C++ SmallVectorImpl::size方法代码示例

// Compare compares the result of MI against zero.  If MI is a suitable load
// instruction and if CCUsers is a single conditional trap on zero, eliminate
// the load and convert the branch to a load-and-trap.  Return true on success.
bool SystemZElimCompare::convertToLoadAndTrap(
    MachineInstr &MI, MachineInstr &Compare,
    SmallVectorImpl<MachineInstr *> &CCUsers) {
  unsigned LATOpcode = TII->getLoadAndTrap(MI.getOpcode());
  if (!LATOpcode)
    return false;

  // Check whether we have a single CondTrap that traps on zero.
  if (CCUsers.size() != 1)
    return false;
  MachineInstr *Branch = CCUsers[0];
  if (Branch->getOpcode() != SystemZ::CondTrap ||
      Branch->getOperand(0).getImm() != SystemZ::CCMASK_ICMP ||
      Branch->getOperand(1).getImm() != SystemZ::CCMASK_CMP_EQ)
    return false;

  // We already know that there are no references to the register between
  // MI and Compare.  Make sure that there are also no references between
  // Compare and Branch.
  unsigned SrcReg = getCompareSourceReg(Compare);
  MachineBasicBlock::iterator MBBI = Compare, MBBE = Branch;
  for (++MBBI; MBBI != MBBE; ++MBBI)
    if (getRegReferences(*MBBI, SrcReg))
      return false;

  // The transformation is OK.  Rebuild Branch as a load-and-trap.
  while (Branch->getNumOperands())
    Branch->RemoveOperand(0);
  Branch->setDesc(TII->get(LATOpcode));
  MachineInstrBuilder(*Branch->getParent()->getParent(), Branch)
      .add(MI.getOperand(0))
      .add(MI.getOperand(1))
      .add(MI.getOperand(2))
      .add(MI.getOperand(3));
  MI.eraseFromParent();
  return true;
}

bool convertUTF8ToUTF16String(StringRef SrcUTF8,
                              SmallVectorImpl<UTF16> &DstUTF16) {
  assert(DstUTF16.empty());

  // Avoid OOB by returning early on empty input.
  if (SrcUTF8.empty()) {
    DstUTF16.push_back(0);
    DstUTF16.pop_back();
    return true;
  }

  const UTF8 *Src = reinterpret_cast<const UTF8 *>(SrcUTF8.begin());
  const UTF8 *SrcEnd = reinterpret_cast<const UTF8 *>(SrcUTF8.end());

  // Allocate the same number of UTF-16 code units as UTF-8 code units. Encoding
  // as UTF-16 should always require the same amount or less code units than the
  // UTF-8 encoding.  Allocate one extra byte for the null terminator though,
  // so that someone calling DstUTF16.data() gets a null terminated string.
  // We resize down later so we don't have to worry that this over allocates.
  DstUTF16.resize(SrcUTF8.size()+1);
  UTF16 *Dst = &DstUTF16[0];
  UTF16 *DstEnd = Dst + DstUTF16.size();

  ConversionResult CR =
      ConvertUTF8toUTF16(&Src, SrcEnd, &Dst, DstEnd, strictConversion);
  assert(CR != targetExhausted);

  if (CR != conversionOK) {
    DstUTF16.clear();
    return false;
  }

  DstUTF16.resize(Dst - &DstUTF16[0]);
  DstUTF16.push_back(0);
  DstUTF16.pop_back();
  return true;
}

void append(SmallVectorImpl<char> &path, Style style, const Twine &a,
            const Twine &b, const Twine &c, const Twine &d) {
  SmallString<32> a_storage;
  SmallString<32> b_storage;
  SmallString<32> c_storage;
  SmallString<32> d_storage;

  SmallVector<StringRef, 4> components;
  if (!a.isTriviallyEmpty()) components.push_back(a.toStringRef(a_storage));
  if (!b.isTriviallyEmpty()) components.push_back(b.toStringRef(b_storage));
  if (!c.isTriviallyEmpty()) components.push_back(c.toStringRef(c_storage));
  if (!d.isTriviallyEmpty()) components.push_back(d.toStringRef(d_storage));

  for (auto &component : components) {
    bool path_has_sep =
        !path.empty() && is_separator(path[path.size() - 1], style);
    if (path_has_sep) {
      // Strip separators from beginning of component.
      size_t loc = component.find_first_not_of(separators(style));
      StringRef c = component.substr(loc);

