perf: skip nonstandard_macro_braces work when the lint is disabled - #3
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…sabled `NONSTANDARD_MACRO_BRACES` is a nursery (allow-by-default) lint, but `is_offending_macro` ran on every item/stmt/expr/ty unconditionally: walking the full macro backtrace (`outer_expn_data` clone + hygiene thread-local re-entry) and hashing macro names against the brace map, even though nothing could be emitted when the lint is disabled. Bail out early on two cheap checks. First, if the span isn't from a macro there is nothing to do (same as the original loop, but before any lint-level lookup so the common non-macro node stays free). Then, once we know the span came from a macro, skip everything when the lint is allowed at this node. Behaviour is unchanged when the lint is enabled. Same-binary A/B (instructions, N=12 medians) on macro-heavy code shows wasmi -8.3%; macro-light crates (tokio/syn/regex/ripgrep/serde) stay within noise. Diagnostics are byte-identical and the UI test is green.
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NONSTANDARD_MACRO_BRACESis a nursery (allow-by-default) lint, butis_offending_macroran on every item, stmt, expr and ty regardless of whether the lint was enabled. For each node it walked the full macro backtrace (which clonesExpnDataand re-enters the hygiene thread-local once per level) and hashed macro names against the brace map. When the lint is disabled none of that can produce a warning, so it is all wasted.The fix adds two early returns at the top of
is_offending_macro:When the lint is enabled the second guard is never taken, so behaviour is unchanged.
Benchmarked performance, same-binary A/B with
perf stat, N=12 medians. Two drivers built against identical libs, differing only in this change:The improvement is on macro-heavy code, the rest are within noise