rustc_mir: insert a dummy access to places being matched on, when building MIR.
Fixes#47412 by adding a `_dummy = Discriminant(place)` before each `match place {...}`.
r? @nikomatsakis
Fixes the hash test to recognize that MirValidated can change when changing
around labels, and add a new test that makes sure we're lowering loop statements
correctly.
As opposed to using weirdness involving pretending the body block
is the loop block. This does not pass tests
This commit is [ci skip] because I know it doesn't pass tests yet.
Somehow this commit introduces nondeterminism into the handling of
loops.
Implicit coercions from references to pointers were lowered to slightly
different Mir than explicit casts (e.g. 'foo as *mut T'). This resulted
in certain uses of self-referential structs compiling correctly when an
explicit cast was used, but not when the implicit coercion was used.
To fix this, this commit adds an outer 'Use' expr when applying a
raw-ptr-borrow adjustment. This makes the lowered Mir for coercions
identical to that of explicit coercions, allowing the original code to
compile regardless of how the raw ptr cast occurs.
Fixes#47722
NLL feature complete (adds `feature(nll)`)!
This is the final PR for the nll-master branch; it brings over all remaining content.
The contents of the branch include:
- track causal information and use it to report extended errors
- handle `impl Trait` in NLL code
- improve printing of outlives errors
- add `#![feature(nll)]` and some more sample tests
The commits should for the most part build independently.
r? @pnkfelix (and/or @arielb1)
Fix -Z lower_128bit_ops handling of statics
Avoids ICEs such as the following:
> error: internal compiler error: src\librustc_metadata\cstore_impl.rs:131:
> get_optimized_mir: missing MIR for `DefId(8/0:40 ~
> compiler_builtins[9532]::int[0]::addsub[0]::rust_i128_addo[0])`
r? @nagisa
cc #45676 @est31
Avoids ICEs such as the following:
error: internal compiler error: src\librustc_metadata\cstore_impl.rs:131:
get_optimized_mir: missing MIR for `DefId(8/0:40 ~
compiler_builtins[9532]::int[0]::addsub[0]::rust_i128_addo[0])`
The input/output types found in `UniversalRegions` are not normalized.
The old code used to assign them directly into the MIR, which would
lead to errors when there was a projection in a argument or return
type. This also led to some special cases in the `renumber` code.
We now renumber uniformly but then pass the input/output types into
the MIR type-checker, which equates them with the types found in MIR.
This allows us to normalize at the same time.
NLL: improve inference with flow results, represent regions with bitsets, and more
This PR begins with a number of edits to the NLL code and then includes a large number of smaller refactorings (these refactorings ought not to change behavior). There are a lot of commits here, but each is individually simple. The goal is to land everything up to but not including the changes to how we handle closures, which are conceptually more complex.
The NLL specific changes are as follows (in order of appearance):
**Modify the region inferencer's approach to free regions.** Previously, for each free region (lifetime parameter) `'a`, it would compute the set of other free regions that `'a` outlives (e.g., if we have `where 'a: 'b`, then this set would be `{'a, 'b}`). Then it would mark those free regions as "constants" and report an error if inference tried to extend `'a` to include any other region (e.g., `'c`) that is not in that outlives set. In this way, the value of `'a` would never grow beyond the maximum that could type check. The new approach is to allow `'a` to grow larger. Then, after the fact, we check over the value of `'a` and see what other free regions it is required to outlive, and we check that those outlives relationships are justified by the where clauses in scope etc.
**Modify constraint generation to consider maybe-init.** When we have a "drop-live" variable `x` (i.e., a variable that will be dropped but will not be otherwise used), we now consider whether `x` is "maybe initialized" at that point. If not, then we know the drop is a no-op, and we can allow its regions to be dead. Due to limitations in the fragment code, this currently only works at the level of entire variables.
**Change representation of regions to use a `BitMatrix`.** We used to use a `BTreeSet`, which was rather silly. We now use a MxN matrix of bits, where `M` is the number of variables and `N` is the number of possible elements in each set (size of the CFG + number of free regions).
The remaining commits (starting from
extract the `implied_bounds` code into a helper function ") are all "no-op" refactorings, I believe.
