Add common lint tools doc
This PR starts adding some documentation about linting tools.
`Retrieving all methods of a type` is not covered at this time.
fixes partially: #3843
changelog: none
option_option test case #4298
Adds regression test case for #4298.
The bug seems still present although rust Playground said otherwise.
changelog: none
new_without_default: do not suggest deriving
---
changelog: do not suggest deriving `Default` in `new_without_default`
This commit changes the behavior of the `new_without_default` lint to not suggest deriving `Default`. This suggestion is misleading if the `new` implementation does something different than what a derived `Default` implementation would do, because then the two methods would not be equivalent.
Instead, the `can_derive_default` check is removed, and we always suggest implementing `Default` in terms of `new()`.
Clarify the documentation of the `unnecessary_mut_passed` lint
fixes#5433 by replacing "giving" with "passing"
changelog: Clarifies documentation for `unnecessary_mut_passed`
Add to the list of words clippy::doc_markdown ignores
"TypeScript" is the only one of these I actually ran into organically; I can remove the others if they're too much.
changelog: Add to the list of words `clippy::doc_markdown` ignores
Downgrade `match_wild_err_arm` to pedantic and update help messages
Hi,
This fixes#3688 and downgrades `match_wild_err_arm` to pedantic.
There are a lot of different reasons in that issue, for me the biggest are:
1. Rust's errors aren't like Java's exceptions because they're type safe and in most cases the type of error can't change by itself.
2. Sometimes matching can be more ergonomic, and before the `track_caller` feature got introduced it was actually easier to track the panic location with explicit `panic!` than with `expect`.
Currently clippy is failing to build because of a breaking change in https://github.com/rust-lang/rust/pull/69171 I tried fixing it but it is too complex for my little knowledge of clippy and rustc so I'll leave that to people who know what they're doing :)
Another thing, if rustc is breaking clippy a lot then maybe it's better to use something like `miri` does, where it's hard codes the latest tested rustc commit and they keep bumping it, that way when you develop locally it should work even if there was a breaking change (https://github.com/rust-lang/miri/blob/master/rustup-toolchain#L23-L29)
changelog: Downgrade `match_wild_err_arm` to pedantic
New lint: `match_wildcard_for_single_variants`
changelog: Added a new lint match_wildcard_for_single_variants to warn on enum matches where a wildcard is used to match a single variant
Closes#5556
Rustup
@oli-obk Do you know, how we can enforce (ui-)tests pass in rust-lang/rust for Clippy? I can open a PR for this, if you tell me what would be necessary for this.
changelog: none
Implement new asm! syntax from RFC 2850
This PR implements the new `asm!` syntax proposed in https://github.com/rust-lang/rfcs/pull/2850.
# Design
A large part of this PR revolves around taking an `asm!` macro invocation and plumbing it through all of the compiler layers down to LLVM codegen. Throughout the various stages, an `InlineAsm` generally consists of 3 components:
- The template string, which is stored as an array of `InlineAsmTemplatePiece`. Each piece represents either a literal or a placeholder for an operand (just like format strings).
```rust
pub enum InlineAsmTemplatePiece {
String(String),
Placeholder { operand_idx: usize, modifier: Option<char>, span: Span },
}
```
- The list of operands to the `asm!` (`in`, `[late]out`, `in[late]out`, `sym`, `const`). These are represented differently at each stage of lowering, but follow a common pattern:
- `in`, `out` and `inout` all have an associated register class (`reg`) or explicit register (`"eax"`).
- `inout` has 2 forms: one with a single expression that is both read from and written to, and one with two separate expressions for the input and output parts.
- `out` and `inout` have a `late` flag (`lateout` / `inlateout`) to indicate that the register allocator is allowed to reuse an input register for this output.
- `out` and the split variant of `inout` allow `_` to be specified for an output, which means that the output is discarded. This is used to allocate scratch registers for assembly code.
- `sym` is a bit special since it only accepts a path expression, which must point to a `static` or a `fn`.
- The options set at the end of the `asm!` macro. The only one that is particularly of interest to rustc is `NORETURN` which makes `asm!` return `!` instead of `()`.
