From: Richard Biener <rguenther@suse.de>
Date: Wed, 28 Nov 2018 12:57:58 +0000 (+0000)
Subject: re PR tree-optimization/79351 (Invalid tree PRE optimization around compound literal)
X-Git-Tag: releases/gcc-7.4.0~9
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=87ac68c8e56ad3b16a83c56d2f429e459987c884;p=thirdparty%2Fgcc.git

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: r266556
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 2c82d0793f97..b199ff465371 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.
+
 2018-11-26  Iain Sandoe  <iain@sandoe.co.uk>
 
 	Backport from mainline
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 0bc4908d668c..fef05c792990 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.
+
 2018-11-26  Andreas Krebbel  <krebbel@linux.ibm.com>
 
 	Backport from mainline
diff --git a/gcc/testsuite/gcc.dg/torture/pr79351.c b/gcc/testsuite/gcc.dg/torture/pr79351.c
new file mode 100644
index 000000000000..d5d0271c376d
--- /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((noinline))
+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 00bb229b4a23..8e7052f950ec 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -1936,6 +1936,7 @@ 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 (maxsize2 != -1
+	  && maxsize2 == size2
 	  && operand_equal_p (base, base2, 0)
 	  && offset2 <= offset
 	  && offset2 + size2 >= offset + maxsize)