// For the parts of the code originating from LLVM-3.5:
//===-- ExternalFunctions.cpp - Implement External Functions --------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LLVMLICENSE for details.
//
//===----------------------------------------------------------------------===//
//
//  This file contains both code to deal with invoking "external" functions, but
//  also contains code that implements "exported" external functions.
//
//  There are currently two mechanisms for handling external functions in the
//  Interpreter.  The first is to implement lle_* wrapper functions that are
//  specific to well-known library functions which manually translate the
//  arguments from GenericValues and make the call.  If such a wrapper does
//  not exist, and libffi is available, then the Interpreter will attempt to
//  invoke the function using libffi, after finding its address.
//
//===----------------------------------------------------------------------===//

/*
 * (For the parts of the code modified from LLVM-3.5)
 *
 * GenMC -- Generic Model Checking.
 *
 * This program 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.
 *
 * This program 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 this program; if not, you can access it online at
 * http://www.gnu.org/licenses/gpl-3.0.html.
 *
 * Author: Michalis Kokologiannakis <michalis@mpi-sws.org>
 */

#include "config.h"

#include "Runtime/Interpreter.h"
#include "Support/Error.hpp"
#include <cmath>
#include <csignal>
#include <cstdio>
#include <cstring>
#include <llvm/IR/DataLayout.h>
#include <llvm/IR/DerivedTypes.h>
#include <llvm/IR/Module.h>
#include <llvm/Support/DynamicLibrary.h>
#include <llvm/Support/ErrorHandling.h>
#include <llvm/Support/ManagedStatic.h>
#include <llvm/Support/Mutex.h>
#include <map>

#ifdef HAVE_LIBFFI
#ifdef HAVE_FFI_H
#include <ffi.h>
#define USE_LIBFFI
#elif HAVE_FFI_FFI_H
#include <ffi/ffi.h>
#define USE_LIBFFI
#endif
#endif

#define LLVM_SYS_MUTEX_LOCK_FN lock
#define LLVM_SYS_MUTEX_UNLOCK_FN unlock

using namespace llvm;

static ManagedStatic<sys::Mutex> FunctionsLock;

typedef GenericValue (*ExFunc)(FunctionType *, const std::vector<GenericValue> &);
static ManagedStatic<std::map<const Function *, ExFunc>> ExportedFunctions;
static std::map<std::string, ExFunc> FuncNames;

#ifdef USE_LIBFFI
typedef void (*RawFunc)();
static ManagedStatic<std::map<const Function *, RawFunc>> RawFunctions;
#endif

static Interpreter *TheInterpreter;

static char getTypeID(Type *Ty)
{
	switch (Ty->getTypeID()) {
	case Type::VoidTyID:
		return 'V';
	case Type::IntegerTyID:
		switch (cast<IntegerType>(Ty)->getBitWidth()) {
		case 1:
			return 'o';
		case 8:
			return 'B';
		case 16:
			return 'S';
		case 32:
			return 'I';
		case 64:
			return 'L';
		default:
			return 'N';
		}
	case Type::FloatTyID:
		return 'F';
	case Type::DoubleTyID:
		return 'D';
	case Type::PointerTyID:
		return 'P';
	case Type::FunctionTyID:
		return 'M';
	case Type::StructTyID:
		return 'T';
	case Type::ArrayTyID:
		return 'A';
	default:
		return 'U';
	}
}

// Try to find address of external function given a Function object.
// Please note, that interpreter doesn't know how to assemble a
// real call in general case (this is JIT job), that's why it assumes,
// that all external functions has the same (and pretty "general") signature.
// The typical example of such functions are "lle_X_" ones.
static ExFunc lookupFunction(const Function *F)
{
	// Function not found, look it up... start by figuring out what the
	// composite function name should be.
	std::string ExtName = "lle_";
	FunctionType *FT = F->getFunctionType();
	for (unsigned i = 0, e = FT->getNumContainedTypes(); i != e; ++i)
		ExtName += getTypeID(FT->getContainedType(i));
	ExtName += "_" + F->getName().str();

	sys::ScopedLock Writer(*FunctionsLock);
	ExFunc FnPtr = FuncNames[ExtName];
	if (!FnPtr)
		FnPtr = FuncNames["lle_X_" + F->getName().str()];
	if (!FnPtr) // Try calling a generic function... if it exists...
		FnPtr = (ExFunc)(intptr_t)sys::DynamicLibrary::SearchForAddressOfSymbol(
			"lle_X_" + F->getName().str());
	if (FnPtr)
		ExportedFunctions->insert(std::make_pair(F, FnPtr)); // Cache for later
	return FnPtr;
}

