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Re: [PATCH][AArch64] Remove aarch64_frame_pointer_required
- From: Richard Sandiford <richard dot sandiford at arm dot com>
- To: Wilco Dijkstra <Wilco dot Dijkstra at arm dot com>
- Cc: James Greenhalgh <James dot Greenhalgh at arm dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Richard Earnshaw <Richard dot Earnshaw at arm dot com>, Ramana Radhakrishnan <Ramana dot Radhakrishnan at arm dot com>, nd <nd at arm dot com>
- Date: Mon, 12 Mar 2018 14:27:24 +0000
- Subject: Re: [PATCH][AArch64] Remove aarch64_frame_pointer_required
- Authentication-results: sourceware.org; auth=none
- References: <DB6PR0801MB205392DA3F942C111AD4572783B60@DB6PR0801MB2053.eurprd08.prod.outlook.com> <20171107170512.GA30919@arm.com> <87muzryjs7.fsf@e105548-lin.cambridge.arm.com> <HE1PR0801MB20589082137557C489367ACE83C60@HE1PR0801MB2058.eurprd08.prod.outlook.com>
Wilco Dijkstra <Wilco.Dijkstra@arm.com> writes:
> Richard Sandiford wrote:
>> But there's the third question of whether the frame pointer is available
>> for general allocation. By removing frame_pointer_required, we're saying
>> that the frame pointer is always available for general use.
>
> Unlike on ARM/Thumb-2, the frame pointer is unfortunately never available for
> general allocation on AArch64 - so we cannot use it for something
> actually useful.
> A while back there were mid-end patches proposed to allow general allocation
> of FP but those weren't accepted.
Ah, missed that, sorry. So the asm example I gave probably is as far as
the "problem" goes, and the argument can be made that that's just doing
what the user asked for.
Sorry for the noise...
Richard