In PR 90877 T-lang decided not to remove `intrinsics::pref_align_of`.
However, the intrinsic and its supporting code
1. is a nightly feature, so can be removed at compiler/libs discretion
2. requires considerable effort in the compiler to support, as it
necessarily complicates every single site reasoning about alignment
3. has been justified based on relevance to codegen, but it is only a
requirement for C++ (not C, not Rust) stack frame layout for AIX,
in ways Rust would not consider even with increased C++ interop
4. is only used by rustc to overalign some globals, not correctness
5. can be adequately replaced by other rules for globals, as it mostly
affects alignments for a few types under 16 bytes of alignment
6. has only one clear benefactor: automating C -> Rust translation
for GNU extensions like `__alignof`
7. such code was likely intended to be `alignof` or `_Alignof`,
because the GNU extension is a "false friend" of the C keyword,
which makes the choice to support such a mapping very questionable
8. makes it easy to do incorrect codegen in the compiler by its mere
presence as usual Rust rules of alignment (e.g. `size == align * N`)
do not hold with preferred alignment
The implementation is clearly damaging the code quality of the compiler.
Thus it is within the compiler team's purview to simply rip it out.
If T-lang wishes to have this intrinsic restored for c2rust's benefit,
it would have to use a radically different implementation that somehow
does not cause internal incorrectness.
Until then, remove the intrinsic and its supporting code, as one tool
and an ill-considered GCC extension cannot justify risking correctness.
Because we touch a fair amount of the compiler to change this at all,
and unfortunately the duplication of AbiAndPrefAlign is deep-rooted,
we keep an "AbiAlign" type which we can wean code off later.
Add const support for the float rounding methods floor, ceil, trunc,
fract, round and round_ties_even.
This works by moving the calculation logic from
src/tools/miri/src/intrinsics/mod.rs
into
compiler/rustc_const_eval/src/interpret/intrinsics.rs.
All relevant method definitions were adjusted to include the `const`
keyword for all supported float types: f16, f32, f64 and f128.
The constness is hidden behind the feature gate
feature(const_float_round_methods)
which is tracked in
https://github.com/rust-lang/rust/issues/141555
This commit is a squash of the following commits:
- test: add tests that we expect to pass when float rounding becomes const
- feat: make float rounding methods `const`
- fix: replace `rustc_allow_const_fn_unstable(core_intrinsics)` attribute with `#[rustc_const_unstable(feature = "f128", issue = "116909")]` in `library/core/src/num/f128.rs`
- revert: undo update to `library/stdarch`
- refactor: replace multiple `float_<mode>_intrinsic` rounding methods with a single, parametrized one
- fix: add `#[cfg(not(bootstrap))]` to new const method tests
- test: add extra sign tests to check `+0.0` and `-0.0`
- revert: undo accidental changes to `round` docs
- fix: gate `const` float round method behind `const_float_round_methods`
- fix: remove unnecessary `#![feature(const_float_methods)]`
- fix: remove unnecessary `#![feature(const_float_methods)]` [2]
- revert: undo changes to `tests/ui/consts/const-eval/float_methods.rs`
- fix: adjust after rebase
- test: fix float tests
- test: add tests for `fract`
- chore: add commented-out `const_float_round_methods` feature gates to `f16` and `f128`
- fix: adjust NaN when rounding floats
- chore: add FIXME comment for de-duplicating float tests
- test: remove unnecessary test file `tests/ui/consts/const-eval/float_methods.rs`
- test: fix tests after upstream simplification of how float tests are run
interpret: add allocation parameters to `AllocBytes`
Necessary for a better implementation of [rust-lang/miri#4343](https://github.com/rust-lang/miri/pull/4343). Also included here is the code from that PR, adapted to this new interface for the sake of example and so that CI can run on them; the Miri changes can be reverted and merged separately, though.
r? `@RalfJung`
Add TRACING_ENABLED to Machine and add enter_trace_span!()
This PR adds the necessary infrastructure to make it possible to do tracing calls from within `rustc_const_eval` when running Miri, while making sure they don't impact the performance of normal compiler execution. This is done by adding a `const` boolean to `Machine`, false by default, but that will be set to true in Miri only. The tracing macro `enter_trace_span!()` checks if it is true before doing anything, and since the value of a `const` is known at compile time, if it it false it the whole tracing call should be optimized out.
I will soon open further PRs to add tracing macro calls similar to this one, so that afterwards it will be possible to learn more about Miri's time spent in the various interpretation steps:
```rs
let _guard = enter_trace_span!(M, "eval_statement", "{:?}", stmt);
```
r? `@RalfJung`
Remove global `next_disambiguator` state and handle it with a `DisambiguatorState` type
This removes `Definitions.next_disambiguator` as it doesn't guarantee deterministic def paths when `create_def` is called in parallel. Instead a new `DisambiguatorState` type is passed as a mutable reference to `create_def` to help create unique def paths. `create_def` calls with distinct `DisambiguatorState` instances must ensure that that the def paths are unique without its help.
