async closure coroutine by move body MirPass refactoring
Unsure about the last commit, but I think the other changes help in simplifying the control flow
Stop making any assumption about the projections applied to the upvars in the `ByMoveBody` pass
So it turns out that because of subtle optimizations like [`truncate_capture_for_optimization`](ab5bda1aa7/compiler/rustc_hir_typeck/src/upvar.rs (L2351)), we simply cannot make any assumptions about the shape of the projections applied to the upvar locals in a coroutine body.
So stop doing that -- the code is resilient to such projections, so the assertion really existed only to "protect against the unknown".
r? oli-obk
Fixes#123650
Re-enable the early otherwise branch optimization
Closes#95162. Fixes#119014.
This is the first part of #121397.
An invalid enum discriminant can come from anywhere. We have to check to see if all successors contain the discriminant statement. This should have a pass to hoist instructions.
r? cjgillot
Fix `ByMove` coroutine-closure shim (for 2021 precise closure capturing behavior)
This PR reworks the way that we perform the `ByMove` coroutine-closure shim to account for the fact that the upvars of the outer coroutine-closure and the inner coroutine might not line up due to edition-2021 closure capture rules changes.
Specifically, the number of upvars may differ *and/or* the inner coroutine may have additional projections applied to an upvar. This PR reworks the information we pass into the `ByMoveBody` MIR visitor to account for both of these facts.
I tried to leave comments explaining exactly what everything is doing, but let me know if you have questions.
r? oli-obk
Actually use the inferred `ClosureKind` from signature inference in coroutine-closures
A follow-up to https://github.com/rust-lang/rust/pull/123349, which fixes another subtle bug: We were not taking into account the async closure kind we infer during closure signature inference.
When I pass a closure directly to an arg like `fn(x: impl async FnOnce())`, that should have the side-effect of artificially restricting the kind of the async closure to `ClosureKind::FnOnce`. We weren't doing this -- that's a quick fix; however, it uncovers a second, more subtle bug with the way that `move`, async closures, and `FnOnce` interact.
Specifically, when we have an async closure like:
```
let x = Struct;
let c = infer_as_fnonce(async move || {
println!("{x:?}");
}
```
The outer closure captures `x` by move, but the inner coroutine still immutably borrows `x` from the outer closure. Since we've forced the closure to by `async FnOnce()`, we can't actually *do* a self borrow, since the signature of `AsyncFnOnce::call_once` doesn't have a borrowed lifetime. This means that all `async move` closures that are constrained to `FnOnce` will fail borrowck.
We can fix that by detecting this case specifically, and making the *inner* async closure `move` as well. This is always beneficial to closure analysis, since if we have an `async FnOnce()` that's `move`, there's no reason to ever borrow anything, so `move` isn't artificially restrictive.
Cleanup: Rename `HAS_PROJECTIONS` to `HAS_ALIASES` etc.
The name of the bitflag `HAS_PROJECTIONS` and of its corresponding method `has_projections` is quite historical dating back to a time when projections were the only kind of alias type.
I think it's time to update it to clear up any potential confusion for newcomers and to reduce unnecessary friction during contributor onboarding.
r? types
coverage: Remove useless constants
After #122972 and #123419, these constants don't serve any useful purpose, so get rid of them.
`@rustbot` label +A-code-coverage
CFI: Support function pointers for trait methods
Adds support for both CFI and KCFI for function pointers to trait methods by attaching both concrete and abstract types to functions.
KCFI does this through generation of a `ReifyShim` on any function pointer for a method that could go into a vtable, and keeping this separate from `ReifyShim`s that are *intended* for vtable us by setting a `ReifyReason` on them.
CFI does this by setting both the concrete and abstract type on every instance.
This should land after #123024 or a similar PR, as it diverges the implementation of CFI vs KCFI.
r? `@compiler-errors`
Remove MIR unsafe check
Now that THIR unsafeck is enabled by default in stable I think we can remove MIR unsafeck entirely. This PR also removes safety information from MIR.
