From dc5586d030effd9755e0e8cddfca46ddd7ea45eb Mon Sep 17 00:00:00 2001
From: Yedidya Feldblum <yfeldblum@meta.com>
Date: Mon, 22 Jul 2024 12:39:32 -0700
Subject: [PATCH] let F14HashToken equality-comparison skip the tag element

Summary: It only needs to compare the hash element and can skip comparing the derived tag element. The derived tag element is indended as a precomputed word to accelerate lookup but only decelerates equality-comparison.

Reviewed By: DenisYaroshevskiy

Differential Revision: D60044472

fbshipit-source-id: 7b18667b993b817b1ce3c78667693f5f12fb48e5
---
 folly/container/detail/F14Table.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/folly/container/detail/F14Table.h b/folly/container/detail/F14Table.h
index ca5766fb201..138d986c097 100644
--- a/folly/container/detail/F14Table.h
+++ b/folly/container/detail/F14Table.h
@@ -214,11 +214,11 @@ class F14HashToken final {
 
   friend constexpr bool operator==(
       F14HashToken const& a, F14HashToken const& b) noexcept {
-    return a.hp_ == b.hp_;
+    return a.hp_.first == b.hp_.first; // processed hash but not tag
   }
   friend constexpr bool operator!=(
       F14HashToken const& a, F14HashToken const& b) noexcept {
-    return a.hp_ != b.hp_;
+    return !(a == b);
   }
 
  private: