85 строки
1.8 KiB
ArmAsm
85 строки
1.8 KiB
ArmAsm
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/*
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* arch/alpha/lib/strncat.S
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* Contributed by Richard Henderson (rth@tamu.edu)
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*
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* Append no more than COUNT characters from the null-terminated string SRC
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* to the null-terminated string DST. Always null-terminate the new DST.
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*
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* This differs slightly from the semantics in libc in that we never write
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* past count, whereas libc may write to count+1. This follows the generic
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* implementation in lib/string.c and is, IMHO, more sensible.
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*/
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.text
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.align 3
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.globl strncat
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.ent strncat
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strncat:
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.frame $30, 0, $26
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.prologue 0
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mov $16, $0 # set up return value
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beq $18, $zerocount
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/* Find the end of the string. */
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ldq_u $1, 0($16) # load first quadword ($16 may be misaligned)
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lda $2, -1($31)
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insqh $2, $16, $2
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andnot $16, 7, $16
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or $2, $1, $1
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cmpbge $31, $1, $2 # bits set iff byte == 0
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bne $2, $found
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$loop: ldq $1, 8($16)
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addq $16, 8, $16
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cmpbge $31, $1, $2
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beq $2, $loop
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$found: negq $2, $3 # clear all but least set bit
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and $2, $3, $2
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and $2, 0xf0, $3 # binary search for that set bit
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and $2, 0xcc, $4
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and $2, 0xaa, $5
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cmovne $3, 4, $3
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cmovne $4, 2, $4
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cmovne $5, 1, $5
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addq $3, $4, $3
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addq $16, $5, $16
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addq $16, $3, $16
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/* Now do the append. */
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bsr $23, __stxncpy
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/* Worry about the null termination. */
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zapnot $1, $27, $2 # was last byte a null?
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bne $2, 0f
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ret
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0: cmplt $27, $24, $2 # did we fill the buffer completely?
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or $2, $18, $2
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bne $2, 2f
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and $24, 0x80, $2 # no zero next byte
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bne $2, 1f
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/* Here there are bytes left in the current word. Clear one. */
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addq $24, $24, $24 # end-of-count bit <<= 1
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2: zap $1, $24, $1
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stq_u $1, 0($16)
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ret
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1: /* Here we must read the next DST word and clear the first byte. */
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ldq_u $1, 8($16)
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zap $1, 1, $1
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stq_u $1, 8($16)
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$zerocount:
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ret
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.end strncat
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