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//===-- JITEmitter.cpp - Write machine code to executable memory ----------===//
// The LLVM Compiler Infrastructure
// This file 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 "JITDwarfEmitter.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/Constants.h"
#include "llvm/Module.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Analysis/DebugInfo.h"
#include "llvm/CodeGen/JITCodeEmitter.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineCodeInfo.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRelocation.h"
#include "llvm/ExecutionEngine/GenericValue.h"
#include "llvm/ExecutionEngine/JITEventListener.h"
#include "llvm/ExecutionEngine/JITMemoryManager.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetJITInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/MutexGuard.h"
#include "llvm/Support/ValueHandle.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/Disassembler.h"
#include "llvm/Support/Memory.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/ValueMap.h"
#include <algorithm>
#ifndef NDEBUG
#include <iomanip>
using namespace llvm;
STATISTIC(NumBytes, "Number of bytes of machine code compiled");
STATISTIC(NumRelos, "Number of relocations applied");
STATISTIC(NumRetries, "Number of retries with more memory");
// A declaration may stop being a declaration once it's fully read from bitcode.
// This function returns true if F is fully read and is still a declaration.
static bool isNonGhostDeclaration(const Function *F) {
return F->isDeclaration() && !F->isMaterializable();
// JIT lazy compilation code.
namespace {
class JITEmitter;
class JITResolverState;
template<typename ValueTy>
struct NoRAUWValueMapConfig : public ValueMapConfig<ValueTy> {
typedef JITResolverState *ExtraData;
static void onRAUW(JITResolverState *, Value *Old, Value *New) {
llvm_unreachable("The JIT doesn't know how to handle a"
" RAUW on a value it has emitted.");
struct CallSiteValueMapConfig : public NoRAUWValueMapConfig<Function*> {
typedef JITResolverState *ExtraData;
static void onDelete(JITResolverState *JRS, Function *F);
class JITResolverState {
typedef ValueMap<Function*, void*, NoRAUWValueMapConfig<Function*> >
typedef std::map<void*, AssertingVH<Function> > CallSiteToFunctionMapTy;
typedef ValueMap<Function *, SmallPtrSet<void*, 1>,
CallSiteValueMapConfig> FunctionToCallSitesMapTy;
typedef std::map<AssertingVH<GlobalValue>, void*> GlobalToIndirectSymMapTy;
/// FunctionToLazyStubMap - Keep track of the lazy stub created for a
/// particular function so that we can reuse them if necessary.
FunctionToLazyStubMapTy FunctionToLazyStubMap;
/// CallSiteToFunctionMap - Keep track of the function that each lazy call
/// site corresponds to, and vice versa.
CallSiteToFunctionMapTy CallSiteToFunctionMap;
FunctionToCallSitesMapTy FunctionToCallSitesMap;
/// GlobalToIndirectSymMap - Keep track of the indirect symbol created for a
/// particular GlobalVariable so that we can reuse them if necessary.
GlobalToIndirectSymMapTy GlobalToIndirectSymMap;
/// Instance of the JIT this ResolverState serves.
JITResolverState(JIT *jit) : FunctionToLazyStubMap(this),
TheJIT(jit) {}
FunctionToLazyStubMapTy& getFunctionToLazyStubMap(
const MutexGuard& locked) {
return FunctionToLazyStubMap;
GlobalToIndirectSymMapTy& getGlobalToIndirectSymMap(const MutexGuard& lck) {
return GlobalToIndirectSymMap;
std::pair<void *, Function *> LookupFunctionFromCallSite(
const MutexGuard &locked, void *CallSite) const {
// 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.
CallSiteToFunctionMapTy::const_iterator I =
assert(I != CallSiteToFunctionMap.begin() &&
"This is not a known call site!");
return *I;
void AddCallSite(const MutexGuard &locked, void *CallSite, Function *F) {
bool Inserted = CallSiteToFunctionMap.insert(
std::make_pair(CallSite, F)).second;
assert(Inserted && "Pair was already in CallSiteToFunctionMap");
void EraseAllCallSitesForPrelocked(Function *F);
// Erases _all_ call sites regardless of their function. This is used to
// unregister the stub addresses from the StubToResolverMap in
// ~JITResolver().
void EraseAllCallSitesPrelocked();
/// JITResolver - Keep track of, and resolve, call sites for functions that
/// have not yet been compiled.
class JITResolver {
typedef JITResolverState::FunctionToLazyStubMapTy FunctionToLazyStubMapTy;
typedef JITResolverState::CallSiteToFunctionMapTy CallSiteToFunctionMapTy;
typedef JITResolverState::GlobalToIndirectSymMapTy GlobalToIndirectSymMapTy;
/// LazyResolverFn - The target lazy resolver function that we actually
/// rewrite instructions to use.
