diff options
Diffstat (limited to 'libc/string/arm/strlen.S')
| -rw-r--r-- | libc/string/arm/strlen.S | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/libc/string/arm/strlen.S b/libc/string/arm/strlen.S index 5b4b02e17..949e918f4 100644 --- a/libc/string/arm/strlen.S +++ b/libc/string/arm/strlen.S @@ -20,6 +20,7 @@ #include <features.h> #include <endian.h> #include <sys/syscall.h> +#include <bits/arm_asm.h> /* size_t strlen(const char *S) * entry: r0 -> string @@ -31,6 +32,19 @@ .type strlen,%function .align 4 +#if defined(THUMB1_ONLY) +/* A simple implementation for when the ARM implementation can't be used. */ +.thumb_func +strlen: + mov r2, #0 +1: + ldrb r1, [r0, r2] + add r2, r2, #1 + cmp r1, #0 + bne 1b + sub r0, r2, #1 + bx lr +#else strlen: bic r1, r0, $3 @ addr of word containing first byte ldr r2, [r1], $4 @ get the first word @@ -41,38 +55,48 @@ strlen: #if __BYTE_ORDER == __BIG_ENDIAN orr r2, r2, $0xff000000 @ set this byte to non-zero subs r3, r3, $1 @ any more to do? + IT(t, gt) orrgt r2, r2, $0x00ff0000 @ if so, set this byte subs r3, r3, $1 @ more? + IT(t, gt) orrgt r2, r2, $0x0000ff00 @ then set. #else orr r2, r2, $0x000000ff @ set this byte to non-zero subs r3, r3, $1 @ any more to do? + IT(t, gt) orrgt r2, r2, $0x0000ff00 @ if so, set this byte subs r3, r3, $1 @ more? + IT(t, gt) orrgt r2, r2, $0x00ff0000 @ then set. #endif Laligned: @ here, we have a word in r2. Does it tst r2, $0x000000ff @ contain any zeroes? + IT(tttt, ne) tstne r2, $0x0000ff00 @ tstne r2, $0x00ff0000 @ tstne r2, $0xff000000 @ addne r0, r0, $4 @ if not, the string is 4 bytes longer + IT(t, ne) ldrne r2, [r1], $4 @ and we continue to the next word bne Laligned @ Llastword: @ drop through to here once we find a #if __BYTE_ORDER == __BIG_ENDIAN tst r2, $0xff000000 @ word that has a zero byte in it + IT(tttt, ne) addne r0, r0, $1 @ tstne r2, $0x00ff0000 @ and add up to 3 bytes on to it addne r0, r0, $1 @ tstne r2, $0x0000ff00 @ (if first three all non-zero, 4th + IT(t, ne) addne r0, r0, $1 @ must be zero) #else tst r2, $0x000000ff @ + IT(tttt, ne) addne r0, r0, $1 @ tstne r2, $0x0000ff00 @ and add up to 3 bytes on to it addne r0, r0, $1 @ tstne r2, $0x00ff0000 @ (if first three all non-zero, 4th + IT(t, ne) addne r0, r0, $1 @ must be zero) #endif #if defined(__USE_BX__) @@ -80,6 +104,7 @@ Llastword: @ drop through to here once we find a #else mov pc,lr #endif +#endif .size strlen,.-strlen |