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// license:BSD-3-Clause
// copyright-holders:Samuele Zannoli
#ifndef MAME_CPU_I386_CACHE_H
#define MAME_CPU_I386_CACHE_H
#pragma once
/* To test it outside of Mame
#include <cstdlib>
typedef unsigned char u8;
typedef unsigned int u32;
*/
enum {
CacheLineBytes16 = 4,
CacheLineBytes32 = 5,
CacheLineBytes64 = 6,
CacheLineBytes128 = 7,
CacheLineBytes256 = 8,
};
enum {
CacheDirectMapped = 0,
Cache2Way = 1,
Cache4Way = 2,
Cache8Way = 3,
Cache16Way = 4
};
enum {
CacheRead = 0,
CacheWrite = 1
};
template<int TagBits, int SetBits, int WayBits, int LineBits>
class cpucache {
public:
// Constructor
cpucache();
// Reset the cache
void reset();
// Find the cacheline containing data at address
template <int ReadWrite> u8* search(u32 address);
// Allocate a cacheline for data at address
template <int ReadWrite> bool allocate(u32 address, u8 **data);
// Get the address where the cacheline data should be written back to
u32 old();
// Get the address of the first byte of the cacheline that contains data at address
u32 base(u32 address);
// Compose the cacheline parameters into an address
u32 address(u32 tag, u32 set, u32 offset);
// Get the data of the first cacheline marked as dirty
u8* first_dirty(u32 &base, bool clean);
// Get the data of the next cacheline marked as dirty
u8* next_dirty(u32 &base, bool clean);
private:
static const int Ways = 1 << WayBits;
static const int LineBytes = 1 << LineBits;
static const int Sets = 1 << SetBits;
static const u32 LineMask = (1 << LineBits) - 1;
static const u32 SetMask = ((1 << SetBits) - 1) << LineBits;
static const u32 WayMask = (1 << WayBits) - 1;
static const int TagShift = LineBits + SetBits;
struct cacheline {
u8 data[LineBytes];
bool allocated;
bool dirty;
u32 tag;
u32 debug_address;
};
struct cacheset {
cacheline lines[Ways];
int nextway;
};
cacheset sets[Sets];
u32 writeback_base;
int last_set;
int last_way;
};
template<int TagBits, int SetBits, int WayBits, int LineBits>
cpucache<TagBits, SetBits, WayBits, LineBits>::cpucache()
{
reset();
}
template<int TagBits, int SetBits, int WayBits, int LineBits>
void cpucache<TagBits, SetBits, WayBits, LineBits>::reset()
{
for (int s = 0; s < Sets; s++)
for (int w = 0; w < Ways; w++)
{
sets[s].nextway = 0;
sets[s].lines[w].allocated = false;
sets[s].lines[w].dirty = false;
sets[s].lines[w].debug_address = 0;
}
last_set = -1;
last_way = -1;
}
template<int TagBits, int SetBits, int WayBits, int LineBits>
template<int ReadWrite>
u8* cpucache<TagBits, SetBits, WayBits, LineBits>::search(u32 address)
{
const int addresset = (address & SetMask) >> LineBits;
const int addrestag = address >> TagShift;
for (int w = 0; w < Ways; w++)
if ((sets[addresset].lines[w].allocated) && (sets[addresset].lines[w].tag == addrestag))
{
if (ReadWrite != 0)
sets[addresset].lines[w].dirty = true;
return sets[addresset].lines[w].data;
}
return nullptr;
}
template<int TagBits, int SetBits, int WayBits, int LineBits>
template<int ReadWrite>
bool cpucache<TagBits, SetBits, WayBits, LineBits>::allocate(u32 address, u8 **data)
{
const int addresset = (address & SetMask) >> LineBits;
const int addrestag = address >> TagShift;
const int victimway = sets[addresset].nextway;
bool old_allocated, old_dirty;
bool ret;
sets[addresset].nextway = (victimway + 1) & WayMask; // decide wich way will be allocated next
old_allocated = sets[addresset].lines[victimway].allocated;
old_dirty = sets[addresset].lines[victimway].dirty;
writeback_base = (sets[addresset].lines[victimway].tag << TagShift) | (address & SetMask);
sets[addresset].lines[victimway].tag = addrestag;
sets[addresset].lines[victimway].allocated = true;
if (ReadWrite == 0)
sets[addresset].lines[victimway].dirty = false; // caller must write back the cacheline if told so
else
sets[addresset].lines[victimway].dirty = true; // line is allocated to write into it
*data = sets[addresset].lines[victimway].data;
sets[addresset].lines[victimway].debug_address = address;
ret = old_allocated; // ret = old_allocated && old_dirty
if (!old_dirty)
ret = false;
return ret; // true if caller must write back the cacheline
}
template<int TagBits, int SetBits, int WayBits, int LineBits>
u32 cpucache<TagBits, SetBits, WayBits, LineBits>::old()
{
return writeback_base;
}
template<int TagBits, int SetBits, int WayBits, int LineBits>
u32 cpucache<TagBits, SetBits, WayBits, LineBits>::base(u32 address)
{
return address & ~LineMask;
}
template<int TagBits, int SetBits, int WayBits, int LineBits>
u32 cpucache<TagBits, SetBits, WayBits, LineBits>::address(u32 tag, u32 set, u32 offset)
{
return (tag << TagShift) | (set << LineBits) | offset;
}
template<int TagBits, int SetBits, int WayBits, int LineBits>
u8* cpucache<TagBits, SetBits, WayBits, LineBits>::first_dirty(u32 &base, bool clean)
{
for (int s = 0; s < Sets; s++)
for (int w = 0; w < Ways; w++)
if (sets[s].lines[w].dirty == true)
{
if (clean)
sets[s].lines[w].dirty = false;
last_set = s;
last_way = w;
base = address(sets[s].lines[w].tag, s, 0);
return sets[s].lines[w].data;
}
return nullptr;
}
template<int TagBits, int SetBits, int WayBits, int LineBits>
u8* cpucache<TagBits, SetBits, WayBits, LineBits>::next_dirty(u32 &base, bool clean)
{
if (last_set < 0)
return nullptr;
while (true)
{
last_way++;
if (last_way == Ways)
{
last_way = 0;
last_set++;
if (last_set == Sets)
{
last_set = -1;
last_way = -1;
return nullptr;
}
}
if (sets[last_set].lines[last_way].dirty == true)
{
if (clean)
sets[last_set].lines[last_way].dirty = false;
base = address(sets[last_set].lines[last_way].tag, last_set, 0);
return sets[last_set].lines[last_way].data;
}
}
}
#endif
/* To test it outside of Mame
const int memorysize = 256 * 1024;
u8 memory[memorysize];
void readline(u8 *data, u32 address)
{
for (int n = 0; n < 64; n++)
data[n] = memory[address + n];
}
void writeline(u8 *data, u32 address)
{
for (int n = 0; n < 64; n++)
memory[address + n] = data[n];
}
void cache_tester()
{
cpucache<18, 8, 6, 2> cache;
bool r;
u8 *data;
int address;
u8 value;
for (int n = 0; n < memorysize; n++)
memory[n] = 0xaa ^ n;
address = std::rand() & (memorysize - 1);
r = cache.search(address, &data);
if (r == false)
{
r = cache.allocate(address, &data);
if (r == true)
writeline(data, cache.base(address));
readline(data, cache.base(address));
}
value = data[address & 63];
if (value != memory[address])
printf("Error reading address %d\n\r", address);
}
*/
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