From: Richard Biener <rguenther@suse.de>
Date: Wed, 29 Aug 2018 14:13:20 +0000 (+0000)
Subject: re PR tree-optimization/87132 (Gcc miscompiles at -O2 on valid code)
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=8f70fdc31a7b0099e7322d0aba94830fb08f4c88;p=gcc.git

re PR tree-optimization/87132 (Gcc miscompiles at -O2 on valid code)

2018-08-29  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/87132
	* tree-ssa-alias.c (get_continuation_for_phi): Do not translate
	when skipping defs reachable over backedges.

	* gcc.dg/torture/pr87132.c: New testcase.

From-SVN: r263959
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 02a7b94d1f2..91a06ed7a16 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2018-08-29  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/87132
+	* tree-ssa-alias.c (get_continuation_for_phi): Do not translate
+	when skipping defs reachable over backedges.
+
 2018-08-29  Richard Biener  <rguenther@suse.de>
 
 	* tree-core.h: Document use of deprecated_flag in SSA_NAME.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index ebdfcf5904a..d785c903497 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-08-29  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/87132
+	* gcc.dg/torture/pr87132.c: New testcase.
+
 2018-08-29  David Malcolm  <dmalcolm@redhat.com>
 
 	PR c++/85110
diff --git a/gcc/testsuite/gcc.dg/torture/pr87132.c b/gcc/testsuite/gcc.dg/torture/pr87132.c
new file mode 100644
index 00000000000..48b8673bba3
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr87132.c
@@ -0,0 +1,18 @@
+/* { dg-do run } */
+
+extern void abort (void);
+int c, d;
+int main()
+{
+  int e[] = {4, 4, 4, 4, 4, 4, 4, 4, 4};
+  d = 8;
+  for (; d; d--)
+    for (int a = 0; a <= 8; a++)
+      {
+	c = e[1];
+	e[d] = 0;
+      }
+  if (c != 0)
+    abort ();
+  return 0;
+}
diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
index 6efe4c3a4a7..032e79b8ba0 100644
--- a/gcc/tree-ssa-alias.c
+++ b/gcc/tree-ssa-alias.c
@@ -2740,7 +2740,14 @@ next:;
       if (arg1 == arg0)
 	;
       else if (! maybe_skip_until (phi, arg0, ref, arg1, cnt, visited,
-				   abort_on_visited, translate, data))
+				   abort_on_visited,
+				   /* Do not translate when walking over
+				      backedges.  */
+				   dominated_by_p
+				     (CDI_DOMINATORS,
+				      gimple_bb (SSA_NAME_DEF_STMT (arg1)),
+				      phi_bb)
+				   ? NULL : translate, data))
 	return NULL_TREE;
     }