[release/9.0] Fix IndexOf Optimization Code (#108562)

* Fix IndexOf Optimization Code

* small typo

* Address the feedback

* Exclude hybrid globalization runs on the new added tests

---------

Co-authored-by: Tarek Mahmoud Sayed <[email protected]>

Author: github-actions[bot]

src/libraries/System.Private.CoreLib/src/System/Globalization/CompareInfo.Icu.cs

@@ -130,12 +130,14 @@ private unsafe int IndexOfOrdinalIgnoreCaseHelper(ReadOnlySpan<char> source, Rea
                 }
 
                 int startIndex, endIndex, jump;
+                ReadOnlySpan<char> remainingSource;
                 if (fromBeginning)
                 {
                     // Left to right, from zero to last possible index in the source string.
                     // Incrementing by one after each iteration. Stop condition is last possible index plus 1.
                     startIndex = 0;
                     endIndex = source.Length - target.Length + 1;
+                    remainingSource = source.Slice(endIndex);
                     jump = 1;
                 }
                 else
@@ -144,6 +146,7 @@ private unsafe int IndexOfOrdinalIgnoreCaseHelper(ReadOnlySpan<char> source, Rea
                     // Decrementing by one after each iteration. Stop condition is last possible index minus 1.
                     startIndex = source.Length - target.Length;
                     endIndex = -1;
+                    remainingSource = source.Slice(0, startIndex);
                     jump = -1;
                 }
 
@@ -192,6 +195,12 @@ private unsafe int IndexOfOrdinalIgnoreCaseHelper(ReadOnlySpan<char> source, Rea
                 Next: ;
                 }
 
+                // Before we return -1, check if the remaining source contains any special or non-Ascii characters.
+                if (remainingSource.ContainsAnyExcept(s_nonSpecialAsciiChars))
+                {
+                    goto InteropCall;
+                }
+
                 return -1;
 
             InteropCall:
@@ -246,12 +255,14 @@ private unsafe int IndexOfOrdinalHelper(ReadOnlySpan<char> source, ReadOnlySpan<
                 }
 
                 int startIndex, endIndex, jump;
+                ReadOnlySpan<char> remainingSource;
                 if (fromBeginning)
                 {
                     // Left to right, from zero to last possible index in the source string.
                     // Incrementing by one after each iteration. Stop condition is last possible index plus 1.
                     startIndex = 0;
                     endIndex = source.Length - target.Length + 1;
+                    remainingSource = source.Slice(endIndex);
                     jump = 1;
                 }
                 else
@@ -260,6 +271,7 @@ private unsafe int IndexOfOrdinalHelper(ReadOnlySpan<char> source, ReadOnlySpan<
                     // Decrementing by one after each iteration. Stop condition is last possible index minus 1.
                     startIndex = source.Length - target.Length;
                     endIndex = -1;
+                    remainingSource = source.Slice(0, startIndex);
                     jump = -1;
                 }
 
@@ -297,6 +309,12 @@ private unsafe int IndexOfOrdinalHelper(ReadOnlySpan<char> source, ReadOnlySpan<
                 Next: ;
                 }
 
+                // Before we return -1, check if the remaining source contains any special or non-Ascii characters.
+                if (remainingSource.ContainsAnyExcept(s_nonSpecialAsciiChars))
+                {
+                    goto InteropCall;
+                }
+
                 return -1;
 
             InteropCall:

src/libraries/System.Runtime/tests/System.Globalization.Tests/CompareInfo/CompareInfoTests.IndexOf.cs

@@ -127,6 +127,16 @@ public static IEnumerable<object[]> IndexOf_TestData()
             yield return new object[] { s_currentCompare, "\u0130", "\u0131", 0, 1, CompareOptions.Ordinal, -1, 0 };
             yield return new object[] { s_currentCompare, "\u0131", "\u0130", 0, 1, CompareOptions.Ordinal, -1, 0 };
 
+            if (!PlatformDetection.IsHybridGlobalizationOnBrowser)
+            {
+                yield return new object[] { s_invariantCompare, "est", "est", 0, 2, CompareOptions.IgnoreCase, 0, 2 };
+                yield return new object[] { s_invariantCompare, " est", "est", 0, 3, CompareOptions.IgnoreCase, 1, 2 };
+                yield return new object[] { s_invariantCompare, " st", "st", 0, 2, CompareOptions.IgnoreCase, 1, 1 };
+                yield return new object[] { s_invariantCompare, "est", "est", 0, 3, CompareOptions.IgnoreCase, 0, 3 };
+                yield return new object[] { s_invariantCompare, " est", "est", 0, 4, CompareOptions.IgnoreCase, 1, 3 };
+                yield return new object[] { s_invariantCompare, " st", "st", 0, 3, CompareOptions.IgnoreCase, 1, 2 };
+            }
+
             // Platform differences
             if (PlatformDetection.IsNlsGlobalization)
             {