integrate anon dep nodes into trait selection
Use anonymous nodes for trait selection. In all cases, we use the same basic "memoization" strategy:
- Store the `DepNodeIndex` in the slot along with value.
- If value is present, return it, and add a read of the dep-node-index.
- Else, start an anonymous task, and store resulting node.
We apply this strategy to a number of caches in trait selection:
- The "trans" caches of selection and projection
- The "evaluation" cache
- The "candidate selection" cache
In general, for our cache strategy to be "dep-correct", the computation of the value is permitted to rely on the *value in the key* but nothing else. The basic argument is this: in order to look something up, you have to produce the key, and to do that you must have whatever reads were needed to create the key. Then, you get whatever reads were further needed to produce the value. But if the "closure" that produced the value made use of *other* environmental data, not derivable from the key, that would be bad -- but that would **also** suggest that the cache is messed up (though it's not proof).
The structure of these caches do not obviously prove that the correctness criteria are met, and I aim to address that in further refactorings. But I *believe* it to be the case that, if we assume that the existing caches are correct, there are also no dependency failures (in other words, if there's a bug, it's a pre-existing one). Specifically:
- The trans caches: these take as input just a `tcx`, which is "by definition" not leaky, the `trait-ref` etc, which is part of the key, and sometimes a span (doesn't influence the result). So they seem fine.
- The evaluation cache:
- This computation takes as input the "stack" and has access to the infcx.
- The infcx is a problem -- would be better to take the tcx -- and this is exactly one of the things I plan to improve in later PRs. Let's ignore it for now. =)
- The stack itself is also not great, in that the *key* only consists of the top-entry in the stack.
- However, the stack can cause a problem in two ways:
- overflow (we panic)
- cycle check fails (we do not update the cache, I believe)
- The candidate selection cache:
- as before, takes the "stack" and has access to the infcx.
- here it is not as obvious that we avoid caching stack-dependent computations. However, to the extent that we do, this is a pre-existing bug, in that we are making cache entries we shouldn't.
- I aim to resolve this by -- following the chalk-style of evaluation -- merging candidate selection and evaluation.
- The infcx is a problem -- would be better to take the tcx -- and this is exactly one of the things I plan to improve in later PRs. Let's ignore it for now. =)
- The stack itself is also not great, in that the *key* only consists of the top-entry in the stack.
- Moreover, the stack would generally just introduce ambiguities and errors anyhow, so that lessens the risk.
Anyway, the existing approach to handle dependencies in the trait code carries the same risks or worse, so this seems like a strict improvement!
r? @michaelwoerister
cc @arielb1
Refactor: {Lvalue,Rvalue,Operand}::ty only need the locals' types, not the full &Mir
I am writing code that needs to call these `ty` methods while mutating MIR -- which is impossible with the current API.
Even with the refactoring the situation is not great: I am cloning the `local_decls` and then passing the clone to the `ty` methods. I have to clone because `Mir::basic_blocks_mut` borrows the entire `Mir` including the `local_decls`. But even that is better than not being able to get these types at all...
Cc @nikomatsakis
On at least RHEL6 there is a segfault caused by the older ld.so version
when BIND_NOW is used, so use partial RELRO by default on ppc64
architectures for now.
Signed-off-by: Johannes Löthberg <johannes@kyriasis.com>
Split old and experimental wasm builders
#42784 introduced configuration errors in the wasm builder by mixing different versions of the tools. This PR separates the wasm32-unknown-emscripten and wasm32-experimental-emscripten builders to resolve these errors.
This adds a pretty contrived example of the usage of fmt::Error. I am
very open to suggestions for a better one.
I have also highlighted the fmt::Error vs std::error::Error.
r? @steveklabnik
Notably pull in an update to the `jobserver` crate to have Cargo set the
`CARGO_MAKEFLAGS` environment variable instead of the `MAKEFLAGS` environment
variable.
Implement fs::rename in sys::redox
This uses a simple implementation of copy + unlink. Redox does not have a rename or link system call for a faster implementation.
Add the Code of Conduct to the repository.
https://github.com/rust-lang/rust/community currently shows that we have
no code of conduct. This will make it understand.
This is an exact copy of the page on the website.
update .mailmap
It's nice to have an up-to-date .mailmap so that contributor listings (like those provided by `git shortlog` or http://thanks.rust-lang.org/) don't split the same author's contributions across two or more variations of their name.
Affected contributors—
@Aaronepower (3 commits as "Aaron Power", 1 as "Aaronepower")
@djrollins (5 commits as "Daniel J Rollins", 1 as "Daniel Rollins")
@eddyb (345 commits as "Eduard-Mihai Burtescu", 678 as "Eduard Burtescu", assuming former is canonical based on recency and GitHub profile display name)
@edunham (1 more recent commit contradicts existing .mailmap entry)
@GuillaumeGomez (942 commits as "Guillaume Gomez", 55 commits as "ggomez", 22 commits as "GuillaumeGomez")
@jonathandturner (362 commits as "Jonathan Turner", 1 as "jonathandturner")
@Mark-Simulacrum (248 commits as "Mark Simulacrum", 97 "Mark-Simulacrum")
@fiveop (1 commit each as "Philipp Matthias Schäfer" and "Philipp Matthias Schaefer", assuming former is canonical based on GitHub profile display name)
@shyaamsundhar (1 commit as "Shyam Sundar B", 3 as ShyamSundarB, assuming former is canonical based on recency)
@steveklabnik (1634 commits as "Steve Klabnik", 41 as "steveklabnik")
Document what happens on failure in path ext is_file is_dir
r? @steveklabnik
Also, what other ways could there be an error that gets discarded and returns false? Should we list them all? Should we say that any errors trying to access the metadata at that path causes it to return false, even if there might be a file or directory there?
Should I add a See also link to the original functions that do return Results?
Thread local try with
https://github.com/rust-lang/rfcs/pull/2030 was turned into this PR (the RFC was closed, but it looks like just a PR should be good).
See also: state stabilization issue: #27716
`try_with` is used in two places in std: stdio and thread_info. In stdio, it would be better if the result was passed to the closure, but in thread_info, it's better as is where the result is returned from the function call. I'm not sure which is better, but I prefer the current way as it better represents the scope.
Updated docker images to share scripts
Attempts to resolve#42201. I managed to pull out five scripts (android-base-apt-get, ubuntu16-apt-get, make3, rustbuild-setup, and crosstool-ng). Let me know if there's more I can do or if I should change some names.
r? @malbarbo
https://github.com/rust-lang/rust/community currently shows that we have
no code of conduct. This will make it understand.
This is an exact copy of the page on the website.