TargetJITInfo::LazyResolverFn LazyResolverFn;
JITResolverState state;
/// ExternalFnToStubMap - This is the equivalent of FunctionToLazyStubMap
/// for external functions. TODO: Of course, external functions don't need
/// a lazy stub. It's actually here to make it more likely that far calls
/// succeed, but no single stub can guarantee that. I'll remove this in a
/// subsequent checkin when I actually fix far calls.
std::map<void*, void*> ExternalFnToStubMap;
/// revGOTMap - map addresses to indexes in the GOT
std::map<void*, unsigned> revGOTMap;
unsigned nextGOTIndex;
JITEmitter &JE;
/// Instance of JIT corresponding to this Resolver.
explicit JITResolver(JIT &jit, JITEmitter &je)
: state(&jit), nextGOTIndex(0), JE(je), TheJIT(&jit) {
LazyResolverFn = jit.getJITInfo().getLazyResolverFunction(JITCompilerFn);
/// getLazyFunctionStubIfAvailable - This returns a pointer to a function's
/// lazy-compilation stub if it has already been created.
void *getLazyFunctionStubIfAvailable(Function *F);
/// getLazyFunctionStub - This returns a pointer to a function's
/// lazy-compilation stub, creating one on demand as needed.
void *getLazyFunctionStub(Function *F);
/// getExternalFunctionStub - Return a stub for the function at the
/// specified address, created lazily on demand.
void *getExternalFunctionStub(void *FnAddr);
/// getGlobalValueIndirectSym - Return an indirect symbol containing the
/// specified GV address.
void *getGlobalValueIndirectSym(GlobalValue *V, void *GVAddress);
/// getGOTIndexForAddress - Return a new or existing index in the GOT for
/// an 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);
class StubToResolverMapTy {
/// Map a stub address to a specific instance of a JITResolver so that
/// lazily-compiled functions can find the right resolver to use.
/// Guarded by Lock.
std::map<void*, JITResolver*> Map;
/// Guards Map from concurrent accesses.
mutable sys::Mutex Lock;
/// Registers a Stub to be resolved by Resolver.
void RegisterStubResolver(void *Stub, JITResolver *Resolver) {
MutexGuard guard(Lock);
Map.insert(std::make_pair(Stub, Resolver));
/// Unregisters the Stub when it's invalidated.
void UnregisterStubResolver(void *Stub) {
MutexGuard guard(Lock);
/// Returns the JITResolver instance that owns the Stub.
JITResolver *getResolverFromStub(void *Stub) const {
MutexGuard guard(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.
// This is the same trick as in LookupFunctionFromCallSite from
// JITResolverState.
std::map<void*, JITResolver*>::const_iterator I = Map.upper_bound(Stub);
assert(I != Map.begin() && "This is not a known stub!");
return I->second;
/// True if any stubs refer to the given resolver. Only used in an assert().
/// O(N)
bool ResolverHasStubs(JITResolver* Resolver) const {
MutexGuard guard(Lock);
for (std::map<void*, JITResolver*>::const_iterator I = Map.begin(),
E = Map.end(); I != E; ++I) {
if (I->second == Resolver)
return true;
return false;
/// This needs to be static so that a lazy call stub can access it with no
/// context except the address of the stub.
ManagedStatic<StubToResolverMapTy> StubToResolverMap;
/// JITEmitter - The JIT implementation of the MachineCodeEmitter, which is
/// used to output functions to memory for execution.
class JITEmitter : public JITCodeEmitter {
JITMemoryManager *MemMgr;
// When outputting a function stub in the context of some other function, we
// save BufferBegin/BufferEnd/CurBufferPtr here.
uint8_t *SavedBufferBegin, *SavedBufferEnd, *SavedCurBufferPtr;
// When reattempting to JIT a function after running out of space, we store
// the estimated size of the function we're trying to JIT here, so we can
// ask the memory manager for at least this much space. When we
// successfully emit the function, we reset this back to zero.
uintptr_t SizeEstimate;
/// Relocations - These are the relocations that the function needs, as
/// emitted.
std::vector<MachineRelocation> Relocations;
/// MBBLocations - This vector is a mapping from MBB ID's to their address.
/// It is filled in by the StartMachineBasicBlock callback and queried by
/// the getMachineBasicBlockAddress callback.
std::vector<uintptr_t> MBBLocations;
/// ConstantPool - The constant pool for the current function.
MachineConstantPool *ConstantPool;
/// ConstantPoolBase - A pointer to the first entry in the constant pool.
void *ConstantPoolBase;
/// ConstPoolAddresses - Addresses of individual constant pool entries.
SmallVector<uintptr_t, 8> ConstPoolAddresses;
/// JumpTable - The jump tables for the current function.
MachineJumpTableInfo *JumpTable;
/// JumpTableBase - A pointer to the first entry in the jump table.
void *JumpTableBase;
/// Resolver - This contains info about the currently resolved functions.
JITResolver Resolver;
/// DE - The dwarf emitter for the jit.
OwningPtr<JITDwarfEmitter> DE;
/// LabelLocations - This vector is a mapping from Label ID's to their
/// address.
DenseMap<MCSymbol*, uintptr_t> LabelLocations;
/// MMI - Machine module info for exception informations
MachineModuleInfo* MMI;
// CurFn - The llvm function being emitted. Only valid during
// finishFunction().
const Function *CurFn;
/// Information about emitted code, which is passed to the
/// JITEventListeners. This is reset in startFunction and used in
/// finishFunction.
