[Instructions -0.08% vs main; paired PGO estimate] Try a checked recent source-file index before binary search - #155
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Use one relaxed atomic hint, validate containment under the existing source-files read guard and fall back to the original binary search. Tests cover boundaries, Unicode, invalid positions and appends.
Negative percentages mean less elapsed time or fewer resources. The title is an individual local instruction-count estimate: instructions:u as an equal-case geometric mean over the 249 Primary cases, the metric the upstream perf bot summarizes; small changes may be measurement noise.
The two recorded repetitions give aggregate instruction estimates of -0.077% and -0.077% for the title comparison. Mixed directions are marked in the title. This repeatability check is not a confidence interval.
Both compilers use the same source base, CI LLVM, fixed standard libraries, ThinLTO and jemalloc. Each has separate nine-workload Rust PGO training. The stock collector measures all 20 Primary benchmarks: 249 Check/Debug/Opt and full/incremental cases, two observations per compiler per case, alternating baseline/candidate order by crate. No other campaign builds run during measurement. Percentages are equal-case geometric means. LLVM retraining and BOLT are omitted.
This branch has one commit directly on main. Its exact measured source passed the full UI and incremental suites plus the additional suites recorded in the build provenance.
Fixed main commit:
da47efd27287edb02eed0b5a178a165c8f258e37. Measured source patch SHA-256:05be637ff38009beaec71ec343c354c1009a4a603271a986d8c866c7fb69767f.Local raw measurements and per-case CSVs:
independent-pr155-main-v1-comparison.csvin the September 6 investigation directory. Build/test provenance:pgo/independent-pr155-source-timing-v1/provenance.json.