`rustc_span::symbol` defines some things that are re-exported from
`rustc_span`, such as `Symbol` and `sym`. But it doesn't re-export some
closely related things such as `Ident` and `kw`. So you can do `use
rustc_span::{Symbol, sym}` but you have to do `use
rustc_span::symbol::{Ident, kw}`, which is inconsistent for no good
reason.
This commit re-exports `Ident`, `kw`, and `MacroRulesNormalizedIdent`,
and changes many `rustc_span::symbol::` qualifiers in `compiler/` to
`rustc_span::`. This is a 200+ net line of code reduction, mostly
because many files with two `use rustc_span` items can be reduced to
one.
This reduces code sizes and better respects programmer intent when
marking inline(never). Previously such a marking was essentially ignored
for generic functions, as we'd still inline them in remote crates.
the behavior of the type system not only depends on the current
assumptions, but also the currentnphase of the compiler. This is
mostly necessary as we need to decide whether and how to reveal
opaque types. We track this via the `TypingMode`.
Querify MonoItem collection
Factored out of https://github.com/rust-lang/rust/pull/131650. These changes are required for post-mono MIR opts, because the previous implementation would load the MIR for every Instance that we traverse (as well as invoke queries on it). The cost of that would grow massively with post-mono MIR opts because we'll need to load new MIR for every Instance, instead of re-using the `optimized_mir` for every Instance with the same DefId.
So the approach here is to add two new queries, `items_of_instance` and `size_estimate`, which contain the specific information about an Instance's MIR that MirUsedCollector and CGU partitioning need, respectively. Caching these significantly increases the size of the query cache, but that's justified by our improved incrementality (I'm sure walking all the MIR for a huge crate scales quite poorly).
This also changes `MonoItems` into a type that will retain the traversal order (otherwise we perturb a bunch of diagnostics), and will also eliminate duplicate findings. Eliminating duplicates removes about a quarter of the query cache size growth.
The perf improvements in this PR are inflated because rustc-perf uses `-Zincremental-verify-ich`, which makes loading MIR a lot slower because MIR contains a lot of Spans and computing the stable hash of a Span is slow. And the primary goal of this PR is to load less MIR. Some squinting at `collector profile_local perf-record +stage1` runs suggests the magnitude of the improvements in this PR would be decreased by between a third and a half if that flag weren't being used. Though this effect may apply to the regressions too since most are incr-full and this change also causes such builds to encode more Spans.
Emit warning when calling/declaring functions with unavailable vectors.
On some architectures, vector types may have a different ABI depending on whether the relevant target features are enabled. (The ABI when the feature is disabled is often not specified, but LLVM implements some de-facto ABI.)
As discussed in rust-lang/lang-team#235, this turns out to very easily lead to unsound code.
This commit makes it a post-monomorphization future-incompat warning to declare or call functions using those vector types in a context in which the corresponding target features are disabled, if using an ABI for which the difference is relevant. This ensures that these functions are always called with a consistent ABI.
See the [nomination comment](https://github.com/rust-lang/rust/pull/127731#issuecomment-2288558187) for more discussion.
Part of #116558
r? RalfJung
On some architectures, vector types may have a different ABI depending
on whether the relevant target features are enabled. (The ABI when the
feature is disabled is often not specified, but LLVM implements some
de-facto ABI.)
As discussed in rust-lang/lang-team#235, this turns out to very easily
lead to unsound code.
This commit makes it a post-monomorphization future-incompat warning to
declare or call functions using those vector types in a context in which
the corresponding target features are disabled, if using an ABI for
which the difference is relevant. This ensures that these functions are
always called with a consistent ABI.
See the [nomination comment](https://github.com/rust-lang/rust/pull/127731#issuecomment-2288558187)
for more discussion.
Part of #116558
- removed extra bits from predicates queries that are no longer needed in the new system
- removed the need for `non_erasable_generics` to take in tcx and DefId, removed unused arguments in callers
Emit future-incompatibility lint when calling/declaring functions with vectors that require missing target feature
On some architectures, vector types may have a different ABI depending on whether the relevant target features are enabled. (The ABI when the feature is disabled is often not specified, but LLVM implements some de-facto ABI.)
As discussed in https://github.com/rust-lang/lang-team/issues/235, this turns out to very easily lead to unsound code.
