pcsx2/common/src/Utilities/x86/MemcpyFast.cpp

/******************************************************************************

 Copyright (c) 2001 Advanced Micro Devices, Inc.

 LIMITATION OF LIABILITY:  THE MATERIALS ARE PROVIDED *AS IS* WITHOUT ANY
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******************************************************************************/

#include "..\PrecompiledHeader.h"

#ifdef _MSC_VER
#pragma warning(disable:4414)
#endif

/*****************************************************************************
MEMCPY_AMD.CPP
******************************************************************************/

// Very optimized memcpy() routine for AMD Athlon and Duron family.
// This code uses any of FOUR different basic copy methods, depending
// on the transfer size.
// NOTE:  Since this code uses MOVNTQ (also known as "Non-Temporal MOV" or
// "Streaming Store"), and also uses the software prefetch instructions,
// be sure you're running on Athlon/Duron or other recent CPU before calling!

#define TINY_BLOCK_COPY 64       // upper limit for movsd type copy
// The smallest copy uses the X86 "movsd" instruction, in an optimized
// form which is an "unrolled loop".

#define IN_CACHE_COPY 2 * 1024  // upper limit for movq/movq copy w/SW prefetch
// Next is a copy that uses the MMX registers to copy 8 bytes at a time,
// also using the "unrolled loop" optimization.   This code uses
// the software prefetch instruction to get the data into the cache.

#define UNCACHED_COPY 4 * 1024 // upper limit for movq/movntq w/SW prefetch
// For larger blocks, which will spill beyond the cache, it's faster to
// use the Streaming Store instruction MOVNTQ.   This write instruction
// bypasses the cache and writes straight to main memory.  This code also
// uses the software prefetch instruction to pre-read the data.
// USE 64 * 1024 FOR THIS VALUE IF YOU'RE ALWAYS FILLING A "CLEAN CACHE"

#define BLOCK_PREFETCH_COPY  infinity // no limit for movq/movntq w/block prefetch 
#define CACHEBLOCK 80h // number of 64-byte blocks (cache lines) for block prefetch
// For the largest size blocks, a special technique called Block Prefetch
// can be used to accelerate the read operations.   Block Prefetch reads
// one address per cache line, for a series of cache lines, in a short loop.
// This is faster than using software prefetch.  The technique is great for
// getting maximum read bandwidth, especially in DDR memory systems.

// Inline assembly syntax for use with Visual C++

#if defined(_MSC_VER)

#ifdef PCSX2_DEBUG
extern u8 g_globalMMXSaved;

#endif


PCSX2_ALIGNED16( static u8 _xmm_backup[16*2] );
PCSX2_ALIGNED16( static u8 _mmx_backup[8*4] );

static __declspec(naked) void __fastcall _memcpy_raz_usrc(void *dest, const void *src, size_t bytes)
{
	// MOVSRC = opcode used to read. I use the same code for the aligned version, with a different define :)
	#define MOVSRC movdqu
	#define MOVDST movdqa

	__asm
	{
		//Reads before reads, to avoid stalls
		mov eax,[esp+4];
		//Make sure to save xmm0, it must be preserved ...
		movaps [_xmm_backup],xmm0;

		//if >=128 bytes use 128 byte unrolled loop
		//i use cmp ..,127 + jna because 127 is encodable using the simm8 form
		cmp eax,127;
		jna _loop_1;

		//since this is a common branch target it could be good to align it -- no idea if it has any effect :p
		align 16

		//128 byte unrolled loop
_loop_8:

		MOVSRC xmm0,[edx+0x00];	//read first to avoid read-after-write stalls
		MOVDST [ecx+0x00],xmm0; //then write :p
		MOVSRC xmm0,[edx+0x10];
		MOVDST [ecx+0x10],xmm0;
		sub edx,-128;			//edx won't be used for a while, so update it here. sub/-128 for simm8 encoding
		sub ecx,-128;			//ecx won't be used for a while, so update it here. sub/-128 for simm8 encoding

