Replace FNV with a faster hash function.
Hash table lookups are very hot in rustc profiles and the time taken within `FnvHash` itself is a big part of that. Although FNV is a simple hash, it processes its input one byte at a time. In contrast, Firefox has a homespun hash function that is also simple but works on multiple bytes at a time. So I tried it out and the results are compelling:
```
futures-rs-test 4.326s vs 4.212s --> 1.027x faster (variance: 1.001x, 1.007x)
helloworld 0.233s vs 0.232s --> 1.004x faster (variance: 1.037x, 1.016x)
html5ever-2016- 5.397s vs 5.210s --> 1.036x faster (variance: 1.009x, 1.006x)
hyper.0.5.0 5.018s vs 4.905s --> 1.023x faster (variance: 1.007x, 1.006x)
inflate-0.1.0 4.889s vs 4.872s --> 1.004x faster (variance: 1.012x, 1.007x)
issue-32062-equ 0.347s vs 0.335s --> 1.035x faster (variance: 1.033x, 1.019x)
issue-32278-big 1.717s vs 1.622s --> 1.059x faster (variance: 1.027x, 1.028x)
jld-day15-parse 1.537s vs 1.459s --> 1.054x faster (variance: 1.005x, 1.003x)
piston-image-0. 11.863s vs 11.482s --> 1.033x faster (variance: 1.060x, 1.002x)
regex.0.1.30 2.517s vs 2.453s --> 1.026x faster (variance: 1.011x, 1.013x)
rust-encoding-0 2.080s vs 2.047s --> 1.016x faster (variance: 1.005x, 1.005x)
syntex-0.42.2 32.268s vs 31.275s --> 1.032x faster (variance: 1.014x, 1.022x)
syntex-0.42.2-i 17.629s vs 16.559s --> 1.065x faster (variance: 1.013x, 1.021x)
```
(That's a stage1 compiler doing debug builds. Results for a stage2 compiler are similar.)
The attached commit is not in a state suitable for landing because I changed the implementation of FnvHasher without changing its name (because that would have required touching many lines in the compiler). Nonetheless, it is a good place to start discussions.
Profiles show very clearly that this new hash function is a lot faster to compute than FNV. The quality of the new hash function is less clear -- it seems to do better in some cases and worse in others (judging by the number of instructions executed in `Hash{Map,Set}::get`).
CC @brson, @arthurprs
Stabilize `..` in tuple (struct) patterns
I'd like to nominate `..` in tuple and tuple struct patterns for stabilization.
This feature is a relatively small extension to existing stable functionality and doesn't have known blockers.
The feature first appeared in Rust 1.10 6 months ago.
An example of use: https://github.com/rust-lang/rust/pull/36203
Closes https://github.com/rust-lang/rust/issues/33627
r? @nikomatsakis
[5/n] rustc: record the target type of every adjustment.
_This is part of a series ([prev](https://github.com/rust-lang/rust/pull/37404) | [next](https://github.com/rust-lang/rust/pull/37412)) of patches designed to rework rustc into an out-of-order on-demand pipeline model for both better feature support (e.g. [MIR-based](https://github.com/solson/miri) early constant evaluation) and incremental execution of compiler passes (e.g. type-checking), with beneficial consequences to IDE support as well.
If any motivation is unclear, please ask for additional PR description clarifications or code comments._
<hr>
The first commit rearranges `tcx.tables` so that all users go through `tcx.tables()`. This in preparation for per-body `Tables` where they will be requested for a specific `DefId`. Included to minimize churn.
The rest of the changes focus on adjustments, there are some renamings, but the main addition is the target type, always available in all cases (as opposed to just for unsizing where it was previously needed).
Possibly the most significant effect of this change is that figuring out the final type of an expression is now _always_ just one successful `HashMap` lookup (either the adjustment or, if that doesn't exist, the node type).
Most of the Rust community agrees that the vec! macro is clearer when
called using square brackets [] instead of regular brackets (). Most of
these ocurrences are from before macros allowed using different types of
brackets.
There is one left unchanged in a pretty-print test, as the pretty
printer still wants it to have regular brackets.
Add ArrayVec and AccumulateVec to reduce heap allocations during interning of slices
Updates `mk_tup`, `mk_type_list`, and `mk_substs` to allow interning directly from iterators. The previous PR, #37220, changed some of the calls to pass a borrowed slice from `Vec` instead of directly passing the iterator, and these changes further optimize that to avoid the allocation entirely.
