Fix HFS write-back insertion using structural inner-label tracking#734
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Fix HFS write-back insertion using structural inner-label tracking#734
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Hot Field Scalarization (HFS) was inserting write-back stores (self.field = _hfs_local) before every `break` statement, including breaks inside inlined function bodies (__inline_ labeled blocks). These breaks are value-returning exits within the same scope, not control flow that leaves the loop — the containing block's own exit handles the write-back. This caused unnecessary struct.set instructions in hot loops like JsonDeserializer::skip_whitespace, where the inlined get_byte block had a redundant `self.pos = _hfs_pos` before the break. Now breaks targeting __inline_ labels skip write-back insertion. https://claude.ai/code/session_01WDWXhoRc8GFXJYeY6Ms4iy
The field_scalarize change eliminates redundant struct.set write-backs before breaks targeting __inline_ labeled blocks, reducing generated WIR across serde/json tests. https://claude.ai/code/session_01WDWXhoRc8GFXJYeY6Ms4iy
Instead of checking if a break label starts with "__inline_", collect all labels defined within the HFS scope (loop body) and skip write-back for breaks targeting any inner label. This is structurally correct and decouples the optimizer from the inliner's naming convention. The inner_labels set is computed once at the HFS entry point and passed through all recursive replace_in_block calls, ensuring breaks at any nesting depth correctly identify scope-local targets. https://claude.ai/code/session_01WDWXhoRc8GFXJYeY6Ms4iy
Golden fixture conflicts only — will be regenerated by on-task-done. https://claude.ai/code/session_01WDWXhoRc8GFXJYeY6Ms4iy
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Summary
The HFS (Hot Field Scalarization) pass inserts
struct.setwrite-backs beforebreakstatements that escape the HFS scope. Previously, breaks targeting inlined labeled blocks (e.g.break __inline_foo_1) incorrectly received write-backs too, even though they stay within the HFS-managed loop body.The initial fix checked for the
__inline_label prefix, but this was an ad-hoc coupling between the optimizer and the inliner's naming convention. This PR replaces it with a structural approach:collect_inner_labels) at the entry pointreplace_in_blockcalls via a newinner_labelsparameter onReplaceCtxThis is more correct (catches cases the prefix check missed, e.g.
base64_decode,base64_encode) and decouples the optimizer from label naming conventions.Test plan
hfs_inline_break_no_writeback.wadowithwir_not_expect:O2assertionmise run on-task-done)https://claude.ai/code/session_01WDWXhoRc8GFXJYeY6Ms4iy