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Peter Anvin" To: Uros Bizjak , x86@kernel.org, linux-kernel@vger.kernel.org CC: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , torvalds@linux-foundation.org Subject: Re: [PATCH -tip 1/3] x86/asm/32: Modernize memset() functions User-Agent: K-9 Mail for Android In-Reply-To: <20250506165227.158932-1-ubizjak@gmail.com> References: <20250506165227.158932-1-ubizjak@gmail.com> Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On May 6, 2025 9:52:06 AM PDT, Uros Bizjak wrote: >Use inout "+" constraint modifier where appropriate and declare >temporary variable using __auto_type, similar to what x86_64 does=2E > >No functional changes intended=2E > >Signed-off-by: Uros Bizjak >Cc: Thomas Gleixner >Cc: Ingo Molnar >Cc: Borislav Petkov >Cc: Dave Hansen >Cc: "H=2E Peter Anvin" >--- > arch/x86/include/asm/string_32=2Eh | 24 ++++++++++++------------ > 1 file changed, 12 insertions(+), 12 deletions(-) > >diff --git a/arch/x86/include/asm/string_32=2Eh b/arch/x86/include/asm/st= ring_32=2Eh >index e9cce169bb4c=2E=2E9152d2c0f60e 100644 >--- a/arch/x86/include/asm/string_32=2Eh >+++ b/arch/x86/include/asm/string_32=2Eh >@@ -164,12 +164,12 @@ extern void *memchr(const void *cs, int c, size_t c= ount); >=20 > static inline void *__memset_generic(void *s, char c, size_t count) > { >- int d0, d1; >+ const __auto_type s0 =3D s; > asm volatile("rep stosb" >- : "=3D&c" (d0), "=3D&D" (d1) >- : "a" (c), "1" (s), "0" (count) >+ : "+D" (s), "+c" (count) >+ : "a" (c) > : "memory"); >- return s; >+ return s0; > } >=20 > /* we might want to write optimized versions of these later */ >@@ -197,23 +197,23 @@ extern void *memset(void *, int, size_t); > #define __HAVE_ARCH_MEMSET16 > static inline void *memset16(uint16_t *s, uint16_t v, size_t n) > { >- int d0, d1; >+ const __auto_type s0 =3D s; > asm volatile("rep stosw" >- : "=3D&c" (d0), "=3D&D" (d1) >- : "a" (v), "1" (s), "0" (n) >+ : "+D" (s), "+c" (n) >+ : "a" (v) > : "memory"); >- return s; >+ return s0; > } >=20 > #define __HAVE_ARCH_MEMSET32 > static inline void *memset32(uint32_t *s, uint32_t v, size_t n) > { >- int d0, d1; >+ const __auto_type s0 =3D s; > asm volatile("rep stosl" >- : "=3D&c" (d0), "=3D&D" (d1) >- : "a" (v), "1" (s), "0" (n) >+ : "+D" (s), "+c" (n) >+ : "a" (v) > : "memory"); >- return s; >+ return s0; > } >=20 > /* So __auto_type is spelled "auto" in newer C versions, but "auto" was a (co= mpletely useless!) keyword going all the way back to K&R C=2E Can anyone th= ink of a reason why we don't do:=20 #define auto __auto_type =2E=2E=2E and just start using the modern keyword right away?=20 -hpa