cache param env canonicalization
Canonicalize ParamEnv only once and store it. Then whenever we try to canonicalize `ParamEnvAnd<'tcx, T>` we only have to canonicalize `T` and then merge the results.
Prelimiary results show ~3-4% savings in diesel and serde benchmarks.
Best to review commits individually. Some commits have a short description.
Initial implementation had a soundness bug (https://github.com/rust-lang/rust/pull/117749#issuecomment-1840453387) due to cache invalidation:
- When canonicalizing `Ty<'?0>` we first try to resolve region variables in the current InferCtxt which may have a constraint `?0 == 'static`. This means that we register `Ty<'?0> => Canonical<Ty<'static>>` in the cache, which is obviously incorrect in another inference context.
- This is fixed by not doing region resolution when canonicalizing the query *input* (vs. response), which is the only place where ParamEnv is used, and then in a later commit we *statically* guard against any form of inference variable resolution of the cached canonical ParamEnv's.
r? `@ghost`
rustdoc-search: use set ops for ranking and filtering
This commit adds ranking and quick filtering to type-based search, improving performance and having it order results based on their type signatures.
Preview
-------
Profiler output: https://notriddle.com/rustdoc-html-demo-6/profile-8/index.html
Preview: https://notriddle.com/rustdoc-html-demo-6/ranking-and-filtering-v2/std/index.html
Motivation
----------
If I write a query like `str -> String`, a lot of functions come up. That's to be expected, but `String::from` should come up on top, and it doesn't right now. This is because the sorting algorithm is based on the functions name, and doesn't consider the type signature at all. `slice::join` even comes up above it!
To fix this, the sorting should take into account the function's signature, and the closer match should come up on top.
Guide-level description
-----------------------
When searching by type signature, types with a "closer" match will show up above types that match less precisely.
Reference-level explanation
---------------------------
Functions signature search works in three major phases:
* A compact "fingerprint," based on the [bloom filter] technique, is used to check for matches and to estimate the distance. It sometimes has false positive matches, but it also operates on 128 bit contiguous memory and requires no backtracking, so it performs a lot better than real unification.
The fingerprint represents the set of items in the type signature, but it does not represent nesting, and it ignores when the same item appears more than once.
The result is rejected if any query bits are absent in the function, or if the distance is higher than the current maximum and 200 results have already been found.
* The second step performs unification. This is where nesting and true bag semantics are taken into account, and it has no false positives. It uses a recursive, backtracking algorithm.
The result is rejected if any query elements are absent in the function.
[bloom filter]: https://en.wikipedia.org/wiki/Bloom_filter
Drawbacks
---------
This makes the code bigger.
More than that, this design is a subtle trade-off. It makes the cases I've tested against measurably faster, but it's not clear how well this extends to other crates with potentially more functions and fewer types.
The more complex things get, the more important it is to gather a good set of data to test with (this is arguably more important than the actual benchmarking ifrastructure right now).
Rationale and alternatives
--------------------------
Throwing a bloom filter in front makes it faster.
More than that, it tries to take a tactic where the system can not only check for potential matches, but also gets an accurate distance function without needing to do unification. That way it can skip unification even on items that have the needed elems, as long as they have more items than the currently found maximum.
If I didn't want to be able to cheaply do set operations on the fingerprint, a [cuckoo filter] is supposed to have better performance. But the nice bit-banging set intersection doesn't work AFAIK.
I also looked into [minhashing], but since it's actually an unbiased estimate of the similarity coefficient, I'm not sure how it could be used to skip unification (I wouldn't know if the estimate was too low or too high).
This function actually uses the number of distinct items as its "distance function." This should give the same results that it would have gotten from a Jaccard Distance $1-\frac{|F\cap{}Q|}{|F\cup{}Q|}$, while being cheaper to compute. This is because:
* The function $F$ must be a superset of the query $Q$, so their union is just $F$ and the intersection is $Q$ and it can be reduced to $1-\frac{|Q|}{|F|}.
