array access after REF1 in the non-TBAA part of the access.
REF1_ALIAS_SET is the alias set of REF1.
BASE_TYPE2 is type of base2. END_STRUCT_REF2 is non-NULL if there is
a trailing array access in the TBAA part of access path2.
BASE2_ALIAS_SET is the alias set of base2. */
bool
access_path_may_continue_p (tree ref_type1, bool end_struct_past_end1,
alias_set_type ref1_alias_set,
tree base_type2, tree end_struct_ref2,
alias_set_type base2_alias_set)
{
/* Access path can not continue past types with no components. */
if (!type_has_components_p (ref_type1))
return false;
/* If first access path ends by too small type to hold base of
the second access path, typically paths can not continue.
Punt if end_struct_past_end1 is true. We want to support arbitrary
type puning past first COMPONENT_REF to union because redundant store
elimination depends on this, see PR92152. For this reason we can not
check size of the reference because types may partially overlap. */
if (!end_struct_past_end1)
{
if (compare_type_sizes (ref_type1, base_type2) < 0)
return false;
/* If the path2 contains trailing array access we can strenghten the check
to verify that also the size of element of the trailing array fits.
In fact we could check for offset + type_size, but we do not track
offsets and this is quite side case. */
if (end_struct_ref2
&& compare_type_sizes (ref_type1, TREE_TYPE (end_struct_ref2)) < 0)
return false;
}
return (base2_alias_set == ref1_alias_set
|| alias_set_subset_of (base2_alias_set, ref1_alias_set));
}
/* 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.
REF1_ALIAS_SET, BASE1_ALIAS_SET, REF2_ALIAS_SET and BASE2_ALIAS_SET
are the respective alias sets. */
static bool
aliasing_component_refs_p (tree ref1,
alias_set_type ref1_alias_set,
alias_set_type base1_alias_set,
poly_int64 offset1, poly_int64 max_size1,
tree ref2,
alias_set_type ref2_alias_set,
alias_set_type base2_alias_set,
poly_int64 offset2, poly_int64 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 base1, base2;
tree type1, type2;
bool maybe_match = false;
tree end_struct_ref1 = NULL, end_struct_ref2 = NULL;
bool end_struct_past_end1 = false;
bool end_struct_past_end2 = false;
/* Choose bases and base types to search for.
The access path is as follows:
base....end_of_tbaa_ref...actual_ref
At one place in the access path may be a reference to zero sized or
trailing array.
We generally discard the segment after end_of_tbaa_ref however
we need to be careful in case it contains zero sized or trailing array.
These may happen after reference to union and in this case we need to
not disambiguate type puning scenarios.
We set:
base1 to point to base
ref1 to point to end_of_tbaa_ref
end_struct_ref1 to point the trailing reference (if it exists
in range base....end_of_tbaa_ref
end_struct_past_end1 is true if this trailing reference occurs in
end_of_tbaa_ref...actual_ref. */
base1 = ref1;
while (handled_component_p (base1))
{
/* Generally access paths are monotous in the size of object. The
exception are trailing arrays of structures. I.e.
struct a {int array[0];};
or
struct a {int array1[0]; int array[];};
Such struct has size 0 but accesses to a.array may have non-zero size.
In this case the size of TREE_TYPE (base1) is smaller than
size of TREE_TYPE (TREE_OPERAND (base1, 0)).
Because we compare sizes of arrays just by sizes of their elements,
we only need to care about zero sized array fields here. */
if (component_ref_to_zero_sized_trailing_array_p (base1))
{
gcc_checking_assert (!end_struct_ref1);
end_struct_ref1 = base1;
}
if (ends_tbaa_access_path_p (base1))
{
ref1 = TREE_OPERAND (base1, 0);
if (end_struct_ref1)
{
end_struct_past_end1 = true;
end_struct_ref1 = NULL;
}
}
base1 = TREE_OPERAND (base1, 0);
}
type1 = TREE_TYPE (base1);
base2 = ref2;
while (handled_component_p (base2))
{
if (component_ref_to_zero_sized_trailing_array_p (base2))
{
gcc_checking_assert (!end_struct_ref2);
end_struct_ref2 = base2;
}
if (ends_tbaa_access_path_p (base2))
{
ref2 = TREE_OPERAND (base2, 0);
if (end_struct_ref2)
{
end_struct_past_end2 = true;
end_struct_ref2 = NULL;
}
}
base2 = TREE_OPERAND (base2, 0);
}
type2 = TREE_TYPE (base2);
/* Now search for the type1 in the access path of ref2. This
would be a common base for doing offset based disambiguation on.
This however only makes sense if type2 is big enough to hold type1. */
int cmp_outer = compare_type_sizes (type2, type1);
/* If type2 is big enough to contain type1 walk its access path.
We also need to care of arrays at the end of structs that may extend
beyond the end of structure. If this occurs in the TBAA part of the
access path, we need to consider the increased type as well. */
if (cmp_outer >= 0
|| (end_struct_ref2
&& compare_type_sizes (TREE_TYPE (end_struct_ref2), type1) >= 0))
{
int res = aliasing_component_refs_walk (ref1, type1, base1,
offset1, max_size1,
end_struct_ref1,
ref2, base2, offset2, max_size2,
&maybe_match);
if (res != -1)
return res;
}
/* If we didn't find a common base, try the other way around. */
if (cmp_outer <= 0
|| (end_struct_ref1
&& compare_type_sizes (TREE_TYPE (end_struct_ref1), type1) <= 0))
{
int res = aliasing_component_refs_walk (ref2, type2, base2,
offset2, max_size2,
end_struct_ref2,
ref1, base1, offset1, max_size1,
&maybe_match);
if (res != -1)
return res;
}
/* In the following code we make an assumption that the types in access
paths do not overlap and thus accesses alias only if one path can be
continuation of another. If we was not able to decide about equivalence,
we need to give up. */
if (maybe_match)
{
if (!nonoverlapping_component_refs_p (ref1, ref2))
{
++alias_stats.aliasing_component_refs_p_may_alias;
return true;
}
++alias_stats.aliasing_component_refs_p_no_alias;
return false;
}
if (access_path_may_continue_p (TREE_TYPE (ref1), end_struct_past_end1,
ref1_alias_set,
type2, end_struct_ref2,
base2_alias_set)
|| access_path_may_continue_p (TREE_TYPE (ref2), end_struct_past_end2,
ref2_alias_set,
type1, end_struct_ref1,
base1_alias_set))
{
++alias_stats.aliasing_component_refs_p_may_alias;
return true;
}
++alias_stats.aliasing_component_refs_p_no_alias;
return false;
}
/* FIELD1 and FIELD2 are two fields of component refs. We assume
that bases of both component refs are either equivalent or nonoverlapping.
We do not assume that the containers of FIELD1 and FIELD2 are of the
same type or size.
Return 0 in case the base address of component_refs are same then
FIELD1 and FIELD2 have same address. Note that FIELD1 and FIELD2
may not be of same type or size.
Return 1 if FIELD1 and FIELD2 are non-overlapping.
Return -1 otherwise.
Main difference between 0 and -1 is to let
nonoverlapping_component_refs_since_match_p discover the semantically
equivalent part of the access path.