```rust
bitflags::bitflags! {
pub struct InlineAsmOptions: u8 {
const PURE = 1 << 0;
const NOMEM = 1 << 1;
const READONLY = 1 << 2;
const PRESERVES_FLAGS = 1 << 3;
const NORETURN = 1 << 4;
const NOSTACK = 1 << 5;
}
}
```
## AST
`InlineAsm` is represented as an expression in the AST:
```rust
pub struct InlineAsm {
pub template: Vec<InlineAsmTemplatePiece>,
pub operands: Vec<(InlineAsmOperand, Span)>,
pub options: InlineAsmOptions,
}
pub enum InlineAsmRegOrRegClass {
Reg(Symbol),
RegClass(Symbol),
}
pub enum InlineAsmOperand {
In {
reg: InlineAsmRegOrRegClass,
expr: P<Expr>,
},
Out {
reg: InlineAsmRegOrRegClass,
late: bool,
expr: Option<P<Expr>>,
},
InOut {
reg: InlineAsmRegOrRegClass,
late: bool,
expr: P<Expr>,
},
SplitInOut {
reg: InlineAsmRegOrRegClass,
late: bool,
in_expr: P<Expr>,
out_expr: Option<P<Expr>>,
},
Const {
expr: P<Expr>,
},
Sym {
expr: P<Expr>,
},
}
```
The `asm!` macro is implemented in librustc_builtin_macros and outputs an `InlineAsm` AST node. The template string is parsed using libfmt_macros, positional and named operands are resolved to explicit operand indicies. Since target information is not available to macro invocations, validation of the registers and register classes is deferred to AST lowering.
## HIR
`InlineAsm` is represented as an expression in the HIR:
```rust
pub struct InlineAsm<'hir> {
pub template: &'hir [InlineAsmTemplatePiece],
pub operands: &'hir [InlineAsmOperand<'hir>],
pub options: InlineAsmOptions,
}
pub enum InlineAsmRegOrRegClass {
Reg(InlineAsmReg),
RegClass(InlineAsmRegClass),
}
pub enum InlineAsmOperand<'hir> {
In {
reg: InlineAsmRegOrRegClass,
expr: Expr<'hir>,
},
Out {
reg: InlineAsmRegOrRegClass,
late: bool,
expr: Option<Expr<'hir>>,
},
InOut {
reg: InlineAsmRegOrRegClass,
late: bool,
expr: Expr<'hir>,
},
SplitInOut {
reg: InlineAsmRegOrRegClass,
late: bool,
in_expr: Expr<'hir>,
out_expr: Option<Expr<'hir>>,
},
Const {
expr: Expr<'hir>,
},
Sym {
expr: Expr<'hir>,
},
}
```
AST lowering is where `InlineAsmRegOrRegClass` is converted from `Symbol`s to an actual register or register class. If any modifiers are specified for a template string placeholder, these are validated against the set allowed for that operand type. Finally, explicit registers for inputs and outputs are checked for conflicts (same register used for different operands).
## Type checking
Each register class has a whitelist of types that it may be used with. After the types of all operands have been determined, the `intrinsicck` pass will check that these types are in the whitelist. It also checks that split `inout` operands have compatible types and that `const` operands are integers or floats. Suggestions are emitted where needed if a template modifier should be used for an operand based on the type that was passed into it.
## HAIR
`InlineAsm` is represented as an expression in the HAIR:
```rust
crate enum ExprKind<'tcx> {
// [..]
InlineAsm {
template: &'tcx [InlineAsmTemplatePiece],
operands: Vec<InlineAsmOperand<'tcx>>,
options: InlineAsmOptions,
},
}
crate enum InlineAsmOperand<'tcx> {
In {
reg: InlineAsmRegOrRegClass,
expr: ExprRef<'tcx>,
},
Out {
reg: InlineAsmRegOrRegClass,
late: bool,
expr: Option<ExprRef<'tcx>>,
},
InOut {
reg: InlineAsmRegOrRegClass,
late: bool,
expr: ExprRef<'tcx>,
},
SplitInOut {
reg: InlineAsmRegOrRegClass,
late: bool,
in_expr: ExprRef<'tcx>,
out_expr: Option<ExprRef<'tcx>>,
},
Const {
expr: ExprRef<'tcx>,
},
SymFn {
expr: ExprRef<'tcx>,
},
SymStatic {
expr: ExprRef<'tcx>,
},
}
```
The only significant change compared to HIR is that `Sym` has been lowered to either a `SymFn` whose `expr` is a `Literal` ZST of the `fn`, or a `SymStatic` whose `expr` is a `StaticRef`.
