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51 lines
1.3 KiB
51 lines
1.3 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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/* |
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* arch/alpha/lib/ev67-strlen.S |
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* 21264 version by Rick Gorton <rick.gorton@alpha-processor.com> |
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* |
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* Finds length of a 0-terminated string. Optimized for the |
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* Alpha architecture: |
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* |
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* - memory accessed as aligned quadwords only |
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* - uses bcmpge to compare 8 bytes in parallel |
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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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*/ |
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#include <asm/export.h> |
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.set noreorder |
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.set noat |
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.globl strlen |
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.ent strlen |
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.align 4 |
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strlen: |
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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, $16, $2 # U : |
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andnot $16, 7, $0 # E : |
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or $2, $1, $1 # E : |
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cmpbge $31, $1, $2 # E : $2 <- bitmask: bit i == 1 <==> i-th byte == 0 |
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nop # E : |
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bne $2, $found # U : |
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$loop: ldq $1, 8($0) # L : |
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addq $0, 8, $0 # E : addr += 8 |
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cmpbge $31, $1, $2 # E : |
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beq $2, $loop # U : |
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$found: |
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cttz $2, $3 # U0 : |
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addq $0, $3, $0 # E : |
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subq $0, $16, $0 # E : |
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ret $31, ($26) # L0 : |
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.end strlen |
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EXPORT_SYMBOL(strlen)
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