From 34d619bf9324e1835a3e9471b40d00a7520ada8f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Henrik=20B=C3=B6ving?= <hargonix@gmail.com>
Date: Thu, 18 Dec 2025 15:24:50 +0100
Subject: [PATCH] perf: use lean::unordered_set for expr_eq_fn (#11731)

This PR makes the cache in expr_eq_fn use mimalloc for a small
performance win across the board.
---
 src/kernel/expr_eq_fn.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/kernel/expr_eq_fn.cpp b/src/kernel/expr_eq_fn.cpp
index a5cf5cdcfe..74dd69ed4b 100644
--- a/src/kernel/expr_eq_fn.cpp
+++ b/src/kernel/expr_eq_fn.cpp
@@ -11,6 +11,7 @@ Author: Leonardo de Moura
 #include "runtime/thread.h"
 #include "kernel/expr.h"
 #include "kernel/expr_sets.h"
+#include "util/alloc.h"
 
 namespace lean {
 /**
@@ -26,7 +27,7 @@ class expr_eq_fn {
             return hash((size_t)p.first >> 3, (size_t)p.second >> 3);
         }
     };
-    typedef std::unordered_set<std::pair<lean_object *, lean_object *>, key_hasher> cache;
+    typedef lean::unordered_set<std::pair<lean_object *, lean_object *>, key_hasher> cache;
     cache * m_cache = nullptr;
     size_t m_max_stack_depth = 0;
     size_t m_counter = 0;