combine.c (simplify_comparison <ASHIFTRT, LSHIFTRT>): Correct test for overflow of constant.

	* combine.c (simplify_comparison <ASHIFTRT, LSHIFTRT>): Correct
	test for overflow of constant.

From-SVN: r51349

gcc/ChangeLog

+2002-03-26  Alan Modra  <amodra@bigpond.net.au>
+
+	* combine.c (simplify_comparison <ASHIFTRT, LSHIFTRT>): Correct
+	test for overflow of constant.
+
 2002-03-25  Richard Earnshaw  <rearnsha@arm.com>
 
 	PR target/2623

gcc/combine.c

@@ -10843,9 +10843,9 @@ simplify_comparison (code, pop0, pop1)
 	      && XEXP (op0, 1) == XEXP (XEXP (op0, 0), 1)
 	      && (tmode = mode_for_size (mode_width - INTVAL (XEXP (op0, 1)),
 					 MODE_INT, 1)) != BLKmode
-	      && ((unsigned HOST_WIDE_INT) const_op <= GET_MODE_MASK (tmode)
-		  || ((unsigned HOST_WIDE_INT) -const_op
-		      <= GET_MODE_MASK (tmode))))
+	      && (((unsigned HOST_WIDE_INT) const_op
+		   + (GET_MODE_MASK (tmode) >> 1) + 1)
+		  <= GET_MODE_MASK (tmode)))
 	    {
 	      op0 = gen_lowpart_for_combine (tmode, XEXP (XEXP (op0, 0), 0));
 	      continue;
@@ -10862,9 +10862,9 @@ simplify_comparison (code, pop0, pop1)
 	      && XEXP (op0, 1) == XEXP (XEXP (XEXP (op0, 0), 0), 1)
 	      && (tmode = mode_for_size (mode_width - INTVAL (XEXP (op0, 1)),
 					 MODE_INT, 1)) != BLKmode
-	      && ((unsigned HOST_WIDE_INT) const_op <= GET_MODE_MASK (tmode)
-		  || ((unsigned HOST_WIDE_INT) -const_op
-		      <= GET_MODE_MASK (tmode))))
+	      && (((unsigned HOST_WIDE_INT) const_op
+		   + (GET_MODE_MASK (tmode) >> 1) + 1)
+		  <= GET_MODE_MASK (tmode)))
 	    {
 	      rtx inner = XEXP (XEXP (XEXP (op0, 0), 0), 0);
 	      rtx add_const = XEXP (XEXP (op0, 0), 1);
@@ -10889,9 +10889,12 @@ simplify_comparison (code, pop0, pop1)
 	      && mode_width <= HOST_BITS_PER_WIDE_INT
 	      && (nonzero_bits (XEXP (op0, 0), mode)
 		  & (((HOST_WIDE_INT) 1 << INTVAL (XEXP (op0, 1))) - 1)) == 0
-	      && (const_op == 0
-		  || (floor_log2 (const_op) + INTVAL (XEXP (op0, 1))
-		      < mode_width)))
+	      && (((unsigned HOST_WIDE_INT) const_op
+		   + (GET_CODE (op0) != LSHIFTRT
+		      ? ((GET_MODE_MASK (mode) >> INTVAL (XEXP (op0, 1)) >> 1)
+			 + 1)
+		      : 0))
+		  <= GET_MODE_MASK (mode) >> INTVAL (XEXP (op0, 1))))
 	    {
 	      /* If the shift was logical, then we must make the condition
 		 unsigned.  */