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UserspaceEmulator: Improve FCOMI/FCOMIP/FUCOMI/FUCOMIP

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These instructions now operate on the specified FPU stack entry instead
of always using ST(0) and ST(1).

FUCOMI and FUCOMIP also handle NaN values slightly better.
This commit is contained in:
Andreas Kling 2020-11-14 15:15:41 +01:00
parent d4509647d8
commit 60ff27c633
Notes: sideshowbarker 2024-07-19 02:28:16 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/60ff27c6335
1 changed files with 16 additions and 8 deletions
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24
DevTools/UserspaceEmulator/SoftCPU.cpp
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@ -1709,24 +1709,32 @@ void SoftCPU::FNINIT(const X86::Instruction&) { TODO_INSN(); }
void SoftCPU::FNSETPM(const X86::Instruction&) { TODO_INSN(); }
void SoftCPU::FLD_RM80(const X86::Instruction&) { TODO_INSN(); }
void SoftCPU::FUCOMI(const X86::Instruction&)
void SoftCPU::FUCOMI(const X86::Instruction& insn)
{
auto i = insn.rm() & 7;
// FIXME: Unordered comparison checks.
// FIXME: QNaN / exception handling.
// FIXME: Set C0, C2, C3 in FPU status word.
set_zf(fpu_get(0) == fpu_get(1));
set_pf(false);
set_cf(fpu_get(0) < fpu_get(1));
set_of(false);
if (__builtin_isnan(fpu_get(0)) || __builtin_isnan(fpu_get(i))) {
set_zf(true);
set_pf(true);
set_cf(true);
} else {
set_zf(fpu_get(0) == fpu_get(i));
set_pf(false);
set_cf(fpu_get(0) < fpu_get(i));
set_of(false);
}
}
void SoftCPU::FCOMI(const X86::Instruction&)
void SoftCPU::FCOMI(const X86::Instruction& insn)
{
auto i = insn.rm() & 7;
// FIXME: QNaN / exception handling.
// FIXME: Set C0, C2, C3 in FPU status word.
set_zf(fpu_get(0) == fpu_get(1));
set_zf(fpu_get(0) == fpu_get(i));
set_pf(false);
set_cf(fpu_get(0) < fpu_get(1));
set_cf(fpu_get(0) < fpu_get(i));
set_of(false);
}