JITEvent_EmittedFunctionDetails EmissionDetails;
struct EmittedCode {
void *FunctionBody; // Beginning of the function's allocation.
void *Code; // The address the function's code actually starts at.
void *ExceptionTable;
EmittedCode() : FunctionBody(0), Code(0), ExceptionTable(0) {}
struct EmittedFunctionConfig : public ValueMapConfig<const Function*> {
typedef JITEmitter *ExtraData;
static void onDelete(JITEmitter *, const Function*);
static void onRAUW(JITEmitter *, const Function*, const Function*);
ValueMap<const Function *, EmittedCode,
EmittedFunctionConfig> EmittedFunctions;
DebugLoc PrevDL;
/// Instance of the JIT
bool JITExceptionHandling;
JITEmitter(JIT &jit, JITMemoryManager *JMM, TargetMachine &TM)
: SizeEstimate(0), Resolver(jit, *this), MMI(0), CurFn(0),
EmittedFunctions(this), TheJIT(&jit),
JITExceptionHandling(TM.Options.JITExceptionHandling) {
MemMgr = JMM ? JMM : JITMemoryManager::CreateDefaultMemManager();
if (jit.getJITInfo().needsGOT()) {
DEBUG(dbgs() << "JIT is managing a GOT\n");
if (JITExceptionHandling) {
DE.reset(new JITDwarfEmitter(jit));
~JITEmitter() {
delete MemMgr;
/// classof - Methods for support type inquiry through isa, cast, and
/// dyn_cast:
static inline bool classof(const MachineCodeEmitter*) { return true; }
JITResolver &getJITResolver() { return Resolver; }
virtual void startFunction(MachineFunction &F);
virtual bool finishFunction(MachineFunction &F);
void emitConstantPool(MachineConstantPool *MCP);
void initJumpTableInfo(MachineJumpTableInfo *MJTI);
void emitJumpTableInfo(MachineJumpTableInfo *MJTI);
void startGVStub(const GlobalValue* GV,
unsigned StubSize, unsigned Alignment = 1);
void startGVStub(void *Buffer, unsigned StubSize);
void finishGVStub();
virtual void *allocIndirectGV(const GlobalValue *GV,
const uint8_t *Buffer, size_t Size,
unsigned Alignment);
/// allocateSpace - Reserves space in the current block if any, or
/// allocate a new one of the given size.
virtual void *allocateSpace(uintptr_t Size, unsigned Alignment);
/// allocateGlobal - Allocate memory for a global. Unlike allocateSpace,
/// this method does not allocate memory in the current output buffer,
/// because a global may live longer than the current function.
virtual void *allocateGlobal(uintptr_t Size, unsigned Alignment);
virtual void addRelocation(const MachineRelocation &MR) {
virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) {
if (MBBLocations.size() <= (unsigned)MBB->getNumber())
MBBLocations[MBB->getNumber()] = getCurrentPCValue();
if (MBB->hasAddressTaken())
DEBUG(dbgs() << "JIT: Emitting BB" << MBB->getNumber() << " at ["
<< (void*) getCurrentPCValue() << "]\n");
virtual uintptr_t getConstantPoolEntryAddress(unsigned Entry) const;
virtual uintptr_t getJumpTableEntryAddress(unsigned Entry) const;
virtual uintptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const{
assert(MBBLocations.size() > (unsigned)MBB->getNumber() &&
MBBLocations[MBB->getNumber()] && "MBB not emitted!");
return MBBLocations[MBB->getNumber()];
/// retryWithMoreMemory - Log a retry and deallocate all memory for the
/// given function. Increase the minimum allocation size so that we get
/// more memory next time.
void retryWithMoreMemory(MachineFunction &F);
/// deallocateMemForFunction - Deallocate all memory for the specified
/// function body.
void deallocateMemForFunction(const Function *F);
virtual void processDebugLoc(DebugLoc DL, bool BeforePrintingInsn);
virtual void emitLabel(MCSymbol *Label) {
LabelLocations[Label] = getCurrentPCValue();
virtual DenseMap<MCSymbol*, uintptr_t> *getLabelLocations() {
return &LabelLocations;
virtual uintptr_t getLabelAddress(MCSymbol *Label) const {
assert(LabelLocations.count(Label) && "Label not emitted!");
return LabelLocations.find(Label)->second;
virtual void setModuleInfo(MachineModuleInfo* Info) {
MMI = Info;
if (DE.get()) DE->setModuleInfo(Info);
void *getPointerToGlobal(GlobalValue *GV, void *Reference,
bool MayNeedFarStub);
void *getPointerToGVIndirectSym(GlobalValue *V, void *Reference);
void CallSiteValueMapConfig::onDelete(JITResolverState *JRS, Function *F) {
void JITResolverState::EraseAllCallSitesForPrelocked(Function *F) {
FunctionToCallSitesMapTy::iterator F2C = FunctionToCallSitesMap.find(F);
if (F2C == FunctionToCallSitesMap.end())
StubToResolverMapTy &S2RMap = *StubToResolverMap;
for (SmallPtrSet<void*, 1>::const_iterator I = F2C->second.begin(),
E = F2C->second.end(); I != E; ++I) {
bool Erased = CallSiteToFunctionMap.erase(*I);
assert(Erased && "Missing call site->function mapping");
void JITResolverState::EraseAllCallSitesPrelocked() {
StubToResolverMapTy &S2RMap = *StubToResolverMap;
for (CallSiteToFunctionMapTy::const_iterator
I = CallSiteToFunctionMap.begin(),
E = CallSiteToFunctionMap.end(); I != E; ++I) {
JITResolver::~JITResolver() {
// No need to lock because we're in the destructor, and state isn't shared.
