* Fix miscompile from functions mutating `VMContext`
This commit fixes a miscompilation in Wasmtime on LLVM 16 where methods
on `Instance` which mutated the state of the internal `VMContext` were
optimized to not actually mutate the state. The root cause of this issue
is a change in LLVM which takes advantage of `noalias readonly` pointers
which is how `&self` methods are translated. This means that `Instance`
methods which take `&self` but actually mutate the `VMContext` end up
being undefined behavior from LLVM's point of view, meaning that the
writes are candidate for removal.
The fix applied here is intended to be a temporary one while a more
formal fix, ideally backed by `cargo miri` verification, is implemented
on `main`. The fix here is to change the return value of
`vmctx_plus_offset` to return `*const T` instead of `*mut T`. This
caused lots of portions of the runtime code to stop compiling because
mutations were indeed happening. To cover these a new
`vmctx_plus_offset_mut` method was added which notably takes `&mut self`
instead of `&self`. This forced all callers which may mutate to reflect
the `&mut self` requirement, propagating that outwards.
This fixes the miscompilation with LLVM 16 in the immediate future and
should be at least a meager line of defense against issues like this in
the future. This is not a long-term fix, though, since `cargo miri`
still does not like what's being done in `Instance` and with
`VMContext`. That fix is likely to be more invasive, though, so it's
being deferred to later.
* Update release notes
* Fix release date
Alex Crichton
4b9ce0e579