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"
16 #ifndef _POSIX_MAPPED_FILES
17 #define _POSIX_MAPPED_FILES
20 #include "llvm/Constant.h"
21 #include "llvm/Module.h"
22 #include "llvm/CodeGen/MachineCodeEmitter.h"
23 #include "llvm/CodeGen/MachineFunction.h"
24 #include "llvm/CodeGen/MachineConstantPool.h"
25 #include "llvm/Target/TargetData.h"
26 #include "Support/Debug.h"
27 #include "Support/Statistic.h"
28 #include "Config/unistd.h"
29 #include "Config/sys/mman.h"
33 Statistic<> NumBytes("jit", "Number of bytes of machine code compiled");
36 /// JITMemoryManager - Manage memory for the JIT code generation in a logical,
37 /// sane way. This splits a large block of MAP_NORESERVE'd memory into two
38 /// sections, one for function stubs, one for the functions themselves. We
39 /// have to do this because we may need to emit a function stub while in the
40 /// middle of emitting a function, and we don't know how large the function we
41 /// are emitting is. This never bothers to release the memory, because when
42 /// we are ready to destroy the JIT, the program exits.
43 class JITMemoryManager {
44 unsigned char *MemBase; // Base of block of memory, start of stub mem
45 unsigned char *FunctionBase; // Start of the function body area
46 unsigned char *CurStubPtr, *CurFunctionPtr;
50 inline unsigned char *allocateStub(unsigned StubSize);
51 inline unsigned char *startFunctionBody();
52 inline void endFunctionBody(unsigned char *FunctionEnd);
56 // getMemory - Return a pointer to the specified number of bytes, which is
57 // mapped as executable readable and writable.
58 static void *getMemory(unsigned NumBytes) {
59 if (NumBytes == 0) return 0;
60 static const long pageSize = sysconf(_SC_PAGESIZE);
61 unsigned NumPages = (NumBytes+pageSize-1)/pageSize;
63 #if defined(i386) || defined(__i386__) || defined(__x86__)
64 /* Linux and *BSD tend to have these flags named differently. */
65 #if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
66 # define MAP_ANONYMOUS MAP_ANON
67 #endif /* defined(MAP_ANON) && !defined(MAP_ANONYMOUS) */
68 #elif defined(sparc) || defined(__sparc__) || defined(__sparcv9)
71 std::cerr << "This architecture is not supported by the JIT!\n";
75 #if defined(__linux__)
81 unsigned mmapFlags = MAP_PRIVATE|MAP_ANONYMOUS;
83 mmapFlags |= MAP_NORESERVE;
86 void *pa = mmap(0, pageSize*NumPages, PROT_READ|PROT_WRITE|PROT_EXEC,
88 if (pa == MAP_FAILED) {
95 JITMemoryManager::JITMemoryManager() {
96 // Allocate a 16M block of memory...
97 MemBase = (unsigned char*)getMemory(16 << 20);
98 FunctionBase = MemBase + 512*1024; // Use 512k for stubs
100 // Allocate stubs backwards from the function base, allocate functions forward
101 // from the function base.
102 CurStubPtr = CurFunctionPtr = FunctionBase;
105 unsigned char *JITMemoryManager::allocateStub(unsigned StubSize) {
106 CurStubPtr -= StubSize;
107 if (CurStubPtr < MemBase) {
108 std::cerr << "JIT ran out of memory for function stubs!\n";
114 unsigned char *JITMemoryManager::startFunctionBody() {
115 // Round up to an even multiple of 4 bytes, this should eventually be target
117 return (unsigned char*)(((intptr_t)CurFunctionPtr + 3) & ~3);
120 void JITMemoryManager::endFunctionBody(unsigned char *FunctionEnd) {
121 assert(FunctionEnd > CurFunctionPtr);
122 CurFunctionPtr = FunctionEnd;
128 /// Emitter - The JIT implementation of the MachineCodeEmitter, which is used
129 /// to output functions to memory for execution.
130 class Emitter : public MachineCodeEmitter {
131 JITMemoryManager MemMgr;
133 // CurBlock - The start of the current block of memory. CurByte - The
134 // current byte being emitted to.
135 unsigned char *CurBlock, *CurByte;
137 // When outputting a function stub in the context of some other function, we
138 // save CurBlock and CurByte here.
139 unsigned char *SavedCurBlock, *SavedCurByte;
141 // ConstantPoolAddresses - Contains the location for each entry in the
143 std::vector<void*> ConstantPoolAddresses;
145 Emitter(VM &vm) { TheVM = &vm; }
147 virtual void startFunction(MachineFunction &F);
148 virtual void finishFunction(MachineFunction &F);
149 virtual void emitConstantPool(MachineConstantPool *MCP);
150 virtual void startFunctionStub(const Function &F, unsigned StubSize);
151 virtual void* finishFunctionStub(const Function &F);
152 virtual void emitByte(unsigned char B);
153 virtual void emitWord(unsigned W);
155 virtual uint64_t getGlobalValueAddress(GlobalValue *V);
156 virtual uint64_t getGlobalValueAddress(const std::string &Name);
157 virtual uint64_t getConstantPoolEntryAddress(unsigned Entry);
158 virtual uint64_t getCurrentPCValue();
160 // forceCompilationOf - Force the compilation of the specified function, and
161 // return its address, because we REALLY need the address now.