#ifdef USE_LIBFFI
static ffi_type *ffiTypeFor(Type *Ty)
{
	switch (Ty->getTypeID()) {
	case Type::VoidTyID:
		return &ffi_type_void;
	case Type::IntegerTyID:
		switch (cast<IntegerType>(Ty)->getBitWidth()) {
		case 8:
			return &ffi_type_sint8;
		case 16:
			return &ffi_type_sint16;
		case 32:
			return &ffi_type_sint32;
		case 64:
			return &ffi_type_sint64;
		}
	case Type::FloatTyID:
		return &ffi_type_float;
	case Type::DoubleTyID:
		return &ffi_type_double;
	case Type::PointerTyID:
		return &ffi_type_pointer;
	default:
		break;
	}
	// TODO: Support other types such as StructTyID, ArrayTyID, OpaqueTyID, etc.
	report_fatal_error("Type could not be mapped for use with libffi.");
	return NULL;
}

static void *ffiValueFor(Type *Ty, const GenericValue &AV, void *ArgDataPtr)
{
	switch (Ty->getTypeID()) {
	case Type::IntegerTyID:
		switch (cast<IntegerType>(Ty)->getBitWidth()) {
		case 8: {
			int8_t *I8Ptr = (int8_t *)ArgDataPtr;
			*I8Ptr = (int8_t)AV.IntVal.getZExtValue();
			return ArgDataPtr;
		}
		case 16: {
			int16_t *I16Ptr = (int16_t *)ArgDataPtr;
			*I16Ptr = (int16_t)AV.IntVal.getZExtValue();
			return ArgDataPtr;
		}
		case 32: {
			int32_t *I32Ptr = (int32_t *)ArgDataPtr;
			*I32Ptr = (int32_t)AV.IntVal.getZExtValue();
			return ArgDataPtr;
		}
		case 64: {
			int64_t *I64Ptr = (int64_t *)ArgDataPtr;
			*I64Ptr = (int64_t)AV.IntVal.getZExtValue();
			return ArgDataPtr;
		}
		}
	case Type::FloatTyID: {
		float *FloatPtr = (float *)ArgDataPtr;
		*FloatPtr = AV.FloatVal;
		return ArgDataPtr;
	}
	case Type::DoubleTyID: {
		double *DoublePtr = (double *)ArgDataPtr;
		*DoublePtr = AV.DoubleVal;
		return ArgDataPtr;
	}
	case Type::PointerTyID: {
		void **PtrPtr = (void **)ArgDataPtr;
		*PtrPtr = GVTOP(AV);
		return ArgDataPtr;
	}
	default:
		break;
	}
	// TODO: Support other types such as StructTyID, ArrayTyID, OpaqueTyID, etc.
	report_fatal_error("Type value could not be mapped for use with libffi.");
	return NULL;
}

static bool ffiInvoke(RawFunc Fn, Function *F, const std::vector<GenericValue> &ArgVals,
		      const DataLayout *TD, GenericValue &Result)
{
	ffi_cif cif;
	FunctionType *FTy = F->getFunctionType();
	const unsigned NumArgs = F->arg_size();

	// TODO: We don't have type information about the remaining arguments, because
	// this information is never passed into ExecutionEngine::runFunction().
	if (ArgVals.size() > NumArgs && F->isVarArg()) {
		report_fatal_error("Calling external var arg function '" + F->getName() +
				   "' is not supported by the Interpreter.");
	}

	unsigned ArgBytes = 0;

	std::vector<ffi_type *> args(NumArgs);
	for (Function::const_arg_iterator A = F->arg_begin(), E = F->arg_end(); A != E; ++A) {
		const unsigned ArgNo = A->getArgNo();
		Type *ArgTy = FTy->getParamType(ArgNo);
		args[ArgNo] = ffiTypeFor(ArgTy);
		ArgBytes += TD->getTypeStoreSize(ArgTy);
	}

