pravinjagtap added a comment. In D153953#4458134 <https://reviews.llvm.org/D153953#4458134>, @sameerds wrote:
> @pravinjagtap @arsenm ... reverting the mbcnt intrinsic affects tests that > were added for atomic optimizations. In particular, the mbcnt is now being > moved across/into/out of control flow because it is no longer convergent. I > eyeballed one example and it seemed okay to me, but a more thorough check > will be useful. Hello @sameerds, The existing logic (before D147408 <https://reviews.llvm.org/D147408>) in atomic optimizer uses `mbcnt(exec)` to setup the control flow to allow only one lane to update the reduced value [Please refer: https://github.com/llvm/llvm-project/blob/80155cbf0be1744953edf68b9729c24bd0de79c4/llvm/lib/Target/AMDGPU/AMDGPUAtomicOptimizer.cpp#L671]. The instructions related to that seems to be moved to other basic block (ComputeEnd). In my opinion it should not affect the logic. @ruiling and @foad can you please confirm this ? While working on D147408 <https://reviews.llvm.org/D147408>, I introduced cttz(exec) [Please refer: https://github.com/llvm/llvm-project/blob/80155cbf0be1744953edf68b9729c24bd0de79c4/llvm/lib/Target/AMDGPU/AMDGPUAtomicOptimizer.cpp#L538C1-L539C72] which is not being affected here. The `EXEC` is being moved to sgpr before the `ComputeLoop` (which we want) and then used it inside the `ComputeLoop` and modified inside it to set up the logic for `ComputeLoop`. This is not being affected because of this change. I could be completely wrong here. Lets see what others have to say. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D153953/new/ https://reviews.llvm.org/D153953 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
