Provide `layout_of` automatically (given tcx + param_env + error handling).
After #88337, there's no longer any uses of `LayoutOf` within `rustc_target` itself, so I realized I could move the trait to `rustc_middle::ty::layout` and redesign it a bit.
This is similar to #88338 (and supersedes it), but at no ergonomic loss, since there's no funky `C: LayoutOf<Ty = Ty>` -> `Ty: TyAbiInterface<C>` generic `impl` chain, and each `LayoutOf` still corresponds to one `impl` (of `LayoutOfHelpers`) for the specific context.
After this PR, this is what's needed to get `trait LayoutOf` (with the `layout_of` method) implemented on some context type:
* `TyCtxt`, via `HasTyCtxt`
* `ParamEnv`, via `HasParamEnv`
* a way to transform `LayoutError`s into the desired error type
* an error type of `!` can be paired with having `cx.layout_of(...)` return `TyAndLayout` *without* `Result<...>` around it, such as used by codegen
* this is done through a new `LayoutOfHelpers` trait (and so is specifying the type of `cx.layout_of(...)`)
When going through this path (and not bypassing it with a manual `impl` of `LayoutOf`), the end result is that only the error case can be customized, the query itself and the success paths are guaranteed to be uniform.
(**EDIT**: just noticed that because of the supertrait relationship, you cannot actually implement `LayoutOf` yourself, the blanket `impl` fully covers all possible context types that could ever implement it)
Part of the motivation for this shape of API is that I've been working on querifying `FnAbi::of_*`, and what I want/need to introduce for that looks a lot like the setup in this PR - in particular, it's harder to express the `FnAbi` methods in `rustc_target`, since they're much more tied to `rustc` concepts.
r? `@nagisa` cc `@oli-obk` `@bjorn3`
Include debug info for the allocator shim
Issue Details:
In some cases it is necessary to generate an "allocator shim" to forward various Rust allocation functions (e.g., `__rust_alloc`) to an underlying function (e.g., `malloc`). However, since this allocator shim is a manually created LLVM module it is not processed via the normal module processing code and so no debug info is generated for it (if debugging info is enabled).
Fix Details:
* Modify the `debuginfo` code to allow creating debug info for a module without a `CodegenCx` (since it is difficult, and expensive, to create one just to emit some debug info).
* After creating the allocator shim add in basic debug info.
Issue Details:
In some cases it is necessary to generate an "allocator shim" to forward various Rust allocation functions (e.g., `__rust_alloc`) to an underlying function (e.g., `malloc`). However, since this allocator shim is a manually created LLVM module it is not processed via the normal module processing code and so no debug info is generated for it (if debugging info is enabled).
Fix Details:
* Modify the `debuginfo` code to allow creating debug info for a module without a `CodegenCx` (since it is difficult, and expensive, to create one just to emit some debug info).
* After creating the allocator shim add in basic debug info.
Fixes#85019
A `SourceFile` created during compilation may have a relative
path (e.g. if rustc itself is invoked with a relative path).
When we write out crate metadata, we convert all relative paths
to absolute paths using the current working direction.
However, the working directory is not included in the crate hash.
This means that the crate metadata can change while the crate
hash remains the same. Among other problems, this can cause a
fingerprint mismatch ICE, since incremental compilation uses
the crate metadata hash to determine if a foreign query is green.
This commit moves the field holding the working directory from
`Session` to `Options`, including it as part of the crate hash.
Name the captured upvars for closures/generators in debuginfo
Previously, debuggers print closures as something like
```
y::main::closure-0 (0x7fffffffdd34)
```
The pointer actually references to an upvar. It is not very obvious, especially for beginners.
It's because upvars don't have names before, as they are packed into a tuple. This PR names the upvars, so we can expect to see something like
```
y::main::closure-0 {_captured_ref__b: 0x[...]}
```
r? `@tmandry`
Discussed at https://github.com/rust-lang/rust/pull/84752#issuecomment-831639489 .
This makes load generation compatible with opaque pointers.
The generation of nontemporal copies still accesses the pointer
element type, as fixing this requires more movement.
- Closures in external crates may get compiled in because of
monomorphization. We should store names of captured variables
in `optimized_mir`, so that they are written into the metadata
file and we can use them to generate debuginfo.