* There are no magic thresholds. These values are only being used to compare against each other while sorting (and, if 200 results are found, to compare with the maximum match). This means we only care if one value is bigger than the other, not what it's actual value is, and since $Q$ is the same for everything, it can be safely left out, reducing the formula to $1-\frac{1}{|F|} = \frac{|F|}{|F|}-\frac{1}{|F|} = |F|-1$. And, since the values are only being compared with each other, $|F|$ is fine.
Prior art
---------
This is significantly different from how Hoogle does it.
It doesn't account for order, and it has no special account for nesting, though `Box<t>` is still two items, while `t` is only one.
This should give the same results that it would have gotten from a Jaccard Distance $1-\frac{|A\cap{}B|}{|A\cup{}B|}$, while being cheaper to compute.
Unresolved questions
--------------------
`[]` and `()`, the slice/array and tuple/union operators, are ignored while building the signature for the query. This is because they match more than one thing, making them ambiguous. Unfortunately, this also makes them a performance cliff. Is this likely to be a problem?
Right now, the system just stashes the type distance into the same field that levenshtein distance normally goes in. This means exact query matches show up on top (for example, if you have a function like `fn nothing(a: Nothing, b: i32)`, then searching for `nothing` will show it on top even if there's another function with `fn bar(x: Nothing)` that's technically a closer match in type signature.
Future possibilities
--------------------
It should be possible to adopt more sorting criteria to act as a tie breaker, which could be determined during unification.
[cuckoo filter]: https://en.wikipedia.org/wiki/Cuckoo_filter
[minhashing]: https://en.wikipedia.org/wiki/MinHash
Rollup of 4 pull requests
Successful merges:
- #118759 (Support bare unit structs in destructuring assignments)
- #118871 (Coroutine variant fields can be uninitialized)
- #118883 (Change a typo mistake in the-doc-attribute.md)
- #118906 (Fix LLD thread flags in bootstrap on Windows)
r? `@ghost`
`@rustbot` modify labels: rollup
The hash changes are based on some tests with `arti` and various
specific queries, aimed at reducing the false positive rate.
Sorting the query elements so that generics always come first is
instead aimed at reducing the number of Map operations on mgens,
assuming if the bloom filter does find a false positive, it'll
be able to reject the row without having to track a mapping.
- https://hur.st/bloomfilter/?n=3&p=&m=96&k=6
Different functions have different amounts of inputs, and
unification isn't very slow anyway, so figuring out a single
ideal number of hash functions is nasty, but 6 keeps things
low even up to 10 inputs.
- https://web.archive.org/web/20210927123933/https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.72.2442&rep=rep1&type=pdf
This is the `h1` and `h2`, both derived from `h0`.
This commit adds ranking and quick filtering to type-based search,
improving performance and having it order results based on their
type signatures.
Motivation
----------
If I write a query like `str -> String`, a lot of functions come up.
That's to be expected, but `String::from_str` should come up on top, and
it doesn't right now. This is because the sorting algorithm is based
on the functions name, and doesn't consider the type signature at all.
`slice::join` even comes up above it!
To fix this, the sorting should take into account the function's
signature, and the closer match should come up on top.
Guide-level description
-----------------------
When searching by type signature, types with a "closer" match will
show up above types that match less precisely.
Reference-level explanation
---------------------------
Functions signature search works in three major phases:
* A compact "fingerprint," based on the [bloom filter] technique, is used to
check for matches and to estimate the distance. It sometimes has false
positive matches, but it also operates on 128 bit contiguous memory and
requires no backtracking, so it performs a lot better than real
unification.
The fingerprint represents the set of items in the type signature, but it
does not represent nesting, and it ignores when the same item appears more
than once.
The result is rejected if any query bits are absent in the function, or
if the distance is higher than the current maximum and 200
results have already been found.
* The second step performs unification. This is where nesting and true bag
semantics are taken into account, and it has no false positives. It uses a
recursive, backtracking algorithm.
The result is rejected if any query elements are absent in the function.
[bloom filter]: https://en.wikipedia.org/wiki/Bloom_filter
Drawbacks
---------
This makes the code bigger.
More than that, this design is a subtle trade-off. It makes the cases I've
tested against measurably faster, but it's not clear how well this extends
to other crates with potentially more functions and fewer types.
