Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Option<NonNullablePtr> optimization is unavailable to library smart pointers #7576

Closed
thestinger opened this issue Jul 4, 2013 · 6 comments · Fixed by #19765
Closed

Option<NonNullablePtr> optimization is unavailable to library smart pointers #7576

thestinger opened this issue Jul 4, 2013 · 6 comments · Fixed by #19765
Labels
I-slow Issue: Problems and improvements with respect to performance of generated code.

Comments

@thestinger
Copy link
Contributor

No description provided.

@sanxiyn
Copy link
Member

sanxiyn commented Oct 14, 2013

Triaging. See #8678 for what happened since the last time.

@huonw huonw mentioned this issue Mar 30, 2014
Closed
@nikomatsakis
Copy link
Contributor

I think there is general agreement that we need some sort of attribute smart pointers can use to opt-in here.

@nikomatsakis
Copy link
Contributor

An RFC seems appropriate.

@emberian
Copy link
Member

I can write up an RFC for #[unsafe_not_null] today.

@emberian
Copy link
Member

emberian commented Apr 1, 2014

And by today I mean "much later"

@emberian
Copy link
Member

emberian commented Apr 6, 2014

rust-lang/rfcs#36

This was referenced Dec 5, 2014
Closed
Merged
bors added a commit that referenced this issue Dec 29, 2014
@bors
auto merge of #19765 : luqmana/rust/nonzero-lang-item, r=nikomatsakis
25fb12b 
This extends the nullable enum opt to traverse beyond just the first level to find possible fields to use as the discriminant. So now, it'll work through structs, tuples, and fixed sized arrays. This also introduces a new lang item, NonZero, that you can use to wrap raw pointers or integral types to indicate to rustc that the underlying value is known to never be 0/NULL. We then use this in Vec, Rc and Arc to have them also benefit from the nullable enum opt.

As per rust-lang/rfcs#499 NonZero is not exposed via the `libstd` facade.

```
x86_64 Linux:
                        T       Option<T> (Before)      Option<T> (After)
----------------------------------------------------------------------------------
Vec<int>                24          32                      24
String                  24          32                      24
Rc<int>                 8           16                      8
Arc<int>                8           16                      8
[Box<int>, ..2]         16          24                      16
(String, uint)          32          40                      32
```

Fixes #19419.
Fixes #13194.
Fixes #9378.
Fixes #7576.
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Assignees
No one assigned
Labels
I-slow Issue: Problems and improvements with respect to performance of generated code.
Projects
None yet
Milestone
No milestone
Development

Successfully merging a pull request may close this issue.

Enum layout optimizations luqmana/rust
Enum layout optimizations luqmana/rust
4 participants
@sanxiyn @nikomatsakis @emberian @thestinger