From: rguenth <rguenth@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Wed, 29 Aug 2018 06:47:14 +0000 (+0000)
Subject: 2018-08-29  Richard Biener  <rguenther@suse.de>
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=881d204865d6999f24336a651771b5d7973f16f1;p=thirdparty%2Fgcc.git

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

	PR tree-optimization/87126
	* tree-ssa-sccvn.c (vn_reference_insert): Remove assert.

	* gcc.dg/tree-ssa/pr87126.c: New testcase.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@263944 138bc75d-0d04-0410-961f-82ee72b054a4
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index c41507662ddd..03a98c90ab28 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2018-08-29  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/87126
+	* tree-ssa-sccvn.c (vn_reference_insert): Remove assert.
+
 2018-08-28  Jim Wilson  <jimw@sifive.com>
 
 	* config/riscv/pic.md: Rewrite.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 72f5a95984e7..e6a9c8610cd2 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-08-29  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/87126
+	* gcc.dg/tree-ssa/pr87126.c: New testcase.
+
 2018-08-28 MCC CS <deswurstes@users.noreply.github.com>
 
 	PR tree-optimization/87009
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr87126.c b/gcc/testsuite/gcc.dg/tree-ssa/pr87126.c
new file mode 100644
index 000000000000..37232ba3a0a8
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr87126.c
@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-fre1" } */
+
+int a, *b;
+
+void f ()
+{ 
+  int d = 0, e = d;
+  while (a++)
+    ;
+  if (e)
+    goto L2;
+L1:
+  d = e;
+  b = &d;
+L2:
+  if (d)
+    goto L1;
+}
+
+/* The load of d could be eliminated if we'd value-number the
+   irreducible region in RPO of the reducible result.  Likewise
+   a redundant store could be removed.  */
+/* { dg-final { scan-tree-dump-times "d = 0;" 1 "fre1" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-not " = d;" "fre1" { xfail *-*-* } } } */
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 2556b0c45271..aaac430bb46e 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -2696,7 +2696,17 @@ vn_reference_insert (tree op, tree result, tree vuse, tree vdef)
      but save a lookup if we deal with already inserted refs here.  */
   if (*slot)
     {
-      gcc_assert (operand_equal_p ((*slot)->result, vr1->result, 0));
+      /* We cannot assert that we have the same value either because
+         when disentangling an irreducible region we may end up visiting
+	 a use before the corresponding def.  That's a missed optimization
+	 only though.  See gcc.dg/tree-ssa/pr87126.c for example.  */
+      if (dump_file && (dump_flags & TDF_DETAILS)
+	  && !operand_equal_p ((*slot)->result, vr1->result, 0))
+	{
+	  fprintf (dump_file, "Keeping old value ");
+	  print_generic_expr (dump_file, (*slot)->result);
+	  fprintf (dump_file, " because of collision\n");
+	}
       free_reference (vr1);
       obstack_free (&vn_tables_obstack, vr1);
       return;