From f165f49d228d2582d2dbfd588c2729cfc9585eb0 Mon Sep 17 00:00:00 2001
From: Giles Cope <gilescope@gmail.com>
Date: Sat, 6 Feb 2021 19:14:13 +0000
Subject: [PATCH] Slight perf improvement on char::to_ascii_lowercase
---
library/core/benches/char/methods.rs | 10 ++++++++++
library/core/src/char/methods.rs | 6 ++++--
2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/library/core/benches/char/methods.rs b/library/core/benches/char/methods.rs
index a9a08a4d762..de4b63030fa 100644
--- a/library/core/benches/char/methods.rs
+++ b/library/core/benches/char/methods.rs
@@ -35,3 +35,13 @@ fn bench_to_digit_radix_var(b: &mut Bencher) {
.min()
})
}
+
+#[bench]
+fn bench_to_ascii_uppercase(b: &mut Bencher) {
+ b.iter(|| CHARS.iter().cycle().take(10_000).map(|c| c.to_ascii_uppercase()).min())
+}
+
+#[bench]
+fn bench_to_ascii_lowercase(b: &mut Bencher) {
+ b.iter(|| CHARS.iter().cycle().take(10_000).map(|c| c.to_ascii_lowercase()).min())
+}
diff --git a/library/core/src/char/methods.rs b/library/core/src/char/methods.rs
index 2baea7842a7..4c28d9cd673 100644
--- a/library/core/src/char/methods.rs
+++ b/library/core/src/char/methods.rs
@@ -1090,7 +1090,8 @@ impl char {
#[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
#[inline]
pub fn to_ascii_uppercase(&self) -> char {
- if self.is_ascii() { (*self as u8).to_ascii_uppercase() as char } else { *self }
+ // 6th bit dictates ascii case.
+ if self.is_ascii_lowercase() { ((*self as u8) & !0b10_0000u8) as char } else { *self }
}
/// Makes a copy of the value in its ASCII lower case equivalent.
@@ -1118,7 +1119,8 @@ impl char {
#[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
#[inline]
pub fn to_ascii_lowercase(&self) -> char {
- if self.is_ascii() { (*self as u8).to_ascii_lowercase() as char } else { *self }
+ // 6th bit dictates ascii case.
+ if self.is_ascii_uppercase() { ((*self as u8) | 0b10_0000u8) as char } else { *self }
}
/// Checks that two values are an ASCII case-insensitive match.