C++ MipsTargetMachine::isPositionIndependent方法代码示例

static void createFPFnStub(Function *F, Module *M, FPParamVariant PV,
                           const MipsTargetMachine &TM) {
  bool PicMode = TM.isPositionIndependent();
  bool LE = TM.isLittleEndian();
  LLVMContext &Context = M->getContext();
  std::string Name = F->getName();
  std::string SectionName = ".mips16.fn." + Name;
  std::string StubName = "__fn_stub_" + Name;
  std::string LocalName = "$$__fn_local_" + Name;
  Function *FStub = Function::Create
    (F->getFunctionType(),
     Function::InternalLinkage, StubName, M);
  FStub->addFnAttr("mips16_fp_stub");
  FStub->addFnAttr(llvm::Attribute::Naked);
  FStub->addFnAttr(llvm::Attribute::NoUnwind);
  FStub->addFnAttr(llvm::Attribute::NoInline);
  FStub->addFnAttr("nomips16");
  FStub->setSection(SectionName);
  BasicBlock *BB = BasicBlock::Create(Context, "entry", FStub);

  std::string AsmText;
  if (PicMode) {
    AsmText += ".set noreorder\n";
    AsmText += ".cpload $$25\n";
    AsmText += ".set reorder\n";
    AsmText += ".reloc 0, R_MIPS_NONE, " + Name + "\n";
    AsmText += "la $$25, " + LocalName + "\n";
  } else
    AsmText += "la $$25, " + Name + "\n";
  AsmText += swapFPIntParams(PV, M, LE, false);
  AsmText += "jr $$25\n";
  AsmText += LocalName + " = " + Name + "\n";
  EmitInlineAsm(Context, BB, AsmText);

  new UnreachableInst(FStub->getContext(), BB);
}

//
// Make sure that we know we already need a stub for this function.
// Having called needsFPHelperFromSig
//
static void assureFPCallStub(Function &F, Module *M,
                             const MipsTargetMachine &TM) {
  // for now we only need them for static relocation
  if (TM.isPositionIndependent())
    return;
  LLVMContext &Context = M->getContext();
  bool LE = TM.isLittleEndian();
  std::string Name = F.getName();
  std::string SectionName = ".mips16.call.fp." + Name;
  std::string StubName = "__call_stub_fp_" + Name;
  //
  // see if we already have the stub
  //
  Function *FStub = M->getFunction(StubName);
  if (FStub && !FStub->isDeclaration()) return;
  FStub = Function::Create(F.getFunctionType(),
                           Function::InternalLinkage, StubName, M);
  FStub->addFnAttr("mips16_fp_stub");
  FStub->addFnAttr(llvm::Attribute::Naked);
  FStub->addFnAttr(llvm::Attribute::NoInline);
  FStub->addFnAttr(llvm::Attribute::NoUnwind);
  FStub->addFnAttr("nomips16");
  FStub->setSection(SectionName);
  BasicBlock *BB = BasicBlock::Create(Context, "entry", FStub);
  FPReturnVariant RV = whichFPReturnVariant(FStub->getReturnType());
  FPParamVariant PV = whichFPParamVariantNeeded(F);

  std::string AsmText;
  AsmText += ".set reorder\n";
  AsmText += swapFPIntParams(PV, M, LE, true);
  if (RV != NoFPRet) {
    AsmText += "move $$18, $$31\n";
    AsmText += "jal " + Name + "\n";
  } else {
    AsmText += "lui  $$25, %hi(" + Name + ")\n";
    AsmText += "addiu  $$25, $$25, %lo(" + Name + ")\n";
  }

  switch (RV) {
  case FRet:
    AsmText += "mfc1 $$2, $$f0\n";
    break;

  case DRet:
    if (LE) {
      AsmText += "mfc1 $$2, $$f0\n";
      AsmText += "mfc1 $$3, $$f1\n";
    } else {
      AsmText += "mfc1 $$3, $$f0\n";
      AsmText += "mfc1 $$2, $$f1\n";
    }
    break;

  case CFRet:
    if (LE) {
      AsmText += "mfc1 $$2, $$f0\n";
      AsmText += "mfc1 $$3, $$f2\n";
    } else {
      AsmText += "mfc1 $$3, $$f0\n";
      AsmText += "mfc1 $$3, $$f2\n";
    }
    break;

  case CDRet:
    if (LE) {
      AsmText += "mfc1 $$4, $$f2\n";
      AsmText += "mfc1 $$5, $$f3\n";
      AsmText += "mfc1 $$2, $$f0\n";
      AsmText += "mfc1 $$3, $$f1\n";

    } else {
      AsmText += "mfc1 $$5, $$f2\n";
      AsmText += "mfc1 $$4, $$f3\n";
      AsmText += "mfc1 $$3, $$f0\n";
      AsmText += "mfc1 $$2, $$f1\n";
    }
    break;

  case NoFPRet:
    break;
  }

  if (RV != NoFPRet)
    AsmText += "jr $$18\n";
  else
    AsmText += "jr $$25\n";
  EmitInlineAsm(Context, BB, AsmText);

