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Subject: Re: [PATCH 06/10] powerpc: remove GCC version check for UPD_CONSTR
To:     Nick Desaulniers <ndesaulniers@google.com>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Joe Perches <joe@perches.com>, Arnd Bergmann <arnd@kernel.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>, llvm@lists.linux.dev,
        linux-kernel@vger.kernel.org,
        Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Segher Boessenkool <segher@kernel.crashing.org>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        linuxppc-dev@lists.ozlabs.org
References: <20210910234047.1019925-1-ndesaulniers@google.com>
 <20210910234047.1019925-7-ndesaulniers@google.com>
From:   Nathan Chancellor <nathan@kernel.org>
Message-ID: <b940bd2c-21d2-dfe9-e171-e265085a2b11@kernel.org>
Date:   Fri, 10 Sep 2021 16:48:20 -0700
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On 9/10/2021 4:40 PM, Nick Desaulniers wrote:
> Now that GCC 5.1 is the minimum supported version, we can drop this
> workaround for older versions of GCC. This adversely affected clang,
> too.
> 
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Segher Boessenkool <segher@kernel.crashing.org>
> Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
> Cc: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
>   arch/powerpc/include/asm/asm-const.h | 10 ----------
>   1 file changed, 10 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/asm-const.h b/arch/powerpc/include/asm/asm-const.h
> index 0ce2368bd20f..dbfa5e1e3198 100644
> --- a/arch/powerpc/include/asm/asm-const.h
> +++ b/arch/powerpc/include/asm/asm-const.h
> @@ -12,16 +12,6 @@
>   #  define ASM_CONST(x)		__ASM_CONST(x)
>   #endif
>   
> -/*
> - * Inline assembly memory constraint
> - *
> - * GCC 4.9 doesn't properly handle pre update memory constraint "m<>"
> - *
> - */
> -#if defined(GCC_VERSION) && GCC_VERSION < 50000
> -#define UPD_CONSTR ""
> -#else
>   #define UPD_CONSTR "<>"
> -#endif

The only reason this exists is because of commit 592bbe9c505d 
("powerpc/uaccess: Don't use "m<>" constraint with GCC 4.9"). It is 
probably just worth sinking "<>" into all of the callsites and removing
UPD_CONSTR.

>   
>   #endif /* _ASM_POWERPC_ASM_CONST_H */
>