lib/Target/PowerPC/PPCCodeEmitter.cpp

//===-- PPC32CodeEmitter.cpp - JIT Code Emitter for PowerPC32 -----*- C++ -*-=//
// 
//                     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 the PowerPC 32-bit CodeEmitter and associated machinery to
// JIT-compile bytecode to native PowerPC.
//
//===----------------------------------------------------------------------===//

#include "PPC32JITInfo.h"
#include "PPC32TargetMachine.h"
#include "llvm/Module.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Support/Debug.h"

namespace llvm {

namespace {
  class JITResolver {
    MachineCodeEmitter &MCE;

    // LazyCodeGenMap - Keep track of call sites for functions that are to be
    // lazily resolved.
    std::map<unsigned, Function*> LazyCodeGenMap;

    // LazyResolverMap - Keep track of the lazy resolver created for a
    // particular function so that we can reuse them if necessary.
    std::map<Function*, unsigned> LazyResolverMap;

  public:
    JITResolver(MachineCodeEmitter &mce) : MCE(mce) {}
    unsigned getLazyResolver(Function *F);
    unsigned addFunctionReference(unsigned Address, Function *F);
    
  private:
    unsigned emitStubForFunction(Function *F);
    static void CompilationCallback();
    unsigned resolveFunctionReference(unsigned RetAddr);
  };

  static JITResolver &getResolver(MachineCodeEmitter &MCE) {
    static JITResolver *TheJITResolver = 0;
    if (TheJITResolver == 0)
      TheJITResolver = new JITResolver(MCE);
    return *TheJITResolver;
  }
}

unsigned JITResolver::getLazyResolver(Function *F) {
  std::map<Function*, unsigned>::iterator I = LazyResolverMap.lower_bound(F);
  if (I != LazyResolverMap.end() && I->first == F) return I->second;

  unsigned Stub = emitStubForFunction(F);
  LazyResolverMap.insert(I, std::make_pair(F, Stub));
  return Stub;
}

/// addFunctionReference - This method is called when we need to emit the
/// address of a function that has not yet been emitted, so we don't know the
/// address.  Instead, we emit a call to the CompilationCallback method, and
/// keep track of where we are.
///
unsigned JITResolver::addFunctionReference(unsigned Address, Function *F) {
  LazyCodeGenMap[Address] = F;
  return (intptr_t)&JITResolver::CompilationCallback;
}

unsigned JITResolver::resolveFunctionReference(unsigned RetAddr) {
  std::map<unsigned, Function*>::iterator I = LazyCodeGenMap.find(RetAddr);
  assert(I != LazyCodeGenMap.end() && "Not in map!");
  Function *F = I->second;
  LazyCodeGenMap.erase(I);
  return MCE.forceCompilationOf(F);
}

/// emitStubForFunction - This method is used by the JIT when it needs to emit
/// the address of a function for a function whose code has not yet been
/// generated.  In order to do this, it generates a stub which jumps to the lazy
/// function compiler, which will eventually get fixed to call the function
/// directly.
///
unsigned JITResolver::emitStubForFunction(Function *F) {
  std::cerr << "PPC32CodeEmitter::emitStubForFunction() unimplemented!\n";
  abort();
  return 0;
}

void JITResolver::CompilationCallback() {
  std::cerr << "PPC32CodeEmitter: CompilationCallback() unimplemented!";
  abort();
}

namespace {
  class PPC32CodeEmitter : public MachineFunctionPass {
    TargetMachine &TM;
    MachineCodeEmitter &MCE;

    // Tracks which instruction references which BasicBlock
    std::vector<std::pair<const BasicBlock*,
                          std::pair<unsigned*,MachineInstr*> > > BBRefs;
    // Tracks where each BasicBlock starts
    std::map<const BasicBlock*, long> BBLocations;

    /// getMachineOpValue - evaluates the MachineOperand of a given MachineInstr
    ///
    int64_t getMachineOpValue(MachineInstr &MI, MachineOperand &MO);

    unsigned getAddressOfExternalFunction(Function *F);

  public:
    PPC32CodeEmitter(TargetMachine &T, MachineCodeEmitter &M) 
      : TM(T), MCE(M) {}

    const char *getPassName() const { return "PowerPC Machine Code Emitter"; }

    /// runOnMachineFunction - emits the given MachineFunction to memory
    ///
    bool runOnMachineFunction(MachineFunction &MF);

    /// emitBasicBlock - emits the given MachineBasicBlock to memory
    ///
    void emitBasicBlock(MachineBasicBlock &MBB);

    /// emitWord - write a 32-bit word to memory at the current PC
    ///
    void emitWord(unsigned w) { MCE.emitWord(w); }
    
    /// getValueBit - return the particular bit of Val
    ///
    unsigned getValueBit(int64_t Val, unsigned bit) { return (Val >> bit) & 1; }

    /// getBinaryCodeForInstr - This function, generated by the
    /// CodeEmitterGenerator using TableGen, produces the binary encoding for
    /// machine instructions.
    ///
    unsigned getBinaryCodeForInstr(MachineInstr &MI);
  };
}

/// addPassesToEmitMachineCode - Add passes to the specified pass manager to get
/// machine code emitted.  This uses a MachineCodeEmitter object to handle
/// actually outputting the machine code and resolving things like the address
/// of functions.  This method should returns true if machine code emission is
/// not supported.
///
bool PPC32TargetMachine::addPassesToEmitMachineCode(FunctionPassManager &PM,
                                                    MachineCodeEmitter &MCE) {
  // Keep as `true' until this is a functional JIT to allow llvm-gcc to build
  return true;

