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re PR tree-optimization/77745 (Inconsistent application of aliasing rules)

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2016-09-27  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/77745
	* tree-ssa-pre.c (eliminate_dom_walker::before_dom_children):
	When removing redundant stores make sure to check compatibility
	of the TBAA state for downstream accesses.
	* tree-ssa-sccvn.c (visit_reference_op_store): Likewise for when
	value-numbering virtual operands for store matches.

	* g++.dg/torture/pr77745.C: New testcase.

From-SVN: r240534
This commit is contained in:
Richard Biener 2016-09-27 12:56:38 +00:00 committed by Richard Biener
parent 4e7e89e8c9
commit 59896334f9
5 changed files with 74 additions and 20 deletions
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9
gcc/ChangeLog
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@ -1,3 +1,12 @@
2016-09-27 Richard Biener <rguenther@suse.de>
PR tree-optimization/77745
* tree-ssa-pre.c (eliminate_dom_walker::before_dom_children):
When removing redundant stores make sure to check compatibility
of the TBAA state for downstream accesses.
* tree-ssa-sccvn.c (visit_reference_op_store): Likewise for when
value-numbering virtual operands for store matches.
2016-09-27 Oleg Endo <olegendo@gcc.gnu.org>
PR target/51244

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2016-09-27 Richard Biener <rguenther@suse.de>
PR tree-optimization/77745
* g++.dg/torture/pr77745.C: New testcase.
2016-09-27 Richard Biener <rguenther@suse.de>
PR tree-optimization/77478

24
gcc/testsuite/g++.dg/torture/pr77745.C Normal file
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@ -0,0 +1,24 @@
// { dg-do run }
inline void* operator new(__SIZE_TYPE__, void* __p) noexcept { return __p; }
long foo(char *c1, char *c2)
{
long *p1 = new (c1) long;
*p1 = 100;
long long *p2 = new (c2) long long;
*p2 = 200;
long *p3 = new (c2) long;
*p3 = 200;
return *p1;
}
int main()
{
union {
char c;
long l;
long long ll;
} c;
if (foo(&c.c, &c.c) != 200)
__builtin_abort();
}

44
gcc/tree-ssa-pre.c
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@ -4431,26 +4431,34 @@ eliminate_dom_walker::before_dom_children (basic_block b)
&& !is_gimple_reg (gimple_assign_lhs (stmt))
&& (TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME
|| is_gimple_min_invariant (gimple_assign_rhs1 (stmt))))
{
tree val;
{
tree val;
tree rhs = gimple_assign_rhs1 (stmt);
val = vn_reference_lookup (gimple_assign_lhs (stmt),
gimple_vuse (stmt), VN_WALK, NULL, false);
if (TREE_CODE (rhs) == SSA_NAME)
rhs = VN_INFO (rhs)->valnum;
if (val
&& operand_equal_p (val, rhs, 0))
{
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Deleted redundant store ");
print_gimple_stmt (dump_file, stmt, 0, 0);
}
vn_reference_t vnresult;
val = vn_reference_lookup (lhs, gimple_vuse (stmt), VN_WALKREWRITE,
&vnresult, false);
if (TREE_CODE (rhs) == SSA_NAME)
rhs = VN_INFO (rhs)->valnum;
if (val
&& operand_equal_p (val, rhs, 0))
{
/* We can only remove the later store if the former aliases
at least all accesses the later one does. */
alias_set_type set = get_alias_set (lhs);
if (vnresult->set == set
|| alias_set_subset_of (set, vnresult->set))
{
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Deleted redundant store ");
print_gimple_stmt (dump_file, stmt, 0, 0);
}
/* Queue stmt for removal. */
el_to_remove.safe_push (stmt);
continue;
}
/* Queue stmt for removal. */
el_to_remove.safe_push (stmt);
continue;
}
}
}
/* If this is a control statement value numbering left edges

12
gcc/tree-ssa-sccvn.c
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@ -3599,13 +3599,21 @@ visit_reference_op_store (tree lhs, tree op, gimple *stmt)
Otherwise, the vdefs for the store are used when inserting into
the table, since the store generates a new memory state. */
result = vn_reference_lookup (lhs, vuse, VN_NOWALK, NULL, false);
result = vn_reference_lookup (lhs, vuse, VN_NOWALK, &vnresult, false);
if (result)
{
if (TREE_CODE (result) == SSA_NAME)
result = SSA_VAL (result);
resultsame = expressions_equal_p (result, op);
if (resultsame)
{
/* If the TBAA state isn't compatible for downstream reads
we cannot value-number the VDEFs the same. */
alias_set_type set = get_alias_set (lhs);
if (vnresult->set != set
&& ! alias_set_subset_of (set, vnresult->set))
resultsame = false;
}
}
if ((!result || !resultsame)