MipsAsmPrinter.cpp

//===-- MipsAsmPrinter.cpp - Mips LLVM assembly writer --------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file 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 GAS-format MIPS assembly language.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "mips-asm-printer"

#include "Mips.h"
#include "MipsSubtarget.h"
#include "MipsInstrInfo.h"
#include "MipsTargetMachine.h"
#include "MipsMachineFunction.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Module.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/Target/TargetAsmInfo.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Support/Mangler.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/MathExtras.h"
#include <cctype>

using namespace llvm;

STATISTIC(EmittedInsts, "Number of machine instrs printed");

namespace {
  struct VISIBILITY_HIDDEN MipsAsmPrinter : public AsmPrinter {

    const MipsSubtarget *Subtarget;

    MipsAsmPrinter(std::ostream &O, MipsTargetMachine &TM, 
                   const TargetAsmInfo *T): 
                   AsmPrinter(O, TM, T) {
      Subtarget = &TM.getSubtarget<MipsSubtarget>();
    }

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

    virtual std::string getSectionForFunction(const Function &F) const;
    bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo, 
                         unsigned AsmVariant, const char *ExtraCode);
    void printOperand(const MachineInstr *MI, int opNum);
    void printUnsignedImm(const MachineInstr *MI, int opNum);
    void printMemOperand(const MachineInstr *MI, int opNum, 
                         const char *Modifier = 0);
    void printFCCOperand(const MachineInstr *MI, int opNum, 
                         const char *Modifier = 0);
    void printModuleLevelGV(const GlobalVariable* GVar);
    void printSavedRegsBitmask(MachineFunction &MF);
    void printHex32(unsigned int Value);

    const char *emitCurrentABIString(void);
    void emitFunctionStart(MachineFunction &MF);
    void emitFunctionEnd(MachineFunction &MF);
    void emitFrameDirective(MachineFunction &MF);

    bool printInstruction(const MachineInstr *MI);  // autogenerated.
    bool runOnMachineFunction(MachineFunction &F);
    bool doInitialization(Module &M);
    bool doFinalization(Module &M);
  };
} // end of anonymous namespace

#include "MipsGenAsmWriter.inc"

/// createMipsCodePrinterPass - Returns a pass that prints the MIPS
/// 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::createMipsCodePrinterPass(std::ostream &o,
                                              MipsTargetMachine &tm) 
{
  return new MipsAsmPrinter(o, tm, tm.getTargetAsmInfo());
}

//===----------------------------------------------------------------------===//
//
//  Mips Asm Directives
//
//  -- Frame directive "frame Stackpointer, Stacksize, RARegister"
//  Describe the stack frame.
//
//  -- Mask directives "(f)mask  bitmask, offset" 
//  Tells the assembler which registers are saved and where.
//  bitmask - contain a little endian bitset indicating which registers are 
//            saved on function prologue (e.g. with a 0x80000000 mask, the 
//            assembler knows the register 31 (RA) is saved at prologue.
//  offset  - the position before stack pointer subtraction indicating where 
//            the first saved register on prologue is located. (e.g. with a
//
//  Consider the following function prologue:
//
//    .frame  $fp,48,$ra
//    .mask   0xc0000000,-8
//       addiu $sp, $sp, -48
//       sw $ra, 40($sp)
//       sw $fp, 36($sp)
//
//    With a 0xc0000000 mask, the assembler knows the register 31 (RA) and 
//    30 (FP) are saved at prologue. As the save order on prologue is from 
//    left to right, RA is saved first. A -8 offset means that after the 
//    stack pointer subtration, the first register in the mask (RA) will be
//    saved at address 48-8=40.
//
//===----------------------------------------------------------------------===//

//===----------------------------------------------------------------------===//
// Mask directives
//===----------------------------------------------------------------------===//

// Create a bitmask with all callee saved registers for CPU or Floating Point 
// registers. For CPU registers consider RA, GP and FP for saving if necessary.
void MipsAsmPrinter::
printSavedRegsBitmask(MachineFunction &MF)
{
  const TargetRegisterInfo &RI = *TM.getRegisterInfo();
  MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();
             
  // CPU and FPU Saved Registers Bitmasks
  unsigned int CPUBitmask = 0;
  unsigned int FPUBitmask = 0;

  // Set the CPU and FPU Bitmasks
  MachineFrameInfo *MFI = MF.getFrameInfo();
  const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
  for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
    unsigned RegNum = MipsRegisterInfo::getRegisterNumbering(CSI[i].getReg());
    if (CSI[i].getRegClass() == Mips::CPURegsRegisterClass)
      CPUBitmask |= (1 << RegNum);
    else
      FPUBitmask |= (1 << RegNum);
  }

