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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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46
Userland/DevTools/UserspaceEmulator/SoftVPU.h
View file

@ -6,12 +6,14 @@
#pragma once
#include <AK/FPControl.h>
#include <AK/SIMD.h>
#include <AK/Types.h>
#include <LibX86/Instruction.h>
#include <math.h>
namespace UserspaceEmulator {
using AK::RoundingMode;
using namespace AK::SIMD;
class Emulator;
class SoftCPU;
@ -57,51 +59,17 @@ public:
// FIXME: More with VEX prefix
};
i32 lround(float value) const
{
// FIXME: This is not yet 100% correct
using enum RoundingMode;
switch ((RoundingMode)rounding_control) {
case NEAREST:
return ::lroundf(value);
case DOWN:
return floorf(value);
case UP:
return ceilf(value);
case TRUNC:
return truncf(value);
default:
VERIFY_NOT_REACHED();
}
}
private:
friend SoftCPU;
Emulator& m_emulator;
SoftCPU& m_cpu;
XMM m_xmm[8];
union {
u32 m_mxcsr;
struct {
u32 invalid_operation_flag : 1; // IE
u32 denormal_operation_flag : 1; // DE
u32 divide_by_zero_flag : 1; // ZE
u32 overflow_flag : 1; // OE
u32 underflow_flag : 1; // UE
u32 precision_flag : 1; // PE
u32 denormals_are_zero : 1; // FIXME: DAZ
u32 invalid_operation_mask : 1; // IM
u32 denormal_operation_mask : 1; // DM
u32 devide_by_zero_mask : 1; // ZM
u32 overflow_mask : 1; // OM
u32 underflow_mask : 1; // UM
u32 precision_mask : 1; // PM
u32 rounding_control : 2; // FIXME: RC
u32 flush_to_zero : 1; // FIXME: FTZ
u32 __reserved : 16;
};
};
// FIXME: Maybe unimplemented features:
// * DAZ
// * FTZ
AK::MXCSR m_mxcsr;
void PREFETCHTNTA(X86::Instruction const&);
void PREFETCHT0(X86::Instruction const&);