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 "Support/Debug.h"
24 #include "Support/Statistic.h"
25 #include "Support/SystemUtils.h"
29 Statistic<> NumBytes("jit", "Number of bytes of machine code compiled");
32 /// JITMemoryManager - Manage memory for the JIT code generation in a logical,
33 /// sane way. This splits a large block of MAP_NORESERVE'd memory into two
34 /// sections, one for function stubs, one for the functions themselves. We
35 /// have to do this because we may need to emit a function stub while in the
36 /// middle of emitting a function, and we don't know how large the function we
37 /// are emitting is. This never bothers to release the memory, because when
38 /// we are ready to destroy the JIT, the program exits.
39 class JITMemoryManager {
40 unsigned char *MemBase; // Base of block of memory, start of stub mem
41 unsigned char *FunctionBase; // Start of the function body area
42 unsigned char *CurStubPtr, *CurFunctionPtr;
46 inline unsigned char *allocateStub(unsigned StubSize);
47 inline unsigned char *startFunctionBody();
48 inline void endFunctionBody(unsigned char *FunctionEnd);
52 JITMemoryManager::JITMemoryManager() {
53 // Allocate a 16M block of memory...
54 MemBase = (unsigned char*)AllocateRWXMemory(16 << 20);
55 FunctionBase = MemBase + 512*1024; // Use 512k for stubs
57 // Allocate stubs backwards from the function base, allocate functions forward
58 // from the function base.
59 CurStubPtr = CurFunctionPtr = FunctionBase;
62 unsigned char *JITMemoryManager::allocateStub(unsigned StubSize) {
63 CurStubPtr -= StubSize;
64 if (CurStubPtr < MemBase) {
65 std::cerr << "JIT ran out of memory for function stubs!\n";
71 unsigned char *JITMemoryManager::startFunctionBody() {
72 // Round up to an even multiple of 4 bytes, this should eventually be target
74 return (unsigned char*)(((intptr_t)CurFunctionPtr + 3) & ~3);
77 void JITMemoryManager::endFunctionBody(unsigned char *FunctionEnd) {
78 assert(FunctionEnd > CurFunctionPtr);
79 CurFunctionPtr = FunctionEnd;
85 /// Emitter - The JIT implementation of the MachineCodeEmitter, which is used
86 /// to output functions to memory for execution.
87 class Emitter : public MachineCodeEmitter {
88 JITMemoryManager MemMgr;
90 // CurBlock - The start of the current block of memory. CurByte - The
91 // current byte being emitted to.
92 unsigned char *CurBlock, *CurByte;
94 // When outputting a function stub in the context of some other function, we
95 // save CurBlock and CurByte here.
96 unsigned char *SavedCurBlock, *SavedCurByte;
98 // ConstantPoolAddresses - Contains the location for each entry in the
100 std::vector<void*> ConstantPoolAddresses;
102 Emitter(JIT &jit) { TheJIT = &jit; }
104 virtual void startFunction(MachineFunction &F);
105 virtual void finishFunction(MachineFunction &F);
106 virtual void emitConstantPool(MachineConstantPool *MCP);
107 virtual void startFunctionStub(const Function &F, unsigned StubSize);
108 virtual void* finishFunctionStub(const Function &F);
109 virtual void emitByte(unsigned char B);
110 virtual void emitWord(unsigned W);
111 virtual void emitWordAt(unsigned W, unsigned *Ptr);
113 virtual uint64_t getGlobalValueAddress(GlobalValue *V);
114 virtual uint64_t getGlobalValueAddress(const std::string &Name);
115 virtual uint64_t getConstantPoolEntryAddress(unsigned Entry);
116 virtual uint64_t getCurrentPCValue();
118 // forceCompilationOf - Force the compilation of the specified function, and
119 // return its address, because we REALLY need the address now.
121 // FIXME: This is JIT specific!
123 virtual uint64_t forceCompilationOf(Function *F);
127 MachineCodeEmitter *JIT::createEmitter(JIT &jit) {
128 return new Emitter(jit);
131 void Emitter::startFunction(MachineFunction &F) {
132 CurByte = CurBlock = MemMgr.startFunctionBody();
133 TheJIT->addGlobalMapping(F.getFunction(), CurBlock);
136 void Emitter::finishFunction(MachineFunction &F) {
137 MemMgr.endFunctionBody(CurByte);
138 ConstantPoolAddresses.clear();
139 NumBytes += CurByte-CurBlock;
141 DEBUG(std::cerr << "Finished CodeGen of [" << (void*)CurBlock
142 << "] Function: " << F.getFunction()->getName()
143 << ": " << CurByte-CurBlock << " bytes of text\n");
146 void Emitter::emitConstantPool(MachineConstantPool *MCP) {
147 const std::vector<Constant*> &Constants = MCP->getConstants();
148 if (Constants.empty()) return;
150 std::vector<unsigned> ConstantOffset;
151 ConstantOffset.reserve(Constants.size());
153 // Calculate how much space we will need for all the constants, and the offset
154 // each one will live in.
