Insert checks for enum discriminants when debug assertions are enabled
Similar to the existing null-pointer and alignment checks, this checks for valid enum discriminants on creation of enums through unsafe transmutes. Essentially this sanitizes patterns like the following:
```rust
let val: MyEnum = unsafe { std::mem::transmute<u32, MyEnum>(42) };
```
An extension of this check will be done in a follow-up that explicitly sanitizes for extern enum values that come into Rust from e.g. C/C++.
This check is similar to Miri's capabilities of checking for valid construction of enum values.
This PR is inspired by saethlin@'s PR
https://github.com/rust-lang/rust/pull/104862. Thank you so much for keeping this code up and the detailed comments!
I also pair-programmed large parts of this together with vabr-g@.
r? `@saethlin`
Stop collecting unmentioned constants
This avoids generating useless dead LLVM IR. This appears to have regressed and/or been introduced in rust-lang/rust#53821 (unfortunately a very large PR - I don't see any direct discussion there of this particular change), but as far as I can tell is at least no longer necessary -- or we lack test coverage -- because none of our UI tests indicate diagnostics regressions. The adjusted codegen-units test has comments explicitly noting that these items should *not* be collected ("These are not referenced, so they do not produce mono-items").
I noticed this while looking at libcore LLVM IR we generate, which contained dead code references to the NOOP Waker item, which is never used inside libcore. Producing LLVM IR for it during libcore's compilation, only for that IR to get deleted by LLVM as unused, isn't useful. Note that the IR is generally all marked internal, too.
Similar to the existing nullpointer and alignment checks, this checks
for valid enum discriminants on creation of enums through unsafe
transmutes. Essentially this sanitizes patterns like the following:
```rust
let val: MyEnum = unsafe { std::mem::transmute<u32, MyEnum>(42) };
```
An extension of this check will be done in a follow-up that explicitly
sanitizes for extern enum values that come into Rust from e.g. C/C++.
This check is similar to Miri's capabilities of checking for valid
construction of enum values.
This PR is inspired by saethlin@'s PR
https://github.com/rust-lang/rust/pull/104862. Thank you so much for
keeping this code up and the detailed comments!
I also pair-programmed large parts of this together with vabr-g@.
Since 122662 this no longer gets used in vtables, so we're safe to fully
drop generating these empty functions. Those are eventually cleaned up
by LLVM, but it's wasteful to produce them in the first place.
This also adds a missing test for fn-ptr casts, which do still need to
generate no-op drop glue. It's possible a future optimization could
point all of those at the same drop glue (e.g., for *mut ()) rather than
for each separate type, but that would require extra work for CFI and
isn't particularly easy to do anyway.
While profiling Zed's dev build I've noticed that while most of the time `upstream_monomorphizations` takes a lot of time in monomorpization_collector, in some cases (e.g. build of `editor` itself)
the rest of monomorphization_collector_graph_walk dominates it. Most of the time is spent in collect_items_rec.
This PR aims to reduce the number of locks taking place; instead of locking output MonoItems once per children of current node, we do so once per *parent*. We also get to reuse locks for mentioned and used items.
While this commit does not reduce Wall time of Zed's build, it does shave off `cargo build -j1` from 43s to 41.5s.
Collect items referenced from var_debug_info
The collection is limited to full debuginfo builds to match behavior of FunctionCx::compute_per_local_var_debug_info.
Fixes#138942.
ssa/mono: deduplicate `type_has_metadata`
The implementation of the `type_has_metadata` function is duplicated in `rustc_codegen_ssa` and `rustc_monomorphize`, so move this to `rustc_middle`.
Greatly simplify lifetime captures in edition 2024
Remove most of the `+ Captures` and `+ '_` from the compiler, since they are now unnecessary with the new edition 2021 lifetime capture rules. Use some `+ 'tcx` and `+ 'static` rather than being overly verbose with precise capturing syntax.
The end goal is to eliminate `Map` altogether.
I added a `hir_` prefix to all of them, that seemed simplest. The
exceptions are `module_items` which became `hir_module_free_items` because
there was already a `hir_module_items`, and `items` which became
`hir_free_items` for consistency with `hir_module_free_items`.
Remove hook calling via `TyCtxtAt`.
All hooks receive a `TyCtxtAt` argument.
Currently hooks can be called through `TyCtxtAt` or `TyCtxt`. In the latter case, a `TyCtxtAt` is constructed with a dummy span and passed to the hook.
However, in practice hooks are never called through `TyCtxtAt`, and always receive a dummy span. (I confirmed this via code inspection, and double-checked it by temporarily making the `TyCtxtAt` code path panic and running all the tests.)
This commit removes all the `TyCtxtAt` machinery for hooks. All hooks now receive `TyCtxt` instead of `TyCtxtAt`. There are two existing hooks that use `TyCtxtAt::span`: `const_caller_location_provider` and `try_destructure_mir_constant_for_user_output`. For both hooks the span is always a dummy span, probably unintentionally. This dummy span use is now explicit. If a non-dummy span is needed for these two hooks it would be easy to add it as an extra argument because hooks are less constrained than queries.
r? `@oli-obk`
All hooks receive a `TyCtxtAt` argument.