		MOVSRC xmm0,[edx+0x20-128];
		MOVDST [ecx+0x20-128],xmm0;
		MOVSRC xmm0,[edx+0x30-128];
		MOVDST [ecx+0x30-128],xmm0;
		add eax,-128;			//eax won't be used for a while, so update it here. add/-128 for simm8 encoding

		MOVSRC xmm0,[edx+0x40-128];
		MOVDST [ecx+0x40-128],xmm0;
		MOVSRC xmm0,[edx+0x50-128];
		MOVDST [ecx+0x50-128],xmm0;

		MOVSRC xmm0,[edx+0x60-128];
		MOVDST [ecx+0x60-128],xmm0;
		MOVSRC xmm0,[edx+0x70-128];
		MOVDST [ecx+0x70-128],xmm0;

		//127~ja, 127 is encodable as simm8 :)
		cmp eax,127;
		ja _loop_8;
		
		//direct copy for 0~7 qwords
		//in order to avoid the inc/dec of all 3 registers
		//i use negative relative addressing from the top of the buffers
		//[top-current index]

_loop_1:
		//prepare the regs for 'negative relative addressing'
		add edx,eax;
		add ecx,eax;
		neg eax;
		jz cleanup;	//exit if nothing to do

_loop_1_inner:
		MOVSRC xmm0,[edx+eax];
		MOVDST [ecx+eax],xmm0;
		
		add eax,16;		//while the offset is still negative we have data to copy
		js _loop_1_inner;

		//done !
cleanup:
		//restore xmm and exit ~)
		movaps xmm0,[_xmm_backup];
		ret 4;
	}
	#undef MOVSRC
	#undef MOVDST
}


static __declspec(naked) void __fastcall _memcpy_raz_udst(void *dest, const void *src, size_t bytes)
{
	// MOVDST = opcode used to read. I use the same code for the aligned version, with a different define :)
	#define MOVSRC movaps
	#define MOVDST movups
	__asm
	{
		//Reads before reads, to avoid stalls
		mov eax,[esp+4];
		//Make sure to save xmm0, it must be preserved ...
		movaps [_xmm_backup],xmm0;

		//if >=128 bytes use 128 byte unrolled loop
		//i use cmp ..,127 + jna because 127 is encodable using the simm8 form
		cmp eax,127;
		jna _loop_1;

		//since this is a common branch target it could be good to align it -- no idea if it has any effect :p
		align 16

		//128 byte unrolled loop
_loop_8:

		MOVSRC xmm0,[edx+0x00];	//read first to avoid read-after-write stalls
		MOVDST [ecx+0x00],xmm0; //then write :p
		MOVSRC xmm0,[edx+0x10];
		MOVDST [ecx+0x10],xmm0;
		sub edx,-128;			//edx won't be used for a while, so update it here. sub/-128 for simm8 encoding
		sub ecx,-128;			//ecx won't be used for a while, so update it here. sub/-128 for simm8 encoding

		MOVSRC xmm0,[edx+0x20-128];
		MOVDST [ecx+0x20-128],xmm0;
		MOVSRC xmm0,[edx+0x30-128];
		MOVDST [ecx+0x30-128],xmm0;
		add eax,-128;			//eax won't be used for a while, so update it here. add/-128 for simm8 encoding

		MOVSRC xmm0,[edx+0x40-128];
		MOVDST [ecx+0x40-128],xmm0;
		MOVSRC xmm0,[edx+0x50-128];
		MOVDST [ecx+0x50-128],xmm0;

		MOVSRC xmm0,[edx+0x60-128];
		MOVDST [ecx+0x60-128],xmm0;
		MOVSRC xmm0,[edx+0x70-128];
		MOVDST [ecx+0x70-128],xmm0;

		//127~ja, 127 is encodable as simm8 :)
		cmp eax,127;
		ja _loop_8;

		//direct copy for 0~7 qwords
		//in order to avoid the inc/dec of all 3 registers
		//i use negative relative addressing from the top of the buffers
		//[top-current index]

