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TITLE LShiftU64.asm: 64-bit left shift function for IA-32
;------------------------------------------------------------------------------
;
; Copyright (c) 2004, 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:
;
; LShiftU64.asm
;
; Abstract:
;
; 64-bit left shift function for IA-32
;
;------------------------------------------------------------------------------
.686P
.XMM
.MODEL SMALL
.CODE
LShiftU64 PROTO C Operand: QWORD, Count: DWORD
LShiftU64 PROC C Operand: QWORD, Count: DWORD
;------------------------------------------------------------------------------
; UINT64
; LShiftU64 (
; IN UINT64 Operand,
; IN UINTN Count
; )
;
; Routine Description:
;
; This routine allows a 64 bit value to be left 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 left.
;
; Returns:
;
; Value shifted left identified by the Count.
;------------------------------------------------------------------------------
push ecx
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 EAX is not touched
; For CL of 32 - 63, it will be shifted 0 - 31 so we will move eax to edx later.
;
mov ecx, Count
and ecx, 63
shld edx, eax, cl
shl eax, cl
;
; Since Count is 32 - 63, eax will have been shifted by 0 - 31
; If shifted by 32 or more, set lower 32 bits to zero.
;
cmp ecx, 32
jc short _LShiftU64_Done
mov edx, eax
xor eax, eax
_LShiftU64_Done:
pop ecx
ret
LShiftU64 ENDP
END
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