      // Append it.
      path.append(c.begin(), c.end());
      continue;
    }

    bool component_has_sep =
        !component.empty() && is_separator(component[0], style);
    if (!component_has_sep &&
        !(path.empty() || has_root_name(component, style))) {
      // Add a separator.
      path.push_back(preferred_separator(style));
    }

    path.append(component.begin(), component.end());
  }
}

/*!
  \note We are really pessimistic here about what kind of a load we're doing.
 */
void SPUInstrInfo::loadRegFromAddr(MachineFunction &MF, unsigned DestReg,
                                   SmallVectorImpl<MachineOperand> &Addr,
                                   const TargetRegisterClass *RC,
                                   SmallVectorImpl<MachineInstr*> &NewMIs)
    const {
  cerr << "loadRegToAddr() invoked!\n";
  abort();

  if (Addr[0].isFI()) {
    /* do what loadRegFromStackSlot does here... */
  } else {
    unsigned Opc = 0;
    if (RC == SPU::R8CRegisterClass) {
      /* do brilliance here */
    } else if (RC == SPU::R16CRegisterClass) {
      /* Opc = PPC::LWZ; */
    } else if (RC == SPU::R32CRegisterClass) {
      /* Opc = PPC::LD; */
    } else if (RC == SPU::R32FPRegisterClass) {
      /* Opc = PPC::LFD; */
    } else if (RC == SPU::R64FPRegisterClass) {
      /* Opc = PPC::LFS; */
    } else if (RC == SPU::VECREGRegisterClass) {
      /* Opc = PPC::LVX; */
    } else if (RC == SPU::GPRCRegisterClass) {
      /* Opc = something else! */
    } else {
      assert(0 && "Unknown regclass!");
      abort();
    }
    DebugLoc DL = DebugLoc::getUnknownLoc();
    MachineInstrBuilder MIB = BuildMI(MF, DL, get(Opc), DestReg);
    for (unsigned i = 0, e = Addr.size(); i != e; ++i)
      MIB.addOperand(Addr[i]);
    NewMIs.push_back(MIB);
  }
}

static bool isAlternateVectorMask(SmallVectorImpl<int> &Mask) {
  bool isAlternate = true;
  unsigned MaskSize = Mask.size();

  // Example: shufflevector A, B, <0,5,2,7>
  for (unsigned i = 0; i < MaskSize && isAlternate; ++i) {
    if (Mask[i] < 0)
      continue;
    isAlternate = Mask[i] == (int)((i & 1) ? MaskSize + i : i);
  }

  if (isAlternate)
    return true;

  isAlternate = true;
  // Example: shufflevector A, B, <4,1,6,3>
  for (unsigned i = 0; i < MaskSize && isAlternate; ++i) {
    if (Mask[i] < 0)
      continue;
    isAlternate = Mask[i] == (int)((i & 1) ? i : MaskSize + i);
  }

  return isAlternate;
}

void Sema::EraseUnwantedCUDAMatches(
    const FunctionDecl *Caller,
    SmallVectorImpl<std::pair<DeclAccessPair, FunctionDecl *>> &Matches) {
  if (Matches.size() <= 1)
    return;

  using Pair = std::pair<DeclAccessPair, FunctionDecl*>;

  // Gets the CUDA function preference for a call from Caller to Match.
  auto GetCFP = [&](const Pair &Match) {
    return IdentifyCUDAPreference(Caller, Match.second);
  };

  // Find the best call preference among the functions in Matches.
  CUDAFunctionPreference BestCFP = GetCFP(*std::max_element(
      Matches.begin(), Matches.end(),
      [&](const Pair &M1, const Pair &M2) { return GetCFP(M1) < GetCFP(M2); }));

  // Erase all functions with lower priority.
  Matches.erase(
      llvm::remove_if(
          Matches, [&](const Pair &Match) { return GetCFP(Match) < BestCFP; }),
      Matches.end());
}

