From: rguenth <rguenth@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Tue, 4 Sep 2018 12:04:42 +0000 (+0000)
Subject: 2018-09-04  Richard Biener  <rguenther@suse.de>
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b86a1a386a1a4718ce56741c8cd75925fc6038d6;p=thirdparty%2Fgcc.git

2018-09-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/87211
	* tree-ssa-sccvn.c (visit_phi): When value-numbering to a
	backedge value we're supposed to treat as VARYING also number
	the PHI to VARYING in case it got a different value-number already.

	* gcc.dg/torture/pr87211.c: New testcase.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@264079 138bc75d-0d04-0410-961f-82ee72b054a4
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index afa7e5bf69e5..5b60b32f243d 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2018-09-04  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/87211
+	* tree-ssa-sccvn.c (visit_phi): When value-numbering to a
+	backedge value we're supposed to treat as VARYING also number
+	the PHI to VARYING in case it got a different value-number already.
+
 2018-09-04  Aldy Hernandez  <aldyh@redhat.com>
 
 	* tree-vrp.c (vrp_can_optimize_bit_op): Remove.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 8602ff4988ac..47bb26591d23 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-09-04  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/87211
+	* gcc.dg/torture/pr87211.c: New testcase.
+
 2018-09-04  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/87176
diff --git a/gcc/testsuite/gcc.dg/torture/pr87211.c b/gcc/testsuite/gcc.dg/torture/pr87211.c
new file mode 100644
index 000000000000..386d2a481c3e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr87211.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+
+int a, b;
+int i(int *);
+int *c(int *d, int *e)
+{
+  for (; b;)
+    d = e;
+  return d;
+}
+void f()
+{
+  for (;;)
+    {
+      int *g[1];
+      int h = 0;
+      for (; h < 3; h++)
+	g[0] = &a;
+      &a == g[0] || i(c((int *)g, g[0]));
+    }
+}
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 8d68b6bac599..1e4bfe5f7ba9 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -4180,7 +4180,8 @@ visit_phi (gimple *phi, bool *inserted, bool backedges_varying_p)
       }
 
   /* If the value we want to use is the backedge and that wasn't visited
-     yet drop to VARYING.  This only happens when not iterating.
+     yet or if we should take it as VARYING but it has a non-VARYING
+     value drop to VARYING.  This only happens when not iterating.
      If we value-number a virtual operand never value-number to the
      value from the backedge as that confuses the alias-walking code.
      See gcc.dg/torture/pr87176.c.  If the value is the same on a
@@ -4190,7 +4191,8 @@ visit_phi (gimple *phi, bool *inserted, bool backedges_varying_p)
       && TREE_CODE (backedge_val) == SSA_NAME
       && sameval == backedge_val
       && (SSA_NAME_IS_VIRTUAL_OPERAND (backedge_val)
-	  || !SSA_VISITED (backedge_val)))
+	  || !SSA_VISITED (backedge_val)
+	  || SSA_VAL (backedge_val) != backedge_val))
     /* Note this just drops to VARYING without inserting the PHI into
        the hashes.  */
     result = PHI_RESULT (phi);