Anon associated types did rely on this global state for uniqueness and are changed to use (method they're defined in + their position in the method return type) as the `DefPathData` to ensure uniqueness. This also means that the method they're defined in appears in error messages, which is nicer.
`DefPathData::NestedStatic` is added to use for nested data inside statics instead of reusing `DefPathData::AnonConst` to avoid conflicts with those.
cc `@oli-obk`
Change `InterpCx::instantiate*` function visibility to pub
For some ongoing work in Miri we need to be able to access `instantiate_from_current_frame_and_normalize_erasing_regions` and `instantiate_from_frame_and_normalize_erasing_regions` on `InterpCx`.
r? `@RalfJung`
miri native-call support: all previously exposed provenance is accessible to the callee
When Miri invokes a native C function, the memory C can access needs to be "prepared": to avoid false positives, we need to consider all that memory initialized, and we need to consider it to have arbitrary provenance. So far we did this for all pointers passed to C, but not for pointers that were exposed already before the native call. This PR adjusts the logic so that we now "prepare" all memory that has ever been exposed.
This fixes cases such as:
- cast a pointer to integer, send that integer to C, and access the memory there (`test_pass_ptr_as_int`)
- send a pointer to some memory to C, which stores it somewhere; then in Rust store another pointer in that memory, and access that via C (`test_pass_ptr_via_previously_shared_mem`)
r? `````@oli-obk`````
rename BackendRepr::Vector → SimdVector
For many Rustaceans, "vector" does not imply "SIMD", so let's be more clear in this type that is used pervasively in the compiler.
r? `@workingjubilee`
Previously, we included a redundant prefix on the panic message and a postfix of the location of the panic. The prefix didn't carry any additional information beyond "something failed", and the location of the panic is redundant with the diagnostic's span, which gets printed out even if its code is not shown.
```
error[E0080]: evaluation of constant value failed
--> $DIR/assert-type-intrinsics.rs:11:9
|
LL | MaybeUninit::<!>::uninit().assume_init();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ evaluation panicked: aborted execution: attempted to instantiate uninhabited type `!`
```
```
error[E0080]: evaluation of `Fail::<i32>::C` failed
--> $DIR/collect-in-dead-closure.rs:9:19
|
LL | const C: () = panic!();
| ^^^^^^^^ evaluation panicked: explicit panic
|
= note: this error originates in the macro
`$crate::panic::panic_2015` which comes from the expansion of the macro
`panic` (in Nightly builds, run with -Z macro-backtrace for more info)
```
```
error[E0080]: evaluation of constant value failed
--> $DIR/uninhabited.rs:41:9
|
LL | assert!(false);
| ^^^^^^^^^^^^^^ evaluation panicked: assertion failed: false
|
= note: this error originates in the macro `assert` (in Nightly builds, run with -Z macro-backtrace for more info)
```
---
When the primary span for a const error is the same as the first frame in the const error report, skip it.
```
error[E0080]: evaluation of constant value failed
--> $DIR/issue-88434-removal-index-should-be-less.rs:3:24
|
LL | const _CONST: &[u8] = &f(&[], |_| {});
| ^^^^^^^^^^^^^^ evaluation panicked: explicit panic
|
note: inside `f::<{closure@$DIR/issue-88434-removal-index-should-be-less.rs:3:31: 3:34}>`
--> $DIR/issue-88434-removal-index-should-be-less.rs:10:5
|
LL | panic!()
| ^^^^^^^^ the failure occurred here
= note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
```
instead of
```
error[E0080]: evaluation of constant value failed
--> $DIR/issue-88434-removal-index-should-be-less.rs:10:5
|
LL | panic!()
| ^^^^^^^^ explicit panic
|
note: inside `f::<{closure@$DIR/issue-88434-removal-index-should-be-less.rs:3:31: 3:34}>`
--> $DIR/issue-88434-removal-index-should-be-less.rs:10:5
|
LL | panic!()
| ^^^^^^^^
note: inside `_CONST`
--> $DIR/issue-88434-removal-index-should-be-less.rs:3:24
|
LL | const _CONST: &[u8] = &f(&[], |_| {});
| ^^^^^^^^^^^^^^
= note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
```
---
Revert order of constant evaluation errors
Point at the code the user wrote first and std functions last.
```
error[E0080]: evaluation of constant value failed
--> $DIR/const-errs-dont-conflict-103369.rs:5:25
|
LL | impl ConstGenericTrait<{my_fn(1)}> for () {}
| ^^^^^^^^ evaluation panicked: Some error occurred
|
note: called from `my_fn`
--> $DIR/const-errs-dont-conflict-103369.rs:10:5
|
LL | panic!("Some error occurred");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
= note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
```
instead of
```
error[E0080]: evaluation of constant value failed
--> $DIR/const-errs-dont-conflict-103369.rs:10:5
|
LL | panic!("Some error occurred");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Some error occurred
|
note: called from `<() as ConstGenericTrait<{my_fn(1)}>>::{constant#0}`
--> $DIR/const-errs-dont-conflict-103369.rs:5:25
|
LL | impl ConstGenericTrait<{my_fn(1)}> for () {}
| ^^^^^^^^
= note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
```
