[release/8.0] JIT: Extract all side effects of the index in optRemoveRangeCheck

src/coreclr/jit/optimizer.cpp

@@ -8875,9 +8875,15 @@ GenTree* Compiler::optRemoveRangeCheck(GenTreeBoundsChk* check, GenTree* comma,
     }
 #endif
 
-    // Extract side effects
+    // TODO-Bug: We really should be extracting all side effects from the
+    // length and index here, but the length typically involves a GT_ARR_LENGTH
+    // that we would preserve. Usually, as part of proving that the range check
+    // passes, we have also proven that the ARR_LENGTH is non-faulting. We need
+    // a good way to communicate to this function that it is ok to ignore side
+    // effects of the ARR_LENGTH.
     GenTree* sideEffList = nullptr;
-    gtExtractSideEffList(check, &sideEffList, GTF_ASG);
+    gtExtractSideEffList(check->GetArrayLength(), &sideEffList, GTF_ASG);
+    gtExtractSideEffList(check->GetIndex(), &sideEffList);
 
     if (sideEffList != nullptr)
     {

src/tests/JIT/Regression/JitBlue/Runtime_91576/Runtime_91576.cs

@@ -1,5 +1,5 @@
 // Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.aa
+// The .NET Foundation licenses this file to you under the MIT license.
 
 // Generated by Fuzzlyn v1.6 on 2023-09-03 15:59:01
 // Run on X64 Windows

src/tests/JIT/Regression/JitBlue/Runtime_91862/Runtime_91862.cs

@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+using Xunit;
+
+public class Runtime_91862
+{
+    [Fact]
+    public static int TestEntryPoint()
+    {
+        return Foo(default);
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static int Foo(Vector128<float> v)
+    {
+        int result = 101;
+        // This tree results in a BOUNDS_CHECK for Bar(...) & 3
+        float x = Vector128.GetElement(v, Bar(ref result) & 3);
+
+        if (result != 100)
+        {
+            Console.WriteLine("FAIL");
+        }
+
+        // After inlining x is DCE'd, which will extract side effects of its assignment above.
+        // That results IR amenable to forward sub, and we end up with a BOUNDS_CHECK
+        // with a complex index expression that we can still prove is within bounds.
+        Baz(x);
+        return result;
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static int Bar(ref int result)
+    {
+        result = 100;
+        return 0;
+    }
+
+    private static void Baz(float x)
+    {
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_91862/Runtime_91862.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>