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//===-- Emitter.cpp - Write machine code to executable memory -------------===//
//
// This file defines a MachineCodeEmitter object that is used by Jello to write
// machine code to memory and remember where relocatable values lie.
//
//===----------------------------------------------------------------------===//
#include "VM.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Function.h"
#include "Support/Statistic.h"
namespace {
Statistic<> NumBytes("jello", "Number of bytes of machine code compiled");
class Emitter : public MachineCodeEmitter {
VM &TheVM;
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;
std::vector<std::pair<BasicBlock*, unsigned *> > BBRefs;
std::map<BasicBlock*, unsigned> BBLocations;
std::vector<void*> ConstantPoolAddresses;
public:
Emitter(VM &vm) : TheVM(vm) {}
virtual void startFunction(MachineFunction &F);
virtual void finishFunction(MachineFunction &F);
virtual void emitConstantPool(MachineConstantPool *MCP);
virtual void startBasicBlock(MachineBasicBlock &BB);
virtual void startFunctionStub(const Function &F, unsigned StubSize);
virtual void* finishFunctionStub(const Function &F);
virtual void emitByte(unsigned char B);
virtual void emitPCRelativeDisp(Value *V);
virtual void emitGlobalAddress(GlobalValue *V, bool isPCRelative);
virtual void emitGlobalAddress(const std::string &Name, bool isPCRelative);
virtual void emitFunctionConstantValueAddress(unsigned ConstantNum,
int Offset);
private:
void emitAddress(void *Addr, bool isPCRelative);
};
}
MachineCodeEmitter *VM::createEmitter(VM &V) {
return new Emitter(V);
}
#define _POSIX_MAPPED_FILES
#include <unistd.h>
#include <sys/mman.h>
// FIXME: This should be rewritten to support a real memory manager for
// executable memory pages!
static void *getMemory(unsigned NumPages) {
return mmap(0, 4096*NumPages, PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
}
void Emitter::startFunction(MachineFunction &F) {
CurBlock = (unsigned char *)getMemory(8);
CurByte = CurBlock; // Start writing at the beginning of the fn.
TheVM.addGlobalMapping(F.getFunction(), CurBlock);
}
void Emitter::finishFunction(MachineFunction &F) {
ConstantPoolAddresses.clear();
for (unsigned i = 0, e = BBRefs.size(); i != e; ++i) {
unsigned Location = BBLocations[BBRefs[i].first];
unsigned *Ref = BBRefs[i].second;
*Ref = Location-(unsigned)(intptr_t)Ref-4;
}
BBRefs.clear();
BBLocations.clear();
NumBytes += CurByte-CurBlock;
DEBUG(std::cerr << "Finished CodeGen of [0x" << std::hex
<< (unsigned)(intptr_t)CurBlock
<< std::dec << "] Function: " << F.getFunction()->getName()
<< ": " << CurByte-CurBlock << " bytes of text\n");
}
void Emitter::emitConstantPool(MachineConstantPool *MCP) {
const std::vector<Constant*> &Constants = MCP->getConstants();
for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
// For now we just allocate some memory on the heap, this can be
// dramatically improved.
const Type *Ty = ((Value*)Constants[i])->getType();
void *Addr = malloc(TheVM.getTargetData().getTypeSize(Ty));
TheVM.InitializeMemory(Constants[i], Addr);
ConstantPoolAddresses.push_back(Addr);
}
}
void Emitter::startBasicBlock(MachineBasicBlock &BB) {
BBLocations[BB.getBasicBlock()] = (unsigned)(intptr_t)CurByte;
}
void Emitter::startFunctionStub(const Function &F, unsigned StubSize) {
SavedCurBlock = CurBlock; SavedCurByte = CurByte;
// FIXME: this is a huge waste of memory.
CurBlock = (unsigned char *)getMemory((StubSize+4095)/4096);
CurByte = CurBlock; // Start writing at the beginning of the fn.
}
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
}
// emitPCRelativeDisp - For functions, just output a displacement that will
// cause a reference to the zero page, which will cause a seg-fault, causing
// things to get resolved on demand. Keep track of these markers.
//
// For basic block references, keep track of where the references are so they
// may be patched up when the basic block is defined.
//
void Emitter::emitPCRelativeDisp(Value *V) {
BasicBlock *BB = cast<BasicBlock>(V); // Keep track of reference...
BBRefs.push_back(std::make_pair(BB, (unsigned*)CurByte));
CurByte += 4;
}
// emitAddress - Emit an address in either direct or PCRelative form...
//
void Emitter::emitAddress(void *Addr, bool isPCRelative) {
if (isPCRelative) {
*(intptr_t*)CurByte = (intptr_t)Addr - (intptr_t)CurByte-4;
} else {
*(void**)CurByte = Addr;
}
CurByte += 4;
}
void Emitter::emitGlobalAddress(GlobalValue *V, bool isPCRelative) {
if (isPCRelative) { // must be a call, this is a major hack!
// Try looking up the function to see if it is already compiled!
if (void *Addr = TheVM.getPointerToGlobalIfAvailable(V)) {
emitAddress(Addr, isPCRelative);
} else { // Function has not yet been code generated!
TheVM.addFunctionRef(CurByte, cast<Function>(V));
// Delayed resolution...
emitAddress((void*)VM::CompilationCallback, isPCRelative);
}
} else {
emitAddress(TheVM.getPointerToGlobal(V), isPCRelative);
}
}
void Emitter::emitGlobalAddress(const std::string &Name, bool isPCRelative) {
emitAddress(TheVM.getPointerToNamedFunction(Name), isPCRelative);
}
void Emitter::emitFunctionConstantValueAddress(unsigned ConstantNum,
int Offset) {
assert(ConstantNum < ConstantPoolAddresses.size() &&
"Invalid ConstantPoolIndex!");
*(void**)CurByte = (char*)ConstantPoolAddresses[ConstantNum]+Offset;
CurByte += 4;
}
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