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96 lines
3.1 KiB
ArmAsm
96 lines
3.1 KiB
ArmAsm
;
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; Ullrich von Bassewitz, 2003-08-20
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; Performance increase (about 20%) by
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; Christian Krueger, 2009-09-13
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;
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; void* __fastcall__ memcpy (void* dest, const void* src, size_t n);
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;
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; NOTE: This function contains entry points for memmove, which will ressort
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; to memcpy for an upwards copy. Don't change this module without looking
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; at memmove!
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;
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.export _memcpy, memcpy_downwards, memcpy_getparams
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.import popax, popptr1
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.importzp sp, ptr1, ptr2, ptr3
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.macpack generic
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; ----------------------------------------------------------------------
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_memcpy:
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jsr memcpy_getparams
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memcpy_downwards:
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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: jmp popax ; Pop ptr and return as result
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; ----------------------------------------------------------------------
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; Get the parameters from stack as follows:
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;
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; size --> ptr3
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; src --> ptr1
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; dest --> ptr2
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; First argument (dest) will remain on stack and is returned in a/x!
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memcpy_getparams: ; IMPORTANT! Function has to leave with Y=0!
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sta ptr3
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stx ptr3+1 ; save n to ptr3
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jsr popptr1 ; save src to ptr1
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; save dest to ptr2
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iny ; Y=0 guaranteed by popptr1, we need '1' here...
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; (direct stack access is three cycles faster
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; (total cycle count with return))
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lda (sp),y
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tax
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stx ptr2+1 ; save high byte of ptr2
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dey ; Y = 0
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lda (sp),y ; Get ptr2 low
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sta ptr2
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rts
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