  new UnreachableInst(Context, BB);
}

//
// Returns of float, double and complex need to be handled with a helper
// function.
//
static bool fixupFPReturnAndCall(Function &F, Module *M,
                                 const MipsTargetMachine &TM) {
  bool Modified = false;
  LLVMContext &C = M->getContext();
  Type *MyVoid = Type::getVoidTy(C);
  for (auto &BB: F)
    for (auto &I: BB) {
      if (const ReturnInst *RI = dyn_cast<ReturnInst>(&I)) {
        Value *RVal = RI->getReturnValue();
        if (!RVal) continue;
        //
        // If there is a return value and it needs a helper function,
        // figure out which one and add a call before the actual
        // return to this helper. The purpose of the helper is to move
        // floating point values from their soft float return mapping to
        // where they would have been mapped to in floating point registers.
        //
        Type *T = RVal->getType();
        FPReturnVariant RV = whichFPReturnVariant(T);
        if (RV == NoFPRet) continue;
        static const char *const Helper[NoFPRet] = {
          "__mips16_ret_sf", "__mips16_ret_df", "__mips16_ret_sc",
          "__mips16_ret_dc"
        };
        const char *Name = Helper[RV];
        AttributeList A;
        Value *Params[] = {RVal};
        Modified = true;
        //
        // These helper functions have a different calling ABI so
        // this __Mips16RetHelper indicates that so that later
        // during call setup, the proper call lowering to the helper
        // functions will take place.
        //
        A = A.addAttribute(C, AttributeList::FunctionIndex,
                           "__Mips16RetHelper");
        A = A.addAttribute(C, AttributeList::FunctionIndex,
                           Attribute::ReadNone);
        A = A.addAttribute(C, AttributeList::FunctionIndex,
                           Attribute::NoInline);
        Value *F = (M->getOrInsertFunction(Name, A, MyVoid, T));
        CallInst::Create(F, Params, "", &I);
      } else if (const CallInst *CI = dyn_cast<CallInst>(&I)) {
        FunctionType *FT = CI->getFunctionType();
        Function *F_ =  CI->getCalledFunction();
        if (needsFPReturnHelper(*FT) &&
            !(F_ && isIntrinsicInline(F_))) {
          Modified=true;
          F.addFnAttr("saveS2");
        }
        if (F_ && !isIntrinsicInline(F_)) {
          // pic mode calls are handled by already defined
          // helper functions
          if (needsFPReturnHelper(*F_)) {
            Modified=true;
            F.addFnAttr("saveS2");
          }
          if (!TM.isPositionIndependent()) {
            if (needsFPHelperFromSig(*F_)) {
              assureFPCallStub(*F_, M, TM);
              Modified=true;
            }
          }
        }
      }
    }
  return Modified;
}

MipsSubtarget::MipsSubtarget(const Triple &TT, const std::string &CPU,
                             const std::string &FS, bool little,
                             const MipsTargetMachine &TM)
    : MipsGenSubtargetInfo(TT, CPU, FS), MipsArchVersion(MipsDefault),
      IsLittle(little), IsSoftFloat(false), IsSingleFloat(false), IsFPXX(false),
      NoABICalls(false), IsFP64bit(false), UseOddSPReg(true),
      IsNaN2008bit(false), IsGP64bit(false), HasVFPU(false), HasCnMips(false),
      HasMips3_32(false), HasMips3_32r2(false), HasMips4_32(false),
      HasMips4_32r2(false), HasMips5_32r2(false), InMips16Mode(false),
      InMips16HardFloat(Mips16HardFloat), InMicroMipsMode(false), HasDSP(false),
      HasDSPR2(false), HasDSPR3(false), AllowMixed16_32(Mixed16_32 | Mips_Os16),
      Os16(Mips_Os16), HasMSA(false), UseTCCInDIV(false), HasSym32(false),
      HasEVA(false), TM(TM), TargetTriple(TT), TSInfo(),
      InstrInfo(
          MipsInstrInfo::create(initializeSubtargetDependencies(CPU, FS, TM))),
      FrameLowering(MipsFrameLowering::create(*this)),
      TLInfo(MipsTargetLowering::create(TM, *this)) {

  PreviousInMips16Mode = InMips16Mode;

  if (MipsArchVersion == MipsDefault)
    MipsArchVersion = Mips32;

  // Don't even attempt to generate code for MIPS-I and MIPS-V. They have not
  // been tested and currently exist for the integrated assembler only.
  if (MipsArchVersion == Mips1)
    report_fatal_error("Code generation for MIPS-I is not implemented", false);
  if (MipsArchVersion == Mips5)
    report_fatal_error("Code generation for MIPS-V is not implemented", false);

  // Check if Architecture and ABI are compatible.
  assert(((!isGP64bit() && isABI_O32()) ||
          (isGP64bit() && (isABI_N32() || isABI_N64()))) &&
         "Invalid  Arch & ABI pair.");

  if (hasMSA() && !isFP64bit())
    report_fatal_error("MSA requires a 64-bit FPU register file (FR=1 mode). "
                       "See -mattr=+fp64.",
                       false);

  if (!isABI_O32() && !useOddSPReg())
    report_fatal_error("-mattr=+nooddspreg requires the O32 ABI.", false);

  if (IsFPXX && (isABI_N32() || isABI_N64()))
    report_fatal_error("FPXX is not permitted for the N32/N64 ABI's.", false);

  if (hasMips32r6()) {
    StringRef ISA = hasMips64r6() ? "MIPS64r6" : "MIPS32r6";

    assert(isFP64bit());
    assert(isNaN2008());
    if (hasDSP())
      report_fatal_error(ISA + " is not compatible with the DSP ASE", false);
  }

  if (NoABICalls && TM.isPositionIndependent())
    report_fatal_error("position-independent code requires '-mabicalls'");

  if (isABI_N64() && !TM.isPositionIndependent() && !hasSym32())
    NoABICalls = true;

  // Set UseSmallSection.
  UseSmallSection = GPOpt;
  if (!NoABICalls && GPOpt) {
    errs() << "warning: cannot use small-data accesses for '-mabicalls'"
           << "\n";
    UseSmallSection = false;
  }
}