Note that this function is used even with -fno-strict-aliasing
and makes use of no TBAA assumptions. */
static int
nonoverlapping_component_refs_p_1 (const_tree field1, const_tree field2)
{
/* If both fields are of the same type, we could save hard work of
comparing offsets. */
tree type1 = DECL_CONTEXT (field1);
tree type2 = DECL_CONTEXT (field2);
if (TREE_CODE (type1) == RECORD_TYPE
&& DECL_BIT_FIELD_REPRESENTATIVE (field1))
field1 = DECL_BIT_FIELD_REPRESENTATIVE (field1);
if (TREE_CODE (type2) == RECORD_TYPE
&& DECL_BIT_FIELD_REPRESENTATIVE (field2))
field2 = DECL_BIT_FIELD_REPRESENTATIVE (field2);
/* ??? Bitfields can overlap at RTL level so punt on them.
FIXME: RTL expansion should be fixed by adjusting the access path
when producing MEM_ATTRs for MEMs which are wider than
the bitfields similarly as done in set_mem_attrs_minus_bitpos. */
if (DECL_BIT_FIELD (field1) && DECL_BIT_FIELD (field2))
return -1;
/* Assume that different FIELD_DECLs never overlap within a RECORD_TYPE. */
if (type1 == type2 && TREE_CODE (type1) == RECORD_TYPE)
return field1 != field2;
/* In common case the offsets and bit offsets will be the same.
However if frontends do not agree on the alignment, they may be
different even if they actually represent same address.
Try the common case first and if that fails calcualte the
actual bit offset. */
if (tree_int_cst_equal (DECL_FIELD_OFFSET (field1),
DECL_FIELD_OFFSET (field2))
&& tree_int_cst_equal (DECL_FIELD_BIT_OFFSET (field1),
DECL_FIELD_BIT_OFFSET (field2)))
return 0;
/* Note that it may be possible to use component_ref_field_offset
which would provide offsets as trees. However constructing and folding
trees is expensive and does not seem to be worth the compile time
cost. */
poly_uint64 offset1, offset2;
poly_uint64 bit_offset1, bit_offset2;
if (poly_int_tree_p (DECL_FIELD_OFFSET (field1), &offset1)
&& poly_int_tree_p (DECL_FIELD_OFFSET (field2), &offset2)
&& poly_int_tree_p (DECL_FIELD_BIT_OFFSET (field1), &bit_offset1)
&& poly_int_tree_p (DECL_FIELD_BIT_OFFSET (field2), &bit_offset2))
{
offset1 = (offset1 << LOG2_BITS_PER_UNIT) + bit_offset1;
offset2 = (offset2 << LOG2_BITS_PER_UNIT) + bit_offset2;
if (known_eq (offset1, offset2))
return 0;
poly_uint64 size1, size2;
if (poly_int_tree_p (DECL_SIZE (field1), &size1)
&& poly_int_tree_p (DECL_SIZE (field2), &size2)
&& !ranges_maybe_overlap_p (offset1, size1, offset2, size2))
return 1;
}
/* Resort to slower overlap checking by looking for matching types in
the middle of access path. */
return -1;
}
/* Return low bound of array. Do not produce new trees
and thus do not care about particular type of integer constant
and placeholder exprs. */
static tree
cheap_array_ref_low_bound (tree ref)
{
tree domain_type = TYPE_DOMAIN (TREE_TYPE (TREE_OPERAND (ref, 0)));
/* Avoid expensive array_ref_low_bound.
low bound is either stored in operand2, or it is TYPE_MIN_VALUE of domain
type or it is zero. */
if (TREE_OPERAND (ref, 2))
return TREE_OPERAND (ref, 2);
else if (domain_type && TYPE_MIN_VALUE (domain_type))
return TYPE_MIN_VALUE (domain_type);
else
return integer_zero_node;
}
/* REF1 and REF2 are ARRAY_REFs with either same base address or which are
completely disjoint.
Return 1 if the refs are non-overlapping.
Return 0 if they are possibly overlapping but if so the overlap again
starts on the same address.
Return -1 otherwise. */
int
nonoverlapping_array_refs_p (tree ref1, tree ref2)
{
tree index1 = TREE_OPERAND (ref1, 1);
tree index2 = TREE_OPERAND (ref2, 1);
tree low_bound1 = cheap_array_ref_low_bound (ref1);
tree low_bound2 = cheap_array_ref_low_bound (ref2);
/* Handle zero offsets first: we do not need to match type size in this
case. */
if (operand_equal_p (index1, low_bound1, 0)
&& operand_equal_p (index2, low_bound2, 0))
return 0;
/* If type sizes are different, give up.
Avoid expensive array_ref_element_size.
If operand 3 is present it denotes size in the alignmnet units.
Otherwise size is TYPE_SIZE of the element type.
Handle only common cases where types are of the same "kind". */
if ((TREE_OPERAND (ref1, 3) == NULL) != (TREE_OPERAND (ref2, 3) == NULL))
return -1;
tree elmt_type1 = TREE_TYPE (TREE_TYPE (TREE_OPERAND (ref1, 0)));
tree elmt_type2 = TREE_TYPE (TREE_TYPE (TREE_OPERAND (ref2, 0)));
if (TREE_OPERAND (ref1, 3))
{
if (TYPE_ALIGN (elmt_type1) != TYPE_ALIGN (elmt_type2)
|| !operand_equal_p (TREE_OPERAND (ref1, 3),
TREE_OPERAND (ref2, 3), 0))
return -1;
}
else
{
if (!operand_equal_p (TYPE_SIZE_UNIT (elmt_type1),
TYPE_SIZE_UNIT (elmt_type2), 0))
return -1;
}
/* Since we know that type sizes are the same, there is no need to return
-1 after this point. Partial overlap can not be introduced. */
/* We may need to fold trees in this case.
TODO: Handle integer constant case at least. */
if (!operand_equal_p (low_bound1, low_bound2, 0))
return 0;
if (TREE_CODE (index1) == INTEGER_CST && TREE_CODE (index2) == INTEGER_CST)
{
if (tree_int_cst_equal (index1, index2))
return 0;
return 1;
}
/* TODO: We can use VRP to further disambiguate here. */
return 0;
}
/* Try to disambiguate REF1 and REF2 under the assumption that MATCH1 and
MATCH2 either point to the same address or are disjoint.
MATCH1 and MATCH2 are assumed to be ref in the access path of REF1 and REF2
respectively or NULL in the case we established equivalence of bases.
If PARTIAL_OVERLAP is true assume that the toplevel arrays may actually
overlap by exact multiply of their element size.
This test works by matching the initial segment of the access path
and does not rely on TBAA thus is safe for !flag_strict_aliasing if
match was determined without use of TBAA oracle.
Return 1 if we can determine that component references REF1 and REF2,
that are within a common DECL, cannot overlap.
Return 0 if paths are same and thus there is nothing to disambiguate more
(i.e. there is must alias assuming there is must alias between MATCH1 and
MATCH2)
Return -1 if we can not determine 0 or 1 - this happens when we met
non-matching types was met in the path.
In this case it may make sense to continue by other disambiguation
oracles. */
static int
nonoverlapping_refs_since_match_p (tree match1, tree ref1,
tree match2, tree ref2,
bool partial_overlap)
{
int ntbaa1 = 0, ntbaa2 = 0;
/* Early return if there are no references to match, we do not need
to walk the access paths.
