Optimized HighBitSetXX() functions
[mirror_edk2.git] / MdePkg / Library / BaseLib / HighBitSet32.c
CommitLineData
878ddf1f 1/** @file\r
2 Math worker functions.\r
3\r
4 Copyright (c) 2006, Intel Corporation<BR>\r
5 All rights reserved. This program and the accompanying materials\r
6 are licensed and made available under the terms and conditions of the BSD License\r
7 which accompanies this distribution. The full text of the license may be found at\r
8 http://opensource.org/licenses/bsd-license.php\r
9\r
10 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
11 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
12\r
13**/\r
14\r
15#include "BaseLibInternals.h"\r
16\r
17/**\r
18 Returns the bit position of the highest bit set in a 32-bit value. Equivalent\r
19 to log2(x).\r
20\r
21 This function computes the bit position of the highest bit set in the 32-bit\r
22 value specified by Operand. If Operand is zero, then -1 is returned.\r
23 Otherwise, a value between 0 and 31 is returned.\r
24\r
25 @param Operand The 32-bit operand to evaluate.\r
26\r
27 @return Position of the highest bit set in Operand if found.\r
28 @retval -1 Operand is zero.\r
29\r
30**/\r
31INTN\r
32EFIAPI\r
33HighBitSet32 (\r
34 IN UINT32 Operand\r
35 )\r
36{\r
37 INTN BitIndex;\r
38\r
73c47db8 39 if (Operand == 0) {\r
40 return - 1;\r
41 }\r
42 for (BitIndex = 31; (INT32)Operand > 0; BitIndex--, Operand <<= 1);\r
878ddf1f 43 return BitIndex;\r
44}\r