+ /* (sign_extend:M (sign_extend:N <X>)) is (sign_extend:M <X>).
+ (sign_extend:M (zero_extend:N <X>)) is (zero_extend:M <X>). */
+ if (GET_CODE (op) == SIGN_EXTEND || GET_CODE (op) == ZERO_EXTEND)
+ {
+ gcc_assert (GET_MODE_BITSIZE (mode)
+ > GET_MODE_BITSIZE (GET_MODE (op)));
+ return simplify_gen_unary (GET_CODE (op), mode, XEXP (op, 0),
+ GET_MODE (XEXP (op, 0)));
+ }
+
+ /* (sign_extend:M (ashiftrt:N (ashift <X> (const_int I)) (const_int I)))
+ is (sign_extend:M (subreg:O <X>)) if there is mode with
+ GET_MODE_BITSIZE (N) - I bits.
+ (sign_extend:M (lshiftrt:N (ashift <X> (const_int I)) (const_int I)))
+ is similarly (zero_extend:M (subreg:O <X>)). */
+ if ((GET_CODE (op) == ASHIFTRT || GET_CODE (op) == LSHIFTRT)
+ && GET_CODE (XEXP (op, 0)) == ASHIFT
+ && CONST_INT_P (XEXP (op, 1))
+ && XEXP (XEXP (op, 0), 1) == XEXP (op, 1)
+ && GET_MODE_BITSIZE (GET_MODE (op)) > INTVAL (XEXP (op, 1)))
+ {
+ enum machine_mode tmode
+ = mode_for_size (GET_MODE_BITSIZE (GET_MODE (op))
+ - INTVAL (XEXP (op, 1)), MODE_INT, 1);
+ gcc_assert (GET_MODE_BITSIZE (mode)
+ > GET_MODE_BITSIZE (GET_MODE (op)));
+ if (tmode != BLKmode)
+ {
+ rtx inner =
+ rtl_hooks.gen_lowpart_no_emit (tmode, XEXP (XEXP (op, 0), 0));
+ return simplify_gen_unary (GET_CODE (op) == ASHIFTRT
+ ? SIGN_EXTEND : ZERO_EXTEND,
+ mode, inner, tmode);
+ }
+ }
+