Rename `bitcode-in-rlib` option to `embed-bitcode`
This commit finishes work first pioneered in #70458 and started in #71528.
The `-C bitcode-in-rlib` option, which has not yet reached stable, is
renamed to `-C embed-bitcode` since that more accurately reflects what
it does now anyway. Various tests and such are updated along the way as
well.
This'll also need to be backported to the beta channel to ensure we
don't accidentally stabilize `-Cbitcode-in-rlib` as well.
This commit finishes work first pioneered in #70458 and started in #71528.
The `-C bitcode-in-rlib` option, which has not yet reached stable, is
renamed to `-C embed-bitcode` since that more accurately reflects what
it does now anyway. Various tests and such are updated along the way as
well.
This'll also need to be backported to the beta channel to ensure we
don't accidentally stabilize `-Cbitcode-in-rlib` as well.
Allow `Downcast` projections unconditionally in const-checking
`ProjectionElem::Downcast` sounds scary, but it's really just the projection we use to access a particular enum variant. They usually appear in the lowering of a `match` statement, so they have been associated with control flow in const-checking, but they don't do any control flow by themselves. We already have a HIR pass that looks for `if` and `match` (even ones that have 1 or fewer reachable branches). That pass is double-checked by a MIR pass that looks for `SwitchInt`s and `FakeRead`s for match scrutinees. In my opinion, there's no need to look for `Downcast` as well.
r? @oli-obk
MIR dump: print pointers consistently with Miri output
This makes MIR allocation dump pointer printing consistent with Miri output: both use hexadecimal offsets with a `0x` prefix. To save some space, MIR dump replaces the `alloc` prefix by `a` when necessary.
I also made AllocId/Pointer printing more consistent in their Debug/Display handling, and adjusted Display printing for Scalar a bit to avoid using decimal printing when we do not know the sign with which to interpret the value (IMO using decimal then is misleading).
Rename Unique::empty() -> Unique::dangling()
A `FIXME` comment in `src/libcore/ptr/unique.rs` suggested refactoring `Unique::empty()` to `Unique::dangling()` which this PR does.
extend NLL checker to understand `'empty` combined with universes
This PR extends the NLL region checker to understand `'empty` combined with universes. In particular, it means that the NLL region checker no longer considers `exists<R2> { forall<R1> { R1: R2 } }` to be provable. This is work towards https://github.com/rust-lang/rust/issues/59490, but we're not all the way there. One thing in particular it does not address is error messages.
The modifications to the NLL region inference code turned out to be simpler than expected. The main change is to require that if `R1: R2` then `universe(R1) <= universe(R2)`.
This constraint follows from the region lattice (shown below), because we assume then that `R2` is "at least" `empty(Universe(R2))`, and hence if `R1: R2` (i.e., `R1 >= R2` on the lattice) then `R1` must be in some universe that can name `'empty(Universe(R2))`, which requires that `Universe(R1) <= Universe(R2)`.
```
static ----------+-----...------+ (greatest)
| | |
early-bound and | |
free regions | |
| | |
scope regions | |
| | |
empty(root) placeholder(U1) |
| / |
| / placeholder(Un)
empty(U1) -- /
| /
... /
| /
empty(Un) -------- (smallest)
```
I also made what turned out to be a somewhat unrelated change to add a special region to represent `'empty(U0)`, which we use (somewhat hackily) to indicate well-formedness checks in some parts of the compiler. This fixes#68550.
I did some investigation into fixing the error message situation. That's a bit trickier: the existing "nice region error" code around placeholders relies on having better error tracing than NLL currently provides, so that it knows (e.g.) that the constraint arose from applying a trait impl and things like that. I feel like I was hoping *not* to do such fine-grained tracing in NLL, and it seems like we...largely...got away with that. I'm not sure yet if we'll have to add more tracing information or if there is some sort of alternative.
It's worth pointing out though that I've not kind of shifted my opinion on whose job it should be to enforce lifetimes: I tend to think we ought to be moving back towards *something like* the leak-check (just not the one we *had*). If we took that approach, it would actually resolve this aspect of the error message problem, because we would be resolving 'higher-ranked errors' in the trait solver itself, and hence we wouldn't have to thread as much causal information back to the region checker. I think it would also help us with removing the leak check while not breaking some of the existing crates out there.
Regardless, I think it's worth landing this change, because it was relatively simple and it aligns the set of programs that NLL accepts with those that are accepted by the main region checker, and hence should at least *help* us in migration (though I guess we still also have to resolve the existing crates that rely on leak check for coherence).
r? @matthewjasper
Miri: better document and fix dynamic const pattern soundness checks
https://github.com/rust-lang/const-eval/issues/42 got me thinking about soundness for consts being used in patterns, and I found a hole in our existing dynamic checks: a const referring to a mutable static *in a different crate* was not caught. This PR fixes that. It also adds some comments that explain which invariants are crucial for soundness of const-patterns.
