perf: skip redundant clone analysis for clone-free functions - #17486
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charliermarsh wants to merge 2 commits into
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perf: skip redundant clone analysis for clone-free functions#17486charliermarsh wants to merge 2 commits into
charliermarsh wants to merge 2 commits into
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Scan function bodies for clone-like method calls before requesting optimized MIR. Skip nested closures because they receive their own lint callbacks, and preserve qualified-call, alias, macro, and closure coverage. On Rust 1.95, the synthetic 4,096-function workload improved from 220 ms to 178 ms. Codex incremental core checks improved from 4.19 s to 3.98 s at the median.
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CommanderStorm
approved these changes
Aug 2, 2026
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| fn contains_clone_like_call(body: &Body<'_>) -> bool { | ||
| for_each_expr_without_closures(body, |expr| { | ||
| if let ExprKind::MethodCall(method, ..) = expr.kind | ||
| && matches!( | ||
| method.ident.name, | ||
| sym::clone | sym::to_owned | sym::to_string | sym::to_path_buf | sym::to_os_string | ||
| ) | ||
| { | ||
| ControlFlow::Break(()) | ||
| } else { | ||
| ControlFlow::Continue(()) | ||
| } | ||
| }) | ||
| .is_some() |
Contributor
There was a problem hiding this comment.
see above
Suggested change
| fn contains_clone_like_call(body: &Body<'_>) -> bool { | |
| for_each_expr_without_closures(body, |expr| { | |
| if let ExprKind::MethodCall(method, ..) = expr.kind | |
| && matches!( | |
| method.ident.name, | |
| sym::clone | sym::to_owned | sym::to_string | sym::to_path_buf | sym::to_os_string | |
| ) | |
| { | |
| ControlFlow::Break(()) | |
| } else { | |
| ControlFlow::Continue(()) | |
| } | |
| }) | |
| .is_some() | |
| fn contains_no_clone_like_call(body: &Body<'_>) -> bool { | |
| for_each_expr_without_closures(body, |expr| { | |
| if let ExprKind::MethodCall(method, ..) = expr.kind | |
| && matches!( | |
| method.ident.name, | |
| sym::clone | sym::to_owned | sym::to_string | sym::to_path_buf | sym::to_os_string | |
| ) | |
| { | |
| ControlFlow::Break(()) | |
| } else { | |
| ControlFlow::Continue(()) | |
| } | |
| }) | |
| .is_none() |
Comment on lines
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| // Closures receive their own `check_fn` callback and are checked separately. | ||
| // Building MIR for `fn`s with unsatisfiable clauses results in ICE. | ||
| if fn_has_unsatisfiable_clauses(cx, def_id.to_def_id()) { | ||
| if !contains_clone_like_call(body) || fn_has_unsatisfiable_clauses(cx, def_id.to_def_id()) { |
Contributor
There was a problem hiding this comment.
🤔 would this be cleaner?
(lol on the diff github produces)
Suggested change
| // Closures receive their own `check_fn` callback and are checked separately. | |
| // Building MIR for `fn`s with unsatisfiable clauses results in ICE. | |
| if fn_has_unsatisfiable_clauses(cx, def_id.to_def_id()) { | |
| if !contains_clone_like_call(body) || fn_has_unsatisfiable_clauses(cx, def_id.to_def_id()) { | |
| // Closures receive their own `check_fn` callback and are checked separately. | |
| // Building MIR for `fn`s with unsatisfiable clauses results in ICE and is expensive. | |
| if contains_no_clone_like_call(body) || fn_has_unsatisfiable_clauses(cx, def_id.to_def_id()) { |
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On master,
redundant_clonerequests optimized MIR for every function. It turns out this is fairly expensive. This PR adds a pre-filter that scans each function’s HIR first and skips MIR analysis unless the body contains a.clone(),.to_owned(),.to_string(),.to_path_buf(), or.to_os_string()call. (It's just a pre-filter so false positives are acceptable.)Benchmarking on my M4, incremental Clippy checks in
codex-rswent from 4.19 s to 3.98 s (~5% improvement). A more contrived workload (4,096 functions) went from 220 ms to 178 ms (~19% improvement).changelog: none