[all-commits] [llvm/llvm-project] dc4335: [libc] Perform bitfield zero initialization wave-p...

[Joseph Huber via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: dc4335a2bf75c7b9928a72a7f15df0276120d7ed
      https://github.com/llvm/llvm-project/commit/dc4335a2bf75c7b9928a72a7f15df0276120d7ed
  Author: Joseph Huber <huberjn at outlook.com>
  Date:   2025-06-11 (Wed, 11 Jun 2025)

  Changed paths:
    M libc/src/__support/GPU/allocator.cpp

  Log Message:
  -----------
  [libc] Perform bitfield zero initialization wave-parallel (#143607)

Summary:
We need to set the bitfield memory to zero because the system does not
guarantee zeroed out memory. Even if fresh pages are zero, the system
allows re-use so we would need a `kfd` level API to skip this step.

Because we can't this patch updates the logic to perform the zero
initialization wave-parallel. This reduces the amount of time it takes
to allocate a fresh by up to a tenth.

This has the unfortunate side effect that the control flow is more
convoluted and we waste some extra registers, but it's worth it to
reduce the slab allocation latency.



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