163 // FIXME: This is JIT specific!
165 virtual uint64_t forceCompilationOf(Function *F);
169 MachineCodeEmitter *VM::createEmitter(VM &V) {
170 return new Emitter(V);
173 void Emitter::startFunction(MachineFunction &F) {
174 CurByte = CurBlock = MemMgr.startFunctionBody();
175 TheVM->addGlobalMapping(F.getFunction(), CurBlock);
178 void Emitter::finishFunction(MachineFunction &F) {
179 MemMgr.endFunctionBody(CurByte);
180 ConstantPoolAddresses.clear();
181 NumBytes += CurByte-CurBlock;
183 DEBUG(std::cerr << "Finished CodeGen of [" << (void*)CurBlock
184 << "] Function: " << F.getFunction()->getName()
185 << ": " << CurByte-CurBlock << " bytes of text\n");
188 void Emitter::emitConstantPool(MachineConstantPool *MCP) {
189 const std::vector<Constant*> &Constants = MCP->getConstants();
190 if (Constants.empty()) return;
192 std::vector<unsigned> ConstantOffset;
193 ConstantOffset.reserve(Constants.size());
195 // Calculate how much space we will need for all the constants, and the offset
196 // each one will live in.
197 unsigned TotalSize = 0;
198 for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
199 const Type *Ty = Constants[i]->getType();
200 unsigned Size = TheVM->getTargetData().getTypeSize(Ty);
201 unsigned Alignment = TheVM->getTargetData().getTypeAlignment(Ty);
202 // Make sure to take into account the alignment requirements of the type.
203 TotalSize = (TotalSize + Alignment-1) & ~(Alignment-1);
205 // Remember the offset this element lives at.
206 ConstantOffset.push_back(TotalSize);
207 TotalSize += Size; // Reserve space for the constant.
210 // Now that we know how much memory to allocate, do so.
211 char *Pool = new char[TotalSize];
213 // Actually output all of the constants, and remember their addresses.
214 for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
215 void *Addr = Pool + ConstantOffset[i];
216 TheVM->InitializeMemory(Constants[i], Addr);
217 ConstantPoolAddresses.push_back(Addr);
221 void Emitter::startFunctionStub(const Function &F, unsigned StubSize) {
222 SavedCurBlock = CurBlock; SavedCurByte = CurByte;
223 CurByte = CurBlock = MemMgr.allocateStub(StubSize);
226 void *Emitter::finishFunctionStub(const Function &F) {
227 NumBytes += CurByte-CurBlock;
228 DEBUG(std::cerr << "Finished CodeGen of [0x" << std::hex
229 << (unsigned)(intptr_t)CurBlock
230 << std::dec << "] Function stub for: " << F.getName()
231 << ": " << CurByte-CurBlock << " bytes of text\n");
232 std::swap(CurBlock, SavedCurBlock);
233 CurByte = SavedCurByte;
234 return SavedCurBlock;
237 void Emitter::emitByte(unsigned char B) {
238 *CurByte++ = B; // Write the byte to memory
241 void Emitter::emitWord(unsigned W) {
242 // This won't work if the endianness of the host and target don't agree! (For
243 // a JIT this can't happen though. :)
244 *(unsigned*)CurByte = W;
245 CurByte += sizeof(unsigned);
248 uint64_t Emitter::getGlobalValueAddress(GlobalValue *V) {
249 // Try looking up the function to see if it is already compiled, if not return
251 return (intptr_t)TheVM->getPointerToGlobalIfAvailable(V);
253 uint64_t Emitter::getGlobalValueAddress(const std::string &Name) {
254 return (intptr_t)TheVM->getPointerToNamedFunction(Name);
257 // getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
258 // in the constant pool that was last emitted with the 'emitConstantPool'
261 uint64_t Emitter::getConstantPoolEntryAddress(unsigned ConstantNum) {
262 assert(ConstantNum < ConstantPoolAddresses.size() &&
263 "Invalid ConstantPoolIndex!");
264 return (intptr_t)ConstantPoolAddresses[ConstantNum];
267 // getCurrentPCValue - This returns the address that the next emitted byte
268 // will be output to.
270 uint64_t Emitter::getCurrentPCValue() {
271 return (intptr_t)CurByte;
274 uint64_t Emitter::forceCompilationOf(Function *F) {
275 return (intptr_t)TheVM->getPointerToFunction(F);
278 // getPointerToNamedFunction - This function is used as a global wrapper to
279 // VM::getPointerToNamedFunction for the purpose of resolving symbols when
280 // bugpoint is debugging the JIT. In that scenario, we are loading an .so and
281 // need to resolve function(s) that are being mis-codegenerated, so we need to
282 // resolve their addresses at runtime, and this is the way to do it.
284 void *getPointerToNamedFunction(const char *Name) {
285 Module &M = TheVM->getModule();
286 if (Function *F = M.getNamedFunction(Name))
287 return TheVM->getPointerToFunction(F);
288 return TheVM->getPointerToNamedFunction(Name);