ABataev added inline comments.
================
Comment at: openmp/libomptarget/deviceRTLs/nvptx/src/omptarget-nvptx.h:73
+/// Note: Only the team master is allowed to call non-const functions!
+struct shared_bytes_buffer {
+
----------------
jdoerfert wrote:
> ABataev wrote:
> > jdoerfert wrote:
> > > > What is this buffer used for? Transferring pointers to the shread
> > > > variables to the parallel regions? If so, it must be handled by the
> > > > compiler. There are several reasons to do this:
> > > > 1) You're using malloc/free functions for large buffers. The fact is
> > > > that the size of this buffer is known at the compile time and compiler
> > > > can generate the fixed size buffer in the global memory if required. We
> > > > already have similar implementation for target regions, globalized
> > > > variables etc. You can take a look and adapt it for your purpose.
> > > > 2) Malloc/free are not very fast on the GPU, so it will get an
> > > > additional performance with the preallocated buffers.
> > > > 3) Another one problem with malloc/free is that they are using
> > > > preallocated memory and the size of this memory is limited by 8Mb (if I
> > > > do recall correctly). This memory is required for the correct support
> > > > of the local variables globalization and we alredy ran into the
> > > > situation when malloc could not allocate enough memory for it with some
> > > > previous implementations.
> > > > 4) You can reused the shared memory buffers already generated by the
> > > > compiler and save shared memory.
> > >
> > > [Quote by ABataev copied from
> > > https://reviews.llvm.org/D59319?id=190767#inline-525900 after the patch
> > > was split.]
> > >
> > >
> > > This buffer is supposed to be used to communicate variables in shared and
> > > firstprivate clauses between threads in a team. In this patch it is
> > > simply used to implement the old `void**` buffer. How, when, if we use it
> > > is part of the interface implementation. For now, this buffer simply
> > > serves the users of the `omptarget_nvptx_globalArgs` global.
> > >
> > > If you want to provide compiler allocated memory to avoid the buffer use,
> > > no problem,
> > > the `__kmpc_target_region_kernel_parallel` function allows to do so, see
> > > the `SharedMemPointers` flag. I wouldn't want to put the logic to
> > > generate these buffers in the front-end though.
> > Why?
> Why what?
Why you don't want to put the buffers generation to the compiler?
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D59424/new/
https://reviews.llvm.org/D59424
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