//===-- 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" #ifndef _POSIX_MAPPED_FILES #define _POSIX_MAPPED_FILES #endif #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 "Config/unistd.h" #include "Config/sys/mman.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); }; } // getMemory - Return a pointer to the specified number of bytes, which is // mapped as executable readable and writable. static void *getMemory(unsigned NumBytes) { if (NumBytes == 0) return 0; static const long pageSize = sysconf(_SC_PAGESIZE); unsigned NumPages = (NumBytes+pageSize-1)/pageSize; #if defined(i386) || defined(__i386__) || defined(__x86__) /* Linux and *BSD tend to have these flags named differently. */ #if defined(MAP_ANON) && !defined(MAP_ANONYMOUS) # define MAP_ANONYMOUS MAP_ANON #endif /* defined(MAP_ANON) && !defined(MAP_ANONYMOUS) */ #elif defined(sparc) || defined(__sparc__) || defined(__sparcv9) /* nothing */ #else std::cerr << "This architecture is not supported by the JIT!\n"; abort(); #endif int fd = -1; #if defined(__linux__) fd = 0; #endif unsigned mmapFlags = MAP_PRIVATE|MAP_ANONYMOUS; #ifdef MAP_NORESERVE mmapFlags |= MAP_NORESERVE; #endif void *pa = mmap(0, pageSize*NumPages, PROT_READ|PROT_WRITE|PROT_EXEC, mmapFlags, fd, 0); if (pa == MAP_FAILED) { perror("mmap"); abort(); } return pa; } JITMemoryManager::JITMemoryManager() { // Allocate a 16M block of memory... MemBase = (unsigned char*)getMemory(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 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 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 &Constants = MCP->getConstants(); if (Constants.empty()) return; std::vector 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); } uint64_t Emitter::getGlobalValueAddress(GlobalValue *V) { // Try looking up the function to see if it is already compiled, if not return // 0. if (isa(V)) return (intptr_t)TheJIT->getPointerToGlobalIfAvailable(V); else { return (intptr_t)TheJIT->getOrEmitGlobalVariable(cast(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); } }