_loop_1:
		//prepare the regs for 'negative relative addressing'
		add edx,eax;
		add ecx,eax;
		neg eax;
		jz cleanup;	//exit if nothing to do

_loop_1_inner:
		MOVSRC xmm0,[edx+eax];
		movaps [ecx+eax],xmm0;

		add eax,16;		//while the offset is still negative we have data to copy
		js _loop_1_inner;

		//done !
cleanup:
		//restore xmm and exit ~)
		movaps xmm0,[_xmm_backup];
		ret 4;
	}
	#undef MOVSRC
	#undef MOVDST
}

// Custom memcpy, only for 16 byte aligned stuff (used for mtgs)
// This function is optimized for medium-small transfer sizes (<2048, >=128). No prefetching is
// used since the reads are linear and the cache logic can predict em :)
// *OBSOLETE* -- memcpy_amd_ has been optimized and is now faster.
__declspec(naked) void __fastcall memcpy_raz_(void *dest, const void *src, size_t bytes)
{
	// Code Implementation Notes:
	// Uses a forward copy, in 128 byte blocks, and then does the remaining in 16 byte blocks :)

	// MOVSRC = opcode used to read. I use the same code for the unaligned version, with a different define :)
	#define MOVSRC movaps
	#define MOVDST movaps
	__asm
	{
		//Reads before reads, to avoid stalls
		mov eax,[esp+4];
		//Make sure to save xmm0, it must be preserved ...
		movaps [_xmm_backup],xmm0;

		//if >=128 bytes use 128 byte unrolled loop
		//i use cmp ..,127 + jna because 127 is encodable using the simm8 form
		cmp eax,127;
		jna _loop_1;

		//since this is a common branch target it could be good to align it -- no idea if it has any effect :p
		align 16

		//128 byte unrolled loop
_loop_8:

		MOVSRC xmm0,[edx+0x00];	//read first to avoid read-after-write stalls
		MOVDST [ecx+0x00],xmm0; //then write :p
		MOVSRC xmm0,[edx+0x10];
		MOVDST [ecx+0x10],xmm0;
		sub edx,-128;			//edx won't be used for a while, so update it here. sub/-128 for simm8 encoding
		sub ecx,-128;			//ecx won't be used for a while, so update it here. sub/-128 for simm8 encoding

		MOVSRC xmm0,[edx+0x20-128];
		MOVDST [ecx+0x20-128],xmm0;
		MOVSRC xmm0,[edx+0x30-128];
		MOVDST [ecx+0x30-128],xmm0;
		add eax,-128;			//eax won't be used for a while, so update it here. add/-128 for simm8 encoding

		MOVSRC xmm0,[edx+0x40-128];
		MOVDST [ecx+0x40-128],xmm0;
		MOVSRC xmm0,[edx+0x50-128];
		MOVDST [ecx+0x50-128],xmm0;

		MOVSRC xmm0,[edx+0x60-128];
		MOVDST [ecx+0x60-128],xmm0;
		MOVSRC xmm0,[edx+0x70-128];
		MOVDST [ecx+0x70-128],xmm0;

		//127~ja, 127 is encodable as simm8 :)
		cmp eax,127;
		ja _loop_8;
		
		//direct copy for 0~7 qwords
		//in order to avoid the inc/dec of all 3 registers
		//i use negative relative addressing from the top of the buffers
		//[top-current index]

_loop_1:
		//prepare the regs for 'negative relative addressing'
		add edx,eax;
		add ecx,eax;
		neg eax;
		jz cleanup;	//exit if nothing to do

_loop_1_inner:
		MOVSRC xmm0,[edx+eax];
		MOVDST [ecx+eax],xmm0;
		
		add eax,16;		//while the offset is still negative we have data to copy
		js _loop_1_inner;

		//done !
cleanup:
		//restore xmm and exit ~)
		movaps xmm0,[_xmm_backup];
		ret 4;
	}
	#undef MOVSRC
	#undef MOVDST
}

