message: Conditionally include immintrin.h for rcm
  See also the discussion under
diff: @@ -68,8 +68,11 @@ namespace omp {
  namespace rcm {
  -#if defined(__x86_64__) && (defined(__GNUG__) || defined(__clang__))
  -#define GKO_MM_PAUSE() asm("rep nop" :::);
  +#ifdef __x86_64__
  +#if defined(__GNUG__) || defined(__clang__)
  +#include <immintrin.h>
  +#endif
  +#define GKO_MM_PAUSE() _mm_pause()
  #else
  #define GKO_MM_PAUSE() // No equivalent instruction.
  #endif
  