From: Richard Biener <rguenther@suse.de>
To: gcc-patches@gcc.gnu.org
Subject: [PATCH] tree-optimization/107107 - tail-merging VN wrong-code
Date: Thu, 6 Oct 2022 10:07:08 +0000 (UTC) [thread overview]
Message-ID: <20221006100708.6ph-PMVUP-3qYtVnDWr8R2IzVxais2IPZ3Z6GuG50do@z> (raw)
The following fixes an unintended(?) side-effect of the special
MODIFY_EXPR expression entries we add for tail-merging during VN.
We shouldn't value-number the virtual operand differently here.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
PR tree-optimization/107107
* tree-ssa-sccvn.cc (visit_reference_op_store): Do not
affect value-numbering when doing the tail merging
MODIFY_EXPR lookup.
* gcc.dg/pr107107.c: New testcase.
---
gcc/testsuite/gcc.dg/pr107107.c | 25 +++++++++++++++++++++++++
gcc/tree-ssa-sccvn.cc | 17 +++--------------
2 files changed, 28 insertions(+), 14 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/pr107107.c
diff --git a/gcc/testsuite/gcc.dg/pr107107.c b/gcc/testsuite/gcc.dg/pr107107.c
new file mode 100644
index 00000000000..5ad6a63159e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr107107.c
@@ -0,0 +1,25 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -ftree-tail-merge" } */
+
+static inline void set_longish(int is_long_long, void *p, long x)
+{
+ if (is_long_long)
+ *(long long*)p = x;
+ else
+ *(long*)p = x;
+}
+static long test(long long *p, int index, int mode)
+{
+ *p = 1;
+ set_longish(mode, p+index, 2);
+ return *p;
+}
+long (*volatile vtest)(long long*, int, int) = test;
+int main(void)
+{
+ long long x;
+ long result = vtest(&x, 0, 1);
+ if (result != 2 || x != 2)
+ __builtin_abort ();
+ return 0;
+}
diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
index 2cc2c0e1e34..37484403c56 100644
--- a/gcc/tree-ssa-sccvn.cc
+++ b/gcc/tree-ssa-sccvn.cc
@@ -5718,19 +5718,6 @@ visit_reference_op_store (tree lhs, tree op, gimple *stmt)
if (!resultsame)
{
- /* Only perform the following when being called from PRE
- which embeds tail merging. */
- if (default_vn_walk_kind == VN_WALK)
- {
- assign = build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, op);
- vn_reference_lookup (assign, vuse, VN_NOWALK, &vnresult, false);
- if (vnresult)
- {
- VN_INFO (vdef)->visited = true;
- return set_ssa_val_to (vdef, vnresult->result_vdef);
- }
- }
-
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "No store match\n");
@@ -5755,7 +5742,9 @@ visit_reference_op_store (tree lhs, tree op, gimple *stmt)
if (default_vn_walk_kind == VN_WALK)
{
assign = build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, op);
- vn_reference_insert (assign, lhs, vuse, vdef);
+ vn_reference_lookup (assign, vuse, VN_NOWALK, &vnresult, false);
+ if (!vnresult)
+ vn_reference_insert (assign, lhs, vuse, vdef);
}
}
else
--
2.35.3
reply other threads:[~2022-10-06 10:07 UTC|newest]
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