The generic implementation of strlen() reads strings byte per byte.
This patch implements strlen() in assembly for PPC32 based on
a read of entire words, in the same spirit as what some other
arches and glibc do.
For long strings, the time spent in strlen is reduced by 50-60%
Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
---
Applies on top of serie "[v5 0/3] powerpc/lib: Optimisation of memcmp() and
__clear_user() for PPC32"
Changes in v2:
- Moved handling of unaligned strings outside of the main path as it is very
unlikely.
- Removed the verification of the fourth byte in case none of the three first
ones are NUL.
arch/powerpc/include/asm/string.h | 3 +++
arch/powerpc/lib/string_32.S | 41 +++++++++++++++++++++++++++++++++++++++
2 files changed, 44 insertions(+)
diff --git a/arch/powerpc/include/asm/string.h
b/arch/powerpc/include/asm/string.h
index 9b8cedf618f4..5ecfdb776f87 100644
--- a/arch/powerpc/include/asm/string.h
+++ b/arch/powerpc/include/asm/string.h
@@ -13,6 +13,9 @@
#define __HAVE_ARCH_MEMCHR
#define __HAVE_ARCH_MEMSET16
#define __HAVE_ARCH_MEMCPY_FLUSHCACHE
+#ifdef CONFIG_PPC32
+#define __HAVE_ARCH_STRLEN
+#endif
extern char * strcpy(char *,const char *);
extern char * strncpy(char *,const char *, __kernel_size_t);
diff --git a/arch/powerpc/lib/string_32.S b/arch/powerpc/lib/string_32.S
index 4fbaa046aa84..69593c917b35 100644
--- a/arch/powerpc/lib/string_32.S
+++ b/arch/powerpc/lib/string_32.S
@@ -47,6 +47,47 @@ _GLOBAL(memcmp)
blr
EXPORT_SYMBOL(memcmp)
+_GLOBAL(strlen)
+ andi. r9, r3, 3
+ addi r10, r3, -4
+ bne- 1f
+2: lis r6, 0x8080
+ ori r6, r6, 0x8080 /* r6 = 0x80808080 (himagic) */
+ rlwinm r7, r6, 1, 0xffffffff /* r7 = 0x01010101 (lomagic) */
+3: lwzu r9, 4(r10)
+ /* ((x - lomagic) & ~x & himagic) == 0 means no byte in x is NUL */
+ subf r8, r7, r9
+ andc r11, r6, r9
+ and. r8, r8, r11
+ beq+ 3b
+ rlwinm. r8, r9, 0, 0xff000000
+ beq 20f
+ rlwinm. r8, r9, 0, 0x00ff0000
+ beq 21f
+ rlwinm. r8, r9, 0, 0x0000ff00
+ beq 22f
+ subf r3, r3, r10
+ addi r3, r3, 3
+ blr
+22: subf r3, r3, r10
+ addi r3, r3, 2
+ blr
+21: subf r3, r3, r10
+ addi r3, r3, 1
+ blr
+19: addi r10, r10, 3
+20: subf r3, r3, r10
+ blr
+
+1: lbz r9, 4(r10)
+ addi r10, r10, 1
+ cmpwi cr1, r9, 0
+ andi. r9, r10, 3
+ beq cr1, 19b
+ bne 1b
+ b 2b
+EXPORT_SYMBOL(strlen)
+
CACHELINE_BYTES = L1_CACHE_BYTES
LG_CACHELINE_BYTES = L1_CACHE_SHIFT
CACHELINE_MASK = (L1_CACHE_BYTES-1)
--
2.13.3
