linux-kernel - Re: [PATCH 2/2] selftests/fpu: Add an FPU selftest

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Message-ID: <20200623191336.GK32590@zn.tnic>
Date:   Tue, 23 Jun 2020 21:13:36 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        jpa@...nelbug.mail.kapsi.fi, Dave Hansen <dave.hansen@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] selftests/fpu: Add an FPU selftest

On Tue, Jun 23, 2020 at 12:07:13PM -0700, Nick Desaulniers wrote:
> You already have a conditional below for CC_IS_GCC; just add an else
> and unconditionally add -msse2.  You *should* use -msse2 for GCC 7.1+
> IMO.

Why if one can write it more compact with cc-option?

FPU_CFLAGS += $(call cc-option,-msse2,)

> Note that Clang has -mstack-alignment=8 whereas GCC has
> -mpreferred-stack-boundary=3.  (Clang is a value in bytes, GCC is 2^X
> bytes)

Sure, the stack boundary setting is GCC only.

> I recommend a version check for GCC < 7.1, or simply disabling the
> self test if the version of GCC used is older than 7.1.

See Andy's suggestion upthread.

And I agree too that using cc-option is better than simply tying it to a
compiler version. Who knows what compiler has what backported. In such
cases a version number means nothing.

> ^ looks familiar ;)

It has been pasted around the kernel, I came to realize today. :-)

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette