llvm-6502/lib/ExecutionEngine/JIT/JITEmitter.cpp
2006-02-09 04:49:59 +00:00

653 lines
24 KiB
C++

//===-- JITEmitter.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 the JIT to
// write machine code to memory and remember where relocatable values are.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "jit"
#include "JIT.h"
#include "llvm/Constant.h"
#include "llvm/Module.h"
#include "llvm/Type.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineRelocation.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetJITInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/System/Memory.h"
#include <algorithm>
#include <iostream>
#include <list>
using namespace llvm;
namespace {
Statistic<> NumBytes("jit", "Number of bytes of machine code compiled");
Statistic<> NumRelos("jit", "Number of relocations applied");
JIT *TheJIT = 0;
}
//===----------------------------------------------------------------------===//
// JITMemoryManager code.
//
namespace {
/// 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 {
std::list<sys::MemoryBlock> Blocks; // List of blocks allocated by the JIT
unsigned char *FunctionBase; // Start of the function body area
unsigned char *GlobalBase; // Start of the Global area
unsigned char *ConstantBase; // Memory allocated for constant pools
unsigned char *CurStubPtr, *CurFunctionPtr, *CurConstantPtr, *CurGlobalPtr;
unsigned char *GOTBase; //Target Specific reserved memory
// centralize memory block allocation
sys::MemoryBlock getNewMemoryBlock(unsigned size);
public:
JITMemoryManager(bool useGOT);
~JITMemoryManager();
inline unsigned char *allocateStub(unsigned StubSize);
inline unsigned char *allocateConstant(unsigned ConstantSize,
unsigned Alignment);
inline unsigned char* allocateGlobal(unsigned Size,
unsigned Alignment);
inline unsigned char *startFunctionBody();
inline void endFunctionBody(unsigned char *FunctionEnd);
inline unsigned char* getGOTBase() const;
inline bool isManagingGOT() const;
};
}
JITMemoryManager::JITMemoryManager(bool useGOT) {
// Allocate a 16M block of memory for functions
sys::MemoryBlock FunBlock = getNewMemoryBlock(16 << 20);
// Allocate a 1M block of memory for Constants
sys::MemoryBlock ConstBlock = getNewMemoryBlock(1 << 20);
// Allocate a 1M Block of memory for Globals
sys::MemoryBlock GVBlock = getNewMemoryBlock(1 << 20);
Blocks.push_front(FunBlock);
Blocks.push_front(ConstBlock);
Blocks.push_front(GVBlock);
FunctionBase = reinterpret_cast<unsigned char*>(FunBlock.base());
ConstantBase = reinterpret_cast<unsigned char*>(ConstBlock.base());
GlobalBase = reinterpret_cast<unsigned char*>(GVBlock.base());
// Allocate stubs backwards from the base, allocate functions forward
// from the base.
CurStubPtr = CurFunctionPtr = FunctionBase + 512*1024;// Use 512k for stubs
CurConstantPtr = ConstantBase + ConstBlock.size();
CurGlobalPtr = GlobalBase + GVBlock.size();
//Allocate the GOT just like a global array
GOTBase = NULL;
if (useGOT)
GOTBase = allocateGlobal(sizeof(void*) * 8192, 8);
}
JITMemoryManager::~JITMemoryManager() {
for (std::list<sys::MemoryBlock>::iterator ib = Blocks.begin(),
ie = Blocks.end(); ib != ie; ++ib)
sys::Memory::ReleaseRWX(*ib);
Blocks.clear();
}
unsigned char *JITMemoryManager::allocateStub(unsigned StubSize) {
CurStubPtr -= StubSize;
if (CurStubPtr < FunctionBase) {
//FIXME: allocate a new block
std::cerr << "JIT ran out of memory for function stubs!\n";
abort();
}
return CurStubPtr;
}
unsigned char *JITMemoryManager::allocateConstant(unsigned ConstantSize,
unsigned Alignment) {
// Reserve space and align pointer.
CurConstantPtr -= ConstantSize;
CurConstantPtr =
(unsigned char *)((intptr_t)CurConstantPtr & ~((intptr_t)Alignment - 1));
if (CurConstantPtr < ConstantBase) {
//Either allocate another MB or 2xConstantSize
sys::MemoryBlock ConstBlock = getNewMemoryBlock(2 * ConstantSize);
ConstantBase = reinterpret_cast<unsigned char*>(ConstBlock.base());
CurConstantPtr = ConstantBase + ConstBlock.size();
return allocateConstant(ConstantSize, Alignment);
}
return CurConstantPtr;
}
unsigned char *JITMemoryManager::allocateGlobal(unsigned Size,
unsigned Alignment) {
// Reserve space and align pointer.