StringRef
camel_case::toLowercaseInitialisms(StringRef string,
                                   SmallVectorImpl<char> &scratch) {

  if (string.empty())
    return string;

  // Already lowercase.
  if (!clang::isUppercase(string[0]))
    return string;

  // Lowercase until we hit the an uppercase letter followed by a
  // non-uppercase letter.
  llvm::SmallString<32> scratchStr;
  for (unsigned i = 0, n = string.size(); i != n; ++i) {
    // If the next character is not uppercase, stop.
    if (i < n - 1 && !clang::isUppercase(string[i+1])) {
      // If the next non-uppercase character was not a letter, we seem
      // to have a plural, or we're at the beginning, we should still
      // lowercase the character we're on.
      if (i == 0 || !clang::isLetter(string[i+1]) ||
          isPluralSuffix(camel_case::getFirstWord(string.substr(i+1)))) {
        scratchStr.push_back(clang::toLowercase(string[i]));
        ++i;
      }

      scratchStr.append(string.substr(i));
      break;
    }

    scratchStr.push_back(clang::toLowercase(string[i]));
  }

  scratch = scratchStr;
  return {scratch.begin(), scratch.size()};
}

/// \brief Diagnose all of the unexpanded parameter packs in the given
/// vector.
static void 
DiagnoseUnexpandedParameterPacks(Sema &S, SourceLocation Loc,
                                 Sema::UnexpandedParameterPackContext UPPC,
             const SmallVectorImpl<UnexpandedParameterPack> &Unexpanded) {
  SmallVector<SourceLocation, 4> Locations;
  SmallVector<IdentifierInfo *, 4> Names;
  llvm::SmallPtrSet<IdentifierInfo *, 4> NamesKnown;

  for (unsigned I = 0, N = Unexpanded.size(); I != N; ++I) {
    IdentifierInfo *Name = 0;
    if (const TemplateTypeParmType *TTP
          = Unexpanded[I].first.dyn_cast<const TemplateTypeParmType *>())
      Name = TTP->getIdentifier();
    else
      Name = Unexpanded[I].first.get<NamedDecl *>()->getIdentifier();

    if (Name && NamesKnown.insert(Name))
      Names.push_back(Name);

    if (Unexpanded[I].second.isValid())
      Locations.push_back(Unexpanded[I].second);
  }

  DiagnosticBuilder DB
    = Names.size() == 0? S.Diag(Loc, diag::err_unexpanded_parameter_pack_0)
                           << (int)UPPC
    : Names.size() == 1? S.Diag(Loc, diag::err_unexpanded_parameter_pack_1)
                           << (int)UPPC << Names[0]
    : Names.size() == 2? S.Diag(Loc, diag::err_unexpanded_parameter_pack_2)
                           << (int)UPPC << Names[0] << Names[1]
    : S.Diag(Loc, diag::err_unexpanded_parameter_pack_3_or_more)
        << (int)UPPC << Names[0] << Names[1];

  for (unsigned I = 0, N = Locations.size(); I != N; ++I)
    DB << SourceRange(Locations[I]);
}

void AlphaInstrInfo::loadRegFromAddr(MachineFunction &MF, unsigned DestReg,
                                        SmallVectorImpl<MachineOperand> &Addr,
                                        const TargetRegisterClass *RC,
                                 SmallVectorImpl<MachineInstr*> &NewMIs) const {
  unsigned Opc = 0;
  if (RC == Alpha::F4RCRegisterClass)
    Opc = Alpha::LDS;
  else if (RC == Alpha::F8RCRegisterClass)
    Opc = Alpha::LDT;
  else if (RC == Alpha::GPRCRegisterClass)
    Opc = Alpha::LDQ;
  else
    abort();
  MachineInstrBuilder MIB = 
    BuildMI(MF, get(Opc), DestReg);
  for (unsigned i = 0, e = Addr.size(); i != e; ++i) {
    MachineOperand &MO = Addr[i];
    if (MO.isReg())
      MIB.addReg(MO.getReg(), MO.isDef(), MO.isImplicit());
    else
      MIB.addImm(MO.getImm());
  }
  NewMIs.push_back(MIB);
}

void Instruction::getAllMetadataImpl(SmallVectorImpl<std::pair<unsigned,
                                       MDNode*> > &Result) const {
  Result.clear();
  
