[BasicBlock] Define class successor and predecessor iterators.

[asbirlea]

Summary

Define class-specific successor and predecessor iterators.
These match the existing interface in MachineBasicBlock and clang::CFGBlock.

[asbirlea]

Updated to have the global APIs as wrappers over class-specific ones and include the added header split off.

[asbirlea]

No longer needed. See discussion: http://lists.llvm.org/pipermail/llvm-dev/2020-March/139888.html

llvm/include/llvm/IR/BasicBlock.h

 
 #include "llvm-c/Types.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/ADT/ilist.h"
 #include "llvm/ADT/ilist_node.h"
 #include "llvm/ADT/iterator.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/IR/Instruction.h"
+#include "llvm/IR/IteratorsHelper.h"
 #include "llvm/IR/SymbolTableListTraits.h"
 #include "llvm/IR/Value.h"
 #include "llvm/Support/CBindingWrapping.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Compiler.h"
 #include <cassert>
 #include <cstddef>
 #include <iterator>
public:
   LLVMContext &getContext() const;
 
   /// Instruction iterators...
   using iterator = InstListType::iterator;
   using const_iterator = InstListType::const_iterator;
   using reverse_iterator = InstListType::reverse_iterator;
   using const_reverse_iterator = InstListType::const_reverse_iterator;
 
+  /// Successor and predecessor iterators.
+  using succ_iterator = SuccIterator<Instruction, BasicBlock>;
+  using const_succ_iterator = SuccIterator<const Instruction, const BasicBlock>;
+  using succ_range = iterator_range<succ_iterator>;
+  using const_succ_range = iterator_range<const_succ_iterator>;
+  using pred_iterator = PredIterator<BasicBlock, Value::user_iterator>;
+  using const_pred_iterator =
+      PredIterator<const BasicBlock, Value::const_user_iterator>;
+  using pred_range = iterator_range<pred_iterator>;
+  using const_pred_range = iterator_range<const_pred_iterator>;
+
+  succ_iterator succ_begin() { return succ_iterator(getTerminator()); }
+  const_succ_iterator succ_begin() const {
+    return const_succ_iterator(getTerminator());
+  }
+  succ_iterator succ_end() { return succ_iterator(getTerminator(), true); }
+  const_succ_iterator succ_end() const {
+    return const_succ_iterator(getTerminator(), true);
+  }
+  bool succ_empty() const { return succ_begin() == succ_end(); }
+  unsigned succ_size() const { return std::distance(succ_begin(), succ_end()); }
+  succ_range successors() { return succ_range(succ_begin(), succ_end()); }
+  const_succ_range successors() const {
+    return const_succ_range(succ_begin(), succ_end());
+  }
+  pred_iterator pred_begin() { return pred_iterator(this); }
+  const_pred_iterator pred_begin() const { return const_pred_iterator(this); }
+  pred_iterator pred_end() { return pred_iterator(this, true); }
+  const_pred_iterator pred_end() const {
+    return const_pred_iterator(this, true);
+  }
+  bool pred_empty() const { return pred_begin() == pred_end(); }
+  unsigned pred_size() const { return std::distance(pred_begin(), pred_end()); }
+  pred_range predecessors() { return pred_range(pred_begin(), pred_end()); }
+  const_pred_range predecessors() const {
+    return const_pred_range(pred_begin(), pred_end());
+  }
+
   /// Creates a new BasicBlock.
   ///
   /// If the Parent parameter is specified, the basic block is automatically
   /// inserted at either the end of the function (if InsertBefore is 0), or
   /// before the specified basic block.
   static BasicBlock *Create(LLVMContext &Context, const Twine &Name = "",
                             Function *Parent = nullptr,
                             BasicBlock *InsertBefore = nullptr) {

llvm/include/llvm/IR/CFG.h

 #include "llvm/Support/Casting.h"
 #include "llvm/Support/type_traits.h"
 #include <cassert>
 #include <cstddef>
 #include <iterator>
 
