Function LLVMGetPrologueData 

pub unsafe extern "C" fn LLVMGetPrologueData(
    Fn: LLVMValueRef,
) -> LLVMValueRef

Gets the prologue data associated with a function. Only valid on functions, and only if LLVMHasPrologueData returns true. See https://llvm.org/docs/LangRef.html#prologue-data