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Auto merge of #119693 - petrochenkov:cachemark, r=cjgillot

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macro_rules: Add an expansion-local cache to span marker

Most tokens in a macro body typically have the same syntax context.
So the cache should usually be hit.

This change can either be combined with https://github.com/rust-lang/rust/pull/119689, or serve as its alternative, depending on perf results.
This commit is contained in:
bors 2024-01-08 04:07:35 +00:00
commit 0ee9cfd54d
2 changed files with 14 additions and 5 deletions
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17
compiler/rustc_expand/src/mbe/transcribe.rs
View File

@ -13,19 +13,28 @@
use rustc_errors::{pluralize, PResult}; use rustc_errors::{pluralize, PResult};
use rustc_span::hygiene::{LocalExpnId, Transparency}; use rustc_span::hygiene::{LocalExpnId, Transparency};
use rustc_span::symbol::{sym, Ident, MacroRulesNormalizedIdent}; use rustc_span::symbol::{sym, Ident, MacroRulesNormalizedIdent};
use rustc_span::Span; use rustc_span::{Span, SyntaxContext};
use smallvec::{smallvec, SmallVec}; use smallvec::{smallvec, SmallVec};
use std::mem; use std::mem;
// A Marker adds the given mark to the syntax context. // A Marker adds the given mark to the syntax context.
struct Marker(LocalExpnId, Transparency); struct Marker(LocalExpnId, Transparency, FxHashMap<SyntaxContext, SyntaxContext>);
impl MutVisitor for Marker { impl MutVisitor for Marker {
const VISIT_TOKENS: bool = true; const VISIT_TOKENS: bool = true;
fn visit_span(&mut self, span: &mut Span) { fn visit_span(&mut self, span: &mut Span) {
*span = span.apply_mark(self.0.to_expn_id(), self.1) // `apply_mark` is a relatively expensive operation, both due to taking hygiene lock, and
// by itself. All tokens in a macro body typically have the same syntactic context, unless
// it's some advanced case with macro-generated macros. So if we cache the marked version
// of that context once, we'll typically have a 100% cache hit rate after that.
let Marker(expn_id, transparency, ref mut cache) = *self;
let data = span.data();
let marked_ctxt = *cache
.entry(data.ctxt)
.or_insert_with(|| data.ctxt.apply_mark(expn_id.to_expn_id(), transparency));
*span = data.with_ctxt(marked_ctxt);
} }
} }
@ -123,7 +132,7 @@ pub(super) fn transcribe<'a>(
// again, and we are done transcribing. // again, and we are done transcribing.
let mut result: Vec<TokenTree> = Vec::new(); let mut result: Vec<TokenTree> = Vec::new();
let mut result_stack = Vec::new(); let mut result_stack = Vec::new();
let mut marker = Marker(cx.current_expansion.id, transparency); let mut marker = Marker(cx.current_expansion.id, transparency, Default::default());
loop { loop {
// Look at the last frame on the stack. // Look at the last frame on the stack.

2
compiler/rustc_span/src/hygiene.rs
View File

@ -658,7 +658,7 @@ pub(crate) const fn from_u32(raw: u32) -> SyntaxContext {
} }
/// Extend a syntax context with a given expansion and transparency. /// Extend a syntax context with a given expansion and transparency.
pub(crate) fn apply_mark(self, expn_id: ExpnId, transparency: Transparency) -> SyntaxContext { pub fn apply_mark(self, expn_id: ExpnId, transparency: Transparency) -> SyntaxContext {
HygieneData::with(|data| data.apply_mark(self, expn_id, transparency)) HygieneData::with(|data| data.apply_mark(self, expn_id, transparency))
} }