// This memcpy routine is for use in situations where the source buffer's alignment is indeterminate.
__forceinline void __fastcall memcpy_raz_usrc(void *dest, const void *src, size_t bytes)
{
	if( ((uptr)src & 0xf) == 0 )
		memcpy_raz_( dest, src, bytes );
	else
		_memcpy_raz_usrc( dest, src, bytes );
}

// This memcpy routine is for use in situations where the destination buffer's alignment is indeterminate.
__forceinline void __fastcall memcpy_raz_udst(void *dest, const void *src, size_t bytes)
{
	if( ((uptr)dest & 0xf) == 0 )
		memcpy_raz_( dest, src, bytes );
	else
		_memcpy_raz_udst( dest, src, bytes );
}


//////////////////////////////////////////////////////////////////////////
// Fast memcpy as coded by AMD, and thn improved by air.
//
// This routine preserves mmx registers!  It's the complete real deal!
__declspec(naked) void __fastcall memcpy_amd_(void *dest, const void *src, size_t n)
{
    __asm
	{
	push    edi  
	push    esi  

	mov		edi, ecx		; destination
	mov		esi, edx		; source
	mov		ecx, [esp+12]	; number of bytes to copy
	mov		eax, ecx		; keep a copy of count

	cld
	cmp		eax, TINY_BLOCK_COPY
	jb		$memcpy_ic_3	; tiny? skip mmx copy

	cmp		eax, 32*1024		; don't align between 32k-64k because
	jbe		$memcpy_do_align	;  it appears to be slower
	cmp		eax, 64*1024
	jbe		$memcpy_align_done
$memcpy_do_align:
	mov		eax, 8			; a trick that's faster than rep movsb...
	sub		eax, edi		; align destination to qword
	and		eax, 111b		; get the low bits
	sub		ecx, eax		; update copy count
	neg		eax				; set up to jump into the array
	add		eax, offset $memcpy_align_done
	jmp		eax				; jump to array of movsb's

align 4
	movsb
	movsb
	movsb
	movsb
	movsb
	movsb
	movsb
	movsb

$memcpy_align_done:			; destination is dword aligned
	mov		eax, ecx		; number of bytes left to copy
	shr		eax, 6			; get 64-byte block count
	jz		$memcpy_ic_2	; finish the last few bytes

	mov     edx, offset _mmx_backup ; will probably need this to save/restore mmx
	cmp		eax, IN_CACHE_COPY/64	; too big 4 cache? use uncached copy
	jae		$memcpy_uc_test

	movq	[edx+0x00],mm0
	movq	[edx+0x08],mm1
	movq	[edx+0x10],mm2
	movq	[edx+0x18],mm3

// This is small block copy that uses the MMX registers to copy 8 bytes
// at a time.  It uses the "unrolled loop" optimization, and also uses
// the software prefetch instruction to get the data into the cache.
align 16
$memcpy_ic_1:			; 64-byte block copies, in-cache copy

	prefetchnta [esi + (200*64/34+192)]		; start reading ahead

	movq	mm0, [esi+0]	; read 64 bits
	movq	mm1, [esi+8]
	movq	[edi+0], mm0	; write 64 bits
	movq	[edi+8], mm1	;    note:  the normal movq writes the
	movq	mm2, [esi+16]	;    data to cache; a cache line will be
	movq	mm3, [esi+24]	;    allocated as needed, to store the data
	movq	[edi+16], mm2
	movq	[edi+24], mm3
	movq	mm0, [esi+32]
	movq	mm1, [esi+40]
	movq	[edi+32], mm0
	movq	[edi+40], mm1
	movq	mm2, [esi+48]
	movq	mm3, [esi+56]
	movq	[edi+48], mm2
	movq	[edi+56], mm3

	add		esi, 64			; update source pointer
	add		edi, 64			; update destination pointer
	dec		eax				; count down
	jnz		$memcpy_ic_1	; last 64-byte block?

	movq	mm0,[edx+0x00]
	movq	mm1,[edx+0x08]
	movq	mm2,[edx+0x10]
	movq	mm3,[edx+0x18]