Do not consider this as may-alias for stats - it is more useful
to have information how many disambiguations happened provided that
the query was meaningful. */
if (match1 == ref1 || !handled_component_p (ref1)
|| match2 == ref2 || !handled_component_p (ref2))
return -1;
auto_vec<tree, 16> component_refs1;
auto_vec<tree, 16> component_refs2;
/* Create the stack of handled components for REF1. */
while (handled_component_p (ref1) && ref1 != match1)
{
/* We use TBAA only to re-synchronize after mismatched refs. So we
do not need to truncate access path after TBAA part ends. */
if (ends_tbaa_access_path_p (ref1))
ntbaa1 = 0;
else
ntbaa1++;
component_refs1.safe_push (ref1);
ref1 = TREE_OPERAND (ref1, 0);
}
/* Create the stack of handled components for REF2. */
while (handled_component_p (ref2) && ref2 != match2)
{
if (ends_tbaa_access_path_p (ref2))
ntbaa2 = 0;
else
ntbaa2++;
component_refs2.safe_push (ref2);
ref2 = TREE_OPERAND (ref2, 0);
}
if (!flag_strict_aliasing)
{
ntbaa1 = 0;
ntbaa2 = 0;
}
bool mem_ref1 = TREE_CODE (ref1) == MEM_REF && ref1 != match1;
bool mem_ref2 = TREE_CODE (ref2) == MEM_REF && ref2 != match2;
/* If only one of access path starts with MEM_REF check that offset is 0
so the addresses stays the same after stripping it.
TODO: In this case we may walk the other access path until we get same
offset.
If both starts with MEM_REF, offset has to be same. */
if ((mem_ref1 && !mem_ref2 && !integer_zerop (TREE_OPERAND (ref1, 1)))
|| (mem_ref2 && !mem_ref1 && !integer_zerop (TREE_OPERAND (ref2, 1)))
|| (mem_ref1 && mem_ref2
&& !tree_int_cst_equal (TREE_OPERAND (ref1, 1),
TREE_OPERAND (ref2, 1))))
{
++alias_stats.nonoverlapping_refs_since_match_p_may_alias;
return -1;
}
/* TARGET_MEM_REF are never wrapped in handled components, so we do not need
to handle them here at all. */
gcc_checking_assert (TREE_CODE (ref1) != TARGET_MEM_REF
&& TREE_CODE (ref2) != TARGET_MEM_REF);
/* Pop the stacks in parallel and examine the COMPONENT_REFs of the same
rank. This is sufficient because we start from the same DECL and you
cannot reference several fields at a time with COMPONENT_REFs (unlike
with ARRAY_RANGE_REFs for arrays) so you always need the same number
of them to access a sub-component, unless you're in a union, in which
case the return value will precisely be false. */
while (true)
{
/* Track if we seen unmatched ref with non-zero offset. In this case
we must look for partial overlaps. */
bool seen_unmatched_ref_p = false;
/* First match ARRAY_REFs an try to disambiguate. */
if (!component_refs1.is_empty ()
&& !component_refs2.is_empty ())
{
unsigned int narray_refs1=0, narray_refs2=0;
/* We generally assume that both access paths starts by same sequence
of refs. However if number of array refs is not in sync, try
to recover and pop elts until number match. This helps the case
where one access path starts by array and other by element. */
for (narray_refs1 = 0; narray_refs1 < component_refs1.length ();
narray_refs1++)
if (TREE_CODE (component_refs1 [component_refs1.length()
- 1 - narray_refs1]) != ARRAY_REF)
break;
for (narray_refs2 = 0; narray_refs2 < component_refs2.length ();
narray_refs2++)
if (TREE_CODE (component_refs2 [component_refs2.length()
- 1 - narray_refs2]) != ARRAY_REF)
break;
for (; narray_refs1 > narray_refs2; narray_refs1--)
{
ref1 = component_refs1.pop ();
ntbaa1--;
/* If index is non-zero we need to check whether the reference
does not break the main invariant that bases are either
disjoint or equal. Consider the example:
unsigned char out[][1];
out[1]="a";
out[i][0];
Here bases out and out are same, but after removing the
[i] index, this invariant no longer holds, because
out[i] points to the middle of array out.
TODO: If size of type of the skipped reference is an integer
multiply of the size of type of the other reference this
invariant can be verified, but even then it is not completely
safe with !flag_strict_aliasing if the other reference contains
unbounded array accesses.
See */
if (!operand_equal_p (TREE_OPERAND (ref1, 1),
cheap_array_ref_low_bound (ref1), 0))
return 0;
}
for (; narray_refs2 > narray_refs1; narray_refs2--)
{
ref2 = component_refs2.pop ();
ntbaa2--;
if (!operand_equal_p (TREE_OPERAND (ref2, 1),
cheap_array_ref_low_bound (ref2), 0))
return 0;
}
/* Try to disambiguate matched arrays. */
for (unsigned int i = 0; i < narray_refs1; i++)
{
int cmp = nonoverlapping_array_refs_p (component_refs1.pop (),
component_refs2.pop ());
ntbaa1--;
ntbaa2--;
if (cmp == 1 && !partial_overlap)
{
++alias_stats
.nonoverlapping_refs_since_match_p_no_alias;
return 1;
}
if (cmp == -1)
{
seen_unmatched_ref_p = true;
/* We can not maintain the invariant that bases are either
same or completely disjoint. However we can still recover
from type based alias analysis if we reach references to
same sizes. We do not attempt to match array sizes, so
just finish array walking and look for component refs. */
if (ntbaa1 < 0 || ntbaa2 < 0)
{
++alias_stats.nonoverlapping_refs_since_match_p_may_alias;
return -1;
}
for (i++; i < narray_refs1; i++)
{
component_refs1.pop ();
component_refs2.pop ();
ntbaa1--;
ntbaa2--;
}
break;
}
partial_overlap = false;
}
}
/* Next look for component_refs. */
do
{
if (component_refs1.is_empty ())
{
++alias_stats
.nonoverlapping_refs_since_match_p_must_overlap;
return 0;
}
ref1 = component_refs1.pop ();
ntbaa1--;
if (TREE_CODE (ref1) != COMPONENT_REF)
{
seen_unmatched_ref_p = true;
if (ntbaa1 < 0 || ntbaa2 < 0)
{
++alias_stats.nonoverlapping_refs_since_match_p_may_alias;
return -1;
}
}
}
while (!RECORD_OR_UNION_TYPE_P (TREE_TYPE (TREE_OPERAND (ref1, 0))));
do
{
if (component_refs2.is_empty ())
{
++alias_stats
.nonoverlapping_refs_since_match_p_must_overlap;
return 0;
}
ref2 = component_refs2.pop ();
ntbaa2--;
if (TREE_CODE (ref2) != COMPONENT_REF)
{
if (ntbaa1 < 0 || ntbaa2 < 0)
{
++alias_stats.nonoverlapping_refs_since_match_p_may_alias;
return -1;
}
seen_unmatched_ref_p = true;
}
}
while (!RECORD_OR_UNION_TYPE_P (TREE_TYPE (TREE_OPERAND (ref2, 0))));
/* BIT_FIELD_REF and VIEW_CONVERT_EXPR are taken off the vectors
earlier. */
