Speed up item_bodies for large match statements involving regions #57494
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Once a region has been expanded to cover a fixed region, a corresponding RegSubVar constraint won't have any effect on the expansion anymore, the same is true for constraints where the variable on the RHS has already reached static scope. By removing those constraints from the set that we're iterating over, we remove a lot of needless overhead in case of slow convergences (i.e. lots of iterations). For the unicode_normalization crate, this about cuts the time required for item_bodies checking in half.
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In functions with lots of region constraint, if the fixed point iteration converges only slowly, a lot of the var/var constraints will have equal regions most of the time. Yet, we still perform the LUB calculation and try to intern the result. Especially the latter incurs quite some overhead. This reduces the take taken by the item bodies checking pass for the unicode_normalization crate by about 75%.
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Removed the commit that modifies the match checking code for now, as that caused a test failure. |
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@bors try |
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@lzutao: 🔑 Insufficient privileges: not in try users |
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@bors try |
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Speed up item_bodies for large match statements involving regions These changes don't change anything about the complexity of the algorithms, but use some easy shortcuts or modifications to cut down some overhead. The first change, which incrementally removes the constraints from the set we're iterating over probably introduces some overhead for small to medium sized constraint sets, but it's not big enough for me to observe it in any project I tested against (not that many though). Though most other crates probably won't improve much at all, because huge matches aren't that common, the changes seemed simple enough for me to make them. Ref #55528 cc unicode-rs/unicode-normalization#29 r? @nikomatsakis
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☀️ Test successful - checks-travis |
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@rust-timer build 960c730 |
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@rust-timer build 960c730 |
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@rust-timer build 960c730 |
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Success: Queued 960c730 with parent 6ecad33, comparison URL. |
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Finished benchmarking try commit 960c730 |
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@bors r+ |
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📌 Commit 5f402b8 has been approved by |
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Speed up item_bodies for large match statements involving regions These changes don't change anything about the complexity of the algorithms, but use some easy shortcuts or modifications to cut down some overhead. The first change, which incrementally removes the constraints from the set we're iterating over probably introduces some overhead for small to medium sized constraint sets, but it's not big enough for me to observe it in any project I tested against (not that many though). Though most other crates probably won't improve much at all, because huge matches aren't that common, the changes seemed simple enough for me to make them. Ref rust-lang#55528 cc unicode-rs/unicode-normalization#29 r? @nikomatsakis
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Speed up item_bodies for large match statements involving regions These changes don't change anything about the complexity of the algorithms, but use some easy shortcuts or modifications to cut down some overhead. The first change, which incrementally removes the constraints from the set we're iterating over probably introduces some overhead for small to medium sized constraint sets, but it's not big enough for me to observe it in any project I tested against (not that many though). Though most other crates probably won't improve much at all, because huge matches aren't that common, the changes seemed simple enough for me to make them. Ref rust-lang#55528 cc unicode-rs/unicode-normalization#29 r? @nikomatsakis
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Rollup of 16 pull requests Successful merges: - #57351 (Don't actually create a full MIR stack frame when not needed) - #57353 (Optimise floating point `is_finite` (2x) and `is_infinite` (1.6x).) - #57412 (Improve the wording) - #57436 (save-analysis: use a fallback when access levels couldn't be computed) - #57453 (lldb_batchmode.py: try `import _thread` for Python 3) - #57454 (Some cleanups for core::fmt) - #57461 (Change `String` to `&'static str` in `ParseResult::Failure`.) - #57473 (std: Render large exit codes as hex on Windows) - #57474 (save-analysis: Get path def from parent in case there's no def for the path itself.) - #57494 (Speed up item_bodies for large match statements involving regions) - #57496 (re-do docs for core::cmp) - #57508 (rustdoc: Allow inlining of reexported crates and crate items) - #57547 (Use `ptr::eq` where applicable) - #57557 (resolve: Mark extern crate items as used in more cases) - #57560 (hygiene: Do not treat `Self` ctor as a local variable) - #57564 (Update the const fn tracking issue to the new metabug) Failed merges: r? @ghost
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These changes don't change anything about the complexity of the algorithms, but use some easy shortcuts or modifications to cut down some overhead.
The first change, which incrementally removes the constraints from the set we're iterating over probably introduces some overhead for small to medium sized constraint sets, but it's not big enough for me to observe it in any project I tested against (not that many though).
Though most other crates probably won't improve much at all, because huge matches aren't that common, the changes seemed simple enough for me to make them.
Ref #55528
cc unicode-rs/unicode-normalization#29
r? @nikomatsakis