re PR rtl-optimization/13821 (IRIX 6.5 bootstrap failure: ICE in simplify_gen_subreg)

	PR optimization/13821
	* simplify-rtx.c (simplify_subreg): Use subreg_lowpart_offset to
	correctly calculate the lowpart offset of the contracted subreg.

From-SVN: r76393

gcc/ChangeLog

+2004-01-22  Roger Sayle  <roger@eyesopen.com>
+
+	PR optimization/13821
+	* simplify-rtx.c (simplify_subreg): Use subreg_lowpart_offset to
+	correctly calculate the lowpart offset of the contracted subreg.
+
 2004-01-22  Ian Lance Taylor  <ian@wasabisystems.com>
 
 	* doc/invoke.texi (Optimize Options): Note that --param arguments

gcc/simplify-rtx.c

@@ -3404,8 +3404,9 @@ simplify_subreg (enum machine_mode outermode, rtx op,
 	  if (outermode == origmode)
 	    return XEXP (op, 0);
 	  if (GET_MODE_BITSIZE (outermode) <= GET_MODE_BITSIZE (origmode))
-	    return simplify_gen_subreg (outermode, XEXP (op, 0),
-					origmode, byte);
+	    return simplify_gen_subreg (outermode, XEXP (op, 0), origmode,
+					subreg_lowpart_offset (outermode,
+							       origmode));
 	  if (SCALAR_INT_MODE_P (outermode))
 	    return simplify_gen_unary (GET_CODE (op), outermode,
 				       XEXP (op, 0), origmode);