$memcpy_ic_2:
	mov		eax, ecx		; has valid low 6 bits of the byte count
$memcpy_ic_3:
	shr		eax, 2			; dword count
	and		eax, 1111b		; only look at the "remainder" bits
	neg		eax				; set up to jump into the array
	add		eax, offset $memcpy_last_few
	jmp		eax				; jump to array of movsd's

$memcpy_uc_test:
	or		eax, eax		; tail end of block prefetch will jump here
	jz		$memcpy_ic_2	; no more 64-byte blocks left

// For larger blocks, which will spill beyond the cache, it's faster to
// use the Streaming Store instruction MOVNTQ.   This write instruction
// bypasses the cache and writes straight to main memory.  This code also
// uses the software prefetch instruction to pre-read the data.

	movq	[edx+0x00],mm0
	movq	[edx+0x08],mm1
	movq	[edx+0x10],mm2

align 16
$memcpy_uc_1:				; 64-byte blocks, uncached copy

	prefetchnta [esi + (200*64/34+192)]		; start reading ahead

	movq	mm0,[esi+0]		; read 64 bits
	add		edi,64			; update destination pointer
	movq	mm1,[esi+8]
	add		esi,64			; update source pointer
	movq	mm2,[esi-48]
	movntq	[edi-64], mm0	; write 64 bits, bypassing the cache
	movq	mm0,[esi-40]	;    note: movntq also prevents the CPU
	movntq	[edi-56], mm1	;    from READING the destination address
	movq	mm1,[esi-32]	;    into the cache, only to be over-written
	movntq	[edi-48], mm2	;    so that also helps performance
	movq	mm2,[esi-24]
	movntq	[edi-40], mm0
	movq	mm0,[esi-16]
	movntq	[edi-32], mm1
	movq	mm1,[esi-8]
	movntq	[edi-24], mm2
	movntq	[edi-16], mm0
	dec		eax
	movntq	[edi-8], mm1
	jnz		$memcpy_uc_1	; last 64-byte block?

	movq	mm0,[edx+0x00]
	movq	mm1,[edx+0x08]
	movq	mm2,[edx+0x10]

	jmp		$memcpy_ic_2		; almost done  (not needed because large copy below was removed)

// For the largest size blocks, a special technique called Block Prefetch
// can be used to accelerate the read operations.   Block Prefetch reads
// one address per cache line, for a series of cache lines, in a short loop.
// This is faster than using software prefetch.  The technique is great for
// getting maximum read bandwidth, especially in DDR memory systems.

// Note: Pcsx2 rarely invokes large copies, so this mode has been disabled to
// help keep the code cache footprint of memcpy_fast to a minimum.
/*
$memcpy_bp_1:			; large blocks, block prefetch copy

	cmp		ecx, CACHEBLOCK			; big enough to run another prefetch loop?
	jl		$memcpy_64_test			; no, back to regular uncached copy

	mov		eax, CACHEBLOCK / 2		; block prefetch loop, unrolled 2X
	add		esi, CACHEBLOCK * 64	; move to the top of the block
align 16
$memcpy_bp_2:
	mov		edx, [esi-64]		; grab one address per cache line
	mov		edx, [esi-128]		; grab one address per cache line
	sub		esi, 128			; go reverse order to suppress HW prefetcher
	dec		eax					; count down the cache lines
	jnz		$memcpy_bp_2		; keep grabbing more lines into cache

	mov		eax, CACHEBLOCK		; now that it's in cache, do the copy
align 16
$memcpy_bp_3:
	movq	mm0, [esi   ]		; read 64 bits
	movq	mm1, [esi+ 8]
	movq	mm2, [esi+16]
	movq	mm3, [esi+24]
	movq	mm4, [esi+32]
	movq	mm5, [esi+40]
	movq	mm6, [esi+48]
	movq	mm7, [esi+56]
	add		esi, 64				; update source pointer
	movntq	[edi   ], mm0		; write 64 bits, bypassing cache
	movntq	[edi+ 8], mm1		;    note: movntq also prevents the CPU
	movntq	[edi+16], mm2		;    from READING the destination address 
	movntq	[edi+24], mm3		;    into the cache, only to be over-written,
	movntq	[edi+32], mm4		;    so that also helps performance
	movntq	[edi+40], mm5
	movntq	[edi+48], mm6
	movntq	[edi+56], mm7
	add		edi, 64				; update dest pointer

	dec		eax					; count down

	jnz		$memcpy_bp_3		; keep copying
	sub		ecx, CACHEBLOCK		; update the 64-byte block count
	jmp		$memcpy_bp_1		; keep processing chunks
*/

