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Add fast path to is_descendant_of #91043

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merged 2 commits into from
Nov 29, 2021
Merged

Add fast path to is_descendant_of #91043

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768cfac
Add fast path to is_descendant_of
camsteffen Nov 19, 2021
ac8d514
Add parent crate assert to register_expn_id
camsteffen Nov 28, 2021
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22 changes: 20 additions & 2 deletions compiler/rustc_span/src/hygiene.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -264,7 +264,15 @@ impl ExpnId {
HygieneData::with(|data| data.expn_data(self).clone())
}

#[inline]
pub fn is_descendant_of(self, ancestor: ExpnId) -> bool {
// a few "fast path" cases to avoid locking HygieneData
if ancestor == ExpnId::root() || ancestor == self {
return true;
}
if ancestor.krate != self.krate {
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return false;
}
HygieneData::with(|data| data.is_descendant_of(self, ancestor))
}

Expand Down Expand Up @@ -376,13 +384,22 @@ impl HygieneData {
}

fn is_descendant_of(&self, mut expn_id: ExpnId, ancestor: ExpnId) -> bool {
while expn_id != ancestor {
// a couple "fast path" cases to avoid traversing parents in the loop below
if ancestor == ExpnId::root() {
return true;
}
if expn_id.krate != ancestor.krate {
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return false;
}
loop {
if expn_id == ancestor {
return true;
}
if expn_id == ExpnId::root() {
return false;
}
expn_id = self.expn_data(expn_id).parent;
}
true
}

fn normalize_to_macros_2_0(&self, ctxt: SyntaxContext) -> SyntaxContext {
Expand Down Expand Up @@ -1223,6 +1240,7 @@ pub fn register_expn_id(
data: ExpnData,
hash: ExpnHash,
) -> ExpnId {
debug_assert!(data.parent == ExpnId::root() || krate == data.parent.krate);
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Should this be a regular assert?

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Seems fine as is, the assert will be removed anyway when root expansions start keeping their crate IDs.

let expn_id = ExpnId { krate, local_id };
HygieneData::with(|hygiene_data| {
let _old_data = hygiene_data.foreign_expn_data.insert(expn_id, data);
Expand Down