This commit makes it a post-monomorphization error to declare or call functions using those vector types in a context in which the corresponding target features are disabled, if using an ABI for which the difference is relevant. This ensures that these functions are always called with a consistent ABI.
See the [nomination comment](https://github.com/rust-lang/rust/pull/127731#issuecomment-2288558187) for more discussion.
r? RalfJung
Part of https://github.com/rust-lang/rust/issues/116558
On some architectures, vector types may have a different ABI when
relevant target features are enabled.
As discussed in https://github.com/rust-lang/lang-team/issues/235, this
turns out to very easily lead to unsound code.
This commit makes it an error to declare or call functions using those
vector types in a context in which the corresponding target features are
disabled, if using an ABI for which the difference is relevant.
Add `File` constructors that return files wrapped with a buffer
In addition to the light convenience, these are intended to raise visibility that buffering is something you should consider when opening a file, since unbuffered I/O is a common performance footgun to Rust newcomers.
ACP: https://github.com/rust-lang/libs-team/issues/446
Tracking Issue: #130804
Separate collection of crate-local inherent impls from error tracking
#119895 changed the return type of the `crate_inherent_impls` query from `CrateInherentImpls` to `Result<CrateInherentImpls, ErrorGuaranteed>` to avoid needing to use the non-parallel-friendly `track_errors()` to track if an error was reporting from within the query... This was mostly fine until #121113, which stopped halting compilation when we hit an `Err(ErrorGuaranteed)` in the `crate_inherent_impls` query.
Thus we proceed onwards to typeck, and since a return type of `Result<CrateInherentImpls, ErrorGuaranteed>` means that the query can *either* return one of "the list inherent impls" or "error has been reported", later on when we want to assemble method or associated item candidates for inherent impls, we were just treating any `Err(ErrorGuaranteed)` return value as if Rust had no inherent impls defined anywhere at all! This leads to basically every inherent method call failing with an error, lol, which was reported in #127798.
This PR changes the `crate_inherent_impls` query to return `(CrateInherentImpls, Result<(), ErrorGuaranteed>)`, i.e. returning the inherent impls collected *and* whether an error was reported in the query itself. It firewalls the latter part of that query into a new `crate_inherent_impls_validity_check` just for the `ensure()` call.
This fixes#127798.
Simplify some nested `if` statements
Applies some but not all instances of `clippy::collapsible_if`. Some ended up looking worse afterwards, though, so I left those out. Also applies instances of `clippy::collapsible_else_if`
Review with whitespace disabled please.
Use `append` instead of `extend(drain(..))`
The first commit adds `IndexVec::append` that forwards to `Vec::append`, and uses it in a couple places.
The second commit updates `indexmap` for its new `IndexMap::append`, and also uses that in a couple places.
These changes are similar to what [`clippy::extend_with_drain`](https://rust-lang.github.io/rust-clippy/master/index.html#/extend_with_drain) would suggest, just for other collection types.
Support tail calls in mir via `TerminatorKind::TailCall`
This is one of the interesting bits in tail call implementation — MIR support.
This adds a new `TerminatorKind` which represents a tail call:
```rust
TailCall {
func: Operand<'tcx>,
args: Vec<Operand<'tcx>>,
fn_span: Span,
},
```
*Structurally* this is very similar to a normal `Call` but is missing a few fields:
- `destination` — tail calls don't write to destination, instead they pass caller's destination to the callee (such that eventual `return` will write to the caller of the function that used tail call)
- `target` — similarly to `destination` tail calls pass the caller's return address to the callee, so there is nothing to do
- `unwind` — I _think_ this is applicable too, although it's a bit confusing
- `call_source` — `become` forbids operators and is not created as a lowering of something else; tail calls always come from HIR (at least for now)
It might be helpful to read the interpreter implementation to understand what `TailCall` means exactly, although I've tried documenting it too.
-----
There are a few `FIXME`-questions still left, ideally we'd be able to answer them during review ':)
-----
r? `@oli-obk`
cc `@scottmcm` `@DrMeepster` `@JakobDegen`
Miri function identity hack: account for possible inlining
Having a non-lifetime generic is not the only reason a function can be duplicated. Another possibility is that the function may be eligible for cross-crate inlining. So also take into account the inlining attribute in this Miri hack for function pointer identity.
That said, `cross_crate_inlinable` will still sometimes return true even for `inline(never)` functions:
- when they are `DefKind::Ctor(..) | DefKind::Closure` -- I assume those cannot be `InlineAttr::Never` anyway?
