[MIR] Deaggregate structs to enable further optimizations
Currently, we generate MIR like:
```
tmp0 = ...;
tmp1 = ...;
tmp3 = Foo { a: ..., b: ... };
```
This PR implements "deaggregation," i.e.:
```
tmp3.0 = ...
tmp3.1 = ...
```
Currently, the code only deaggregates structs, not enums. My understanding is that we do not have MIR to set the discriminant of an enum.
Better attribute and metaitem encapsulation throughout the compiler
This PR refactors most (hopefully all?) of the `MetaItem` interactions outside of `libsyntax` (and a few inside) to interact with MetaItems through the provided traits instead of directly creating / destruct / matching against them. This is a necessary first step to eventually converting `MetaItem`s to internally use `TokenStream` representations (which will make `MetaItem` interactions much nicer for macro writers once the new macro system is in place).
r? @nrc
Convert built-in targets to JSON
Convert the built-in targets to JSON to ensure that the JSON parser is always fully featured. This follows on #32988 and #32847. The PR includes a number of extra commits that are just intermediate changes necessary for bisectibility and the ability to prove correctness of the change.
We used to use `Name`, but the session outlives the tokenizer, which
means that attempts to read this field after trans has complete
otherwise panic. All reads want an `InternedString` anyhow.
Since we can know which targets are instantiable on a particular host,
it does not make sense to list invalid targets in the target print code.
Filter the list of targets to only include the targets that can be
instantiated.
Simplify librustc_errors
This is part 2 of the error crate refactor, starting with #34403.
In this refactor, I focused on slimming down the error crate to fewer moving parts. As such, I've removed quite a few parts and replaced the with simpler, straight-line code. Specifically, this PR:
* Removes BasicEmitter
* Remove emit from emitter, leaving emit_struct
* Renames emit_struct to emit
* Removes CoreEmitter and focuses on a single Emitter
* Implements the latest changes to error format RFC (#1644)
* Removes (now-unused) code in emitter.rs and snippet.rs
* Moves more tests to the UI tester, removing some duplicate tests in the process
There is probably more that could be done with some additional refactoring, but this felt like it was getting to a good state.
r? @alexcrichton cc: @Manishearth (as there may be breaking changes in stuff I removed/changed)
Simplify the macro hygiene algorithm
This PR removes renaming from the hygiene algorithm and treats differently marked identifiers as unequal.
This change makes the scope of identifiers in `macro_rules!` items empty. That is, identifiers in `macro_rules!` definitions do not inherit any semantics from the `macro_rules!`'s scope.
Since `macro_rules!` macros are items, the scope of their identifiers "should" be the same as that of other items; in particular, the scope should contain only items. Since all items are unhygienic today, this would mean the scope should be empty.
However, the scope of an identifier in a `macro_rules!` statement today is the scope that the identifier would have if it replaced the `macro_rules!` (excluding anything unhygienic, i.e. locals only).
To continue to support this, this PR tracks the scope of each `macro_rules!` and uses it in `resolve` to ensure that an identifier expanded from a `macro_rules!` gets a chance to resolve to the locals in the `macro_rules!`'s scope.
This PR is a pure refactoring. After this PR,
- `syntax::ext::expand` is much simpler.
- We can expand macros in any order without causing problems for hygiene (needed for macro modularization).
- We can deprecate or remove today's `macro_rules!` scope easily.
- Expansion performance improves by 25%, post-expansion memory usage decreases by ~5%.
- Expanding a block is no longer quadratic in the number of `let` statements (fixes#10607).
r? @nrc
Add x86 intrinsics for bit manipulation (BMI 1.0, BMI 2.0, and TBM).
This PR adds the LLVM x86 intrinsics for the bit manipulation instruction sets (BMI 1.0, BMI 2.0, and TBM).
The objective of this pull-request is to allow building a library that implements all the algorithms offered by those instruction sets, using compiler intrinsics for the targets that support them (by means of `target_feature`).
The target features added are:
- `bmi`: Bit Manipulation Instruction Set 1.0, available in Intel >= Haswell and AMD's >= Jaguar/Piledriver,
- `bmi2`: Bit Manipulation Instruction Set 2.0, available in Intel >= Haswell and AMD's >= Excavator,
- `tbm`: Trailing Bit Manipulation, available only in AMD's Piledriver (won't be available in newer CPUs).
The intrinsics added are:
- BMI 1.0:
- `bextr`: Bit field extract (with register).
- BMI 2.0:
- `bzhi`: Zero high bits starting with specified bit position.
- `pdep`: Parallel bits deposit.
- `pext`: Parallel bits extract.
- TBM:
- `bextri`: Bit field extract (with immediate).
To allow these braced macro invocation, this PR removes the optional expression from `ast::Block` and instead uses a `StmtKind::Expr` at the end of the statement list.
Currently, braced macro invocations in blocks can expand into statements (and items) except when they are last in a block, in which case they can only expand into expressions.
For example,
```rust
macro_rules! make_stmt {
() => { let x = 0; }
}
fn f() {
make_stmt! {} //< This is OK...
let x = 0; //< ... unless this line is commented out.
}
```
Fixes#34418.
MIR cleanups and predecessor cache
This PR cleans up a few things in MIR and adds a predecessor cache to allow graph algorithms to be run easily.
r? @nikomatsakis
