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55 lines
1.5 KiB
55 lines
1.5 KiB
20 years ago
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/*
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* arch/alpha/lib/ev67-strcat.S
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* 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com>
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*
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* Append a null-terminated string from SRC to DST.
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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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* Commentary: It seems bogus to walk the input string twice - once
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* to determine the length, and then again while doing the copy.
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* A significant (future) enhancement would be to only read the input
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* string once.
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*/
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.text
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.align 4
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.globl strcat
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.ent strcat
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strcat:
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.frame $30, 0, $26
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.prologue 0
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mov $16, $0 # E : set up return value
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/* Find the end of the string. */
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ldq_u $1, 0($16) # L : load first quadword (a0 may be misaligned)
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lda $2, -1 # E :
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insqh $2, $16, $2 # U :
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andnot $16, 7, $16 # E :
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or $2, $1, $1 # 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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/* Now do the append. */
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mov $26, $23 # E :
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br __stxcpy # L0 :
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.end strcat
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