gtbercea marked an inline comment as done.
gtbercea added inline comments.
================
Comment at: lib/CodeGen/CGOpenMPRuntime.cpp:5122
+ NewTask = CGF.EmitRuntimeCall(
+ createRuntimeFunction(OMPRTL__kmpc_omp_target_task_alloc), AllocArgs);
+ } else {
----------------
AlexEichenberger wrote:
> gtbercea wrote:
> > ABataev wrote:
> > > gtbercea wrote:
> > > > ABataev wrote:
> > > > > gtbercea wrote:
> > > > > > ABataev wrote:
> > > > > > > gtbercea wrote:
> > > > > > > > ABataev wrote:
> > > > > > > > > Can we use the same function in both modes, with nowait
> > > > > > > > > clause and without?
> > > > > > > > For nowait we need to use the target_task_alloc variant. There
> > > > > > > > are runtimes - other than the open source one - for which this
> > > > > > > > function does something different.
> > > > > > > Trunk relies only to libomptarget interfaces. Why we should take
> > > > > > > into account some other runtime libraries? Plus, what's so
> > > > > > > different for async and non-async versions of the directive?
> > > > > > Async is not yet fully supported in the OpenMP open source runtime
> > > > > > but at some point it will be. This is the first step towards its
> > > > > > support. I'm not sure what your objection is. The difference is
> > > > > > clear. Device ID must be passed on the async version of this call.
> > > > > The difference is not obvious. Why we can't use the same function for
> > > > > sync directives? The fact the it has DeviceId parameter is not an
> > > > > argument here. What's so special from functional point of view?
> > > > When you have multiple device on the same system you have to be able to
> > > > distinguish between then and manage dependencies across these different
> > > > devices. Knowing the device is a crucial first step in handling these
> > > > inter-device dependencies.
> > > Ok, this is why we need it for async version. But why we can't use for
> > > sync version?
> > Based on how the runtime is currently structured, nowait functions are
> > separate from the synchronous ones. See target vs. target_nowait functions
> > and there are many examples like that. The async support is always kept
> > separate from the synchronous support at least in terms of entry points in
> > the runtime.
> Right now, target_task indicates two things: 1) there are depenences to
> offload and 2) it's a nowait constructs. If we use target_task_alloc for both
> situations, we need to distinguish these two cases using flags, because the
> handling iseventually different.
> If we want to explore this avenue, then we have to look into using the proxy
> flag is set to indicates nowait. It may have implications for the tasks on
> the KMP side, so this might be more risky.
> This is why I suggest at the present time that we only generate target task
> for the limited "target task depend nowait"
Thanks a lot for the comment @AlexEichenberger
Repository:
rC Clang
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D63009/new/
https://reviews.llvm.org/D63009
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