Ensure TYP_SIMD12 LclVar can be cloned in lowering

src/coreclr/jit/gentree.cpp

@@ -6507,9 +6507,16 @@ GenTree* Compiler::gtNewLclvNode(unsigned lnum, var_types type DEBUGARG(IL_OFFSE
         // should be able to remove this exception and handle the assignment mismatch in
         // Lowering.
         LclVarDsc* varDsc = lvaGetDesc(lnum);
+#if FEATURE_SIMD
+        // We can additionally have a SIMD12 that was widened to a SIMD16, generally as part of lowering
+        assert((type == varDsc->lvType) || ((type == TYP_SIMD16) && (varDsc->lvType == TYP_SIMD12)) ||
+               (lvaIsImplicitByRefLocal(lnum) && fgGlobalMorph && (varDsc->lvType == TYP_BYREF)) ||
+               ((varDsc->lvType == TYP_STRUCT) && (genTypeSize(type) == varDsc->lvExactSize)));
+#else
         assert((type == varDsc->lvType) ||
                (lvaIsImplicitByRefLocal(lnum) && fgGlobalMorph && (varDsc->lvType == TYP_BYREF)) ||
                ((varDsc->lvType == TYP_STRUCT) && (genTypeSize(type) == varDsc->lvExactSize)));
+#endif // FEATURE_SIMD
     }
     GenTree* node = new (this, GT_LCL_VAR) GenTreeLclVar(GT_LCL_VAR, type, lnum DEBUGARG(ILoffs));