lib/Target/X86/X86AsmPrinter.cpp

//===-- X86AsmPrinter.cpp - Convert X86 LLVM code to Intel assembly -------===//
// 
//                     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 a printer that converts from our internal representation
// of machine-dependent LLVM code to Intel-format assembly language. This
// printer is the output mechanism used by `llc' and `lli -print-machineinstrs'
// on X86.
//
//===----------------------------------------------------------------------===//

#include "X86.h"
#include "X86InstrInfo.h"
#include "X86TargetMachine.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Module.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/ValueTypes.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/Mangler.h"
#include "Support/Statistic.h"
#include "Support/StringExtras.h"
#include "Support/CommandLine.h"
using namespace llvm;

namespace {
  Statistic<> EmittedInsts("asm-printer", "Number of machine instrs printed");

  struct GasBugWorkaroundEmitter : public MachineCodeEmitter {
    GasBugWorkaroundEmitter(std::ostream& o) 
      : O(o), OldFlags(O.flags()), firstByte(true) {
      O << std::hex;
    }

    ~GasBugWorkaroundEmitter() {
      O.flags(OldFlags);
    }

    virtual void emitByte(unsigned char B) {
      if (!firstByte) O << "\n\t";
      firstByte = false;
      O << ".byte 0x" << (unsigned) B;
    }

    // These should never be called
    virtual void emitWord(unsigned W) { assert(0); }
    virtual uint64_t getGlobalValueAddress(GlobalValue *V) { abort(); }
    virtual uint64_t getGlobalValueAddress(const std::string &Name) { abort(); }
    virtual uint64_t getConstantPoolEntryAddress(unsigned Index) { abort(); }
    virtual uint64_t getCurrentPCValue() { abort(); }
    virtual uint64_t forceCompilationOf(Function *F) { abort(); }

  private:
    std::ostream& O;
    std::ios::fmtflags OldFlags;
    bool firstByte;
  };

  struct X86AsmPrinter : public AsmPrinter {
    X86AsmPrinter(std::ostream &O, TargetMachine &TM) : AsmPrinter(O, TM) { }

    virtual const char *getPassName() const {
      return "X86 Assembly Printer";
    }

    /// printInstruction - This method is automatically generated by tablegen
    /// from the instruction set description.  This method returns true if the
    /// machine instruction was sufficiently described to print it, otherwise it
    /// returns false.
    bool printInstruction(const MachineInstr *MI);

    // This method is used by the tablegen'erated instruction printer.
    void printOperand(const MachineInstr *MI, unsigned OpNo, MVT::ValueType VT){
      const MachineOperand &MO = MI->getOperand(OpNo);
      if (MO.getType() == MachineOperand::MO_MachineRegister) {
        assert(MRegisterInfo::isPhysicalRegister(MO.getReg())&&"Not physref??");
        // Bug Workaround: See note in Printer::doInitialization about %.
        O << "%" << TM.getRegisterInfo()->get(MO.getReg()).Name;
      } else {
        printOp(MO);
      }
    }

    void printCallOperand(const MachineInstr *MI, unsigned OpNo,
                          MVT::ValueType VT) {
      printOp(MI->getOperand(OpNo), true); // Don't print "OFFSET".
    }

    void printMemoryOperand(const MachineInstr *MI, unsigned OpNo,
                            MVT::ValueType VT) {
      switch (VT) {
      default: assert(0 && "Unknown arg size!");
      case MVT::i8:   O << "BYTE PTR "; break;
      case MVT::i16:  O << "WORD PTR "; break;
      case MVT::i32:
      case MVT::f32:  O << "DWORD PTR "; break;
      case MVT::i64:
      case MVT::f64:  O << "QWORD PTR "; break;
      case MVT::f80:  O << "XWORD PTR "; break;
      }
      printMemReference(MI, OpNo);
    }

    void printMachineInstruction(const MachineInstr *MI);
    void printOp(const MachineOperand &MO, bool elideOffsetKeyword = false);
    void printMemReference(const MachineInstr *MI, unsigned Op);
    void printConstantPool(MachineConstantPool *MCP);
    bool runOnMachineFunction(MachineFunction &F);    
    bool doInitialization(Module &M);
    bool doFinalization(Module &M);
  };
} // end of anonymous namespace

