diff --git a/src/java.base/share/classes/java/lang/StringLatin1.java b/src/java.base/share/classes/java/lang/StringLatin1.java
index 875d79b6f64..3c6bd0dba84 100644
--- a/src/java.base/share/classes/java/lang/StringLatin1.java
+++ b/src/java.base/share/classes/java/lang/StringLatin1.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -398,9 +398,6 @@ final class StringLatin1 {
             if (u1 == u2) {
                 continue;
             }
-            if (Character.toLowerCase(u1) == Character.toLowerCase(u2)) {
-                continue;
-            }
             return false;
         }
         return true;
diff --git a/test/jdk/java/lang/String/CompactString/RegionMatches.java b/test/jdk/java/lang/String/CompactString/RegionMatches.java
index c44f8c5b1b8..e796708a5e7 100644
--- a/test/jdk/java/lang/String/CompactString/RegionMatches.java
+++ b/test/jdk/java/lang/String/CompactString/RegionMatches.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -24,6 +24,7 @@
 import org.testng.annotations.DataProvider;
 import org.testng.annotations.Test;
 
+import java.util.Map;
 import static org.testng.Assert.assertEquals;
 
 /*
@@ -92,13 +93,85 @@ public class RegionMatches extends CompactString {
                         "\uFF21", 0, 1, false },
                 new Object[] { STRING_SUPPLEMENTARY_LOWERCASE, false, 4,
                         "\uFF41", 0, 1, true },
+                // Turkish I with dot
+                new Object[] { "\u0130", false, 0, "i", 0, 1, false },
+                new Object[] { "\u0130", true,  0, "i", 0, 1, true },
+                // i without dot
+                new Object[] { "\u0131", false, 0, "i", 0, 1, false },
+                new Object[] { "\u0131", true,  0, "i", 0, 1, true },
+                // Exhaustive list of 1-char latin1 strings that match
+                // case-insensitively:
+                // for (char c1 = 0; c1 < 255; c1++) {
+                //   for (char c2 = c; c2 < 255; c2++) {
+                //     if (c1 == c2) continue;
+                //     if (String.valueOf(c1).regionMatches(true, 0, String.valueOf(c2), 0, 1)) {
+                //       System.out.println("                new Object[] { \"\\u00"
+                //                          + Integer.toHexString((int)c) + "\", true, 0, \"\\u00"
+                //                          + Integer.toHexString((int)c2) + "\", 0, 1, true },");
+                // }}}
+                new Object[] { "\u0041", true, 0, "\u0061", 0, 1, true },
+                new Object[] { "\u0042", true, 0, "\u0062", 0, 1, true },
+                new Object[] { "\u0043", true, 0, "\u0063", 0, 1, true },
+                new Object[] { "\u0044", true, 0, "\u0064", 0, 1, true },
+                new Object[] { "\u0045", true, 0, "\u0065", 0, 1, true },
+                new Object[] { "\u0046", true, 0, "\u0066", 0, 1, true },
+                new Object[] { "\u0047", true, 0, "\u0067", 0, 1, true },
+                new Object[] { "\u0048", true, 0, "\u0068", 0, 1, true },
+                new Object[] { "\u0049", true, 0, "\u0069", 0, 1, true },
+                new Object[] { "\u004a", true, 0, "\u006a", 0, 1, true },
+                new Object[] { "\u004b", true, 0, "\u006b", 0, 1, true },
+                new Object[] { "\u004c", true, 0, "\u006c", 0, 1, true },
+                new Object[] { "\u004d", true, 0, "\u006d", 0, 1, true },
+                new Object[] { "\u004e", true, 0, "\u006e", 0, 1, true },
+                new Object[] { "\u004f", true, 0, "\u006f", 0, 1, true },
+                new Object[] { "\u0050", true, 0, "\u0070", 0, 1, true },
+                new Object[] { "\u0051", true, 0, "\u0071", 0, 1, true },
+                new Object[] { "\u0052", true, 0, "\u0072", 0, 1, true },
+                new Object[] { "\u0053", true, 0, "\u0073", 0, 1, true },
+                new Object[] { "\u0054", true, 0, "\u0074", 0, 1, true },
+                new Object[] { "\u0055", true, 0, "\u0075", 0, 1, true },
+                new Object[] { "\u0056", true, 0, "\u0076", 0, 1, true },
+                new Object[] { "\u0057", true, 0, "\u0077", 0, 1, true },
+                new Object[] { "\u0058", true, 0, "\u0078", 0, 1, true },
+                new Object[] { "\u0059", true, 0, "\u0079", 0, 1, true },
+                new Object[] { "\u005a", true, 0, "\u007a", 0, 1, true },
+                new Object[] { "\u00c0", true, 0, "\u00e0", 0, 1, true },
+                new Object[] { "\u00c1", true, 0, "\u00e1", 0, 1, true },
+                new Object[] { "\u00c2", true, 0, "\u00e2", 0, 1, true },
+                new Object[] { "\u00c3", true, 0, "\u00e3", 0, 1, true },
+                new Object[] { "\u00c4", true, 0, "\u00e4", 0, 1, true },
+                new Object[] { "\u00c5", true, 0, "\u00e5", 0, 1, true },
+                new Object[] { "\u00c6", true, 0, "\u00e6", 0, 1, true },
+                new Object[] { "\u00c7", true, 0, "\u00e7", 0, 1, true },
+                new Object[] { "\u00c8", true, 0, "\u00e8", 0, 1, true },
+                new Object[] { "\u00c9", true, 0, "\u00e9", 0, 1, true },
+                new Object[] { "\u00ca", true, 0, "\u00ea", 0, 1, true },
+                new Object[] { "\u00cb", true, 0, "\u00eb", 0, 1, true },
+                new Object[] { "\u00cc", true, 0, "\u00ec", 0, 1, true },
+                new Object[] { "\u00cd", true, 0, "\u00ed", 0, 1, true },
+                new Object[] { "\u00ce", true, 0, "\u00ee", 0, 1, true },
+                new Object[] { "\u00cf", true, 0, "\u00ef", 0, 1, true },
+                new Object[] { "\u00d0", true, 0, "\u00f0", 0, 1, true },
+                new Object[] { "\u00d1", true, 0, "\u00f1", 0, 1, true },
+                new Object[] { "\u00d2", true, 0, "\u00f2", 0, 1, true },
+                new Object[] { "\u00d3", true, 0, "\u00f3", 0, 1, true },
+                new Object[] { "\u00d4", true, 0, "\u00f4", 0, 1, true },
+                new Object[] { "\u00d5", true, 0, "\u00f5", 0, 1, true },
+                new Object[] { "\u00d6", true, 0, "\u00f6", 0, 1, true },
+                new Object[] { "\u00d8", true, 0, "\u00f8", 0, 1, true },
+                new Object[] { "\u00d9", true, 0, "\u00f9", 0, 1, true },
+                new Object[] { "\u00da", true, 0, "\u00fa", 0, 1, true },
+                new Object[] { "\u00db", true, 0, "\u00fb", 0, 1, true },
+                new Object[] { "\u00dc", true, 0, "\u00fc", 0, 1, true },
+                new Object[] { "\u00dd", true, 0, "\u00fd", 0, 1, true },
+                new Object[] { "\u00de", true, 0, "\u00fe", 0, 1, true },
         };
     }
 
