llvm-6502/lib/ExecutionEngine/JIT/JITEmitter.cpp

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//===-- Emitter.cpp - Write machine code to executable memory -------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines a MachineCodeEmitter object that is used by Jello to write
// machine code to memory and remember where relocatable values lie.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "jit"
#include "JIT.h"
#include "llvm/Constant.h"
#include "llvm/Module.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/Target/TargetData.h"
#include "Support/Debug.h"
#include "Support/Statistic.h"
#include "Support/SystemUtils.h"
using namespace llvm;
namespace {
Statistic<> NumBytes("jit", "Number of bytes of machine code compiled");
JIT *TheJIT = 0;
/// JITMemoryManager - Manage memory for the JIT code generation in a logical,
/// sane way. This splits a large block of MAP_NORESERVE'd memory into two
/// sections, one for function stubs, one for the functions themselves. We
/// have to do this because we may need to emit a function stub while in the
/// middle of emitting a function, and we don't know how large the function we
/// are emitting is. This never bothers to release the memory, because when
/// we are ready to destroy the JIT, the program exits.
class JITMemoryManager {
unsigned char *MemBase; // Base of block of memory, start of stub mem
unsigned char *FunctionBase; // Start of the function body area
unsigned char *CurStubPtr, *CurFunctionPtr;
public:
JITMemoryManager();
inline unsigned char *allocateStub(unsigned StubSize);
inline unsigned char *startFunctionBody();
inline void endFunctionBody(unsigned char *FunctionEnd);
};
}
JITMemoryManager::JITMemoryManager() {
// Allocate a 16M block of memory...
MemBase = (unsigned char*)AllocateRWXMemory(16 << 20);
FunctionBase = MemBase + 512*1024; // Use 512k for stubs
// Allocate stubs backwards from the function base, allocate functions forward
// from the function base.
CurStubPtr = CurFunctionPtr = FunctionBase;
}
unsigned char *JITMemoryManager::allocateStub(unsigned StubSize) {
CurStubPtr -= StubSize;
if (CurStubPtr < MemBase) {
std::cerr << "JIT ran out of memory for function stubs!\n";
abort();
}
return CurStubPtr;
}
unsigned char *JITMemoryManager::startFunctionBody() {
// Round up to an even multiple of 4 bytes, this should eventually be target
// specific.
return (unsigned char*)(((intptr_t)CurFunctionPtr + 3) & ~3);
}
void JITMemoryManager::endFunctionBody(unsigned char *FunctionEnd) {
assert(FunctionEnd > CurFunctionPtr);
CurFunctionPtr = FunctionEnd;
}
namespace {
/// Emitter - The JIT implementation of the MachineCodeEmitter, which is used
/// to output functions to memory for execution.
class Emitter : public MachineCodeEmitter {
JITMemoryManager MemMgr;
// CurBlock - The start of the current block of memory. CurByte - The
// current byte being emitted to.
unsigned char *CurBlock, *CurByte;
// When outputting a function stub in the context of some other function, we
// save CurBlock and CurByte here.
unsigned char *SavedCurBlock, *SavedCurByte;
// ConstantPoolAddresses - Contains the location for each entry in the
// constant pool.
std::vector<void*> ConstantPoolAddresses;
public:
Emitter(JIT &jit) { TheJIT = &jit; }
virtual void startFunction(MachineFunction &F);
virtual void finishFunction(MachineFunction &F);
virtual void emitConstantPool(MachineConstantPool *MCP);
virtual void startFunctionStub(const Function &F, unsigned StubSize);
virtual void* finishFunctionStub(const Function &F);
virtual void emitByte(unsigned char B);
virtual void emitWord(unsigned W);
virtual void emitWordAt(unsigned W, unsigned *Ptr);
virtual uint64_t getGlobalValueAddress(GlobalValue *V);
virtual uint64_t getGlobalValueAddress(const std::string &Name);
virtual uint64_t getConstantPoolEntryAddress(unsigned Entry);
virtual uint64_t getCurrentPCValue();
// forceCompilationOf - Force the compilation of the specified function, and
// return its address, because we REALLY need the address now.
//
// FIXME: This is JIT specific!
