Welcome to LLVM GPU News, a bi-weekly newsletter on all the GPU things under the LLVM umbrella. This issue covers the period from May 21 to June 3 2021.

We welcome your feedback and suggestions. Let us know if we missed anything interesting, or want us to bring attention to your (sub)project, revisions under review, or proposals. Please see the bottom of the page for details on how to submit suggestions and contribute.

Industry News and Conference Talks

LLVM and Clang


  • Sameer Sahasrabuddhe posted an RFC for making function calls convergent by default. On GPU targets, “A convergent operation involves inter-thread communication or synchronization that occurs outside of the memory model, where the set of threads which participate in communication is implicitly affected by control flow”. The RFC proposed to conservatively make calls convergent by default, and to add the noconvergent attribute to indicate that a call is not sensitive to the set of threads executing any dynamic instance of that call. This way, “Frontends are no longer required to add a convergent or noconvergent attribute if all they seek is correct execution on GPUs”.
  • ggllvm is seeking help with OpenCL kernel compilation for AMDGPU on Discourse. The only suggestion so far did not resolve their problem.




  • Thomas Raoux is asking about using the new GPU_MMAMatrix type with Standard ops without having the Standard dialect depend on the GPU dialect. Geoffrey Martin-Noble pointed out that “standard ops only operate on (a subset of) builtin types, but perhaps we could consider turning ShapedType into an interface”.


  • GPU MMA store ops are relaxed to allow chain of MMA ops.
  • SPIR-V dialect starts to see better assembly result names.
  • spv.module now has SingleBlock and NoTerminator traits; spv.endmodule is retired.

OpenMP (Target Offloading)


  • An OpenMP offloading buildbot is available in the LLVM buildbot staging area.
  • OMPD upstreaming continues with discussions: D100181.
  • The patchsets for reworked globalization (D97680 and following) and custom state machines (D101976 and following) are almost ready.
  • AMD are reworking the __shared__ / __local implementation for higher efficiency.
  • Linking of static archives with offload code is being worked on again: D93525.


  • We are replacing libelf with the ELF facilities in LLVM core to cut down on dependencies and work towards offloading on non-Linux platforms: D103545.
  • Multiple refactoring commits to the amdgpu plugin, mainly removing global state (D103600, D103509, …).
  • Various bug fixes: D103642, D103646.

External Compilers