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Re: Proposed doc update for Explicit Reg Vars 3/3
- From: Andrew Haley <aph at redhat dot com>
- To: Jeff Law <law at redhat dot com>, Segher Boessenkool <segher at kernel dot crashing dot org>
- Cc: 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 17:05:04 +0100
- 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>
On 10/20/2015 05:00 PM, Jeff Law wrote:
> But the technical reality is I can't see a use outside the extended asm.
I can. In the past (and probably still today) GCC did an awful job of
allocating registers in a large function. This was visible in a
bytecode interpreter, where the programmer knows that the virtual PC
and SP should live in a register. GCC does not know this and is
forever spilling them. Explicit local reg vars fixed this nicely.