- when `cross_crate_inline_threshold == InliningThreshold::Always`
so maybe this is still not quite the right criterion to use for function pointer identity.
smir: merge identical Constant and ConstOperand types
The first commit renames the const operand visitor functions on regular MIR to match the type name, that was forgotten in the original rename.
The second commit changes stable MIR, fixing https://github.com/rust-lang/project-stable-mir/issues/71. Previously there were two different smir types for the MIR type `ConstOperand`, one used in `Operand` and one in `VarDebugInfoContents`.
Maybe we should have done this with https://github.com/rust-lang/rust/pull/125967, so there's only a single breaking change... but I saw that PR too late.
Fixes https://github.com/rust-lang/project-stable-mir/issues/71
We already do this for a number of crates, e.g. `rustc_middle`,
`rustc_span`, `rustc_metadata`, `rustc_span`, `rustc_errors`.
For the ones we don't, in many cases the attributes are a mess.
- There is no consistency about order of attribute kinds (e.g.
`allow`/`deny`/`feature`).
- Within attribute kind groups (e.g. the `feature` attributes),
sometimes the order is alphabetical, and sometimes there is no
particular order.
- Sometimes the attributes of a particular kind aren't even grouped
all together, e.g. there might be a `feature`, then an `allow`, then
another `feature`.
This commit extends the existing sorting to all compiler crates,
increasing consistency. If any new attribute line is added there is now
only one place it can go -- no need for arbitrary decisions.
Exceptions:
- `rustc_log`, `rustc_next_trait_solver` and `rustc_type_ir_macros`,
because they have no crate attributes.
- `rustc_codegen_gcc`, because it's quasi-external to rustc (e.g. it's
ignored in `rustfmt.toml`).
Codegen const panic messages as function calls
This skips emitting extra arguments at every callsite (of which there
can be many). For a librustc_driver build with overflow checks enabled,
this cuts 0.7MB from the resulting shared library (see [perf]).
A sample improvement from nightly:
```
leaq str.0(%rip), %rdi
leaq .Lalloc_d6aeb8e2aa19de39a7f0e861c998af13(%rip), %rdx
movl $25, %esi
callq *_ZN4core9panicking5panic17h17cabb89c5bcc999E@GOTPCREL(%rip)
```
to this PR:
```
leaq .Lalloc_d6aeb8e2aa19de39a7f0e861c998af13(%rip), %rdi
callq *_RNvNtNtCsduqIKoij8JB_4core9panicking11panic_const23panic_const_div_by_zero@GOTPCREL(%rip)
```
[perf]: https://perf.rust-lang.org/compare.html?start=a7e4de13c1785819f4d61da41f6704ed69d5f203&end=64fbb4f0b2d621ff46d559d1e9f5ad89a8d7789b&stat=instructions:u
Remove `TypeAndMut` from `ty::RawPtr` variant, make it take `Ty` and `Mutability`
Pretty much mechanically converting `ty::RawPtr(ty::TypeAndMut { ty, mutbl })` to `ty::RawPtr(ty, mutbl)` and its fallout.
r? lcnr
cc rust-lang/types-team#124
"Handle" calls to upstream monomorphizations in compiler_builtins
This is pretty cooked, but I think it works.
compiler-builtins has a long-standing problem that at link time, its rlib cannot contain any calls to `core`. And yet, in codegen we _love_ inserting calls to symbols in `core`, generally from various panic entrypoints.
I intend this PR to attack that problem as completely as possible. When we generate a function call, we now check if we are generating a function call from `compiler_builtins` and whether the callee is a function which was not lowered in the current crate, meaning we will have to link to it.
If those conditions are met, actually generating the call is asking for a linker error. So we don't. If the callee diverges, we lower to an abort with the same behavior as `core::intrinsics::abort`. If the callee does not diverge, we produce an error. This means that compiler-builtins can contain panics, but they'll SIGILL instead of panicking. I made non-diverging calls a compile error because I'm guessing that they'd mostly get into compiler-builtins by someone making a mistake while working on the crate, and compile errors are better than linker errors. We could turn such calls into aborts as well if that's preferred.
