linux-kernel - Re: [PATCH] Kconfig: eradicate CC_HAS_ASM

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Date:   Fri, 19 Aug 2022 11:45:54 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        linux-kbuild@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-um@...ts.infradead.org,
        kvm@...r.kernel.org, llvm@...ts.linux.dev,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Subject: Re: [PATCH] Kconfig: eradicate CC_HAS_ASM_GOTO

On Fri, Aug 19, 2022 at 10:01 AM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> diff --git a/arch/x86/include/asm/rmwcc.h b/arch/x86/include/asm/rmwcc.h
> index 8a9eba191516..c82f1b334207 100644
> --- a/arch/x86/include/asm/rmwcc.h
> +++ b/arch/x86/include/asm/rmwcc.h
> @@ -11,9 +11,7 @@
>
>  #define __CLOBBERS_MEM(clb...) "memory", ## clb
>
> -#if !defined(__GCC_ASM_FLAG_OUTPUTS__) && defined(CONFIG_CC_HAS_ASM_GOTO)
> -
> -/* Use asm goto */
> +#ifndef __GCC_ASM_FLAG_OUTPUTS__
>
>  #define __GEN_RMWcc(fullop, _var, cc, clobbers, ...)                   \
>  ({                                                                     \
> @@ -27,21 +25,6 @@ cc_label:    c = true;                                               \
>         c;                                                              \
>  })
>
> -#else /* defined(__GCC_ASM_FLAG_OUTPUTS__) || !defined(CONFIG_CC_HAS_ASM_GOTO) */
> -
> -/* Use flags output or a set instruction */
> -
> -#define __GEN_RMWcc(fullop, _var, cc, clobbers, ...)                   \
> -({                                                                     \
> -       bool c;                                                         \
> -       asm volatile (fullop CC_SET(cc)                                 \
> -                       : [var] "+m" (_var), CC_OUT(cc) (c)             \
> -                       : __VA_ARGS__ : clobbers);                      \
> -       c;                                                              \
> -})
> -
> -#endif /* defined(__GCC_ASM_FLAG_OUTPUTS__) || !defined(CONFIG_CC_HAS_ASM_GOTO) */
> -

^ probably don't want to remove the terminal endif. Will respin based
on feedback from Masahiro + Alexei.


-- 
Thanks,
~Nick Desaulniers