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RE: [PATCH] xtensa: fix access to the last pseudo register
- From: Marc Gauthier <marc at cadence dot com>
- To: Max Filippov <jcmvbkbc at gmail dot com>, Pedro Alves <palves at redhat dot com>
- Cc: "gdb-patches at sourceware dot org" <gdb-patches at sourceware dot org>, Maxim Grigoriev <maxim2405 at gmail dot com>, Woody LaRue <larue at cadence dot com>
- Date: Wed, 27 May 2015 15:12:54 +0000
- Subject: RE: [PATCH] xtensa: fix access to the last pseudo register
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Max Filippov wrote:
[...]
> I'm removing that aliasing to expose the last pseudoregister.
> After that patch fp pseudo register still exists and it is a read only
> alias
> for a1. I don't think that's right, because normally frame pointer is a7
> or
> a15, depending on ABI, but that's definitely a separate question.
If the compiler allocated a frame pointer for the function, it is
a7 or a15 according to ABI, correct. If no separate pointer is
allocated (usually when no variable stack allocation such as alloca
or similar is used in the function), I believe a1 is effectively
both the stack pointer and the frame pointer.
-Marc