Rollup of 4 pull requests
Successful merges:
- #122411 ( Provide cabi_realloc on wasm32-wasip2 by default )
- #123349 (Fix capture analysis for by-move closure bodies)
- #123359 (Link against libc++abi and libunwind as well when building LLVM wrappers on AIX)
- #123388 (use a consistent style for links)
r? `@ghost`
`@rustbot` modify labels: rollup
Rename `UninhabitedEnumBranching` to `UnreachableEnumBranching`
Per [#120268](https://github.com/rust-lang/rust/pull/120268#discussion_r1517492060), I rename `UninhabitedEnumBranching` to `UnreachableEnumBranching` .
I solved some nits to add some comments.
I adjusted the workaround restrictions. This should be useful for `a <= b` and `if let Some/Ok(v)`. For enum with few variants, `early-tailduplication` should not cause compile time overhead.
r? RalfJung
Add `Ord::cmp` for primitives as a `BinOp` in MIR
Update: most of this OP was written months ago. See https://github.com/rust-lang/rust/pull/118310#issuecomment-2016940014 below for where we got to recently that made it ready for review.
---
There are dozens of reasonable ways to implement `Ord::cmp` for integers using comparison, bit-ops, and branches. Those differences are irrelevant at the rust level, however, so we can make things better by adding `BinOp::Cmp` at the MIR level:
1. Exactly how to implement it is left up to the backends, so LLVM can use whatever pattern its optimizer best recognizes and cranelift can use whichever pattern codegens the fastest.
2. By not inlining those details for every use of `cmp`, we drastically reduce the amount of MIR generated for `derive`d `PartialOrd`, while also making it more amenable to MIR-level optimizations.
Having extremely careful `if` ordering to μoptimize resource usage on broadwell (#63767) is great, but it really feels to me like libcore is the wrong place to put that logic. Similarly, using subtraction [tricks](https://graphics.stanford.edu/~seander/bithacks.html#CopyIntegerSign) (#105840) is arguably even nicer, but depends on the optimizer understanding it (https://github.com/llvm/llvm-project/issues/73417) to be practical. Or maybe [bitor is better than add](https://discourse.llvm.org/t/representing-in-ir/67369/2?u=scottmcm)? But maybe only on a future version that [has `or disjoint` support](https://discourse.llvm.org/t/rfc-add-or-disjoint-flag/75036?u=scottmcm)? And just because one of those forms happens to be good for LLVM, there's no guarantee that it'd be the same form that GCC or Cranelift would rather see -- especially given their very different optimizers. Not to mention that if LLVM gets a spaceship intrinsic -- [which it should](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Suboptimal.20inlining.20in.20std.20function.20.60binary_search.60/near/404250586) -- we'll need at least a rustc intrinsic to be able to call it.
As for simplifying it in Rust, we now regularly inline `{integer}::partial_cmp`, but it's quite a large amount of IR. The best way to see that is with 8811efa88b (diff-d134c32d028fbe2bf835fef2df9aca9d13332dd82284ff21ee7ebf717bfa4765R113) -- I added a new pre-codegen MIR test for a simple 3-tuple struct, and this PR change it from 36 locals and 26 basic blocks down to 24 locals and 8 basic blocks. Even better, as soon as the construct-`Some`-then-match-it-in-same-BB noise is cleaned up, this'll expose the `Cmp == 0` branches clearly in MIR, so that an InstCombine (#105808) can simplify that to just a `BinOp::Eq` and thus fix some of our generated code perf issues. (Tracking that through today's `if a < b { Less } else if a == b { Equal } else { Greater }` would be *much* harder.)
---
r? `@ghost`
But first I should check that perf is ok with this
~~...and my true nemesis, tidy.~~
KCFI needs to be able to tell which kind of `ReifyShim` it is examining
in order to decide whether to use a concrete type (`FnPtr` case) or an
abstract case (`Vtable` case). You can *almost* tell this from context,
but there is one case where you can't - if a trait has a method which is
*not* `#[track_caller]`, with an impl that *is* `#[track_caller]`, both
the vtable and a function pointer created from that method will be
`ReifyShim(def_id)`.
Currently, the reason is optional to ensure no additional unique
`ReifyShim`s are added without KCFI on. However, the case in which an
extra `ReifyShim` is created is sufficiently rare that this may be worth
revisiting to reduce complexity.
