avoid promoting division, modulo and indexing operations that could fail
For division, `x / y` will still be promoted if `y` is a non-zero integer literal; however, `1/(1+1)` will not be promoted any more.
While at it, also see if we can reject promoting floating-point arithmetic (which are [complicated](https://github.com/rust-lang/unsafe-code-guidelines/issues/237) so maybe we should not promote them).
This will need a crater run to see if there's code out there that relies on these things being promoted.
If we can land this, promoteds in `fn`/`const fn` cannot fail to evaluate any more, which should let us do some simplifications in codegen/Miri!
Cc https://github.com/rust-lang/rfcs/pull/3027
Fixes https://github.com/rust-lang/rust/issues/61821
r? `@oli-obk`
Fix `unused_unsafe` label with `unsafe_block_in_unsafe_fn
Previously, the following code:
```rust
#![feature(unsafe_block_in_unsafe_fn)]
unsafe fn foo() {
unsafe { unsf() }
}
unsafe fn unsf() {}
```
Would give the following warning:
```
warning: unnecessary `unsafe` block
--> src/lib.rs:4:5
|
4 | unsafe { unsf() }
| ^^^^^^ unnecessary `unsafe` block
|
= note: `#[warn(unused_unsafe)]` on by default
```
which doesn't point out that the block is in an `unsafe fn`.
Tracking issue: #71668
cc #79208
Stability oddity with const intrinsics
cc `@RalfJung`
In https://github.com/rust-lang/rust/pull/80699#discussion_r551495670 `@usbalbin` realized we accepted some intrinsics as `const` without a `#[rustc_const_(un)stable]` attribute. I did some digging, and that example works because intrinsics inherit their stability from their parents... including `#[rustc_const_(un)stable]` attributes. While we may want to fix that (not sure, wasn't there just a MCPed PR that caused this on purpose?), we definitely want tests for it, thus this PR adding tests and some fun tracing statements.
Use PlaceRef projection abstractions more consistently in rustc_mir
PlaceRef contains abstractions for dealing with the `projections` array. This PR uses these abstractions more consistently within the `rustc_mir` crate.
See associated issue: rust-lang/rust#80647.
r? `@RalfJung`
implement ptr::write without dedicated intrinsic
This makes `ptr::write` more consistent with `ptr::write_unaligned`, `ptr::read`, `ptr::read_unaligned`, all of which are implemented in terms of `copy_nonoverlapping`.
This means we can also remove `move_val_init` implementations in codegen and Miri, and its special handling in the borrow checker.
Also see [this Zulip discussion](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/ptr.3A.3Aread.20vs.20ptr.3A.3Awrite).
Make CTFE able to check for UB...
... by not doing any optimizations on the `const fn` MIR used in CTFE. This means we duplicate all `const fn`'s MIR now, once for CTFE, once for runtime. This PR is for checking the perf effect, so we have some data when talking about https://github.com/rust-lang/const-eval/blob/master/rfcs/0000-const-ub.md
To do this, we now have two queries for obtaining mir: `optimized_mir` and `mir_for_ctfe`. It is now illegal to invoke `optimized_mir` to obtain the MIR of a const/static item's initializer, an array length, an inline const expression or an enum discriminant initializer. For `const fn`, both `optimized_mir` and `mir_for_ctfe` work, the former returning the MIR that LLVM should use if the function is called at runtime. Similarly it is illegal to invoke `mir_for_ctfe` on regular functions.
This is all checked via appropriate assertions and I don't think it is easy to get wrong, as there should be no `mir_for_ctfe` calls outside the const evaluator or metadata encoding. Almost all rustc devs should keep using `optimized_mir` (or `instance_mir` for that matter).
Add ABI argument for called function in `find_mir_or_eval_fn` and
`call_extra_fn`. Useful for comparing with expected ABI in interpreters.
Related to [miri/1631](https://github.com/rust-lang/miri/issues/1631)
MIR Inline is incompatible with coverage
Fixes: #80060
Fixed by disabling inlining if `-Zinstrument-coverage` is set.
The PR also adds additional use cases to the coverage test for doctests.
r? `@wesleywiser`
cc: `@tmandry`
Make `ExpnData` fields `krate` and `orig_id` private
These fields are only used by hygiene serialized, and should not be
accessed by anything outside of `rustc_span`.