/// createX86CodePrinterPass - Returns a pass that prints the X86
/// assembly code for a MachineFunction to the given output stream,
/// using the given target machine description.  This should work
/// regardless of whether the function is in SSA form.
///
FunctionPass *llvm::createX86CodePrinterPass(std::ostream &o,TargetMachine &tm){
  return new X86AsmPrinter(o, tm);
}


// Include the auto-generated portion of the assembly writer.
#include "X86GenAsmWriter.inc"


/// printConstantPool - Print to the current output stream assembly
/// representations of the constants in the constant pool MCP. This is
/// used to print out constants which have been "spilled to memory" by
/// the code generator.
///
void X86AsmPrinter::printConstantPool(MachineConstantPool *MCP) {
  const std::vector<Constant*> &CP = MCP->getConstants();
  const TargetData &TD = TM.getTargetData();
 
  if (CP.empty()) return;

  for (unsigned i = 0, e = CP.size(); i != e; ++i) {
    O << "\t.section .rodata\n";
    emitAlignment(TD.getTypeAlignmentShift(CP[i]->getType()));
    O << ".CPI" << CurrentFnName << "_" << i << ":\t\t\t\t\t" << CommentChar
      << *CP[i] << "\n";
    emitGlobalConstant(CP[i]);
  }
}

/// runOnMachineFunction - This uses the printMachineInstruction()
/// method to print assembly for each instruction.
///
bool X86AsmPrinter::runOnMachineFunction(MachineFunction &MF) {
  setupMachineFunction(MF);
  O << "\n\n";

  // Print out constants referenced by the function
  printConstantPool(MF.getConstantPool());

  // Print out labels for the function.
  O << "\t.text\n";
  emitAlignment(4);
  O << "\t.globl\t" << CurrentFnName << "\n";
  O << "\t.type\t" << CurrentFnName << ", @function\n";
  O << CurrentFnName << ":\n";

  // Print out code for the function.
  for (MachineFunction::const_iterator I = MF.begin(), E = MF.end();
       I != E; ++I) {
    // Print a label for the basic block.
    O << ".LBB" << CurrentFnName << "_" << I->getNumber() << ":\t"
      << CommentChar << " " << I->getBasicBlock()->getName() << "\n";
    for (MachineBasicBlock::const_iterator II = I->begin(), E = I->end();
         II != E; ++II) {
      // Print the assembly for the instruction.
      O << "\t";
      printMachineInstruction(II);
    }
  }

  // We didn't modify anything.
  return false;
}

static bool isScale(const MachineOperand &MO) {
  return MO.isImmediate() &&
    (MO.getImmedValue() == 1 || MO.getImmedValue() == 2 ||
     MO.getImmedValue() == 4 || MO.getImmedValue() == 8);
}

static bool isMem(const MachineInstr *MI, unsigned Op) {
  if (MI->getOperand(Op).isFrameIndex()) return true;
  if (MI->getOperand(Op).isConstantPoolIndex()) return true;
  return Op+4 <= MI->getNumOperands() &&
    MI->getOperand(Op  ).isRegister() && isScale(MI->getOperand(Op+1)) &&
    MI->getOperand(Op+2).isRegister() && MI->getOperand(Op+3).isImmediate();
}



void X86AsmPrinter::printOp(const MachineOperand &MO,
                            bool elideOffsetKeyword /* = false */) {
  const MRegisterInfo &RI = *TM.getRegisterInfo();
  switch (MO.getType()) {
  case MachineOperand::MO_VirtualRegister:
    if (Value *V = MO.getVRegValueOrNull()) {
      O << "<" << V->getName() << ">";
      return;
    }
    // FALLTHROUGH
  case MachineOperand::MO_MachineRegister:
    if (MRegisterInfo::isPhysicalRegister(MO.getReg()))
      // Bug Workaround: See note in Printer::doInitialization about %.
      O << "%" << RI.get(MO.getReg()).Name;
    else
      O << "%reg" << MO.getReg();
    return;

