How should LLVM Function clones be cleaned up? - llvm

Question

I have an LLVM pass that traverses input IR code and performs analysis on called functions. My analysis function signature is functionTracer(const Function* pFunc) and I call it on a CallInst's getCalledFunction().
At the start of my analysis function I create a copy of the passed in function that I manipulate during the analysis:
Function* pFunctionToAnalyze = CloneFunction(pFunction,VMap,false);
I have a C++ main that calls a function f2(int i):
int main(){
int a = 3;
int b = f2(a);
int c = f2(b);
}
I turn this code into IR and submit to my pass. My code appears to execute and perform the manipulations I want but I get the following error output:
While deleting: i32 (i32)* %_Z2f2i
Use still stuck around after Def is destroyed: %call1 = call i32 #_Z2f2i(i32 %1)
Use still stuck around after Def is destroyed: %call = call i32 #_Z2f2i(i32 %0)
module: /home/src/extern/llvm/llvm-3.7.0.src/lib/IR/Value.cpp:82:
virtual llvm::Value::~Value(): Assertion `use_empty() && "Uses remain when a value is destroyed!"' failed.
Aborted (core dumped)
Do I need to perform manual clean up of the Cloned function, pFunctionToAnalyze, at the end of my analysis function to remove Uses before returning? Is there a better way to copy function contents for analysis that may modify it?

Answer 1

There's an example on that in lib/Transforms/IPO/PartialInlining.cpp
// Clone the function, so that we can hack away on it.
ValueToValueMapTy VMap;
Function* duplicateFunction = CloneFunction(F, VMap,
/*ModuleLevelChanges=*/false);
And in the end of the pass:
duplicateFunction->replaceAllUsesWith(F);
duplicateFunction->eraseFromParent();
Isn't that what fixes your problem?