perf(moarstats): hint rare branches with core::hint::cold_path()#3823
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jqnatividad merged 2 commits intomasterfrom May 5, 2026
Merged
perf(moarstats): hint rare branches with core::hint::cold_path()#3823jqnatividad merged 2 commits intomasterfrom
jqnatividad merged 2 commits intomasterfrom
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Mark exceptional branches inside the per-record hot loops of `count_chunk_outliers` and `compute_chunk_bivariate` as cold so the compiler can keep the common path tight: - UTF-8 decode failures on byte cells (CSV cells are virtually always valid UTF-8) - `chunk_stats.get_mut` "this can't happen" safety guards already paired with `debug_assert!(false, ...)` Leaf `compute_*` finalizer helpers, `is_empty()` checks in the parsers, and the outlier-bucket if/else chain were intentionally not hinted — they are not on a tight inner loop or their branch frequency depends on the dataset. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Up to standards ✅🟢 Issues
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Address roborev review #1956 (Low): move `use core::hint::cold_path;` to the top of the import block, matching the convention in `src/cmd/stats.rs`. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
core::hint::cold_path()hints to exceptional branches inside the per-record hot loops ofcount_chunk_outliersandcompute_chunk_bivariate, matching the pattern already used instats.rs,frequency.rs, andvalidate.rs.chunk_stats.get_mutsafety guards already paired withdebug_assert!(false, ...).compute_*finalizer helpers (called O(columns), not in a tight loop),is_empty()checks inparse_float_opt*/parse_date_to_days(empty cells are common in real CSVs), and the outlier-bucket if/else chain (whole purpose of that loop is counting outliers — can't assume "normal" is hot).Test plan
cargo build --locked --bin qsv -F all_features— cleancargo test moarstats -F all_features— 88 passed, 0 failedcargo clippy --bin qsv -F all_features -- -D warnings— clean🤖 Generated with Claude Code