gcc_checking_assert (TREE_CODE (ref1) == COMPONENT_REF
&& TREE_CODE (ref2) == COMPONENT_REF);
tree field1 = TREE_OPERAND (ref1, 1);
tree field2 = TREE_OPERAND (ref2, 1);
/* ??? We cannot simply use the type of operand #0 of the refs here
as the Fortran compiler smuggles type punning into COMPONENT_REFs
for common blocks instead of using unions like everyone else. */
tree type1 = DECL_CONTEXT (field1);
tree type2 = DECL_CONTEXT (field2);
partial_overlap = false;
/* If we skipped array refs on type of different sizes, we can
no longer be sure that there are not partial overlaps. */
if (seen_unmatched_ref_p && ntbaa1 >= 0 && ntbaa2 >= 0
&& !operand_equal_p (TYPE_SIZE (type1), TYPE_SIZE (type2), 0))
{
++alias_stats
.nonoverlapping_refs_since_match_p_may_alias;
return -1;
}
int cmp = nonoverlapping_component_refs_p_1 (field1, field2);
if (cmp == -1)
{
++alias_stats
.nonoverlapping_refs_since_match_p_may_alias;
return -1;
}
else if (cmp == 1)
{
++alias_stats
.nonoverlapping_refs_since_match_p_no_alias;
return 1;
}
}
++alias_stats.nonoverlapping_refs_since_match_p_must_overlap;
return 0;
}
/* Return TYPE_UID which can be used to match record types we consider
same for TBAA purposes. */
static inline int
ncr_type_uid (const_tree field)
{
/* ??? We cannot simply use the type of operand #0 of the refs here
as the Fortran compiler smuggles type punning into COMPONENT_REFs
for common blocks instead of using unions like everyone else. */
tree type = DECL_FIELD_CONTEXT (field);
/* With LTO types considered same_type_for_tbaa_p
from different translation unit may not have same
main variant. They however have same TYPE_CANONICAL. */
if (TYPE_CANONICAL (type))
return TYPE_UID (TYPE_CANONICAL (type));
return TYPE_UID (type);
}
/* qsort compare function to sort FIELD_DECLs after their
DECL_FIELD_CONTEXT TYPE_UID. */
static inline int
ncr_compar (const void *field1_, const void *field2_)
{
const_tree field1 = *(const_tree *) const_cast <void *>(field1_);
const_tree field2 = *(const_tree *) const_cast <void *>(field2_);
unsigned int uid1 = ncr_type_uid (field1);
unsigned int uid2 = ncr_type_uid (field2);
if (uid1 < uid2)
return -1;
else if (uid1 > uid2)
return 1;
return 0;
}
/* Return true if we can determine that the fields referenced cannot
overlap for any pair of objects. This relies on TBAA. */
static bool
nonoverlapping_component_refs_p (const_tree x, const_tree y)
{
/* Early return if we have nothing to do.
Do not consider this as may-alias for stats - it is more useful
to have information how many disambiguations happened provided that
the query was meaningful. */
if (!flag_strict_aliasing
|| !x || !y
|| !handled_component_p (x)
|| !handled_component_p (y))
return false;
auto_vec<const_tree, 16> fieldsx;
while (handled_component_p (x))
{
if (TREE_CODE (x) == COMPONENT_REF)
{
tree field = TREE_OPERAND (x, 1);
tree type = DECL_FIELD_CONTEXT (field);
if (TREE_CODE (type) == RECORD_TYPE)
fieldsx.safe_push (field);
}
else if (ends_tbaa_access_path_p (x))
fieldsx.truncate (0);
x = TREE_OPERAND (x, 0);
}
if (fieldsx.length () == 0)
return false;
auto_vec<const_tree, 16> fieldsy;
while (handled_component_p (y))
{
if (TREE_CODE (y) == COMPONENT_REF)
{
tree field = TREE_OPERAND (y, 1);
tree type = DECL_FIELD_CONTEXT (field);
if (TREE_CODE (type) == RECORD_TYPE)
fieldsy.safe_push (TREE_OPERAND (y, 1));
}
else if (ends_tbaa_access_path_p (y))
fieldsy.truncate (0);
y = TREE_OPERAND (y, 0);
}
if (fieldsy.length () == 0)
{
++alias_stats.nonoverlapping_component_refs_p_may_alias;
return false;
}
/* Most common case first. */
if (fieldsx.length () == 1
&& fieldsy.length () == 1)
{
if (same_type_for_tbaa (DECL_FIELD_CONTEXT (fieldsx[0]),
DECL_FIELD_CONTEXT (fieldsy[0])) == 1
&& nonoverlapping_component_refs_p_1 (fieldsx[0], fieldsy[0]) == 1)
{
++alias_stats.nonoverlapping_component_refs_p_no_alias;
return true;
}
else
{
++alias_stats.nonoverlapping_component_refs_p_may_alias;
return false;
}
}
if (fieldsx.length () == 2)
{
if (ncr_compar (&fieldsx[0], &fieldsx[1]) == 1)
std::swap (fieldsx[0], fieldsx[1]);
}
else
fieldsx.qsort (ncr_compar);
if (fieldsy.length () == 2)
{
if (ncr_compar (&fieldsy[0], &fieldsy[1]) == 1)
std::swap (fieldsy[0], fieldsy[1]);
}
else
fieldsy.qsort (ncr_compar);
unsigned i = 0, j = 0;
do
{
const_tree fieldx = fieldsx[i];
const_tree fieldy = fieldsy[j];
/* We're left with accessing different fields of a structure,
no possible overlap. */
if (same_type_for_tbaa (DECL_FIELD_CONTEXT (fieldx),
DECL_FIELD_CONTEXT (fieldy)) == 1
&& nonoverlapping_component_refs_p_1 (fieldx, fieldy) == 1)
{
++alias_stats.nonoverlapping_component_refs_p_no_alias;
return true;
}
if (ncr_type_uid (fieldx) < ncr_type_uid (fieldy))
{
i++;
if (i == fieldsx.length ())
break;
}
else
{
j++;
if (j == fieldsy.length ())
break;
}
}
while (1);
++alias_stats.nonoverlapping_component_refs_p_may_alias;
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. REF1 and REF2
if non-NULL are the complete memory reference trees. */
static bool
decl_refs_may_alias_p (tree ref1, tree base1,
poly_int64 offset1, poly_int64 max_size1,
poly_int64 size1,
tree ref2, tree base2,
poly_int64 offset2, poly_int64 max_size2,
poly_int64 size2)
{
gcc_checking_assert (DECL_P (base1) && DECL_P (base2));
/* If both references are based on different variables, they cannot alias. */
if (compare_base_decls (base1, base2) == 0)
return false;
/* If both references are based on the same variable, they cannot alias if
the accesses do not overlap. */
if (!ranges_maybe_overlap_p (offset1, max_size1, offset2, max_size2))
return false;
/* If there is must alias, there is no use disambiguating further. */
if (known_eq (size1, max_size1) && known_eq (size2, max_size2))
return true;
/* For components with variable position, the above test isn't sufficient,
so we disambiguate component references manually. */
if (ref1 && ref2
&& handled_component_p (ref1) && handled_component_p (ref2)
&& nonoverlapping_refs_since_match_p (NULL, ref1, NULL, ref2, false) == 1)
return false;
return true;
}
/* Return true if access with BASE is view converted.
