strncpy

strncpy

Posted Aug 21, 2003 20:09 UTC (Thu) by chad.netzer (subscriber, #4257)
In reply to: strncpy by paulsheer
Parent article: Kernel release status

I noticed the same thing as you, until a Google search led me to try it on PPC linux. And indeed, there, it does seem to save a branch. I'll post the code below. The first function, is Erik Andersen's code, which I called 'strncpy2'. The original (below it) is called 'strncpy'.

        .file   "strncpy.c"
        .section        ".text"
        .align 2
        .globl strncpy2
        .type   strncpy2, @function
strncpy2:
        mtctr 5
        mr 9,3
        cmpwi 0,5,0
        beqlr- 0
.L16:
        lbz 0,0(4)
        stb 0,0(9)
        neg 0,0
        srwi 0,0,31
        add 4,4,0
        addi 9,9,1
        bdnz .L16
        blr
        .size   strncpy2, .-strncpy2
        .align 2
        .globl strncpy
        .type   strncpy, @function
strncpy:
        mr 9,3
.L20:
        cmpwi 0,5,0
        addi 5,5,-1
        beq- 0,.L21
        lbz 0,0(4)
        stb 0,0(3)
        addi 4,4,1
        addi 3,3,1
        cmpwi 0,0,0
        bne+ 0,.L20
.L21:
        mr 3,9
        blr
        .size   strncpy, .-strncpy
        .ident  "GCC: (GNU) 3.3.2 20030812 (Debian prerelease)"

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