- /* The result must be <= the second operand. */
- return cached_num_sign_bit_copies (XEXP (x, 1), mode,
+ /* The result must be <= the second operand. If the second operand
+ has (or just might have) the high bit set, we know nothing about
+ the number of sign bit copies. */
+ if (bitwidth > HOST_BITS_PER_WIDE_INT)
+ return 1;
+ else if ((nonzero_bits (XEXP (x, 1), mode)
+ & ((HOST_WIDE_INT) 1 << (bitwidth - 1))) != 0)
+ return 1;
+ else
+ return cached_num_sign_bit_copies (XEXP (x, 1), mode,