Base must not be stripped from inner MEM_REF (&decl)
which is done by ao_ref_base and thus one extra walk
of handled components is needed. */
static bool
view_converted_memref_p (tree base)
{
if (TREE_CODE (base) != MEM_REF && TREE_CODE (base) != TARGET_MEM_REF)
return false;
return same_type_for_tbaa (TREE_TYPE (base),
TREE_TYPE (TREE_OPERAND (base, 1))) != 1;
}
/* 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. */
static bool
indirect_ref_may_alias_decl_p (tree ref1 ATTRIBUTE_UNUSED, tree base1,
poly_int64 offset1, poly_int64 max_size1,
poly_int64 size1,
alias_set_type ref1_alias_set,
alias_set_type base1_alias_set,
tree ref2 ATTRIBUTE_UNUSED, tree base2,
poly_int64 offset2, poly_int64 max_size2,
poly_int64 size2,
alias_set_type ref2_alias_set,
alias_set_type base2_alias_set, bool tbaa_p)
{
tree ptr1;
tree ptrtype1, dbase2;
gcc_checking_assert ((TREE_CODE (base1) == MEM_REF
|| TREE_CODE (base1) == TARGET_MEM_REF)
&& DECL_P (base2));
ptr1 = TREE_OPERAND (base1, 0);
poly_offset_int moff = mem_ref_offset (base1) << LOG2_BITS_PER_UNIT;
/* 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).
??? IVOPTs creates bases that do not honor this restriction,
so do not apply this optimization for TARGET_MEM_REFs. */
if (TREE_CODE (base1) != TARGET_MEM_REF
&& !ranges_maybe_overlap_p (offset1 + moff, -1, offset2, max_size2))
return false;
/* If the pointer based access is bigger than the variable they cannot
alias. This is similar to the check below where we use TBAA to
increase the size of the pointer based access based on the dynamic
type of a containing object we can infer from it. */
poly_int64 dsize2;
if (known_size_p (size1)
&& poly_int_tree_p (DECL_SIZE (base2), &dsize2)
&& known_lt (dsize2, size1))
return false;
/* They also cannot alias if the pointer may not point to the decl. */
if (!ptr_deref_may_alias_decl_p (ptr1, base2))
return false;
/* Disambiguations that rely on strict aliasing rules follow. */
if (!flag_strict_aliasing || !tbaa_p)
return true;
/* If the alias set for a pointer access is zero all bets are off. */
if (base1_alias_set == 0 || base2_alias_set == 0)
return true;
/* When we are trying to disambiguate an access with a pointer dereference
as base versus one with a decl as base we can use both the size
of the decl and its dynamic type for extra disambiguation.
??? We do not know anything about the dynamic type of the decl
other than that its alias-set contains base2_alias_set as a subset
which does not help us here. */
/* As we know nothing useful about the dynamic type of the decl just
use the usual conflict check rather than a subset test.
??? We could introduce -fvery-strict-aliasing when the language
does not allow decls to have a dynamic type that differs from their
static type. Then we can check
!alias_set_subset_of (base1_alias_set, base2_alias_set) instead. */
if (base1_alias_set != base2_alias_set
&& !alias_sets_conflict_p (base1_alias_set, base2_alias_set))
return false;
ptrtype1 = TREE_TYPE (TREE_OPERAND (base1, 1));
/* If the size of the access relevant for TBAA through the pointer
is bigger than the size of the decl we can't possibly access the
decl via that pointer. */
if (/* ??? This in turn may run afoul when a decl of type T which is
a member of union type U is accessed through a pointer to
type U and sizeof T is smaller than sizeof U. */
TREE_CODE (TREE_TYPE (ptrtype1)) != UNION_TYPE
&& TREE_CODE (TREE_TYPE (ptrtype1)) != QUAL_UNION_TYPE
&& compare_sizes (DECL_SIZE (base2),
TYPE_SIZE (TREE_TYPE (ptrtype1))) < 0)
return false;
if (!ref2)
return true;
/* If the decl is accessed via a MEM_REF, reconstruct the base
we can use for TBAA and an appropriately adjusted offset. */
dbase2 = ref2;
while (handled_component_p (dbase2))
dbase2 = TREE_OPERAND (dbase2, 0);
poly_int64 doffset1 = offset1;
poly_offset_int doffset2 = offset2;
if (TREE_CODE (dbase2) == MEM_REF
|| TREE_CODE (dbase2) == TARGET_MEM_REF)
{
doffset2 -= mem_ref_offset (dbase2) << LOG2_BITS_PER_UNIT;
tree ptrtype2 = TREE_TYPE (TREE_OPERAND (dbase2, 1));
/* If second reference is view-converted, give up now. */
if (same_type_for_tbaa (TREE_TYPE (dbase2), TREE_TYPE (ptrtype2)) != 1)
return true;
}
/* If first reference is view-converted, give up now. */
if (same_type_for_tbaa (TREE_TYPE (base1), TREE_TYPE (ptrtype1)) != 1)
return true;
/* 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.
For MEM_REFs we require that the component-ref offset we computed
is relative to the start of the type which we ensure by
comparing rvalue and access type and disregarding the constant
pointer offset.
But avoid treating variable length arrays as "objects", instead assume they
can overlap by an exact multiple of their element size.
See gcc.dg/torture/alias-2.c. */
if (((TREE_CODE (base1) != TARGET_MEM_REF
|| (!TMR_INDEX (base1) && !TMR_INDEX2 (base1)))
&& (TREE_CODE (dbase2) != TARGET_MEM_REF
|| (!TMR_INDEX (dbase2) && !TMR_INDEX2 (dbase2))))
&& same_type_for_tbaa (TREE_TYPE (base1), TREE_TYPE (dbase2)) == 1)
{
bool partial_overlap = (TREE_CODE (TREE_TYPE (base1)) == ARRAY_TYPE
&& (TYPE_SIZE (TREE_TYPE (base1))
&& TREE_CODE (TYPE_SIZE (TREE_TYPE (base1)))
!= INTEGER_CST));
if (!partial_overlap
&& !ranges_maybe_overlap_p (doffset1, max_size1, doffset2, max_size2))
return false;
if (!ref1 || !ref2
/* If there is must alias, there is no use disambiguating further. */
|| (!partial_overlap
&& known_eq (size1, max_size1) && known_eq (size2, max_size2)))
return true;
int res = nonoverlapping_refs_since_match_p (base1, ref1, base2, ref2,
partial_overlap);
if (res == -1)
return !nonoverlapping_component_refs_p (ref1, ref2);
return !res;
}
/* Do access-path based disambiguation. */
if (ref1 && ref2
&& (handled_component_p (ref1) || handled_component_p (ref2)))
return aliasing_component_refs_p (ref1,
ref1_alias_set, base1_alias_set,
offset1, max_size1,
ref2,
ref2_alias_set, base2_alias_set,
offset2, max_size2);
return true;
}
/* 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. */
static bool
indirect_refs_may_alias_p (tree ref1 ATTRIBUTE_UNUSED, tree base1,
poly_int64 offset1, poly_int64 max_size1,
poly_int64 size1,
alias_set_type ref1_alias_set,
alias_set_type base1_alias_set,
tree ref2 ATTRIBUTE_UNUSED, tree base2,
