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AJvYcCUBMuZyDzWNqGoQv/NJ7l1THQquNzHMIoPKlxOaXkvb5CPGPPXUglv5rRN5iDWsNWw9CCb/VhV/CkODrVknu1GuNgTOhgfidGUTTHic X-Gm-Message-State: AOJu0YwQTGlX9d276HesYzFUEz1zoDgJk8Z+gNm3X3v10dMSEPAErFfu fqYmBf35HnYPizdtSc9F46fkhMW8ewi9gxVCBd+iM7eorBNuYSM= X-Received: by 2002:a5d:604d:0:b0:33d:3566:b5c8 with SMTP id j13-20020a5d604d000000b0033d3566b5c8mr501780wrt.13.1710435448551; Thu, 14 Mar 2024 09:57:28 -0700 (PDT) Received: from localhost.localdomain ([46.53.249.38]) by smtp.gmail.com with ESMTPSA id a26-20020a5d457a000000b0033e7e9c8657sm1142177wrc.45.2024.03.14.09.57.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Mar 2024 09:57:27 -0700 (PDT) From: Alexey Dobriyan To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com Cc: x86@kernel.org, linux-kernel@vger.kernel.org, hpa@zytor.com, adobriyan@gmail.com Subject: [PATCH 1/1] x86_64: cleanup memset16(), memset32(), memset64() Date: Thu, 14 Mar 2024 19:57:15 +0300 Message-ID: <20240314165715.31831-1-adobriyan@gmail.com> X-Mailer: git-send-email 2.43.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit * use "+" constraint modifier, simplify inputs and output lists, delete dummy variables with meaningless names, "&" only makes sense in complex assembly creating constraints on intermediate registers. But 1 instruction assemblies don't have inner body so to speak. * write "rep stos*" on one line: Rep prefix is integral part of x86 instruction. I'm not sure why people separate "rep" with newline or semicolon pretending rep is separate instruction. It is not and never was. * use __auto_type for maximum copy pasta experience, * reformat a bit to make everything looks nicer. Note that "memory" clobber is too much if "n" is known at compile time. However, "=m" (*(T(*)[n])s) doesn't work because -Wvla even if "n" is compile time constant: if (BCP(n)) { rep stos : "=m" (*(T(*)[n])s) } else { rep stosw : "memory" } The above doesn't work. Signed-off-by: Alexey Dobriyan --- arch/x86/include/asm/string_64.h | 45 +++++++++++++++++--------------- 1 file changed, 24 insertions(+), 21 deletions(-) diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h index 857d364b9888..9d0b324eab21 100644 --- a/arch/x86/include/asm/string_64.h +++ b/arch/x86/include/asm/string_64.h @@ -30,37 +30,40 @@ void *__memset(void *s, int c, size_t n); #define __HAVE_ARCH_MEMSET16 static inline void *memset16(uint16_t *s, uint16_t v, size_t n) { - long d0, d1; - asm volatile("rep\n\t" - "stosw" - : "=&c" (d0), "=&D" (d1) - : "a" (v), "1" (s), "0" (n) - : "memory"); - return s; + const __auto_type s0 = s; + asm volatile ( + "rep stosw" + : "+D" (s), "+c" (n) + : "a" (v) + : "memory" + ); + return s0; } #define __HAVE_ARCH_MEMSET32 static inline void *memset32(uint32_t *s, uint32_t v, size_t n) { - long d0, d1; - asm volatile("rep\n\t" - "stosl" - : "=&c" (d0), "=&D" (d1) - : "a" (v), "1" (s), "0" (n) - : "memory"); - return s; + const __auto_type s0 = s; + asm volatile ( + "rep stosl" + : "+D" (s), "+c" (n) + : "a" (v) + : "memory" + ); + return s0; } #define __HAVE_ARCH_MEMSET64 static inline void *memset64(uint64_t *s, uint64_t v, size_t n) { - long d0, d1; - asm volatile("rep\n\t" - "stosq" - : "=&c" (d0), "=&D" (d1) - : "a" (v), "1" (s), "0" (n) - : "memory"); - return s; + const __auto_type s0 = s; + asm volatile ( + "rep stosq" + : "+D" (s), "+c" (n) + : "a" (v) + : "memory" + ); + return s0; } #endif -- 2.43.2