openrisc: Add optimized memset

This adds a hand-optimized assembler version of memset and sets
__HAVE_ARCH_MEMSET to use this version instead of the generic C
routine

Signed-off-by: Olof Kindgren <olof.kindgren@gmail.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

4 files changed, 107 insertions, 1 deletions

diff --git a/arch/openrisc/include/asm/string.h b/arch/openrisc/include/asm/string.h
new file mode 100644
index 000000000000..33470d4d6948
--- /dev/null
+++ b/arch/openrisc/include/asm/string.h
@@ -0,0 +1,7 @@
+#ifndef __ASM_OPENRISC_STRING_H
+#define __ASM_OPENRISC_STRING_H
+
+#define __HAVE_ARCH_MEMSET
+extern void *memset(void *s, int c, __kernel_size_t n);
+
+#endif /* __ASM_OPENRISC_STRING_H */
diff --git a/arch/openrisc/kernel/or32_ksyms.c b/arch/openrisc/kernel/or32_ksyms.c
index 86e31cf1de1d..5c4695d13542 100644
--- a/arch/openrisc/kernel/or32_ksyms.c
+++ b/arch/openrisc/kernel/or32_ksyms.c
@@ -44,3 +44,4 @@ DECLARE_EXPORT(__ashldi3);
 DECLARE_EXPORT(__lshrdi3);
 
 EXPORT_SYMBOL(__copy_tofrom_user);
+EXPORT_SYMBOL(memset);
diff --git a/arch/openrisc/lib/Makefile b/arch/openrisc/lib/Makefile
index 966f65dbc6f0..67c583e0617f 100644
--- a/arch/openrisc/lib/Makefile
+++ b/arch/openrisc/lib/Makefile
@@ -2,4 +2,4 @@
 # Makefile for or32 specific library files..
 #
 
-obj-y  = string.o delay.o
+obj-y  = memset.o string.o delay.o
diff --git a/arch/openrisc/lib/memset.S b/arch/openrisc/lib/memset.S
new file mode 100644
index 000000000000..92cc2eac26fa
--- /dev/null
+++ b/arch/openrisc/lib/memset.S
@@ -0,0 +1,98 @@
+/*
+ * OpenRISC memset.S
+ *
+ * Hand-optimized assembler version of memset for OpenRISC.
+ * Algorithm inspired by several other arch-specific memset routines
+ * in the kernel tree
+ *
+ * Copyright (C) 2015 Olof Kindgren <olof.kindgren@gmail.com>
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ */
+
+        .global memset
+        .type   memset, @function
+memset:
+        /* arguments:
+         * r3 = *s
+         * r4 = c
+         * r5 = n
+         * r13, r15, r17, r19 used as temp regs
+        */
+
+        /* Exit if n == 0 */
+        l.sfeqi         r5, 0
+        l.bf            4f
+
+        /* Truncate c to char */
+        l.andi          r13, r4, 0xff
+
+        /* Skip word extension if c is 0 */
+        l.sfeqi         r13, 0
+        l.bf            1f
+        /* Check for at least two whole words (8 bytes) */
+         l.sfleui       r5, 7
+
+        /* Extend char c to 32-bit word cccc in r13 */
+        l.slli          r15, r13, 16  // r13 = 000c, r15 = 0c00
+        l.or            r13, r13, r15 // r13 = 0c0c, r15 = 0c00
+        l.slli          r15, r13, 8   // r13 = 0c0c, r15 = c0c0
+        l.or            r13, r13, r15 // r13 = cccc, r15 = c0c0
+
+1:      l.addi          r19, r3, 0 // Set r19 = src
+        /* Jump to byte copy loop if less than two words */
+        l.bf            3f
+         l.or           r17, r5, r0 // Set r17 = n
+
+        /* Mask out two LSBs to check alignment */
+        l.andi          r15, r3, 0x3
+
+        /* lsb == 00, jump to word copy loop */
+        l.sfeqi         r15, 0
+        l.bf            2f
+         l.addi         r19, r3, 0 // Set r19 = src
+
+        /* lsb == 01,10 or 11 */
+        l.sb            0(r3), r13   // *src = c
+        l.addi          r17, r17, -1 // Decrease n
+
+        l.sfeqi         r15, 3
+        l.bf            2f
+         l.addi         r19, r3, 1  // src += 1
+
+        /* lsb == 01 or 10 */
+        l.sb            1(r3), r13   // *(src+1) = c
+        l.addi          r17, r17, -1 // Decrease n
+
+        l.sfeqi         r15, 2
+        l.bf            2f
+         l.addi         r19, r3, 2  // src += 2
+
+        /* lsb == 01 */
+        l.sb            2(r3), r13   // *(src+2) = c
+        l.addi          r17, r17, -1 // Decrease n
+        l.addi          r19, r3, 3   // src += 3
+
+        /* Word copy loop */
+2:      l.sw            0(r19), r13  // *src = cccc
+        l.addi          r17, r17, -4 // Decrease n
+        l.sfgeui        r17, 4
+        l.bf            2b
+         l.addi         r19, r19, 4  // Increase src
+
+        /* When n > 0, copy the remaining bytes, otherwise jump to exit */
+        l.sfeqi         r17, 0
+        l.bf            4f
+
+        /* Byte copy loop */
+3:      l.addi          r17, r17, -1 // Decrease n
+        l.sb            0(r19), r13  // *src = cccc
+        l.sfnei         r17, 0
+        l.bf            3b
+         l.addi         r19, r19, 1  // Increase src
+
+4:      l.jr            r9
+         l.ori          r11, r3, 0