## MIR
`InlineAsm` is represented as a `Terminator` in the MIR:
```rust
pub enum TerminatorKind<'tcx> {
// [..]
/// Block ends with an inline assembly block. This is a terminator since
/// inline assembly is allowed to diverge.
InlineAsm {
/// The template for the inline assembly, with placeholders.
template: &'tcx [InlineAsmTemplatePiece],
/// The operands for the inline assembly, as `Operand`s or `Place`s.
operands: Vec<InlineAsmOperand<'tcx>>,
/// Miscellaneous options for the inline assembly.
options: InlineAsmOptions,
/// Destination block after the inline assembly returns, unless it is
/// diverging (InlineAsmOptions::NORETURN).
destination: Option<BasicBlock>,
},
}
pub enum InlineAsmOperand<'tcx> {
In {
reg: InlineAsmRegOrRegClass,
value: Operand<'tcx>,
},
Out {
reg: InlineAsmRegOrRegClass,
late: bool,
place: Option<Place<'tcx>>,
},
InOut {
reg: InlineAsmRegOrRegClass,
late: bool,
in_value: Operand<'tcx>,
out_place: Option<Place<'tcx>>,
},
Const {
value: Operand<'tcx>,
},
SymFn {
value: Box<Constant<'tcx>>,
},
SymStatic {
value: Box<Constant<'tcx>>,
},
}
```
As part of HAIR lowering, `InOut` and `SplitInOut` operands are lowered to a split form with a separate `in_value` and `out_place`.
Semantically, the `InlineAsm` terminator is similar to the `Call` terminator except that it has multiple output places where a `Call` only has a single return place output.
The constant promotion pass is used to ensure that `const` operands are actually constants (using the same logic as `#[rustc_args_required_const]`).
## Codegen
Operands are lowered one more time before being passed to LLVM codegen:
```rust
pub enum InlineAsmOperandRef<'tcx, B: BackendTypes + ?Sized> {
In {
reg: InlineAsmRegOrRegClass,
value: OperandRef<'tcx, B::Value>,
},
Out {
reg: InlineAsmRegOrRegClass,
late: bool,
place: Option<PlaceRef<'tcx, B::Value>>,
},
InOut {
reg: InlineAsmRegOrRegClass,
late: bool,
in_value: OperandRef<'tcx, B::Value>,
out_place: Option<PlaceRef<'tcx, B::Value>>,
},
Const {
string: String,
},
SymFn {
instance: Instance<'tcx>,
},
SymStatic {
def_id: DefId,
},
}
```
The operands are lowered to LLVM operands and constraint codes as follow:
- `out` and the output part of `inout` operands are added first, as required by LLVM. Late output operands have a `=` prefix added to their constraint code, non-late output operands have a `=&` prefix added to their constraint code.
- `in` operands are added normally.
- `inout` operands are tied to the matching output operand.
- `sym` operands are passed as function pointers or pointers, using the `"s"` constraint.
- `const` operands are formatted to a string and directly inserted in the template string.
The template string is converted to LLVM form:
- `$` characters are escaped as `$$`.
- `const` operands are converted to strings and inserted directly.
- Placeholders are formatted as `${X:M}` where `X` is the operand index and `M` is the modifier character. Modifiers are converted from the Rust form to the LLVM form.
The various options are converted to clobber constraints or LLVM attributes, refer to the [RFC](https://github.com/Amanieu/rfcs/blob/inline-asm/text/0000-inline-asm.md#mapping-to-llvm-ir) for more details.
Note that LLVM is sometimes rather picky about what types it accepts for certain constraint codes so we sometimes need to insert conversions to/from a supported type. See the target-specific ISelLowering.cpp files in LLVM for details.
# Adding support for new architectures
Adding inline assembly support to an architecture is mostly a matter of defining the registers and register classes for that architecture. All the definitions for register classes are located in `src/librustc_target/asm/`.
Additionally you will need to implement lowering of these register classes to LLVM constraint codes in `src/librustc_codegen_llvm/asm.rs`.
