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S/390: Fix minor missed optimization
- From: "Ulrich Weigand" <Ulrich dot Weigand at de dot ibm dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Fri, 25 Oct 2002 14:30:56 +0200
- Subject: S/390: Fix minor missed optimization
- Sensitivity:
Hello,
we sometimes use (arg pointer - constant) as address, but this is rejected
by s390_decompose_address due to the out-of-range displacement.
However, after arg pointer elimination these addresses usually become
valid. This patch changes s390_decompose_address to acknowledge that.
Bootstrapped/regtested on s390-ibm-linux and s390x-ibm-linux.
ChangeLog:
* config/s390/s390.c (s390_decompose_address): Do not range check the
displacement if base or index is the argument pointer register.
Index: gcc/config/s390/s390.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/config/s390/s390.c,v
retrieving revision 1.65
diff -c -p -r1.65 s390.c
*** gcc/config/s390/s390.c 23 Oct 2002 16:32:43 -0000 1.65
--- gcc/config/s390/s390.c 24 Oct 2002 22:00:07 -0000
*************** s390_decompose_address (addr, out)
*** 1597,1604 ****
/* Allow integer constant in range. */
if (GET_CODE (disp) == CONST_INT)
{
! if (INTVAL (disp) < 0 || INTVAL (disp) >= 4096)
! return FALSE;
}
/* In the small-PIC case, the linker converts @GOT12
--- 1597,1616 ----
/* Allow integer constant in range. */
if (GET_CODE (disp) == CONST_INT)
{
! /* If the argument pointer is involved, the displacement will change
! later anyway as the argument pointer gets eliminated. This could
! make a valid displacement invalid, but it is more likely to make
! an invalid displacement valid, because we sometimes access the
! register save area via negative offsets to the arg pointer.
! Thus we don't check the displacement for validity here. If after
! elimination the displacement turns out to be invalid after all,
! this is fixed up by reload in any case. */
! if ((base && REGNO (base) == ARG_POINTER_REGNUM)
! || (indx && REGNO (indx) == ARG_POINTER_REGNUM))
! ;
!
! else if (INTVAL (disp) < 0 || INTVAL (disp) >= 4096)
! return FALSE;
}
/* In the small-PIC case, the linker converts @GOT12
Mit freundlichen Gruessen / Best Regards
Ulrich Weigand
--
Dr. Ulrich Weigand
Linux for S/390 Design & Development
IBM Deutschland Entwicklung GmbH, Schoenaicher Str. 220, 71032 Boeblingen
Phone: +49-7031/16-3727 --- Email: Ulrich.Weigand@de.ibm.com