 namespace llvm {
 
-//===----------------------------------------------------------------------===//
-// BasicBlock pred_iterator definition
-//===----------------------------------------------------------------------===//
-
-template <class Ptr, class USE_iterator> // Predecessor Iterator
-class PredIterator : public std::iterator<std::forward_iterator_tag,
-                                          Ptr, ptrdiff_t, Ptr*, Ptr*> {
-  using super =
-      std::iterator<std::forward_iterator_tag, Ptr, ptrdiff_t, Ptr*, Ptr*>;
-  using Self = PredIterator<Ptr, USE_iterator>;
-  USE_iterator It;
-
-  inline void advancePastNonTerminators() {
-    // Loop to ignore non-terminator uses (for example BlockAddresses).
-    while (!It.atEnd()) {
-      if (auto *Inst = dyn_cast<Instruction>(*It))
-        if (Inst->isTerminator())
-          break;
-
-      ++It;
-    }
-  }
-
-public:
-  using pointer = typename super::pointer;
-  using reference = typename super::reference;
-
-  PredIterator() = default;
-  explicit inline PredIterator(Ptr *bb) : It(bb->user_begin()) {
-    advancePastNonTerminators();
-  }
-  inline PredIterator(Ptr *bb, bool) : It(bb->user_end()) {}
-
-  inline bool operator==(const Self& x) const { return It == x.It; }
-  inline bool operator!=(const Self& x) const { return !operator==(x); }
-
-  inline reference operator*() const {
-    assert(!It.atEnd() && "pred_iterator out of range!");
-    return cast<Instruction>(*It)->getParent();
-  }
-  inline pointer *operator->() const { return &operator*(); }
-
-  inline Self& operator++() {   // Preincrement
-    assert(!It.atEnd() && "pred_iterator out of range!");
-    ++It; advancePastNonTerminators();
-    return *this;
-  }
-
-  inline Self operator++(int) { // Postincrement
-    Self tmp = *this; ++*this; return tmp;
-  }
-
-  /// getOperandNo - Return the operand number in the predecessor's
-  /// terminator of the successor.
-  unsigned getOperandNo() const {
-    return It.getOperandNo();
-  }
-
-  /// getUse - Return the operand Use in the predecessor's terminator
-  /// of the successor.
-  Use &getUse() const {
-    return It.getUse();
-  }
-};
-
-using pred_iterator = PredIterator<BasicBlock, Value::user_iterator>;
-using const_pred_iterator =
-    PredIterator<const BasicBlock, Value::const_user_iterator>;
+using pred_iterator = BasicBlock::pred_iterator;
+using const_pred_iterator = BasicBlock::const_pred_iterator;
 using pred_range = iterator_range<pred_iterator>;
 using const_pred_range = iterator_range<const_pred_iterator>;
 
-inline pred_iterator pred_begin(BasicBlock *BB) { return pred_iterator(BB); }
+inline pred_iterator pred_begin(BasicBlock *BB) { return BB->pred_begin(); }
 inline const_pred_iterator pred_begin(const BasicBlock *BB) {
-  return const_pred_iterator(BB);
+  return BB->pred_begin();
 }
-inline pred_iterator pred_end(BasicBlock *BB) { return pred_iterator(BB, true);}
+inline pred_iterator pred_end(BasicBlock *BB) { return BB->pred_end(); }
 inline const_pred_iterator pred_end(const BasicBlock *BB) {
-  return const_pred_iterator(BB, true);
+  return BB->pred_end();
 }
 inline bool pred_empty(const BasicBlock *BB) {
   return pred_begin(BB) == pred_end(BB);
 }
 /// Get the number of predecessors of \p BB. This is a linear time operation.
 /// Use \ref BasicBlock::hasNPredecessors() or hasNPredecessorsOrMore if able.
 inline unsigned pred_size(const BasicBlock *BB) {
   return std::distance(pred_begin(BB), pred_end(BB));
 }
 inline pred_range predecessors(BasicBlock *BB) {
   return pred_range(pred_begin(BB), pred_end(BB));
 }
 inline const_pred_range predecessors(const BasicBlock *BB) {
   return const_pred_range(pred_begin(BB), pred_end(BB));
 }
 
