The following fixes bogus redundant store removal by FRE/PRE and bogus
"store match" detections by VN. This amends the similar PR69776 fix.
Bootstraped on x86_64-unknown-linux-gnu, testing in progress.
2016-09-27 Richard Biener <rguent...@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.
Index: gcc/tree-ssa-pre.c
===================================================================
--- gcc/tree-ssa-pre.c (revision 240521)
+++ gcc/tree-ssa-pre.c (working copy)
@@ -4431,26 +4436,34 @@ eliminate_dom_walker::before_dom_childre
&& !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
Index: gcc/tree-ssa-sccvn.c
===================================================================
--- gcc/tree-ssa-sccvn.c (revision 240521)
+++ gcc/tree-ssa-sccvn.c (working copy)
@@ -3599,13 +3706,21 @@ visit_reference_op_store (tree lhs, tree
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)
Index: gcc/testsuite/g++.dg/torture/pr77745.C
===================================================================
--- gcc/testsuite/g++.dg/torture/pr77745.C (revision 0)
+++ gcc/testsuite/g++.dg/torture/pr77745.C (working copy)
@@ -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();
+}
