polymorphize: unevaluated constants
This PR makes polymorphization visit the promoted MIR of unevaluated constants with available promoted MIR instead of visiting the substitutions of that constant - which will mark all of the generic parameters as used; in addition polymorphization will now visit non-promoted unevaluated constants rather than visit their substs.
r? @lcnr
Emit == null instead of <= null for niche check
When the niche maximum is zero, emit a "== zero" check instead of a "<= zero" check. In particular, this avoids the awkward case of "<= null". While LLVM does canonicalize this to "== null", this apparently doesn't happen for constant expressions, leading to the issue in #74425. While that can be addressed on the LLVM side, it still seems prudent to emit sensible IR here, because this will allow null checks to be optimized earlier in the pipeline.
Fixes#74425.
When the niche maximum is zero, emit a "== zero" check instead of
a "<= zero" check. In particular, this avoid the awkward case of
"<= null". While LLVM does canonicalize this to "!= null", this
appently doesn't happen for constant expressions, leading to the
issue in #74425. While that can be addressed on the LLVM side, it
still seems prudent to emit sensible IR here, because this will
allow null checks to be optimized earlier in the pipeline.
Fixes#74425.
make MaybeUninit::as_(mut_)ptr const
I think it was just an oversight that they are not const yet.
I also changed their implementation as the old one created references to uninitialized memory.^^
Display elided lifetime for non-reference type in doc
In edition 2018 we encourage writing `<'_>` explicitly, so rustdoc should display like such as well.
Fixes#75225
~~Somehow when I run the compiled rustdoc using `cargo +stage2 doc` on other crates, it correctly produces `<'_>`, but I couldn't get the std doc to do the same with `./x.py doc --stage 2`. Might this be related to the recent change to x.py about how the doc is built?~~
Don't call a function in function-arguments-naked.rs
Fixes#75096
It's U.B. to use anything other than inline assmebling in a naked
function. Fortunately, the `#break` directive works fine without
anything in the function body.
By moving `{known,used}_attrs` from `SessionGlobals` to `Session`. This
means they are accessed via the `Session`, rather than via TLS. A few
`Attr` methods and `librustc_ast` functions are now methods of
`Session`.
All of this required passing a `Session` to lots of functions that didn't
already have one. Some of these functions also had arguments removed, because
those arguments could be accessed directly via the `Session` argument.
`contains_feature_attr()` was dead, and is removed.
Some functions were moved from `librustc_ast` elsewhere because they now need
to access `Session`, which isn't available in that crate.
- `entry_point_type()` --> `librustc_builtin_macros`
- `global_allocator_spans()` --> `librustc_metadata`
- `is_proc_macro_attr()` --> `Session`
Implement the `min_const_generics` feature gate
Implements both https://github.com/rust-lang/lang-team/issues/37 and https://github.com/rust-lang/compiler-team/issues/332.
Adds the new feature gate `#![feature(min_const_generics)]`.
This feature gate adds the following limitations to using const generics:
- generic parameters must only be used in types if they are trivial. (either `N` or `{ N }`)
- generic parameters must be either integers, `bool` or `char`.
We do allow arbitrary expressions in associated consts though, meaning that the following is allowed,
even if `<[u8; 0] as Foo>::ASSOC` is not const evaluatable.
```rust
trait Foo {
const ASSOC: usize;
}
impl<const N: usize> Foo for [u8; N] {
const ASSOC: usize = 64 / N;
}
```
r? @varkor cc @eddyb @withoutboats
Prevent `__rust_begin_short_backtrace` frames from being tail-call optimised away
I've stumbled across some situations where there (unexpectedly) was no `__rust_begin_short_backtrace` frame on the stack during unwinding.
On closer examination, it appeared that the calls to that function had been tail-call optimised away.
This PR follows [@bjorn3's suggestion on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Disabling.20tail.20call.20optimisation.3F/near/205699133), by adding calls to `black_box` that hint to rustc not to perform TCO.
Fixes#47429
instance: polymorphize upvar closures/generators
This PR modifies how instances are polymorphized so that closures and generators have any closures or generators captured within their upvars also polymorphized.
With the new symbol mangling, a fully polymorphised closure will produce the same symbol regardless of what it was instantiated with. However, when that polymorphised closure captures another closure as an upvar, then the type of that other closure in the upvar substitution wouldn't have been polymorphised. The other closure will still refer to the initial substitutions. Therefore, the polymorphised closure will end up hashing differently but producing the same symbol - triggering `assert_symbols_are_distinct` in MIR partitioning. The old mangling scheme had a hash at the end that meant this didn't happen (this would still have been an issue, we just didn't have a way to notice).
See [this Zulip discussion for further elaboration](https://rust-lang.zulipchat.com/#narrow/stream/216091-t-compiler.2Fwg-polymorphization/topic/symbol.20mangling.20v0.20.E2.9C.95.20polymorphisation/near/206152008).
r? @eddyb
cc @lcnr
This commit avoids unnecessary calls to `mk_closure` and `mk_generator`
by checking if the polymorphized substs match the original substs.
Signed-off-by: David Wood <david@davidtw.co>
This commit adds a `MAY_POLYMORPHIZE` which checks for closures and
generators so that polymorphization of substs does not need to traverse
every substs.
Signed-off-by: David Wood <david@davidtw.co>
