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Message-ID: <87tufljlmv.fsf@oldenburg.str.redhat.com>
Date: Tue, 07 Dec 2021 01:37:12 +0100
From: Florian Weimer <fweimer@...hat.com>
To: Stijn Tintel <stijn@...ux-ipv6.be>
Cc: musl@...ts.openwall.com
Subject: Re: [PATCH] ppc64: check for AltiVec in setjmp/longjmp
* Stijn Tintel:
> diff --git a/src/setjmp/powerpc64/setjmp.s b/src/setjmp/powerpc64/setjmp.s
> index 37683fda..32853693 100644
> --- a/src/setjmp/powerpc64/setjmp.s
> +++ b/src/setjmp/powerpc64/setjmp.s
> @@ -69,7 +69,17 @@ __setjmp_toc:
> stfd 30, 38*8(3)
> stfd 31, 39*8(3)
>
> - # 5) store vector registers v20-v31
> + # 5) store vector registers v20-v31 if hardware supports AltiVec
> + mflr 0
> + bl 1f
> + .hidden __hwcap
> + .long __hwcap-.
> +1: mflr 4
This de-balances the return stack and probably has quite severe
performance impact. The ISA manual says to use
bcl 20,31,$+4
and you'll have to store the __hwcap offset somewhere else.
Thanks,
Florian
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