R12 is callee-saved for A- and R- class interrupt handlers

[Oliver Stannard]

Committed as r201089.

Oliver

-----Original Message-----
From: Tim Northover [mailto:t.p.northover at gmail.com]
Sent: 10 February 2014 14:25
To: Oliver Stannard
Cc: LLVM Commits
Subject: Re: R12 is callee-saved for A- and R- class interrupt handlers

> For v7A and v7R, r12 must be callee-saved by interrupt handlers. This is
> because it is the intra-procedure-call scratch register, which may be
> clobbered by any branch subject to a relocation supporting interworking or
> long branches (AAPCS, 5.3.1.1, “Use of IP by the linker”). R12 may be used
> as a temporary register between function calls, so it must be preserved by
> an interrupt handler. It seems that this is mostly implemented, but there
> was a bug in the prologue/epilogue generator which prevented it from being
> included in the push and pop instructions. The attached patch fixes this.

Looks good to me! Thanks for that.

Tim.


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