diff options
Diffstat (limited to 'EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/RShiftU64.c')
-rw-r--r-- | EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/RShiftU64.c | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/RShiftU64.c b/EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/RShiftU64.c new file mode 100644 index 0000000000..bc909eb78d --- /dev/null +++ b/EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/RShiftU64.c @@ -0,0 +1,71 @@ +/*++
+
+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:
+
+ RShiftU64.c
+
+Abstract:
+
+ 64-bit right shift function for IA-32
+
+--*/
+
+#include "Tiano.h"
+
+UINT64
+RShiftU64 (
+ IN UINT64 Operand,
+ IN UINTN Count
+ )
+/*++
+
+Routine Description:
+ This routine allows a 64 bit value to be right shifted by 32 bits and returns the
+ shifted value.
+ Count is valid up 63. (Only Bits 0-5 is valid for Count)
+Arguments:
+ Operand - Value to be shifted
+ Count - Number of times to shift right.
+
+Returns:
+
+ Value shifted right identified by the Count.
+
+--*/
+{
+ __asm {
+
+ mov eax, dword ptr Operand[0]
+ mov edx, dword ptr Operand[4]
+
+ ;
+ ; CL is valid from 0 - 31. shld will move EDX:EAX by CL times but EDX is not touched
+ ; For CL of 32 - 63, it will be shifted 0 - 31 so we will move edx to eax later.
+ ;
+ mov ecx, Count
+ and ecx, 63
+ shrd eax, edx, cl
+ shr edx, cl
+
+ cmp ecx, 32
+ jc short _RShiftU64_Done
+
+ ;
+ ; Since Count is 32 - 63, edx will have been shifted by 0 - 31
+ ; If shifted by 32 or more, set upper 32 bits to zero.
+ ;
+ mov eax, edx
+ xor edx, edx
+
+_RShiftU64_Done:
+ }
+}
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