From 76a80492489b9081944c6da793c509c4ad82f813 Mon Sep 17 00:00:00 2001
From: Stein Somers <git@steinsomers.be>
Date: Thu, 23 Jul 2020 20:15:47 +0200
Subject: [PATCH] Optimize btree's unwrap_unchecked
---
library/alloc/src/collections/btree/mod.rs | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/library/alloc/src/collections/btree/mod.rs b/library/alloc/src/collections/btree/mod.rs
index 543ff41a4d48d..36511a23581a0 100644
--- a/library/alloc/src/collections/btree/mod.rs
+++ b/library/alloc/src/collections/btree/mod.rs
@@ -13,15 +13,16 @@ trait Recover<Q: ?Sized> {
fn replace(&mut self, key: Self::Key) -> Option<Self::Key>;
}
+/// Same purpose as `Option::unwrap` but doesn't always guarantee a panic
+/// if the option contains no value.
+/// SAFETY: the caller must ensure that the option contains a value.
#[inline(always)]
pub unsafe fn unwrap_unchecked<T>(val: Option<T>) -> T {
- val.unwrap_or_else(|| {
- if cfg!(debug_assertions) {
- panic!("'unchecked' unwrap on None in BTreeMap");
- } else {
- unsafe {
- core::intrinsics::unreachable();
- }
- }
- })
+ if cfg!(debug_assertions) {
+ val.expect("'unchecked' unwrap on None in BTreeMap")
+ } else {
+ val.unwrap()
+ // val.unwrap_or_else(|| unsafe { core::hint::unreachable_unchecked() })
+ // ...is considerably slower
+ }
}