Let's avoid using two different terms for the same thing -- let's just call it "provenance" everywhere.
In Miri, provenance consists of an AllocId and an SbTag (Stacked Borrows tag), which made this even more confusing.
Interpret: AllocRange Debug impl, and use it more consistently
The two commits are pretty independent but it did not seem worth having two PRs for them.
r? ``@oli-obk``
The interning of const allocations visits the mplace looking for references
to intern. Walking big aggregates like big static arrays can be costly,
so we only do it if the allocation we're interning contains references
or interior mutability.
Walking ZSTs was avoided before, and this optimization is now applied
to cases where there are no references/relocations either.
We now have an infallible function that also tells us which kind of allocation we are talking about.
Also we do longer have to distinguish between data and function allocations for liveness.
use precise spans for recursive const evaluation
This fixes https://github.com/rust-lang/rust/issues/73283 by using a `TyCtxtAt` with a more precise span when the interpreter recursively calls itself. Hopefully such calls are sufficiently rare that this does not cost us too much performance.
(In theory, cycles can also arise through layout computation, as layout can depend on consts -- but layout computation happens all the time so we'd have to do something to not make this terrible for performance.)
Ensure we never consider the null pointer dereferencable
This replaces the checks that are being removed in https://github.com/rust-lang/rust/pull/97188. Those checks were too early and hence incorrect.
Remove unneeded null pointer asserts in ptr2int casts
This removes an assert that a pointer with address 0 has no provenance. This change is needed to support permissive provenance work in Miri, and seems justified by `ptr.with_addr(0)` working and a discussion on Zulip regarding LLVM semantics.
r? `@RalfJung`
Initial work on Miri permissive-exposed-provenance
Rustc portion of the changes for portions of a permissive ptr-to-int model for Miri. The main changes here are changing `ptr_get_alloc` and `get_alloc_id` to return an Option, and also making ptr-to-int casts have an expose side effect.
Miri provenance cleanup
Reviewing https://github.com/rust-lang/rust/pull/95826 by ``@carbotaniuman`` made me realize that we could clean things up a little here.
``@carbotaniuman`` please let me know if you're okay with landing this (it will create a lot of conflicts with your PR), or if you'd prefer incorporating the ideas from this PR into yours. I think we want to end up in a situation where the function you called `ptr_reify_alloc` returns just two things, a concrete tag and an offset. Getting an `AllocId` from a concrete tag should be infallible like now. However a concrete tag and `Tag` don't have to be the same type.
r? ``@oli-obk``
CTFE/Miri: detect out-of-bounds pointers in offset_from
Also I became uneasy with aggressively doing `try_to_int` here -- this will always succeed on Miri, leading to the wrong codepath being taken. We should rather try to convert them both to pointers, and use the integer path as a fallback, so that's what I implemented now.
Hiding whitespaces helps with the diff.
Fixes https://github.com/rust-lang/miri/issues/1950
r? ``@oli-obk``
Currently some `Allocation`s are interned, some are not, and it's very
hard to tell at a use point which is which.
This commit introduces `ConstAllocation` for the known-interned ones,
which makes the division much clearer. `ConstAllocation::inner()` is
used to get the underlying `Allocation`.
In some places it's natural to use an `Allocation`, in some it's natural
to use a `ConstAllocation`, and in some places there's no clear choice.
I've tried to make things look as nice as possible, while generally
favouring `ConstAllocation`, which is the type that embodies more
information. This does require quite a few calls to `inner()`.
The commit also tweaks how `PartialOrd` works for `Interned`. The
previous code was too clever by half, building on `T: Ord` to make the
code shorter. That caused problems with deriving `PartialOrd` and `Ord`
for `ConstAllocation`, so I changed it to build on `T: PartialOrd`,
which is slightly more verbose but much more standard and avoided the
problems.
