Stream: git-wasmtime

Topic: wasmtime / PR #12613 Cranelift: update ValueDataPacked to...

Wasmtime GitHub notifications bot (Feb 18 2026 at 00:07):

cfallin opened PR #12613 from cfallin:bigger-valuedata to bytecodealliance:main:

This updates the ValueDataPacked scheme from the old

            (enum tag)    (CLIF type)    (value 1)     (value 2)
///        | tag:2 |  type:14        |    x:24       | y:24          |

encoding in a u64 to a new

///        | tag:2 |  type:14        |    x:32       | y:32
|

encoding, with a packed tag attribute to ensure the struct fits in 10 bytes. This permits the full range of Value (a u32 entity index) to be encoded, removing the remaining major limit on function body size after the work in #12611 to address #12229.

Curiously, this appears to be a speedup in compile time of 3-5% on bz2 and 3% on spidermonkey-json (Sightglass, 50 data points each). My best guess as to why is that putting the value fields in their own u32s allows for quick access without shifts/masks, which is actually better than the unaligned accesses (caused by 10-byte size) -- which have no penalty on modern mainstream CPUs -- and 25% size inflation of the value-definitions array.

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Wasmtime GitHub notifications bot (Feb 18 2026 at 00:07):

cfallin requested fitzgen for a review on PR #12613.

Wasmtime GitHub notifications bot (Feb 18 2026 at 00:07):

cfallin requested wasmtime-compiler-reviewers for a review on PR #12613.

Wasmtime GitHub notifications bot (Feb 18 2026 at 00:15):

cfallin updated PR #12613.

Wasmtime GitHub notifications bot (Feb 18 2026 at 03:34):

github-actions[bot] added the label cranelift on PR #12613.

Wasmtime GitHub notifications bot (Feb 18 2026 at 15:52):

fitzgen submitted PR review.

Wasmtime GitHub notifications bot (Feb 18 2026 at 15:52):

fitzgen added PR #12613 Cranelift: update ValueDataPacked to support full Value range. to the merge queue

Wasmtime GitHub notifications bot (Feb 18 2026 at 16:26):

fitzgen merged PR #12613.

Wasmtime GitHub notifications bot (Feb 18 2026 at 16:26):

fitzgen removed PR #12613 Cranelift: update ValueDataPacked to support full Value range. from the merge queue

Last updated: Feb 24 2026 at 04:36 UTC