[Openmp-commits] [PATCH] D70971: [libomptarget] Build a minimal deviceRTL for amdgcn

[Jon Chesterfield via Phabricator via Openmp-commits]

JonChesterfield marked an inline comment as done.
JonChesterfield added inline comments.


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Comment at: openmp/libomptarget/deviceRTLs/amdgcn/src/device_environment.h:18-26
+struct omptarget_device_environmentTy {
+  int32_t debug_level;   // gets value of envvar LIBOMPTARGET_DEVICE_RTL_DEBUG
+                         // only useful for Debug build of deviceRTLs 
+  int32_t num_devices;   // gets number of active offload devices 
+  int32_t device_num;    // gets a value 0 to num_devices-1
+};
+
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ABataev wrote:
> JonChesterfield wrote:
> > ABataev wrote:
> > > JonChesterfield wrote:
> > > > ABataev wrote:
> > > > > JonChesterfield wrote:
> > > > > > ABataev wrote:
> > > > > > > JonChesterfield wrote:
> > > > > > > > ABataev wrote:
> > > > > > > > > Agan this thing. Can we make it common if it is really required? Again, why do we need these new fields? Could you remove it from the current patch?
> > > > > > > > It's different on nvptx and amdgcn, so not a great candidate for common. The extra fields are used to implement a couple of functions that are stubs in trunk which you weren't sure are necessary for nvptx.
> > > > > > > Maybe, it is better to exclude this from this patch? Maybe it would be good to have these fields for nvptx too or we don't need them to for amdgcn. Could you remind where we discussed this structure?
> > > > > > Discussion was in D69424. I could drop the file from this patch, but it's included by debug.h so that'll break the amdgcn build
> > > > > Ah, found it. Again, the same question. These fields are required to add 2 new `omp_...` functions. The question is the same. Are they required by the standard? If yes, we must have the same fields for nvptx. Otherwise, I don't think we need these fields at all.
> > > > "When called from a target region the effect of this routing is unspecified"
> > > > 
> > > > So nvptx returning zero is fine, and andgcn returning a meaningful value is also fine, as far as the standard is concerned.
> > > Why do we need to store these values? And if we want these functions to return some meaningful values, better to implement the same behavior for both nvptx and amdgcn.
> > The plugin knows how many devices are available, so it writes the values to memory on the device, such that the device can answer the query accurately. I want the function to return a meaningful value on amdgcn as a quality of implementation point - it doesn't directly affect me whether nvptx supports the same. It'll cost a few bytes of memory, in difficult to optimise out fashion.
> WE need to support the same behavior on all platforms.
Who is we in this context, and do you consider unconditionally returning zero everywhere to be better than returning meaningful values on some targets and zero on others?


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https://reviews.llvm.org/D70971