// The smallest copy uses the X86 "movsd" instruction, in an optimized
// form which is an "unrolled loop".   Then it handles the last few bytes.
align 16
	movsd
	movsd			; perform last 1-15 dword copies
	movsd
	movsd
	movsd
	movsd
	movsd
	movsd
	movsd
	movsd			; perform last 1-7 dword copies
	movsd
	movsd
	movsd
	movsd
	movsd
	movsd

$memcpy_last_few:		; dword aligned from before movsd's
	and		ecx, 11b	; the last few cows must come home
	jz		$memcpy_final	; no more, let's leave
	rep		movsb		; the last 1, 2, or 3 bytes

$memcpy_final: 
	emms				; clean up the MMX state
	sfence				; flush the write buffer
	//mov		eax, [dest]	; ret value = destination pointer

	pop    esi  
	pop    edi

	ret 4
    }
}

// mmx mem-compare implementation, size has to be a multiple of 8
// returns 0 is equal, nonzero value if not equal
// ~10 times faster than standard memcmp
// (zerofrog)
u8 memcmp_mmx(const void* src1, const void* src2, int cmpsize)
{
	assert( (cmpsize&7) == 0 );

	__asm {
		push esi
		mov ecx, cmpsize
		mov edx, src1
		mov esi, src2

		cmp ecx, 32
		jl Done4

		// custom test first 8 to make sure things are ok
		movq mm0, [esi]
		movq mm1, [esi+8]
		pcmpeqd mm0, [edx]
		pcmpeqd mm1, [edx+8]
		pand mm0, mm1
		movq mm2, [esi+16]
		pmovmskb eax, mm0
		movq mm3, [esi+24]

		// check if eq
		cmp eax, 0xff
		je NextComp
		mov eax, 1
		jmp End

NextComp:
		pcmpeqd mm2, [edx+16]
		pcmpeqd mm3, [edx+24]
		pand mm2, mm3
		pmovmskb eax, mm2

		sub ecx, 32
		add esi, 32
		add edx, 32

		// check if eq
		cmp eax, 0xff
		je ContinueTest
		mov eax, 1
		jmp End

		cmp ecx, 64
		jl Done8

Cmp8:
		movq mm0, [esi]
		movq mm1, [esi+8]
		movq mm2, [esi+16]
		movq mm3, [esi+24]
		movq mm4, [esi+32]
		movq mm5, [esi+40]
		movq mm6, [esi+48]
		movq mm7, [esi+56]
		pcmpeqd mm0, [edx]
		pcmpeqd mm1, [edx+8]
		pcmpeqd mm2, [edx+16]
		pcmpeqd mm3, [edx+24]
		pand mm0, mm1
		pcmpeqd mm4, [edx+32]
		pand mm0, mm2
		pcmpeqd mm5, [edx+40]
		pand mm0, mm3
		pcmpeqd mm6, [edx+48]
		pand mm0, mm4
		pcmpeqd mm7, [edx+56]
		pand mm0, mm5
		pand mm0, mm6
		pand mm0, mm7
		pmovmskb eax, mm0
		
		// check if eq
		cmp eax, 0xff
		je Continue
		mov eax, 1
		jmp End

Continue:
		sub ecx, 64
		add esi, 64
		add edx, 64
ContinueTest:
		cmp ecx, 64
		jge Cmp8

