[llvm-dev] Inserting a function with arguments to appendToGlobalCtors

[Mohannad Ismail via llvm-dev]

Thank you for your reply.

I was able to create a function and append the call instructions to those
functions-taking-arguments to it with IRBuilder. Then I added it to the
global constructors and it worked! Thank you!

On Mon, Dec 21, 2020 at 9:53 PM David Blaikie <dblaikie at gmail.com> wrote:

>
>
> On Mon, Dec 21, 2020 at 6:16 PM Mohannad Ismail <imohannad at vt.edu> wrote:
>
>> Hi David,
>>
>> Thank you for your fast reply.
>>
>> That's a good idea. But the arguments I need are obtained from the IR, or
>> in more accurately, from the static analysis I do on the IR. I can't
>> get these arguments externally. Are you proposing I create the function
>> within the pass? How do I do that?
>>
>
> If it's necessary to create the pass you want to, yeah, you could
> introduce a function within the transformation pass. (I guess it'd have to
> be a module pass, if it adds a function - I'm not 100% sure on that). Same
> way you create an IR function at any point - I guess
> IRBuilder::createFunction or something like that.
>
>
>>
>> On Mon, Dec 21, 2020 at 8:40 PM David Blaikie <dblaikie at gmail.com> wrote:
>>
>>> You probably need to create a function that takes no arguments - and
>>> have that function then create the arguments and call the
>>> functions-taking-arguments you want to run as global ctors. Add the outer
>>> no-argument-taking-function to the global ctors list.
>>>
>>> On Mon, Dec 21, 2020 at 5:28 PM Mohannad Ismail via llvm-dev <
>>> llvm-dev at lists.llvm.org> wrote:
>>>
>>>> I want to insert a function call that executes first. I figured the way
>>>> to do this is to insert to the global constructors with
>>>> appendToGlobalCtors() in this way:
>>>>
>>>> LLVMContext &C = M.getContext();
>>>> Function* FInit = Function::Create(FunctionType::get(Type::getVoidTy(C), false), GlobalValue::ExternalLinkage, INITMEMORY, &M);
>>>> appendToGlobalCtors(M, FInit, 0);
>>>>
>>>> This works well if the function has no arguments. But what if the
>>>> function I need to insert has arguments that I would like to specify? How
>>>> do I create the function to insert into the global constructors? The
>>>> function I have returns void. I already know how to use the IRBuilder to
>>>> create a function call. But the builder takes the arguments in the
>>>> builder.CreateCall(Func, FuncArgs). In general, I need to execute a bunch
>>>> of function calls first when I am able to obtain their parameters in the
>>>> program.
>>>>
>>>> Hope I was clear enough. Let me know if this needs more clarification.
>>>> Thanks!
>>>>
>>>>
>>>> Best regards,
>>>>
>>>> Mohannad Ismail
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> llvm-dev at lists.llvm.org
>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>
>>>
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