LLVM中Def-Use获取

Frequently, we might have an instance of the Value Class and we want to determine which Users use the Value. The list of all Users of a particular Value is called a def-use chain.

1. 函数的def-use

Function *F = ...;
 
for (User *U : F->users()) {
  if (Instruction *Inst = dyn_cast(U)) {
    errs() << "F is used in instruction:\n";
    errs() << *Inst << "\n";
  }

或者

Function *F = ...;
for (Value::use_iterator U = F->use_begin(), e = F->use_end(); U != e; ++U) {
  if (Instruction *Inst = dyn_cast(&*(U->getUser()))) {
    errs() << "F is used in instruction:\n";
    errs() << *Inst << "\n";
}

2. 指令的Def-Use

Instruction *A = ...;
 
for (User *U : A->users()) {
  if (Instruction *Inst = dyn_cast(U)) {
    errs() << "A is used in instruction:\n";
    errs() << *Inst << "\n";
  }

或

Instruction *A = ...;
for (Value::use_iterator i = A->use_begin(), e = A->use_end(); i != e; ++i) {
  if (Instruction *U = dyn_cast(&*(i->getUser()))) {
  ...
  }
}