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Merged
merged 1 commit into from
Aug 9, 2020
Merged

Hash parent ExpnData #75134

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8 changes: 5 additions & 3 deletions src/librustc_span/hygiene.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -80,8 +80,6 @@ pub enum Transparency {
Opaque,
}

pub(crate) const NUM_TRANSPARENCIES: usize = 3;

impl ExpnId {
pub fn fresh(expn_data: Option<ExpnData>) -> Self {
HygieneData::with(|data| data.fresh_expn(expn_data))
Expand Down Expand Up @@ -618,6 +616,11 @@ impl SyntaxContext {
HygieneData::with(|data| data.expn_data(data.outer_expn(self)).clone())
}

#[inline]
pub fn outer_mark(self) -> (ExpnId, Transparency) {
HygieneData::with(|data| data.outer_mark(self))
}

#[inline]
pub fn outer_mark_with_data(self) -> (ExpnId, Transparency, ExpnData) {
HygieneData::with(|data| {
Expand Down Expand Up @@ -667,7 +670,6 @@ pub struct ExpnData {
/// The kind of this expansion - macro or compiler desugaring.
pub kind: ExpnKind,
/// The expansion that produced this expansion.
#[stable_hasher(ignore)]
pub parent: ExpnId,
/// The location of the actual macro invocation or syntax sugar , e.g.
/// `let x = foo!();` or `if let Some(y) = x {}`
Expand Down
64 changes: 34 additions & 30 deletions src/librustc_span/lib.rs
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Expand Up @@ -32,8 +32,8 @@ pub mod edition;
use edition::Edition;
pub mod hygiene;
pub use hygiene::SyntaxContext;
use hygiene::Transparency;
pub use hygiene::{DesugaringKind, ExpnData, ExpnId, ExpnKind, ForLoopLoc, MacroKind};
use hygiene::{Transparency, NUM_TRANSPARENCIES};
pub mod def_id;
use def_id::{CrateNum, DefId, LOCAL_CRATE};
mod span_encoding;
Expand Down Expand Up @@ -1814,47 +1814,51 @@ impl<CTX: HashStableContext> HashStable<CTX> for SyntaxContext {
TAG_NO_EXPANSION.hash_stable(ctx, hasher);
} else {
TAG_EXPANSION.hash_stable(ctx, hasher);
let (expn_id, transparency) = self.outer_mark();
expn_id.hash_stable(ctx, hasher);
transparency.hash_stable(ctx, hasher);
}
}
}

// Since the same expansion context is usually referenced many
// times, we cache a stable hash of it and hash that instead of
// recursing every time.
thread_local! {
static CACHE: RefCell<Vec<Option<[Option<u64>; NUM_TRANSPARENCIES]>>> = Default::default();
}
impl<CTX: HashStableContext> HashStable<CTX> for ExpnId {
fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
// Since the same expansion context is usually referenced many
// times, we cache a stable hash of it and hash that instead of
// recursing every time.
thread_local! {
static CACHE: RefCell<Vec<Option<Fingerprint>>> = Default::default();
}

let sub_hash: u64 = CACHE.with(|cache| {
let (expn_id, transparency, _) = self.outer_mark_with_data();
let index = expn_id.as_u32() as usize;
const TAG_ROOT: u8 = 0;
const TAG_NOT_ROOT: u8 = 1;

if let Some(sub_hash_cache) = cache.borrow().get(index).copied().flatten() {
if let Some(sub_hash) = sub_hash_cache[transparency as usize] {
return sub_hash;
}
}
if *self == ExpnId::root() {
TAG_ROOT.hash_stable(ctx, hasher);
return;
}

let new_len = index + 1;
TAG_NOT_ROOT.hash_stable(ctx, hasher);
let index = self.as_u32() as usize;

let mut hasher = StableHasher::new();
expn_id.expn_data().hash_stable(ctx, &mut hasher);
transparency.hash_stable(ctx, &mut hasher);
let res = CACHE.with(|cache| cache.borrow().get(index).copied().flatten());

if let Some(res) = res {
res.hash_stable(ctx, hasher);
} else {
let new_len = index + 1;

let sub_hash: Fingerprint = hasher.finish();
let sub_hash = sub_hash.to_smaller_hash();
let mut sub_hasher = StableHasher::new();
self.expn_data().hash_stable(ctx, &mut sub_hasher);
let sub_hash: Fingerprint = sub_hasher.finish();

CACHE.with(|cache| {
let mut cache = cache.borrow_mut();
if cache.len() < new_len {
cache.resize(new_len, None);
}
if let Some(mut sub_hash_cache) = cache[index] {
sub_hash_cache[transparency as usize] = Some(sub_hash);
} else {
let mut sub_hash_cache = [None; NUM_TRANSPARENCIES];
sub_hash_cache[transparency as usize] = Some(sub_hash);
cache[index] = Some(sub_hash_cache);
}
sub_hash
cache[index].replace(sub_hash).expect_none("Cache slot was filled");
});

sub_hash.hash_stable(ctx, hasher);
}
}
Expand Down