Do not CSE constant operands for GT_SIMD vector constructors

src/coreclr/jit/gentree.h

@@ -1733,6 +1733,7 @@ struct GenTree
     inline bool IsIntegralConst(ssize_t constVal) const;
     inline bool IsFloatPositiveZero() const;
     inline bool IsVectorZero() const;
+    inline bool IsVectorCreate() const;
     inline bool IsVectorAllBitsSet() const;
     inline bool IsVectorConst();
 
@@ -8313,6 +8314,52 @@ inline bool GenTree::IsVectorZero() const
     return IsCnsVec() && AsVecCon()->IsZero();
 }
 
+//-------------------------------------------------------------------
+// IsVectorCreate: returns true if this node is the creation of a vector.
+//                 Does not include "Unsafe" method calls.
+//
+// Returns:
+//     True if this node is the creation of a vector
+//
+inline bool GenTree::IsVectorCreate() const
+{
+#ifdef FEATURE_HW_INTRINSICS
+    if (OperIs(GT_HWINTRINSIC))
+    {
+        switch (AsHWIntrinsic()->GetHWIntrinsicId())
+        {
+            case NI_Vector128_Create:
+#if defined(TARGET_XARCH)
+            case NI_Vector256_Create:
+#elif defined(TARGET_ARMARCH)
+            case NI_Vector64_Create:
+#endif
+                return true;
+
+            default:
+                return false;
+        }
+    }
+#endif // FEATURE_HW_INTRINSICS
+
+#ifdef FEATURE_SIMD
+    if (OperIs(GT_SIMD))
+    {
+        switch (AsSIMD()->GetSIMDIntrinsicId())
+        {
+            case SIMDIntrinsicInit:
+            case SIMDIntrinsicInitN:
+                return true;
+
+            default:
+                return false;
+        }
+    }
+#endif // FEATURE_SIMD
+
+    return false;
+}
+
 //-------------------------------------------------------------------
 // IsVectorAllBitsSet: returns true if this node is a vector constant with all bits set.
 //

src/coreclr/jit/morph.cpp

@@ -13870,41 +13870,35 @@ GenTree* Compiler::fgMorphMultiOp(GenTreeMultiOp* multiOp)
             }
 #endif
 
-            case NI_Vector128_Create:
-#if defined(TARGET_XARCH)
-            case NI_Vector256_Create:
-#elif defined(TARGET_ARMARCH)
-            case NI_Vector64_Create:
-#endif
-            {
-                bool hwAllArgsAreConst = true;
-                for (GenTree** use : multiOp->UseEdges())
-                {
-                    if (!(*use)->OperIsConst())
-                    {
-                        hwAllArgsAreConst = false;
-                        break;
-                    }
-                }
-
-                // Avoid unexpected CSE for constant arguments for Vector_.Create
-                // but only if all arguments are constants.
-                if (hwAllArgsAreConst)
-                {
-                    for (GenTree** use : multiOp->UseEdges())
-                    {
-                        (*use)->SetDoNotCSE();
-                    }
-                }
-            }
-            break;
-
             default:
                 break;
         }
     }
 #endif // defined(FEATURE_HW_INTRINSICS) && defined(TARGET_XARCH)
 
+    if (opts.OptimizationEnabled() && multiOp->IsVectorCreate())
+    {
+        bool allArgsAreConst = true;
+        for (GenTree* arg : multiOp->Operands())
+        {
+            if (!arg->OperIsConst())
+            {
+                allArgsAreConst = false;
+                break;
+            }
+        }
+
+        // Avoid unexpected CSE for constant arguments for Vector_.Create
+        // but only if all arguments are constants.
+        if (allArgsAreConst)
+        {
+            for (GenTree* arg : multiOp->Operands())
+            {
+                arg->SetDoNotCSE();
+            }
+        }
+    }
+
 #ifdef FEATURE_HW_INTRINSICS
     if (multiOp->OperIsHWIntrinsic() && !optValnumCSE_phase)
     {