MIPS: microMIPS: Optimise 'strlen' core library function.

Optimise 'strlen' 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 <Steven.Hill@imgtec.com>

arch/mips/lib/strlen_user.S

@@ -3,8 +3,9 @@
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  *
- * Copyright (c) 1996, 1998, 1999, 2004 by Ralf Baechle
- * Copyright (c) 1999 Silicon Graphics, Inc.
+ * Copyright (C) 1996, 1998, 1999, 2004 by Ralf Baechle
+ * Copyright (C) 1999 Silicon Graphics, Inc.
+ * Copyright (C) 2011 MIPS Technologies, Inc.
  */
 #include <asm/asm.h>
 #include <asm/asm-offsets.h>
@@ -28,9 +29,9 @@ LEAF(__strlen_user_asm)
 
 FEXPORT(__strlen_user_nocheck_asm)
 	move		v0, a0
-1:	EX(lb, t0, (v0), .Lfault)
+1:	EX(lbu, v1, (v0), .Lfault)
 	PTR_ADDIU	v0, 1
-	bnez		t0, 1b
+	bnez		v1, 1b
 	PTR_SUBU	v0, a0
 	jr		ra
 	END(__strlen_user_asm)