Ensure constant evaluation of shifts on xarch broadcast the operand t…

…o the correct size (#105487)

* Ensure constant evaluation of shifts on xarch broadcast the operand to the correct size

* Ensure we don't try to execute AVX2 code on unsupported platforms

src/coreclr/jit/gentree.cpp

@@ -30917,6 +30917,10 @@ GenTree* Compiler::gtFoldExprHWIntrinsic(GenTreeHWIntrinsic* tree)
                                 // Ensure we don't lose track the the amount is an overshift
                                 shiftAmount = -1;
                             }
+
+                            // Ensure we broadcast to the right vector size
+                            otherNode->gtType = retType;
+
                             otherNode->AsVecCon()->EvaluateBroadcastInPlace(simdBaseType, shiftAmount);
                         }
                     }

src/tests/JIT/Regression/JitBlue/Runtime_105465/Runtime_105465.cs

@@ -0,0 +1,26 @@
+// Generated by Fuzzlyn v1.7 on 2024-07-25 11:06:17
+// Run on X64 Windows
+// Seed: 1535747306914661768-vectort,vector128,vector256,x86aes,x86avx,x86avx2,x86bmi1,x86bmi1x64,x86bmi2,x86bmi2x64,x86fma,x86lzcnt,x86lzcntx64,x86pclmulqdq,x86popcnt,x86popcntx64,x86sse,x86ssex64,x86sse2,x86sse2x64,x86sse3,x86sse41,x86sse41x64,x86sse42,x86sse42x64,x86ssse3,x86x86base
+// Reduced from 95.3 KiB to 0.6 KiB in 00:00:29
+// Debug: Outputs <0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0>
+// Release: Outputs <0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1>
+using System;
+using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.X86;
+using Xunit;
+
+public class Runtime_105465
+{
+    [Fact]
+    public static void TestEntryPoint()
+    {
+        if (Avx2.IsSupported)
+        {
+            var vr2 = Vector256.Create<ushort>(1);
+            var vr3 = Vector128.Create<ushort>(1);
+            Vector256<ushort> vr4 = Avx2.ShiftLeftLogical(vr2, vr3);
+            Assert.Equal(Vector256<ushort>.Zero, vr4);
+        }
+    }
+}
+

src/tests/JIT/Regression/JitBlue/Runtime_105465/Runtime_105465.csproj

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