Clean up and streamline snapshot data structures
These commits clean up the snapshot structures a bit, so they are more consistent with each other and with the `ena` crate.
They also remove the `OpenSnapshot` and `CommittedSnapshot` entries in the undo log, just like I did for the `ena` crate in https://github.com/rust-lang-nursery/ena/pull/14. This PR in combination with that `ena` PR reduces instruction counts by up to 6% on benchmarks.
r? @nikomatsakis. Note that this isn't quite ready for landing, because the `ena` dependency in the first commit needs to be updated once https://github.com/rust-lang-nursery/ena/pull/14 lands. But otherwise it should be good.
They're not strictly necessary, and they result in the `Vec` being
allocated even for the trivial (and common) case where a
`start_snapshot` is immediately followed by a `commit` or `rollback_to`.
The commit also removes a now-unnecessary argument of
`pop_placeholders()`.
They're not strictly necessary, and they result in the `Vec` being
allocated even for the trivial (and common) case where a
`start_snapshot` is immediately followed by a `commit` or `rollback_to`.
Because it's as useless as its name suggests.
This commit also renames `UndoLog::Noop` as `UndoLog::Purged`, because
(a) that's a more descriptive name and (b) it matches the name used in
similar code in `librustc/infer/region_constraints/mod.rs`.
Cleanup from lexical MIR borrowck removal
Lexical MIR borrowck was removed months ago now, and `EndRegion`s are no longer used for MIRI verification.
* Remove `rustc::mir::StatementKind::EndRegion` and the `-Zemit_end_regions` flag
* Use `RegionVid` instead of `Region` in BorrowSet
* Rewrite drop generation to create fewer goto terminators.
r? @nikomatsakis
On Windows, the high-resolution timestamp api doesn't seem to always be
monotonic. This can cause panics when the self-profiler uses the
`Instant` api to find elapsed time.
Work around this by detecting the case where now is less than the start
time and just use 0 elapsed ticks as the measurement.
Fixes#51648
