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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"
;
;---------------------------------------------------------------------------
.686
.model flat,C
.code
;---------------------------------------------------------------------------
;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.
;
;--*/
RShiftU64 PROC
mov eax, [esp + 4]; dword ptr Operand[0]
mov edx, [esp + 8]; 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, [esp + 0Ch] ; 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:
ret
RShiftU64 ENDP
END
|
