Catch (more) mismatched args in fgMorphArgs

src/coreclr/jit/morph.cpp

@@ -3399,13 +3399,28 @@ GenTreeCall* Compiler::fgMorphArgs(GenTreeCall* call)
                                 makeOutArgCopy = true;
                             }
                         }
-                        else if (genTypeSize(varDsc->TypeGet()) != genTypeSize(structBaseType))
+                        else if (genTypeSize(varDsc) != genTypeSize(structBaseType))
                         {
                             // Not a promoted struct, so just swizzle the type by using GT_LCL_FLD
                             lvaSetVarDoNotEnregister(lclNum DEBUGARG(DoNotEnregisterReason::SwizzleArg));
                             argObj->ChangeOper(GT_LCL_FLD);
                             argObj->gtType = structBaseType;
                         }
+                        else if (varTypeUsesFloatReg(varDsc) != varTypeUsesFloatReg(structBaseType))
+                        {
+                            // Here we can see int <-> float, long <-> double, long <-> simd8 mismatches, due
+                            // to the "OBJ(ADDR(LCL))" => "LCL" folding above. The latter case is handled in
+                            // lowering, others we will handle here via swizzling.
+                            CLANG_FORMAT_COMMENT_ANCHOR;
+#ifdef TARGET_AMD64
+                            if (varDsc->TypeGet() != TYP_SIMD8)
+#endif // TARGET_AMD64
+                            {
+                                lvaSetVarDoNotEnregister(lclNum DEBUGARG(DoNotEnregisterReason::SwizzleArg));
+                                argObj->ChangeOper(GT_LCL_FLD);
+                                argObj->gtType = structBaseType;
+                            }
+                        }
                     }
                     else if (argObj->OperIs(GT_LCL_FLD, GT_IND))
                     {

src/tests/JIT/Directed/StructABI/TypeMismatchedArgs.cs

@@ -41,6 +41,11 @@ public static int Main()
             return 105;
         }
 
+        if (ProblemWithRegFileMismatch_Win_x64(12, 13))
+        {
+            return 106;
+        }
+
         return 100;
     }
 
@@ -86,6 +91,21 @@ private static bool ProblemWithVectorCallArg()
         return result != s_vtor128.Vtor4.X;
     }
 
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static bool ProblemWithRegFileMismatch_Win_x64(double dbl, float flt)
+    {
+        if (CallForDblStruct(*(DblStruct*)&dbl) != dbl)
+        {
+            return true;
+        }
+        if (CallForFltStruct(*(FltStruct*)&flt) != flt)
+        {
+            return true;
+        }
+
+        return false;
+    }
+
     [MethodImpl(MethodImplOptions.NoInlining)]
     private static float CallForVector4(Vector4 value) => value.X;
 
@@ -97,6 +117,12 @@ private static bool ProblemWithVectorCallArg()
 
     [MethodImpl(MethodImplOptions.NoInlining)]
     private static long CallForSplitStructWithFourLongs(int arg0, int arg1, StructWithFourLongs splitArg) => splitArg.LongOne;
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static double CallForDblStruct(DblStruct value) => value.Dbl;
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static float CallForFltStruct(FltStruct value) => value.Flt;
 }
 
 [StructLayout(LayoutKind.Explicit)]
@@ -170,3 +196,13 @@ struct FourDoublesHfaStruct
     public double ThirdDblValue;
     public double FourthDblValue;
 }
+
+struct DblStruct
+{
+    public double Dbl;
+}
+
+struct FltStruct
+{
+    public float Flt;
+}