  // Return Address and Frame registers must also be set in CPUBitmask.
  if (RI.hasFP(MF)) 
    CPUBitmask |= (1 << MipsRegisterInfo::
                getRegisterNumbering(RI.getFrameRegister(MF)));
  
  if (MF.getFrameInfo()->hasCalls()) 
    CPUBitmask |= (1 << MipsRegisterInfo::
                getRegisterNumbering(RI.getRARegister()));

  // Print CPUBitmask
  O << "\t.mask \t"; printHex32(CPUBitmask); O << ','
    << MipsFI->getCPUTopSavedRegOff() << '\n';

  // Print FPUBitmask
  O << "\t.fmask\t"; printHex32(FPUBitmask); O << ","
    << MipsFI->getFPUTopSavedRegOff() << '\n';
}

// Print a 32 bit hex number with all numbers.
void MipsAsmPrinter::
printHex32(unsigned int Value) 
{
  O << "0x" << std::hex;
  for (int i = 7; i >= 0; i--) 
    O << std::hex << ( (Value & (0xF << (i*4))) >> (i*4) );
  O << std::dec;
}

//===----------------------------------------------------------------------===//
// Frame and Set directives
//===----------------------------------------------------------------------===//

/// Frame Directive
void MipsAsmPrinter::
emitFrameDirective(MachineFunction &MF)
{
  const TargetRegisterInfo &RI = *TM.getRegisterInfo();

  unsigned stackReg  = RI.getFrameRegister(MF);
  unsigned returnReg = RI.getRARegister();
  unsigned stackSize = MF.getFrameInfo()->getStackSize();


  O << "\t.frame\t" << '$' << LowercaseString(RI.get(stackReg).AsmName)
                    << ',' << stackSize << ','
                    << '$' << LowercaseString(RI.get(returnReg).AsmName)
                    << '\n';
}

/// Emit Set directives.
const char * MipsAsmPrinter::
emitCurrentABIString(void) 
{  
  switch(Subtarget->getTargetABI()) {
    case MipsSubtarget::O32:  return "abi32";  
    case MipsSubtarget::O64:  return "abiO64";
    case MipsSubtarget::N32:  return "abiN32";
    case MipsSubtarget::N64:  return "abi64";
    case MipsSubtarget::EABI: return "eabi32"; // TODO: handle eabi64
    default: break;
  }

  assert(0 && "Unknown Mips ABI");
  return NULL;
}  

// Substitute old hook with new one temporary
std::string MipsAsmPrinter::getSectionForFunction(const Function &F) const {
  return TAI->SectionForGlobal(&F);
}

/// Emit the directives used by GAS on the start of functions
void MipsAsmPrinter::
emitFunctionStart(MachineFunction &MF)
{
  // Print out the label for the function.
  const Function *F = MF.getFunction();
  SwitchToTextSection(TAI->SectionForGlobal(F).c_str());

  // 2 bits aligned
  EmitAlignment(2, F);

  O << "\t.globl\t"  << CurrentFnName << '\n';
  O << "\t.ent\t"    << CurrentFnName << '\n';

  printVisibility(CurrentFnName, F->getVisibility());

  if ((TAI->hasDotTypeDotSizeDirective()) && Subtarget->isLinux())
    O << "\t.type\t"   << CurrentFnName << ", @function\n";

  O << CurrentFnName << ":\n";

  emitFrameDirective(MF);
  printSavedRegsBitmask(MF);

  O << '\n';
}

/// Emit the directives used by GAS on the end of functions
void MipsAsmPrinter::
emitFunctionEnd(MachineFunction &MF) 
{
  // There are instruction for this macros, but they must
  // always be at the function end, and we can't emit and
  // break with BB logic. 
  O << "\t.set\tmacro\n"; 
  O << "\t.set\treorder\n"; 

  O << "\t.end\t" << CurrentFnName << '\n';
  if (TAI->hasDotTypeDotSizeDirective() && !Subtarget->isLinux())
    O << "\t.size\t" << CurrentFnName << ", .-" << CurrentFnName << '\n';
}

/// runOnMachineFunction - This uses the printMachineInstruction()
/// method to print assembly for each instruction.
bool MipsAsmPrinter::
runOnMachineFunction(MachineFunction &MF) 
{
  SetupMachineFunction(MF);

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

  // Print out jump tables referenced by the function
  EmitJumpTableInfo(MF.getJumpTableInfo(), MF);

  O << "\n\n";

  // What's my mangled name?
  CurrentFnName = Mang->getValueName(MF.getFunction());

  // Emit the function start directives
  emitFunctionStart(MF);

