1 //===-- Emitter.cpp - Write machine code to executable memory -------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines a MachineCodeEmitter object that is used by Jello to write
11 // machine code to memory and remember where relocatable values lie.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "jit"
17 #include "llvm/Constant.h"
18 #include "llvm/Module.h"
19 #include "llvm/CodeGen/MachineCodeEmitter.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/CodeGen/MachineConstantPool.h"
22 #include "llvm/Target/TargetData.h"
23 #include "llvm/Support/Debug.h"
24 #include "llvm/ADT/Statistic.h"
25 #include "llvm/System/Memory.h"
30 Statistic<> NumBytes("jit", "Number of bytes of machine code compiled");
33 /// JITMemoryManager - Manage memory for the JIT code generation in a logical,
34 /// sane way. This splits a large block of MAP_NORESERVE'd memory into two
35 /// sections, one for function stubs, one for the functions themselves. We
36 /// have to do this because we may need to emit a function stub while in the
37 /// middle of emitting a function, and we don't know how large the function we
38 /// are emitting is. This never bothers to release the memory, because when
39 /// we are ready to destroy the JIT, the program exits.
40 class JITMemoryManager {
41 sys::MemoryBlock MemBlock; // Virtual memory block allocated RWX
42 unsigned char *MemBase; // Base of block of memory, start of stub mem
43 unsigned char *FunctionBase; // Start of the function body area
44 unsigned char *CurStubPtr, *CurFunctionPtr;
48 inline unsigned char *allocateStub(unsigned StubSize);
49 inline unsigned char *startFunctionBody();
50 inline void endFunctionBody(unsigned char *FunctionEnd);
54 JITMemoryManager::JITMemoryManager() {
55 // Allocate a 16M block of memory...
56 MemBlock = sys::Memory::AllocateRWX((16 << 20));
57 MemBase = reinterpret_cast<unsigned char*>(MemBlock.base());
58 FunctionBase = MemBase + 512*1024; // Use 512k for stubs
60 // Allocate stubs backwards from the function base, allocate functions forward
61 // from the function base.
62 CurStubPtr = CurFunctionPtr = FunctionBase;
65 unsigned char *JITMemoryManager::allocateStub(unsigned StubSize) {
66 CurStubPtr -= StubSize;
67 if (CurStubPtr < MemBase) {
68 std::cerr << "JIT ran out of memory for function stubs!\n";
74 unsigned char *JITMemoryManager::startFunctionBody() {
75 // Round up to an even multiple of 4 bytes, this should eventually be target
77 return (unsigned char*)(((intptr_t)CurFunctionPtr + 3) & ~3);
80 void JITMemoryManager::endFunctionBody(unsigned char *FunctionEnd) {
81 assert(FunctionEnd > CurFunctionPtr);
82 CurFunctionPtr = FunctionEnd;
88 /// Emitter - The JIT implementation of the MachineCodeEmitter, which is used
89 /// to output functions to memory for execution.
90 class Emitter : public MachineCodeEmitter {
91 JITMemoryManager MemMgr;
93 // CurBlock - The start of the current block of memory. CurByte - The
94 // current byte being emitted to.
95 unsigned char *CurBlock, *CurByte;
97 // When outputting a function stub in the context of some other function, we
98 // save CurBlock and CurByte here.
99 unsigned char *SavedCurBlock, *SavedCurByte;
101 // ConstantPoolAddresses - Contains the location for each entry in the
103 std::vector<void*> ConstantPoolAddresses;
105 Emitter(JIT &jit) { TheJIT = &jit; }
107 virtual void startFunction(MachineFunction &F);
108 virtual void finishFunction(MachineFunction &F);
109 virtual void emitConstantPool(MachineConstantPool *MCP);
110 virtual void startFunctionStub(const Function &F, unsigned StubSize);
111 virtual void* finishFunctionStub(const Function &F);
112 virtual void emitByte(unsigned char B);
113 virtual void emitWord(unsigned W);
114 virtual void emitWordAt(unsigned W, unsigned *Ptr);
116 virtual uint64_t getGlobalValueAddress(GlobalValue *V);
117 virtual uint64_t getGlobalValueAddress(const std::string &Name);
118 virtual uint64_t getConstantPoolEntryAddress(unsigned Entry);
119 virtual uint64_t getCurrentPCValue();
121 // forceCompilationOf - Force the compilation of the specified function, and
122 // return its address, because we REALLY need the address now.
124 // FIXME: This is JIT specific!