This skips emitting extra arguments at every callsite (of which there
can be many). For a librustc_driver build with overflow checks enabled,
this cuts 0.7MB from the resulting binary.
recursively evaluate the constants in everything that is 'mentioned'
This is another attempt at fixing https://github.com/rust-lang/rust/issues/107503. The previous attempt at https://github.com/rust-lang/rust/pull/112879 seems stuck in figuring out where the [perf regression](https://perf.rust-lang.org/compare.html?start=c55d1ee8d4e3162187214692229a63c2cc5e0f31&end=ec8de1ebe0d698b109beeaaac83e60f4ef8bb7d1&stat=instructions:u) comes from. In https://github.com/rust-lang/rust/pull/122258 I learned some things, which informed the approach this PR is taking.
Quoting from the new collector docs, which explain the high-level idea:
```rust
//! One important role of collection is to evaluate all constants that are used by all the items
//! which are being collected. Codegen can then rely on only encountering constants that evaluate
//! successfully, and if a constant fails to evaluate, the collector has much better context to be
//! able to show where this constant comes up.
//!
//! However, the exact set of "used" items (collected as described above), and therefore the exact
//! set of used constants, can depend on optimizations. Optimizing away dead code may optimize away
//! a function call that uses a failing constant, so an unoptimized build may fail where an
//! optimized build succeeds. This is undesirable.
//!
//! To fix this, the collector has the concept of "mentioned" items. Some time during the MIR
//! pipeline, before any optimization-level-dependent optimizations, we compute a list of all items
//! that syntactically appear in the code. These are considered "mentioned", and even if they are in
//! dead code and get optimized away (which makes them no longer "used"), they are still
//! "mentioned". For every used item, the collector ensures that all mentioned items, recursively,
//! do not use a failing constant. This is reflected via the [`CollectionMode`], which determines
//! whether we are visiting a used item or merely a mentioned item.
//!
//! The collector and "mentioned items" gathering (which lives in `rustc_mir_transform::mentioned_items`)
//! need to stay in sync in the following sense:
//!
//! - For every item that the collector gather that could eventually lead to build failure (most
//! likely due to containing a constant that fails to evaluate), a corresponding mentioned item
//! must be added. This should use the exact same strategy as the ecollector to make sure they are
//! in sync. However, while the collector works on monomorphized types, mentioned items are
//! collected on generic MIR -- so any time the collector checks for a particular type (such as
//! `ty::FnDef`), we have to just onconditionally add this as a mentioned item.
//! - In `visit_mentioned_item`, we then do with that mentioned item exactly what the collector
//! would have done during regular MIR visiting. Basically you can think of the collector having
//! two stages, a pre-monomorphization stage and a post-monomorphization stage (usually quite
//! literally separated by a call to `self.monomorphize`); the pre-monomorphizationn stage is
//! duplicated in mentioned items gathering and the post-monomorphization stage is duplicated in
//! `visit_mentioned_item`.
//! - Finally, as a performance optimization, the collector should fill `used_mentioned_item` during
//! its MIR traversal with exactly what mentioned item gathering would have added in the same
//! situation. This detects mentioned items that have *not* been optimized away and hence don't
//! need a dedicated traversal.
enum CollectionMode {
/// Collect items that are used, i.e., actually needed for codegen.
///
/// Which items are used can depend on optimization levels, as MIR optimizations can remove
/// uses.
UsedItems,
/// Collect items that are mentioned. The goal of this mode is that it is independent of
/// optimizations: the set of "mentioned" items is computed before optimizations are run.
///
/// The exact contents of this set are *not* a stable guarantee. (For instance, it is currently
/// computed after drop-elaboration. If we ever do some optimizations even in debug builds, we
/// might decide to run them before computing mentioned items.) The key property of this set is
/// that it is optimization-independent.
MentionedItems,
}
```
And the `mentioned_items` MIR body field docs:
```rust
/// Further items that were mentioned in this function and hence *may* become monomorphized,
/// depending on optimizations. We use this to avoid optimization-dependent compile errors: the
/// collector recursively traverses all "mentioned" items and evaluates all their
/// `required_consts`.
///
/// This is *not* soundness-critical and the contents of this list are *not* a stable guarantee.
/// All that's relevant is that this set is optimization-level-independent, and that it includes
/// everything that the collector would consider "used". (For example, we currently compute this
/// set after drop elaboration, so some drop calls that can never be reached are not considered
/// "mentioned".) See the documentation of `CollectionMode` in
/// `compiler/rustc_monomorphize/src/collector.rs` for more context.
pub mentioned_items: Vec<Spanned<MentionedItem<'tcx>>>,
```
Fixes#107503
