Cranelift: move exception-handler metadata into callsites.#10609
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fitzgen merged 2 commits intobytecodealliance:mainfrom Apr 18, 2025
Merged
Cranelift: move exception-handler metadata into callsites.#10609fitzgen merged 2 commits intobytecodealliance:mainfrom
fitzgen merged 2 commits intobytecodealliance:mainfrom
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bjorn3
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Apr 17, 2025
bjorn3
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Apr 17, 2025
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bjorn3
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Apr 17, 2025
…tor. This commit updates the call-site metadata to refer to a range in a flattened vector containing tuples of handler tags and labels (before finalization) or code offsets (after finalization). It also provides an iterator accessor `.call_sites()` on the finalized buffer that yields this information in a safe way.
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This PR starts with a cherry-pick of @bjorn3's work at 1, which switches exception-handler metadata from a separate list of records (of callsite offset, tag, handler offset tuples) to per-callsite (tag, handler) tuples. This is cleaner for both the native-code use-case and for our planned Wasmtime use-case: in both cases one knows the specific callsite in each frame and wants to look at handlers only for that callsite. The old representation was designed for fast emission and flat storage, but we can get flat storage with this semantic structure as well...
... with the second commit, in which I've updated @bjorn3's implementation to keep a separate vector of handler tuples in the
MachBuffer, and refer to ranges in this vector in the callsite metadata. It also provides an iterator that yields per-callsite information in a safe way.No functional change in-tree (because Cranelift and Wasmtime both do not use this metadata yet) but should enable
cg_clifto use our exception support for native unwind.Co-authored-by:
bjorn3 <17426603+bjorn3@users.noreply.github.com>