diff options
Diffstat (limited to 'EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/Log2.c')
| -rw-r--r-- | EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/Log2.c | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/Log2.c b/EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/Log2.c new file mode 100644 index 0000000000..7e6db880e1 --- /dev/null +++ b/EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/Log2.c @@ -0,0 +1,74 @@ +/*++
+
+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:
+
+ Log2.c
+
+Abstract:
+
+ 64-bit integer logarithm function for IA-32
+
+--*/
+
+#include "Tiano.h"
+
+UINT8
+Log2 (
+ IN UINT64 Operand
+ )
+/*++
+
+Routine Description:
+
+ Calculates and floors logarithms based on 2
+
+Arguments:
+
+ Operand - value to calculate logarithm
+
+Returns:
+
+ The largest integer that is less than or equal
+ to the logarithm of Operand based on 2
+
+--*/
+{
+ __asm {
+ mov ecx, 64
+
+ cmp dword ptr Operand[0], 0
+ jne _Log2_Wend
+ cmp dword ptr Operand[4], 0
+ jne _Log2_Wend
+ mov cl, 0FFH
+ jmp _Log2_Done
+
+_Log2_Wend:
+ dec ecx
+ cmp ecx, 32
+ jae _Log2_Higher
+ bt dword ptr Operand[0], ecx
+ jmp _Log2_Bit
+
+_Log2_Higher:
+ mov eax, ecx
+ sub eax, 32
+ bt dword ptr Operand[4], eax
+
+_Log2_Bit:
+ jc _Log2_Done
+ jmp _Log2_Wend
+
+_Log2_Done:
+ mov al, cl
+ }
+}
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