	SmallVector<uint8_t, 128> ArgData;
	ArgData.resize(ArgBytes);
	uint8_t *ArgDataPtr = ArgData.data();
	SmallVector<void *, 16> values(NumArgs);
	for (Function::const_arg_iterator A = F->arg_begin(), E = F->arg_end(); A != E; ++A) {
		const unsigned ArgNo = A->getArgNo();
		Type *ArgTy = FTy->getParamType(ArgNo);
		values[ArgNo] = ffiValueFor(ArgTy, ArgVals[ArgNo], ArgDataPtr);
		ArgDataPtr += TD->getTypeStoreSize(ArgTy);
	}

	Type *RetTy = FTy->getReturnType();
	ffi_type *rtype = ffiTypeFor(RetTy);

	if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, NumArgs, rtype, &args[0]) == FFI_OK) {
		SmallVector<uint8_t, 128> ret;
		if (RetTy->getTypeID() != Type::VoidTyID)
			ret.resize(TD->getTypeStoreSize(RetTy));
		ffi_call(&cif, Fn, ret.data(), values.data());
		switch (RetTy->getTypeID()) {
		case Type::IntegerTyID:
			switch (cast<IntegerType>(RetTy)->getBitWidth()) {
			case 8:
				Result.IntVal = APInt(8, *(int8_t *)ret.data());
				break;
			case 16:
				Result.IntVal = APInt(16, *(int16_t *)ret.data());
				break;
			case 32:
				Result.IntVal = APInt(32, *(int32_t *)ret.data());
				break;
			case 64:
				Result.IntVal = APInt(64, *(int64_t *)ret.data());
				break;
			}
			break;
		case Type::FloatTyID:
			Result.FloatVal = *(float *)ret.data();
			break;
		case Type::DoubleTyID:
			Result.DoubleVal = *(double *)ret.data();
			break;
		case Type::PointerTyID:
			Result.PointerVal = *(void **)ret.data();
			break;
		default:
			break;
		}
		return true;
	}

	return false;
}
#endif // USE_LIBFFI

GenericValue Interpreter::callExternalFunction(Function *F,
					       const std::vector<GenericValue> &ArgVals)
{
	TheInterpreter = this;

	FunctionsLock->LLVM_SYS_MUTEX_LOCK_FN();

	// Do a lookup to see if the function is in our cache... this should just be a
	// deferred annotation!
	std::map<const Function *, ExFunc>::iterator FI = ExportedFunctions->find(F);
	if (ExFunc Fn = (FI == ExportedFunctions->end()) ? lookupFunction(F) : FI->second) {
		FunctionsLock->LLVM_SYS_MUTEX_UNLOCK_FN();
		return Fn(F->getFunctionType(), ArgVals);
	}

#ifdef USE_LIBFFI
	std::map<const Function *, RawFunc>::iterator RF = RawFunctions->find(F);
	RawFunc RawFn;
	if (RF == RawFunctions->end()) {
		RawFn = (RawFunc)(intptr_t)sys::DynamicLibrary::SearchForAddressOfSymbol(
			F->getName().str());
		if (!RawFn)
			RawFn = (RawFunc)(intptr_t)getPointerToGlobalIfAvailable(F);
		if (RawFn != 0)
			RawFunctions->insert(std::make_pair(F, RawFn)); // Cache for later
	} else {
		RawFn = RF->second;
	}

	FunctionsLock->LLVM_SYS_MUTEX_UNLOCK_FN();

	GenericValue Result;
	const llvm::DataLayout *DL = &getDataLayout();
	if (RawFn != 0 && ffiInvoke(RawFn, F, ArgVals, DL, Result))
		return Result;
#endif // USE_LIBFFI

	if (F->getName() == "__main")
		errs() << "Tried to execute an unknown external function: " << *F->getType()
		       << " __main\n";
	else
		ERROR("Tried to execute an unknown external function: " + F->getName());
#ifndef USE_LIBFFI
	errs() << "Recompiling LLVM with --enable-libffi might help.\n";
#endif
	return GenericValue();
}

//===----------------------------------------------------------------------===//
//  Functions "exported" to the running application...
//

// void atexit(Function*)
static GenericValue lle_X_atexit(FunctionType *FT, const std::vector<GenericValue> &Args)
{
	assert(Args.size() == 1);
	TheInterpreter->addAtExitHandler((Function *)GVTOP(Args[0]));
	GenericValue GV;
	GV.IntVal = 0;
	return GV;
}

// void exit(int)
static GenericValue lle_X_exit(FunctionType *FT, const std::vector<GenericValue> &Args)
{
	TheInterpreter->exitCalled(Args[0]);
	return GenericValue();
}