Curiously, trying to weaponize this soundness hole failed: pattern matching compilation ICEd when encountering the cross-crate static, saying "expected allocation ID alloc0 to point to memory". I don't know why that would happen, statics *should* be entirely normal memory for pattern matching to access.
r? @oli-obk
Cc @rust-lang/wg-const-eval
Suggest deref when coercing `ty::Ref` to `ty::RawPtr`
Fixes#32122
Currently we do autoderef when casting `ty::Ref` ->`ty::Ref`, but we don't autoderef when casting `ty::Ref` -> `ty::RawPtr`. This PR make the compiler suggests deref when coercing `ty::Ref` to `ty::RawPtr`
rustc: fix check_attr() for methods, closures and foreign functions
This fixes an issue that previously turned up for methods in https://github.com/rust-lang/rust/pull/69274, but also exists for closures and foreign function: `check_attr` does not call `codegen_fn_attrs()` for these types when it should, meaning that incorrectly used function attributes are not diagnosed without codegen.
The issue affects our UI tests, as they run with `--emit=metadata` by default, but as it turns out, this is not the only case: Function attributes are not checked on any dead code without this fix!
This makes the fix a **breaking change**. The following very silly Rust programs compiles fine on stable Rust when it should not, which is fixed by this PR.
```rust
fn main() {
#[target_feature(enable = "sse2")]
|| {};
}
```
I assume any real-world program which may trigger this issue would at least emit a dead code warning, but of course that is no guarantee that such code does not exist...
Fixes#70307
Store LLVM bitcode in object files, not compressed
This commit is an attempted resurrection of #70458 where LLVM bitcode
emitted by rustc into rlibs is stored into object file sections rather
than in a separate file. The main rationale for doing this is that when
rustc emits bitcode it will no longer use a custom compression scheme
which makes it both easier to interoperate with existing tools and also
cuts down on compile time since this compression isn't happening.
The blocker for this in #70458 turned out to be that native linkers
didn't handle the new sections well, causing the sections to either
trigger bugs in the linker or actually end up in the final linked
artifact. This commit attempts to address these issues by ensuring that
native linkers ignore the new sections by inserting custom flags with
module-level inline assembly.
Note that this does not currently change the API of the compiler at all.
The pre-existing `-C bitcode-in-rlib` flag is co-opted to indicate
whether the bitcode should be present in the object file or not.
Finally, note that an important consequence of this commit, which is also
one of its primary purposes, is to enable rustc's `-Clto` bitcode
loading to load rlibs produced with `-Clinker-plugin-lto`. The goal here
is that when you're building with LTO Cargo will tell rustc to skip
codegen of all intermediate crates and only generate LLVM IR. Today
rustc will generate both object code and LLVM IR, but the object code is
later simply thrown away, wastefully.
This commit is an attempted resurrection of #70458 where LLVM bitcode
emitted by rustc into rlibs is stored into object file sections rather
than in a separate file. The main rationale for doing this is that when
rustc emits bitcode it will no longer use a custom compression scheme
which makes it both easier to interoperate with existing tools and also
cuts down on compile time since this compression isn't happening.
The blocker for this in #70458 turned out to be that native linkers
didn't handle the new sections well, causing the sections to either
trigger bugs in the linker or actually end up in the final linked
artifact. This commit attempts to address these issues by ensuring that
native linkers ignore the new sections by inserting custom flags with
module-level inline assembly.
Note that this does not currently change the API of the compiler at all.
The pre-existing `-C bitcode-in-rlib` flag is co-opted to indicate
whether the bitcode should be present in the object file or not.
Finally, note that an important consequence of this commit, which is also
one of its primary purposes, is to enable rustc's `-Clto` bitcode
loading to load rlibs produced with `-Clinker-plugin-lto`. The goal here
is that when you're building with LTO Cargo will tell rustc to skip
codegen of all intermediate crates and only generate LLVM IR. Today
rustc will generate both object code and LLVM IR, but the object code is
later simply thrown away, wastefully.
Suggest `into` instead of `try_into` if possible with int types
If it is possible to convert an integer type into another using `into`, don't suggest `try_into`. This commit changes the suggested method to convert from one integer type to another for the following cases:
- u{n} -> i{m} where n < m
- u8 -> isize
- i{n} -> isize where n <= 16
- u{n} -> usize where n <= 16
Fixes#71580
Const qualification for `StructuralEq`
Furthers #62411. Resolves#62614.
The goal of this PR is to implement the logic in #67088 on the MIR instead of the HIR. It uses the `Qualif` trait to track `StructuralPartialEq`/`StructuralEq` in the final value of a `const`. Then, if we encounter a constant during HAIR lowering whose value may not be structurally matchable, we emit the `indirect_structural_match` lint.
This PR contains all the tests present in #67088 and emits the proper warnings for the corner cases. This PR does not handle #65466, which would require that we be [more aggressive](42abbd8878/src/librustc_mir_build/hair/pattern/const_to_pat.rs (L126-L130)) when checking matched types for `PartialEq`. I think that should be done separately.
Because this works on MIR and uses dataflow, this PR should accept more cases than #67088. Notably, the qualifs in the final value of a const are encoded cross-crate, so matching on a constant whose value is defined in another crate to be `Option::<TyWithCustomEqImpl>::None` should work. Additionally, if a `const` has branching/looping, we will only emit the warning if any possible control flow path could result in a type with a custom `PartialEq` impl ending up as the final value of a `const`. I'm not sure how #67088 handled this.
AFAIK, it's not settled that these are the semantics we actually want: it's just how the `Qualif` framework happens to work. If the cross-crate part is undesirable, it would be quite easy to change the result of `mir_const_qualif().custom_eq` to `true` before encoding it in the crate metadata. This way, other crates would have to assume that all publicly exported constants may not be safe for matching.
r? @pnkfelix
cc @eddyb