  // Handle 'dbg' as a special case since it is not stored in the hash table.
  if (!DbgLoc.isUnknown()) {
    Result.push_back(std::make_pair((unsigned)LLVMContext::MD_dbg,
                                    DbgLoc.getAsMDNode(getContext())));
    if (!hasMetadataHashEntry()) return;
  }
  
  assert(hasMetadataHashEntry() &&
         getContext().pImpl->MetadataStore.count(this) &&
         "Shouldn't have called this");
  const LLVMContextImpl::MDMapTy &Info =
    getContext().pImpl->MetadataStore.find(this)->second;
  assert(!Info.empty() && "Shouldn't have called this");

  Result.append(Info.begin(), Info.end());

  // Sort the resulting array so it is stable.
  if (Result.size() > 1)
    array_pod_sort(Result.begin(), Result.end());
}

void SPUInstrInfo::storeRegToAddr(MachineFunction &MF, unsigned SrcReg,
                                  bool isKill,
                                  SmallVectorImpl<MachineOperand> &Addr,
                                  const TargetRegisterClass *RC,
                                  SmallVectorImpl<MachineInstr*> &NewMIs) const {
  cerr << "storeRegToAddr() invoked!\n";
  abort();

  if (Addr[0].isFI()) {
    /* do what storeRegToStackSlot does here */
  } else {
    unsigned Opc = 0;
    if (RC == SPU::GPRCRegisterClass) {
      /* Opc = PPC::STW; */
    } else if (RC == SPU::R16CRegisterClass) {
      /* Opc = PPC::STD; */
    } else if (RC == SPU::R32CRegisterClass) {
      /* Opc = PPC::STFD; */
    } else if (RC == SPU::R32FPRegisterClass) {
      /* Opc = PPC::STFD; */
    } else if (RC == SPU::R64FPRegisterClass) {
      /* Opc = PPC::STFS; */
    } else if (RC == SPU::VECREGRegisterClass) {
      /* Opc = PPC::STVX; */
    } else {
      assert(0 && "Unknown regclass!");
      abort();
    }
    DebugLoc DL = DebugLoc::getUnknownLoc();
    MachineInstrBuilder MIB = BuildMI(MF, DL, get(Opc))
      .addReg(SrcReg, false, false, isKill);
    for (unsigned i = 0, e = Addr.size(); i != e; ++i)
      MIB.addOperand(Addr[i]);
    NewMIs.push_back(MIB);
  }
}

bool GlobalMerge::doMerge(SmallVectorImpl<GlobalVariable*> &Globals,
                          Module &M, bool isConst, unsigned AddrSpace) const {
  auto &DL = M.getDataLayout();
  // FIXME: Find better heuristics
  std::stable_sort(Globals.begin(), Globals.end(),
                   [&DL](const GlobalVariable *GV1, const GlobalVariable *GV2) {
                     return DL.getTypeAllocSize(GV1->getValueType()) <
                            DL.getTypeAllocSize(GV2->getValueType());
                   });

  // If we want to just blindly group all globals together, do so.
  if (!GlobalMergeGroupByUse) {
    BitVector AllGlobals(Globals.size());
    AllGlobals.set();
    return doMerge(Globals, AllGlobals, M, isConst, AddrSpace);
  }

  // If we want to be smarter, look at all uses of each global, to try to
  // discover all sets of globals used together, and how many times each of
  // these sets occurred.
  //
  // Keep this reasonably efficient, by having an append-only list of all sets
  // discovered so far (UsedGlobalSet), and mapping each "together-ness" unit of
  // code (currently, a Function) to the set of globals seen so far that are
  // used together in that unit (GlobalUsesByFunction).
  //
  // When we look at the Nth global, we know that any new set is either:
  // - the singleton set {N}, containing this global only, or
  // - the union of {N} and a previously-discovered set, containing some
  //   combination of the previous N-1 globals.
  // Using that knowledge, when looking at the Nth global, we can keep:
  // - a reference to the singleton set {N} (CurGVOnlySetIdx)
  // - a list mapping each previous set to its union with {N} (EncounteredUGS),
  //   if it actually occurs.