126 virtual uint64_t forceCompilationOf(Function *F);
130 MachineCodeEmitter *JIT::createEmitter(JIT &jit) {
131 return new Emitter(jit);
134 void Emitter::startFunction(MachineFunction &F) {
135 CurByte = CurBlock = MemMgr.startFunctionBody();
136 TheJIT->addGlobalMapping(F.getFunction(), CurBlock);
139 void Emitter::finishFunction(MachineFunction &F) {
140 MemMgr.endFunctionBody(CurByte);
141 ConstantPoolAddresses.clear();
142 NumBytes += CurByte-CurBlock;
144 DEBUG(std::cerr << "Finished CodeGen of [" << (void*)CurBlock
145 << "] Function: " << F.getFunction()->getName()
146 << ": " << CurByte-CurBlock << " bytes of text\n");
149 void Emitter::emitConstantPool(MachineConstantPool *MCP) {
150 const std::vector<Constant*> &Constants = MCP->getConstants();
151 if (Constants.empty()) return;
153 std::vector<unsigned> ConstantOffset;
154 ConstantOffset.reserve(Constants.size());
156 // Calculate how much space we will need for all the constants, and the offset
157 // each one will live in.
158 unsigned TotalSize = 0;
159 for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
160 const Type *Ty = Constants[i]->getType();
161 unsigned Size = TheJIT->getTargetData().getTypeSize(Ty);
162 unsigned Alignment = TheJIT->getTargetData().getTypeAlignment(Ty);
163 // Make sure to take into account the alignment requirements of the type.
164 TotalSize = (TotalSize + Alignment-1) & ~(Alignment-1);
166 // Remember the offset this element lives at.
167 ConstantOffset.push_back(TotalSize);
168 TotalSize += Size; // Reserve space for the constant.
171 // Now that we know how much memory to allocate, do so.
172 char *Pool = new char[TotalSize];
174 // Actually output all of the constants, and remember their addresses.
175 for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
176 void *Addr = Pool + ConstantOffset[i];
177 TheJIT->InitializeMemory(Constants[i], Addr);
178 ConstantPoolAddresses.push_back(Addr);
182 void Emitter::startFunctionStub(const Function &F, unsigned StubSize) {
183 SavedCurBlock = CurBlock; SavedCurByte = CurByte;
184 CurByte = CurBlock = MemMgr.allocateStub(StubSize);
187 void *Emitter::finishFunctionStub(const Function &F) {
188 NumBytes += CurByte-CurBlock;
189 DEBUG(std::cerr << "Finished CodeGen of [0x" << std::hex
190 << (uintptr_t)CurBlock
191 << std::dec << "] Function stub for: " << F.getName()
192 << ": " << CurByte-CurBlock << " bytes of text\n");
193 std::swap(CurBlock, SavedCurBlock);
194 CurByte = SavedCurByte;
195 return SavedCurBlock;
198 void Emitter::emitByte(unsigned char B) {
199 *CurByte++ = B; // Write the byte to memory
202 void Emitter::emitWord(unsigned W) {
203 // This won't work if the endianness of the host and target don't agree! (For
204 // a JIT this can't happen though. :)
205 *(unsigned*)CurByte = W;
206 CurByte += sizeof(unsigned);
209 void Emitter::emitWordAt(unsigned W, unsigned *Ptr) {
213 uint64_t Emitter::getGlobalValueAddress(GlobalValue *V) {
214 // Try looking up the function to see if it is already compiled, if not return
216 if (Function *F = dyn_cast<Function>(V)) {
217 void *Addr = TheJIT->getPointerToGlobalIfAvailable(F);
218 if (Addr == 0 && F->hasExternalLinkage()) {
219 // Do not output stubs for external functions.
220 Addr = TheJIT->getPointerToFunction(F);
222 return (intptr_t)Addr;
224 return (intptr_t)TheJIT->getOrEmitGlobalVariable(cast<GlobalVariable>(V));
227 uint64_t Emitter::getGlobalValueAddress(const std::string &Name) {
228 return (intptr_t)TheJIT->getPointerToNamedFunction(Name);
231 // getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
232 // in the constant pool that was last emitted with the 'emitConstantPool'
235 uint64_t Emitter::getConstantPoolEntryAddress(unsigned ConstantNum) {
236 assert(ConstantNum < ConstantPoolAddresses.size() &&
237 "Invalid ConstantPoolIndex!");
238 return (intptr_t)ConstantPoolAddresses[ConstantNum];
241 // getCurrentPCValue - This returns the address that the next emitted byte
242 // will be output to.
244 uint64_t Emitter::getCurrentPCValue() {
245 return (intptr_t)CurByte;
248 uint64_t Emitter::forceCompilationOf(Function *F) {
249 return (intptr_t)TheJIT->getPointerToFunction(F);
252 // getPointerToNamedFunction - This function is used as a global wrapper to
253 // JIT::getPointerToNamedFunction for the purpose of resolving symbols when
254 // bugpoint is debugging the JIT. In that scenario, we are loading an .so and
255 // need to resolve function(s) that are being mis-codegenerated, so we need to
256 // resolve their addresses at runtime, and this is the way to do it.
258 void *getPointerToNamedFunction(const char *Name) {
259 Module &M = TheJIT->getModule();
260 if (Function *F = M.getNamedFunction(Name))
261 return TheJIT->getPointerToFunction(F);
262 return TheJIT->getPointerToNamedFunction(Name);