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Re: [AArch64] Fix for gcc-7 regression PR 80530
- From: Jakub Jelinek <jakub at redhat dot com>
- To: "Richard Earnshaw (lists)" <Richard dot Earnshaw at arm dot com>
- Cc: gcc-patches <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 27 Apr 2017 15:26:54 +0200
- Subject: Re: [AArch64] Fix for gcc-7 regression PR 80530
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- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Thu, Apr 27, 2017 at 01:32:11PM +0100, Richard Earnshaw (lists) wrote:
> This patch fixes the regression caused by the changes to add square root
> estimation when compiling for xgene-1 or exynos-m1 targets.
>
> The issue is that the expand path for the reciprocal estimate square
> root pattern assumes that pattern cannot fail once it has been decided
> that this expansion path is available, but because the logic deep inside
> aarch64_emit_approx_sqrt() differs from use_rsqrt_p() the two disagree
> as to what is safe.
>
> This patch refactors the logic to ensure that we cannot unknowingly make
> different choices here.
>
> Bootstrap/testing completed ok. I'll apply this to trunk.
>
> Jakub: Are we having an RC2? If so, is this ok for the gcc-7 branch?
>
> PR target/80530
> * config/aarch64/aarch64.c (aarch64_emit_approx_sqrt): Ensure
> that the logic for permitting reciprocal estimates matches that
> in use_rsqrt_p.
No testcase?
We will have RC2 (later today or tomorrow), so I guess this is ok if you
believe it is important enough to have in 7.1 and very low risk.
Jakub