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Re: Proposed doc update for Explicit Reg Vars 3/3
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: Jeff Law <law at redhat dot com>
- Cc: Andrew Haley <aph at redhat dot com>, David Wohlferd <dw at LimeGreenSocks dot com>, "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>, Sandra Loosemore <sandra at codesourcery dot com>
- Date: Tue, 20 Oct 2015 12:11:48 -0500
- Subject: Re: Proposed doc update for Explicit Reg Vars 3/3
- Authentication-results: sourceware.org; auth=none
- References: <561C3DAE dot 8050505 at LimeGreenSocks dot com> <5625CF7E dot 5010003 at redhat dot com> <20151020151312 dot GB25514 at gate dot crashing dot org> <56266519 dot 8070104 at redhat dot com> <56266630 dot 2050800 at redhat dot com> <562667FF dot 5000003 at redhat dot com> <562668B5 dot 6040404 at redhat dot com> <56266A5D dot 80809 at redhat dot com>
On Tue, Oct 20, 2015 at 10:22:53AM -0600, Jeff Law wrote:
> bz21182 has a testcase that's still helped by local register variables.
I tried it out, and it now is much worse *with* the reg vars than
without (and -O2 vs. -O3 makes no difference at all). It doesn't look
to have used the pre-determined allocation at all. The difference at
expand time is huge already; maybe some things weren't optimised at
tree level with the register vars? It's a bit big to really look into ;-)
Segher