[PERF] Don't spawn so many compilers (3/2) (19m -> 250k) #15030
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blyxyas
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Avoid creating so many SessionGlobals
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| // | ||
| // Also, as we only check for attribute names and don't do macro expansion, | ||
| // we can check only for #[test] | ||
| if !(text.contains("fn main") || text.contains("#[test]")) { |
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hm, if someone writes fn main() instead of fn main() will this cause false negatives?
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Optimize
needless_doctest_main, make it short-circuit, make sure that we don't spin up a new compiler on EVERY code block.The old implementation was creating a new compiler, new parser, new thread, new SessionGlobals, new everything for each code block. No matter if they actually didn't even contain
fn main()or anything relevant.On callgrind, seems that we're reducing about a 6.7242% de cycle count (which turns out to be a 38 million instruction difference, great!). Benchmarked in
bumpalo-3.16.0. Also on bumpalo we spawn 78 less threads. This movesSessionGlobals::newfrom the top time-consuming function by itself in some benchmarks, into one not even in the top 500.Also, populate the test files.
changelog:[
needless_doctest_main]: Avoid spawning so many threads in unnecessary circumstances