- If there are breakpoints inside closures, the names of captured
variables stored in `optimized_mir` can be used to print them.
Now the name is more precise when disjoint fields are captured.
Previously, debuggers print closures as something like
```
y::main::closure-0 (0x7fffffffdd34)
```
The pointer actually references to an upvar. It is not
very obvious, especially for beginners.
It's because upvars don't have names before, as they
are packed into a tuple. This commit names the upvars,
so we can expect to see something like
```
y::main::closure-0 {_captured_ref__b: 0x[...]}
```
Previously, only the fields would be displayed with no indication of the
variant name. If you already knew the enum was univariant, this was ok
but if the enum was univariant because of layout, for example, a
`Result<T, !>` then it could be very confusing which variant was the
active one.
Previously, directly tagged enums had a `variant$` field which would
show the name of the active variant. We now show the variant using a
`[variant]` synthetic item just like we do for niche-layout enums.
There are several cases where names of types and functions in the debug info are either ambiguous, or not helpful, such as including ambiguous placeholders (e.g., `{{impl}}`, `{{closure}}` or `dyn _'`) or dropping qualifications (e.g., for dynamic types).
Instead, each debug symbol name should be unique and useful:
* Include disambiguators for anonymous `DefPathDataName` (closures and generators), and unify their formatting when used as a path-qualifier vs item being qualified.
* Qualify the principal trait for dynamic types.
* If there is no principal trait for a dynamic type, emit all other traits instead.
* Respect the `qualified` argument when emitting ref and pointer types.
* For implementations, emit the disambiguator.
* Print const generics when emitting generic parameters or arguments.
Additionally, when targeting MSVC, its debugger treats many command arguments as C++ expressions, even when the argument is defined to be a symbol name. As such names in the debug info need to be more C++-like to be parsed correctly:
* Avoid characters with special meaning (`#`, `[`, `"`, `+`).
* Never start a name with `<` or `{` as this is treated as an operator.
* `>>` is always treated as a right-shift, even when parsing generic arguments (so add a space to avoid this).
* Emit function declarations using C/C++ style syntax (e.g., leading return type).
* Emit arrays as a synthetic `array$<type, size>` type.
* Include a `$` in all synthetic types as this is a legal character for C++, but not Rust (thus we avoid collisions with user types).
Previously, we would generate a single struct with the layout of the
dataful variant plus an extra field whose name contained the value of
the niche (this would only really work for things like `Option<&_>`
where we can determine that the `None` case maps to `0` but for enums
that have multiple tag only variants, this doesn't work).
Now, we generate a union of two structs, one which is the layout of the
dataful variant and one which just has a way of reading the
discriminant. We also generate an enum which maps the discriminant value
to the tag only variants.
We also encode information about the range of values which correspond to
the dataful variant in the type name and then use natvis to determine
which union field we should display to the user.
As a result of this change, all niche-layout enums render correctly in
WinDbg and Visual Studio!
This wasn't necessary for msvc and caused issues where different types
with the same name such as different instantiations of `Option<T>` would
have colliding debuginfo. This confused the debugger which would pick
one of the type definitions and use for all types with that name even
though they had different layout.
Remove CrateNum parameter for queries that only work on local crate
The pervasive `CrateNum` parameter is a remnant of the multi-crate rustc idea.
Using `()` as query key in those cases avoids having to worry about the validity of the query key.
Fix `--remap-path-prefix` not correctly remapping `rust-src` component paths and unify handling of path mapping with virtualized paths
This PR fixes#73167 ("Binaries end up containing path to the rust-src component despite `--remap-path-prefix`") by preventing real local filesystem paths from reaching compilation output if the path is supposed to be remapped.
`RealFileName::Named` introduced in #72767 is now renamed as `LocalPath`, because this variant wraps a (most likely) valid local filesystem path.
`RealFileName::Devirtualized` is renamed as `Remapped` to be used for remapped path from a real path via `--remap-path-prefix` argument, as well as real path inferred from a virtualized (during compiler bootstrapping) `/rustc/...` path. The `local_path` field is now an `Option<PathBuf>`, as it will be set to `None` before serialisation, so it never reaches any build output. Attempting to serialise a non-`None` `local_path` will cause an assertion faliure.
