//===-- Alpha/AlphaCodeEmitter.cpp - Convert Alpha code to machine code ---===//
//
//                     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 contains the pass that transforms the Alpha machine instructions
// into relocatable machine code.
//
//===----------------------------------------------------------------------===//

#include "AlphaTargetMachine.h"
#include "AlphaRelocations.h"
#include "Alpha.h"
#include "llvm/PassManager.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Function.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
#include <iostream>
using namespace llvm;

namespace {
  Statistic<>
  NumEmitted("alpha-emitter", "Number of machine instructions emitted");
}

namespace {
  class AlphaCodeEmitter : public MachineFunctionPass {
    const AlphaInstrInfo  *II;
    MachineCodeEmitter  &MCE;
    std::map<const MachineBasicBlock*, unsigned*> BasicBlockAddrs;
    std::vector<std::pair<const MachineBasicBlock *, unsigned*> > BBRefs;

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

  public:
    explicit AlphaCodeEmitter(MachineCodeEmitter &mce) : II(0), MCE(mce) {}
    AlphaCodeEmitter(MachineCodeEmitter &mce, const AlphaInstrInfo& ii)
        : II(&ii), MCE(mce) {}

    bool runOnMachineFunction(MachineFunction &MF);

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

    void emitInstruction(const MachineInstr &MI);

    /// emitWord - write a 32-bit word to memory at the current PC
    ///
    void emitWord(unsigned w) { MCE.emitWord(w); }

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

  private:
    void emitBasicBlock(MachineBasicBlock &MBB);

  };
}

/// createAlphaCodeEmitterPass - Return a pass that emits the collected Alpha code
/// to the specified MCE object.
FunctionPass *llvm::createAlphaCodeEmitterPass(MachineCodeEmitter &MCE) {
  return new AlphaCodeEmitter(MCE);
}

bool AlphaCodeEmitter::runOnMachineFunction(MachineFunction &MF) {
  II = ((AlphaTargetMachine&)MF.getTarget()).getInstrInfo();

  MCE.startFunction(MF);
  MCE.emitConstantPool(MF.getConstantPool());
  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
    emitBasicBlock(*I);
  MCE.finishFunction(MF);

  // Resolve all forward branches now...
  for (unsigned i = 0, e = BBRefs.size(); i != e; ++i) {
    unsigned* Location = (unsigned*)BasicBlockAddrs[BBRefs[i].first];
    unsigned* Ref = (unsigned*)BBRefs[i].second;
    intptr_t BranchTargetDisp = 
      (((unsigned char*)Location  - (unsigned char*)Ref) >> 2) - 1;
    DEBUG(std::cerr << "Fixup @ " << (void*)Ref << " to " << (void*)Location
          << " Disp " << BranchTargetDisp 
          << " using " <<  (BranchTargetDisp & ((1 << 22)-1)) << "\n");
    *Ref |= (BranchTargetDisp & ((1 << 21)-1));
  }
  BBRefs.clear();
  BasicBlockAddrs.clear();

  return false;
}

void AlphaCodeEmitter::emitBasicBlock(MachineBasicBlock &MBB) {
  uintptr_t Addr = MCE.getCurrentPCValue();
  BasicBlockAddrs[&MBB] = (unsigned*)Addr;

  for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
       I != E; ++I) {
    MachineInstr &MI = *I;
    unsigned Opcode = MI.getOpcode();
    switch(MI.getOpcode()) {
    default:
      emitWord(getBinaryCodeForInstr(*I));
      break;
    case Alpha::ALTENT:
    case Alpha::PCLABEL:
    case Alpha::MEMLABEL:
    case Alpha::IDEF_I:
    case Alpha::IDEF_F32:
    case Alpha::IDEF_F64:
      break; //skip these
    }
  }
}

