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59 lines
1.8 KiB
ArmAsm
59 lines
1.8 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, memcpy_upwards
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.import memcpy_getparams, memcpy_downwards, 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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jcs memcpy_downwards ; Branch if dest < src (upwards copy)
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memcpy_upwards:
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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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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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; Done, return dest
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done: jmp popax ; Pop ptr and return as result
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