topic Calling function from kernel scope. SYCL_EXTERNAL in Intel® oneAPI DPC++/C++ Compiler

Calling function from kernel scope. SYCL_EXTERNAL

Xeenych — Wed, 16 Feb 2022 22:27:41 GMT

I have my_func.cpp/.hpp with some fuction

/* my_func.hpp */ void my_func(); /* my_func.cpp */ void my_func() { // do some stuff // call some other funcs }

In my main.cpp I wrote a simple kernel, which just calls my_func()

When compiling it with VS2022 compiler says, that my_func() should have SYCL_EXTERNAL attribute?

How do i get over this error?

Re: Calling function from kernel scope. SYCL_EXTERNAL

NoorjahanSk_Intel — Thu, 17 Feb 2022 11:10:34 GMT

Hi,

Thanks for reaching out to us.

>>How do i get over this error?

SYCL_EXTERNAL is an optional macro that enables external linkage of SYCL functions and methods to be included in an SYCL kernel.

If we want to call a function from a kernel, that function(in our case void my_func()) should be preceded with SYCL_EXTERNAL in the header file, then you can get rid of this compiler error.

We have tried the following code with dpc++ version 2022.0.0 and it worked for us.

Please find the below code snippets.

Header.h

#pragma once #include<CL/sycl.hpp> extern SYCL_EXTERNAL void my_func();

my_fun.cpp

#include <CL/sycl.hpp> #include "Header.h" void my_func() { }

main.cpp

#include <CL/sycl.hpp> #include <iostream> #include "Header.h" #define numElements 10 using namespace std; int main(void) { cl::sycl::queue queue(cl::sycl::host_selector{}); std::cout << "Running on " << queue.get_device().get_info<cl::sycl::info::device::name>() << "\n"; { queue.submit( [&](cl::sycl::handler& cgh) { cgh.parallel_for<class vectorAdd_e83213>( cl::sycl::range<1>{numElements}, [=](cl::sycl::item<1> item_ct1) { my_func(); }); }); } queue.wait(); return 0; }

If this resolves your issue, make sure to accept this as a solution. This would help others with a similar issue.

If your issue still persists, please do let us know which oneAPI version is being used.

Thanks & Regards,

Noorjahan

Re: Calling function from kernel scope. SYCL_EXTERNAL

Xeenych — Thu, 17 Feb 2022 11:12:17 GMT

Ok, this works, but:

my_func() calls tons of other functions.

I have to add SYCL_EXTERNAL to every declaration in .hpp and every definition in.cpp of all functions in a call-tree of my_func()

This introduces a dependancy on DPC++ headers in my_func() and other sources

I could have written something like this for every function in a call-tree of my_func().

#if defined __INTEL_LLVM_COMPILER && SYCL_LANGUAGE_VERISON #include <CL/sycl.hpp> #else #define SYCL_EXTERNAL #endif SYCL_EXTERNAL void my_func();

Is there a way to avoid this?

Is there a linker script or some command-line arguments for compiler to list functions to be included in SYCL kernel without specifying SYCL_EXTERNAL?

I thought, that intel compiler is advanced enough to determine functions to be included in kernel and link them accordingly.

Re: Calling function from kernel scope. SYCL_EXTERNAL

NoorjahanSk_Intel — Thu, 10 Mar 2022 09:27:47 GMT

Hi,

>>Is there a linker script or some command-line arguments for compiler to list functions to be included in SYCL kernel without specifying SYCL_EXTERNAL?

Sorry for causing any inconvenience, there is no such script or command-line argument to list the functions.

As of now, we need to use macro definitions to add SYCL_EXTERNAL for every function as you have mentioned in the earlier post.

Thanks & Regards,

Noorjahan.

Re:Calling function from kernel scope. SYCL_EXTERNAL

NoorjahanSk_Intel — Fri, 04 Mar 2022 09:56:58 GMT

Hi,

Could you please provide an update on your issue?

If the information provided above helped, Could you also please confirm whether can we close this issue from our end.

Thanks & Regards,

Noorjahan.

Re: Calling function from kernel scope. SYCL_EXTERNAL

Xeenych — Fri, 04 Mar 2022 10:51:43 GMT

Yes, this helped. You can close the issue.

P.S.

Looks like my account was banned for several days, but now it works.

Re:Calling function from kernel scope. SYCL_EXTERNAL

NoorjahanSk_Intel — Fri, 04 Mar 2022 11:49:49 GMT

Hi,

Thanks for the confirmation!

As this issue has been resolved, we will no longer respond to this thread. If you need any additional information, please submit a new question as this thread will no longer be monitored.

Thanks & Regards,

Noorjahan.