assert(!StubToResolverMap->ResolverHasStubs(this) &&
"Resolver destroyed with stubs still alive.");
/// getLazyFunctionStubIfAvailable - This returns a pointer to a function stub
/// if it has already been created.
void *JITResolver::getLazyFunctionStubIfAvailable(Function *F) {
MutexGuard locked(TheJIT->lock);
// If we already have a stub for this function, recycle it.
return state.getFunctionToLazyStubMap(locked).lookup(F);
/// getFunctionStub - This returns a pointer to a function stub, creating
/// one on demand as needed.
void *JITResolver::getLazyFunctionStub(Function *F) {
MutexGuard locked(TheJIT->lock);
// If we already have a lazy stub for this function, recycle it.
void *&Stub = state.getFunctionToLazyStubMap(locked)[F];
if (Stub) return Stub;
// Call the lazy resolver function if we are JIT'ing lazily. Otherwise we
// must resolve the symbol now.
void *Actual = TheJIT->isCompilingLazily()
? (void *)(intptr_t)LazyResolverFn : (void *)0;
// If this is an external declaration, attempt to resolve the address now
// to place in the stub.
if (isNonGhostDeclaration(F) || F->hasAvailableExternallyLinkage()) {
Actual = TheJIT->getPointerToFunction(F);
// If we resolved the symbol to a null address (eg. a weak external)
// don't emit a stub. Return a null pointer to the application.
if (!Actual) return 0;
TargetJITInfo::StubLayout SL = TheJIT->getJITInfo().getStubLayout();
JE.startGVStub(F, SL.Size, SL.Alignment);
// Codegen a new stub, calling the lazy resolver or the actual address of the
// external function, if it was resolved.
Stub = TheJIT->getJITInfo().emitFunctionStub(F, Actual, JE);
if (Actual != (void*)(intptr_t)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(dbgs() << "JIT: Lazy stub emitted at [" << Stub << "] for function '"
<< F->getName() << "'\n");
if (TheJIT->isCompilingLazily()) {
// Register this JITResolver as the one corresponding to this call site so
// JITCompilerFn will be able to find it.
StubToResolverMap->RegisterStubResolver(Stub, this);
// Finally, keep track of the stub-to-Function mapping so that the
// JITCompilerFn knows which function to compile!
state.AddCallSite(locked, Stub, F);
} else if (!Actual) {
// If we are JIT'ing non-lazily but need to call a function that does not
// exist yet, add it to the JIT's work list so that we can fill in the
// stub address later.
assert(!isNonGhostDeclaration(F) && !F->hasAvailableExternallyLinkage() &&
"'Actual' should have been set above.");
return Stub;
/// getGlobalValueIndirectSym - Return a lazy pointer containing the specified
/// GV address.
void *JITResolver::getGlobalValueIndirectSym(GlobalValue *GV, void *GVAddress) {
MutexGuard locked(TheJIT->lock);
// If we already have a stub for this global variable, recycle it.
void *&IndirectSym = state.getGlobalToIndirectSymMap(locked)[GV];
if (IndirectSym) return IndirectSym;
// Otherwise, codegen a new indirect symbol.
IndirectSym = TheJIT->getJITInfo().emitGlobalValueIndirectSym(GV, GVAddress,
DEBUG(dbgs() << "JIT: Indirect symbol emitted at [" << IndirectSym
<< "] for GV '" << GV->getName() << "'\n");
return IndirectSym;
/// 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;
TargetJITInfo::StubLayout SL = TheJIT->getJITInfo().getStubLayout();
JE.startGVStub(0, SL.Size, SL.Alignment);
Stub = TheJIT->getJITInfo().emitFunctionStub(0, FnAddr, JE);
DEBUG(dbgs() << "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(dbgs() << "JIT: Adding GOT entry " << idx << " for addr ["
<< addr << "]\n");
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 = StubToResolverMap->getResolverFromStub(Stub);
assert(JR && "Unable to find the corresponding JITResolver to the call site");
Function* F = 0;
void* ActualPtr = 0;
// Only lock for getting the Function. The call getPointerToFunction made
// in this function might trigger function materializing, which requires
// JIT lock to be unlocked.
MutexGuard locked(JR->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::pair<void*, Function*> I =
JR->state.LookupFunctionFromCallSite(locked, Stub);
F = I.second;
ActualPtr = I.first;
// If we have already code generated the function, just return the address.
void *Result = JR->TheJIT->getPointerToGlobalIfAvailable(F);
if (!Result) {
// Otherwise we don't have it, do lazy compilation now.
// If lazy compilation is disabled, emit a useful error message and abort.
if (!JR->TheJIT->isCompilingLazily()) {
report_fatal_error("LLVM JIT requested to do lazy compilation of"
" function '"
+ F->getName() + "' when lazy compiles are disabled!");
DEBUG(dbgs() << "JIT: Lazily resolving function '" << F->getName()
<< "' In stub ptr = " << Stub << " actual ptr = "
<< ActualPtr << "\n");
Result = JR->TheJIT->getPointerToFunction(F);
// Reacquire the lock to update the GOT map.