  // 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.
    if (I != MF.begin()) {
      printBasicBlockLabel(I, true, true);
      O << '\n';
    }

    for (MachineBasicBlock::const_iterator II = I->begin(), E = I->end();
         II != E; ++II) {
      // Print the assembly for the instruction.
      printInstruction(II);
      ++EmittedInsts;
    }

    // Each Basic Block is separated by a newline
    O << '\n';
  }

  // Emit function end directives
  emitFunctionEnd(MF);

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

// Print out an operand for an inline asm expression.
bool MipsAsmPrinter::
PrintAsmOperand(const MachineInstr *MI, unsigned OpNo, 
                unsigned AsmVariant, const char *ExtraCode) 
{
  // Does this asm operand have a single letter operand modifier?
  if (ExtraCode && ExtraCode[0]) 
    return true; // Unknown modifier.

  printOperand(MI, OpNo);
  return false;
}

void MipsAsmPrinter::
printOperand(const MachineInstr *MI, int opNum) 
{
  const MachineOperand &MO = MI->getOperand(opNum);
  const TargetRegisterInfo  &RI = *TM.getRegisterInfo();
  bool closeP = false;
  bool isPIC = (TM.getRelocationModel() == Reloc::PIC_);
  bool isCodeLarge = (TM.getCodeModel() == CodeModel::Large);

  // %hi and %lo used on mips gas to load global addresses on
  // static code. %got is used to load global addresses when 
  // using PIC_. %call16 is used to load direct call targets
  // on PIC_ and small code size. %call_lo and %call_hi load 
  // direct call targets on PIC_ and large code size.
  if (MI->getOpcode() == Mips::LUi && !MO.isRegister() 
      && !MO.isImmediate()) {
    if ((isPIC) && (isCodeLarge))
      O << "%call_hi(";
    else
      O << "%hi(";
    closeP = true;
  } else if ((MI->getOpcode() == Mips::ADDiu) && !MO.isRegister() 
             && !MO.isImmediate()) {
    const MachineOperand &firstMO = MI->getOperand(opNum-1);
    if (firstMO.getReg() == Mips::GP)
      O << "%gp_rel(";
    else
      O << "%lo(";
    closeP = true;
  } else if ((isPIC) && (MI->getOpcode() == Mips::LW)
             && (!MO.isRegister()) && (!MO.isImmediate())) {
    const MachineOperand &firstMO = MI->getOperand(opNum-1);
    const MachineOperand &lastMO  = MI->getOperand(opNum+1);
    if ((firstMO.isRegister()) && (lastMO.isRegister())) {
      if ((firstMO.getReg() == Mips::T9) && (lastMO.getReg() == Mips::GP) 
          && (!isCodeLarge))
        O << "%call16(";
      else if ((firstMO.getReg() != Mips::T9) && (lastMO.getReg() == Mips::GP))
        O << "%got(";
      else if ((firstMO.getReg() == Mips::T9) && (lastMO.getReg() != Mips::GP) 
               && (isCodeLarge))
        O << "%call_lo(";
      closeP = true;
    }
  }
 
  switch (MO.getType()) 
  {
    case MachineOperand::MO_Register:
      if (TargetRegisterInfo::isPhysicalRegister(MO.getReg()))
        O << '$' << LowercaseString (RI.get(MO.getReg()).AsmName);
      else
        O << '$' << MO.getReg();
      break;

    case MachineOperand::MO_Immediate:
      O << (short int)MO.getImm();
      break;

    case MachineOperand::MO_MachineBasicBlock:
      printBasicBlockLabel(MO.getMBB());
      return;

    case MachineOperand::MO_GlobalAddress:
      O << Mang->getValueName(MO.getGlobal());
      break;

    case MachineOperand::MO_ExternalSymbol:
      O << MO.getSymbolName();
      break;

    case MachineOperand::MO_JumpTableIndex:
      O << TAI->getPrivateGlobalPrefix() << "JTI" << getFunctionNumber()
      << '_' << MO.getIndex();
      break;

    case MachineOperand::MO_ConstantPoolIndex:
      O << TAI->getPrivateGlobalPrefix() << "CPI"
        << getFunctionNumber() << "_" << MO.getIndex();
      break;
  
    default:
      O << "<unknown operand type>"; abort (); break;
  }

  if (closeP) O << ")";
}

void MipsAsmPrinter::
printUnsignedImm(const MachineInstr *MI, int opNum) 
{
  const MachineOperand &MO = MI->getOperand(opNum);
  if (MO.getType() == MachineOperand::MO_Immediate)
    O << (unsigned short int)MO.getImm();
  else 
    printOperand(MI, opNum);
}

void MipsAsmPrinter::
printMemOperand(const MachineInstr *MI, int opNum, const char *Modifier) 
{
  // when using stack locations for not load/store instructions
  // print the same way as all normal 3 operand instructions.
  if (Modifier && !strcmp(Modifier, "stackloc")) {
    printOperand(MI, opNum+1);
    O << ", ";
    printOperand(MI, opNum);
    return;
  }

