The amortized case is much more common than the exact case, and it is
typically instantiated many times.
Also, we can put a chunk of the code into a function that isn't generic
over T, which reduces the amount of LLVM IR generated quite a lot,
improving compile times.
It's only used once, for `VecDeque`, and can easily be replaced by
something else. The commit changes `grow_if_necessary` to `grow` to
avoid some small regressions caused by changed inlining.
The commit also removes `Strategy::Double`, and streamlines the
remaining variants of `Strategy`.
It's a compile time win on some benchmarks because the many
instantations of `RawVec::grow` are a little smaller.
I also added test cases to make sure the optimization can fire on all of
these cases:
```rust
fn case_1(o: Option<u8>) -> Option<u8> {
match o {
Some(u) => Some(u),
None => None,
}
}
fn case2(r: Result<u8, i32>) -> Result<u8, i32> {
match r {
Ok(u) => Ok(u),
Err(i) => Err(i),
}
}
fn case3(r: Result<u8, i32>) -> Result<u8, i32> {
let u = r?;
Ok(u)
}
```
Without MIR inlining, this still does not completely optimize away the
`?` operator because the `Try::into_result()`, `From::from()` and
`Try::from_error()` calls still exist. This does move us a bit closer to
that goal though because:
- We can now run the pass on mir-opt-level=1
- We no longer depend on the copy propagation pass running which is
unlikely to stabilize anytime soon.
Given code like `v[&field].boo();` where `field: String` and
`.boo(&mut self)`, typeck will have decided that `v` is accessed using
`Index`, but when `boo` adds a new `mut` obligation,
`convert_place_op_to_mutable` is called. When this happens, for *some
reason* the arguments' dereference adjustments are completely ignored
causing an error saying that `IndexMut` is not satisfied:
```
error[E0596]: cannot borrow data in an index of `Indexable` as mutable
--> src/main.rs:30:5
|
30 | v[&field].boo();
| ^^^^^^^^^ cannot borrow as mutable
|
= help: trait `IndexMut` is required to modify indexed content, but it is not implemented for `Indexable`
```
This is not true, but by changing `try_overloaded_place_op` to retry
when given `Needs::MutPlace` without passing the argument types, the
example successfully compiles.
I believe there might be more appropriate ways to deal with this.
Use CDN for ci-caches on download
This will reduce costs, as well as lays the groundwork for developers to be able
to locally pull the published docker images without needing AWS credentials.
r? @pietroalbini
Const prop aggregates even if partially or fully modified
r? @wesleywiser
cc @rust-lang/wg-mir-opt I'm moderately scared of this change, but I'm confident in having reviewed all the cases.