-//===----------------------------------------------------------------------===//
-// Instruction and BasicBlock succ_iterator helpers
-//===----------------------------------------------------------------------===//
-
-template <class InstructionT, class BlockT>
-class SuccIterator
-    : public iterator_facade_base<SuccIterator<InstructionT, BlockT>,
-                                  std::random_access_iterator_tag, BlockT, int,
-                                  BlockT *, BlockT *> {
-public:
-  using difference_type = int;
-  using pointer = BlockT *;
-  using reference = BlockT *;
-
-private:
-  InstructionT *Inst;
-  int Idx;
-  using Self = SuccIterator<InstructionT, BlockT>;
-
-  inline bool index_is_valid(int Idx) {
-    // Note that we specially support the index of zero being valid even in the
-    // face of a null instruction.
-    return Idx >= 0 && (Idx == 0 || Idx <= (int)Inst->getNumSuccessors());
-  }
-
-  /// Proxy object to allow write access in operator[]
-  class SuccessorProxy {
-    Self It;
-
-  public:
-    explicit SuccessorProxy(const Self &It) : It(It) {}
-
-    SuccessorProxy(const SuccessorProxy &) = default;
-
-    SuccessorProxy &operator=(SuccessorProxy RHS) {
-      *this = reference(RHS);
-      return *this;
-    }
-
-    SuccessorProxy &operator=(reference RHS) {
-      It.Inst->setSuccessor(It.Idx, RHS);
-      return *this;
-    }
-
-    operator reference() const { return *It; }
-  };
-
-public:
-  // begin iterator
-  explicit inline SuccIterator(InstructionT *Inst) : Inst(Inst), Idx(0) {}
-  // end iterator
-  inline SuccIterator(InstructionT *Inst, bool) : Inst(Inst) {
-    if (Inst)
-      Idx = Inst->getNumSuccessors();
-    else
-      // Inst == NULL happens, if a basic block is not fully constructed and
-      // consequently getTerminator() returns NULL. In this case we construct
-      // a SuccIterator which describes a basic block that has zero
-      // successors.
-      // Defining SuccIterator for incomplete and malformed CFGs is especially
-      // useful for debugging.
-      Idx = 0;
-  }
-
-  /// This is used to interface between code that wants to
-  /// operate on terminator instructions directly.
-  int getSuccessorIndex() const { return Idx; }
-
-  inline bool operator==(const Self &x) const { return Idx == x.Idx; }
-
-  inline BlockT *operator*() const { return Inst->getSuccessor(Idx); }
-
-  // We use the basic block pointer directly for operator->.
-  inline BlockT *operator->() const { return operator*(); }
-
-  inline bool operator<(const Self &RHS) const {
-    assert(Inst == RHS.Inst && "Cannot compare iterators of different blocks!");
-    return Idx < RHS.Idx;
-  }
-
-  int operator-(const Self &RHS) const {
-    assert(Inst == RHS.Inst && "Cannot compare iterators of different blocks!");
-    return Idx - RHS.Idx;
-  }
-
-  inline Self &operator+=(int RHS) {
-    int NewIdx = Idx + RHS;
-    assert(index_is_valid(NewIdx) && "Iterator index out of bound");
-    Idx = NewIdx;
-    return *this;
-  }
-
-  inline Self &operator-=(int RHS) { return operator+=(-RHS); }
-
-  // Specially implement the [] operation using a proxy object to support
-  // assignment.
-  inline SuccessorProxy operator[](int Offset) {
-    Self TmpIt = *this;
-    TmpIt += Offset;
-    return SuccessorProxy(TmpIt);
-  }
-
-  /// Get the source BlockT of this iterator.
-  inline BlockT *getSource() {
-    assert(Inst && "Source not available, if basic block was malformed");
-    return Inst->getParent();
-  }
-};
-
-using succ_iterator = SuccIterator<Instruction, BasicBlock>;
-using const_succ_iterator = SuccIterator<const Instruction, const BasicBlock>;
+using succ_iterator = BasicBlock::succ_iterator;
+using const_succ_iterator = BasicBlock::const_succ_iterator;
 using succ_range = iterator_range<succ_iterator>;
 using const_succ_range = iterator_range<const_succ_iterator>;
 
