2016-03-14  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/70222
	* combine.c (simplify_shift_const_1): Force simplify_and_const_int
	for LSHIFTRT if result_mode != mode && count == 0.

	* gcc.c-torture/execute/pr70222.c: New test.

--- gcc/combine.c.jj	2016-02-11 23:52:57.000000000 +0100
+++ gcc/combine.c	2016-03-14 14:00:24.576657458 +0100
@@ -10835,8 +10835,12 @@ simplify_shift_const_1 (enum rtx_code co
     x = simplify_gen_binary (code, shift_mode, varop, GEN_INT (count));
 
   /* If we were doing an LSHIFTRT in a wider mode than it was originally,
-     turn off all the bits that the shift would have turned off.  */
-  if (orig_code == LSHIFTRT && result_mode != shift_mode)
+     turn off all the bits that the shift would have turned off.
+     Similarly do this if if we've optimized varop so that we don't perform
+     any shift.  */
+  if (orig_code == LSHIFTRT
+      && (result_mode != shift_mode
+	  || (result_mode != mode && count == 0)))
     x = simplify_and_const_int (NULL_RTX, shift_mode, x,
 				GET_MODE_MASK (result_mode) >> orig_count);
 
--- gcc/testsuite/gcc.c-torture/execute/pr70222.c.jj	2016-03-14 14:03:27.998140364 +0100
+++ gcc/testsuite/gcc.c-torture/execute/pr70222.c	2016-03-14 14:03:12.000000000 +0100
@@ -0,0 +1,30 @@
+/* PR rtl-optimization/70222 */
+
+int a = 1;
+unsigned int b = 2;
+int c = 0;
+int d = 0;
+
+void
+foo ()
+{
+  int e = ((-(c >= c)) < b) > ((int) (-1ULL >> ((a / a) * 15)));
+  d = -e;
+}
+
+__attribute__((noinline, noclone)) void
+bar (int x)
+{
+  if (x != -1)
+    __builtin_abort ();
+}
+
+int
+main ()
+{
+#if __CHAR_BIT__ == 8 && __SIZEOF_INT__ == 4 && __SIZEOF_LONG_LONG__ == 8
+  foo ();
+  bar (d);
+#endif
+  return 0;
+}