From 65ea0ff29d32ca4fea30477f7fb1a1d43342dc26 Mon Sep 17 00:00:00 2001 From: Nicholas Nethercote 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 f252020bc3169..f26a6a5307401 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, 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()))))