re PR rtl-optimization/51023 (likely integer wrong code bug)

	PR rtl-optimization/51023
	* combine.c (simplify_comparison) <case SIGN_EXTEND>: Don't use
	val_signbit_known_clear_p for signed comparison narrowing
	optimization.  Don't check for non-VOIDmode, use
	HWI_COMPUTABLE_MODE_P macro.
	<case ZERO_EXTEND>: Don't check for non-VOIDmode.
	Optimize even when const_op is equal to GET_MODE_MASK (mode),
	don't optimize if const_op is negative.

	* gcc.c-torture/execute/pr51023.c: New test.

From-SVN: r181257

gcc/ChangeLog

+2011-11-10  Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/51023
+	* combine.c (simplify_comparison) <case SIGN_EXTEND>: Don't use
+	val_signbit_known_clear_p for signed comparison narrowing
+	optimization.  Don't check for non-VOIDmode, use
+	HWI_COMPUTABLE_MODE_P macro.
+	<case ZERO_EXTEND>: Don't check for non-VOIDmode.
+	Optimize even when const_op is equal to GET_MODE_MASK (mode),
+	don't optimize if const_op is negative.
+
 2011-11-10  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/51042

gcc/combine.c

@@ -11397,9 +11397,10 @@ simplify_comparison (enum rtx_code code, rtx *pop0, rtx *pop1)
 	     later on, and then we wouldn't know whether to sign- or
 	     zero-extend.  */
 	  mode = GET_MODE (XEXP (op0, 0));
-	  if (mode != VOIDmode && GET_MODE_CLASS (mode) == MODE_INT
+	  if (GET_MODE_CLASS (mode) == MODE_INT
 	      && ! unsigned_comparison_p
-	      && val_signbit_known_clear_p (mode, const_op)
+	      && HWI_COMPUTABLE_MODE_P (mode)
+	      && trunc_int_for_mode (const_op, mode) == const_op
 	      && have_insn_for (COMPARE, mode))
 	    {
 	      op0 = XEXP (op0, 0);
@@ -11477,10 +11478,11 @@ simplify_comparison (enum rtx_code code, rtx *pop0, rtx *pop1)
 
 	case ZERO_EXTEND:
 	  mode = GET_MODE (XEXP (op0, 0));
-	  if (mode != VOIDmode && GET_MODE_CLASS (mode) == MODE_INT
+	  if (GET_MODE_CLASS (mode) == MODE_INT
 	      && (unsigned_comparison_p || equality_comparison_p)
 	      && HWI_COMPUTABLE_MODE_P (mode)
-	      && ((unsigned HOST_WIDE_INT) const_op < GET_MODE_MASK (mode))
+	      && (unsigned HOST_WIDE_INT) const_op <= GET_MODE_MASK (mode)
+	      && const_op >= 0
 	      && have_insn_for (COMPARE, mode))
 	    {
 	      op0 = XEXP (op0, 0);

gcc/testsuite/ChangeLog

+2011-11-10  Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/51023
+	* gcc.c-torture/execute/pr51023.c: New test.
+
 2011-11-10  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/51042

gcc/testsuite/gcc.c-torture/execute/pr51023.c

+/* PR rtl-optimization/51023 */
+
+extern void abort (void);
+
+short int
+foo (long int x)
+{
+  return x;
+}
+
+int
+main ()
+{
+  long int a = 0x4272AL;
+  if (foo (a) == a)
+    abort ();
+  return 0;
+}