  // We keep track of the sets of globals used together "close enough".
  struct UsedGlobalSet {
    BitVector Globals;
    unsigned UsageCount = 1;

    UsedGlobalSet(size_t Size) : Globals(Size) {}
  };

  // Each set is unique in UsedGlobalSets.
  std::vector<UsedGlobalSet> UsedGlobalSets;

  // Avoid repeating the create-global-set pattern.
  auto CreateGlobalSet = [&]() -> UsedGlobalSet & {
    UsedGlobalSets.emplace_back(Globals.size());
    return UsedGlobalSets.back();
  };

  // The first set is the empty set.
  CreateGlobalSet().UsageCount = 0;

  // We define "close enough" to be "in the same function".
  // FIXME: Grouping uses by function is way too aggressive, so we should have
  // a better metric for distance between uses.
  // The obvious alternative would be to group by BasicBlock, but that's in
  // turn too conservative..
  // Anything in between wouldn't be trivial to compute, so just stick with
  // per-function grouping.

  // The value type is an index into UsedGlobalSets.
  // The default (0) conveniently points to the empty set.
  DenseMap<Function *, size_t /*UsedGlobalSetIdx*/> GlobalUsesByFunction;

  // Now, look at each merge-eligible global in turn.

  // Keep track of the sets we already encountered to which we added the
  // current global.
  // Each element matches the same-index element in UsedGlobalSets.
  // This lets us efficiently tell whether a set has already been expanded to
  // include the current global.
  std::vector<size_t> EncounteredUGS;

  for (size_t GI = 0, GE = Globals.size(); GI != GE; ++GI) {
    GlobalVariable *GV = Globals[GI];

    // Reset the encountered sets for this global...
    std::fill(EncounteredUGS.begin(), EncounteredUGS.end(), 0);
    // ...and grow it in case we created new sets for the previous global.
    EncounteredUGS.resize(UsedGlobalSets.size());

    // We might need to create a set that only consists of the current global.
    // Keep track of its index into UsedGlobalSets.
    size_t CurGVOnlySetIdx = 0;

    // For each global, look at all its Uses.
    for (auto &U : GV->uses()) {
      // This Use might be a ConstantExpr.  We're interested in Instruction
      // users, so look through ConstantExpr...
      Use *UI, *UE;
      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U.getUser())) {
        if (CE->use_empty())
          continue;
        UI = &*CE->use_begin();
        UE = nullptr;
      } else if (isa<Instruction>(U.getUser())) {
        UI = &U;
//.........这里部分代码省略.........

bool GlobalMerge::doMerge(SmallVectorImpl<GlobalVariable *> &Globals,
                          const BitVector &GlobalSet, Module &M, bool isConst,
                          unsigned AddrSpace) const {

  Type *Int32Ty = Type::getInt32Ty(M.getContext());
  auto &DL = M.getDataLayout();

  assert(Globals.size() > 1);

  DEBUG(dbgs() << " Trying to merge set, starts with #"
               << GlobalSet.find_first() << "\n");

  ssize_t i = GlobalSet.find_first();
  while (i != -1) {
    ssize_t j = 0;
    uint64_t MergedSize = 0;
    std::vector<Type*> Tys;
    std::vector<Constant*> Inits;

    bool HasExternal = false;
    GlobalVariable *TheFirstExternal = 0;
    for (j = i; j != -1; j = GlobalSet.find_next(j)) {
      Type *Ty = Globals[j]->getType()->getElementType();
      MergedSize += DL.getTypeAllocSize(Ty);
      if (MergedSize > MaxOffset) {
        break;
      }
      Tys.push_back(Ty);
      Inits.push_back(Globals[j]->getInitializer());

      if (Globals[j]->hasExternalLinkage() && !HasExternal) {
        HasExternal = true;
        TheFirstExternal = Globals[j];
      }
    }

    // If merged variables doesn't have external linkage, we needn't to expose
    // the symbol after merging.
    GlobalValue::LinkageTypes Linkage = HasExternal
                                            ? GlobalValue::ExternalLinkage
                                            : GlobalValue::InternalLinkage;

