A compilation error occurs when compiling with clan on macOS:

[     CXX] ARM/sim/power/mathexpr_powermodel.cc -> .o
In file included from build/ARM/sim/mathexpr.cc:40:
build/ARM/sim/mathexpr.hh:87:36: error: implicit instantiation of undefined template 'std::__1::array<MathExpr::OpSearch, 6>'
    std::array<OpSearch, uNeg + 1> ops;
                                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/__tuple:116:65: note: template is declared here
template <class _Tp, size_t _Size> struct _LIBCPP_TYPE_VIS_ONLY array;
                                                                ^
 [    SWIG] ARM/python/m5/internal/AbstractMemory_vector.i -> _wrap.cc, .py
 [    SWIG] ARM/python/m5/internal/AbstractNVM_vector.i -> _wrap.cc, .py


this is due to missing includes in mathexpr.hh