     @Test(dataProvider = "provider")
     public void testRegionMatches(String str, boolean ignoreCase, int toffset,
             String other, int ooffset, int len, boolean expected) {
-        map.get(str)
+        map.getOrDefault(str, Map.of(str, str)) // Allow data provider to test adhoc strings
                 .forEach(
                         (source, data) -> {
                             assertEquals(
diff --git a/test/micro/org/openjdk/bench/java/lang/StringOther.java b/test/micro/org/openjdk/bench/java/lang/StringOther.java
index 0cb4b86c63c..205881481d9 100644
--- a/test/micro/org/openjdk/bench/java/lang/StringOther.java
+++ b/test/micro/org/openjdk/bench/java/lang/StringOther.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -24,30 +24,39 @@ package org.openjdk.bench.java.lang;
 
 import org.openjdk.jmh.annotations.Benchmark;
 import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
 import org.openjdk.jmh.annotations.Mode;
 import org.openjdk.jmh.annotations.OutputTimeUnit;
 import org.openjdk.jmh.annotations.Scope;
 import org.openjdk.jmh.annotations.Setup;
 import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
 import org.openjdk.jmh.infra.Blackhole;
 
+import java.util.Locale;
 import java.util.Random;
 import java.util.concurrent.TimeUnit;
 
 @BenchmarkMode(Mode.AverageTime)
 @OutputTimeUnit(TimeUnit.NANOSECONDS)
 @State(Scope.Thread)
+@Warmup(iterations = 10, time = 1000, timeUnit = TimeUnit.MILLISECONDS)
+@Measurement(iterations = 5, time = 1000, timeUnit = TimeUnit.MILLISECONDS)
+@Fork(3)
 public class StringOther {
 
     private String testString;
     private Random rnd;
 
     private String str1, str2, str3, str4;
+    private String str1UP;
 
     @Setup
     public void setup() {
         testString = "Idealism is what precedes experience; cynicism is what follows.";
         str1 = "vm-guld vm-guld vm-guld";
+        str1UP = str1.toUpperCase(Locale.ROOT);
         str2 = "vm-guld vm-guld vm-guldx";
         str3 = "vm-guld vm-guld vm-guldx";
         str4 = "adadaskasdjierudks";
@@ -85,4 +94,10 @@ public class StringOther {
         return String.valueOf(rnd.nextInt()).intern();
     }
 
+    @Benchmark
+    public void regionMatchesLatin1(Blackhole bh) {
+        bh.consume(str1.regionMatches(true, 0, str2, 0, str1.length()));
+        bh.consume(str2.regionMatches(true, 16, str1UP, 0, 8));
+        bh.consume(str3.regionMatches(true, 6, str4, 1, 2));
+    }
 }