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Re: [PATCH] bitops.h: Compile out asserts without --enable-debug


From: Peter Maydell
Subject: Re: [PATCH] bitops.h: Compile out asserts without --enable-debug
Date: Mon, 22 May 2023 10:16:25 +0100

On Sat, 20 May 2023 at 21:55, BALATON Zoltan <balaton@eik.bme.hu> wrote:
>
> The low level extract and deposit funtions provided by bitops.h are
> used in performance critical places. It crept into target/ppc via
> FIELD_EX64 and also used by softfloat so PPC code using a lot of FPU
> where hardfloat is also disabled is doubly affected.
>
> Normally asserts should be compiled out from release builds with
> -DNDEBUG but that cannot be used in QEMU because some places still
> rely on asserts instead of proper error checking. To resolve this,
> compile out asserts from deposit/extract functions in optimised builds
> which improves performance for target/ppc and possibly others too.

Can we have some figures for performance improvements,
please? General QEMU policy is that asserts remain,
even in non-debug builds, so exceptions from that policy
should come with justification with figures attached.

thanks
-- PMM



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