Precompute fast-path eligibility for gang processing#576
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Replace the 11-condition runtime check in terminalAppendMixedAsciiGang: with a precomputed _fastPathEligible ivar that is recomputed at each state-mutation point. The hot path is now one ivar read plus two lightweight checks (tokens.count and grid canTakeFastPath). Add terminalActiveCharsetDidChangeTo: delegate callback so charset changes (SI/SO) can invalidate the cache. Include a debug assertion that validates the cached value against a fresh computation on every call.
Address three cache invalidation bugs in the precomputed _fastPathEligible boolean: - Recompute after evaluateTriggers: block executes (expectations can be consumed by matching during trigger evaluation) - Recompute after updateExpectFrom: updates expectations - Recompute after setTerminalEnabled: assigns terminal modes during session startup/revive Add self-healing recompute at the top of terminalAppendMixedAsciiGang: for lazy expectation deadline expiry (deadlines pass without notification, so the cache cannot be eagerly invalidated). Add mutation-queue-only annotations to _computeFastPathEligible and _recomputeFastPathEligible. Add 14 new tests covering every _fastPathEligible condition: insert mode, wraparound, ANSI mode, alt buffer, command start coord, line drawing mode, logging, publishing, expectations, print buffer, multiple simultaneous conditions, expectation consumed by match, expectation expired by deadline, and post-trigger action drain transitions.
Add testGang_fastPathPerformance (cached boolean gang path) and testGang_charAtATimePerformance (character-at-a-time baseline) using XCTest measure blocks. 100 gang calls of 100 lines each per iteration.
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I'm not sure the juice is worth the squeeze. After running it in an optimized build, I get: I've pushed my changes to the fastpath-perf branch so you can see what I did. That being said, I do plan to merge the performance tests because it's awesome to have performance tests. |
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Ah, I must have been benching the debug build! If the gains seem too good to be true... |
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Summary
10 XCTest measure iterations x100 gang calls of 100 lines (10,000 lines per iteration, 1,000,000 lines total per test).