BigNumWordMul64.c

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#include "../BigNumLib.h"
 
#if defined (_MSC_VER) && !defined (__clang__)
  #include <intrin.h>
  #pragma intrinsic(_umul128)
#endif
 
OC_BN_WORD
BigNumWordMul64 (
  OUT OC_BN_WORD  *Hi,
  IN  OC_BN_WORD  A,
  IN  OC_BN_WORD  B
  )
{
  ASSERT (OC_BN_WORD_SIZE == sizeof (UINT64));
  ASSERT (Hi != NULL);
 
 #if !defined (_MSC_VER) || defined (__clang__)
  //
  // Clang and GCC support the __int128 type for edk2 builds.
  //
  unsigned __int128  Result = (unsigned __int128)A * B;
  *Hi = (OC_BN_WORD)(Result >> OC_BN_WORD_NUM_BITS);
  return (OC_BN_WORD)Result;
 #else
  //
  // MSVC does not support the __int128 type for edk2 builds, but a proprietary
  // intrinsic function declared above.
  //
  return _umul128 (A, B, Hi);
 #endif
}