CurGlobalPtr -= Size;
CurGlobalPtr =
(unsigned char *)((intptr_t)CurGlobalPtr & ~((intptr_t)Alignment - 1));
if (CurGlobalPtr < GlobalBase) {
//Either allocate another MB or 2xSize
sys::MemoryBlock GVBlock = getNewMemoryBlock(2 * Size);
GlobalBase = reinterpret_cast<unsigned char*>(GVBlock.base());
CurGlobalPtr = GlobalBase + GVBlock.size();
return allocateGlobal(Size, Alignment);
}
return CurGlobalPtr;
}
unsigned char *JITMemoryManager::startFunctionBody() {
// Round up to an even multiple of 8 bytes, this should eventually be target
// specific.
return (unsigned char*)(((intptr_t)CurFunctionPtr + 7) & ~7);
}
void JITMemoryManager::endFunctionBody(unsigned char *FunctionEnd) {
assert(FunctionEnd > CurFunctionPtr);
CurFunctionPtr = FunctionEnd;
}
unsigned char* JITMemoryManager::getGOTBase() const {
return GOTBase;
}
bool JITMemoryManager::isManagingGOT() const {
return GOTBase != NULL;
}
sys::MemoryBlock JITMemoryManager::getNewMemoryBlock(unsigned size) {
const sys::MemoryBlock* BOld = 0;
if (Blocks.size())
BOld = &Blocks.front();
//never allocate less than 1 MB
sys::MemoryBlock B;
try {
B = sys::Memory::AllocateRWX(std::max(((unsigned)1 << 20), size), BOld);
} catch (std::string& err) {
std::cerr << "Allocation failed when allocating new memory in the JIT\n";
std::cerr << err << "\n";
abort();
}
Blocks.push_front(B);
return B;
}
//===----------------------------------------------------------------------===//
// JIT lazy compilation code.
//
namespace {
class JITResolverState {
private:
/// FunctionToStubMap - Keep track of the stub created for a particular
/// function so that we can reuse them if necessary.
std::map<Function*, void*> FunctionToStubMap;
/// StubToFunctionMap - Keep track of the function that each stub
/// corresponds to.
std::map<void*, Function*> StubToFunctionMap;
public:
std::map<Function*, void*>& getFunctionToStubMap(const MutexGuard& locked) {
assert(locked.holds(TheJIT->lock));
return FunctionToStubMap;
}
std::map<void*, Function*>& getStubToFunctionMap(const MutexGuard& locked) {
assert(locked.holds(TheJIT->lock));
return StubToFunctionMap;
}
};
/// JITResolver - Keep track of, and resolve, call sites for functions that
/// have not yet been compiled.
class JITResolver {
/// MCE - The MachineCodeEmitter to use to emit stubs with.
MachineCodeEmitter &MCE;
/// LazyResolverFn - The target lazy resolver function that we actually
/// rewrite instructions to use.
TargetJITInfo::LazyResolverFn LazyResolverFn;
JITResolverState state;
/// ExternalFnToStubMap - This is the equivalent of FunctionToStubMap for
/// external functions.
std::map<void*, void*> ExternalFnToStubMap;
//map addresses to indexes in the GOT
std::map<void*, unsigned> revGOTMap;
unsigned nextGOTIndex;
public:
JITResolver(MachineCodeEmitter &mce) : MCE(mce), nextGOTIndex(0) {
LazyResolverFn =
TheJIT->getJITInfo().getLazyResolverFunction(JITCompilerFn);
}
/// getFunctionStub - This returns a pointer to a function stub, creating
/// one on demand as needed.
void *getFunctionStub(Function *F);
/// getExternalFunctionStub - Return a stub for the function at the
/// specified address, created lazily on demand.
void *getExternalFunctionStub(void *FnAddr);
/// AddCallbackAtLocation - If the target is capable of rewriting an
/// instruction without the use of a stub, record the location of the use so
/// we know which function is being used at the location.
void *AddCallbackAtLocation(Function *F, void *Location) {
MutexGuard locked(TheJIT->lock);
/// Get the target-specific JIT resolver function.
state.getStubToFunctionMap(locked)[Location] = F;
return (void*)LazyResolverFn;
}
/// getGOTIndexForAddress - Return a new or existing index in the GOT for
/// and address. This function only manages slots, it does not manage the
/// contents of the slots or the memory associated with the GOT.
unsigned getGOTIndexForAddr(void* addr);
/// JITCompilerFn - This function is called to resolve a stub to a compiled
/// address. If the LLVM Function corresponding to the stub has not yet
/// been compiled, this function compiles it first.
static void *JITCompilerFn(void *Stub);
};
}
/// getJITResolver - This function returns the one instance of the JIT resolver.
