[LLVMdev] How to const char* Value for function argument

[Dmitry N. Mikushin]

Thank you, James!

2011/9/22 James Molloy <James.Molloy at arm.com>:
> Hi Dimitry,
>
> This makes sense if you think about it from the perspective that the string you want passing must be passed at runtime, and so can't use a const char * from compile time.
>
> You need to make the string visible in the compiled image, and use that as the argument. A string is an array of 8-bit integers, so you need to create a ConstantArray.
>
> Value *v = ConstantArray::get(Context, callee->getName(), /*AddNull=*/true);
>
> Cheers,
>
> James
>
> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Dmitry N. Mikushin
> Sent: 22 September 2011 11:06
> To: LLVM-Dev
> Subject: [LLVMdev] How to const char* Value for function argument
>
> Hi,
>
> I'm trying to replace function call with call to
> wrapper(function_name, num_args, ...), where varargs hold args of
> original call.
>
>        Function* launch = Function::Create(
>                TypeBuilder<int(const char*, int, ...), false>::get(context),
>                GlobalValue::ExternalLinkage, "kernelgen_launch_", m2);
>
>                                {
>                                        CallInst* call = dyn_cast<CallInst>(cast<Value>(I));
>                                        if (!call) continue;
>                                        Function* callee = call->getCalledFunction();
>                                        if (!callee && !callee->isDeclaration()) continue;
>                                        if (callee->getName() != func2.getName()) continue;
>
>                                        SmallVector<Value*, 16> callargs(call->op_begin(), call->op_end());
>                                        callargs.insert(callargs.begin(),
>                                                ConstantInt::get(Type::getInt32Ty(context),
>                                                        call->getNumArgOperands()));
>                                        callargs.insert(callargs.begin(), callee->getName());
>                                        CallInst* newcall = CallInst::Create(launch, callargs, "", call);
>                                        newcall->takeName(call);
>                                        newcall->setCallingConv(call->getCallingConv());
>                                        newcall->setAttributes(call->getAttributes());
>                                        newcall->setDebugLoc(call->getDebugLoc());
>                                        call->replaceAllUsesWith(newcall);
>
>                                        found = true;
>                                        break;
>                                }
>
> The line callargs.insert(callargs.begin(), callee->getName()); is
> invalid: instead of StringRef I need to supply a Value* for the second
> argument. How to construct value for const char* ?
>
> Thanks,
> - D.
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