This change yields 50% less malloc calls in [some cases](https://pastebin.mozilla.org/8921686). It also yields decent, though not amazing, performance improvements:
```
futures-rs-test 4.091s vs 4.021s --> 1.017x faster (variance: 1.004x, 1.004x)
helloworld 0.219s vs 0.220s --> 0.993x faster (variance: 1.010x, 1.018x)
html5ever-2016- 3.805s vs 3.736s --> 1.018x faster (variance: 1.003x, 1.009x)
hyper.0.5.0 4.609s vs 4.571s --> 1.008x faster (variance: 1.015x, 1.017x)
inflate-0.1.0 3.864s vs 3.883s --> 0.995x faster (variance: 1.232x, 1.005x)
issue-32062-equ 0.309s vs 0.299s --> 1.033x faster (variance: 1.014x, 1.003x)
issue-32278-big 1.614s vs 1.594s --> 1.013x faster (variance: 1.007x, 1.004x)
jld-day15-parse 1.390s vs 1.326s --> 1.049x faster (variance: 1.006x, 1.009x)
piston-image-0. 10.930s vs 10.675s --> 1.024x faster (variance: 1.006x, 1.010x)
reddit-stress 2.302s vs 2.261s --> 1.019x faster (variance: 1.010x, 1.026x)
regex.0.1.30 2.250s vs 2.240s --> 1.005x faster (variance: 1.087x, 1.011x)
rust-encoding-0 1.895s vs 1.887s --> 1.005x faster (variance: 1.005x, 1.018x)
syntex-0.42.2 29.045s vs 28.663s --> 1.013x faster (variance: 1.004x, 1.006x)
syntex-0.42.2-i 13.925s vs 13.868s --> 1.004x faster (variance: 1.022x, 1.007x)
```
We implement a small-size optimized vector, intended to be used primarily for collection of presumed to be short iterators. This vector cannot be "upsized/reallocated" into a heap-allocated vector, since that would require (slow) branching logic, but during the initial collection from an iterator heap-allocation is possible.
We make the new `AccumulateVec` and `ArrayVec` generic over implementors of the `Array` trait, of which there is currently one, `[T; 8]`. In the future, this is likely to expand to other values of N.
Huge thanks to @nnethercote for collecting the performance and other statistics mentioned above.
In #34268 (8531d581), we replaced matches of None to the unit value `()`
with `if let`s in places where it was deemed that this made the code
unambiguously clearer and more idiomatic. In #34638 (d37edef9), we did
the same for matches of None to the empty block `{}`.
A casual observer, upon seeing these commits fly by, might suppose that
the matter was then settled, that no further pull requests on this
utterly trivial point of style could or would be made. Unless ...
It turns out that sometimes people write the empty block with a space in
between the braces. Who knew?
The wording of RFC #495 enables moves out of slices. Unfortuantely, non-zeroing
moves out of slices introduce a very annoying complication: as slices can
vary in their length, indexes from the start and end may or may not overlap
depending on the slice's exact length, which prevents assigning a particular
drop flag for each individual element.
For example, in the code
```Rust
fn foo<T>(a: Box<[Box<[T]>]>, c: bool) -> T {
match (a, c) {
(box [box [t, ..], ..], true) => t,
(box [.., box [.., t]], false) => t,
_ => panic!()
}
}
```
If the condition is false, we have to drop the first element
of `a`, unless `a` has size 1 in which case we drop all the elements
of it but the last.
If someone comes with a nice way of handling it, we can always re-allow
moves out of slices.
This is a [breaking-change], but it is behind the `slice_patterns` feature
gate and was not allowed until recently.
Update lifetime errors to specifically note temporaries
This PR updates the error message we give in the case of a temporary value not living long enough.
Before:
<img width="497" alt="screen shot 2016-08-31 at 10 02 47 am" src="https://cloud.githubusercontent.com/assets/547158/18138551/27a06794-6f62-11e6-9ee2-bdf8bed75ca7.png">
Now:
<img width="488" alt="screen shot 2016-08-31 at 10 03 01 am" src="https://cloud.githubusercontent.com/assets/547158/18138557/2e5cf322-6f62-11e6-9047-4a78abf3d78c.png">
Specifically, it makes the following changes:
* Detects if a temporary is being used. If so, it changes the labels to mention that a temporary value specifically is in question
* Simplifies wording of the existing labels to focus on lifetimes rather than values being valid
* Changes the help to a note, since the help+span wasn't as helpful (and sometimes more confusing) than just a note.
r? @nikomatsakis
rustc_borrowck: Don't hash types in loan paths
1) Types for equal loan paths are not always equal, they can sometimes differ in lifetimes, making equal loan paths hash differently.
Example:
71bdeea561/src/libcollections/linked_list.rs (L835-L856)
One of `self.list`s has type
```
&ReFree(CodeExtent(15013/CallSiteScope { fn_id: 18907, body_id: 18912 }), BrNamed(0:DefIndex(3066), 'a(397), WontChange)) mut linked_list::LinkedList<T>
```
and other has type
```
&ReScope(CodeExtent(15018/Remainder(BlockRemainder { block: 18912, first_statement_index: 0 }))) mut linked_list::LinkedList<T>
```
(... but I'm not sure it's not a bug actually.)
2) Not hashing types is faster than hashing types.
r? @arielb1
[MIR] track Location in MirVisitor, combine Location
All the users of MirVisitor::visit_statement implement their own statement index tracking. This PR move the tracking into MirVisitor itself.
Also, there were 2 separate implementations of Location that were identical. This PR eliminates one of them.
