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94 lines
2.4 KiB
ArmAsm
94 lines
2.4 KiB
ArmAsm
;
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; void* __fastcall__ memset (void* ptr, int c, size_t n);
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; void* __fastcall__ _bzero (void* ptr, size_t n);
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; void __fastcall__ bzero (void* ptr, size_t n);
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;
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; Ullrich von Bassewitz, 29.05.1998
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; Performance increase (about 20%) by
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; Christian Krueger, 12.09.2009, slightly improved 12.01.2011
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;
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; NOTE: bzero will return it's first argument as memset does. It is no problem
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; to declare the return value as void, since it may be ignored. _bzero
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; (note the leading underscore) is declared with the proper return type,
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; because the compiler will replace memset by _bzero if the fill value
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; is zero, and the optimizer looks at the return type to see if the value
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; in a/x is of any use.
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;
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.export _memset, _bzero, __bzero
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.import popax
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.importzp sp, ptr1, ptr2, ptr3
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_bzero:
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__bzero:
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sta ptr3
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stx ptr3+1 ; Save n
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ldx #0 ; Fill with zeros
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beq common
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_memset:
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sta ptr3 ; Save n
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stx ptr3+1
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jsr popax ; Get c
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tax
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; Common stuff for memset and bzero from here
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common: ; Fill value is in X!
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ldy #1
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lda (sp),y
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sta ptr1+1 ; save high byte of ptr
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dey ; Y = 0
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lda (sp),y ; Get ptr
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sta ptr1
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lsr ptr3+1 ; divide number of
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ror ptr3 ; bytes by two to increase
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bcc evenCount ; speed (ptr3 = ptr3/2)
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oddCount:
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; y is still 0 here
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txa ; restore fill value
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sta (ptr1),y ; save value and increase
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inc ptr1 ; dest. pointer
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bne evenCount
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inc ptr1+1
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evenCount:
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lda ptr1 ; build second pointer section
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clc
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adc ptr3 ; ptr2 = ptr1 + (length/2) <- ptr3
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sta ptr2
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lda ptr1+1
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adc ptr3+1
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sta ptr2+1
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txa ; restore fill value
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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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; Set 256/512 byte blocks
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; y is still 0 here
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L1: .repeat 2 ; Unroll this a bit to make it faster
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sta (ptr1),y ; Set byte in lower section
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sta (ptr2),y ; Set byte in upper section
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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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; Set the remaining bytes if any
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L2: ldy ptr3 ; Get the low byte of n
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beq leave ; something to set? No -> leave
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L3: dey
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sta (ptr1),y ; set bytes in low
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sta (ptr2),y ; and high section
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bne L3 ; flags still up to date from dey!
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leave:
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jmp popax ; Pop ptr and return as result
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