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

445 lines
16 KiB
C++
Raw Normal View History

//===-- 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/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"
using namespace llvm;
namespace {
Statistic<> NumBytes("jit", "Number of bytes of machine code compiled");
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 {
sys::MemoryBlock MemBlock; // Virtual memory block allocated RWX
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();
~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...
MemBlock = sys::Memory::AllocateRWX((16 << 20));
MemBase = reinterpret_cast<unsigned char*>(MemBlock.base());
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;
}
JITMemoryManager::~JITMemoryManager() {
sys::Memory::ReleaseRWX(MemBlock);
}
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 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;
}
//===----------------------------------------------------------------------===//
// JIT lazy compilation code.
//
namespace {
/// 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;
// 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:
JITResolver(MachineCodeEmitter &mce) : MCE(mce) {
LazyResolverFn =
TheJIT->getJITInfo().getLazyResolverFunction(JITCompilerFn);
}
/// getFunctionStub - This returns a pointer to a function stub, creating
/// one on demand as needed.
void *getFunctionStub(Function *F);
/// 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) {
/// Get the target-specific JIT resolver function.
StubToFunctionMap[Location] = F;
return (void*)LazyResolverFn;
}
/// 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) {
// If we already have a stub for this function, recycle it.
void *&Stub = FunctionToStubMap[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->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 (F->hasExternalLinkage()) {
// 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!
StubToFunctionMap[Stub] = F;
return Stub;
}
/// 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();
// 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.StubToFunctionMap.upper_bound(Stub);
assert(I != JR.StubToFunctionMap.begin() && "This is not a known stub!");
Function *F = (--I)->second;
// The target function will rewrite the stub so that the compilation callback
// function is no longer called from this stub.
JR.StubToFunctionMap.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.FunctionToStubMap.erase(F);
// FIXME: We could rewrite all references to this stub if we knew them.
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;
// ConstantPoolAddresses - Contains the location for each entry in the
// constant pool.
std::vector<void*> ConstantPoolAddresses;
/// Relocations - These are the relocations that the function needs, as
/// emitted.
std::vector<MachineRelocation> Relocations;
public:
JITEmitter(JIT &jit) { TheJIT = &jit; }
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);
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);
ConstantPoolAddresses.clear();
NumBytes += CurByte-CurBlock;
if (!Relocations.empty()) {
// 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());
else
ResultPtr = getPointerToGlobal(MR.getGlobalValue(),
CurBlock+MR.getMachineCodeOffset(),
MR.doesntNeedFunctionStub());
MR.setResultPointer(ResultPtr);
}
TheJIT->getJITInfo().relocate(CurBlock, &Relocations[0],
Relocations.size());
}
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<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 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 < 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 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);
}
}