re PR rtl-optimization/82913 (ICE: Segmentation fault in try_merge_compare)

	PR rtl-optimization/82913
	* compare-elim.c (try_merge_compare): Punt if def_insn is not
	single set.

	* gcc.c-torture/compile/pr82913.c: New test.

From-SVN: r254614

gcc/ChangeLog

+2017-11-10  Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/82913
+	* compare-elim.c (try_merge_compare): Punt if def_insn is not
+	single set.
+
 2017-11-09  Jeff Law  <law@redhat.com>
 
 	* vr-values.h: New file with vr_values class.

gcc/compare-elim.c

@@ -683,6 +683,8 @@ try_merge_compare (struct comparison *cmp)
 
   rtx_insn *def_insn = cmp->in_a_setter;
   rtx set = single_set (def_insn);
+  if (!set)
+    return false;
 
   if (!can_merge_compare_into_arith (cmp_insn, def_insn))
     return false;

gcc/testsuite/ChangeLog

+2017-11-10  Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/82913
+	* gcc.c-torture/compile/pr82913.c: New test.
+
 2017-11-09  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/78619

gcc/testsuite/gcc.c-torture/compile/pr82913.c

+/* PR rtl-optimization/82913 */
+
+unsigned int a;
+unsigned long int b;
+
+int
+foo (void)
+{
+  ++a;
+  b = 0;
+}
+
+unsigned long int
+bar (int x)
+{
+  if (!foo () || !a)
+    {
+      int c = a != b;
+      if (c != x)
+        return a;
+    }
+  return 0;
+}