Tag delay optimization#179
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When a Set_position tag fires on every transition entering a cycle
state, remove it from those transitions and emit Set_position with
offset 1 (pos - 1) on exit transitions. This turns O(n) tag writes
per loop into O(1) on exit.
Handles multi-state cycles via SCC analysis (Tarjan's algorithm) and
multi-exit cycles: exits from other cycle states are safe when they
only reach rules that don't read the tag.
Set_position { cell; offset } with offset 0 for current position and
offset 1 for previous code point (subtracted from pos).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Tags are allocated during regexp_of_pattern in the PPX, not during compile_re. The tag_starts approach incorrectly mapped all tags to rule 0. Use an NFA walk (tag_owners) to correctly discover which rule each tag belongs to. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
With the tag binding on rule 1 (not rule 0), incorrect tag ownership would allow an unsafe delay: the check would see rule 0 as unreachable from the non-s exit (correct) but miss that rule 1 IS reachable there. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
Set_positiontag fires on every transition entering a cycle state, remove it from those transitions and emitSet_positionwith offset 1 (pos - 1) on exit transitions. Turns O(n) tag writes per loop into O(1) on exit.Set_position { cell; offset }with offset 0 for current position and offset 1 for previous code point (subtracted from pos).Test plan
test_realistic.mlmulti-rule lexer baseline🤖 Generated with Claude Code