From 388c83bb9570377d1fa3e1ac685f4d05e3813eb9 Mon Sep 17 00:00:00 2001
From: Stephen Toub <stoub@microsoft.com>
Date: Thu, 19 Jan 2023 20:02:22 -0500
Subject: [PATCH] Improve StringComparer.OrdinalIgnoreCase.Compare perf
 (#80813)

---
 .../src/System/StringComparer.cs              | 22 +++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/libraries/System.Private.CoreLib/src/System/StringComparer.cs b/src/libraries/System.Private.CoreLib/src/System/StringComparer.cs
index 93938b246adf6..8edcece63e8c0 100644
--- a/src/libraries/System.Private.CoreLib/src/System/StringComparer.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/StringComparer.cs
@@ -318,7 +318,7 @@ public override int Compare(string? x, string? y)
 
             if (_ignoreCase)
             {
-                return string.Compare(x, y, StringComparison.OrdinalIgnoreCase);
+                return System.Globalization.Ordinal.CompareStringIgnoreCase(ref x.GetRawStringData(), x.Length, ref y.GetRawStringData(), y.Length);
             }
 
             return string.CompareOrdinal(x, y);
@@ -418,7 +418,25 @@ private OrdinalIgnoreCaseComparer() : base(true)
         {
         }
 
-        public override int Compare(string? x, string? y) => string.Compare(x, y, StringComparison.OrdinalIgnoreCase);
+        public override int Compare(string? x, string? y)
+        {
+            if (ReferenceEquals(x, y))
+            {
+                return 0;
+            }
+
+            if (x == null)
+            {
+                return -1;
+            }
+
+            if (y == null)
+            {
+                return 1;
+            }
+
+            return System.Globalization.Ordinal.CompareStringIgnoreCase(ref x.GetRawStringData(), x.Length, ref y.GetRawStringData(), y.Length);
+        }
 
         public override bool Equals(string? x, string? y)
         {