To use any of these intrinsics, include the immintrin.h file as follows:
Intrinsics that map to FXSAVE and FXRSTOR instructions
This group of intrinsics includes four intrinsics to save and restore the current state of the x87 FPU, MMX, XMM, and MXCSR registers.
These intrinsics accept a memory reference to a 16-byte aligned 512-byte memory chunk. The layout of the memory is shown below in Table 1.
Table 1 - FXSAVE save area layout.
Intrinsics that map to XSAVE, XSAVEOPT, and XRSTOR instructions
This group of intrinsics includes six intrinsics to fully or partially save and restore the current state of the x87 FPU, MMX, XMM, YMM, and MXCSR registers.
These intrinsics accept a memory reference to a 64-byte aligned memory. The layout of the register fields for the first 512 bytes is the same as the FXSAVE save area layout. The intrinsics saving the states do not write to bytes 464:511. The save area layout is shown in Tables 2a and 2b below.
The second operand is a save/restore mask specifying the saved/restored extended states. The value of the mask is ANDed with XFEATURE_ENABLED_MASK(XCR0). A particular extended state is saved/restored only if the corresponding bit of both save/restore mask and XFEATURE_ENABLED_MASK is set to '1'.
Table 2a - XSAVE save area layout (first 512 bytes)
Table 2b - XSAVE save area layout for YMM registers