MutexGuard locked(JR->TheJIT->lock);
// We might like to remove the call site from the CallSiteToFunction map, but
// 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.
// 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;
// JITEmitter code.
void *JITEmitter::getPointerToGlobal(GlobalValue *V, void *Reference,
bool MayNeedFarStub) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
return TheJIT->getOrEmitGlobalVariable(GV);
if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
return TheJIT->getPointerToGlobal(GA->resolveAliasedGlobal(false));
// If we have already compiled the function, return a pointer to its body.
Function *F = cast<Function>(V);
void *FnStub = Resolver.getLazyFunctionStubIfAvailable(F);
if (FnStub) {
// Return the function stub if it's already created. We do this first so
// that we're returning the same address for the function as any previous
// call. TODO: Yes, this is wrong. The lazy stub isn't guaranteed to be
// close enough to call.
return FnStub;
// If we know the target can handle arbitrary-distance calls, try to
// return a direct pointer.
if (!MayNeedFarStub) {
// If we have code, go ahead and return that.
void *ResultPtr = TheJIT->getPointerToGlobalIfAvailable(F);
if (ResultPtr) return ResultPtr;
// If this is an external function pointer, we can force the JIT to
// 'compile' it, which really just adds it to the map.
if (isNonGhostDeclaration(F) || F->hasAvailableExternallyLinkage())
return TheJIT->getPointerToFunction(F);
// Otherwise, we may need a to emit a stub, and, conservatively, we always do
// so. Note that it's possible to return null from getLazyFunctionStub in the
// case of a weak extern that fails to resolve.
return Resolver.getLazyFunctionStub(F);
void *JITEmitter::getPointerToGVIndirectSym(GlobalValue *V, void *Reference) {
// Make sure GV is emitted first, and create a stub containing the fully
// resolved address.
void *GVAddress = getPointerToGlobal(V, Reference, false);
void *StubAddr = Resolver.getGlobalValueIndirectSym(V, GVAddress);
return StubAddr;
void JITEmitter::processDebugLoc(DebugLoc DL, bool BeforePrintingInsn) {
if (DL.isUnknown()) return;
if (!BeforePrintingInsn) return;
const LLVMContext &Context = EmissionDetails.MF->getFunction()->getContext();
if (DL.getScope(Context) != 0 && PrevDL != DL) {
JITEvent_EmittedFunctionDetails::LineStart NextLine;
NextLine.Address = getCurrentPCValue();
NextLine.Loc = DL;
PrevDL = DL;
static unsigned GetConstantPoolSizeInBytes(MachineConstantPool *MCP,
const TargetData *TD) {
const std::vector<MachineConstantPoolEntry> &Constants = MCP->getConstants();
if (Constants.empty()) return 0;
unsigned Size = 0;
for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
MachineConstantPoolEntry CPE = Constants[i];
unsigned AlignMask = CPE.getAlignment() - 1;
Size = (Size + AlignMask) & ~AlignMask;
Type *Ty = CPE.getType();
Size += TD->getTypeAllocSize(Ty);
return Size;
void JITEmitter::startFunction(MachineFunction &F) {
DEBUG(dbgs() << "JIT: Starting CodeGen of Function "
<< F.getFunction()->getName() << "\n");
uintptr_t ActualSize = 0;
// Set the memory writable, if it's not already
if (SizeEstimate > 0) {
// SizeEstimate will be non-zero on reallocation attempts.
ActualSize = SizeEstimate;
BufferBegin = CurBufferPtr = MemMgr->startFunctionBody(F.getFunction(),
BufferEnd = BufferBegin+ActualSize;
EmittedFunctions[F.getFunction()].FunctionBody = BufferBegin;
// Ensure the constant pool/jump table info is at least 4-byte aligned.
if (MachineJumpTableInfo *MJTI = F.getJumpTableInfo())
// About to start emitting the machine code for the function.
emitAlignment(std::max(F.getFunction()->getAlignment(), 8U));
TheJIT->updateGlobalMapping(F.getFunction(), CurBufferPtr);
EmittedFunctions[F.getFunction()].Code = CurBufferPtr;
EmissionDetails.MF = &F;
bool JITEmitter::finishFunction(MachineFunction &F) {
if (CurBufferPtr == BufferEnd) {
// We must call endFunctionBody before retrying, because
// deallocateMemForFunction requires it.
MemMgr->endFunctionBody(F.getFunction(), BufferBegin, CurBufferPtr);
return true;
if (MachineJumpTableInfo *MJTI = F.getJumpTableInfo())
// FnStart is the start of the text, not the start of the constant pool and
// other per-function data.
uint8_t *FnStart =
(uint8_t *)TheJIT->getPointerToGlobalIfAvailable(F.getFunction());
// FnEnd is the end of the function's machine code.
uint8_t *FnEnd = CurBufferPtr;
if (!Relocations.empty()) {
CurFn = F.getFunction();
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 = 0;
if (!MR.letTargetResolve()) {
if (MR.isExternalSymbol()) {
ResultPtr = TheJIT->getPointerToNamedFunction(MR.getExternalSymbol(),
DEBUG(dbgs() << "JIT: Map \'" << MR.getExternalSymbol() << "\' to ["
<< ResultPtr << "]\n");
// If the target REALLY wants a stub for this function, emit it now.
