This PR is based on #17784, which fixes closure soundness problems in borrowck. Only the last two commits are unique to this PR.
My understanding of regionck is still evolving, so I'm not sure if this is the right approach. Feedback is appreciated.
- In `link_reborrowed_region`, we account for the ability of upvars to
change their mutability due to later processing. A map of recursive
region links we may want to establish in the future is maintained,
with the links being established when the mutability of the borrow
is adjusted.
- When asked to establish a region link for an upvar, we link it to
the region of the closure body. This creates the necessary
constraint to stop unsound reborrows from the closure environment.
This partially (maybe completely) solves issue #17403. Remaining work:
- This is only known to help with by-ref upvars. I have not looked at
by-value upvars yet to see if they can cause problems.
- The error diagnostics that result from failed region inference are
pretty inscrutible.
When an overloaded call expression has parameters but the function
object takes none, construct an array of formal argument types with
the arity of the call expression so that we don't fail by indexing out
of bounds later.
Closes#16939
- Unify the representations of `cat_upvar` and `cat_copied_upvar`
- In `link_reborrowed_region`, account for the ability of upvars to
change their mutability due to later processing. A map of recursive
region links we may want to establish in the future is maintained,
with the links being established when the kind of the borrow is
adjusted.
- When categorizing upvars, add an explicit deref that represents the
closure environment pointer for closures that do not take the
environment by value. The region for the implicit pointer is an
anonymous free region type introduced for this purpose. This
creates the necessary constraint to prevent unsound reborrows from
the environment.
- Add a note to categorizations to make it easier to tell when extra
dereferences have been inserted by an upvar without having to
perform deep pattern matching.
- Adjust borrowck to deal with the changes. Where `cat_upvar` and
`cat_copied_upvar` were previously treated differently, they are
now both treated roughly like local variables within the closure
body, as the explicit derefs now ensure proper behavior. However,
error diagnostics had to be changed to explicitly look through the
extra dereferences to avoid producing confusing messages about
references not present in the source code.
Closes issue #17403. Remaining work:
- The error diagnostics that result from failed region inference are
pretty inscrutible and should be improved.
Code like the following is now rejected:
let mut x = 0u;
let f = || &mut x;
let y = f();
let z = f(); // multiple mutable references to the same location
This also breaks code that uses a similar construction even if it does
not go on to violate aliasability semantics. Such code will need to
be reworked in some way, such as by using a capture-by-value closure
type.
[breaking-change]
This improves the spectralnorm shootout benchmark through a few vectors after
looking at the leading C implementation:
* The simd-based f64x2 is now used to parallelize a few computations
* RWLock usage has been removed. A custom `parallel` function was added as a
form of stack-based fork-join parallelism. I found that the contention on the
locks was high as well as hindering other optimizations.
This does, however, introduce one `unsafe` block into the benchmarks, which
previously had none.
In terms of timings, the before and after numbers are:
```
$ time ./shootout-spectralnorm-before
./shootout-spectralnorm-before 2.07s user 0.71s system 324% cpu 0.857 total
$ time ./shootout-spectralnorm-before 5500
./shootout-spectralnorm-before 5500 11.88s user 1.13s system 459% cpu 2.830 total
$ time ./shootout-spectralnorm-after
./shootout-spectralnorm-after 0.58s user 0.01s system 280% cpu 0.210 tota
$ time ./shootout-spectralnorm-after 5500
./shootout-spectralnorm-after 5500 3.55s user 0.01s system 455% cpu 0.783 total
```
AsciiStr::to_lower is now AsciiStr::to_lowercase and AsciiStr::to_upper is AsciiStr::to_uppercase to match Ascii trait.
Part of issue #17790.
This is my first pull request so let me know if anything is incorrect.
Thanks!
[breaking-changes]
Out goes reflection! This means your code will break if you used the `:?` format specifier, anything else from libdebug, or the `visit_tydesc` intrinsic directly.
Closes#18046.
[breaking-change]
Adds an `assume` intrinsic that gets translated to llvm.assume. It is
used on a boolean expression and allows the optimizer to assume that
the expression is true.
This implements #18051.
librustc: Improve method autoderef/deref/index behavior more, and enable IndexMut on mutable vectors.
This fixes a bug whereby the mutability fixups for method behavior were
not kicking in after autoderef failed to happen at any level. It also
adds support for `Index` to the fixer-upper.
Closes#12825.
r? @pnkfelix
LLVM generates wrong code (which may be an instance of compile-time UB) when
faced with types that take lots of memory - bigger than the address space.
Make using such types a trans error. While trans errors are bad, overbig
types are expected to be very rare.
Use the integer sizes LLVM uses, rather than having random projections
laying around. Sizes are u64, Alignments are u32, C_*int is target-dependent
but 64-bit is fine (the int -> C_int conversion is non-precision-losing,
but it can be preceded by `as int` conversions which are, so it is
somewhat ugly. However, being able to suffix a `u` to properly infer
integer types is nice).
