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UserspaceEmulator: Delegate rounding to the actual hardware

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This also makes us a bit more accurate, due to better rounding of
intermediate results.

This also gives us the flush-to-zero and denormals-are-zero SSE settings
for free! (Assuming UE is build with SSE)
This commit is contained in:
Hendiadyoin1 2022-04-08 17:09:19 +02:00 • committed by Linus Groh
parent 56a31ab376
commit 6c41267dcf
5 changed files with 91 additions and 126 deletions
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29
Userland/DevTools/UserspaceEmulator/SoftVPU.cpp
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@ -18,14 +18,35 @@ void SoftVPU::PREFETCHT2(X86::Instruction const&) { TODO(); }
void SoftVPU::LDMXCSR(X86::Instruction const& insn)
{
// FIXME: Shadows
m_mxcsr = insn.modrm().read32(m_cpu, insn).value();
m_mxcsr.mxcsr = insn.modrm().read32(m_cpu, insn).value();
// #GP - General Protection Fault
VERIFY((m_mxcsr & 0xFFFF'0000) == 0);
VERIFY((m_mxcsr.mxcsr & 0xFFFF'0000) == 0);
// Just let the host's SSE (or if not available x87) handle the rounding for us
// We do not want to accedentally raise an FP-Exception on the host, so we
// mask all exceptions
#ifdef __SSE__
AK::MXCSR temp = m_mxcsr;
temp.invalid_operation_mask = 1;
temp.denormal_operation_mask = 1;
temp.divide_by_zero_mask = 1;
temp.overflow_mask = 1;
temp.underflow_mask = 1;
temp.precision_mask = 1;
AK::set_mxcsr(temp);
#else
// FIXME: This will mess with x87-land, because it uses the same trick, and
// Does not know of us doing this
AK::X87ControlWord cw { 0x037F };
cw.rounding_control = m_mxcsr.rounding_control;
AK::set_cw_x87(cw);
#endif
}
void SoftVPU::STMXCSR(X86::Instruction const& insn)
{
// FIXME: Shadows
insn.modrm().write32(m_cpu, insn, ValueWithShadow<u32>::create_initialized(m_mxcsr));
insn.modrm().write32(m_cpu, insn, ValueWithShadow<u32>::create_initialized(m_mxcsr.mxcsr));
}
void SoftVPU::MOVUPS_xmm1_xmm2m128(X86::Instruction const& insn)
@ -222,7 +243,7 @@ void SoftVPU::CVTSS2SI_r32_xmm2m32(X86::Instruction const& insn)
{
// FIXME: Raise Invalid, Precision
insn.modrm().write32(m_cpu, insn,
ValueWithShadow<u32>::create_initialized((u32)lround(m_xmm[insn.modrm().reg()].ps[0])));
ValueWithShadow<u32>::create_initialized(static_cast<i32>(m_xmm[insn.modrm().reg()].ps[0])));
}
void SoftVPU::UCOMISS_xmm1_xmm2m32(X86::Instruction const& insn)