SUBST (SET_SRC (x), src);
}
+#ifdef WORD_REGISTER_OPERATIONS
/* If we have (set x (subreg:m1 (op:m2 ...) 0)) with OP being some operation,
and X being a REG or (subreg (reg)), we may be able to convert this to
(set (subreg:m2 x) (op)).
- We can always do this if M1 is narrower than M2 because that means that
- we only care about the low bits of the result.
+ On a machine where WORD_REGISTER_OPERATIONS is defined, this
+ transformation is safe as long as M1 and M2 have the same number
+ of words.
- However, on machines without WORD_REGISTER_OPERATIONS defined, we cannot
- perform a narrower operation than requested since the high-order bits will
- be undefined. On machine where it is defined, this transformation is safe
- as long as M1 and M2 have the same number of words. */
+ However, on a machine without WORD_REGISTER_OPERATIONS defined,
+ we cannot apply this transformation because it would create a
+ paradoxical subreg in SET_DEST. */
if (GET_CODE (src) == SUBREG && subreg_lowpart_p (src)
&& GET_RTX_CLASS (GET_CODE (SUBREG_REG (src))) != 'o'
/ UNITS_PER_WORD)
== ((GET_MODE_SIZE (GET_MODE (SUBREG_REG (src)))
+ (UNITS_PER_WORD - 1)) / UNITS_PER_WORD))
-#ifndef WORD_REGISTER_OPERATIONS
- && (GET_MODE_SIZE (GET_MODE (src))
- < GET_MODE_SIZE (GET_MODE (SUBREG_REG (src))))
-#endif
#ifdef CANNOT_CHANGE_MODE_CLASS
&& ! (GET_CODE (dest) == REG && REGNO (dest) < FIRST_PSEUDO_REGISTER
&& REG_CANNOT_CHANGE_MODE_P (REGNO (dest),
src = SET_SRC (x), dest = SET_DEST (x);
}
+#endif
#ifdef HAVE_cc0
/* If we have (set (cc0) (subreg ...)), we try to remove the subreg