JIT: Fix over-shifting logic when constant-folding AdvSimd.ShiftRight* and AdvSimd.ShiftLeft*

src/coreclr/jit/simd.h

@@ -668,10 +668,10 @@ void EvaluateUnarySimd(genTreeOps oper, bool scalar, var_types baseType, TSimd*
 template <typename TBase>
 TBase EvaluateBinaryScalarRSZ(TBase arg0, TBase arg1)
 {
-#if defined(TARGET_XARCH)
+#if defined(TARGET_XARCH) || defined(TARGET_ARM64)
     if ((arg1 < 0) || (arg1 >= (sizeof(TBase) * 8)))
     {
-        // For SIMD, xarch allows overshifting and treats
+        // For SIMD, xarch and ARM64 allow overshifting and treat
         // it as zeroing. So ensure we do the same here.
         //
         // The xplat APIs ensure the shiftAmount is masked
@@ -817,10 +817,10 @@ TBase EvaluateBinaryScalarSpecialized(genTreeOps oper, TBase arg0, TBase arg1)
 
         case GT_RSH:
         {
-#if defined(TARGET_XARCH)
+#if defined(TARGET_XARCH) || defined(TARGET_ARM64)
             if ((arg1 < 0) || (arg1 >= (sizeof(TBase) * 8)))
             {
-                // For SIMD, xarch allows overshifting and treats
+                // For SIMD, xarch and ARM64 allow overshifting and treat
                 // it as propagating the sign bit (returning Zero
                 // or AllBitsSet). So ensure we do the same here.
                 //

src/tests/JIT/Regression/JitBlue/Runtime_105817/Runtime_105817.cs

@@ -0,0 +1,60 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// Generated by Fuzzlyn v2.2 on 2024-08-01 14:37:47
+// Run on Arm64 MacOS
+// Seed: 14773448547728333023-vectort,vector64,vector128,armadvsimd,armadvsimdarm64,armaes,armarmbase,armarmbasearm64,armcrc32,armcrc32arm64,armdp,armrdm,armrdmarm64,armsha1,armsha256
+// Reduced from 270.2 KiB to 0.4 KiB in 00:01:48
+// Debug: Outputs 0
+// Release: Outputs 1
+using System;
+using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.Arm;
+using Xunit;
+
+public class Runtime_105817
+{
+    [Fact]
+    public static void TestOverShiftRightLogical()
+    {
+        if (AdvSimd.IsSupported)
+        {
+            var vr6 = Vector128.Create<short>(1);
+            var vr7 = AdvSimd.ShiftRightLogical(vr6, 16);
+            Assert.Equal(vr7, Vector128<short>.Zero);
+        }
+    }
+
+    [Fact]
+    public static void TestOverShiftRightLogicalScalar()
+    {
+        if (AdvSimd.IsSupported)
+        {
+            var vr6 = Vector64.Create<long>(1);
+            var vr7 = AdvSimd.ShiftRightLogicalScalar(vr6, 64);
+            Assert.Equal(vr7, Vector64<long>.Zero);
+        }
+    }
+
+    [Fact]
+    public static void TestOverShiftRightArithmetic()
+    {
+        if (AdvSimd.IsSupported)
+        {
+            var vr6 = Vector128.Create<short>(1);
+            var vr7 = AdvSimd.ShiftRightArithmetic(vr6, 16);
+            Assert.Equal(vr7, Vector128<short>.Zero);
+        }
+    }
+
+    [Fact]
+    public static void TestOverShiftRightArithmeticScalar()
+    {
+        if (AdvSimd.IsSupported)
+        {
+            var vr6 = Vector64.Create<long>(1);
+            var vr7 = AdvSimd.ShiftRightArithmeticScalar(vr6, 64);
+            Assert.Equal(vr7, Vector64<long>.Zero);
+        }
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_105817/Runtime_105817.csproj

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