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Re: GVN-PRE sucks -- well, for SPECCFP2000 mgrid anyway
- From: Mark Mitchell <mark at codesourcery dot com>
- To: Daniel Berlin <dberlin at dberlin dot org>
- Cc: Steven Bosscher <stevenb at suse dot de>, gcc at gcc dot gnu dot org, Kenneth Zadeck <zadeck at naturalbridge dot com>
- Date: Sun, 15 Aug 2004 17:05:51 -0700
- Subject: Re: GVN-PRE sucks -- well, for SPECCFP2000 mgrid anyway
- Organization: CodeSourcery, LLC
- References: <200408151321.07846.stevenb@suse.de> <A9F086BE-EEC3-11D8-B6DD-000A95DA505C@dberlin.org>
Daniel Berlin wrote:
Yeah.
I'll see if i can come up with some simple heuristics that help here,
without hurting anything else too much.
I wonder if it's better to restrain PRE, or let it go ahead, and then
have the register allocator move computations back into the loop.
I've copied Kenny here to see if he happens to know of any magic bullets
for this kind of thing.
(Kenny, the issue is that PRE is pulling so much stuff out of loops that
we get register pressure, and hence bad code.)
--
Mark Mitchell
CodeSourcery, LLC
(916) 791-8304
mark@codesourcery.com