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fbusato merged 3 commits into from
Feb 27, 2025
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Improve <cuda/std/bit> documentation #3959

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improve bit documentation
fbusato Feb 21, 2025
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fbusato Feb 27, 2025
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fbusato Feb 27, 2025
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@fbusato
fbusato committed Feb 27, 2025
commit f00ed427acc34245f3b4bdc7b4a94ec075ff0ad7
9 changes: 5 additions & 4 deletions docs/libcudacxx/standard_api/numerics_library/bit.rst
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@@ -1,14 +1,15 @@
.. _libcudacxx-standard-api-numerics-bit:

``<cuda/std/bit>``
======================
==================

CUDA Performance Considerations
-------------------------------

- ``bit_width()`` translates into a single ``FLO`` SASS instruction. The result is assumed to be in the range ``[0, N-bit]``.
- ``bit_ceil()`` translates into ``FLO, SHL`` SASS instructions. The result is assumed to be greater than or equal to the input.
- ``bit_floor()`` translates into ``ADD, FLO, SHL, IMINMAX`` SASS instructions. The result is assumed to be less than or equal to the input.
- ``bit_ceil()`` translates into ``ADD, FLO, SHL, IMINMAX`` SASS instructions. The result is assumed to be greater than or equal to the input.
- ``bit_floor()`` translates into ``FLO, SHL`` SASS instructions. The result is assumed to be less than or equal to the input.
- ``byteswap()`` translates into a single ``PRMT`` SASS instruction.
- ``popcount()`` translates into a single ``POPC`` SASS instruction. The result is assumed to be in the range ``[0, N-bit]``.
- ``has_single_bit()`` translates into ``POPC + ISETP`` SASS instructions.
- ``rotl()/rotr()`` translate into a single ``SHF`` (funned shift) SASS instruction.
Expand All @@ -21,5 +22,5 @@ Additional Notes
----------------

- All functions are marked ``[[nodiscard]]`` and ``noexcept``
- All functions support ``__uint128_t``
- All functions support 128-bit integer types
- ``bit_ceil()`` checks for overflow in debug mode
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