diff options
Diffstat (limited to 'EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/GetPowerOfTwo.c')
| -rw-r--r-- | EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/GetPowerOfTwo.c | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/GetPowerOfTwo.c b/EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/GetPowerOfTwo.c new file mode 100644 index 0000000000..665fa02136 --- /dev/null +++ b/EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/GetPowerOfTwo.c @@ -0,0 +1,62 @@ +/*++
+
+Copyright (c) 2006, Intel Corporation
+All rights reserved. This program and the accompanying materials
+are licensed and made available under the terms and conditions of the BSD License
+which accompanies this distribution. The full text of the license may be found at
+http://opensource.org/licenses/bsd-license.php
+
+THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+Module Name:
+
+ GetPowerOfTwo.c
+
+Abstract:
+
+ Calculates the largest integer that is both
+ a power of two and less than Input
+
+--*/
+
+#include "Tiano.h"
+
+UINT64
+GetPowerOfTwo (
+ IN UINT64 Input
+ )
+/*++
+
+Routine Description:
+
+ Calculates the largest integer that is both
+ a power of two and less than Input
+
+Arguments:
+
+ Input - value to calculate power of two
+
+Returns:
+
+ the largest integer that is both a power of
+ two and less than Input
+
+--*/
+{
+ __asm {
+ xor eax, eax
+ mov edx, eax
+ mov ecx, dword ptr Input[4]
+ jecxz _F
+ bsr ecx, ecx
+ bts edx, ecx
+ jmp _Exit
+_F:
+ mov ecx, dword ptr Input[0]
+ jecxz _Exit
+ bsr ecx, ecx
+ bts eax, ecx
+_Exit:
+ }
+}
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