re PR tree-optimization/77514 (ICE in VN_INFO_GET, at tree-ssa-sccvn.c:406 w/ -O2 (and above))

2016-09-15  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/77514
	* tree-ssa-pre.c (create_expression_by_pieces): Handle garbage
	only forced_stmts sequence.

	* gcc.dg/torture/pr77514.c: New testcase.

From-SVN: r240153

gcc/ChangeLog

+2016-09-15  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/77514
+	* tree-ssa-pre.c (create_expression_by_pieces): Handle garbage
+	only forced_stmts sequence.
+
 2016-09-15  Kugan Vivekanandarajah  <kuganv@linaro.org>
 
 	* tree-ssanames.h (FOR_EACH_SSA_NAME): New.

gcc/testsuite/ChangeLog

+2016-09-15  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/77514
+	* gcc.dg/torture/pr77514.c: New testcase.
+
 2016-09-14  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/77549

gcc/testsuite/gcc.dg/torture/pr77514.c

+/* { dg-do compile } */
+
+void
+m1 (char l0, char e8, int hw)
+{
+  char *rs = &l0;
+
+yu:
+  l0 = 1;
+  while (l0 != 0)
+    {
+      l0 = -l0;
+      l0 += (*rs ^ (l0 &= 1));
+    }
+  for (;;)
+    {
+      if (hw != 0)
+	goto yu;
+      rs = &e8;
+    }
+}

gcc/tree-ssa-pre.c

@@ -2879,7 +2879,21 @@ create_expression_by_pieces (basic_block block, pre_expr expr,
       gimple_seq_discard (forced_stmts);
       return folded;
     }
-
+  /* Likewise if we simplified to sth not queued for insertion.  */
+  bool found = false;
+  gsi = gsi_start (forced_stmts);
+  for (; !gsi_end_p (gsi); gsi_next (&gsi))
+    {
+      gimple *stmt = gsi_stmt (gsi);
+      tree forcedname = gimple_get_lhs (stmt);
+      if (forcedname == folded)
+	found = true;
+    }
+  if (! found)
+    {
+      gimple_seq_discard (forced_stmts);
+      return folded;
+    }
   gcc_assert (TREE_CODE (folded) == SSA_NAME);
 
   /* If we have any intermediate expressions to the value sets, add them