When a path is remapped, a `RealFileName::Remapped` variant is created. The original path is preserved in `local_path` field and the remapped path is saved in `virtual_name` field. Previously, the `local_path` is directly modified which goes against its purpose of "suitable for reading from the file system on the local host".
`rustc_span::SourceFile`'s fields `unmapped_path` (introduced by #44940) and `name_was_remapped` (introduced by #41508 when `--remap-path-prefix` feature originally added) are removed, as these two pieces of information can be inferred from the `name` field: if it's anything other than a `FileName::Real(_)`, or if it is a `FileName::Real(RealFileName::LocalPath(_))`, then clearly `name_was_remapped` would've been false and `unmapped_path` would've been `None`. If it is a `FileName::Real(RealFileName::Remapped{local_path, virtual_name})`, then `name_was_remapped` would've been true and `unmapped_path` would've been `Some(local_path)`.
cc `@eddyb` who implemented `/rustc/...` path devirtualisation
Fix debuginfo for generators
First, all fields except the discriminant (including `outer_fields`) should be put into structures inside the variant part, which gives an equivalent layout but offers us much better integration with debuggers.
Second, artificial flags in generator variants should be removed.
- Literally, variants are not artificial. We have `yield` statements, upvars and inner variables in the source code.
- Functionally, we don't want debuggers to suppress the variants. It contains the state of the generator, which is useful when debugging. So they shouldn't be marked artificial.
- Debuggers may use artificial flags to find the active variant. In this case, marking variants artificial will make debuggers not work properly.
Fixes#62572.
Fixes#79009.
And refer https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Debuginfo.20for.20generators.
- Literally, variants are not artificial. We have `yield` statements,
upvars and inner variables in the source code.
- Functionally, we don't want debuggers to suppress the variants. It
contains the state of the generator, which is useful when debugging.
So they shouldn't be marked artificial.
- Debuggers may use artificial flags to find the active variant. In
this case, marking variants artificial will make debuggers not work
properly.
Fixes#79009.
All fields except the discriminant (including `outer_fields`)
should be put into structures inside the variant part, which gives
an equivalent layout but offers us much better integration with
debuggers.
* Use Markdown list syntax and unindent a bit to prevent Markdown
interpreting the nested lists as code blocks
* A few more small typographical cleanups
Use u32 over Option<u32> in DebugLoc
~~Changes `Option<u32>` fields in `DebugLoc` to `Option<NonZeroU32>`. Since the respective fields (`line` and `col`) are guaranteed to be 1-based, this layout optimization is a freebie.~~
EDIT: Changes `Option<u32>` fields in `DebugLoc` to `u32`. As `@bugadani` pointed out, an `Option<NonZeroU32>` is probably an unnecessary layer of abstraction since the `None` variant is always used as `UNKNOWN_LINE_NUMBER` (which is just `0`). Also, `SourceInfo` in `metadata.rs` already uses a `u32` instead of an `Option<u32>` to encode the same information, so I think this change is warranted.
Since `@jyn514` raised some concerns over measuring performance in a similar PR (#82255), does this need a perf run?
Replace const_cstr with cstr crate
This PR replaces the `const_cstr` macro inside `rustc_data_structures` with `cstr` macro from [cstr](https://crates.io/crates/cstr) crate.
The two macros basically serve the same purpose, which is to generate `&'static CStr` from a string literal. `cstr` is better because it validates the literal at compile time, while the existing `const_cstr` does it at runtime when `debug_assertions` is enabled. In addition, the value `cstr` generates can be used in constant context (which is seemingly not needed anywhere currently, though).
As part of the effort to implement split dwarf debug info, we ended up
setting the compile unit location to the output directory rather than
the source directory. Furthermore, it seems like we failed to remap the
prefixes for this as well!
The desired behaviour is to instead set the `DW_AT_GNU_dwo_name` to a
path relative to compiler's working directory. This still allows
debuggers to find the split dwarf files, while not changing the
behaviour of the code that is compiling with regular debug info, and not
changing the compiler's behaviour with regards to reproducibility.
Fixes#82074
