From 65ea0ff29d32ca4fea30477f7fb1a1d43342dc26 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <nnethercote@mozilla.com>
Date: Fri, 4 May 2018 16:53:31 +1000
Subject: [PATCH] Optimize string handling in lit_token().
In the common case, the string value in a string literal Token is the
same as the string value in a string literal LitKind. (The exception is
when escapes or \r are involved.) This patch takes advantage of that to
avoid calling str_lit() and re-interning the string in that case. This
speeds up incremental builds for a few of the rustc-benchmarks, the best
by 3%.
---
src/libsyntax/parse/mod.rs | 23 +++++++++++++++++------
1 file changed, 17 insertions(+), 6 deletions(-)
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index f252020bc316..f26a6a530740 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -419,13 +419,24 @@ pub fn lit_token(lit: token::Lit, suf: Option<Symbol>, diag: Option<(Span, &Hand
token::Integer(s) => (false, integer_lit(&s.as_str(), suf, diag)),
token::Float(s) => (false, float_lit(&s.as_str(), suf, diag)),
- token::Str_(s) => {
- let s = Symbol::intern(&str_lit(&s.as_str(), diag));
- (true, Some(LitKind::Str(s, ast::StrStyle::Cooked)))
+ token::Str_(mut sym) => {
+ // If there are no characters requiring special treatment we can
+ // reuse the symbol from the Token. Otherwise, we must generate a
+ // new symbol because the string in the LitKind is different to the
+ // string in the Token.
+ let s = &sym.as_str();
+ if s.as_bytes().iter().any(|&c| c == b'\\' || c == b'\r') {
+ sym = Symbol::intern(&str_lit(s, diag));
+ }
+ (true, Some(LitKind::Str(sym, ast::StrStyle::Cooked)))
}
- token::StrRaw(s, n) => {
- let s = Symbol::intern(&raw_str_lit(&s.as_str()));
- (true, Some(LitKind::Str(s, ast::StrStyle::Raw(n))))
+ token::StrRaw(mut sym, n) => {
+ // Ditto.
+ let s = &sym.as_str();
+ if s.contains('\r') {
+ sym = Symbol::intern(&raw_str_lit(s));
+ }
+ (true, Some(LitKind::Str(sym, ast::StrStyle::Raw(n))))
}
token::ByteStr(i) => {
(true, Some(LitKind::ByteStr(byte_str_lit(&i.as_str()))))