-inline succ_iterator succ_begin(Instruction *I) { return succ_iterator(I); }
+inline succ_iterator succ_begin(Instruction *I) { return I->succ_begin(); }
 inline const_succ_iterator succ_begin(const Instruction *I) {
-  return const_succ_iterator(I);
+  return I->succ_begin();
 }
-inline succ_iterator succ_end(Instruction *I) { return succ_iterator(I, true); }
+inline succ_iterator succ_end(Instruction *I) { return I->succ_end(); }
 inline const_succ_iterator succ_end(const Instruction *I) {
-  return const_succ_iterator(I, true);
+  return I->succ_end();
 }
 inline bool succ_empty(const Instruction *I) {
   return succ_begin(I) == succ_end(I);
 }
 inline unsigned succ_size(const Instruction *I) {
   return std::distance(succ_begin(I), succ_end(I));
 }
 inline succ_range successors(Instruction *I) {
   return succ_range(succ_begin(I), succ_end(I));
 }
 inline const_succ_range successors(const Instruction *I) {
   return const_succ_range(succ_begin(I), succ_end(I));
 }
 
-inline succ_iterator succ_begin(BasicBlock *BB) {
-  return succ_iterator(BB->getTerminator());
-}
+inline succ_iterator succ_begin(BasicBlock *BB) { return BB->succ_begin(); }
 inline const_succ_iterator succ_begin(const BasicBlock *BB) {
-  return const_succ_iterator(BB->getTerminator());
-}
-inline succ_iterator succ_end(BasicBlock *BB) {
-  return succ_iterator(BB->getTerminator(), true);
+  return BB->succ_begin();
 }
+inline succ_iterator succ_end(BasicBlock *BB) { return BB->succ_end(); }
 inline const_succ_iterator succ_end(const BasicBlock *BB) {
-  return const_succ_iterator(BB->getTerminator(), true);
+  return BB->succ_end();
 }
 inline bool succ_empty(const BasicBlock *BB) {
   return succ_begin(BB) == succ_end(BB);
 }
 inline unsigned succ_size(const BasicBlock *BB) {
   return std::distance(succ_begin(BB), succ_end(BB));
 }
 inline succ_range successors(BasicBlock *BB) {

llvm/include/llvm/IR/Instruction.h

 #ifndef LLVM_IR_INSTRUCTION_H
 #define LLVM_IR_INSTRUCTION_H
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/ilist_node.h"
 #include "llvm/IR/DebugLoc.h"
+#include "llvm/IR/IteratorsHelper.h"
 #include "llvm/IR/SymbolTableListTraits.h"
 #include "llvm/IR/User.h"
 #include "llvm/IR/Value.h"
 #include "llvm/Support/Casting.h"
 #include <algorithm>
 #include <cassert>
 #include <cstdint>
 #include <utility>

 
 protected:
   ~Instruction(); // Use deleteValue() to delete a generic Instruction.
 
 public:
   Instruction(const Instruction &) = delete;
   Instruction &operator=(const Instruction &) = delete;
 
+  /// Successor iterators.
+  using succ_iterator = SuccIterator<Instruction, BasicBlock>;
+  using const_succ_iterator = SuccIterator<const Instruction, const BasicBlock>;
+  using succ_range = iterator_range<succ_iterator>;
+  using const_succ_range = iterator_range<const_succ_iterator>;
+
+  succ_iterator succ_begin() { return succ_iterator(this); }
+  const_succ_iterator succ_begin() const { return const_succ_iterator(this); }
+  succ_iterator succ_end() { return succ_iterator(this, true); }
+  const_succ_iterator succ_end() const {
+    return const_succ_iterator(this, true);
+  }
+  bool succ_empty() const { return succ_begin() == succ_end(); }
+  unsigned succ_size() const { return std::distance(succ_begin(), succ_end()); }
+  succ_range successors() { return succ_range(succ_begin(), succ_end()); }
+  const_succ_range successors() const {
+    return const_succ_range(succ_begin(), succ_end());
+  }
+
   /// Specialize the methods defined in Value, as we know that an instruction
   /// can only be used by other instructions.
   Instruction       *user_back()       { return cast<Instruction>(*user_begin());}
   const Instruction *user_back() const { return cast<Instruction>(*user_begin());}
 
