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[Bug rtl-optimization/23837] [4.0/4.1 regression] Wrong code with -fschedule-insns
- From: "amylaar at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 20 Sep 2005 20:52:15 -0000
- Subject: [Bug rtl-optimization/23837] [4.0/4.1 regression] Wrong code with -fschedule-insns
- References: <20050912190132.23837.debian-gcc@lists.debian.org>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From amylaar at gcc dot gnu dot org 2005-09-20 20:52 -------
(In reply to comment #3)
> A regression hunt on i686-linux showed the failure starting with this patch
> from amylaar@gcc.gnu.org:
>
> http://gcc.gnu.org/ml/gcc-cvs/2005-05/msg00640.html
The i386.md x86_shrd_1 pattern is bogus, is should use lshiftrt,
not ashiftrt. However, that is not the reason for this regression.
The reason is that we have a bogus REG_NO_CONFLICT block. The generic
rotate expander expects emit_no_conflict_block to re-order its instructions,
but that is now suppresed by a match between clobbers of the flags register.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23837