///
static JITResolver &getJITResolver(MachineCodeEmitter *MCE = 0) {
static JITResolver TheJITResolver(*MCE);
return TheJITResolver;
}
/// getFunctionStub - This returns a pointer to a function stub, creating
/// one on demand as needed.
void *JITResolver::getFunctionStub(Function *F) {
MutexGuard locked(TheJIT->lock);
// If we already have a stub for this function, recycle it.
void *&Stub = state.getFunctionToStubMap(locked)[F];
if (Stub) return Stub;
// Call the lazy resolver function unless we already KNOW it is an external
// function, in which case we just skip the lazy resolution step.
void *Actual = (void*)LazyResolverFn;
if (F->isExternal() && F->hasExternalLinkage())
Actual = TheJIT->getPointerToFunction(F);
// Otherwise, codegen a new stub. For now, the stub will call the lazy
// resolver function.
Stub = TheJIT->getJITInfo().emitFunctionStub(Actual, MCE);
if (Actual != (void*)LazyResolverFn) {
// If we are getting the stub for an external function, we really want the
// address of the stub in the GlobalAddressMap for the JIT, not the address
// of the external function.
TheJIT->updateGlobalMapping(F, Stub);
}
DEBUG(std::cerr << "JIT: Stub emitted at [" << Stub << "] for function '"
<< F->getName() << "'\n");
// Finally, keep track of the stub-to-Function mapping so that the
// JITCompilerFn knows which function to compile!
state.getStubToFunctionMap(locked)[Stub] = F;
return Stub;
}
/// getExternalFunctionStub - Return a stub for the function at the
/// specified address, created lazily on demand.
void *JITResolver::getExternalFunctionStub(void *FnAddr) {
// If we already have a stub for this function, recycle it.
void *&Stub = ExternalFnToStubMap[FnAddr];
if (Stub) return Stub;
Stub = TheJIT->getJITInfo().emitFunctionStub(FnAddr, MCE);
DEBUG(std::cerr << "JIT: Stub emitted at [" << Stub
<< "] for external function at '" << FnAddr << "'\n");
return Stub;
}
unsigned JITResolver::getGOTIndexForAddr(void* addr) {
unsigned idx = revGOTMap[addr];
if (!idx) {
idx = ++nextGOTIndex;
revGOTMap[addr] = idx;
DEBUG(std::cerr << "Adding GOT entry " << idx
<< " for addr " << addr << "\n");
// ((void**)MemMgr.getGOTBase())[idx] = addr;
}
return idx;
}
/// JITCompilerFn - This function is called when a lazy compilation stub has
/// been entered. It looks up which function this stub corresponds to, compiles
/// it if necessary, then returns the resultant function pointer.
void *JITResolver::JITCompilerFn(void *Stub) {
JITResolver &JR = getJITResolver();
MutexGuard locked(TheJIT->lock);
// The address given to us for the stub may not be exactly right, it might be
// a little bit after the stub. As such, use upper_bound to find it.
std::map<void*, Function*>::iterator I =
JR.state.getStubToFunctionMap(locked).upper_bound(Stub);
assert(I != JR.state.getStubToFunctionMap(locked).begin() &&
"This is not a known stub!");
Function *F = (--I)->second;
// We might like to remove the stub from the StubToFunction map.
// We can't do that! Multiple threads could be stuck, waiting to acquire the
// lock above. As soon as the 1st function finishes compiling the function,
// the next one will be released, and needs to be able to find the function it
// needs to call.
//JR.state.getStubToFunctionMap(locked).erase(I);
DEBUG(std::cerr << "JIT: Lazily resolving function '" << F->getName()
<< "' In stub ptr = " << Stub << " actual ptr = "
<< I->first << "\n");
void *Result = TheJIT->getPointerToFunction(F);
// We don't need to reuse this stub in the future, as F is now compiled.
JR.state.getFunctionToStubMap(locked).erase(F);
// FIXME: We could rewrite all references to this stub if we knew them.
