)]}'
{
  "commit": "d2d245bc1bba8e3863408cebff484ea90e5cf0a2",
  "tree": "654b5edc15a0023923aaba6873affd99cfd6d6a9",
  "parents": [
    "682c5617b301fc596052bb70ab5f391cb49b5eed"
  ],
  "author": {
    "name": "Evan Brown",
    "email": "ezb@google.com",
    "time": "Mon Oct 05 13:03:25 2026 -0700"
  },
  "committer": {
    "name": "Copybara-Service",
    "email": "copybara-worker@google.com",
    "time": "Mon Oct 05 13:05:51 2026 -0700"
  },
  "message": "Store the swisstable per-table seed in a byte-addressable field.\n\nThe seed for a table\u0027s hashing is packed into `HashtableInlineData::data_` together with the capacity log, size, and other metadata. On the lookup path the compiler has to load the whole word and mask out the seed (`andl $0x7c0`) before it can start hashing, and that masking instruction sits on the critical dependency chain from the table header load to the hash computation and the first control-group load.\n\nGive the seed the whole low byte of `data_` (8 bits instead of 5) and move the capacity log to the next byte. Both are read with byte loads (`movzbl`). This shortens the header-to-hash chain by one cycle when the table pointer load is on the critical path and is neutral for throughput. Hash values for a given seed are unchanged; only the seed encoding and the number of possible per-table seeds change. The size field shrinks from 41 to 37 bits, which still allows ~1.4e11 elements.\n\nReading the fields as bytes matters: a bit-field or a shift-and-mask on the wide word makes clang forward the wide load and re-materialize the masking op, so the seed and capacity accessors go through `unsigned char` loads.\n\nPiperOrigin-RevId: 993854988\nChange-Id: I6e424e26b8f1ce2e706e36f3eb28e85fe041ffa6\n",
  "tree_diff": [
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      "type": "modify",
      "old_id": "fc7cc409f8be710804d8b53e313ea462557cd356",
      "old_mode": 33188,
      "old_path": "absl/container/internal/raw_hash_set.h",
      "new_id": "824f0f4d67ef61781534d42d7c6ab3223966e7c8",
      "new_mode": 33188,
      "new_path": "absl/container/internal/raw_hash_set.h"
    },
    {
      "type": "modify",
      "old_id": "43ac251e50f9b3e0bd568696d05e2711c751a04d",
      "old_mode": 33188,
      "old_path": "absl/container/internal/raw_hash_set_test.cc",
      "new_id": "3ad18c95048d4c8456cdfed6bd6edb6b3369cdbf",
      "new_mode": 33188,
      "new_path": "absl/container/internal/raw_hash_set_test.cc"
    }
  ]
}