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Tue, 12 May 2026 07:10:19 -0700 (PDT) Received: from RTRKW671-LIN.domain.local ([77.243.27.125]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48e8e568b04sm40557965e9.0.2026.05.12.07.10.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 May 2026 07:10:19 -0700 (PDT) From: Milan Tripkovic To: Paul Walmsley , Palmer Dabbelt , Albert Ou Cc: Alexandre Ghiti , Dusan Stojkovic , Milan Tripkovic , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Milan Tripkovic Subject: [PATCH 1/2] riscv: lib: add memcmp() implementation Date: Tue, 12 May 2026 16:10:06 +0200 Message-ID: <20260512141007.1193033-1-milant2002@gmail.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260512_071023_600929_A194BBA4 X-CRM114-Status: GOOD ( 15.46 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org From: Milan Tripkovic Add an assembly implementation of memcmp() for RISC-V. The implementation uses the ZBB extension for word-at-a-time comparison and an assembly fallback for non-ZBB systems. Benchmark results (QEMU TCG, rv64): Len | Def | NoZBB | ZBB | %NoZBB | %ZBB -----|-------|-------|-------|--------|------- 1 B | 22.4 | 24.6 | 23.2 | +9.8% | +3.5% 7 B | 96.9 | 108.5 | 107.3 | +12.0% | +10.7% 8 B | 107.0 | 116.3 | 176.7 | +8.7% | +65.1% 16 B | 148.4 | 172.8 | 315.6 | +16.4% | +112.6% 31 B | 182.2 | 217.1 | 377.6 | +19.2% | +107.2% 64 B | 220.6 | 239.4 | 874.2 | +8.5% | +296.2% 127 B| 213.7 | 254.8 | 1042.9| +19.2% | +388.0% 512 B| 255.1 | 269.0 | 1778.6| +5.4% | +597.2% 1024B| 252.3 | 280.9 | 1887.7| +11.3% | +648.1% 3173B| 241.3 | 288.7 | 2063.2| +19.6% | +755.0% 4096B| 240.9 | 280.5 | 2064.5| +16.4% | +756.9% Signed-off-by: Milan Tripkovic --- arch/riscv/include/asm/string.h | 2 + arch/riscv/lib/Makefile | 1 + arch/riscv/lib/memcmp.S | 103 ++++++++++++++++++++++++++++++++ arch/riscv/purgatory/Makefile | 5 +- 4 files changed, 110 insertions(+), 1 deletion(-) create mode 100644 arch/riscv/lib/memcmp.S diff --git a/arch/riscv/include/asm/string.h b/arch/riscv/include/asm/string.h index 764ffe8f6..5c5299678 100644 --- a/arch/riscv/include/asm/string.h +++ b/arch/riscv/include/asm/string.h @@ -18,6 +18,8 @@ extern asmlinkage void *__memcpy(void *, const void *, size_t); #define __HAVE_ARCH_MEMMOVE extern asmlinkage void *memmove(void *, const void *, size_t); extern asmlinkage void *__memmove(void *, const void *, size_t); +#define __HAVE_ARCH_MEMCMP +extern asmlinkage int memcmp(const void *, const void *, size_t); #if !(defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) #define __HAVE_ARCH_STRCMP diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile index 6f767b2a3..b529e1be1 100644 --- a/arch/riscv/lib/Makefile +++ b/arch/riscv/lib/Makefile @@ -3,6 +3,7 @@ lib-y += delay.o lib-y += memcpy.o lib-y += memset.o lib-y += memmove.o +lib-y += memcmp.o ifeq ($(CONFIG_KASAN_GENERIC)$(CONFIG_KASAN_SW_TAGS),) lib-y += strcmp.o lib-y += strlen.o diff --git a/arch/riscv/lib/memcmp.S b/arch/riscv/lib/memcmp.S new file mode 100644 index 000000000..444b082d9 --- /dev/null +++ b/arch/riscv/lib/memcmp.S @@ -0,0 +1,103 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ + +#include +#include +#include +#include + +/* int memcmp(const void *cs, const void *ct, size_t n) */ +SYM_FUNC_START(memcmp) + + __ALTERNATIVE_CFG("nop", "j memcmp_zbb", 0, RISCV_ISA_EXT_ZBB, + IS_ENABLED(CONFIG_RISCV_ISA_ZBB) && IS_ENABLED(CONFIG_TOOLCHAIN_HAS_ZBB)) +/* + * Parameters + * a0 - Pointer to first memory block (cs), also return value + * a1 - Pointer to second memory block (ct) + * a2 - Number of bytes to compare (n), transformed to end pointer (a0 + n) + * + * Returns + * a0 - 0 if equal, positive if cs > ct, negative if cs < ct + * + * Clobbers + * t0, t1 + */ + beqz a2, 2f + add a2, a0, a2 +1: + lbu t0, 0(a0) + lbu t1, 0(a1) + bne t0, t1, 3f + addi a0, a0, 1 + addi a1, a1, 1 + bne a0, a2, 1b +2: + li a0, 0 + ret +3: + sub a0, t0, t1 + ret + + +memcmp_zbb: +.option push +.option arch,+zbb +/* + * Parameters + * a0 - Pointer to first memory block (cs), also return value + * a1 - Pointer to second memory block (ct) + * a2 - Number of bytes to compare (n), decremented during loop + * + * Returns + * a0 - 0 if equal, positive if cs > ct, negative if cs < ct + * + * Clobbers + * t0, t1, t2 + */ + beq a0, a1, 4f + + li t0, SZREG + bltu a2, t0, 5f + +1: + REG_L t1, 0(a0) + REG_L t2, 0(a1) + bne t1, t2, 2f + + addi a0, a0, SZREG + addi a1, a1, SZREG + addi a2, a2, -SZREG + bgeu a2, t0, 1b + +5: + beqz a2, 4f +6: + lbu t1, 0(a0) + lbu t2, 0(a1) + bne t1, t2, 3f + addi a0, a0, 1 + addi a1, a1, 1 + addi a2, a2, -1 + bnez a2, 6b + +4: li a0, 0 + ret +2: +#ifndef CONFIG_CPU_BIG_ENDIAN + rev8 t1, t1 + rev8 t2, t2 +#endif + sltu a0, t2, t1 + sltu t0, t1, t2 + sub a0, a0, t0 + ret + +3: + sub a0, t1, t2 + ret + +.option pop + +SYM_FUNC_END(memcmp) +SYM_FUNC_ALIAS(__pi_memcmp, memcmp) +EXPORT_SYMBOL(memcmp) diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile index b0358a78f..456929971 100644 --- a/arch/riscv/purgatory/Makefile +++ b/arch/riscv/purgatory/Makefile @@ -1,6 +1,6 @@ # SPDX-License-Identifier: GPL-2.0 -purgatory-y := purgatory.o sha256.o entry.o string.o ctype.o memcpy.o memset.o +purgatory-y := purgatory.o sha256.o entry.o string.o ctype.o memcpy.o memset.o memcmp.o ifeq ($(CONFIG_KASAN_GENERIC)$(CONFIG_KASAN_SW_TAGS),) purgatory-y += strcmp.o strlen.o strncmp.o strnlen.o strchr.o strrchr.o endif @@ -41,6 +41,9 @@ $(obj)/strchr.o: $(srctree)/arch/riscv/lib/strchr.S FORCE $(obj)/strrchr.o: $(srctree)/arch/riscv/lib/strrchr.S FORCE $(call if_changed_rule,as_o_S) +$(obj)/memcmp.o: $(srctree)/arch/riscv/lib/memcmp.S FORCE + $(call if_changed_rule,as_o_S) + CFLAGS_sha256.o := -D__DISABLE_EXPORTS -D__NO_FORTIFY CFLAGS_string.o := -D__DISABLE_EXPORTS CFLAGS_ctype.o := -D__DISABLE_EXPORTS -- 2.43.0 _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv