Avoid allocating in updateLineCountAndPosFor #44241
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...(in the call to `computeLineStarts`) by detecting the very common case of not having a linebreak.
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On my box, this cuts total time for the compiling ts/src by about 1% and I suspect it saves additional GC time in larger projects. |
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@typescript-bot test this |
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@typescript-bot perf test this |
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Heya @amcasey, I've started to run the perf test suite on this PR at 22e2a80. You can monitor the build here. Update: The results are in! |
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@amcasey Here they are:Comparison Report - master..44241
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It is weird that Monaco and Compiler-Unions seems to see no improvement. |
JoostK
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May 24, 2021
| const lineStartsOfS = computeLineStarts(s); | ||
| if (lineStartsOfS.length > 1) { | ||
| // Most arguments don't contain one of JS's four linebreak characters | ||
| if (/[\r\n\u2028\u2029]/.test(s)) { |
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Drive by comment 🚗: I wonder if it could be beneficial to:
- Create the regex once
- Leverage the regex's
lastIndexinstead of usingcomputeLineStarts. This would involve iteratively matching to count the lines, then using the lastlastIndex+1 (and probably +2 for u2028/u2029) in favor oflast(lineStartsOfS).
(at which point it basically becomes a linear search just like computeLineStarts does, but without allocating the array. Maybe using a regex is not even needed)
Btw, lineStart = (linePos - output.length) === 0; a couple lines lower can just be lineStart = linePos === output.length; (probably won't make a difference).
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Thanks! If I don't abandon this in favor of #44242, I'll give that a shot (and, yeah, the === 0 was bugging me too).
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This does not appear to have the same memory benefit as #44242. |
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...(in the call to
computeLineStarts) by detecting the very common case of not having a linebreak.