FPControlWord.h

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// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
// SPDX-FileCopyrightText: 2021 Jorrit Rouwe
// SPDX-License-Identifier: MIT
 
#pragma once
 
#include <Jolt/Core/NonCopyable.h>
 
JPH_NAMESPACE_BEGIN
 
#if defined(JPH_CPU_WASM)
 
// Not supported
 
#elif defined(JPH_USE_SSE)
 
template <uint Value, uint Mask>
class FPControlWord : public NonCopyable
{
public:
                FPControlWord()
    {
        mPrevState = _mm_getcsr();
        _mm_setcsr((mPrevState & ~Mask) | Value);
    }
 
                ~FPControlWord()
    {
        _mm_setcsr((_mm_getcsr() & ~Mask) | (mPrevState & Mask));
    }
 
private:
    uint        mPrevState;
};
 
#elif defined(JPH_CPU_ARM) && defined(JPH_COMPILER_MSVC)
 
template <unsigned int Value, unsigned int Mask>
class FPControlWord : public NonCopyable
{
public:
                FPControlWord()
    {
        // Read state before change
        _controlfp_s(&mPrevState, 0, 0);
 
        // Update the state
        unsigned int dummy;
        _controlfp_s(&dummy, Value, Mask);
    }
 
                ~FPControlWord()
    {
        // Restore state
        unsigned int dummy;
        _controlfp_s(&dummy, mPrevState, Mask);
    }
 
private:
    unsigned int mPrevState;
};
 
#elif defined(JPH_CPU_ARM) && defined(JPH_USE_NEON)
 
template <uint64 Value, uint64 Mask>
class FPControlWord : public NonCopyable
{
public:
                FPControlWord()
    {
        uint64 val;
        asm volatile("mrs %0, fpcr" : "=r" (val));
        mPrevState = val;
        val &= ~Mask;
        val |= Value;
        asm volatile("msr fpcr, %0" : /* no output */ : "r" (val));
    }
 
                ~FPControlWord()
    {
        uint64 val;
        asm volatile("mrs %0, fpcr" : "=r" (val));
        val &= ~Mask;
        val |= mPrevState & Mask;
        asm volatile("msr fpcr, %0" : /* no output */ : "r" (val));
    }
 
private:
    uint64      mPrevState;
};
 
#elif defined(JPH_CPU_ARM)
 
template <uint32 Value, uint32 Mask>
class FPControlWord : public NonCopyable
{
public:
    FPControlWord()
    {
        uint32 val;
        asm volatile("vmrs %0, fpscr" : "=r" (val));
        mPrevState = val;
        val &= ~Mask;
        val |= Value;
        asm volatile("vmsr fpscr, %0" : /* no output */ : "r" (val));
    }
 
    ~FPControlWord()
    {
        uint32 val;
        asm volatile("vmrs %0, fpscr" : "=r" (val));
        val &= ~Mask;
        val |= mPrevState & Mask;
        asm volatile("vmsr fpscr, %0" : /* no output */ : "r" (val));
    }
 
private:
    uint32      mPrevState;
};
 
#else
 
#error Unsupported CPU architecture
 
#endif
 
JPH_NAMESPACE_END