wasmtime / PR #14425 Alias analysis: Reuse the exit state... · git-wasmtime

Stream: git-wasmtime

Topic: wasmtime / PR #14425 Alias analysis: Reuse the exit state...

Wasmtime GitHub notifications bot (Sep 25 2026 at 17:42):

fitzgen opened PR #14425 from fitzgen:alias-analysis-single-predecessor-state to bytecodealliance:main:

Following the same existing logic we use for determining memory "extents", if a block has a single predecessor, then entering it sees the same memory state that the single predecessor exited with. By reusing the single predecessor's exit state, we get strictly more-precise analysis results because the fixpoint's initial block entry states were computed on the function before optimization, and therefore can include dead stores that we have since eliminated, while the single predecessor's exit state reflects the post-optimization state.

This shaves off another ~13% of time from the increment-each-byte compile-time builtins benchmark. See the associated disas test output updates: inside the loop body, another redundant load was eliminated, which cascaded into another trapz getting deduplicated by GVN.

On Sightglass, this actually speeds up compilation, shaving off 0.57% of instructions retired across the whole suite. It doesn't make any statistically significant difference to execution on Sightglass.