94 lines
2.3 KiB
ArmAsm
94 lines
2.3 KiB
ArmAsm
/* a-memcpy.s -- memcpy, optimised for m68k asm
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*
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* Copyright (c) 2007 mocom software GmbH & Co KG)
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*
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* The authors hereby grant permission to use, copy, modify, distribute,
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* and license this software and its documentation for any purpose, provided
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* that existing copyright notices are retained in all copies and that this
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* notice is included verbatim in any distributions. No written agreement,
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* license, or royalty fee is required for any of the authorized uses.
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* Modifications to this software may be copyrighted by their authors
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* and need not follow the licensing terms described here, provided that
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* the new terms are clearly indicated on the first page of each file where
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* they apply.
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*/
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.text
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.align 4
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.globl memcpy
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.type memcpy, @function
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/* memcpy, optimised
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*
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* strategy:
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* - no argument testing (the original memcpy from the GNU lib does
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* no checking either)
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* - make sure the destination pointer (the write pointer) is long word
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* aligned. This is the best you can do, because writing to unaligned
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* addresses can be the most costfull thing you could do.
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* - Once you have figured that out, we do a little loop unrolling
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* to further improve speed.
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*/
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memcpy:
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move.l 4(%sp),%a0 | dest ptr
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move.l 8(%sp),%a1 | src ptr
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move.l 12(%sp),%d1 | len
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cmp.l #8,%d1 | if fewer than 8 bytes to transfer,
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blo .Lresidue | do not optimise
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/* align dest */
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move.l %a0,%d0 | copy of dest
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neg.l %d0
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and.l #3,%d0 | look for the lower two only
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beq 2f | is aligned?
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sub.l %d0,%d1
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lsr.l #1,%d0 | word align needed?
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bcc 1f
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move.b (%a1)+,(%a0)+
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1:
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lsr.l #1,%d0 | long align needed?
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bcc 2f
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move.w (%a1)+,(%a0)+
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2:
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/* long word transfers */
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move.l %d1,%d0
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and.l #3,%d1 | byte residue
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lsr.l #3,%d0
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bcc 1f | carry set for 4-byte residue
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move.l (%a1)+,(%a0)+
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1:
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lsr.l #1,%d0 | number of 16-byte transfers
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bcc .Lcopy | carry set for 8-byte residue
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bra .Lcopy8
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1:
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move.l (%a1)+,(%a0)+
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move.l (%a1)+,(%a0)+
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.Lcopy8:
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move.l (%a1)+,(%a0)+
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move.l (%a1)+,(%a0)+
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.Lcopy:
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#if !defined (__mcoldfire__)
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dbra %d0,1b
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#else
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subq.l #1,%d0
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bpl 1b
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#endif
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bra .Lresidue
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1:
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move.b (%a1)+,(%a0)+ | move residue bytes
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.Lresidue:
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#if !defined (__mcoldfire__)
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dbra %d1,1b | loop until done
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#else
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subq.l #1,%d1
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bpl 1b
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#endif
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move.l 4(%sp),%d0 | return value
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rts
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