// void abort(void)
static GenericValue lle_X_abort(FunctionType *FT, const std::vector<GenericValue> &Args)
{
	// FIXME: should we report or raise here?
	// report_fatal_error("Interpreted program raised SIGABRT");
	raise(SIGABRT);
	return GenericValue();
}

// int sprintf(char *, const char *, ...) - a very rough implementation to make
// output useful.
static GenericValue lle_X_sprintf(FunctionType *FT, const std::vector<GenericValue> &Args)
{
	char *OutputBuffer = (char *)GVTOP(Args[0]);
	const char *FmtStr = (const char *)GVTOP(Args[1]);
	unsigned ArgNo = 2;

	// printf should return # chars printed.  This is completely incorrect, but
	// close enough for now.
	GenericValue GV;
	GV.IntVal = APInt(32, strlen(FmtStr));
	while (1) {
		switch (*FmtStr) {
		case 0:
			return GV; // Null terminator...
		default:	   // Normal nonspecial character
			sprintf(OutputBuffer++, "%c", *FmtStr++);
			break;
		case '\\': { // Handle escape codes
			sprintf(OutputBuffer, "%c%c", *FmtStr, *(FmtStr + 1));
			FmtStr += 2;
			OutputBuffer += 2;
			break;
		}
		case '%': { // Handle format specifiers
			char FmtBuf[100] = "", Buffer[1000] = "";
			char *FB = FmtBuf;
			*FB++ = *FmtStr++;
			char Last = *FB++ = *FmtStr++;
			unsigned HowLong = 0;
			while (Last != 'c' && Last != 'd' && Last != 'i' && Last != 'u' &&
			       Last != 'o' && Last != 'x' && Last != 'X' && Last != 'e' &&
			       Last != 'E' && Last != 'g' && Last != 'G' && Last != 'f' &&
			       Last != 'p' && Last != 's' && Last != '%') {
				if (Last == 'l' || Last == 'L')
					HowLong++; // Keep track of l's
				Last = *FB++ = *FmtStr++;
			}
			*FB = 0;

			switch (Last) {
			case '%':
				memcpy(Buffer, "%", 2);
				break;
			case 'c':
				sprintf(Buffer, FmtBuf,
					uint32_t(Args[ArgNo++].IntVal.getZExtValue()));
				break;
			case 'd':
			case 'i':
			case 'u':
			case 'o':
			case 'x':
			case 'X':
				if (HowLong >= 1) {
#ifdef LLVM_EXECUTIONENGINE_DATALAYOUT_PTR
					const llvm::DataLayout *DL =
						TheInterpreter->getDataLayout();
#else
					const llvm::DataLayout *DL =
						&(TheInterpreter->getDataLayout());
#endif
					if (HowLong == 1 && DL->getPointerSizeInBits() == 64 &&
					    sizeof(long) < sizeof(int64_t)) {
						// Make sure we use %lld with a 64 bit argument
						// because we might be compiling LLI on a 32 bit
						// compiler.
						unsigned Size = strlen(FmtBuf);
						FmtBuf[Size] = FmtBuf[Size - 1];
						FmtBuf[Size + 1] = 0;
						FmtBuf[Size - 1] = 'l';
					}
					sprintf(Buffer, FmtBuf,
						Args[ArgNo++].IntVal.getZExtValue());
				} else
					sprintf(Buffer, FmtBuf,
						uint32_t(Args[ArgNo++].IntVal.getZExtValue()));
				break;
			case 'e':
			case 'E':
			case 'g':
			case 'G':
			case 'f':
				sprintf(Buffer, FmtBuf, Args[ArgNo++].DoubleVal);
				break;
			case 'p':
				sprintf(Buffer, FmtBuf, (void *)GVTOP(Args[ArgNo++]));
				break;
			case 's':
				sprintf(Buffer, FmtBuf, (char *)GVTOP(Args[ArgNo++]));
				break;
			default:
				errs() << "<unknown printf code '" << *FmtStr << "'!>";
				ArgNo++;
				break;
			}
			size_t Len = strlen(Buffer);
			memcpy(OutputBuffer, Buffer, Len + 1);
			OutputBuffer += Len;
		} break;
		}
	}
	return GV;
}

