This will allow MIR building to check whether a function is eligible for
coverage instrumentation, and avoid collecting branch coverage info if it is
not.
Distinguish between library and lang UB in assert_unsafe_precondition
As described in https://github.com/rust-lang/rust/pull/121583#issuecomment-1963168186, `assert_unsafe_precondition` now explicitly distinguishes between language UB (conditions we explicitly optimize on) and library UB (things we document you shouldn't do, and maybe some library internals assume you don't do).
`debug_assert_nounwind` was originally added to avoid the "only at runtime" aspect of `assert_unsafe_precondition`. Since then the difference between the macros has gotten muddied. This totally revamps the situation.
Now _all_ preconditions shall be checked with `assert_unsafe_precondition`. If you have a precondition that's only checkable at runtime, do a `const_eval_select` hack, as done in this PR.
r? RalfJung
Add asm goto support to `asm!`
Tracking issue: #119364
This PR implements asm-goto support, using the syntax described in "future possibilities" section of [RFC2873](https://rust-lang.github.io/rfcs/2873-inline-asm.html#asm-goto).
Currently I have only implemented the `label` part, not the `fallthrough` part (i.e. fallthrough is implicit). This doesn't reduce the expressive though, since you can use label-break to get arbitrary control flow or simply set a value and rely on jump threading optimisation to get the desired control flow. I can add that later if deemed necessary.
r? ``@Amanieu``
cc ``@ojeda``
interpret: avoid a long-lived PlaceTy in stack frames
`PlaceTy` uses a representation that's not very stable under changes to the stack. I'd feel better if we didn't have one in the long-term machine state.
r? `@oli-obk`
Fix `async Fn` confirmation for `FnDef`/`FnPtr`/`Closure` types
Fixes three issues:
1. The code in `extract_tupled_inputs_and_output_from_async_callable` was accidentally getting the *future* type and the *output* type (returned by the future) messed up for fnptr/fndef/closure types. :/
2. We have a (class of) bug(s) in the old solver where we don't really support higher ranked built-in `Future` goals for generators. This is not possible to hit on stable code, but [can be hit with `unboxed_closures`](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=e935de7181e37e13515ad01720bcb899) (#121653).
* I'm opting not to fix that in this PR. Instead, I just instantiate placeholders when confirming `async Fn` goals.
4. Fixed a bug when generating `FnPtr` shims for `async Fn` trait goals.
r? oli-obk
Add `#[rustc_no_mir_inline]` for standard library UB checks
should help with #121110 and also with #120848
Because the MIR inliner cannot know whether the checks are enabled or not, so inlining is an unnecessary compile time pessimization when debug assertions are disabled. LLVM knows whether they are enabled or not, so it can optimize accordingly without wasting time.
r? `@saethlin`
coverage: Rename `is_closure` to `is_hole`
Extracted from #121433, since I was having second thoughts about some of the other changes bundled in that PR, but these changes are still fine.
---
When refining covspans, we don't specifically care which ones represent closures; we just want to know which ones represent "holes" that should be carved out of other spans and then discarded.
(Closures are currently the only source of hole spans, but in the future we might want to also create hole spans for nested items and inactive `#[cfg(..)]` regions.)
``@rustbot`` label +A-code-coverage
When refining covspans, we don't specifically care which ones represent
closures; we just want to know which ones represent "holes" that should be
carved out of other spans and then discarded.
(Closures are currently the only source of hole spans, but in the future we
might want to also create hole spans for nested items and inactive `#[cfg(..)]`
regions.)