   inline const BasicBlock *getParent() const { return Parent; }
   inline       BasicBlock *getParent()       { return Parent; }
 

llvm/include/llvm/IR/IteratorsHelper.h

+//===- IteratorsHelper.h ---------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+/// \file
+///
+/// This file provides generic facilities for iterating successors and
+/// predecessors of basic blocks, the successors of specific terminator
+/// instructions, etc.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_IR_ITERATORSHELPER_H
+#define LLVM_IR_ITERATORSHELPER_H
+
+#include "llvm/ADT/iterator.h"
+#include "llvm/ADT/iterator_range.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/type_traits.h"
+#include <cassert>
+#include <cstddef>
+#include <iterator>
+
+namespace llvm {
+
+//===----------------------------------------------------------------------===//
+// BasicBlock pred_iterator definition
+//===----------------------------------------------------------------------===//
+
+template <class Ptr, class USE_iterator> // Predecessor Iterator
+class PredIterator : public std::iterator<std::forward_iterator_tag, Ptr,
+                                          ptrdiff_t, Ptr *, Ptr *> {
+  using super =
+      std::iterator<std::forward_iterator_tag, Ptr, ptrdiff_t, Ptr *, Ptr *>;
+  using Self = PredIterator<Ptr, USE_iterator>;
+  USE_iterator It;
+
+  inline void advancePastNonTerminators() {
+    // Loop to ignore non-terminator uses (for example BlockAddresses).
+    while (!It.atEnd()) {
+      if (auto *Inst = dyn_cast<Instruction>(*It))
+        if (Inst->isTerminator())
+          break;
+
+      ++It;
+    }
+  }
+
+public:
+  using pointer = typename super::pointer;
+  using reference = typename super::reference;
+
+  PredIterator() = default;
+  explicit inline PredIterator(Ptr *bb) : It(bb->user_begin()) {
+    advancePastNonTerminators();
+  }
+  inline PredIterator(Ptr *bb, bool) : It(bb->user_end()) {}
+
+  inline bool operator==(const Self &x) const { return It == x.It; }
+  inline bool operator!=(const Self &x) const { return !operator==(x); }
+
+  inline reference operator*() const {
+    assert(!It.atEnd() && "pred_iterator out of range!");
+    return cast<Instruction>(*It)->getParent();
+  }
+  inline pointer *operator->() const { return &operator*(); }
+
+  inline Self &operator++() { // Preincrement
+    assert(!It.atEnd() && "pred_iterator out of range!");
+    ++It;
+    advancePastNonTerminators();
+    return *this;
+  }
+
+  inline Self operator++(int) { // Postincrement
+    Self tmp = *this;
+    ++*this;
+    return tmp;
+  }
+
+  /// getOperandNo - Return the operand number in the predecessor's
+  /// terminator of the successor.
+  unsigned getOperandNo() const { return It.getOperandNo(); }
+
+  /// getUse - Return the operand Use in the predecessor's terminator
+  /// of the successor.
+  Use &getUse() const { return It.getUse(); }
+};
+
+//===----------------------------------------------------------------------===//
+// Instruction and BasicBlock succ_iterator helpers
+//===----------------------------------------------------------------------===//
+
+template <class InstructionT, class BlockT>
+class SuccIterator
+    : public iterator_facade_base<SuccIterator<InstructionT, BlockT>,
