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Auto merge of #108709 - matthiaskrgr:rollup-j2tjbyx, r=matthiaskrgr

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Rollup of 8 pull requests

Successful merges:

 - #104549 (add -Zexport-executable-symbols to unstable book)
 - #108292 (Label opaque type for 'captures lifetime' error message)
 - #108540 (Add `Atomic*::from_ptr`)
 - #108634 (Add link to component dashboard)
 - #108647 (Remove dead pgo.sh file)
 - #108678 (Use `Option::as_slice` where applicable)
 - #108681 (Improve comments in `needs_process_obligation`.)
 - #108688 (Match unmatched backticks in library/)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
This commit is contained in:
bors 2023-03-03 22:45:58 +00:00
commit 70adb4e5b4
50 changed files with 341 additions and 324 deletions
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56
compiler/rustc_trait_selection/src/traits/fulfill.rs
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@ -212,36 +212,44 @@ impl<'a, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'tcx> {
/// Identifies whether a predicate obligation needs processing.
///
/// This is always inlined, despite its size, because it has a single
/// callsite and it is called *very* frequently.
/// This is always inlined because it has a single callsite and it is
/// called *very* frequently. Be careful modifying this code! Several
/// compile-time benchmarks are very sensitive to even small changes.
#[inline(always)]
fn needs_process_obligation(&self, pending_obligation: &Self::Obligation) -> bool {
// If we were stalled on some unresolved variables, first check whether
// any of them have been resolved; if not, don't bother doing more work
// yet.
match pending_obligation.stalled_on.len() {
// Match arms are in order of frequency, which matters because this
// code is so hot. 1 and 0 dominate; 2+ is fairly rare.
1 => {
let infer_var = pending_obligation.stalled_on[0];
self.selcx.infcx.ty_or_const_infer_var_changed(infer_var)
}
0 => {
// In this case we haven't changed, but wish to make a change.
true
}
_ => {
// This `for` loop was once a call to `all()`, but this lower-level
// form was a perf win. See #64545 for details.
(|| {
for &infer_var in &pending_obligation.stalled_on {
if self.selcx.infcx.ty_or_const_infer_var_changed(infer_var) {
return true;
}
let stalled_on = &pending_obligation.stalled_on;
match stalled_on.len() {
// This case is the hottest most of the time, being hit up to 99%
// of the time. `keccak` and `cranelift-codegen-0.82.1` are
// benchmarks that particularly stress this path.
1 => self.selcx.infcx.ty_or_const_infer_var_changed(stalled_on[0]),
// In this case we haven't changed, but wish to make a change. Note
// that this is a special case, and is not equivalent to the `_`
// case below, which would return `false` for an empty `stalled_on`
// vector.
//
// This case is usually hit only 1% of the time or less, though it
// reaches 20% in `wasmparser-0.101.0`.
0 => true,
// This case is usually hit only 1% of the time or less, though it
// reaches 95% in `mime-0.3.16`, 64% in `wast-54.0.0`, and 12% in
// `inflate-0.4.5`.
//
// The obvious way of writing this, with a call to `any()` and no
// closure, is currently slower than this version.
_ => (|| {
for &infer_var in stalled_on {
if self.selcx.infcx.ty_or_const_infer_var_changed(infer_var) {
return true;
}
false
})()
}
}
false
})(),
}
}