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OpcodeDispatcher: calculate PF with integer ops

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based on clang's __builtin_parity

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
This commit is contained in:
Alyssa Rosenzweig 2024-04-01 13:58:07 -04:00
parent 65ec191dc1
commit 3b052e826f
1 changed files with 5 additions and 6 deletions
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11
FEXCore/Source/Interface/Core/OpcodeDispatcher/Flags.cpp
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@ -242,13 +242,12 @@ OrderedNode *OpDispatchBuilder::LoadPFRaw() {
// parity calculated.
auto Result = GetRFLAG(FEXCore::X86State::RFLAG_PF_RAW_LOC);
// Cast the input to a 32-bit FPR. Logically we only need 8-bit, but that would
// generate unwanted an ubfx instruction. VPopcount will ignore the upper bits anyway.
auto InputFPR = _VCastFromGPR(4, 4, Result);
// Cascade to calculate parity of bottom 8-bits to bottom bit.
Result = _XorShift(OpSize::i32Bit, Result, Result, ShiftType::LSR, 4);
Result = _XorShift(OpSize::i32Bit, Result, Result, ShiftType::LSR, 2);
Result = _XorShift(OpSize::i32Bit, Result, Result, ShiftType::LSR, 1);
// Calculate the popcount.
auto Count = _VPopcount(1, 1, InputFPR);
return _VExtractToGPR(8, 1, Count, 0);
return Result;
}
OrderedNode *OpDispatchBuilder::LoadAF() {