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81 lines
2.6 KiB
ArmAsm
81 lines
2.6 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_upwards, memcpy_getparams
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.import popax
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.importzp sp, ptr1, ptr2, ptr3
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; ----------------------------------------------------------------------
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_memcpy:
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jsr memcpy_getparams
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memcpy_upwards: ; assert Y = 0
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ldx ptr3+1 ; Get high byte of n
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beq L2 ; Jump if zero
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L1: .repeat 2 ; Unroll this a bit to make it faster...
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lda (ptr1),Y ; copy a byte
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sta (ptr2),Y
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iny
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.endrepeat
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bne L1
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inc ptr1+1
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inc ptr2+1
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dex ; Next 256 byte block
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bne L1 ; Repeat if any
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; the following section could be 10% faster if we were able to copy
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; back to front - unfortunately we are forced to copy strict from
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; low to high since this function is also used for
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; memmove and blocks could be overlapping!
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; {
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L2: ; assert Y = 0
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ldx ptr3 ; Get the low byte of n
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beq done ; something to copy
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L3: lda (ptr1),Y ; copy a byte
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sta (ptr2),Y
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iny
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dex
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bne L3
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; }
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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 popax
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sta ptr1
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stx ptr1+1 ; save src to ptr1
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; save dest to ptr2
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ldy #1 ; (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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