// What we will do is set the compiled function address to map to the
// same GOT entry as the stub so that later clients may update the GOT
// if they see it still using the stub address.
// Note: this is done so the Resolver doesn't have to manage GOT memory
// Do this without allocating map space if the target isn't using a GOT
if(JR.revGOTMap.find(Stub) != JR.revGOTMap.end())
JR.revGOTMap[Result] = JR.revGOTMap[Stub];
return Result;
}
// getPointerToFunctionOrStub - If the specified function has been
// code-gen'd, return a pointer to the function. If not, compile it, or use
// a stub to implement lazy compilation if available.
//
void *JIT::getPointerToFunctionOrStub(Function *F) {
// If we have already code generated the function, just return the address.
if (void *Addr = getPointerToGlobalIfAvailable(F))
return Addr;
// Get a stub if the target supports it
return getJITResolver(MCE).getFunctionStub(F);
}
//===----------------------------------------------------------------------===//
// JITEmitter code.
//
namespace {
/// JITEmitter - The JIT implementation of the MachineCodeEmitter, which is
/// used to output functions to memory for execution.
class JITEmitter : 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;
/// Relocations - These are the relocations that the function needs, as
/// emitted.
std::vector<MachineRelocation> Relocations;
/// ConstantPool - The constant pool for the current function.
///
MachineConstantPool *ConstantPool;
/// ConstantPoolBase - A pointer to the first entry in the constant pool.
///
void *ConstantPoolBase;
public:
JITEmitter(JIT &jit) : MemMgr(jit.getJITInfo().needsGOT()) {
TheJIT = &jit;
DEBUG(std::cerr <<
(MemMgr.isManagingGOT() ? "JIT is managing GOT\n"
: "JIT is not managing GOT\n"));
}
virtual void startFunction(MachineFunction &F);
virtual void finishFunction(MachineFunction &F);
virtual void emitConstantPool(MachineConstantPool *MCP);
virtual void startFunctionStub(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 void addRelocation(const MachineRelocation &MR) {
Relocations.push_back(MR);
}
virtual uint64_t getCurrentPCValue();
virtual uint64_t getCurrentPCOffset();
virtual uint64_t getConstantPoolEntryAddress(unsigned Entry);
virtual unsigned char* allocateGlobal(unsigned size, unsigned alignment);
private:
void *getPointerToGlobal(GlobalValue *GV, void *Reference, bool NoNeedStub);
};
}
MachineCodeEmitter *JIT::createEmitter(JIT &jit) {
return new JITEmitter(jit);
}
void *JITEmitter::getPointerToGlobal(GlobalValue *V, void *Reference,
bool DoesntNeedStub) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
/// FIXME: If we straightened things out, this could actually emit the
/// global immediately instead of queuing it for codegen later!
return TheJIT->getOrEmitGlobalVariable(GV);
}
// If we have already compiled the function, return a pointer to its body.
Function *F = cast<Function>(V);
void *ResultPtr = TheJIT->getPointerToGlobalIfAvailable(F);
if (ResultPtr) return ResultPtr;
if (F->hasExternalLinkage() && F->isExternal()) {
// If this is an external function pointer, we can force the JIT to
// 'compile' it, which really just adds it to the map.
if (DoesntNeedStub)
return TheJIT->getPointerToFunction(F);
return getJITResolver(this).getFunctionStub(F);
}
// Okay, the function has not been compiled yet, if the target callback
// mechanism is capable of rewriting the instruction directly, prefer to do
// that instead of emitting a stub.
if (DoesntNeedStub)
return getJITResolver(this).AddCallbackAtLocation(F, Reference);
// Otherwise, we have to emit a lazy resolving stub.
return getJITResolver(this).getFunctionStub(F);
}
void JITEmitter::startFunction(MachineFunction &F) {
CurByte = CurBlock = MemMgr.startFunctionBody();
TheJIT->addGlobalMapping(F.getFunction(), CurBlock);
}
void JITEmitter::finishFunction(MachineFunction &F) {
MemMgr.endFunctionBody(CurByte);
NumBytes += CurByte-CurBlock;
if (!Relocations.empty()) {
NumRelos += Relocations.size();
// Resolve the relocations to concrete pointers.
for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
MachineRelocation &MR = Relocations[i];
void *ResultPtr;
if (MR.isString()) {
ResultPtr = TheJIT->getPointerToNamedFunction(MR.getString());
// If the target REALLY wants a stub for this function, emit it now.
