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/*++
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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