  case MachineOperand::MO_SignExtendedImmed:
  case MachineOperand::MO_UnextendedImmed:
    O << (int)MO.getImmedValue();
    return;
  case MachineOperand::MO_MachineBasicBlock: {
    MachineBasicBlock *MBBOp = MO.getMachineBasicBlock();
    O << ".LBB" << Mang->getValueName(MBBOp->getParent()->getFunction())
      << "_" << MBBOp->getNumber () << "\t# "
      << MBBOp->getBasicBlock ()->getName ();
    return;
  }
  case MachineOperand::MO_PCRelativeDisp:
    std::cerr << "Shouldn't use addPCDisp() when building X86 MachineInstrs";
    abort ();
    return;
  case MachineOperand::MO_GlobalAddress:
    if (!elideOffsetKeyword)
      O << "OFFSET ";
    O << Mang->getValueName(MO.getGlobal());
    return;
  case MachineOperand::MO_ExternalSymbol:
    O << MO.getSymbolName();
    return;
  default:
    O << "<unknown operand type>"; return;    
  }
}

void X86AsmPrinter::printMemReference(const MachineInstr *MI, unsigned Op) {
  assert(isMem(MI, Op) && "Invalid memory reference!");

  if (MI->getOperand(Op).isFrameIndex()) {
    O << "[frame slot #" << MI->getOperand(Op).getFrameIndex();
    if (MI->getOperand(Op+3).getImmedValue())
      O << " + " << MI->getOperand(Op+3).getImmedValue();
    O << "]";
    return;
  } else if (MI->getOperand(Op).isConstantPoolIndex()) {
    O << "[.CPI" << CurrentFnName << "_"
      << MI->getOperand(Op).getConstantPoolIndex();
    if (MI->getOperand(Op+3).getImmedValue())
      O << " + " << MI->getOperand(Op+3).getImmedValue();
    O << "]";
    return;
  }

  const MachineOperand &BaseReg  = MI->getOperand(Op);
  int ScaleVal                   = MI->getOperand(Op+1).getImmedValue();
  const MachineOperand &IndexReg = MI->getOperand(Op+2);
  int DispVal                    = MI->getOperand(Op+3).getImmedValue();

  O << "[";
  bool NeedPlus = false;
  if (BaseReg.getReg()) {
    printOp(BaseReg);
    NeedPlus = true;
  }

  if (IndexReg.getReg()) {
    if (NeedPlus) O << " + ";
    if (ScaleVal != 1)
      O << ScaleVal << "*";
    printOp(IndexReg);
    NeedPlus = true;
  }

  if (DispVal) {
    if (NeedPlus)
      if (DispVal > 0)
        O << " + ";
      else {
        O << " - ";
        DispVal = -DispVal;
      }
    O << DispVal;
  }
  O << "]";
}


/// printMachineInstruction -- Print out a single X86 LLVM instruction
/// MI in Intel syntax to the current output stream.
///
void X86AsmPrinter::printMachineInstruction(const MachineInstr *MI) {
  ++EmittedInsts;

  // gas bugs:
  //
  // The 80-bit FP store-pop instruction "fstp XWORD PTR [...]"  is misassembled
  // by gas in intel_syntax mode as its 32-bit equivalent "fstp DWORD PTR
  // [...]". Workaround: Output the raw opcode bytes instead of the instruction.
  //
  // The 80-bit FP load instruction "fld XWORD PTR [...]" is misassembled by gas
  // in intel_syntax mode as its 32-bit equivalent "fld DWORD PTR
  // [...]". Workaround: Output the raw opcode bytes instead of the instruction.
  //
  // gas intel_syntax mode treats "fild QWORD PTR [...]" as an invalid opcode,
  // saying "64 bit operations are only supported in 64 bit modes." libopcodes
  // disassembles it as "fild DWORD PTR [...]", which is wrong. Workaround:
  // Output the raw opcode bytes instead of the instruction.
  //
  // gas intel_syntax mode treats "fistp QWORD PTR [...]" as an invalid opcode,
  // saying "64 bit operations are only supported in 64 bit modes." libopcodes
  // disassembles it as "fistpll DWORD PTR [...]", which is wrong. Workaround:
  // Output the raw opcode bytes instead of the instruction.
  switch (MI->getOpcode()) {
  case X86::FSTP80m:
  case X86::FLD80m:
  case X86::FILD64m:
  case X86::FISTP64m:
    GasBugWorkaroundEmitter gwe(O);
    X86::emitInstruction(gwe, (X86InstrInfo&)*TM.getInstrInfo(), *MI);
    O << "\t# ";
  }