The more complex things get, the more important it is to gather a good set
of data to test with (this is arguably more important than the actual
benchmarking ifrastructure right now).
Rationale and alternatives
--------------------------
Throwing a bloom filter in front makes it faster.
More than that, it tries to take a tactic where the system can not only check
for potential matches, but also gets an accurate distance function without
needing to do unification. That way it can skip unification even on items
that have the needed elems, as long as they have more items than the
currently found maximum.
If I didn't want to be able to cheaply do set operations on the fingerprint,
a [cuckoo filter] is supposed to have better performance.
But the nice bit-banging set intersection doesn't work AFAIK.
I also looked into [minhashing], but since it's actually an unbiased
estimate of the similarity coefficient, I'm not sure how it could be used
to skip unification (I wouldn't know if the estimate was too low or
too high).
This function actually uses the number of distinct items as its
"distance function."
This should give the same results that it would have gotten from a Jaccard
Distance $1-\frac{|F\cap{}Q|}{|F\cup{}Q|}$, while being cheaper to compute.
This is because:
* The function $F$ must be a superset of the query $Q$, so their union is
just $F$ and the intersection is $Q$ and it can be reduced to
$1-\frac{|Q|}{|F|}.
* There are no magic thresholds. These values are only being used to
compare against each other while sorting (and, if 200 results are found,
to compare with the maximum match). This means we only care if one value
is bigger than the other, not what it's actual value is, and since $Q$ is
the same for everything, it can be safely left out, reducing the formula
to $1-\frac{1}{|F|} = \frac{|F|}{|F|}-\frac{1}{|F|} = |F|-1$. And, since
the values are only being compared with each other, $|F|$ is fine.
Prior art
---------
This is significantly different from how Hoogle does it.
It doesn't account for order, and it has no special account for nesting,
though `Box<t>` is still two items, while `t` is only one.
This should give the same results that it would have gotten from a Jaccard
Distance $1-\frac{|A\cap{}B|}{|A\cup{}B|}$, while being cheaper to compute.
Unresolved questions
--------------------
`[]` and `()`, the slice/array and tuple/union operators, are ignored while
building the signature for the query. This is because they match more than
one thing, making them ambiguous. Unfortunately, this also makes them
a performance cliff. Is this likely to be a problem?
Right now, the system just stashes the type distance into the
same field that levenshtein distance normally goes in. This means exact
query matches show up on top (for example, if you have a function like
`fn nothing(a: Nothing, b: i32)`, then searching for `nothing` will show it
on top even if there's another function with `fn bar(x: Nothing)` that's
technically a closer match in type signature.
Future possibilities
--------------------
It should be possible to adopt more sorting criteria to act as a tie breaker,
which could be determined during unification.
[cuckoo filter]: https://en.wikipedia.org/wiki/Cuckoo_filter
[minhashing]: https://en.wikipedia.org/wiki/MinHash
This function dates back to 9a45c9d7c6 and
seems to have been made obsolete when `addIntoResult` grew the ability to
check the levenshtein distance matching with commit
ba824ec52b.
Change a typo mistake in the-doc-attribute.md
I guess that `Bar` in the section I changed should be `bar` because when I run the program it has its page under struct but bar doesn't have any page.
Unbreak non-unix non-windows bootstrap
Fixes#118862.
#118647 added a new use of std::io::Write that is not conditional on any cfg.
028b6d152e/src/bootstrap/src/bin/main.rs (L134)
```console
error[E0599]: no method named `write_all` found for struct `File` in the current scope
--> src/bin/main.rs:134:21
|
134 | t!(file.write_all(lines.join("\n").as_bytes()));
| ^^^^^^^^^ method not found in `File`
|
= help: items from traits can only be used if the trait is in scope
help: the following trait is implemented but not in scope; perhaps add a `use` for it:
|
8 + use std::io::Write;
|
```
codegen: panic when trying to compute size/align of extern type
The alignment is also computed when accessing a field of extern type at non-zero offset, so we also panic in that case.
Previously `size_of_val` worked because the code path there assumed that "thin pointer" means "sized". But that's not true any more with extern types. The returned size and align are just blatantly wrong, so it seems better to panic than returning wrong results. We use a non-unwinding panic since code probably does not expect size_of_val to panic.
