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Compiler performance returning nested closures #68061

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#68772
Closed
Compiler performance returning nested closures#68061
#68772
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A-borrow-checkerArea: The borrow checkerA-closuresArea: Closures (`|…| { … }`)I-compiletimeIssue: Problems and improvements with respect to compile times.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

Description

@197g
197g
opened on Jan 9, 2020

The following takes approximately one year to compile:

fn main() {
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||();
}

(This estimate was derived from observing that compile time scales seemingly exponentially in the depth of the instantiated closure. At level 23 it took about 25 seconds, and at 22 only 13. Extrapolating this doubling-per-depth leads us to about a year at level 43 which is depicted above).

Activity

  1. jonas-schievink
    added
    A-closuresArea: Closures (`|…| { … }`)
    I-compiletimeIssue: Problems and improvements with respect to compile times.
    T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.
    on Jan 9, 2020

  2. tesuji commented on Jan 11, 2020

    @tesuji
    tesuji
    on Jan 11, 2020
    Contributor

    Flamegraph: https://gist.github.com/lzutao/3e900642d43ec9bad186c74b3028902d

  3. jonas-schievink
    added
    A-borrow-checkerArea: The borrow checker
    on Jan 19, 2020

  4. jonas-schievink commented on Jan 19, 2020

    @jonas-schievink
    jonas-schievink
    on Jan 19, 2020
    Contributor
    fn main() {
||||||||||||||||||||||||||||||||||||||||||||();
}

    Yields:

    +-----------------------------------------------+-----------+-----------------+----------+------------+------------+--------------+-----------------------+
| Item                                          | Self time | % of total time | Time     | Item count | Cache hits | Blocked time | Incremental load time |
+-----------------------------------------------+-----------+-----------------+----------+------------+------------+--------------+-----------------------+
| mir_borrowck                                  | 8.64s     | 98.672          | 21.61s   | 23         | 0          | 0.00ns       | 0.00ns                |

    cc @matthewjasper

  5. bors
    added a commit that references this issue on Feb 3, 2020

    Auto merge of #68772 - matthewjasper:relate-opt, r=davidtwco

    0d34a87
  6. bors
    closed this as completedin 0d34a87on Feb 3, 2020
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    A-borrow-checkerArea: The borrow checkerA-closuresArea: Closures (`|…| { … }`)I-compiletimeIssue: Problems and improvements with respect to compile times.T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.

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