Currently hooks can be called through `TyCtxtAt` or `TyCtxt`. In the
latter case, a `TyCtxtAt` is constructed with a dummy span and passed to
the hook.
However, in practice hooks are never called through `TyCtxtAt`, and
always receive a dummy span. (I confirmed this via code inspection, and
double-checked it by temporarily making the `TyCtxtAt` code path panic
and running all the tests.)
This commit removes all the `TyCtxtAt` machinery for hooks. All hooks
now receive `TyCtxt` instead of `TyCtxtAt`. There are two existing hooks
that use `TyCtxtAt::span`: `const_caller_location_provider` and
`try_destructure_mir_constant_for_user_output`. For both hooks the span
is always a dummy span, probably unintentionally. This dummy span use is
now explicit. If a non-dummy span is needed for these two hooks it would
be easy to add it as an extra argument because hooks are less
constrained than queries.
Insert null checks for pointer dereferences when debug assertions are enabled
Similar to how the alignment is already checked, this adds a check
for null pointer dereferences in debug mode. It is implemented similarly
to the alignment check as a `MirPass`.
This inserts checks in the same places as the `CheckAlignment` pass and additionally
also inserts checks for `Borrows`, so code like
```rust
let ptr: *const u32 = std::ptr::null();
let val: &u32 = unsafe { &*ptr };
```
will have a check inserted on dereference. This is done because null references
are UB. The alignment check doesn't cover these places, because in `&(*ptr).field`,
the exact requirement is that the final reference must be aligned. This is something to
consider further enhancements of the alignment check.
For now this is implemented as a separate `MirPass`, to make it easy to disable
this check if necessary.
This is related to a 2025H1 project goal for better UB checks in debug
mode: https://github.com/rust-lang/rust-project-goals/pull/177.
r? `@saethlin`
Similar to how the alignment is already checked, this adds a check
for null pointer dereferences in debug mode. It is implemented similarly
to the alignment check as a MirPass.
This is related to a 2025H1 project goal for better UB checks in debug
mode: https://github.com/rust-lang/rust-project-goals/pull/177.
Autodiff Upstreaming - rustc_codegen_ssa, rustc_middle
This PR should not be merged until the rustc_codegen_llvm part is merged.
I will also alter it a little based on what get's shaved off from the cg_llvm PR,
and address some of the feedback I received in the other PR (including cleanups).
I am putting it already up to
1) Discuss with `@jieyouxu` if there is more work needed to add tests to this and
2) Pray that there is someone reviewing who can tell me why some of my autodiff invocations get lost.
Re 1: My test require fat-lto. I also modify the compilation pipeline. So if there are any other llvm-ir tests in the same compilation unit then I will likely break them. Luckily there are two groups who currently have the same fat-lto requirement for their GPU code which I have for my autodiff code and both groups have some plans to enable support for thin-lto. Once either that work pans out, I'll copy it over for this feature. I will also work on not changing the optimization pipeline for functions not differentiated, but that will require some thoughts and engineering, so I think it would be good to be able to run the autodiff tests isolated from the rest for now. Can you guide me here please?
For context, here are some of my tests in the samples folder: https://github.com/EnzymeAD/rustbook
Re 2: This is a pretty serious issue, since it effectively prevents publishing libraries making use of autodiff: https://github.com/EnzymeAD/rust/issues/173. For some reason my dummy code persists till the end, so the code which calls autodiff, deletes the dummy, and inserts the code to compute the derivative never gets executed. To me it looks like the rustc_autodiff attribute just get's dropped, but I don't know WHY? Any help would be super appreciated, as rustc queries look a bit voodoo to me.
Tracking:
- https://github.com/rust-lang/rust/issues/124509
r? `@jieyouxu`
Eagerly mono drop for structs with lifetimes
That is, use `!generics.requires_monomorphization()` rather than `generics.is_empty()` like the rest of the mono collector code.
Eagerly collect mono items for non-generic closures
This allows users to use `-Zprint-mono-items=eager` to eagerly monomorphize closures and coroutine bodies, in case they want to inspect the LLVM or ASM for those items.
`-Zprint-mono-items`, which used to be called `-Zprint-trans-items`, was originally added in https://github.com/rust-lang/rust/pull/30900:
> Eager mode is meant to be used in conjunction with incremental compilation
> where a stable set of translation items is more important than a minimal
> one. Thus, eager mode will instantiate drop-glue for every drop-able type
> in the crate, even of no drop call for that type exists (yet). It will
> also instantiate default implementations of trait methods, something that
> otherwise is only done on demand.
Although it remains an unstable option, its purpose has somewhat expanded since then, and as far as I can tell it's generally useful for cases when you want to monomorphize as many items as possible, even if they're unreachable. Specifically, it's useful for debugging since you can look at the codegen'd body of a function, since we don't emit items that are not reachable in monomorphization.
And even more specifically, it would be very to monomorphize the coroutine body of an async fn, since those you can't easily call those without a runtime. This PR enables this usecase since we now monomorphize `DefKind::Closure`.
Adds `#[rustc_force_inline]` which is similar to always inlining but
reports an error if the inlining was not possible, and which always
attempts to inline annotated items, regardless of optimisation levels.
It can only be applied to free functions to guarantee that the MIR
inliner will be able to resolve calls.
`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.