Clean up variables in `search.js`
While reviewing https://github.com/rust-lang/rust/pull/118402, I saw a few small clean ups that were needed, mostly about variables creation.
r? ```@notriddle```
Add rustX check to codeblock attributes lint
We discovered this issue [here](https://github.com/rust-lang/rust/pull/118802#discussion_r1421815943).
I assume that the issue will be present in other places outside of the compiler so it's worth adding a check for it.
First commit is just a small cleanup about variables creation which was a bit strange (at least more than necessary).
r? ```@notriddle```
rustdoc-search: clean up parser
The `c === "="` was redundant when `isSeparatorCharacter` already checks that.
The function `isStopCharacter` and `isEndCharacter` functions did exactly the same thing and have synonymous names. There doesn't seem much point in having both.
On borrow return type, suggest borrowing from arg or owned return type
When we encounter a function with a return type that has an anonymous lifetime with no argument to borrow from, besides suggesting the `'static` lifetime we now also suggest changing the arguments to be borrows or changing the return type to be an owned type.
```
error[E0106]: missing lifetime specifier
--> $DIR/variadic-ffi-6.rs:7:6
|
LL | ) -> &usize {
| ^ expected named lifetime parameter
|
= help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
help: consider using the `'static` lifetime, but this is uncommon unless you're returning a borrowed value from a `const` or a `static`
|
LL | ) -> &'static usize {
| +++++++
help: instead, you are more likely to want to change one of the arguments to be borrowed...
|
LL | x: &usize,
| +
help: ...or alternatively, to want to return an owned value
|
LL - ) -> &usize {
LL + ) -> usize {
|
```
Fix#85843.
Renamings:
- find -> opt_hir_node
- get -> hir_node
- find_by_def_id -> opt_hir_node_by_def_id
- get_by_def_id -> hir_node_by_def_id
Fix rebase changes using removed methods
Use `tcx.hir_node_by_def_id()` whenever possible in compiler
Fix clippy errors
Fix compiler
Apply suggestions from code review
Co-authored-by: Vadim Petrochenkov <vadim.petrochenkov@gmail.com>
Add FIXME for `tcx.hir()` returned type about its removal
Simplify with with `tcx.hir_node_by_def_id`
Let `reuse` look inside git submodules
Changes `collect-license-metadata` and `generate-copyright` so they can now look at the git submodules.
Unfortunately `reuse` chokes on the LLVM submodule - it finds the word "Copyright" or the unicode copyright symbol in all kinds of places, including UTF-8 test cases. The `reuse` tool expressly won't let you ignore folders, so we let it scan everything and then strip out the LLVM sub-folder in post. Instead, we add in a hand-curated list of copyright information gleaned by reading the LLVM codebase carefully, which is stored in `.reuse/dep5` in Debian format where `reuse` can find and use it.
The `.reuse/dep5` continues to track copyright info for files in the tree that do not have SPDX metadata in them (i.e. all of them)
The `c === "="` was redundant when `isSeparatorCharacter` already
checks that.
The function `isStopCharacter` and `isEndCharacter` functions
did exactly the same thing and have synonymous names.
There doesn't seem much point in having both.
Edit target doc template to remove email
We don't really want to communicate with target maintainers via email. GitHub is where everything happens, people should have a GitHub account that can be pinged on issues.
This doesn't necessarily have to be a strict rule, but edit the template to suggest this. The previous template made it look like we care about having an email address, which we do not.
r? ````@davidtwco````
dump bootstrap shims
When making changes to the bootstrap that shouldn't change its behavior, this feature will help developers perform comparisons to check whether the bootstrap behavior has changed or not. As an example, when removing Python from the bootstrap by migrating to Rust, this feature will be super useful for ensuring that the behavior remains unaffected. It will assist me in performing comparisons to verify that the bootstrap behavior and its outputs remains consistent throughout the migration process.
This can also be used for different purposes. For example, allowing CI to dump the shims and upload them so that developers can download them and compare with their local dump to see if CI affects the bootstrap unexpectedly. Or, make CI perform comparisons on specific bootstrap tests to check for behavior changes between the master and PR branches.
