Compile some CGUs in parallel at the start of codegen
This brings the compilation time for `syntex_syntax` from 11.542s to 10.453s with 6 threads in non-incremental debug mode. Just compiling `n` CGUs in parallel at the beginning of codegen seems sufficient to get rid of the staircase effect, at least for `syntex_syntax`.
Based on https://github.com/rust-lang/rust/pull/67777.
r? @michaelwoerister
cc @alexcrichton @Mark-Simulacrum
Rollup of 8 pull requests
Successful merges:
- #67666 (make use of pointer::is_null)
- #67806 (Extract `rustc_ast_passes`, move gating, & refactor linting)
- #68043 (Add some missing timers)
- #68074 (Add `llvm-skip-rebuild` flag to `x.py`)
- #68079 (Clarify suggestion for E0013)
- #68084 (Do not ICE on unicode next point)
- #68102 (Inline some conversion methods around OsStr)
- #68106 (Fix issue with using `self` module via indirection)
Failed merges:
r? @ghost
Inline some conversion methods around OsStr
Diff on the assembly of this snippet before and after this PR: https://www.diffchecker.com/NeGMjaJ2
```rust
use std::env;
use std::io;
use std::path::{Path, PathBuf};
pub fn cargo_home_with_cwd(cwd: &Path) -> io::Result<PathBuf> {
match env::var_os("CARGO_HOME").filter(|h| !h.is_empty()) {
Some(home) => {
let home = PathBuf::from(home);
if home.is_absolute() {
Ok(home)
} else {
Ok(cwd.join(&home))
}
}
_ => env::home_dir()
.map(|p| p.join(".cargo"))
.ok_or_else(|| io::Error::new(io::ErrorKind::Other, "could not find cargo home dir")),
}
}
```
Add `llvm-skip-rebuild` flag to `x.py`
This PR follows on from #67437 to complete the feature request from #65612.
Specifically it adds a new command-line flag, `--llvm-skip-rebuild`, which overrides both any value set in `config.toml` and the default value (`false`).
I'm not 100% confident that I've implemented the override in the "best" way, but I've checked it locally and it seems to work at least.
This option isn't currently mentioned in the Guide to Rustc Development. I'd be happy to write something on it if folk think that's worthwhile.
Extract `rustc_ast_passes`, move gating, & refactor linting
Based on https://github.com/rust-lang/rust/pull/67770.
This PR extracts a crate `rustc_ast_passes`:
- `ast_validation.rs`, which is contributed by `rustc_passes` (now only has HIR based passes) -- the goal here is to improve recompilation of the parser,
- `feature_gate.rs`, which is contributed by `syntax` and performs post-expansion-gating & final erroring for pre-expansion gating,
- `show_span`, which is contributed by `syntax`.
To facilitate this, we first have to also:
- Move `{leveled_}feature_err{_err}` from `syntax::feature_gate::check` into `rustc_session::parse`.
- Move `get_features` into `rustc_parse::config`, the only place it is used.
- Move some some lint datatypes and traits, e.g. `LintBuffer`, `BufferedEarlyLint`, `BuiltinLintDiagnostics`, `LintPass`, and `LintArray` into `rustc_session::lint`.
- Move all the hard-wired lint `static`s into `rustc_session::lint::builtin`.
This flag opts out of the min-const-fn checks entirely, which is usually
not what we want. The few cases where the flag is still necessary have
been annotated.
