--- /dev/null
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Runtime.CompilerServices;
+
+// Some tests for removing bounds checks based
+// on byte and sbyte-based indices
+
+class GitHub_21915
+{
+ private static ReadOnlySpan<byte> A => new byte[256] {
+ 0, 0, 0, 7, 8, 9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 1,
+ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1,
+ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1,
+ 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ };
+
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ private static byte NeedsEscapingByte256(int value) => A[value];
+
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ private static byte NeedsEscapingByte255(int value) => A.Slice(0, 255)[value];
+
+ [MethodImpl(MethodImplOptions.NoInlining)]
+ private static byte ByteRemoveBoundsCheck(ReadOnlySpan<byte> data, int i)
+ {
+ return NeedsEscapingByte256(data[i]);
+ }
+
+ [MethodImpl(MethodImplOptions.NoInlining)]
+ private static byte ByteKeepBoundsCheck1(ReadOnlySpan<byte> data, int i)
+ {
+ return NeedsEscapingByte255(data[i]);
+ }
+
+ [MethodImpl(MethodImplOptions.NoInlining)]
+ private static byte ByteKeepBoundsCheck2(ReadOnlySpan<byte> data, int i)
+ {
+ return NeedsEscapingByte256(data[i] + 1);
+ }
+
+ [MethodImpl(MethodImplOptions.NoInlining)]
+ private static byte SByteRemoveBoundsCheck(ReadOnlySpan<sbyte> data, int i)
+ {
+ return NeedsEscapingByte256(data[i] + 128);
+ }
+
+ [MethodImpl(MethodImplOptions.NoInlining)]
+ private static byte SByteKeepBoundsCheck1(ReadOnlySpan<sbyte> data, int i)
+ {
+ return NeedsEscapingByte255(data[i] + 128);
+ }
+
+ [MethodImpl(MethodImplOptions.NoInlining)]
+ private static byte SByteKeepBoundsCheck2(ReadOnlySpan<sbyte> data, int i)
+ {
+ return NeedsEscapingByte256(data[i] + 127);
+ }
+
+ public static int Main()
+ {
+ ReadOnlySpan<byte> bytes = new byte[] { 2, 3 };
+
+ byte brbc = ByteRemoveBoundsCheck(bytes, 1);
+ byte bkbc1 = ByteKeepBoundsCheck1(bytes, 1);
+ byte bkbc2 = ByteKeepBoundsCheck2(bytes, 0);
+
+ Console.WriteLine($"byte cases: {brbc} {bkbc1} {bkbc2} (expected 7 7 7)");
+
+ ReadOnlySpan<sbyte> sbytes = new sbyte[] { -124, -125, -128 };
+
+ byte sbrbc = SByteRemoveBoundsCheck(sbytes, 1);
+ byte sbkbc1 = SByteKeepBoundsCheck1(sbytes, 1);
+ byte sbkbc2 = SByteKeepBoundsCheck2(sbytes, 0);
+
+ Console.WriteLine($"sbyte cases: {sbrbc} {sbkbc1} {sbkbc2} (expected 7 7 7)");
+
+ bool ok = (brbc == 7) && (bkbc1 == 7) && (bkbc2 == 7) && (sbrbc == 7) && (sbkbc1 == 7) && (sbkbc2 == 7);
+
+ try
+ {
+ // Check for buggy case in initial PR 21857
+ // -128 + 127 should index with -1 and throw.
+ SByteKeepBoundsCheck2(sbytes, 2);
+ Console.WriteLine($"error: did not throw as expected");
+ ok = false;
+ }
+ catch (IndexOutOfRangeException)
+ {
+ Console.WriteLine($"threw exception, as expected");
+ }
+
+ return ok ? 100 : -1;
+ }
+}