Cache repeated mapper instantiations only within a single instantiation call #61535
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FWIW, check times for TS 5.8 This PR (#61535) at commit 82666d1: |
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JoostK
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Apr 12, 2025
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| if (index === -1) { | ||
| pushActiveMapper(mapper); | ||
| } | ||
| const key = type.id + getAliasId(aliasSymbol, aliasTypeArguments); | ||
| const mapperCache = activeTypeMappersCaches[index !== -1 ? index : activeTypeMappersCount - 1]; | ||
| const cached = mapperCache.get(key); | ||
| if (cached) { | ||
| return cached; | ||
| } |
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Since key and mapperCache aren't used for initial occurrences of mappers, computing the key can be avoided:
Suggested change
| if (index === -1) { | |
| pushActiveMapper(mapper); | |
| } | |
| const key = type.id + getAliasId(aliasSymbol, aliasTypeArguments); | |
| const mapperCache = activeTypeMappersCaches[index !== -1 ? index : activeTypeMappersCount - 1]; | |
| const cached = mapperCache.get(key); | |
| if (cached) { | |
| return cached; | |
| } | |
| let key: string | undefined; | |
| let mapperCache: Map<string, Type> | undefined; | |
| if (index === -1) { | |
| pushActiveMapper(mapper); | |
| } else { | |
| key = type.id + getAliasId(aliasSymbol, aliasTypeArguments); | |
| mapperCache = activeTypeMappersCaches[index]; | |
| const cached = mapperCache.get(key); | |
| if (cached) { | |
| return cached; | |
| } | |
| } |
Likely also needs some updates below because of the undefineds.
I also wonder if it's worth making the allocation of the Map lazy (and/or to keep it around if it's empty)
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Or possibly only push if the type could potentially recurse (depending on the type flags), although I suspect that delaying the allocation of Map should be similar in perf; the push/pop operations themselves should be rather cheap.
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This is an alternative to #61505 , I hope this might have better memory consumption characteristics (at the expense of repeated work, the instantiations diff can be seen here).