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95 lines
2.4 KiB
ArmAsm
95 lines
2.4 KiB
ArmAsm
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/*
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* arch/alpha/lib/ev67-strncat.S
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* 21264 version contributed by Rick Gorton <rick.gorton@api-networks.com>
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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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* Much of the information about 21264 scheduling/coding comes from:
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* Compiler Writer's Guide for the Alpha 21264
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* abbreviated as 'CWG' in other comments here
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* ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
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* Scheduling notation:
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* E - either cluster
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* U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
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* L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
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* Try not to change the actual algorithm if possible for consistency.
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*/
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.text
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.align 4
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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 # U :
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/* Find the end of the string. */
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ldq_u $1, 0($16) # L : load first quadword ($16 may be misaligned)
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lda $2, -1($31) # E :
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insqh $2, $0, $2 # U :
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andnot $16, 7, $16 # E :
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nop # E :
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or $2, $1, $1 # E :
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nop # E :
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nop # E :
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cmpbge $31, $1, $2 # E : bits set iff byte == 0
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bne $2, $found # U :
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$loop: ldq $1, 8($16) # L :
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addq $16, 8, $16 # E :
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cmpbge $31, $1, $2 # E :
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beq $2, $loop # U :
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$found: cttz $2, $3 # U0 :
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addq $16, $3, $16 # E :
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nop # E :
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bsr $23, __stxncpy # L0 :/* Now do the append. */
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/* Worry about the null termination. */
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zapnot $1, $27, $2 # U : was last byte a null?
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cmplt $27, $24, $5 # E : did we fill the buffer completely?
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bne $2, 0f # U :
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ret # L0 :
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0: or $5, $18, $2 # E :
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nop
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bne $2, 2f # U :
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and $24, 0x80, $3 # E : no zero next byte
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nop # E :
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bne $3, 1f # U :
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/* Here there are bytes left in the current word. Clear one. */
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addq $24, $24, $24 # E : end-of-count bit <<= 1
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nop # E :
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2: zap $1, $24, $1 # U :
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nop # E :
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stq_u $1, 0($16) # L :
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ret # L0 :
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1: /* Here we must clear the first byte of the next DST word */
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stb $31, 8($16) # L :
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nop # E :
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nop # E :
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ret # L0 :
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$zerocount:
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nop # E :
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nop # E :
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nop # E :
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ret # L0 :
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.end strncat
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