linux-kernel - Re: [PATCH -tip] x86: Remove code depending on __GCC_ASM_FLAG_OUTPUTS_

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Message-ID: <20250905121723.GCaLrU04lP2A50PT-B@fat_crate.local>
Date: Fri, 5 Sep 2025 14:17:23 +0200
From: Borislav Petkov <bp@...en8.de>
To: Uros Bizjak <ubizjak@...il.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH -tip] x86: Remove code depending on
 __GCC_ASM_FLAG_OUTPUTS__

On Thu, Aug 28, 2025 at 09:29:29AM +0200, Uros Bizjak wrote:
> diff --git a/arch/x86/include/asm/cmpxchg_32.h b/arch/x86/include/asm/cmpxchg_32.h
> index 371f7906019e..1f80a62be969 100644
> --- a/arch/x86/include/asm/cmpxchg_32.h
> +++ b/arch/x86/include/asm/cmpxchg_32.h
> @@ -46,8 +46,7 @@ static __always_inline u64 __cmpxchg64_local(volatile u64 *ptr, u64 old, u64 new
>  	bool ret;							\
>  									\
>  	asm_inline volatile(_lock "cmpxchg8b %[ptr]"			\
> -		     CC_SET(e)						\
> -		     : CC_OUT(e) (ret),					\
> +		     : "=@ccz" (ret),					\

Any particular reason you're not using =@cce here?

I know, they're equivalent but why then switch to =@...?

-- 
Regards/Gruss,
    Boris.

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