The unconditional ground-state indexOf regressed dense back-to-back
SGR/CSI streams, where the code unit at the cursor is already the ESC and
the search pays call plus SIMD setup to find it in place. Check the
current unit first and fall back to the native search otherwise.
0.9 MiB dense SGR/CSI medians: 2.04 ms before this PR, 2.56 ms with the
unconditional search, 1.92 ms with the hybrid. Sparse colored logs and
plain text keep the full search win (0.36 / 0.016 ms vs 1.54 / 1.41 ms
baseline). Differential over the full VT alphabet with lone and split
surrogates matched 388,416 cases against both prior implementations with
zero mismatches; the ground-scan work budget now records 16 inspected
code units and 2 native searches.
Neil
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