From aa2e903e1d7f30c546b4e77f0aa71dff6c95754f Mon Sep 17 00:00:00 2001
From: Richard Biener <rguenther@suse.de>
Date: Wed, 28 Nov 2018 11:01:06 +0000
Subject: [PATCH] re PR tree-optimization/79351 (Invalid tree PRE optimization
 around compound literal)

2018-11-28  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/79351
	* tree-ssa-sccvn.c (vn_reference_lookup_3): For assignments from
	empty CONSTRUCTORs ensure the store is at a constant position.

	* gcc.dg/torture/pr79351.c: New testcase.

From-SVN: r266551
---
 gcc/ChangeLog                          |  6 ++++++
 gcc/testsuite/ChangeLog                |  7 ++++++-
 gcc/testsuite/gcc.dg/torture/pr79351.c | 26 ++++++++++++++++++++++++++
 gcc/tree-ssa-sccvn.c                   |  1 +
 4 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/torture/pr79351.c

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 93b35e87c5c..d1123888cb8 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2018-11-28  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/79351
+	* tree-ssa-sccvn.c (vn_reference_lookup_3): For assignments from
+	empty CONSTRUCTORs ensure the store is at a constant position.
+
 2018-11-28  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/88229
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 5d3b2d12664..b56d3dc40dd 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-11-28  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/79351
+	* gcc.dg/torture/pr79351.c: New testcase.
+
 2018-11-28  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/88189
@@ -13,7 +18,7 @@
 	PR c++/88215
 	* c-c++-common/ubsan/pr88215.c: New test.
 
-2018-10-19  Richard Biener  <rguenther@suse.de>
+2018-11-28  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/88182
 	* g++.dg/gomp/pr88182.C: Move from libgomp and use -fopenmp-simd.
diff --git a/gcc/testsuite/gcc.dg/torture/pr79351.c b/gcc/testsuite/gcc.dg/torture/pr79351.c
new file mode 100644
index 00000000000..0e145eb7e3b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr79351.c
@@ -0,0 +1,26 @@
+/* { dg-do run } */
+
+static struct state {
+    int k;
+    int dummy;
+} states[256];
+
+__attribute((noipa))
+static void
+ismatch(int n)
+{
+  for (int j=0; j<n; j++) {
+      states[j] = (struct state){0};
+      for (int i = 0; i <= j; i++) {
+	  states[i].k++;
+      }
+  }
+}
+
+int
+main()
+{
+  ismatch(2);
+  if (states[0].k != 2)
+    __builtin_abort();
+}
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index e0ff40555ea..b0b9d5221f4 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -2115,6 +2115,7 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *vr_,
       base2 = get_ref_base_and_extent (gimple_assign_lhs (def_stmt),
 				       &offset2, &size2, &maxsize2, &reverse);
       if (known_size_p (maxsize2)
+	  && known_eq (maxsize2, size2)
 	  && operand_equal_p (base, base2, 0)
 	  && known_subrange_p (offset, maxsize, offset2, size2))
 	{
-- 
2.30.2