re PR rtl-optimization/80501 (Wrong code w/ a signed char, a shift, and a conversion to int)

	PR rtl-optimization/80501
	* combine.c (make_compound_operation_int): Set subreg_code to SET
	even for AND with mask of the sign bit of mode.

	* gcc.c-torture/execute/pr80501.c: New test.

From-SVN: r247128

gcc/ChangeLog

 2017-04-25  Jakub Jelinek  <jakub@redhat.com>
 
+	PR rtl-optimization/80501
+	* combine.c (make_compound_operation_int): Set subreg_code to SET
+	even for AND with mask of the sign bit of mode.
+
 	PR rtl-optimization/80500
 	* loop-unroll.c (combine_var_copies_in_loop_exit): Call copy_rtx on
 	sum's initial value.

gcc/combine.c

@@ -8170,12 +8170,15 @@ make_compound_operation_int (machine_mode mode, rtx *x_ptr,
 		|| GET_CODE (inner) == SUBREG
 		/* (subreg:SI (and:DI (reg:DI) (const_int 0x800000000)) 0)
 		   is (const_int 0), rather than
-		   (subreg:SI (lshiftrt:DI (reg:DI) (const_int 35)) 0).  */
+		   (subreg:SI (lshiftrt:DI (reg:DI) (const_int 35)) 0).
+		   Similarly (subreg:QI (and:SI (reg:SI) (const_int 0x80)) 0)
+		   for non-equality comparisons against 0 is not equivalent
+		   to (subreg:QI (lshiftrt:SI (reg:SI) (const_int 7)) 0).  */
 		|| (GET_CODE (inner) == AND
 		    && CONST_INT_P (XEXP (inner, 1))
 		    && GET_MODE_SIZE (mode) < GET_MODE_SIZE (GET_MODE (inner))
 		    && exact_log2 (UINTVAL (XEXP (inner, 1)))
-		       >= GET_MODE_BITSIZE (mode))))
+		       >= GET_MODE_BITSIZE (mode) - 1)))
 	  subreg_code = SET;
 
 	tem = make_compound_operation (inner, subreg_code);

gcc/testsuite/ChangeLog

 2017-04-25  Jakub Jelinek  <jakub@redhat.com>
 
+	PR rtl-optimization/80501
+	* gcc.c-torture/execute/pr80501.c: New test.
+
 	PR rtl-optimization/80500
 	* gcc.dg/pr80500.c: New test.
 

gcc/testsuite/gcc.c-torture/execute/pr80501.c

+/* PR rtl-optimization/80501 */
+
+signed char v = 0;
+
+static signed char
+foo (int x, int y)
+{
+  return x << y;
+}
+
+__attribute__((noinline, noclone)) int
+bar (void)
+{
+  return foo (v >= 0, __CHAR_BIT__ - 1) >= 1;
+}
+
+int
+main ()
+{
+  if (sizeof (int) > sizeof (char) && bar () != 0)
+    __builtin_abort ();
+  return 0;
+}