    StructType *MergedTy = StructType::get(M.getContext(), Tys);
    Constant *MergedInit = ConstantStruct::get(MergedTy, Inits);

    // If merged variables have external linkage, we use symbol name of the
    // first variable merged as the suffix of global symbol name. This would
    // be able to avoid the link-time naming conflict for globalm symbols.
    GlobalVariable *MergedGV = new GlobalVariable(
        M, MergedTy, isConst, Linkage, MergedInit,
        HasExternal ? "_MergedGlobals_" + TheFirstExternal->getName()
                    : "_MergedGlobals",
        nullptr, GlobalVariable::NotThreadLocal, AddrSpace);

    for (ssize_t k = i, idx = 0; k != j; k = GlobalSet.find_next(k)) {
      GlobalValue::LinkageTypes Linkage = Globals[k]->getLinkage();
      std::string Name = Globals[k]->getName();

      Constant *Idx[2] = {
        ConstantInt::get(Int32Ty, 0),
        ConstantInt::get(Int32Ty, idx++)
      };
      Constant *GEP =
          ConstantExpr::getInBoundsGetElementPtr(MergedTy, MergedGV, Idx);
      Globals[k]->replaceAllUsesWith(GEP);
      Globals[k]->eraseFromParent();

      if (Linkage != GlobalValue::InternalLinkage) {
        // Generate a new alias...
        auto *PTy = cast<PointerType>(GEP->getType());
        GlobalAlias::create(PTy, Linkage, Name, GEP, &M);
      }

      NumMerged++;
    }
    i = j;
  }

  return true;
}

void LiveRange::join(LiveRange &Other,
                     const int *LHSValNoAssignments,
                     const int *RHSValNoAssignments,
                     SmallVectorImpl<VNInfo *> &NewVNInfo) {
  verify();

  // Determine if any of our values are mapped.  This is uncommon, so we want
  // to avoid the range scan if not.
  bool MustMapCurValNos = false;
  unsigned NumVals = getNumValNums();
  unsigned NumNewVals = NewVNInfo.size();
  for (unsigned i = 0; i != NumVals; ++i) {
    unsigned LHSValID = LHSValNoAssignments[i];
    if (i != LHSValID ||
        (NewVNInfo[LHSValID] && NewVNInfo[LHSValID] != getValNumInfo(i))) {
      MustMapCurValNos = true;
      break;
    }
  }

  // If we have to apply a mapping to our base range assignment, rewrite it now.
  if (MustMapCurValNos && !empty()) {
    // Map the first live range.

    iterator OutIt = begin();
    OutIt->valno = NewVNInfo[LHSValNoAssignments[OutIt->valno->id]];
    for (iterator I = std::next(OutIt), E = end(); I != E; ++I) {
      VNInfo* nextValNo = NewVNInfo[LHSValNoAssignments[I->valno->id]];
      assert(nextValNo != 0 && "Huh?");

      // If this live range has the same value # as its immediate predecessor,
      // and if they are neighbors, remove one Segment.  This happens when we
      // have [0,4:0)[4,7:1) and map 0/1 onto the same value #.
      if (OutIt->valno == nextValNo && OutIt->end == I->start) {
        OutIt->end = I->end;
      } else {
        // Didn't merge. Move OutIt to the next segment,
        ++OutIt;
        OutIt->valno = nextValNo;
        if (OutIt != I) {
          OutIt->start = I->start;
          OutIt->end = I->end;
        }
      }
    }
    // If we merge some segments, chop off the end.
    ++OutIt;
    segments.erase(OutIt, end());
  }

  // Rewrite Other values before changing the VNInfo ids.
  // This can leave Other in an invalid state because we're not coalescing
  // touching segments that now have identical values. That's OK since Other is
  // not supposed to be valid after calling join();
  for (iterator I = Other.begin(), E = Other.end(); I != E; ++I)
    I->valno = NewVNInfo[RHSValNoAssignments[I->valno->id]];

