Horton

refactor architecture-specific popcount code

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: pgsql-hackers@postgresql.org
Date: 2026-01-14T20:40:02Z
Lists: pgsql-hackers

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Right now, the organization of this code is weird.  All AArch64-specific
implementations live in an AArch64-specific file, the AVX-512
implementations live in their own file, and the architecture-agnostic and
SSE4.2 implementations live in pg_bitutils.c.  The attached patches move
the SSE4.2 implementations to the AVX-512 file (which is renamed
appropriately), and they update some function names to be more descriptive,
i.e., "fast" is replaced with "sse42" and "slow" is replaced with
"generic".

I probably should've done this a while ago...

-- 
nathan

Commits

  1. Make use of pg_popcount() in more places.

  2. Remove uses of popcount builtins.

  3. Remove some unnecessary optimizations in popcount code.

  4. Remove specialized word-length popcount implementations.

  5. Move x86-64-specific popcount code to pg_popcount_x86.c.

  6. Refactor some SIMD and popcount macros.

  7. Rename "fast" and "slow" popcount functions.

  8. Rename pg_popcount_avx512.c to pg_popcount_x86.c.

  9. Remove trailing zero words from Bitmapsets

  10. Don't use _BitScanForward64/_BitScanReverse64 on 32-bit MSVC builds