// int printf(const char *, ...) - a very rough implementation to make output
// useful.
static GenericValue lle_X_printf(FunctionType *FT, const std::vector<GenericValue> &Args)
{
	char Buffer[10000];
	std::vector<GenericValue> NewArgs;
	NewArgs.push_back(PTOGV((void *)&Buffer[0]));
	NewArgs.insert(NewArgs.end(), Args.begin(), Args.end());
	GenericValue GV = lle_X_sprintf(FT, NewArgs);
	outs() << Buffer;
	return GV;
}

// int sscanf(const char *format, ...);
static GenericValue lle_X_sscanf(FunctionType *FT, const std::vector<GenericValue> &args)
{
	assert(args.size() < 10 && "Only handle up to 10 args to sscanf right now!");

	char *Args[10];
	for (unsigned i = 0; i < args.size(); ++i)
		Args[i] = (char *)GVTOP(args[i]);

	GenericValue GV;
	GV.IntVal = APInt(32, sscanf(Args[0], Args[1], Args[2], Args[3], Args[4], Args[5], Args[6],
				     Args[7], Args[8], Args[9]));
	return GV;
}

// int scanf(const char *format, ...);
static GenericValue lle_X_scanf(FunctionType *FT, const std::vector<GenericValue> &args)
{
	assert(args.size() < 10 && "Only handle up to 10 args to scanf right now!");

	char *Args[10];
	for (unsigned i = 0; i < args.size(); ++i)
		Args[i] = (char *)GVTOP(args[i]);

	GenericValue GV;
	GV.IntVal = APInt(32, scanf(Args[0], Args[1], Args[2], Args[3], Args[4], Args[5], Args[6],
				    Args[7], Args[8], Args[9]));
	return GV;
}

// int fprintf(FILE *, const char *, ...) - a very rough implementation to make
// output useful.
static GenericValue lle_X_fprintf(FunctionType *FT, const std::vector<GenericValue> &Args)
{
	assert(Args.size() >= 2);
	char Buffer[10000];
	std::vector<GenericValue> NewArgs;
	NewArgs.push_back(PTOGV(Buffer));
	NewArgs.insert(NewArgs.end(), Args.begin() + 1, Args.end());
	GenericValue GV = lle_X_sprintf(FT, NewArgs);

	fputs(Buffer, (FILE *)GVTOP(Args[0]));
	return GV;
}

static GenericValue lle_X_memset(FunctionType *FT, const std::vector<GenericValue> &Args)
{
	/*
	 * Memory intrinsics should _not_ be executed here, as:
	 *   1) We do not know the size of subsequent loads in these addresses,
	 *      which will most likely lead to mixed-size memory accesses
	 *   2) They would need to be intercepted by the interpreter anyway
	 */
	ERROR("Invalid call to memset()!\n");

	// int val = (int)Args[1].IntVal.getSExtValue();
	// size_t len = (size_t)Args[2].IntVal.getZExtValue();
	// memset((void *)GVTOP(Args[0]), val, len);

	// llvm.memset.* returns void, lle_X_* returns GenericValue,
	// so here we return GenericValue with IntVal set to zero
	GenericValue GV;
	GV.IntVal = 0;
	return GV;
}

static GenericValue lle_X_memcpy(FunctionType *FT, const std::vector<GenericValue> &Args)
{
	ERROR("Invalid call to memcpy()!\n");

	// memcpy(GVTOP(Args[0]), GVTOP(Args[1]),
	//        (size_t)(Args[2].IntVal.getLimitedValue()));

	// llvm.memcpy* returns void, lle_X_* returns GenericValue,
	// so here we return GenericValue with IntVal set to zero
	GenericValue GV;
	GV.IntVal = 0;
	return GV;
}

void Interpreter::initializeExternalFunctions()
{
	sys::ScopedLock Writer(*FunctionsLock);
	FuncNames["lle_X_atexit"] = lle_X_atexit;
	FuncNames["lle_X_exit"] = lle_X_exit;
	FuncNames["lle_X_abort"] = lle_X_abort;

	FuncNames["lle_X_printf"] = lle_X_printf;
	FuncNames["lle_X_sprintf"] = lle_X_sprintf;
	FuncNames["lle_X_sscanf"] = lle_X_sscanf;
	FuncNames["lle_X_scanf"] = lle_X_scanf;
	FuncNames["lle_X_fprintf"] = lle_X_fprintf;
	FuncNames["lle_X_memset"] = lle_X_memset;
	FuncNames["lle_X_memcpy"] = lle_X_memcpy;
}