if (MR.mayNeedFarStub()) {
ResultPtr = Resolver.getExternalFunctionStub(ResultPtr);
} else if (MR.isGlobalValue()) {
ResultPtr = getPointerToGlobal(MR.getGlobalValue(),
} else if (MR.isIndirectSymbol()) {
ResultPtr = getPointerToGVIndirectSym(
MR.getGlobalValue(), BufferBegin+MR.getMachineCodeOffset());
} else if (MR.isBasicBlock()) {
ResultPtr = (void*)getMachineBasicBlockAddress(MR.getBasicBlock());
} else if (MR.isConstantPoolIndex()) {
ResultPtr =
} else {
// if we are managing the GOT and the relocation wants an index,
// give it one
if (MR.isGOTRelative() && MemMgr->isManagingGOT()) {
unsigned idx = Resolver.getGOTIndexForAddr(ResultPtr);
if (((void**)MemMgr->getGOTBase())[idx] != ResultPtr) {
DEBUG(dbgs() << "JIT: GOT was out of date for " << ResultPtr
<< " pointing at " << ((void**)MemMgr->getGOTBase())[idx]
<< "\n");
((void**)MemMgr->getGOTBase())[idx] = ResultPtr;
CurFn = 0;
TheJIT->getJITInfo().relocate(BufferBegin, &Relocations[0],
Relocations.size(), MemMgr->getGOTBase());
// Update the GOT entry for F to point to the new code.
if (MemMgr->isManagingGOT()) {
unsigned idx = Resolver.getGOTIndexForAddr((void*)BufferBegin);
if (((void**)MemMgr->getGOTBase())[idx] != (void*)BufferBegin) {
DEBUG(dbgs() << "JIT: GOT was out of date for " << (void*)BufferBegin
<< " pointing at " << ((void**)MemMgr->getGOTBase())[idx]
<< "\n");
((void**)MemMgr->getGOTBase())[idx] = (void*)BufferBegin;
// CurBufferPtr may have moved beyond FnEnd, due to memory allocation for
// global variables that were referenced in the relocations.
MemMgr->endFunctionBody(F.getFunction(), BufferBegin, CurBufferPtr);
if (CurBufferPtr == BufferEnd) {
return true;
} else {
// Now that we've succeeded in emitting the function, reset the
// SizeEstimate back down to zero.
SizeEstimate = 0;
BufferBegin = CurBufferPtr = 0;
NumBytes += FnEnd-FnStart;
// Invalidate the icache if necessary.
sys::Memory::InvalidateInstructionCache(FnStart, FnEnd-FnStart);
TheJIT->NotifyFunctionEmitted(*F.getFunction(), FnStart, FnEnd-FnStart,
// Reset the previous debug location.
PrevDL = DebugLoc();
DEBUG(dbgs() << "JIT: Finished CodeGen of [" << (void*)FnStart
<< "] Function: " << F.getFunction()->getName()
<< ": " << (FnEnd-FnStart) << " bytes of text, "
<< Relocations.size() << " relocations\n");
// Mark code region readable and executable if it's not so already.
if (sys::hasDisassembler()) {
dbgs() << "JIT: Disassembled code:\n";
dbgs() << sys::disassembleBuffer(FnStart, FnEnd-FnStart,
} else {
dbgs() << "JIT: Binary code:\n";
uint8_t* q = FnStart;
for (int i = 0; q < FnEnd; q += 4, ++i) {
if (i == 4)
i = 0;
if (i == 0)
dbgs() << "JIT: " << (long)(q - FnStart) << ": ";
bool Done = false;
for (int j = 3; j >= 0; --j) {
if (q + j >= FnEnd)
Done = true;
dbgs() << (unsigned short)q[j];
if (Done)
dbgs() << ' ';
if (i == 3)
dbgs() << '\n';
dbgs()<< '\n';
if (JITExceptionHandling) {
uintptr_t ActualSize = 0;
SavedBufferBegin = BufferBegin;
SavedBufferEnd = BufferEnd;
SavedCurBufferPtr = CurBufferPtr;
BufferBegin = CurBufferPtr = MemMgr->startExceptionTable(F.getFunction(),
BufferEnd = BufferBegin+ActualSize;
EmittedFunctions[F.getFunction()].ExceptionTable = BufferBegin;
uint8_t *EhStart;
uint8_t *FrameRegister = DE->EmitDwarfTable(F, *this, FnStart, FnEnd,
MemMgr->endExceptionTable(F.getFunction(), BufferBegin, CurBufferPtr,
BufferBegin = SavedBufferBegin;
BufferEnd = SavedBufferEnd;
CurBufferPtr = SavedCurBufferPtr;
if (JITExceptionHandling) {
TheJIT->RegisterTable(F.getFunction(), FrameRegister);
if (MMI)
return false;
void JITEmitter::retryWithMoreMemory(MachineFunction &F) {
DEBUG(dbgs() << "JIT: Ran out of space for native code. Reattempting.\n");
Relocations.clear(); // Clear the old relocations or we'll reapply them.
// Try again with at least twice as much free space.
SizeEstimate = (uintptr_t)(2 * (BufferEnd - BufferBegin));
for (MachineFunction::iterator MBB = F.begin(), E = F.end(); MBB != E; ++MBB){
if (MBB->hasAddressTaken())
/// deallocateMemForFunction - Deallocate all memory for the specified
/// function body. Also drop any references the function has to stubs.
