Skip `Drop` terminators for enum variants without drop glue
Split out from #68528.
When doing drop elaboration for an `enum` that may or may not be moved out of (an open drop), we check the discriminant of the `enum` to see whether the live variant has any drop flags and then check the drop flags to see whether we need to drop each field. Sometimes, however, the live
variant has no move paths and thus no drop flags. In this case, we still emit a drop terminator
for the entire enum after checking the enum discriminant. This drop shim will check the discriminant of the enum *again* and then drop the fields of the active variant. If the active variant has no drop glue, nothing will be done.
This commit skips emitting the drop terminator during drop elaboration when the "otherwise" variants, those without move paths, have no drop glue. A common example of this scenario is when an `Option` is moved from, since `Option::None` never needs drop glue. Below is a fragment the pre-codegen CFG for `Option::unwrap_or` in which we check the drop flag (`_5`) for `self` (`_1`), before and after the change.
Before:
After:
This change doesn't do much on its own, but it is a prerequisite to get the perf gains from #68528.
cc @arielb1
Rename `libsyntax` to `librustc_ast`
This was the last rustc crate that wasn't following the `rustc_*` naming convention.
Follow-up to https://github.com/rust-lang/rust/pull/67763.
rustc_parse: Tweak the function parameter name check
The function doesn't need a full token, only its edition.
Noticed while implementing https://github.com/rust-lang/rust/pull/69384.
I'm still not sure whether normalized or unnormalized token is a better fit for the edition check here, so https://github.com/rust-lang/rust/pull/69384 and this PR just keep the status quo behavior.
r? @Centril
Correct comment to match behavior
Corrects the header comment on `saturating_duration_since` to match the behavior of returning 0 if the other timestamp is _later_ than the invocant, not earlier,
This is purely a documentation change, so hopefully it doesn't require an issue; if it does, I'll open one and resubmit.
fix aliasing violation in align_to_mut
Fixes https://github.com/rust-lang/rust/issues/68549
I decided to add the testcase here to make it all one PR, but if you prefer I can also add that test case in the Miri repo instead.
perf: Buffer stderr when writing json errors/warnings
Since `stderr` is unbuffered, writing out json messages actually take up
about ~10%/0.1s of the runtime of the `inflate` benchmark as it generates a fair number of warnings.
cc #64413
Fix no_std detection for target triples
The current check for wether a target is no_std or not is matching for the string `-none-` in a target triple. This doesn't work for triples that end in `-none`, like `aarch64-unknown-none`.
Fix this by matching for `-none` instead.
I checked for all the current target triples containing `none`, and this should not generate any false positives.
This fixes an issue encountered in https://github.com/rust-lang/rust/pull/68334
Use assert_ne in hash tests
The hash tests were written before the assert_ne macro was added to the standard library. The assert_ne macro provides better output in case of a failure.
