re PR rtl-optimization/70429 (Wrong code with -O1.)

PR rtl-optimization/70429
	* combine.c (simplify_shift_const_1): For ASHIFTRT don't optimize
	(cst1 >> count) >> cst2 into (cst1 >> cst2) >> count if
	mode != result_mode.

	* gcc.c-torture/execute/pr70429.c: New test.

From-SVN: r234531

gcc/ChangeLog

@@ -1,5 +1,10 @@
 2016-03-29  Jakub Jelinek  <jakub@redhat.com>
 
+	PR rtl-optimization/70429
+	* combine.c (simplify_shift_const_1): For ASHIFTRT don't optimize
+	(cst1 >> count) >> cst2 into (cst1 >> cst2) >> count if
+	mode != result_mode.
+
 	PR c++/70353
 	* tree-inline.c (remap_decls): Don't add_local_decl if
 	cfun is null.

gcc/combine.c

@@ -10533,6 +10533,11 @@ simplify_shift_const_1 (enum rtx_code code, machine_mode result_mode,
 				       >> orig_count, result_mode,
 				       &complement_p))
 		break;
+	      /* For ((int) (cstLL >> count)) >> cst2 just give up.  Queuing
+		 up outer sign extension (often left and right shift) is
+		 hardly more efficient than the original.  See PR70429.  */
+	      if (code == ASHIFTRT && mode != result_mode)
+		break;
 
 	      rtx new_rtx = simplify_const_binary_operation (code, mode,
 							     XEXP (varop, 0),

gcc/testsuite/ChangeLog

@@ -1,5 +1,8 @@
 2016-03-29  Jakub Jelinek  <jakub@redhat.com>
 
+	PR rtl-optimization/70429
+	* gcc.c-torture/execute/pr70429.c: New test.
+
 	PR tree-optimization/70405
 	* gcc.dg/pr70405.c: New test.
 

gcc/testsuite/gcc.c-torture/execute/pr70429.c

@@ -0,0 +1,17 @@
+/* PR rtl-optimization/70429 */
+
+__attribute__((noinline, noclone)) int
+foo (int a)
+{
+  return (int) (0x14ff6e2207db5d1fLL >> a) >> 4;
+}
+
+int
+main ()
+{
+  if (sizeof (int) != 4 || sizeof (long long) != 8 || __CHAR_BIT__ != 8)
+    return 0;
+  if (foo (1) != 0x3edae8 || foo (2) != -132158092)
+    __builtin_abort ();
+  return 0;
+}