Ensure that Arm64 correctly handles multiplication of simd by a 64-bit scalar (#106839)

Author: tannergooding

src/coreclr/jit/gentree.cpp

@@ -20843,21 +20843,14 @@ GenTree* Compiler::gtNewSimdBinOpNode(
         {
             GenTree** broadcastOp = nullptr;
 
-#if defined(TARGET_ARM64)
-            if (varTypeIsLong(simdBaseType))
-            {
-                break;
-            }
-#endif // TARGET_ARM64
-
             if (varTypeIsArithmetic(op1))
             {
                 broadcastOp = &op1;
 
 #if defined(TARGET_ARM64)
                 if (!varTypeIsByte(simdBaseType))
                 {
-                    // MultiplyByScalar requires the scalar op to be op2fGetHWIntrinsicIdForBinOp
+                    // MultiplyByScalar requires the scalar op to be op2 for GetHWIntrinsicIdForBinOp
                     needsReverseOps = true;
                 }
 #endif // TARGET_ARM64
@@ -20870,7 +20863,12 @@ GenTree* Compiler::gtNewSimdBinOpNode(
             if (broadcastOp != nullptr)
             {
 #if defined(TARGET_ARM64)
-                if (!varTypeIsByte(simdBaseType))
+                if (varTypeIsLong(simdBaseType))
+                {
+                    // This is handled via emulation and the scalar is consumed directly
+                    break;
+                }
+                else if (!varTypeIsByte(simdBaseType))
                 {
                     op2ForLookup = *broadcastOp;
                     *broadcastOp = gtNewSimdCreateScalarUnsafeNode(TYP_SIMD8, *broadcastOp, simdBaseJitType, 8);
@@ -21274,24 +21272,26 @@ GenTree* Compiler::gtNewSimdBinOpNode(
 #elif defined(TARGET_ARM64)
             if (varTypeIsLong(simdBaseType))
             {
-                GenTree** op1ToDup = &op1;
-                GenTree** op2ToDup = &op2;
+                GenTree** op2ToDup = nullptr;
 
-                if (!varTypeIsArithmetic(op1))
-                {
-                    op1      = gtNewSimdToScalarNode(TYP_LONG, op1, simdBaseJitType, simdSize);
-                    op1ToDup = &op1->AsHWIntrinsic()->Op(1);
-                }
+                assert(varTypeIsSIMD(op1));
+                op1                = gtNewSimdToScalarNode(TYP_LONG, op1, simdBaseJitType, simdSize);
+                GenTree** op1ToDup = &op1->AsHWIntrinsic()->Op(1);
 
-                if (!varTypeIsArithmetic(op2))
+                if (varTypeIsSIMD(op2))
                 {
                     op2      = gtNewSimdToScalarNode(TYP_LONG, op2, simdBaseJitType, simdSize);
                     op2ToDup = &op2->AsHWIntrinsic()->Op(1);
                 }
 
                 // lower = op1.GetElement(0) * op2.GetElement(0)
                 GenTree* lower = gtNewOperNode(GT_MUL, TYP_LONG, op1, op2);
-                lower          = gtNewSimdCreateScalarUnsafeNode(type, lower, simdBaseJitType, simdSize);
+
+                if (op2ToDup == nullptr)
+                {
+                    op2ToDup = &lower->AsOp()->gtOp2;
+                }
+                lower = gtNewSimdCreateScalarUnsafeNode(type, lower, simdBaseJitType, simdSize);
 
                 if (simdSize == 8)
                 {
@@ -21303,10 +21303,8 @@ GenTree* Compiler::gtNewSimdBinOpNode(
                 GenTree* op1Dup = fgMakeMultiUse(op1ToDup);
                 GenTree* op2Dup = fgMakeMultiUse(op2ToDup);
 
-                if (!varTypeIsArithmetic(op1Dup))
-                {
-                    op1Dup = gtNewSimdGetElementNode(TYP_LONG, op1Dup, gtNewIconNode(1), simdBaseJitType, simdSize);
-                }
+                assert(!varTypeIsArithmetic(op1Dup));
+                op1Dup = gtNewSimdGetElementNode(TYP_LONG, op1Dup, gtNewIconNode(1), simdBaseJitType, simdSize);
 
                 if (!varTypeIsArithmetic(op2Dup))
                 {

src/tests/JIT/Regression/JitBlue/Runtime_106838/Runtime_106838.cs

@@ -0,0 +1,20 @@
+// 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_106838
+{
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static Vector128<ulong> Problem(Vector128<ulong> vector) => vector * 5UL;
+
+    [Fact]
+    public static void TestEntryPoint()
+    {
+        Vector128<ulong> result = Problem(Vector128.Create<ulong>(5));
+        Assert.Equal(Vector128.Create<ulong>(25), result);
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_106838/Runtime_106838.csproj

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