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Latte: Use better hashing algorithm for cache invalidation

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Decreases chance of hash collisions while also being faster due to 4 channel vectorization
This commit is contained in:
Exzap 2023-04-15 10:02:56 +02:00
parent a640bd079c
commit ecb7b77326
1 changed files with 26 additions and 12 deletions
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38
src/Cafe/HW/Latte/Core/LatteBufferCache.cpp
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@ -734,20 +734,34 @@ private:
static uint64 hashPage(uint8* mem)
{
// note - this algorithm is/was also baked into pageWriteStreamoutSignatures()
uint64 h = 0;
uint64* memU64 = (uint64*)mem;
for (uint32 i = 0; i < CACHE_PAGE_SIZE / 8; i++)
{
//h = _rotr64(h, 7);
//h ^= *memU64;
//memU64++;
static const uint64 k0 = 0x55F23EAD;
static const uint64 k1 = 0x185FDC6D;
static const uint64 k2 = 0xF7431F49;
static const uint64 k3 = 0xA4C7AE9D;
h = std::rotr<uint64>(h, 7);
h += (*memU64 + (uint64)i);
memU64++;
cemu_assert_debug((CACHE_PAGE_SIZE % 32) == 0);
const uint64* ptr = (const uint64*)mem;
const uint64* end = ptr + (CACHE_PAGE_SIZE / sizeof(uint64));
uint64 h0 = 0;
uint64 h1 = 0;
uint64 h2 = 0;
uint64 h3 = 0;
while (ptr < end)
{
h0 = std::rotr(h0, 7);
h1 = std::rotr(h1, 7);
h2 = std::rotr(h2, 7);
h3 = std::rotr(h3, 7);
h0 += ptr[0] * k0;
h1 += ptr[1] * k1;
h2 += ptr[2] * k2;
h3 += ptr[3] * k3;
ptr += 4;
}
return h;
return h0 + h1 + h2 + h3;
}
// flag page as having streamout data, also write streamout signatures to page memory