VVMAtomics.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#if WITH_VERSE_VM || defined(__INTELLISENSE__)
 
#include "HAL/Platform.h"
#include <atomic>
 
namespace Verse
{
 
inline void CompilerFence()
{
#if PLATFORM_WINDOWS
    _ReadWriteBarrier();
#else
    asm volatile("" ::
                     : "memory");
#endif
}
 
#if PLATFORM_CPU_ARM_FAMILY
 
inline void ArmDmb()
{
    asm volatile("dmb ish" ::
                     : "memory");
}
 
// Like the above, but only affects stores.
inline void ArmDmbSt()
{
    asm volatile("dmb ishst" ::
                     : "memory");
}
 
inline void ArmIsb()
{
    asm volatile("isb" ::
                     : "memory");
}
 
inline void LoadLoadFence()
{
    ArmDmb();
}
inline void LoadStoreFence()
{
    ArmDmb();
}
inline void StoreLoadFence()
{
    ArmDmb();
}
inline void StoreStoreFence()
{
    ArmDmbSt();
}
inline void CrossModifyingCodeFence()
{
    ArmIsb();
}
 
#elif PLATFORM_CPU_X86_FAMILY
 
inline void X86Ortop()
{
#if PLATFORM_WINDOWS
    FGenericPlatformMisc::MemoryBarrier();
#elif PLATFORM_64BITS
    asm volatile("lock; orl $0, (%%rsp)" ::
                     : "memory");
#else
    asm volatile("lock; orl $0, (%%esp)" ::
                     : "memory");
#endif
}
 
inline void X86Cpuid()
{
#if PLATFORM_WINDOWS
    int info[4];
    __cpuid(info, 0);
#else
    intptr_t a = 0, b, c, d;
    asm volatile(
        "cpuid"
        : "+a"(a), "=b"(b), "=c"(c), "=d"(d)
        :
        : "memory");
#endif
}
 
inline void LoadLoadFence()
{
    CompilerFence();
}
inline void LoadStoreFence()
{
    CompilerFence();
}
inline void StoreLoadFence()
{
    X86Ortop();
}
inline void StoreStoreFence()
{
    CompilerFence();
}
inline void CrossModifyingCodeFence()
{
    X86Cpuid();
}
 
#else
 
inline void LoadLoadFence()
{
    std::atomic_thread_fence(std::memory_order_seq_cst);
}
inline void LoadStoreFence()
{
    std::atomic_thread_fence(std::memory_order_seq_cst);
}
inline void StoreLoadFence()
{
    std::atomic_thread_fence(std::memory_order_seq_cst);
}
inline void StoreStoreFence()
{
    std::atomic_thread_fence(std::memory_order_seq_cst);
}
inline void CrossModifyingCodeFence()
{
    std::atomic_thread_fence(std::memory_order_seq_cst);
} // Probably not strong enough.
 
#endif
 
} // namespace Verse
#endif // WITH_VERSE_VM