Optimized HighBitSetXX() functions

[mirror_edk2.git] / MdePkg / Library / BaseLib / HighBitSet32.c

/** @file\r
  Math worker functions.\r
\r
  Copyright (c) 2006, Intel Corporation<BR>\r
  All rights reserved. This program and the accompanying materials\r
  are licensed and made available under the terms and conditions of the BSD License\r
  which accompanies this distribution.  The full text of the license may be found at\r
  http://opensource.org/licenses/bsd-license.php\r
\r
  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
\r
**/\r
\r
#include "BaseLibInternals.h"\r
\r
/**\r
  Returns the bit position of the highest bit set in a 32-bit value. Equivalent\r
  to log2(x).\r
\r
  This function computes the bit position of the highest bit set in the 32-bit\r
  value specified by Operand. If Operand is zero, then -1 is returned.\r
  Otherwise, a value between 0 and 31 is returned.\r
\r
  @param  Operand The 32-bit operand to evaluate.\r
\r
  @return Position of the highest bit set in Operand if found.\r
  @retval -1  Operand is zero.\r
\r
**/\r
INTN\r
EFIAPI\r
HighBitSet32 (\r
  IN      UINT32                    Operand\r
  )\r
{\r
  INTN                              BitIndex;\r
\r
  if (Operand == 0) {\r
    return - 1;\r
  }\r
  for (BitIndex = 31; (INT32)Operand > 0; BitIndex--, Operand <<= 1);\r
  return BitIndex;\r
}\r