diff options
| author | Ralf Baechle <ralf@linux-mips.org> | 1997-01-07 02:33:00 +0000 |
|---|---|---|
| committer | <ralf@linux-mips.org> | 1997-01-07 02:33:00 +0000 |
| commit | beb116954b9b7f3bb56412b2494b562f02b864b1 (patch) | |
| tree | 120e997879884e1b9d93b265221b939d2ef1ade1 /arch/alpha/lib/strlen.S | |
| parent | 908d4681a1dc3792ecafbe64265783a86c4cccb6 (diff) | |
Import of Linux/MIPS 2.1.14
Diffstat (limited to 'arch/alpha/lib/strlen.S')
| -rw-r--r-- | arch/alpha/lib/strlen.S | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/arch/alpha/lib/strlen.S b/arch/alpha/lib/strlen.S new file mode 100644 index 000000000..fe63353de --- /dev/null +++ b/arch/alpha/lib/strlen.S @@ -0,0 +1,57 @@ +/* + * strlen.S (c) 1995 David Mosberger (davidm@cs.arizona.edu) + * + * Finds length of a 0-terminated string. Optimized for the + * Alpha architecture: + * + * - memory accessed as aligned quadwords only + * - uses bcmpge to compare 8 bytes in parallel + * - does binary search to find 0 byte in last + * quadword (HAKMEM needed 12 instructions to + * do this instead of the 9 instructions that + * binary search needs). + */ + + .set noreorder + .set noat + + .align 3 + + .globl strlen + .ent strlen + +strlen: + ldq_u $1, 0($16) # load first quadword ($16 may be misaligned) + lda $2, -1($31) + insqh $2, $16, $2 + andnot $16, 7, $0 + or $2, $1, $1 + cmpbge $31, $1, $2 # $2 <- bitmask: bit i == 1 <==> i-th byte == 0 + bne $2, found + +loop: ldq $1, 8($0) + addq $0, 8, $0 # addr += 8 + nop # helps dual issue last two insns + cmpbge $31, $1, $2 + beq $2, loop + +found: blbs $2, done # make aligned case fast + negq $2, $3 + and $2, $3, $2 + + and $2, 0x0f, $1 + addq $0, 4, $3 + cmoveq $1, $3, $0 + + and $2, 0x33, $1 + addq $0, 2, $3 + cmoveq $1, $3, $0 + + and $2, 0x55, $1 + addq $0, 1, $3 + cmoveq $1, $3, $0 + +done: subq $0, $16, $0 + ret $31, ($26) + + .end strlen |