  // Call the autogenerated instruction printer routines.
  bool Handled = printInstruction(MI);
  if (!Handled) {
    MI->dump();
    assert(0 && "Do not know how to print this instruction!");
    abort();
  }
}

bool X86AsmPrinter::doInitialization(Module &M) {
  AsmPrinter::doInitialization(M);
  // Tell gas we are outputting Intel syntax (not AT&T syntax) assembly.
  //
  // Bug: gas in `intel_syntax noprefix' mode interprets the symbol `Sp' in an
  // instruction as a reference to the register named sp, and if you try to
  // reference a symbol `Sp' (e.g. `mov ECX, OFFSET Sp') then it gets lowercased
  // before being looked up in the symbol table. This creates spurious
  // `undefined symbol' errors when linking. Workaround: Do not use `noprefix'
  // mode, and decorate all register names with percent signs.
  O << "\t.intel_syntax\n";
  return false;
}

// SwitchSection - Switch to the specified section of the executable if we are
// not already in it!
//
static void SwitchSection(std::ostream &OS, std::string &CurSection,
                          const char *NewSection) {
  if (CurSection != NewSection) {
    CurSection = NewSection;
    if (!CurSection.empty())
      OS << "\t" << NewSection << "\n";
  }
}

bool X86AsmPrinter::doFinalization(Module &M) {
  const TargetData &TD = TM.getTargetData();
  std::string CurSection;

  // Print out module-level global variables here.
  for (Module::const_giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
    if (I->hasInitializer()) {   // External global require no code
      O << "\n\n";
      std::string name = Mang->getValueName(I);
      Constant *C = I->getInitializer();
      unsigned Size = TD.getTypeSize(C->getType());
      unsigned Align = TD.getTypeAlignmentShift(C->getType());

      if (C->isNullValue() && 
          (I->hasLinkOnceLinkage() || I->hasInternalLinkage() ||
           I->hasWeakLinkage() /* FIXME: Verify correct */)) {
        SwitchSection(O, CurSection, ".data");
        if (I->hasInternalLinkage())
          O << "\t.local " << name << "\n";
        
        O << "\t.comm " << name << "," << TD.getTypeSize(C->getType())
          << "," << (1 << Align);
        O << "\t\t# ";
        WriteAsOperand(O, I, true, true, &M);
        O << "\n";
      } else {
        switch (I->getLinkage()) {
        case GlobalValue::LinkOnceLinkage:
        case GlobalValue::WeakLinkage:   // FIXME: Verify correct for weak.
          // Nonnull linkonce -> weak
          O << "\t.weak " << name << "\n";
          SwitchSection(O, CurSection, "");
          O << "\t.section\t.llvm.linkonce.d." << name << ",\"aw\",@progbits\n";
          break;
        case GlobalValue::AppendingLinkage:
          // FIXME: appending linkage variables should go into a section of
          // their name or something.  For now, just emit them as external.
        case GlobalValue::ExternalLinkage:
          // If external or appending, declare as a global symbol
          O << "\t.globl " << name << "\n";
          // FALL THROUGH
        case GlobalValue::InternalLinkage:
          if (C->isNullValue())
            SwitchSection(O, CurSection, ".bss");
          else
            SwitchSection(O, CurSection, ".data");
          break;
        }

        emitAlignment(Align);
        O << "\t.type " << name << ",@object\n";
        O << "\t.size " << name << "," << Size << "\n";
        O << name << ":\t\t\t\t# ";
        WriteAsOperand(O, I, true, true, &M);
        O << " = ";
        WriteAsOperand(O, C, false, false, &M);
        O << "\n";
        emitGlobalConstant(C);
      }
    }

  AsmPrinter::doFinalization(M);
  return false; // success
}