~~One concern I have is with the commit "with -Zverbose, print all details of closure substs"; this commit seems to include some "internal" stuff in the mir-dump files, such as internal interner numbers, that I fear may vary by platform. Annoying. I guess we will see.~~ (I removed this commit.)
As for reviewer, @arielb1 has been reviewing the PRs, and they are certainly welcome to review this one too. But I figured it'd maybe be good to have more people taking a look and being familiar with this code, so I'll "nominate" @pnkfelix .
r? @pnkfelix
We now visit just the stuff in the CFG, and we add liveness
constraints for all the random types, regions etc that appear within
rvalues and statements.
Rather than declaring some region variables to be constant, and
reporting errors when they would have to change, we instead populate
each free region X with a minimal set of points (the CFG plus end(X)),
and then we let inference do its thing. This may add other `end(Y)`
points into X; we can then check after the fact that indeed `X: Y`
holds.
This requires a bit of "blame" detection to find where the bad
constraint came from: we are currently using a pretty dumb
algorithm. Good place for later expansion.
Fix CopyPropagation regression (2)
Remaining part of MIR copyprop regression by (I think) #45380, which I missed in #45753.
```rust
fn foo(mut x: i32) -> i32 {
let y = x;
x = 123; // `x` is assigned only once in MIR, but cannot be propagated to `y`
y
}
```
So any assignment to an argument cannot be propagated.
This simplifies analysis and borrow-checking because liveness at the
resume point can always be simply propagated.
Later on, the "dead" Resumes are removed.
This commit allocates a builder to running wasm32 tests on Travis. Not all test
suites pass right now so this is starting out with just the run-pass and the
libcore test suites. This'll hopefully give us a pretty broad set of coverage
for integration in rustc itself as well as a somewhat broad coverage of the llvm
backend itself through integration/unit tests.
Make accesses to fields of packed structs unsafe
To handle packed structs with destructors (which you'll think are a rare
case, but the `#[repr(packed)] struct Packed<T>(T);` pattern is
ever-popular, which requires handling packed structs with destructors to
avoid monomorphization-time errors), drops of subfields of packed
structs should drop a local move of the field instead of the original
one.
That's it, I think I'll use a strategy suggested by @Zoxc, where this mir
```
drop(packed_struct.field)
```
is replaced by
```
tmp0 = packed_struct.field;
drop tmp0
```
cc #27060 - this should deal with that issue after codegen of drop glue
is updated.
The new errors need to be changed to future-compatibility warnings, but
I'll rather do a crater run first with them as errors to assess the
impact.
cc @eddyb
Things which still need to be done for this:
- [ ] - handle `repr(packed)` structs in `derive` the same way I did in `Span`, and use derive there again
- [ ] - implement the "fix packed drops" pass and call it in both the MIR shim and validated MIR pipelines
- [ ] - do a crater run
- [ ] - convert the errors to compatibility warnings
Add a MIR pass to lower 128-bit operators to lang item calls
Runs only with `-Z lower_128bit_ops` since it's not hooked into targets yet.
This isn't really useful on its own, but the declarations for the lang items need to be in the compiler before compiler-builtins can be updated to define them, so this is part 1 of at least 3.
cc https://github.com/rust-lang/rust/issues/45676 @est31 @nagisa
move closure kind, signature into `ClosureSubsts`
Instead of using side-tables, store the closure-kind and signature in the substitutions themselves. This has two key effects:
- It means that the closure's type changes as inference finds out more things, which is very nice.
- As a result, it avoids the need for the `freshen_closure_like` code (though we still use it for generators).
- It avoids cyclic closures calls.
- These were never meant to be supported, precisely because they make a lot of the fancy inference that we do much more complicated. However, due to an oversight, it was previously possible -- if challenging -- to create a setup where a closure *directly* called itself (see e.g. #21410).
We have to see what the effect of this change is, though. Needs a crater run. Marking as [WIP] until that has been assessed.
r? @arielb1
* The overflow-checking shift items need to take a full 128-bit type, since they need to be able to detect idiocy like `1i128 << (1u128 << 127)`
* The unchecked ones just take u32, like the `*_sh?` methods in core
* Because shift-by-anything is allowed, cast into a new local for every shift
