1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
|
TITLE RShiftU64.asm: 64-bit right 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:
;
; RShiftU64.asm
;
; Abstract:
;
; 64-bit right shift function for IA-32
;
;------------------------------------------------------------------------------
.686P
.XMM
.MODEL SMALL
.CODE
RShiftU64 PROTO C Operand: QWORD, Count: DWORD
RShiftU64 PROC C Operand: QWORD, Count: DWORD
;------------------------------------------------------------------------------
; 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.
;------------------------------------------------------------------------------
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 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:
pop ecx
ret
RShiftU64 ENDP
END
|