  // Load/Store memory operands -- imm($reg) 
  // If PIC target the target is loaded as the 
  // pattern lw $25,%call16($28)
  printOperand(MI, opNum);
  O << "(";
  printOperand(MI, opNum+1);
  O << ")";
}

void MipsAsmPrinter::
printFCCOperand(const MachineInstr *MI, int opNum, const char *Modifier) 
{
  const MachineOperand& MO = MI->getOperand(opNum);
  O << Mips::MipsFCCToString((Mips::CondCode)MO.getImm()); 
}

bool MipsAsmPrinter::
doInitialization(Module &M) 
{
  Mang = new Mangler(M);

  // Tell the assembler which ABI we are using
  O << "\t.section .mdebug." << emitCurrentABIString() << '\n';

  // TODO: handle O64 ABI
  if (Subtarget->isABI_EABI())
    O << "\t.section .gcc_compiled_long" << 
      (Subtarget->isGP32bit() ? "32" : "64") << '\n';

  // return to previous section
  O << "\t.previous" << '\n'; 

  return false; // success
}

void MipsAsmPrinter::
printModuleLevelGV(const GlobalVariable* GVar) {
  const TargetData *TD = TM.getTargetData();

  if (!GVar->hasInitializer())
    return;   // External global require no code

  // Check to see if this is a special global used by LLVM, if so, emit it.
  if (EmitSpecialLLVMGlobal(GVar))
    return;

  O << "\n\n";
  std::string SectionName = TAI->SectionForGlobal(GVar);
  std::string name = Mang->getValueName(GVar);
  Constant *C = GVar->getInitializer();
  const Type *CTy = C->getType();
  unsigned Size = TD->getABITypeSize(CTy);
  const ConstantArray *CVA = dyn_cast<ConstantArray>(C);
  bool printSizeAndType = true;

  // A data structure or array is aligned in memory to the largest
  // alignment boundary required by any data type inside it (this matches
  // the Preferred Type Alignment). For integral types, the alignment is
  // the type size.
  unsigned Align;
  if (CTy->getTypeID() == Type::IntegerTyID ||
      CTy->getTypeID() == Type::VoidTyID) {
    assert(!(Size & (Size-1)) && "Alignment is not a power of two!");
    Align = Log2_32(Size);
  } else
    Align = TD->getPreferredTypeAlignmentShift(CTy);

  printVisibility(name, GVar->getVisibility());

  SwitchToDataSection(SectionName.c_str());

  if (C->isNullValue() && !GVar->hasSection()) {
    if (!GVar->isThreadLocal() &&
        (GVar->hasInternalLinkage() || GVar->isWeakForLinker())) {
      if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.

      if (GVar->hasInternalLinkage())
        O << "\t.local\t" << name << '\n';

      O << TAI->getCOMMDirective() << name << ',' << Size;
      if (TAI->getCOMMDirectiveTakesAlignment())
        O << ',' << (1 << Align);

      O << '\n';
      return;
    }
  }
  switch (GVar->getLinkage()) {
   case GlobalValue::LinkOnceLinkage:
   case GlobalValue::CommonLinkage:
   case GlobalValue::WeakLinkage:
    // FIXME: Verify correct for weak.
    // Nonnull linkonce -> weak
    O << "\t.weak " << name << '\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 << TAI->getGlobalDirective() << name << '\n';
    // Fall Through
   case GlobalValue::InternalLinkage:
    if (CVA && CVA->isCString())
      printSizeAndType = false;
    break;
   case GlobalValue::GhostLinkage:
    cerr << "Should not have any unmaterialized functions!\n";
    abort();
   case GlobalValue::DLLImportLinkage:
    cerr << "DLLImport linkage is not supported by this target!\n";
    abort();
   case GlobalValue::DLLExportLinkage:
    cerr << "DLLExport linkage is not supported by this target!\n";
    abort();
   default:
    assert(0 && "Unknown linkage type!");
  }

  EmitAlignment(Align, GVar);

  if (TAI->hasDotTypeDotSizeDirective() && printSizeAndType) {
    O << "\t.type " << name << ",@object\n";
    O << "\t.size " << name << ',' << Size << '\n';
  }

  O << name << ":\n";
  EmitGlobalConstant(C);
}

bool MipsAsmPrinter::
doFinalization(Module &M)
{
  // Print out module-level global variables here.
  for (Module::const_global_iterator I = M.global_begin(),
         E = M.global_end(); I != E; ++I)
    printModuleLevelGV(I);

  O << '\n';

  return AsmPrinter::doFinalization(M);
}