Done8:
		test ecx, 0x20
		jz Done4
		movq mm0, [esi]
		movq mm1, [esi+8]
		movq mm2, [esi+16]
		movq mm3, [esi+24]
		pcmpeqd mm0, [edx]
		pcmpeqd mm1, [edx+8]
		pcmpeqd mm2, [edx+16]
		pcmpeqd mm3, [edx+24]
		pand mm0, mm1
		pand mm0, mm2
		pand mm0, mm3
		pmovmskb eax, mm0
		sub ecx, 32
		add esi, 32
		add edx, 32

		// check if eq
		cmp eax, 0xff
		je Done4
		mov eax, 1
		jmp End

Done4:
		cmp ecx, 24
		jne Done2
		movq mm0, [esi]
		movq mm1, [esi+8]
		movq mm2, [esi+16]
		pcmpeqd mm0, [edx]
		pcmpeqd mm1, [edx+8]
		pcmpeqd mm2, [edx+16]
		pand mm0, mm1
		pand mm0, mm2
		pmovmskb eax, mm0

		// check if eq
		cmp eax, 0xff
		setne al
		jmp End

Done2:
		cmp ecx, 16
		jne Done1

		movq mm0, [esi]
		movq mm1, [esi+8]
		pcmpeqd mm0, [edx]
		pcmpeqd mm1, [edx+8]
		pand mm0, mm1
		pmovmskb eax, mm0

		// check if eq
		cmp eax, 0xff
		setne al
		jmp End

Done1:
		cmp ecx, 8
		jne Done

		mov eax, [esi]
		mov esi, [esi+4]
		cmp eax, [edx]
		je Next
		mov eax, 1
		jmp End

Next:
		cmp esi, [edx+4]
		setne al
		jmp End

Done:
		xor eax, eax

End:
		pop esi
		emms
	}
}


// returns the xor of all elements, cmpsize has to be mult of 8
void memxor_mmx(void* dst, const void* src1, int cmpsize)
{
	assert( (cmpsize&7) == 0 );

	__asm {
		mov ecx, cmpsize
		mov eax, src1
		mov edx, dst

		cmp ecx, 64
		jl Setup4

		movq mm0, [eax]
		movq mm1, [eax+8]
		movq mm2, [eax+16]
		movq mm3, [eax+24]
		movq mm4, [eax+32]
		movq mm5, [eax+40]
		movq mm6, [eax+48]
		movq mm7, [eax+56]
		sub ecx, 64
		add eax, 64
		cmp ecx, 64
		jl End8

Cmp8:
		pxor mm0, [eax]
		pxor mm1, [eax+8]
		pxor mm2, [eax+16]
		pxor mm3, [eax+24]
		pxor mm4, [eax+32]
		pxor mm5, [eax+40]
		pxor mm6, [eax+48]
		pxor mm7, [eax+56]

		sub ecx, 64
		add eax, 64
		cmp ecx, 64
		jge Cmp8

End8:
		pxor mm0, mm4
		pxor mm1, mm5
		pxor mm2, mm6
		pxor mm3, mm7

		cmp ecx, 32
		jl End4
		pxor mm0, [eax]
		pxor mm1, [eax+8]
		pxor mm2, [eax+16]
		pxor mm3, [eax+24]
		sub ecx, 32
		add eax, 32
		jmp End4

Setup4:
		cmp ecx, 32
		jl Setup2

		movq mm0, [eax]
		movq mm1, [eax+8]
		movq mm2, [eax+16]
		movq mm3, [eax+24]
		sub ecx, 32
		add eax, 32

End4:
		pxor mm0, mm2
		pxor mm1, mm3

		cmp ecx, 16
		jl End2
		pxor mm0, [eax]
		pxor mm1, [eax+8]
		sub ecx, 16
		add eax, 16
		jmp End2

Setup2:
		cmp ecx, 16
		jl Setup1

		movq mm0, [eax]
		movq mm1, [eax+8]
		sub ecx, 16
		add eax, 16

End2:
		pxor mm0, mm1

		cmp ecx, 8
		jl End1
		pxor mm0, [eax]
End1:
		movq [edx], mm0
		jmp End

Setup1:
		movq mm0, [eax]
		movq [edx], mm0
End:
		emms
	}
}

#endif