# Intrinsics for Reading and Writing the Content of Extended Control Registers

This group of intrinsics includes two intrinsics to read from and write to extended control registers (XCRs). Currently, the only such register defined is XCR0, XFEATURE_ENABLED_MASK register. This register specifies the set of processor states that the operating system enables on that processor, for example x87 FPU states, SSE states, and other processor extended states that Intel® 64 architecture may introduce in the future.

To use these intrinsics, include the immintrin.h file as follows:

    #include <immintrin.h>

Parent topic: Intrinsics for Managing Extended Processor States and Registers

- _xgetbv()
  Reads the content of an extended control register.
- _xsetbv()
  Writes the given value to a specified extended control register.