static unsigned getAlphaRegNumber(unsigned Reg) {
  switch (Reg) {
  case Alpha::R0  : case Alpha::F0  : return 0;
  case Alpha::R1  : case Alpha::F1  : return 1;
  case Alpha::R2  : case Alpha::F2  : return 2;
  case Alpha::R3  : case Alpha::F3  : return 3;
  case Alpha::R4  : case Alpha::F4  : return 4;
  case Alpha::R5  : case Alpha::F5  : return 5;
  case Alpha::R6  : case Alpha::F6  : return 6;
  case Alpha::R7  : case Alpha::F7  : return 7;
  case Alpha::R8  : case Alpha::F8  : return 8;
  case Alpha::R9  : case Alpha::F9  : return 9;
  case Alpha::R10 : case Alpha::F10 : return 10;
  case Alpha::R11 : case Alpha::F11 : return 11;
  case Alpha::R12 : case Alpha::F12 : return 12;
  case Alpha::R13 : case Alpha::F13 : return 13;
  case Alpha::R14 : case Alpha::F14 : return 14;
  case Alpha::R15 : case Alpha::F15 : return 15;
  case Alpha::R16 : case Alpha::F16 : return 16;
  case Alpha::R17 : case Alpha::F17 : return 17;
  case Alpha::R18 : case Alpha::F18 : return 18;
  case Alpha::R19 : case Alpha::F19 : return 19;
  case Alpha::R20 : case Alpha::F20 : return 20;
  case Alpha::R21 : case Alpha::F21 : return 21;
  case Alpha::R22 : case Alpha::F22 : return 22;
  case Alpha::R23 : case Alpha::F23 : return 23;
  case Alpha::R24 : case Alpha::F24 : return 24;
  case Alpha::R25 : case Alpha::F25 : return 25;
  case Alpha::R26 : case Alpha::F26 : return 26;
  case Alpha::R27 : case Alpha::F27 : return 27;
  case Alpha::R28 : case Alpha::F28 : return 28;
  case Alpha::R29 : case Alpha::F29 : return 29;
  case Alpha::R30 : case Alpha::F30 : return 30;
  case Alpha::R31 : case Alpha::F31 : return 31;
  default:
    assert(0 && "Unhandled reg");
    abort();
  }
}

int AlphaCodeEmitter::getMachineOpValue(MachineInstr &MI, MachineOperand &MO) {

  int rv = 0; // Return value; defaults to 0 for unhandled cases
              // or things that get fixed up later by the JIT.

  if (MO.isRegister()) {
    rv = getAlphaRegNumber(MO.getReg());
  } else if (MO.isImmediate()) {
    rv = MO.getImmedValue();
  } else if (MO.isGlobalAddress() || MO.isExternalSymbol()
             || MO.isConstantPoolIndex()) {
    DEBUG(std::cerr << MO << " is a relocated op for " << MI << "\n";);
    bool isExternal = MO.isExternalSymbol() ||
      (MO.isGlobalAddress() &&
       ( MO.getGlobal()->hasWeakLinkage() ||
         MO.getGlobal()->isExternal()) );
    unsigned Reloc = 0;
    int Offset = 0;
    bool useGOT = false;
    switch (MI.getOpcode()) {
    case Alpha::BSR:
      Reloc = Alpha::reloc_bsr;
      break;
    case Alpha::LDLr:
    case Alpha::LDQr:
    case Alpha::LDBUr:
    case Alpha::LDWUr:
    case Alpha::LDSr:
    case Alpha::LDTr:
    case Alpha::LDAr:
    case Alpha::STQr:
    case Alpha::STLr:
    case Alpha::STWr:
    case Alpha::STBr:
    case Alpha::STSr:
    case Alpha::STTr:
      Reloc = Alpha::reloc_gprellow;
      break;
    case Alpha::LDAHr:
      Reloc = Alpha::reloc_gprelhigh;
      break;
    case Alpha::LDQl:
      Reloc = Alpha::reloc_literal;
      useGOT = true;
      break;
    case Alpha::LDAg:
    case Alpha::LDAHg:
      Reloc = Alpha::reloc_gpdist;
      Offset = MI.getOperand(3).getImmedValue();
      break;
    default:
      assert(0 && "unknown relocatable instruction");
      abort();
    }
    if (MO.isGlobalAddress())
      MCE.addRelocation(MachineRelocation((unsigned)MCE.getCurrentPCOffset(),
                                          Reloc, MO.getGlobal(), Offset,
                                          false, useGOT));
    else if (MO.isExternalSymbol())
      MCE.addRelocation(MachineRelocation((unsigned)MCE.getCurrentPCOffset(),
                                          Reloc, MO.getSymbolName(), Offset,
                                          true));
    else
      MCE.addRelocation(MachineRelocation((unsigned)MCE.getCurrentPCOffset(),
                                          Reloc, MO.getConstantPoolIndex(),
                                          Offset));
  } else if (MO.isMachineBasicBlock()) {
    unsigned* CurrPC = (unsigned*)(intptr_t)MCE.getCurrentPCValue();
    BBRefs.push_back(std::make_pair(MO.getMachineBasicBlock(), CurrPC));
  }else {
    std::cerr << "ERROR: Unknown type of MachineOperand: " << MO << "\n";
    abort();
  }

  return rv;
}


#include "AlphaGenCodeEmitter.inc"