x64_XSAVE_FORMAT.h

typedef struct DECLSPEC_ALIGN(16) _XSAVE_FORMAT {
    WORD   ControlWord;
    WORD   StatusWord;
    BYTE  TagWord;
    BYTE  Reserved1;
    WORD   ErrorOpcode;
    DWORD ErrorOffset;
    WORD   ErrorSelector;
    WORD   Reserved2;
    DWORD DataOffset;
    WORD   DataSelector;
    WORD   Reserved3;
    DWORD MxCsr;
    DWORD MxCsr_Mask;
    M128A FloatRegisters[8];

#if defined(_WIN64)

    M128A XmmRegisters[16];
    BYTE  Reserved4[96];

#else

    M128A XmmRegisters[8];
    BYTE  Reserved4[192];

    //
    // The fields below are not part of XSAVE/XRSTOR format.
    // They are written by the OS which is relying on a fact that
    // neither (FX)SAVE nor (F)XSTOR used this area.
    //

    DWORD   StackControl[7];    // KERNEL_STACK_CONTROL structure actualy
    DWORD   Cr0NpxState;

#endif

} XSAVE_FORMAT, *PXSAVE_FORMAT;

x86_FLOATING_SAVE_AREA.h

typedef struct _FLOATING_SAVE_AREA {
    DWORD   ControlWord;
    DWORD   StatusWord;
    DWORD   TagWord;
    DWORD   ErrorOffset;
    DWORD   ErrorSelector;
    DWORD   DataOffset;
    DWORD   DataSelector;
    BYTE    RegisterArea[SIZE_OF_80387_REGISTERS];
    DWORD   Cr0NpxState;
} FLOATING_SAVE_AREA;