THis significantly complicates `NaiveLayout` logic, but is necessary to
ensure that bounds like `NonNull<T>: PointerLike` hold in generic
contexts.
Also implement exact layout computation for structs.
The style guide inconsistently used language like "there should be a
space" or "it should be on its own line", or "may be written on a single
line", for things that are required components of the default Rust
style. "should" and especially "may" come across as optional. While the
style guide overall now has a statement at the top that the default
style itself is a *recommendation*, the *definition* of the default
style should not be ambiguous about what's part of the default style.
Rewrite language in the style guide to only use "should" and "may" and
similar for truly optional components of the style (e.g. things a tool
cannot or should not enforce in its default configuration).
In their place, either use "must", or rewrite in imperative style ("put
a space", "start it on the same line"). The latter also substantially
reduces the use of passive voice.
This is a purely editorial change, and does not affect the semantic
definition of the Rust style.
The style guide requires a trailing comma on where clause components,
but then gives an example that doesn't include one. Add the missing
trailing comma.
Get `!nonnull` metadata on slice iterators, without `assume`s
This updates the non-ZST paths to read the end pointer through a pointer-to-`NonNull`, so that they all get `!nonnull` metadata.
That means that the last `assume(!ptr.is_null())` can be deleted, without impacting codegen -- the codegen tests confirm the LLVM-IR ends up exactly the same as before.
Always const-prop scalars and scalar pairs
This removes some complexity from the pass.
The limitation to propagate ScalarPairs only for tuple comes from https://github.com/rust-lang/rust/pull/67015, when ScalarPair constant were modeled using `Rvalue::Aggregate`. Nowadays, we use `ConstValue::ByRef`, which does not care about the underlying type.
The justification for not propagating in all cases was perf. This seems not to be a clear cut any more: https://github.com/rust-lang/rust/pull/113858#issuecomment-1642396746
Refactor vtable encoding and optimize it for the case of multiple marker traits
This PR does two things
- Refactor `prepare_vtable_segments` (this was motivated by the other change, `prepare_vtable_segments` was quite hard to understand and while trying to edit it I've refactored it)
- Mostly remove `loop`s labeled `break`s/`continue`s whenever there is a simpler solution
- Also use `?`
- Make vtable format a bit more efficient wrt to marker traits
- See the tests for an example
Fixes https://github.com/rust-lang/rust/issues/113840
cc `@crlf0710`
----
Review wise it's probably best to review each commit individually, as then it's more clear why the refactoring is correct.
I can split the last two commits (which change behavior) into a separate PR if it makes reviewing easier
Querify unused trait check.
This code transitively loads information for all bodies, and from resolutions. As it does not return a value, it should be beneficial to have it as a query.
