1 /** @file
2   Math worker functions.
3 
4   Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
5   This program and the accompanying materials
6   are licensed and made available under the terms and conditions of the BSD License
7   which accompanies this distribution.  The full text of the license may be found at
8   http://opensource.org/licenses/bsd-license.php.
9 
10   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
11   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
12 
13 **/
14 
15 
16 
17 
18 #include "BaseLibInternals.h"
19 
20 /**
21   Returns the bit position of the highest bit set in a 64-bit value. Equivalent
22   to log2(x).
23 
24   This function computes the bit position of the highest bit set in the 64-bit
25   value specified by Operand. If Operand is zero, then -1 is returned.
26   Otherwise, a value between 0 and 63 is returned.
27 
28   @param  Operand The 64-bit operand to evaluate.
29 
30   @retval 0..63   Position of the highest bit set in Operand if found.
31   @retval -1      Operand is zero.
32 
33 **/
34 INTN
35 EFIAPI
HighBitSet64(IN UINT64 Operand)36 HighBitSet64 (
37   IN      UINT64                    Operand
38   )
39 {
40   if (Operand == (UINT32)Operand) {
41     //
42     // Operand is just a 32-bit integer
43     //
44     return HighBitSet32 ((UINT32)Operand);
45   }
46 
47   //
48   // Operand is really a 64-bit integer
49   //
50   if (sizeof (UINTN) == sizeof (UINT32)) {
51     return HighBitSet32 (((UINT32*)&Operand)[1]) + 32;
52   } else {
53     return HighBitSet32 ((UINT32)RShiftU64 (Operand, 32)) + 32;
54   }
55 }
56