//
virtual uint64_t forceCompilationOf(Function *F);
};
}
MachineCodeEmitter *JIT::createEmitter(JIT &jit) {
return new Emitter(jit);
}
void Emitter::startFunction(MachineFunction &F) {
CurByte = CurBlock = MemMgr.startFunctionBody();
TheJIT->addGlobalMapping(F.getFunction(), CurBlock);
}
void Emitter::finishFunction(MachineFunction &F) {
MemMgr.endFunctionBody(CurByte);
ConstantPoolAddresses.clear();
NumBytes += CurByte-CurBlock;
DEBUG(std::cerr << "Finished CodeGen of [" << (void*)CurBlock
<< "] Function: " << F.getFunction()->getName()
<< ": " << CurByte-CurBlock << " bytes of text\n");
}
void Emitter::emitConstantPool(MachineConstantPool *MCP) {
const std::vector<Constant*> &Constants = MCP->getConstants();
if (Constants.empty()) return;
std::vector<unsigned> ConstantOffset;
ConstantOffset.reserve(Constants.size());
// Calculate how much space we will need for all the constants, and the offset
// each one will live in.
unsigned TotalSize = 0;
for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
const Type *Ty = Constants[i]->getType();
unsigned Size = TheJIT->getTargetData().getTypeSize(Ty);
unsigned Alignment = TheJIT->getTargetData().getTypeAlignment(Ty);
// Make sure to take into account the alignment requirements of the type.
TotalSize = (TotalSize + Alignment-1) & ~(Alignment-1);
// Remember the offset this element lives at.
ConstantOffset.push_back(TotalSize);
TotalSize += Size; // Reserve space for the constant.
}
// Now that we know how much memory to allocate, do so.
char *Pool = new char[TotalSize];
// Actually output all of the constants, and remember their addresses.
for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
void *Addr = Pool + ConstantOffset[i];
TheJIT->InitializeMemory(Constants[i], Addr);
ConstantPoolAddresses.push_back(Addr);
}
}
void Emitter::startFunctionStub(const Function &F, unsigned StubSize) {
SavedCurBlock = CurBlock; SavedCurByte = CurByte;
CurByte = CurBlock = MemMgr.allocateStub(StubSize);
}
void *Emitter::finishFunctionStub(const Function &F) {
NumBytes += CurByte-CurBlock;
DEBUG(std::cerr << "Finished CodeGen of [0x" << std::hex
<< (unsigned)(intptr_t)CurBlock
<< std::dec << "] Function stub for: " << F.getName()
<< ": " << CurByte-CurBlock << " bytes of text\n");
std::swap(CurBlock, SavedCurBlock);
CurByte = SavedCurByte;
return SavedCurBlock;
}
void Emitter::emitByte(unsigned char B) {
*CurByte++ = B; // Write the byte to memory
}
void Emitter::emitWord(unsigned W) {
// This won't work if the endianness of the host and target don't agree! (For
// a JIT this can't happen though. :)
*(unsigned*)CurByte = W;
CurByte += sizeof(unsigned);
}
void Emitter::emitWordAt(unsigned W, unsigned *Ptr) {
*Ptr = W;
}
uint64_t Emitter::getGlobalValueAddress(GlobalValue *V) {
// Try looking up the function to see if it is already compiled, if not return
// 0.
if (isa<Function>(V))
return (intptr_t)TheJIT->getPointerToGlobalIfAvailable(V);
else {
return (intptr_t)TheJIT->getOrEmitGlobalVariable(cast<GlobalVariable>(V));
}
}
uint64_t Emitter::getGlobalValueAddress(const std::string &Name) {
return (intptr_t)TheJIT->getPointerToNamedFunction(Name);
}
// getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
// in the constant pool that was last emitted with the 'emitConstantPool'
// method.
//
uint64_t Emitter::getConstantPoolEntryAddress(unsigned ConstantNum) {
assert(ConstantNum < ConstantPoolAddresses.size() &&
"Invalid ConstantPoolIndex!");
return (intptr_t)ConstantPoolAddresses[ConstantNum];
}
// getCurrentPCValue - This returns the address that the next emitted byte
// will be output to.
//
uint64_t Emitter::getCurrentPCValue() {
return (intptr_t)CurByte;
}
uint64_t Emitter::forceCompilationOf(Function *F) {
return (intptr_t)TheJIT->getPointerToFunction(F);
}
// getPointerToNamedFunction - This function is used as a global wrapper to
// JIT::getPointerToNamedFunction for the purpose of resolving symbols when
// bugpoint is debugging the JIT. In that scenario, we are loading an .so and
// need to resolve function(s) that are being mis-codegenerated, so we need to
// resolve their addresses at runtime, and this is the way to do it.
extern "C" {
void *getPointerToNamedFunction(const char *Name) {
Module &M = TheJIT->getModule();
if (Function *F = M.getNamedFunction(Name))
return TheJIT->getPointerToFunction(F);
return TheJIT->getPointerToNamedFunction(Name);
}
}