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Re: Proposed doc update for Explicit Reg Vars 3/3
- From: Jeff Law <law at redhat dot com>
- To: Andrew Haley <aph 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 10:22:53 -0600
- 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>
On 10/20/2015 10:15 AM, Andrew Haley wrote:
But in that case, what do we guarantee.
We certainly don't guarantee that those objects will be in their
requested register at any point other than at the asm statements.
OK, but this usage did work in the past: that it now doesn't is a
regression. GCC was quite useful (unique, really) in that it provided
a way to write a decent bytecode interpreter in a HLL. The world has
lost something significant if this no longer works.
It still works, but again, it's not a guarantee, never has been.
bz21182 has a testcase that's still helped by local register variables.