  // Update val# info. Renumber them and make sure they all belong to this
  // LiveRange now. Also remove dead val#'s.
  unsigned NumValNos = 0;
  for (unsigned i = 0; i < NumNewVals; ++i) {
    VNInfo *VNI = NewVNInfo[i];
    if (VNI) {
      if (NumValNos >= NumVals)
        valnos.push_back(VNI);
      else
        valnos[NumValNos] = VNI;
      VNI->id = NumValNos++;  // Renumber val#.
    }
  }
  if (NumNewVals < NumVals)
    valnos.resize(NumNewVals);  // shrinkify

  // Okay, now insert the RHS live segments into the LHS.
  LiveRangeUpdater Updater(this);
  for (iterator I = Other.begin(), E = Other.end(); I != E; ++I)
    Updater.add(*I);
}

// The CC users in CCUsers are testing the result of a comparison of some
// value X against zero and we know that any CC value produced by MI
// would also reflect the value of X.  Try to adjust CCUsers so that
// they test the result of MI directly, returning true on success.
// Leave everything unchanged on failure.
bool SystemZElimCompare::
adjustCCMasksForInstr(MachineInstr *MI, MachineInstr *Compare,
                      SmallVectorImpl<MachineInstr *> &CCUsers) {
  int Opcode = MI->getOpcode();
  const MCInstrDesc &Desc = TII->get(Opcode);
  unsigned MIFlags = Desc.TSFlags;

  // See which compare-style condition codes are available.
  unsigned ReusableCCMask = SystemZII::getCompareZeroCCMask(MIFlags);

  // For unsigned comparisons with zero, only equality makes sense.
  unsigned CompareFlags = Compare->getDesc().TSFlags;
  if (CompareFlags & SystemZII::IsLogical)
    ReusableCCMask &= SystemZ::CCMASK_CMP_EQ;

  if (ReusableCCMask == 0)
    return false;

  unsigned CCValues = SystemZII::getCCValues(MIFlags);
  assert((ReusableCCMask & ~CCValues) == 0 && "Invalid CCValues");

  // Now check whether these flags are enough for all users.
  SmallVector<MachineOperand *, 4> AlterMasks;
  for (unsigned int I = 0, E = CCUsers.size(); I != E; ++I) {
    MachineInstr *MI = CCUsers[I];

    // Fail if this isn't a use of CC that we understand.
    unsigned Flags = MI->getDesc().TSFlags;
    unsigned FirstOpNum;
    if (Flags & SystemZII::CCMaskFirst)
      FirstOpNum = 0;
    else if (Flags & SystemZII::CCMaskLast)
      FirstOpNum = MI->getNumExplicitOperands() - 2;
    else
      return false;

    // Check whether the instruction predicate treats all CC values
    // outside of ReusableCCMask in the same way.  In that case it
    // doesn't matter what those CC values mean.
    unsigned CCValid = MI->getOperand(FirstOpNum).getImm();
    unsigned CCMask = MI->getOperand(FirstOpNum + 1).getImm();
    unsigned OutValid = ~ReusableCCMask & CCValid;
    unsigned OutMask = ~ReusableCCMask & CCMask;
    if (OutMask != 0 && OutMask != OutValid)
      return false;

    AlterMasks.push_back(&MI->getOperand(FirstOpNum));
    AlterMasks.push_back(&MI->getOperand(FirstOpNum + 1));
  }

  // All users are OK.  Adjust the masks for MI.
  for (unsigned I = 0, E = AlterMasks.size(); I != E; I += 2) {
    AlterMasks[I]->setImm(CCValues);
    unsigned CCMask = AlterMasks[I + 1]->getImm();
    if (CCMask & ~ReusableCCMask)
      AlterMasks[I + 1]->setImm((CCMask & ReusableCCMask) |
                                (CCValues & ~ReusableCCMask));
  }

  // CC is now live after MI.
  int CCDef = MI->findRegisterDefOperandIdx(SystemZ::CC, false, true, TRI);
  assert(CCDef >= 0 && "Couldn't find CC set");
  MI->getOperand(CCDef).setIsDead(false);

  // Clear any intervening kills of CC.
  MachineBasicBlock::iterator MBBI = MI, MBBE = Compare;
  for (++MBBI; MBBI != MBBE; ++MBBI)
    MBBI->clearRegisterKills(SystemZ::CC, TRI);

  return true;
}