From bb33bcce3559c5beab8f0aac7a7fb5b9dce4ea99 Mon Sep 17 00:00:00 2001
From: overlookmotel <557937+overlookmotel@users.noreply.github.com>
Date: Wed, 31 Jul 2024 00:29:00 +0000
Subject: [PATCH] perf(parser): speed up lexing non-decimal numbers (#4571)

Inline `Lexer::read_non_decimal` to reduce branching.
---
 crates/oxc_parser/src/lexer/kind.rs    | 1 +
 crates/oxc_parser/src/lexer/numeric.rs | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/crates/oxc_parser/src/lexer/kind.rs b/crates/oxc_parser/src/lexer/kind.rs
index df8aa3d0950e7..ecaa14248789c 100644
--- a/crates/oxc_parser/src/lexer/kind.rs
+++ b/crates/oxc_parser/src/lexer/kind.rs
@@ -206,6 +206,7 @@ impl Kind {
         )
     }
 
+    #[inline] // Inline into `read_non_decimal` - see comment there as to why
     pub fn matches_number_byte(self, b: u8) -> bool {
         match self {
             Decimal => b.is_ascii_digit(),
diff --git a/crates/oxc_parser/src/lexer/numeric.rs b/crates/oxc_parser/src/lexer/numeric.rs
index c9090e426a775..1655306e3f3e0 100644
--- a/crates/oxc_parser/src/lexer/numeric.rs
+++ b/crates/oxc_parser/src/lexer/numeric.rs
@@ -39,6 +39,10 @@ impl<'a> Lexer<'a> {
         self.check_after_numeric_literal(kind)
     }
 
+    // Inline into the 3 calls from `read_zero` so that value of `kind` is known
+    // and `kind.matches_number_byte` can be statically reduced to just the match arm
+    // that applies for this specific kind. `matches_number_byte` is also marked `#[inline]`.
+    #[inline]
     fn read_non_decimal(&mut self, kind: Kind) -> Kind {
         self.consume_char();