From e4b4d18f589b2d0cfcf244124ab43da34a3d8794 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jakub=20Ber=C3=A1nek?= <berykubik@gmail.com>
Date: Mon, 25 Oct 2021 08:26:00 +0200
Subject: [PATCH] Use SmallVec in Hash map stable hashing

---
 compiler/rustc_data_structures/src/stable_hasher.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/compiler/rustc_data_structures/src/stable_hasher.rs b/compiler/rustc_data_structures/src/stable_hasher.rs
index 354f9dd93cc4d..b3958af7a4d50 100644
--- a/compiler/rustc_data_structures/src/stable_hasher.rs
+++ b/compiler/rustc_data_structures/src/stable_hasher.rs
@@ -552,7 +552,8 @@ pub fn hash_stable_hashmap<HCX, K, V, R, SK, F>(
     SK: HashStable<HCX> + Ord,
     F: Fn(&K, &HCX) -> SK,
 {
-    let mut entries: Vec<_> = map.iter().map(|(k, v)| (to_stable_hash_key(k, hcx), v)).collect();
+    let mut entries: SmallVec<[_; 3]> =
+        map.iter().map(|(k, v)| (to_stable_hash_key(k, hcx), v)).collect();
     entries.sort_unstable_by(|&(ref sk1, _), &(ref sk2, _)| sk1.cmp(sk2));
     entries.hash_stable(hcx, hasher);
 }