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combine.c (simplify_set): Don't move a subreg in SET_SRC to SET_DEST if... 

* combine.c (simplify_set): Don't move a subreg in SET_SRC to
	SET_DEST if WORD_REGISTER_OPERATIONS is not defined.

From-SVN: r67388
This commit is contained in:
Kazu Hirata 2003-06-03 17:10:48 +00:00 committed by Kazu Hirata
parent bf46042bdb
commit 8d6b2775ec
2 changed files with 13 additions and 10 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2003-06-03 Kazu Hirata <kazu@cs.umass.edu>
* combine.c (simplify_set): Don't move a subreg in SET_SRC to
SET_DEST if WORD_REGISTER_OPERATIONS is not defined.
2003-06-03 Nathanael Nerode <neroden@gcc.gnu.org>
* config/i386/x86-64.h: Remove two target-independent comments;

18
gcc/combine.c
View File

@ -5238,17 +5238,18 @@ simplify_set (x)
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'
@ -5256,10 +5257,6 @@ simplify_set (x)
/ 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),
@ -5277,6 +5274,7 @@ simplify_set (x)
src = SET_SRC (x), dest = SET_DEST (x);
}
#endif
#ifdef HAVE_cc0
/* If we have (set (cc0) (subreg ...)), we try to remove the subreg