  // Machine code emitter pass for PowerPC
  PM.add(new PPC32CodeEmitter(*this, MCE)); 
  // Delete machine code for this function after emitting it
  PM.add(createMachineCodeDeleter());
  return false;
}

bool PPC32CodeEmitter::runOnMachineFunction(MachineFunction &MF) {
  MCE.startFunction(MF);
  MCE.emitConstantPool(MF.getConstantPool());
  for (MachineFunction::iterator BB = MF.begin(), E = MF.end(); BB != E; ++BB)
    emitBasicBlock(*BB);
  MCE.finishFunction(MF);

  // Resolve branches to BasicBlocks for the entire function
  for (unsigned i = 0, e = BBRefs.size(); i != e; ++i) {
    long Location = BBLocations[BBRefs[i].first];
    unsigned *Ref = BBRefs[i].second.first;
    MachineInstr *MI = BBRefs[i].second.second;
    DEBUG(std::cerr << "Fixup @ " << std::hex << Ref << " to 0x" << Location
                    << " in instr: " << std::dec << *MI);
    for (unsigned ii = 0, ee = MI->getNumOperands(); ii != ee; ++ii) {
      MachineOperand &op = MI->getOperand(ii);
      if (op.isPCRelativeDisp()) {
        // the instruction's branch target is made such that it branches to
        // PC + (branchTarget * 4), so undo that arithmetic here:
        // Location is the target of the branch
        // Ref is the location of the instruction, and hence the PC
        int64_t branchTarget = (Location - (long)Ref) >> 2;
        MI->SetMachineOperandConst(ii, MachineOperand::MO_SignExtendedImmed,
                                   branchTarget);
        unsigned fixedInstr = PPC32CodeEmitter::getBinaryCodeForInstr(*MI);
        MCE.emitWordAt(fixedInstr, Ref);
        break;
      }
    }
  }
  BBRefs.clear();
  BBLocations.clear();

  return false;
}

void PPC32CodeEmitter::emitBasicBlock(MachineBasicBlock &MBB) {
  for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end(); I != E; ++I)
    emitWord(getBinaryCodeForInstr(*I));
}

unsigned PPC32CodeEmitter::getAddressOfExternalFunction(Function *F) {
  static std::map<Function*, unsigned> ExternalFn2Addr;
  std::map<Function*, unsigned>::iterator Addr = ExternalFn2Addr.find(F);

  if (Addr == ExternalFn2Addr.end())
    ExternalFn2Addr[F] = MCE.forceCompilationOf(F);
  return ExternalFn2Addr[F];
}

int64_t PPC32CodeEmitter::getMachineOpValue(MachineInstr &MI, 
                                            MachineOperand &MO) {
  int64_t rv = 0; // Return value; defaults to 0 for unhandled cases
                  // or things that get fixed up later by the JIT.
  if (MO.isRegister()) {
    rv = MO.getReg();
  } else if (MO.isImmediate()) {
    rv = MO.getImmedValue();
  } else if (MO.isGlobalAddress()) {
    GlobalValue *GV = MO.getGlobal();
    intptr_t Addr = (intptr_t)MCE.getGlobalValueAddress(GV);
    if (Addr == 0) {
      if (Function *F = dyn_cast<Function>(GV)) {
        if (F->isExternal())
          rv = getAddressOfExternalFunction(F);
        else {
          // Function has not yet been code generated!
          getResolver(MCE).addFunctionReference(MCE.getCurrentPCValue(), F);
          // Delayed resolution...
          return (intptr_t)getResolver(MCE).getLazyResolver(F);
        }
      } else if (GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) {
        if (GVar->isExternal())
          rv = MCE.getGlobalValueAddress(MO.getSymbolName());
        else {
          std::cerr << "PPC32CodeEmitter: External global addr not found: " 
                    << *GVar;
          abort();
        }
      }
    }
    if (MO.isPCRelative()) { // Global variable reference
      rv = (Addr - MCE.getCurrentPCValue()) >> 2;
    }
  } else if (MO.isMachineBasicBlock()) {
    const BasicBlock *BB = MO.getMachineBasicBlock()->getBasicBlock();
    unsigned* CurrPC = (unsigned*)(intptr_t)MCE.getCurrentPCValue();
    BBRefs.push_back(std::make_pair(BB, std::make_pair(CurrPC, &MI)));
  } else if (MO.isConstantPoolIndex()) {
    unsigned index = MO.getConstantPoolIndex();
    rv = MCE.getConstantPoolEntryAddress(index);
  } else if (MO.isFrameIndex()) {
    std::cerr << "PPC32CodeEmitter: error: Frame index unhandled!\n";
    abort();
  } else {
    std::cerr << "ERROR: Unknown type of MachineOperand: " << MO << "\n";
    abort();
  }

  return rv;
}


void *PPC32JITInfo::getJITStubForFunction(Function *F, MachineCodeEmitter &MCE){
  return (void*)((unsigned long)getResolver(MCE).getLazyResolver(F));
}

void PPC32JITInfo::replaceMachineCodeForFunction (void *Old, void *New) {
  std::cerr << "PPC32JITInfo::replaceMachineCodeForFunction not implemented\n";
  abort();
}

#include "PPC32GenCodeEmitter.inc"

} // end llvm namespace