+                                  std::random_access_iterator_tag, BlockT, int,
+                                  BlockT *, BlockT *> {
+public:
+  using difference_type = int;
+  using pointer = BlockT *;
+  using reference = BlockT *;
+
+private:
+  InstructionT *Inst;
+  int Idx;
+  using Self = SuccIterator<InstructionT, BlockT>;
+
+  inline bool index_is_valid(int Idx) {
+    // Note that we specially support the index of zero being valid even in the
+    // face of a null instruction.
+    return Idx >= 0 && (Idx == 0 || Idx <= (int)Inst->getNumSuccessors());
+  }
+
+  /// Proxy object to allow write access in operator[]
+  class SuccessorProxy {
+    Self It;
+
+  public:
+    explicit SuccessorProxy(const Self &It) : It(It) {}
+
+    SuccessorProxy(const SuccessorProxy &) = default;
+
+    SuccessorProxy &operator=(SuccessorProxy RHS) {
+      *this = reference(RHS);
+      return *this;
+    }
+
+    SuccessorProxy &operator=(reference RHS) {
+      It.Inst->setSuccessor(It.Idx, RHS);
+      return *this;
+    }
+
+    operator reference() const { return *It; }
+  };
+
+public:
+  // begin iterator
+  explicit inline SuccIterator(InstructionT *Inst) : Inst(Inst), Idx(0) {}
+  // end iterator
+  inline SuccIterator(InstructionT *Inst, bool) : Inst(Inst) {
+    if (Inst)
+      Idx = Inst->getNumSuccessors();
+    else
+      // Inst == NULL happens, if a basic block is not fully constructed and
+      // consequently getTerminator() returns NULL. In this case we construct
+      // a SuccIterator which describes a basic block that has zero
+      // successors.
+      // Defining SuccIterator for incomplete and malformed CFGs is especially
+      // useful for debugging.
+      Idx = 0;
+  }
+
+  /// This is used to interface between code that wants to
+  /// operate on terminator instructions directly.
+  int getSuccessorIndex() const { return Idx; }
+
+  inline bool operator==(const Self &x) const { return Idx == x.Idx; }
+
+  inline BlockT *operator*() const { return Inst->getSuccessor(Idx); }
+
+  // We use the basic block pointer directly for operator->.
+  inline BlockT *operator->() const { return operator*(); }
+
+  inline bool operator<(const Self &RHS) const {
+    assert(Inst == RHS.Inst && "Cannot compare iterators of different blocks!");
+    return Idx < RHS.Idx;
+  }
+
+  int operator-(const Self &RHS) const {
+    assert(Inst == RHS.Inst && "Cannot compare iterators of different blocks!");
+    return Idx - RHS.Idx;
+  }
+
+  inline Self &operator+=(int RHS) {
+    int NewIdx = Idx + RHS;
+    assert(index_is_valid(NewIdx) && "Iterator index out of bound");
+    Idx = NewIdx;
+    return *this;
+  }
+
+  inline Self &operator-=(int RHS) { return operator+=(-RHS); }
+
+  // Specially implement the [] operation using a proxy object to support
+  // assignment.
+  inline SuccessorProxy operator[](int Offset) {
+    Self TmpIt = *this;
+    TmpIt += Offset;
+    return SuccessorProxy(TmpIt);
+  }
+
+  /// Get the source BlockT of this iterator.
+  inline BlockT *getSource() {
+    assert(Inst && "Source not available, if basic block was malformed");
+    return Inst->getParent();
+  }
+};
+} // end namespace llvm
+
+#endif // LLVM_IR_ITERATORSHELPER_H

