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Optimize shallow_resolve_changed.

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It can be made even more specialized.
This commit is contained in:
Nicholas Nethercote 2019-12-06 15:36:14 +11:00
parent 7dbfb0a8ca
commit f5e68ccd09
1 changed files with 15 additions and 13 deletions
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28
src/librustc/infer/mod.rs
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@ -1617,38 +1617,40 @@ pub fn shallow_resolve(&mut self, typ: Ty<'tcx>) -> Ty<'tcx> {
// `resolver.shallow_resolve(ty) != ty`, but more efficient. It's always
// inlined, despite being large, because it has only two call sites that
// are extremely hot.
//
// Note that `typ` is always a `ty::Infer(_)`.
#[inline(always)]
pub fn shallow_resolve_changed(&mut self, typ: Ty<'tcx>) -> bool {
pub fn shallow_resolve_changed(&self, typ: Ty<'tcx>) -> bool {
match typ.kind {
ty::Infer(ty::TyVar(v)) => {
use self::type_variable::TypeVariableValue;
// See the comment in `shallow_resolve()`.
// If `inlined_probe` returns a `Known` value it never matches
// `typ`.
match self.infcx.type_variables.borrow_mut().inlined_probe(v) {
TypeVariableValue::Known { value: t } => self.fold_ty(t) != typ,
TypeVariableValue::Unknown { .. } => false,
TypeVariableValue::Known { .. } => true,
}
}
ty::Infer(ty::IntVar(v)) => {
match self.infcx.int_unification_table.borrow_mut().inlined_probe_value(v) {
Some(v) => v.to_type(self.infcx.tcx) != typ,
None => false,
}
// If inlined_probe_value returns a value it's always a
// `ty::Int(_)` or `ty::UInt(_)`, which nevers matches a
// `ty::Infer(_)`.
self.infcx.int_unification_table.borrow_mut().inlined_probe_value(v).is_some()
}
ty::Infer(ty::FloatVar(v)) => {
// If inlined_probe_value returns a value it's always a
// `ty::Float(_)`, which nevers matches a `ty::Infer(_)`.
//
// Not `inlined_probe_value(v)` because this call site is colder.
match self.infcx.float_unification_table.borrow_mut().probe_value(v) {
Some(v) => v.to_type(self.infcx.tcx) != typ,
None => false,
}
self.infcx.float_unification_table.borrow_mut().probe_value(v).is_some()
}
_ => false,
_ => unreachable!(),
}
}
}
impl<'a, 'tcx> TypeFolder<'tcx> for ShallowResolver<'a, 'tcx> {