/* Copyright (C) 2009 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * CPU and memory detection.
 */

#ifndef INCLUDED_CPU
#define INCLUDED_CPU

#include "lib/sysdep/compiler.h"


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


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

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


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

/**
 * prevent the CPU from reordering previous loads or stores past the barrier,
 * thus ensuring they retire before any subsequent memory operations.
 * this also prevents compiler reordering.
 **/
#if MSC_VERSION
# include <intrin.h>
# pragma intrinsic(_ReadWriteBarrier)
# define cpu_MemoryBarrier() _ReadWriteBarrier()
#elif GCC_VERSION
# define cpu_MemoryBarrier() asm volatile("" : : : "memory")
#else
# define cpu_MemoryBarrier()
#endif

/**
 * 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)
 **/
LIB_API bool cpu_CAS(volatile uintptr_t* location, uintptr_t expected, uintptr_t newValue);

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

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

/**
 * enforce strict instruction ordering in the CPU pipeline.
 **/
LIB_API void cpu_Serialize();


//-----------------------------------------------------------------------------
// misc

/**
 * drop-in replacement for POSIX memcpy().
 **/
LIB_API void* cpu_memcpy(void* RESTRICT dst, const void* RESTRICT src, size_t size);


/**
 * set the FPU control word to "desirable" values (see implementation)
 **/
LIB_API void cpu_ConfigureFloatingPoint();

// convert float to int much faster than _ftol2, which would normally be
// used by (int) casts.
// VC8 and GCC with -ffast-math now manage to generate SSE instructions,
// so our implementation is no longer needed.
#define cpu_i32FromFloat(f)  ((i32)(f))
#define cpu_i32FromDouble(d) ((i32)(d))
#define cpu_i64FromDouble(d) ((i64)(d))

#endif	// #ifndef INCLUDED_CPU