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80 lines
2.4 KiB
ArmAsm
80 lines
2.4 KiB
ArmAsm
;
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; 2003-08-20, Ullrich von Bassewitz
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; 2009-09-13, Christian Krueger -- performance increase (about 20%), 2013-07-25 improved unrolling
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; 2015-10-23, Greg King
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;
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; void* __fastcall__ memmove (void* dest, const void* src, size_t size);
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;
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; NOTE: This function uses entry points from memcpy!
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;
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.export _memmove
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.import memcpy_getparams, memcpy_upwards, popax
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.importzp ptr1, ptr2, ptr3, ptr4, tmp1
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.macpack generic
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.macpack longbranch
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; ----------------------------------------------------------------------
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_memmove:
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jsr memcpy_getparams
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; Check for the copy direction. If dest < src, we must copy upwards (start at
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; low addresses and increase pointers), otherwise we must copy downwards
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; (start at high addresses and decrease pointers).
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cmp ptr1
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txa
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sbc ptr1+1
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jcc memcpy_upwards ; Branch if dest < src (upwards copy)
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; Copy downwards. Adjust the pointers to the end of the memory regions.
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lda ptr1+1
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add ptr3+1
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sta ptr1+1
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lda ptr2+1
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add ptr3+1
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sta ptr2+1
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; handle fractions of a page size first
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ldy ptr3 ; count, low byte
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bne @entry ; something to copy?
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beq PageSizeCopy ; here like bra...
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@copyByte:
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lda (ptr1),y
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sta (ptr2),y
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@entry:
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dey
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bne @copyByte
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lda (ptr1),y ; copy remaining byte
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sta (ptr2),y
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PageSizeCopy: ; assert Y = 0
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ldx ptr3+1 ; number of pages
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beq done ; none? -> done
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@initBase:
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dec ptr1+1 ; adjust base...
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dec ptr2+1
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dey ; in entry case: 0 -> FF
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@copyBytes:
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.repeat 3 ; unroll this a bit to make it faster...
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lda (ptr1),y ; important: unrolling three times gives a nice
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sta (ptr2),y ; 255/3 = 85 loop which ends at 0
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dey
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.endrepeat
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@copyEntry: ; in entry case: 0 -> FF
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bne @copyBytes
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lda (ptr1),y ; Y = 0, copy last byte
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sta (ptr2),y
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dex ; one page to copy less
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bne @initBase ; still a page to copy?
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; Done, return dest
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done: jmp popax ; Pop ptr and return as result
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