core: optimize RepeatN
#138833
core: optimize RepeatN
#138833
Conversation
...by adding an optimized implementation of `try_fold` and `fold` as well as replacing some unnecessary `mem::replace` calls with `MaybeUninit` helper methods.
rustbot
added
S-waiting-on-review
|
Looks great, thanks. @bors r+ rollup=never |
bors
added
S-waiting-on-bors
| @@ -95,10 +96,10 @@ impl<A> RepeatN<A> { | |||
| fn take_element(&mut self) -> Option<A> { | |||
| if self.count > 0 { | |||
| self.count = 0; | |||
| let element = mem::replace(&mut self.element, MaybeUninit::uninit()); | |||
There was a problem hiding this comment.
curiosity: were you seeing this be a codegen issue? I would guess this was done intentionally to "overwrite" the value with undef so that Miri could catch any further typed use of it. And overwrite-with-undef optimizes out in LLVM, normally.
There was a problem hiding this comment.
Ah, that's why it was written this way... I just saw some strange code and wanted to make it more idiomatic. I can go back to the old version and just keep the fold part, if you think there's merit in keeping this.
|
☀️ Test successful - checks-actions |
What is this?This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.Comparing 756bff9 (parent) -> f08d5c0 (this PR) Test differencesShow 8 test diffsAdditionally, 8 doctest diffs were found. These are ignored, as they are noisy. Job group index |
|
Finished benchmarking commit (f08d5c0): comparison URL. Overall result: ❌ regressions - no action needed@rustbot label: -perf-regression Instruction countThis is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.
Max RSS (memory usage)Results (primary 3.1%)This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
CyclesResults (primary 2.4%)This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
Binary sizeThis benchmark run did not return any relevant results for this metric. Bootstrap: 774.407s -> 774.928s (0.07%) |
core: optimize `RepeatN` ...by adding an optimized implementation of `try_fold` and `fold` as well as replacing some unnecessary `mem::replace` calls with `MaybeUninit` helper methods.
...by adding an optimized implementation of
try_foldandfoldas well as replacing some unnecessarymem::replacecalls withMaybeUninithelper methods.