poly_int64 offset2, poly_int64 max_size2,
poly_int64 size2,
alias_set_type ref2_alias_set,
alias_set_type base2_alias_set, bool tbaa_p)
{
tree ptr1;
tree ptr2;
tree ptrtype1, ptrtype2;
gcc_checking_assert ((TREE_CODE (base1) == MEM_REF
|| TREE_CODE (base1) == TARGET_MEM_REF)
&& (TREE_CODE (base2) == MEM_REF
|| TREE_CODE (base2) == TARGET_MEM_REF));
ptr1 = TREE_OPERAND (base1, 0);
ptr2 = TREE_OPERAND (base2, 0);
/* 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 ((!cfun || gimple_in_ssa_p (cfun))
&& operand_equal_p (ptr1, ptr2, 0)
&& (((TREE_CODE (base1) != TARGET_MEM_REF
|| (!TMR_INDEX (base1) && !TMR_INDEX2 (base1)))
&& (TREE_CODE (base2) != TARGET_MEM_REF
|| (!TMR_INDEX (base2) && !TMR_INDEX2 (base2))))
|| (TREE_CODE (base1) == TARGET_MEM_REF
&& TREE_CODE (base2) == TARGET_MEM_REF
&& (TMR_STEP (base1) == TMR_STEP (base2)
|| (TMR_STEP (base1) && TMR_STEP (base2)
&& operand_equal_p (TMR_STEP (base1),
TMR_STEP (base2), 0)))
&& (TMR_INDEX (base1) == TMR_INDEX (base2)
|| (TMR_INDEX (base1) && TMR_INDEX (base2)
&& operand_equal_p (TMR_INDEX (base1),
TMR_INDEX (base2), 0)))
&& (TMR_INDEX2 (base1) == TMR_INDEX2 (base2)
|| (TMR_INDEX2 (base1) && TMR_INDEX2 (base2)
&& operand_equal_p (TMR_INDEX2 (base1),
TMR_INDEX2 (base2), 0))))))
{
poly_offset_int moff1 = mem_ref_offset (base1) << LOG2_BITS_PER_UNIT;
poly_offset_int moff2 = mem_ref_offset (base2) << LOG2_BITS_PER_UNIT;
if (!ranges_maybe_overlap_p (offset1 + moff1, max_size1,
offset2 + moff2, max_size2))
return false;
/* If there is must alias, there is no use disambiguating further. */
if (known_eq (size1, max_size1) && known_eq (size2, max_size2))
return true;
if (ref1 && ref2)
{
int res = nonoverlapping_refs_since_match_p (NULL, ref1, NULL, ref2,
false);
if (res != -1)
return !res;
}
}
if (!ptr_derefs_may_alias_p (ptr1, ptr2))
return false;
/* Disambiguations that rely on strict aliasing rules follow. */
if (!flag_strict_aliasing || !tbaa_p)
return true;
ptrtype1 = TREE_TYPE (TREE_OPERAND (base1, 1));
ptrtype2 = TREE_TYPE (TREE_OPERAND (base2, 1));
/* If the alias set for a pointer access is zero all bets are off. */
if (base1_alias_set == 0
|| base2_alias_set == 0)
return true;
/* Do type-based disambiguation. */
if (base1_alias_set != base2_alias_set
&& !alias_sets_conflict_p (base1_alias_set, base2_alias_set))
return false;
/* If either reference is view-converted, give up now. */
if (same_type_for_tbaa (TREE_TYPE (base1), TREE_TYPE (ptrtype1)) != 1
|| same_type_for_tbaa (TREE_TYPE (base2), TREE_TYPE (ptrtype2)) != 1)
return true;
/* 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 ((TREE_CODE (base1) != TARGET_MEM_REF
|| (!TMR_INDEX (base1) && !TMR_INDEX2 (base1)))
&& (TREE_CODE (base2) != TARGET_MEM_REF
|| (!TMR_INDEX (base2) && !TMR_INDEX2 (base2)))
&& same_type_for_tbaa (TREE_TYPE (ptrtype1),
TREE_TYPE (ptrtype2)) == 1)
{
/* But avoid treating arrays as "objects", instead assume they
can overlap by an exact multiple of their element size.
See gcc.dg/torture/alias-2.c. */
bool partial_overlap = TREE_CODE (TREE_TYPE (ptrtype1)) == ARRAY_TYPE;
if (!partial_overlap
&& !ranges_maybe_overlap_p (offset1, max_size1, offset2, max_size2))
return false;
if (!ref1 || !ref2
|| (!partial_overlap
&& known_eq (size1, max_size1) && known_eq (size2, max_size2)))
return true;
int res = nonoverlapping_refs_since_match_p (base1, ref1, base2, ref2,
partial_overlap);
if (res == -1)
return !nonoverlapping_component_refs_p (ref1, ref2);
return !res;
}
/* Do access-path based disambiguation. */
if (ref1 && ref2
&& (handled_component_p (ref1) || handled_component_p (ref2)))
return aliasing_component_refs_p (ref1,
ref1_alias_set, base1_alias_set,
offset1, max_size1,
ref2,
ref2_alias_set, base2_alias_set,
offset2, max_size2);
return true;
}
/* Return true, if the two memory references REF1 and REF2 may alias. */
static bool
refs_may_alias_p_2 (ao_ref *ref1, ao_ref *ref2, bool tbaa_p)
{
tree base1, base2;
poly_int64 offset1 = 0, offset2 = 0;
poly_int64 max_size1 = -1, max_size2 = -1;
bool var1_p, var2_p, ind1_p, ind2_p;
gcc_checking_assert ((!ref1->ref
|| TREE_CODE (ref1->ref) == SSA_NAME
|| DECL_P (ref1->ref)
|| TREE_CODE (ref1->ref) == STRING_CST
|| handled_component_p (ref1->ref)
|| TREE_CODE (ref1->ref) == MEM_REF
|| TREE_CODE (ref1->ref) == TARGET_MEM_REF
|| TREE_CODE (ref1->ref) == WITH_SIZE_EXPR)
&& (!ref2->ref
|| TREE_CODE (ref2->ref) == SSA_NAME
|| DECL_P (ref2->ref)
|| TREE_CODE (ref2->ref) == STRING_CST
|| handled_component_p (ref2->ref)
|| TREE_CODE (ref2->ref) == MEM_REF
|| TREE_CODE (ref2->ref) == TARGET_MEM_REF
|| TREE_CODE (ref2->ref) == WITH_SIZE_EXPR));
/* Decompose the references into their base objects and the access. */
base1 = ao_ref_base (ref1);
offset1 = ref1->offset;
max_size1 = ref1->max_size;
base2 = ao_ref_base (ref2);
offset2 = ref2->offset;
max_size2 = ref2->max_size;
/* 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 (base1) == CONST_DECL
|| TREE_CODE (base1) == CONSTRUCTOR
|| TREE_CODE (base1) == ADDR_EXPR
|| CONSTANT_CLASS_P (base1)
|| TREE_CODE (base2) == SSA_NAME
|| TREE_CODE (base2) == CONST_DECL
|| TREE_CODE (base2) == CONSTRUCTOR
|| TREE_CODE (base2) == ADDR_EXPR
|| CONSTANT_CLASS_P (base2))
return false;
/* We can end up referring to code via function and label decls.
As we likely do not properly track code aliases conservatively
bail out. */
if (TREE_CODE (base1) == FUNCTION_DECL
|| TREE_CODE (base1) == LABEL_DECL
|| TREE_CODE (base2) == FUNCTION_DECL
|| TREE_CODE (base2) == LABEL_DECL)
return true;
/* Two volatile accesses always conflict. */
if (ref1->volatile_p
&& ref2->volatile_p)
return true;
/* refN->ref may convey size information, do not confuse our workers
with that but strip it - ao_ref_base took it into account already. */
tree ref1ref = ref1->ref;
if (ref1ref && TREE_CODE (ref1ref) == WITH_SIZE_EXPR)
ref1ref = TREE_OPERAND (ref1ref, 0);
tree ref2ref = ref2->ref;
if (ref2ref && TREE_CODE (ref2ref) == WITH_SIZE_EXPR)
ref2ref = TREE_OPERAND (ref2ref, 0);
/* 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 = DECL_P (base1);
var2_p = DECL_P (base2);
if (var1_p && var2_p)
return decl_refs_may_alias_p (ref1ref, base1, offset1, max_size1,
ref1->size,
ref2ref, base2, offset2, max_size2,
ref2->size);
/* Handle restrict based accesses.