/// May be called while the Function is being destroyed inside ~Value().
void JITEmitter::deallocateMemForFunction(const Function *F) {
ValueMap<const Function *, EmittedCode, EmittedFunctionConfig>::iterator
Emitted = EmittedFunctions.find(F);
if (Emitted != EmittedFunctions.end()) {
if (JITExceptionHandling) {
void *JITEmitter::allocateSpace(uintptr_t Size, unsigned Alignment) {
if (BufferBegin)
return JITCodeEmitter::allocateSpace(Size, Alignment);
// create a new memory block if there is no active one.
// care must be taken so that BufferBegin is invalidated when a
// block is trimmed
BufferBegin = CurBufferPtr = MemMgr->allocateSpace(Size, Alignment);
BufferEnd = BufferBegin+Size;
return CurBufferPtr;
void *JITEmitter::allocateGlobal(uintptr_t Size, unsigned Alignment) {
// Delegate this call through the memory manager.
return MemMgr->allocateGlobal(Size, Alignment);
void JITEmitter::emitConstantPool(MachineConstantPool *MCP) {
if (TheJIT->getJITInfo().hasCustomConstantPool())
const std::vector<MachineConstantPoolEntry> &Constants = MCP->getConstants();
if (Constants.empty()) return;
unsigned Size = GetConstantPoolSizeInBytes(MCP, TheJIT->getTargetData());
unsigned Align = MCP->getConstantPoolAlignment();
ConstantPoolBase = allocateSpace(Size, Align);
ConstantPool = MCP;
if (ConstantPoolBase == 0) return; // Buffer overflow.
DEBUG(dbgs() << "JIT: Emitted constant pool at [" << ConstantPoolBase
<< "] (size: " << Size << ", alignment: " << Align << ")\n");
// Initialize the memory for all of the constant pool entries.
unsigned Offset = 0;
for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
MachineConstantPoolEntry CPE = Constants[i];
unsigned AlignMask = CPE.getAlignment() - 1;
Offset = (Offset + AlignMask) & ~AlignMask;
uintptr_t CAddr = (uintptr_t)ConstantPoolBase + Offset;
if (CPE.isMachineConstantPoolEntry()) {
// FIXME: add support to lower machine constant pool values into bytes!
report_fatal_error("Initialize memory with machine specific constant pool"
"entry has not been implemented!");
TheJIT->InitializeMemory(CPE.Val.ConstVal, (void*)CAddr);
DEBUG(dbgs() << "JIT: CP" << i << " at [0x";
dbgs().write_hex(CAddr) << "]\n");
Type *Ty = CPE.Val.ConstVal->getType();
Offset += TheJIT->getTargetData()->getTypeAllocSize(Ty);
void JITEmitter::initJumpTableInfo(MachineJumpTableInfo *MJTI) {
if (TheJIT->getJITInfo().hasCustomJumpTables())
if (MJTI->getEntryKind() == MachineJumpTableInfo::EK_Inline)
const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
if (JT.empty()) return;
unsigned NumEntries = 0;
for (unsigned i = 0, e = JT.size(); i != e; ++i)
NumEntries += JT[i].MBBs.size();
unsigned EntrySize = MJTI->getEntrySize(*TheJIT->getTargetData());
// Just allocate space for all the jump tables now. We will fix up the actual
// MBB entries in the tables after we emit the code for each block, since then
// we will know the final locations of the MBBs in memory.
JumpTable = MJTI;
JumpTableBase = allocateSpace(NumEntries * EntrySize,
void JITEmitter::emitJumpTableInfo(MachineJumpTableInfo *MJTI) {
if (TheJIT->getJITInfo().hasCustomJumpTables())
const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
if (JT.empty() || JumpTableBase == 0) return;
switch (MJTI->getEntryKind()) {
case MachineJumpTableInfo::EK_Inline:
case MachineJumpTableInfo::EK_BlockAddress: {
// EK_BlockAddress - Each entry is a plain address of block, e.g.:
// .word LBB123
assert(MJTI->getEntrySize(*TheJIT->getTargetData()) == sizeof(void*) &&
"Cross JIT'ing?");
// For each jump table, map each target in the jump table to the address of
// an emitted MachineBasicBlock.
intptr_t *SlotPtr = (intptr_t*)JumpTableBase;
for (unsigned i = 0, e = JT.size(); i != e; ++i) {
const std::vector<MachineBasicBlock*> &MBBs = JT[i].MBBs;
// Store the address of the basic block for this jump table slot in the
// memory we allocated for the jump table in 'initJumpTableInfo'
for (unsigned mi = 0, me = MBBs.size(); mi != me; ++mi)
*SlotPtr++ = getMachineBasicBlockAddress(MBBs[mi]);
case MachineJumpTableInfo::EK_Custom32:
case MachineJumpTableInfo::EK_GPRel32BlockAddress:
case MachineJumpTableInfo::EK_LabelDifference32: {
assert(MJTI->getEntrySize(*TheJIT->getTargetData()) == 4&&"Cross JIT'ing?");
// For each jump table, place the offset from the beginning of the table
// to the target address.
int *SlotPtr = (int*)JumpTableBase;
for (unsigned i = 0, e = JT.size(); i != e; ++i) {
const std::vector<MachineBasicBlock*> &MBBs = JT[i].MBBs;
// Store the offset of the basic block for this jump table slot in the
// memory we allocated for the jump table in 'initJumpTableInfo'
uintptr_t Base = (uintptr_t)SlotPtr;
for (unsigned mi = 0, me = MBBs.size(); mi != me; ++mi) {
uintptr_t MBBAddr = getMachineBasicBlockAddress(MBBs[mi]);
/// FIXME: USe EntryKind instead of magic "getPICJumpTableEntry" hook.
