48 lines
817 B
ArmAsm
48 lines
817 B
ArmAsm
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/*
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* Written by J.T. Conklin <jtc@NetBSD.org>.
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* Public domain.
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*/
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#include <machine/asm.h>
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#if defined(LIBC_SCCS)
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RCSID("$NetBSD: swab.S,v 1.4 2014/05/22 15:01:57 uebayasi Exp $")
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#endif
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#define LOAD_SWAP_STORE_WORD \
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lodsw ; \
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xchgb %al,%ah ; \
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stosw
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ENTRY3(swab)
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xchgq %rdi,%rsi
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cld # set direction forward
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shrq $1,%rdx
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testq $7,%rdx # copy first group of 1 to 7 words
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jz L2 # while swapping alternate bytes.
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L1: lodsw
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rorw $8,%ax
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stosw
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decq %rdx
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testq $7,%rdx
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jnz L1
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L2: shrq $3,%rdx # copy remainder 8 words at a time
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jz L4 # while swapping alternate bytes.
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L3:
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LOAD_SWAP_STORE_WORD
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LOAD_SWAP_STORE_WORD
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LOAD_SWAP_STORE_WORD
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LOAD_SWAP_STORE_WORD
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LOAD_SWAP_STORE_WORD
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LOAD_SWAP_STORE_WORD
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LOAD_SWAP_STORE_WORD
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LOAD_SWAP_STORE_WORD
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decq %rdx
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jnz L3
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L4:
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ret
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END(swab)
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