??? ao_ref_base strips inner MEM_REF [&decl], recover from that
here. */
tree rbase1 = base1;
tree rbase2 = base2;
if (var1_p)
{
rbase1 = ref1ref;
if (rbase1)
while (handled_component_p (rbase1))
rbase1 = TREE_OPERAND (rbase1, 0);
}
if (var2_p)
{
rbase2 = ref2ref;
if (rbase2)
while (handled_component_p (rbase2))
rbase2 = TREE_OPERAND (rbase2, 0);
}
if (rbase1 && rbase2
&& (TREE_CODE (base1) == MEM_REF || TREE_CODE (base1) == TARGET_MEM_REF)
&& (TREE_CODE (base2) == MEM_REF || TREE_CODE (base2) == TARGET_MEM_REF)
/* If the accesses are in the same restrict clique... */
&& MR_DEPENDENCE_CLIQUE (base1) == MR_DEPENDENCE_CLIQUE (base2)
/* But based on different pointers they do not alias. */
&& MR_DEPENDENCE_BASE (base1) != MR_DEPENDENCE_BASE (base2))
return false;
ind1_p = (TREE_CODE (base1) == MEM_REF
|| TREE_CODE (base1) == TARGET_MEM_REF);
ind2_p = (TREE_CODE (base2) == MEM_REF
|| TREE_CODE (base2) == TARGET_MEM_REF);
/* Canonicalize the pointer-vs-decl case. */
if (ind1_p && var2_p)
{
std::swap (offset1, offset2);
std::swap (max_size1, max_size2);
std::swap (base1, base2);
std::swap (ref1, ref2);
std::swap (ref1ref, ref2ref);
var1_p = true;
ind1_p = false;
var2_p = false;
ind2_p = true;
}
/* First defer to TBAA if possible. */
if (tbaa_p
&& flag_strict_aliasing
&& !alias_sets_conflict_p (ao_ref_alias_set (ref1),
ao_ref_alias_set (ref2)))
return false;
/* If the reference is based on a pointer that points to memory
that may not be written to then the other reference cannot possibly
clobber it. */
if ((TREE_CODE (TREE_OPERAND (base2, 0)) == SSA_NAME
&& SSA_NAME_POINTS_TO_READONLY_MEMORY (TREE_OPERAND (base2, 0)))
|| (ind1_p
&& TREE_CODE (TREE_OPERAND (base1, 0)) == SSA_NAME
&& SSA_NAME_POINTS_TO_READONLY_MEMORY (TREE_OPERAND (base1, 0))))
return false;
/* Dispatch to the pointer-vs-decl or pointer-vs-pointer disambiguators. */
if (var1_p && ind2_p)
return indirect_ref_may_alias_decl_p (ref2ref, base2,
offset2, max_size2, ref2->size,
ao_ref_alias_set (ref2),
ao_ref_base_alias_set (ref2),
ref1ref, base1,
offset1, max_size1, ref1->size,
ao_ref_alias_set (ref1),
ao_ref_base_alias_set (ref1),
tbaa_p);
else if (ind1_p && ind2_p)
return indirect_refs_may_alias_p (ref1ref, base1,
offset1, max_size1, ref1->size,
ao_ref_alias_set (ref1),
ao_ref_base_alias_set (ref1),
ref2ref, base2,
offset2, max_size2, ref2->size,
ao_ref_alias_set (ref2),
ao_ref_base_alias_set (ref2),
tbaa_p);
gcc_unreachable ();
}
/* Return true, if the two memory references REF1 and REF2 may alias
and update statistics. */
bool
refs_may_alias_p_1 (ao_ref *ref1, ao_ref *ref2, bool tbaa_p)
{
bool res = refs_may_alias_p_2 (ref1, ref2, tbaa_p);
if (res)
++alias_stats.refs_may_alias_p_may_alias;
else
++alias_stats.refs_may_alias_p_no_alias;
return res;
}
static bool
refs_may_alias_p (tree ref1, ao_ref *ref2, bool tbaa_p)
{
ao_ref r1;
ao_ref_init (&r1, ref1);
return refs_may_alias_p_1 (&r1, ref2, tbaa_p);
}
bool
refs_may_alias_p (tree ref1, tree ref2, bool tbaa_p)
{
ao_ref r1, r2;
ao_ref_init (&r1, ref1);
ao_ref_init (&r2, ref2);
return refs_may_alias_p_1 (&r1, &r2, tbaa_p);
}
/* Returns true if there is a anti-dependence for the STORE that
executes after the LOAD. */
bool
refs_anti_dependent_p (tree load, tree store)
{
ao_ref r1, r2;
ao_ref_init (&r1, load);
ao_ref_init (&r2, store);
return refs_may_alias_p_1 (&r1, &r2, false);
}
/* Returns true if there is a output dependence for the stores
STORE1 and STORE2. */
bool
refs_output_dependent_p (tree store1, tree store2)
{
ao_ref r1, r2;
ao_ref_init (&r1, store1);
ao_ref_init (&r2, store2);
return refs_may_alias_p_1 (&r1, &r2, false);
}
/* Returns true if and only if REF may alias any access stored in TT.
IF TBAA_P is true, use TBAA oracle. */
static bool
modref_may_conflict (const gimple *stmt,
modref_tree <alias_set_type> *tt, ao_ref *ref, bool tbaa_p)
{
alias_set_type base_set, ref_set;
modref_base_node <alias_set_type> *base_node;
modref_ref_node <alias_set_type> *ref_node;
size_t i, j, k;
if (tt->every_base)
return true;
if (!dbg_cnt (ipa_mod_ref))
return true;
base_set = ao_ref_base_alias_set (ref);
ref_set = ao_ref_alias_set (ref);
int num_tests = 0, max_tests = param_modref_max_tests;
FOR_EACH_VEC_SAFE_ELT (tt->bases, i, base_node)
{
if (tbaa_p && flag_strict_aliasing)
{
if (num_tests >= max_tests)
return true;
alias_stats.modref_tests++;
if (!alias_sets_conflict_p (base_set, base_node->base))
continue;
num_tests++;
}
if (base_node->every_ref)
return true;
FOR_EACH_VEC_SAFE_ELT (base_node->refs, j, ref_node)
{
/* Do not repeat same test as before. */
if ((ref_set != base_set || base_node->base != ref_node->ref)
&& tbaa_p && flag_strict_aliasing)
{
if (num_tests >= max_tests)
return true;
alias_stats.modref_tests++;
if (!alias_sets_conflict_p (ref_set, ref_node->ref))
continue;
num_tests++;
}
/* TBAA checks did not disambiguate, try to use base pointer, for
that we however need to have ref->ref or ref->base. */
if (ref_node->every_access || (!ref->ref && !ref->base))
return true;
modref_access_node *access_node;
FOR_EACH_VEC_SAFE_ELT (ref_node->accesses, k, access_node)
{
if (num_tests >= max_tests)
return true;
if (access_node->parm_index == -1
|| (unsigned)access_node->parm_index
>= gimple_call_num_args (stmt))
return true;
alias_stats.modref_baseptr_tests++;
tree arg = gimple_call_arg (stmt, access_node->parm_index);
if (integer_zerop (arg) && flag_delete_null_pointer_checks)
continue;
if (!POINTER_TYPE_P (TREE_TYPE (arg)))
return true;
/* ao_ref_init_from_ptr_and_range assumes that memory access
starts by the pointed to location. If we did not track the
offset it is possible that it starts before the actual
pointer. */
if (!access_node->parm_offset_known)
{
if (ptr_deref_may_alias_ref_p_1 (arg, ref))
return true;
}
else
{
ao_ref ref2;
poly_offset_int off = (poly_offset_int)access_node->offset
+ ((poly_offset_int)access_node->parm_offset
<< LOG2_BITS_PER_UNIT);
poly_int64 off2;
if (off.to_shwi (&off2))
{
ao_ref_init_from_ptr_and_range
(&ref2, arg, true, off2,
access_node->size,
access_node->max_size);
ref2.ref_alias_set = ref_set;
ref2.base_alias_set = base_set;
if (refs_may_alias_p_1 (&ref2, ref, tbaa_p))
return true;
}
else if (ptr_deref_may_alias_ref_p_1 (arg, ref))
return true;
}
num_tests++;
}
}
}
return false;
}
/* Check if REF conflicts with call using "fn spec" attribute.