*SlotPtr++ = TheJIT->getJITInfo().getPICJumpTableEntry(MBBAddr, Base);
case MachineJumpTableInfo::EK_GPRel64BlockAddress:
"JT Info emission not implemented for GPRel64BlockAddress yet.");
void JITEmitter::startGVStub(const GlobalValue* GV,
unsigned StubSize, unsigned Alignment) {
SavedBufferBegin = BufferBegin;
SavedBufferEnd = BufferEnd;
SavedCurBufferPtr = CurBufferPtr;
BufferBegin = CurBufferPtr = MemMgr->allocateStub(GV, StubSize, Alignment);
BufferEnd = BufferBegin+StubSize+1;
void JITEmitter::startGVStub(void *Buffer, unsigned StubSize) {
SavedBufferBegin = BufferBegin;
SavedBufferEnd = BufferEnd;
SavedCurBufferPtr = CurBufferPtr;
BufferBegin = CurBufferPtr = (uint8_t *)Buffer;
BufferEnd = BufferBegin+StubSize+1;
void JITEmitter::finishGVStub() {
assert(CurBufferPtr != BufferEnd && "Stub overflowed allocated space.");
NumBytes += getCurrentPCOffset();
BufferBegin = SavedBufferBegin;
BufferEnd = SavedBufferEnd;
CurBufferPtr = SavedCurBufferPtr;
void *JITEmitter::allocIndirectGV(const GlobalValue *GV,
const uint8_t *Buffer, size_t Size,
unsigned Alignment) {
uint8_t *IndGV = MemMgr->allocateStub(GV, Size, Alignment);
memcpy(IndGV, Buffer, Size);
return IndGV;
// getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
// in the constant pool that was last emitted with the 'emitConstantPool'
// method.
uintptr_t JITEmitter::getConstantPoolEntryAddress(unsigned ConstantNum) const {
assert(ConstantNum < ConstantPool->getConstants().size() &&
"Invalid ConstantPoolIndex!");
return ConstPoolAddresses[ConstantNum];
// getJumpTableEntryAddress - Return the address of the JumpTable with index
// 'Index' in the jumpp table that was last initialized with 'initJumpTableInfo'
uintptr_t JITEmitter::getJumpTableEntryAddress(unsigned Index) const {
const std::vector<MachineJumpTableEntry> &JT = JumpTable->getJumpTables();
assert(Index < JT.size() && "Invalid jump table index!");
unsigned EntrySize = JumpTable->getEntrySize(*TheJIT->getTargetData());
unsigned Offset = 0;
for (unsigned i = 0; i < Index; ++i)
Offset += JT[i].MBBs.size();
Offset *= EntrySize;
return (uintptr_t)((char *)JumpTableBase + Offset);
void JITEmitter::EmittedFunctionConfig::onDelete(
JITEmitter *Emitter, const Function *F) {
void JITEmitter::EmittedFunctionConfig::onRAUW(
JITEmitter *, const Function*, const Function*) {
llvm_unreachable("The JIT doesn't know how to handle a"
" RAUW on a value it has emitted.");
// Public interface to this file
JITCodeEmitter *JIT::createEmitter(JIT &jit, JITMemoryManager *JMM,
TargetMachine &tm) {
return new JITEmitter(jit, JMM, tm);
// 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.
assert(isa<JITEmitter>(JCE) && "Unexpected MCE?");
JITEmitter *JE = cast<JITEmitter>(getCodeEmitter());
return JE->getJITResolver().getLazyFunctionStub(F);
void JIT::updateFunctionStub(Function *F) {
// Get the empty stub we generated earlier.
assert(isa<JITEmitter>(JCE) && "Unexpected MCE?");
JITEmitter *JE = cast<JITEmitter>(getCodeEmitter());
void *Stub = JE->getJITResolver().getLazyFunctionStub(F);
void *Addr = getPointerToGlobalIfAvailable(F);
assert(Addr != Stub && "Function must have non-stub address to be updated.");
// Tell the target jit info to rewrite the stub at the specified address,
// rather than creating a new one.
TargetJITInfo::StubLayout layout = getJITInfo().getStubLayout();
JE->startGVStub(Stub, layout.Size);
getJITInfo().emitFunctionStub(F, Addr, *getCodeEmitter());
/// freeMachineCodeForFunction - release machine code memory for given Function.
void JIT::freeMachineCodeForFunction(Function *F) {
// Delete translation for this from the ExecutionEngine, so it will get
// retranslated next time it is used.
updateGlobalMapping(F, 0);
// Free the actual memory for the function body and related stuff.
assert(isa<JITEmitter>(JCE) && "Unexpected MCE?");