llvm/lib/IR/BasicBlock.cpp

 void BasicBlock::dropAllReferences() {
   for (Instruction &I : *this)
     I.dropAllReferences();
 }
 
 /// If this basic block has a single predecessor block,
 /// return the block, otherwise return a null pointer.
 const BasicBlock *BasicBlock::getSinglePredecessor() const {
-  const_pred_iterator PI = pred_begin(this), E = pred_end(this);
+  const_pred_iterator PI = pred_begin(), E = pred_end();
   if (PI == E) return nullptr;         // No preds.
   const BasicBlock *ThePred = *PI;
   ++PI;
   return (PI == E) ? ThePred : nullptr /*multiple preds*/;
 }
 
 /// If this basic block has a unique predecessor block,
 /// return the block, otherwise return a null pointer.
 /// Note that unique predecessor doesn't mean single edge, there can be
 /// multiple edges from the unique predecessor to this block (for example
 /// a switch statement with multiple cases having the same destination).
 const BasicBlock *BasicBlock::getUniquePredecessor() const {
-  const_pred_iterator PI = pred_begin(this), E = pred_end(this);
+  const_pred_iterator PI = pred_begin(), E = pred_end();
   if (PI == E) return nullptr; // No preds.
   const BasicBlock *PredBB = *PI;
   ++PI;
   for (;PI != E; ++PI) {
     if (*PI != PredBB)
       return nullptr;
     // The same predecessor appears multiple times in the predecessor list.
     // This is OK.
   }
   return PredBB;
 }
 
 bool BasicBlock::hasNPredecessors(unsigned N) const {
-  return hasNItems(pred_begin(this), pred_end(this), N);
+  return hasNItems(pred_begin(), pred_end(), N);
 }
 
 bool BasicBlock::hasNPredecessorsOrMore(unsigned N) const {
-  return hasNItemsOrMore(pred_begin(this), pred_end(this), N);
+  return hasNItemsOrMore(pred_begin(), pred_end(), N);
 }
 
 const BasicBlock *BasicBlock::getSingleSuccessor() const {
-  const_succ_iterator SI = succ_begin(this), E = succ_end(this);
+  const_succ_iterator SI = succ_begin(), E = succ_end();
   if (SI == E) return nullptr; // no successors
   const BasicBlock *TheSucc = *SI;
   ++SI;
   return (SI == E) ? TheSucc : nullptr /* multiple successors */;
 }
 
 const BasicBlock *BasicBlock::getUniqueSuccessor() const {
-  const_succ_iterator SI = succ_begin(this), E = succ_end(this);
+  const_succ_iterator SI = succ_begin(), E = succ_end();
   if (SI == E) return nullptr; // No successors
   const BasicBlock *SuccBB = *SI;
   ++SI;
   for (;SI != E; ++SI) {
     if (*SI != SuccBB)
       return nullptr;
     // The same successor appears multiple times in the successor list.
     // This is OK.

 /// This method is used to notify a BasicBlock that the
 /// specified Predecessor of the block is no longer able to reach it.  This is
 /// actually not used to update the Predecessor list, but is actually used to
 /// update the PHI nodes that reside in the block.  Note that this should be
 /// called while the predecessor still refers to this block.
 ///
 void BasicBlock::removePredecessor(BasicBlock *Pred,
                                    bool KeepOneInputPHIs) {
-  assert((hasNUsesOrMore(16)||// Reduce cost of this assertion for complex CFGs.
-          find(pred_begin(this), pred_end(this), Pred) != pred_end(this)) &&
-         "removePredecessor: BB is not a predecessor!");
+  assert(
+      (hasNUsesOrMore(16) || // Reduce cost of this assertion for complex CFGs.
+       find(pred_begin(), pred_end(), Pred) != pred_end()) &&
 
   if (InstList.empty()) return;
   PHINode *APN = dyn_cast<PHINode>(&front());
   if (!APN) return;   // Quick exit.
 
   // If there are exactly two predecessors, then we want to nuke the PHI nodes
   // altogether.  However, we cannot do this, if this in this case:
   //

 
 void BasicBlock::replaceSuccessorsPhiUsesWith(BasicBlock *Old,
                                               BasicBlock *New) {
   Instruction *TI = getTerminator();
   if (!TI)
     // Cope with being called on a BasicBlock that doesn't have a terminator
     // yet. Clang's CodeGenFunction::EmitReturnBlock() likes to do this.
     return;
-  llvm::for_each(successors(TI), [Old, New](BasicBlock *Succ) {
+  llvm::for_each(TI->successors(), [Old, New](BasicBlock *Succ) {
     Succ->replacePhiUsesWith(Old, New);
   });
 }
 
 void BasicBlock::replaceSuccessorsPhiUsesWith(BasicBlock *New) {
   this->replaceSuccessorsPhiUsesWith(this, New);
 }