c++ - 如何检查迭代器的相等性？

Question

在我的 llvm 代码中，我尝试使用以下代码检查迭代器 InsertPos 是否指向基本 block 的最后一条指令。

  BasicBlock::iterator InsertPos = BB->begin();
  LLVMContext &Context = BB->getContext();

  while ( !( isa<CallInst>(InsertPos) || 
      ( InsertPos == BB->getTerminator() ) ) ) // <-- Error here
    ++InsertPos;

但是，clang 给了我以下错误。

Basic2.cpp:82:54: error: use of overloaded operator '==' is ambiguous (with operand types 'BasicBlock::iterator' (aka 'ilist_iterator<llvm::Instruction>')
      and 'llvm::TerminatorInst *')
  while ( !( isa<CallInst>(InsertPos) || ( InsertPos == BB->getTerminator() ) ) ) 
                                           ~~~~~~~~~ ^  ~~~~~~~~~~~~~~~~~~~
/home/hmushtaq/llvm/include/llvm/ADT/ilist.h:204:8: note: candidate function
  bool operator==(const ilist_iterator &RHS) const {
       ^
Basic2.cpp:82:54: note: built-in candidate operator==(class llvm::Instruction *, class llvm::Instruction *)
  while ( !( isa<CallInst>(InsertPos) || ( InsertPos == BB->getTerminator() ) ) ) 
                                                     ^
    Basic2.cpp:82:54: note: built-in candidate operator==(restrict class llvm::Instruction    *, restrict class llvm::Instruction *)
    Basic2.cpp:82:54: note: built-in candidate operator==(const restrict class llvm::Instruction *, const restrict class llvm::Instruction *)
    Basic2.cpp:82:54: note: built-in candidate operator==(volatile class llvm::Instruction *, volatile class llvm::Instruction *)
    Basic2.cpp:82:54: note: built-in candidate operator==(const volatile class llvm::Instruction *, const volatile class llvm::Instruction *)
    Basic2.cpp:82:54: note: built-in candidate operator==(volatile restrict class llvm::Instruction *, volatile restrict class llvm::Instruction *)
    Basic2.cpp:82:54: note: built-in candidate operator==(const class llvm::Instruction *, const class llvm::Instruction *)
    Basic2.cpp:82:54: note: built-in candidate operator==(const volatile restrict class llvm::Instruction *, const volatile restrict class llvm::Instruction *)

这样做的正确方法是什么？

Answer 1

BB->getTerminator() 返回一个指针 (TerminatorInst *)，而 InsertPos 是一个迭代器 (BasicBlock::迭代器)。类型不匹配。

也许你可以尝试

&*InsertPos == BB->getTerminator()

---

您还可以使用the isTerminator() method检查指令是否是终止符。 .

InsertPos->isTerminator()