nd_item::barrier has been deprecated

[EikanWang]

As the title, the barrier function of the nd_item class has been deprecated in the SYCL spec 2020. In torch-xpu-ops, we need to replace nd_item::barrier with group_barrier. By the way, we need to check if there is any compile option to expose all the deprecated functions.
https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html#group-barrier

cc @fengyuan14

[dvrogozh]

By the way, we need to check if there is any compile option to expose all the deprecated functions.

I think our problem is that currently warnings are obscured by those coming from the SYCL headers for the features which we did not actually use. The issue is not that compiler does not report such warnings, but that it does so for the stuff we are not interested in. However, this issue is know to DPC++ compiler team and they are working on the fix. Hopefully we will get a new version soon with it. In a meanwhile they also suggested a workaround for the current compiler version. We did need it to go forward with SYCL CPP extension on Windows (pytorch/pytorch#162579). The WA is to add explicit path to SYCL headers with -isystem for GCC or /external:I for MSVC (in host compiler option). This way compiler will treat these paths as system paths and suppress warnings coming from them. I think it still should throw a warning for the cases when we use a deprecated feature in our code - exactly what we need. This needs to be tried though.

[dvrogozh]

Prepared #2096. I don't think I see any warnings from DPC++ compiler for nd_item::barrier. Do you know if they are actually throwing deprecations for this one? and in which version?

[EikanWang]

I have not checked if the DPC++ compiler has marked the API as deprecated. However, the SYCL spec 2020 has removed this API -https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html

[EikanWang]

https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html#nditem-class