155 unsigned TotalSize = 0;
156 for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
157 const Type *Ty = Constants[i]->getType();
158 unsigned Size = TheJIT->getTargetData().getTypeSize(Ty);
159 unsigned Alignment = TheJIT->getTargetData().getTypeAlignment(Ty);
160 // Make sure to take into account the alignment requirements of the type.
161 TotalSize = (TotalSize + Alignment-1) & ~(Alignment-1);
163 // Remember the offset this element lives at.
164 ConstantOffset.push_back(TotalSize);
165 TotalSize += Size; // Reserve space for the constant.
168 // Now that we know how much memory to allocate, do so.
169 char *Pool = new char[TotalSize];
171 // Actually output all of the constants, and remember their addresses.
172 for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
173 void *Addr = Pool + ConstantOffset[i];
174 TheJIT->InitializeMemory(Constants[i], Addr);
175 ConstantPoolAddresses.push_back(Addr);
179 void Emitter::startFunctionStub(const Function &F, unsigned StubSize) {
180 SavedCurBlock = CurBlock; SavedCurByte = CurByte;
181 CurByte = CurBlock = MemMgr.allocateStub(StubSize);
184 void *Emitter::finishFunctionStub(const Function &F) {
185 NumBytes += CurByte-CurBlock;
186 DEBUG(std::cerr << "Finished CodeGen of [0x" << std::hex
187 << (unsigned)(intptr_t)CurBlock
188 << std::dec << "] Function stub for: " << F.getName()
189 << ": " << CurByte-CurBlock << " bytes of text\n");
190 std::swap(CurBlock, SavedCurBlock);
191 CurByte = SavedCurByte;
192 return SavedCurBlock;
195 void Emitter::emitByte(unsigned char B) {
196 *CurByte++ = B; // Write the byte to memory
199 void Emitter::emitWord(unsigned W) {
200 // This won't work if the endianness of the host and target don't agree! (For
201 // a JIT this can't happen though. :)
202 *(unsigned*)CurByte = W;
203 CurByte += sizeof(unsigned);
206 void Emitter::emitWordAt(unsigned W, unsigned *Ptr) {
210 uint64_t Emitter::getGlobalValueAddress(GlobalValue *V) {
211 // Try looking up the function to see if it is already compiled, if not return
213 if (isa<Function>(V))
214 return (intptr_t)TheJIT->getPointerToGlobalIfAvailable(V);
216 return (intptr_t)TheJIT->getOrEmitGlobalVariable(cast<GlobalVariable>(V));
219 uint64_t Emitter::getGlobalValueAddress(const std::string &Name) {
220 return (intptr_t)TheJIT->getPointerToNamedFunction(Name);
223 // getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
224 // in the constant pool that was last emitted with the 'emitConstantPool'
227 uint64_t Emitter::getConstantPoolEntryAddress(unsigned ConstantNum) {
228 assert(ConstantNum < ConstantPoolAddresses.size() &&
229 "Invalid ConstantPoolIndex!");
230 return (intptr_t)ConstantPoolAddresses[ConstantNum];
233 // getCurrentPCValue - This returns the address that the next emitted byte
234 // will be output to.
236 uint64_t Emitter::getCurrentPCValue() {
237 return (intptr_t)CurByte;
240 uint64_t Emitter::forceCompilationOf(Function *F) {
241 return (intptr_t)TheJIT->getPointerToFunction(F);
244 // getPointerToNamedFunction - This function is used as a global wrapper to
245 // JIT::getPointerToNamedFunction for the purpose of resolving symbols when
246 // bugpoint is debugging the JIT. In that scenario, we are loading an .so and
247 // need to resolve function(s) that are being mis-codegenerated, so we need to
248 // resolve their addresses at runtime, and this is the way to do it.
250 void *getPointerToNamedFunction(const char *Name) {
251 Module &M = TheJIT->getModule();
252 if (Function *F = M.getNamedFunction(Name))
253 return TheJIT->getPointerToFunction(F);
254 return TheJIT->getPointerToNamedFunction(Name);