If CLOBBER is true we are checking for writes, otherwise check loads.
Return 0 if there are no conflicts (except for possible function call
argument reads), 1 if there are conflicts and -1 if we can not decide by
fn spec. */
static int
check_fnspec (gcall *call, ao_ref *ref, bool clobber)
{
attr_fnspec fnspec = gimple_call_fnspec (call);
if (fnspec.known_p ())
{
if (clobber
? !fnspec.global_memory_written_p ()
: !fnspec.global_memory_read_p ())
{
for (unsigned int i = 0; i < gimple_call_num_args (call); i++)
if (POINTER_TYPE_P (TREE_TYPE (gimple_call_arg (call, i)))
&& (!fnspec.arg_specified_p (i)
|| (clobber ? fnspec.arg_maybe_written_p (i)
: fnspec.arg_maybe_read_p (i))))
{
ao_ref dref;
tree size = NULL_TREE;
unsigned int size_arg;
if (!fnspec.arg_specified_p (i))
;
else if (fnspec.arg_max_access_size_given_by_arg_p
(i, &size_arg))
size = gimple_call_arg (call, size_arg);
else if (fnspec.arg_access_size_given_by_type_p (i))
{
tree callee = gimple_call_fndecl (call);
tree t = TYPE_ARG_TYPES (TREE_TYPE (callee));
for (unsigned int p = 0; p < i; p++)
t = TREE_CHAIN (t);
size = TYPE_SIZE_UNIT (TREE_TYPE (TREE_VALUE (t)));
}
ao_ref_init_from_ptr_and_size (&dref,
gimple_call_arg (call, i),
size);
if (refs_may_alias_p_1 (&dref, ref, false))
return 1;
}
if (clobber
&& fnspec.errno_maybe_written_p ()
&& flag_errno_math
&& targetm.ref_may_alias_errno (ref))
return 1;
return 0;
}
}
/* FIXME: we should handle barriers more consistently, but for now leave the
check here. */
if (gimple_call_builtin_p (call, BUILT_IN_NORMAL))
switch (DECL_FUNCTION_CODE (gimple_call_fndecl (call)))
{
/* __sync_* builtins and some OpenMP builtins act as threading
barriers. */
#undef DEF_SYNC_BUILTIN
#define DEF_SYNC_BUILTIN(ENUM, NAME, TYPE, ATTRS) case ENUM:
#include "sync-builtins.def"
#undef DEF_SYNC_BUILTIN
case BUILT_IN_GOMP_ATOMIC_START:
case BUILT_IN_GOMP_ATOMIC_END:
case BUILT_IN_GOMP_BARRIER:
case BUILT_IN_GOMP_BARRIER_CANCEL:
case BUILT_IN_GOMP_TASKWAIT:
case BUILT_IN_GOMP_TASKGROUP_END:
case BUILT_IN_GOMP_CRITICAL_START:
case BUILT_IN_GOMP_CRITICAL_END:
case BUILT_IN_GOMP_CRITICAL_NAME_START:
case BUILT_IN_GOMP_CRITICAL_NAME_END:
case BUILT_IN_GOMP_LOOP_END:
case BUILT_IN_GOMP_LOOP_END_CANCEL:
case BUILT_IN_GOMP_ORDERED_START:
case BUILT_IN_GOMP_ORDERED_END:
case BUILT_IN_GOMP_SECTIONS_END:
case BUILT_IN_GOMP_SECTIONS_END_CANCEL:
case BUILT_IN_GOMP_SINGLE_COPY_START:
case BUILT_IN_GOMP_SINGLE_COPY_END:
return 1;
default:
return -1;
}
return -1;
}
/* If the call CALL may use the memory reference REF return true,
otherwise return false. */
static bool
ref_maybe_used_by_call_p_1 (gcall *call, ao_ref *ref, bool tbaa_p)
{
tree base, callee;
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;
/* A call that is not without side-effects might involve volatile
accesses and thus conflicts with all other volatile accesses. */
if (ref->volatile_p)
return true;
callee = gimple_call_fndecl (call);
if (!gimple_call_chain (call) && callee != NULL_TREE)
{
struct cgraph_node *node = cgraph_node::get (callee);
/* We can not safely optimize based on summary of calle if it does
not always bind to current def: it is possible that memory load
was optimized out earlier and the interposed variant may not be
optimized this way. */
if (node && node->binds_to_current_def_p ())
{
modref_summary *summary = get_modref_function_summary (node);
if (summary)
{
if (!modref_may_conflict (call, summary->loads, ref, tbaa_p))
{
alias_stats.modref_use_no_alias++;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file,
"ipa-modref: call stmt ");
print_gimple_stmt (dump_file, call, 0);
fprintf (dump_file,
"ipa-modref: call to %s does not use ",
node->dump_name ());
if (!ref->ref && ref->base)
{
fprintf (dump_file, "base: ");
print_generic_expr (dump_file, ref->base);
}
else if (ref->ref)
{
fprintf (dump_file, "ref: ");
print_generic_expr (dump_file, ref->ref);
}
fprintf (dump_file, " alias sets: %i->%i\n",
ao_ref_base_alias_set (ref),
ao_ref_alias_set (ref));
}
goto process_args;
}
alias_stats.modref_use_may_alias++;
}
}
}
base = ao_ref_base (ref);
if (!base)
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;
if (int res = check_fnspec (call, ref, false))
{
if (res == 1)
return true;
}
else
goto process_args;
/* Check if base is a global static variable that is not read
by the function. */
if (callee != NULL_TREE && VAR_P (base) && TREE_STATIC (base))
{
struct cgraph_node *node = cgraph_node::get (callee);
bitmap read;
int id;
/* FIXME: Callee can be an OMP builtin that does not have a call graph
node yet. We should enforce that there are nodes for all decls in the
IL and remove this check instead. */
if (node
&& (id = ipa_reference_var_uid (base)) != -1
&& (read = ipa_reference_get_read_global (node))
&& !bitmap_bit_p (read, id))
goto process_args;
}
/* Check if the base variable is call-used. */<