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[PATCH 2/4] MIPS: Optimise core library function 'strncpy' for microMIPS

To: linux-mips@linux-mips.org, ralf@linux-mips.org
Subject: [PATCH 2/4] MIPS: Optimise core library function 'strncpy' for microMIPS.
From: "Steven J. Hill" <sjhill@mips.com>
Date: Thu, 24 May 2012 15:55:40 -0500
Cc: "Steven J. Hill" <sjhill@mips.com>
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From: "Steven J. Hill" <sjhill@mips.com>

Optimise 'strncpy' to use microMIPS instructions and/or optimisations
for binary size reduction. When the microMIPS ISA is not being used,
the library function compiles to the original binary code.

Signed-off-by: Steven J. Hill <sjhill@mips.com>
---
 arch/mips/lib/strncpy_user.S |   28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/arch/mips/lib/strncpy_user.S b/arch/mips/lib/strncpy_user.S
index 7201b2f..dea9304 100644
--- a/arch/mips/lib/strncpy_user.S
+++ b/arch/mips/lib/strncpy_user.S
@@ -3,7 +3,8 @@
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  *
- * Copyright (c) 1996, 1999 by Ralf Baechle
+ * Copyright (C) 1996, 1999 by Ralf Baechle
+ * Copyright (C) 2011 MIPS Technologies, Inc.
  */
 #include <linux/errno.h>
 #include <asm/asm.h>
@@ -33,22 +34,23 @@ LEAF(__strncpy_from_user_asm)
        bnez            v0, .Lfault
 
 FEXPORT(__strncpy_from_user_nocheck_asm)
-       move            v0, zero
-       move            v1, a1
        .set            noreorder
-1:     EX(lbu, t0, (v1), .Lfault)
+       move            t0, zero
+       move            v1, a1
+1:     EX(lbu, v0, (v1), .Lfault)
        PTR_ADDIU       v1, 1
        R10KCBARRIER(0(ra))
-       beqz            t0, 2f
-        sb             t0, (a0)
-       PTR_ADDIU       v0, 1
-       .set            reorder
-       PTR_ADDIU       a0, 1
-       bne             v0, a2, 1b
-2:     PTR_ADDU        t0, a1, v0
-       xor             t0, a1
-       bltz            t0, .Lfault
+       beqz            v0, 2f
+        sb             v0, (a0)
+       PTR_ADDIU       t0, 1
+       bne             t0, a2, 1b
+        PTR_ADDIU      a0, 1
+2:     PTR_ADDU        v0, a1, t0
+       xor             v0, a1
+       bltz            v0, .Lfault
+        nop
        jr              ra                      # return n
+       move            v0, t0
        END(__strncpy_from_user_asm)
 
 .Lfault:       li              v0, -EFAULT
-- 
1.7.10


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