if (!MR.doesntNeedFunctionStub())
ResultPtr = getJITResolver(this).getExternalFunctionStub(ResultPtr);
} else if (MR.isGlobalValue())
ResultPtr = getPointerToGlobal(MR.getGlobalValue(),
CurBlock+MR.getMachineCodeOffset(),
MR.doesntNeedFunctionStub());
else //ConstantPoolIndex
ResultPtr =
(void*)(intptr_t)getConstantPoolEntryAddress(MR.getConstantPoolIndex());
MR.setResultPointer(ResultPtr);
// if we are managing the GOT and the relocation wants an index,
// give it one
if (MemMgr.isManagingGOT() && !MR.isConstantPoolIndex() &&
MR.isGOTRelative()) {
unsigned idx = getJITResolver(this).getGOTIndexForAddr(ResultPtr);
MR.setGOTIndex(idx);
if (((void**)MemMgr.getGOTBase())[idx] != ResultPtr) {
DEBUG(std::cerr << "GOT was out of date for " << ResultPtr
<< " pointing at " << ((void**)MemMgr.getGOTBase())[idx]
<< "\n");
((void**)MemMgr.getGOTBase())[idx] = ResultPtr;
}
}
}
TheJIT->getJITInfo().relocate(CurBlock, &Relocations[0],
Relocations.size(), MemMgr.getGOTBase());
}
//Update the GOT entry for F to point to the new code.
if(MemMgr.isManagingGOT()) {
unsigned idx = getJITResolver(this).getGOTIndexForAddr((void*)CurBlock);
if (((void**)MemMgr.getGOTBase())[idx] != (void*)CurBlock) {
DEBUG(std::cerr << "GOT was out of date for " << (void*)CurBlock
<< " pointing at " << ((void**)MemMgr.getGOTBase())[idx] << "\n");
((void**)MemMgr.getGOTBase())[idx] = (void*)CurBlock;
}
}
DEBUG(std::cerr << "JIT: Finished CodeGen of [" << (void*)CurBlock
<< "] Function: " << F.getFunction()->getName()
<< ": " << CurByte-CurBlock << " bytes of text, "
<< Relocations.size() << " relocations\n");
Relocations.clear();
}
void JITEmitter::emitConstantPool(MachineConstantPool *MCP) {
const std::vector<MachineConstantPoolEntry> &Constants = MCP->getConstants();
if (Constants.empty()) return;
unsigned Size = Constants.back().Offset;
Size += TheJIT->getTargetData().getTypeSize(Constants.back().Val->getType());
ConstantPoolBase = MemMgr.allocateConstant(Size,
1 << MCP->getConstantPoolAlignment());
ConstantPool = MCP;
// Initialize the memory for all of the constant pool entries.
for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
void *CAddr = (char*)ConstantPoolBase+Constants[i].Offset;
TheJIT->InitializeMemory(Constants[i].Val, CAddr);
}
}
void JITEmitter::startFunctionStub(unsigned StubSize) {
SavedCurBlock = CurBlock; SavedCurByte = CurByte;
CurByte = CurBlock = MemMgr.allocateStub(StubSize);
}
void *JITEmitter::finishFunctionStub(const Function *F) {
NumBytes += CurByte-CurBlock;
std::swap(CurBlock, SavedCurBlock);
CurByte = SavedCurByte;
return SavedCurBlock;
}
void JITEmitter::emitByte(unsigned char B) {
*CurByte++ = B; // Write the byte to memory
}
void JITEmitter::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 JITEmitter::emitWordAt(unsigned W, unsigned *Ptr) {
*Ptr = W;
}
// getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
// in the constant pool that was last emitted with the 'emitConstantPool'
// method.
//
uint64_t JITEmitter::getConstantPoolEntryAddress(unsigned ConstantNum) {
assert(ConstantNum < ConstantPool->getConstants().size() &&
"Invalid ConstantPoolIndex!");
return (intptr_t)ConstantPoolBase +
ConstantPool->getConstants()[ConstantNum].Offset;
}
unsigned char* JITEmitter::allocateGlobal(unsigned size, unsigned alignment)
{
return MemMgr.allocateGlobal(size, alignment);
}
// getCurrentPCValue - This returns the address that the next emitted byte
// will be output to.
//
uint64_t JITEmitter::getCurrentPCValue() {
return (intptr_t)CurByte;
}
uint64_t JITEmitter::getCurrentPCOffset() {
return (intptr_t)CurByte-(intptr_t)CurBlock;
}
// 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);
}
}