Currently, dataflow begins by visiting each block in order of ID
(`BasicBlock(0)`, `BasicBlock(1)`, etc.). This PR changes that initial
iteration to reverse post-order. This ensures that the effects of all
predecessors will be applied before a basic block is visited if the CFG
has no back-edges, and should result in less total iterations even when
back-edges exist. This should not change the results of dataflow
analysis.
The current ordering for basic blocks is pretty close to RPO
already--`BasicBlock(0)` is already the start block, so the gains from
this are pretty small, especially since we need to do an extra traversal
up front.
Note that some basic blocks are unreachable from the `START_BLOCK`
during dataflow. We add these blocks to the work queue as well to
preserve the original behavior.
This commit moves a test out of libstd which is causing deadlocks on
musl on CI. Looks like the recent update in musl versions brings in some
internal updates to musl which makes `setgid` and `setuid` invalid to
call after a `fork` in a multithreaded program. The issue seen here is
that the child thread was attempting to grab a lock held by a
nonexistent thread, meaning that the child process simply deadlocked
causing the whole test to deadlock.
This commit moves the test to its own file with no threads which should
work.
We've seen quite a few issues with spurious illegal instructions getting
executed on OSX on CI recently. For whatever reason `cc` itself is
executing an illegal instruction and we're not really getting any other
information about what's happening. Since we're already retrying the
linker when it segfaults, let's just continue to retry everything and
automatically reinvoke the linker when it fails with an illegal instruction.
For `libc` types that will be initialized in FFI calls, we can just use
`MaybeUninit` and then pass around raw pointers.
For `sun_path_offset()`, which really wants `offset_of`, all callers
have a real `sockaddr_un` available, so we can use that reference.
ci: Sync AppVeyor/Travis with Azure configuration
Manually make sure that we do the same thing across all the services,
uncovering one spot where we needed to pass one more configure flag on
Azure but otherwise we're good to go!
ci: Publish toolstate changes from Azure
This commit moves toolstate publishing from Travis to Azure. We've been
testing on azure for some time now and this works by deleting the Travis
config and updating the credentials used on Azure.
ci: Switch official `try` builds to happen on Azure
This commit switches the `try` builers to officially happen on Azure
Pipelines instead of Travis where they're currently run. This also cuts
back the number of builders to just the two we run on Travis, leaving
expansion as a possible future extension.
ci: Disable assertions in PR builds
The PR builder on Azure currently takes 2.5h which is a bit long, so
this commit disables debug assertions and llvm assertions in an attempt
to speed up that builder and have PR builds come back a bit more
quickly. Other builders continue to enable debug assertions and test the
compiler there.
Manually make sure that we do the same thing across all the services,
uncovering one spot where we needed to pass one more configure flag on
Azure but otherwise we're good to go!
This commit moves toolstate publishing from Travis to Azure. We've been
testing on azure for some time now and this works by deleting the Travis
config and updating the credentials used on Azure.
This commit switches the `try` builers to officially happen on Azure
Pipelines instead of Travis where they're currently run. This also cuts
back the number of builders to just the two we run on Travis, leaving
expansion as a possible future extension.
The PR builder on Azure currently takes 2.5h which is a bit long, so
this commit disables debug assertions and llvm assertions in an attempt
to speed up that builder and have PR builds come back a bit more
quickly. Other builders continue to enable debug assertions and test the
compiler there.
Clean up MIR drop generation
* Don't assign twice to the destination of a `while` loop containing a `break` expression
* Use `as_temp` to evaluate statement expression
* Avoid consecutive `StorageLive`s for the condition of a `while` loop
* Unify `return`, `break` and `continue` handling, and move it to `scopes.rs`
* Make some of the `scopes.rs` internals private
* Don't use `Place`s that are always `Local`s in MIR drop generation
Closes#42371Closes#61579Closes#61731Closes#61834Closes#61910Closes#62115
rustc: correctly transform memory_index mappings for generators.
Fixes#61793, closes#62011 (previous attempt at fixing #61793).
During #60187, I made the mistake of suggesting that the (re-)computation of `memory_index` in `ty::layout`, after generator-specific logic split/recombined fields, be done off of the `offsets` of those fields (which needed to be computed anyway), as opposed to the `memory_index`.
`memory_index` maps each field to its in-memory order index, which ranges over the same `0..n` values as the fields themselves, making it a bijective mapping, and more specifically a permutation (indeed, it's the permutation resulting from field reordering optimizations).
Each field has an unique "memory index", meaning a sort based on them, even an unstable one, will not put them in the wrong order. But offsets don't have that property, because of ZSTs (which do not increase the offset), so sorting based on the offset of fields alone can (and did) result in wrong orders.
Instead of going back to sorting based on (slices/subsets of) `memory_index`, or special-casing ZSTs to make sorting based on offsets produce the right results (presumably), as #62011 does, I opted to drop sorting altogether and focus on `O(n)` operations involving *permutations*:
* a permutation is easily inverted (see the `invert_mapping` `fn`)
* an `inverse_memory_index` was already employed in other parts of the `ty::layout` code (that is, a mapping from memory order to field indices)
* inverting twice produces the original permutation, so you can invert, modify, and invert again, if it's easier to modify the inverse mapping than the direct one
* you can modify/remove elements in a permutation, as long as the result remains dense (i.e. using every integer in `0..len`, without gaps)
* for splitting a `0..n` permutation into disjoint `0..x` and `x..n` ranges, you can pick the elements based on a `i < x` / `i >= x` predicate, and for the latter, also subtract `x` to compact the range to `0..n-x`
* in the general case, for taking an arbitrary subset of the permutation, you need a renumbering from that subset to a dense `0..subset.len()` - but notably, this is still `O(n)`!
* you can merge permutations, as long as the result remains disjoint (i.e. each element is unique)
* for concatenating two `0..n` and `0..m` permutations, you can renumber the elements in the latter to `n..n+m`
* some of these operations can be combined, and an inverse mapping (be it a permutation or not) can still be used instead of a forward one by changing the "domain" of the loop performing the operation
I wish I had a nicer / more mathematical description of the recombinations involved, but my focus was to fix the bug (in a way which preserves information more directly than sorting would), so I may have missed potential changes in the surrounding generator layout code, that would make this all more straight-forward.
r? @tmandry
