cpu.h

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/* Copyright (C) 2022 Wildfire Games.
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
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 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * CPU and memory detection.
 */

#ifndef INCLUDED_CPU
#define INCLUDED_CPU

#include "lib/sysdep/compiler.h"


namespace ERR
{
    const Status CPU_FEATURE_MISSING     = -130000;
    const Status CPU_UNKNOWN_OPCODE      = -130001;
    const Status CPU_UNKNOWN_VENDOR      = -130002;

}


//-----------------------------------------------------------------------------
// CPU detection

/**
 * @return string identifying the CPU (usually a cleaned-up version of the
 * brand string)
 **/
const char* cpu_IdentifierString();


//-----------------------------------------------------------------------------
// lock-free support routines

/**
 * add a signed value to a variable without the possibility of interference
 * from other threads/CPUs.
 *
 * @return the previous value.
 **/
intptr_t cpu_AtomicAdd(volatile intptr_t* location, intptr_t increment);

/**
 * atomic "compare and swap".
 *
 * @param location address of the word to compare and possibly overwrite
 * @param expected its expected value
 * @param newValue the value with which to replace it
 * @return false if the target word doesn't match the expected value,
 * otherwise true (also overwriting the contents of location)
 **/
bool cpu_CAS(volatile intptr_t* location, intptr_t expected, intptr_t newValue);
bool cpu_CAS64(volatile i64* location, i64 expected, i64 newValue);

/**
 * specialization of cpu_CAS for pointer types. this avoids error-prone
 * casting in user code.
 **/
template<typename T>
inline bool cpu_CAS(volatile T* location, T expected, T new_value)
{
    return cpu_CAS((volatile intptr_t*)location, (intptr_t)expected, (intptr_t)new_value);
}


void cpu_Test();

/**
 * pause in spin-wait loops, as a performance optimisation.
 **/
inline void cpu_Pause()
{
#if MSC_VERSION && ARCH_X86_X64
    _mm_pause();
#elif GCC_VERSION && ARCH_X86_X64
    __asm__ __volatile__( "rep; nop" : : : "memory" );
#endif
}

#endif  // #ifndef INCLUDED_CPU