simplify-rtx.c (simplify_unary_operation_1): When trying to remove TRUNCATE…

simplify-rtx.c (simplify_unary_operation_1): When trying to remove TRUNCATE check if all bits outside the new mode are...

	* simplify-rtx.c (simplify_unary_operation_1) <TRUNCATE>: When
	trying to remove TRUNCATE check if all bits outside the new mode
	are identical to the sign bit.

From-SVN: r112643

gcc/ChangeLog

+2006-04-03  Adam Nemet  <anemet@caviumnetworks.com>
+
+	* simplify-rtx.c (simplify_unary_operation_1) <TRUNCATE>: When
+	trying to remove TRUNCATE check if all bits outside the new mode
+	are identical to the sign bit.
+
 2006-04-03  Jeff Law  <law@redhat.com>
 
 	* tree-ssa-dom.c (propagate_rhs_into_lhs): Avoid useless folding

gcc/simplify-rtx.c

@@ -656,7 +656,8 @@ simplify_unary_operation_1 (enum rtx_code code, enum machine_mode mode, rtx op)
       if ((TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (mode),
 				 GET_MODE_BITSIZE (GET_MODE (op)))
 	   ? (num_sign_bit_copies (op, GET_MODE (op))
-	      >= (unsigned int) (GET_MODE_BITSIZE (mode) + 1))
+	      > (unsigned int) (GET_MODE_BITSIZE (GET_MODE (op))
+				- GET_MODE_BITSIZE (mode)))
 	   : truncated_to_mode (mode, op))
 	  && ! (GET_CODE (op) == LSHIFTRT
 		&& GET_CODE (XEXP (op, 0)) == MULT))