/*****************************************************************************
                    The Dark Mod GPL Source Code
 
 This file is part of the The Dark Mod Source Code, originally based 
 on the Doom 3 GPL Source Code as published in 2011.
 
 The Dark Mod Source Code is free software: you can redistribute it 
 and/or modify it under the terms of the GNU General Public License as 
 published by the Free Software Foundation, either version 3 of the License, 
 or (at your option) any later version. For details, see LICENSE.TXT.
 
 Project: The Dark Mod (http://www.thedarkmod.com/)
 
******************************************************************************/

#include "precompiled.h"
#pragma hdrstop

#include "Simd_Generic.h"
#include "Simd_MMX.h"
#include "Simd_3DNow.h"


//===============================================================
//
//	3DNow! implementation of idSIMDProcessor
//
//===============================================================

#if SIMD_USE_ASM

/*
============
idSIMD_3DNow::GetName
============
*/
const char * idSIMD_3DNow::GetName( void ) const {
	return "MMX & 3DNow!";
}

// Very optimized memcpy() routine for all 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 prefetchnta 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 64 * 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 197 * 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.

/*
================
idSIMD_3DNow::Memcpy

  optimized memory copy routine that handles all alignment cases and block sizes efficiently
================
*/
void VPCALL idSIMD_3DNow::Memcpy( void *dest, const void *src, const int n ) {
  __asm {

	mov		ecx, [n]					// number of bytes to copy
	mov		edi, [dest]					// destination
	mov		esi, [src]					// source
	mov		ebx, ecx					// keep a copy of count

	cld
	cmp		ecx, TINY_BLOCK_COPY
	jb		$memcpy_ic_3				// tiny? skip mmx copy

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

align 4
	movsb
	movsb
	movsb
	movsb
	movsb
	movsb
	movsb
	movsb

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

	cmp		ecx, IN_CACHE_COPY/64		// too big 4 cache? use uncached copy
	jae		$memcpy_uc_test

// 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		ecx							// count down
	jnz		$memcpy_ic_1				// last 64-byte block?

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

$memcpy_uc_test:
	cmp		ecx, UNCACHED_COPY/64		// big enough? use block prefetch copy
	jae		$memcpy_bp_1

$memcpy_64_test:
	or		ecx, ecx					// 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.
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		ecx
	movntq	[edi-8], mm1
	jnz		$memcpy_uc_1				// last 64-byte block?

	jmp		$memcpy_ic_2				// almost done

// 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, in this case.
// The technique is great for getting maximum read bandwidth,
// especially in DDR memory systems.
$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
	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 4
	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
	mov		ecx, ebx					// has valid low 2 bits of the byte count
	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

    }
}

#endif /* SIMD_USE_ASM */