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96 lines
2.4 KiB
96 lines
2.4 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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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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#include <asm/export.h> |
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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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EXPORT_SYMBOL(strncat)
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