Value* to Instruction*/LoadInst* casting [closed]

问题

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Closed 6 years ago.

Can you please tell me if it is possible in LLVM to cast a Value* to an Instruction*/LoadInst* if for example isa<LoadInst>(MyValue) is true? In my particular piece of code:

Value* V1 = icmpInstrArray[i]->getOperand(0);
Value* V2 = icmpInstrArray[i]->getOperand(1);
if (isa<LoadInst>(V1) || isa<LoadInst>(V2)){
...
if(isa<LoadInst>(icmpInstrArray[i]->getOperand(0)))
    LoadInst *LD100 = cast<LoadInst>(icmpInstrArray[i]->getOperand(0));
        Value *C100 = LD100->getPointerOperand(); //HERE COMPILATION ERROR

Further, I just need to make C100->getName() and I will get the loaded variable.

The compilation error is : error: ‘LD100’ was not declared in this scope.

I don't think that I can use cast like that. Can you tell me a method to obtain the loaded variable from a Load instruction correspondent to my ICMP instructions? Or better how I can extract the Load instruction from icmpInstrArray[i]->getOperand(0)?

回答1:

You are missing the braces around the if-statement. Your code is currently equal to this:

if(isa<LoadInst>(icmpInstrArray[i]->getOperand(0))) {
    LoadInst *LD100 = cast<LoadInst>(icmpInstrArray[i]->getOperand(0));
}
Value *C100 = LD100->getPointerOperand(); //HERE COMPILATION ERROR

LD100 is not defined outside the if-statements scope. This would work:

if(isa<LoadInst>(icmpInstrArray[i]->getOperand(0))) {
    LoadInst *LD100 = cast<LoadInst>(icmpInstrArray[i]->getOperand(0));
    Value *C100 = LD100->getPointerOperand(); //HERE COMPILATION ERROR
}

来源：https://stackoverflow.com/questions/14560027/value-to-instruction-loadinst-casting