Optimize sum of Durations by using custom function
The current `impl Sum for Duration` uses `fold` to perform several `add`s (or really `checked_add`s) of durations. In doing so, it has to guarantee the number of nanoseconds is valid after every addition. If you squeese the current implementation into a single function it looks kind of like this:
````rust
fn sum<I: Iterator<Item = Duration>>(iter: I) -> Duration {
let mut sum = Duration::new(0, 0);
for rhs in iter {
if let Some(mut secs) = sum.secs.checked_add(rhs.secs) {
let mut nanos = sum.nanos + rhs.nanos;
if nanos >= NANOS_PER_SEC {
nanos -= NANOS_PER_SEC;
if let Some(new_secs) = secs.checked_add(1) {
secs = new_secs;
} else {
panic!("overflow when adding durations");
}
}
sum = Duration { secs, nanos }
} else {
panic!("overflow when adding durations");
}
}
sum
}
````
We only need to check if `nanos` is in the correct range when giving our final answer so we can have a more optimized version like so:
````rust
fn sum<I: Iterator<Item = Duration>>(iter: I) -> Duration {
let mut total_secs: u64 = 0;
let mut total_nanos: u64 = 0;
for entry in iter {
total_secs = total_secs
.checked_add(entry.secs)
.expect("overflow in iter::sum over durations");
total_nanos = match total_nanos.checked_add(entry.nanos as u64) {
Some(n) => n,
None => {
total_secs = total_secs
.checked_add(total_nanos / NANOS_PER_SEC as u64)
.expect("overflow in iter::sum over durations");
(total_nanos % NANOS_PER_SEC as u64) + entry.nanos as u64
}
};
}
total_secs = total_secs
.checked_add(total_nanos / NANOS_PER_SEC as u64)
.expect("overflow in iter::sum over durations");
total_nanos = total_nanos % NANOS_PER_SEC as u64;
Duration {
secs: total_secs,
nanos: total_nanos as u32,
}
}
````
We now only convert `total_nanos` to `total_secs` (1) if `total_nanos` overflows and (2) at the end of the function when we have to output a valid `Duration`. This gave a 5-22% performance improvement when I benchmarked it, depending on how big the `nano` value of the `Duration`s in `iter` were.
Don't inspect the generated existential type items
r? @nikomatsakis
My debugging led me to the `hir::ItemExistential(..)` checks, which are entirely unnecessary because we never use the items directly. The issue was that items were iterated over in a random order (due to hashmaps), so if you checked the `ItemExistential` before the function that has the actual return `impl Trait`, you'd run into those ICEs you encountered.
lint to favor `..=` over `...` range patterns; migrate to `..=` throughout codebase
We probably need an RFC to actually deprecate the `...` syntax, but here's a candidate implementation for the lint considered in #51043. (My local build is super flaky, but hopefully I got all of the test revisions.)
Add `LocalTaskObj` to `core::task`
- Splits `libcore/task.rs` into submodules
- Adds `LocalTaskObj` and `SpawnLocalObjError` (-> [Commit for this](433e6b31a7))
Note: To make reviewing easy, both actions have their own commit
r? @cramertj
Do not build LLVM tools for any of the tools
None of the tools in the list should need LLVM tools themselves as far as I can
tell; if this is incorrect, we can re-enable the tool building later.
The primary reason for doing this is that rust-central-station uses the
BuildManifest tool and building LLVM there is not cached: it takes ~1.5
hours on the 2 core machine. This commit should make nightlies and
stable releases much faster.
Followup to https://github.com/rust-lang/rust/pull/51459, r? @kennytm
I'm mostly relying on CI to test this so probably don't roll it up; I'm not sure how to (and not particularly inclined to) wait for multiple hours to test this locally. I imagine that the failures should be fairly obvious when/if encountered.
Our implementation ends up changing the `PatKind::Range` variant in the
AST to take a `Spanned<RangeEnd>` instead of just a `RangeEnd`, because
the alternative would be to try to infer the span of the range operator
from the spans of the start and end subexpressions, which is both
hideous and nontrivial to get right (whereas getting the change to the
AST right was a simple game of type tennis).
This is concerning #51043.
Remove unnecessary stat64 pointer casts
In effect, these just casted `&mut stat64` to `*mut stat64`, twice.
That's harmless, but it masked a problem when this was copied to new
code calling `fstatat`, which takes a pointer to `struct stat`. That
will be fixed by #51785, but let's remove the unnecessary casts here
too.
Update broken rustc-guide links
Recently, there has been some rearrangement of the content in the Rustc
Guide, and this commit changes the urls the match the updated guide.
New safe associated functions for PinMut
- Add safe `get_mut` and `map`
- Rename unsafe equivalents to `get_mut_unchecked` and `map_unchecked`
The discussion about this starts [in this comment](https://github.com/rust-lang/rust/issues/49150#issuecomment-399604573) on the tracking issue.
Link panic and compile_error docs
This adds documentation links between `panic!()` and `compile_error!()` as per #47275, which points out that they’re similar. It also adds a sentence to the `compile_error()` docs I thought could be added.
Obligation forest cleanup
While looking at this code I was scratching my head about whether a node could appear in both `parent` and `dependents`. Turns out it can, but it's not useful to do so, so this PR cleans things up so it's no longer possible.
Fix possibly endless loop in ReadDir iterator
Certain directories in `/proc` can cause the `ReadDir` iterator to loop indefinitely. We get an error code (22) when calling libc's `readdir_r` on these directories, but `entry_ptr` is `NULL` at the same time, signalling the end of the directory stream.
This change introduces an internal state to the iterator such that the `Some(Err(..))` value will only be returned once when calling `next`. Subsequent calls will return `None`.
fixes#50619
`Self` in where clauses may not be object safe
Needs crater, virtually certain to cause regressions.
In #50781 it was discovered that our object safety rules are not sound because we allow `Self` in where clauses without restrain. This PR is a direct fix to the rules so that we disallow methods with unsound where clauses.
This currently uses hard error to measure impact, but we will want to downgrade it to a future compat error.
Part of #50781.
r? @nikomatsakis
None of the tools in the list should need LLVM tools themselves as far as I can
tell; if this is incorrect, we can re-enable the tool building later.
The primary reason for doing this is that rust-central-station uses the
BuildManifest tool and building LLVM there is not cached: it takes ~1.5
hours on the 2 core machine. This commit should make nightlies and
stable releases much faster.
In effect, these just casted `&mut stat64` to `*mut stat64`, twice.
That's harmless, but it masked a problem when this was copied to new
code calling `fstatat`, which takes a pointer to `struct stat`. That
will be fixed by #51785, but let's remove the unnecessary casts here
too.
build: add llvm-tools to manifest
This commit expands on a previous commit to build llvm-tools as a rustup component. It causes the llvm-tools component to be built if the extended step is active. It also adds llvm-tools to the build manifest so rustup can find it.
I tested this as far as I could, but had to hack `build-manifest/src/main.rs` a bit as it is not supported on MacOS. The main change I am not sure about is this line:
```rust
self.package("llvm-tools", &mut manifest.pkg, TARGETS);
```
There are numerous calls to `self.package()`, and I'm not sure if `TARGETS`, `HOSTS`, or `["*"]` is appropriate for llvm-tools.
Otherwise I mostly copied the example set by `rustfmt-preview`.
