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From:   zhangfei <zhang_fei_0403@163.com>
To:     ajones@ventanamicro.com
Cc:     aou@eecs.berkeley.edu, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org, palmer@dabbelt.com,
        paul.walmsley@sifive.com, zhangfei@nj.iscas.ac.cn
Subject: [PATCH 2/2] riscv: Optimize memset
Date:   Tue,  9 May 2023 10:22:06 +0800
Message-Id: <20230509022207.3700-2-zhang_fei_0403@163.com>
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 <20230509022207.3700-1-zhang_fei_0403@163.com>
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From: zhangfei <zhangfei@nj.iscas.ac.cn>

This patch has been optimized for memset data sizes less than 16 bytes.
Compared to byte by byte storage, significant performance improvement has been achieved.

Signed-off-by: Fei Zhang <zhangfei@nj.iscas.ac.cn>
---
 arch/riscv/lib/memset.S | 33 ++++++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/lib/memset.S b/arch/riscv/lib/memset.S
index e613c5c27998..6113a2696e79 100644
--- a/arch/riscv/lib/memset.S
+++ b/arch/riscv/lib/memset.S
@@ -106,9 +106,36 @@ WEAK(memset)
 	beqz	a2, 6f
 	add	a3, t0, a2
 5:
-	sb	a1, 0(t0)
-	addi	t0, t0, 1
-	bltu	t0, a3, 5b
+       sb      a1,  0(t0)
+       sb      a1, -1(a3)
+       li      a4, 2
+       bgeu    a4, a2, 6f
+
+       sb 	a1,  1(t0)
+       sb 	a1,  2(t0)
+       sb 	a1, -2(a3)
+       sb 	a1, -3(a3)
+       li 	a4, 6
+       bgeu 	a4, a2, 6f
+
+       sb 	a1,  3(t0)
+       sb 	a1, -4(a3)
+       li 	a4, 8
+       bgeu    a4, a2, 6f
+
+       sb 	a1,  4(t0)
+       sb 	a1, -5(a3)
+       li 	a4, 10
+       bgeu 	a4, a2, 6f
+
+       sb 	a1,  5(t0)
+       sb 	a1,  6(t0)
+       sb 	a1, -6(a3)
+       sb 	a1, -7(a3)
+       li 	a4, 14
+       bgeu 	a4, a2, 6f
+
+       sb 	a1, 7(t0)
 6:
 	ret
 END(__memset)
-- 
2.33.0