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gsdx sw: add a code example for gather instruction 

It will requires a generic (register naming) linear interpolation to use it properly
Gather instruction requires an extra mask register therefore all registers name will be shuffled

Perf wise, initial haswell implementation seems to be microcode emulated.
This commit is contained in:
Gregory Hainaut 2016-11-19 10:40:39 +01:00
parent 2e20693583
commit 322473c295
1 changed files with 38 additions and 0 deletions
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38
plugins/GSdx/GSDrawScanlineCodeGenerator.x64.avx.cpp
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@ -2019,4 +2019,42 @@ void GSDrawScanlineCodeGenerator::ReadTexel(const Xmm& dst, const Xmm& addr, uin
else vpinsrd(dst, src, i);
}
// Gather example (AVX2). Not faster on Haswell but potentially better on recent CPU
// Worst case reduce Icache.
//
// Current limitation requires 1 extra free register for the mask.
// And palette need zero masking.
// It is not possible to use same source/destination so linear interpolation must be updated
#if 0
void GSDrawScanlineCodeGenerator::ReadTexel(int pixels, int mip_offset)
{
const int in[] = {0, 1, 2, 3};
const int out[] = {4, 5, 0, 1};
const int mask[] = {5, 0, 1, 2};
if (m_sel.tlu) {
for(int i = 0; i < pixels; i++) {
// FIXME can't use same dst and add register
Gather4Texel(Xmm(in[i]), _m_local__gd__tex, Xmm(in[i]), Xmm(mask[i]));
// FIXME need a memory and could be faster
vpslld(Xmm(in[i]), 24);
vpsrld(Xmm(in[i]), 24);
Gather4Texel(Xmm(out[i]), _m_local__gd__clut, Xmm(in[i]), Xmm(mask[i]));
}
} else {
for(int i = 0; i < pixels; i++) {
Gather4Texel(Xmm(out[i]), _m_local__gd__tex, Xmm(in[i]), Xmm(mask[i]));
}
}
}
static void Gather4Texel(const Xmm& dst, const Reg64& base, const Xmm& addr, const Xmm& Mask)
{
//void vpgatherdd(const Xmm& x1, const Address& addr, const Xmm& x2)
vpcmpeqd(Mask, Mask);
vpgatherdd(dst, ptr[base + addr * 4], Mask);
}
#endif
#endif