[llvm-dev] How to get the address of a global variable in LLVM?
Dipanjan Das via llvm-dev
llvm-dev at lists.llvm.org
Fri Apr 28 14:20:40 PDT 2017
Let `x` be the address of a global variable `g` in a program at run-time.
LLVM IR produces a store instruction as shown below:
store i32 30, i32* @g, align 4
I am writing an LLVM pass which will instrument the program such that `x`
is passed to an instrumentation function `func(int addr)` at run-time. I
can insert a call to `func` using `IRBuilder` successfully. What I am not
being able to do is to insert instrumentation to collect `x`.
if (StoreInst *store_inst = dyn_cast<StoreInst>(&I)) {
Value* po = store_inst->getPointerOperand();
if(isa<GlobalVariable>(po)) {
errs() << "store [pointer]: " << *po << '\n';
Constant *instrument_func =
F.getParent()->getOrInsertFunction("func", Type::getVoidTy(Ctx),
Type::getInt32Ty(Ctx), NULL);
IRBuilder<> builder(&I);
builder.SetInsertPoint(&B,
++builder.GetInsertPoint());
Value* args[] = {po};
builder.CreateCall(instrument_func, args);
}
}
The result of running `opt` is :
Call parameter type does not match function signature!
i32* @a
i32 call void bitcast (void (i64)* @func to void (i32)*)(i32* @a)
LLVM ERROR: Broken function found, compilation aborted!
--
Thanks & Regards,
Dipanjan
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