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TITLE DivU64x32.asm: 64-bit division 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:
;
; DivU64x32.asm
;
; Abstract:
;
; 64-bit division function for IA-32
;
;------------------------------------------------------------------------------
.686P
.XMM
.MODEL SMALL
.CODE
DivU64x32 PROTO C Dividend: QWORD, Divisor: DWORD, Remainder: DWORD
DivU64x32 PROC C Dividend: QWORD, Divisor: DWORD, Remainder: DWORD
;------------------------------------------------------------------------------
; UINT64
; DivU64x32 (
; IN UINT64 Dividend,
; IN UINTN Divisor,
; OUT UINTN *Remainder OPTIONAL
; )
;
; Routine Description:
;
; This routine allows a 64 bit value to be divided with a 32 bit value returns
; 64bit result and the Remainder.
;
; Arguments:
;
; Dividend - dividend
; Divisor - divisor
; Remainder - buffer for remainder
;
; Returns:
;
; Dividend / Divisor
; Remainder = Dividend mod Divisor
;
; N.B. only works for 31bit divisors!!
;------------------------------------------------------------------------------
push ecx
;
; let edx contain the intermediate result of remainder
;
xor edx, edx
mov ecx, 64
_DivU64x32_Wend:
shl dword ptr Dividend[0], 1
rcl dword ptr Dividend[4], 1
rcl edx, 1
;
; If intermediate result of remainder is larger than
; or equal to divisor, then set the lowest bit of dividend,
; and subtract divisor from intermediate remainder
;
cmp edx, Divisor
jb _DivU64x32_Cont
bts dword ptr Dividend[0], 0
sub edx, Divisor
_DivU64x32_Cont:
loop _DivU64x32_Wend
cmp Remainder, 0
je _DivU64x32_Done
mov eax, Remainder
mov dword ptr [eax], edx
_DivU64x32_Done:
mov eax, dword ptr Dividend[0]
mov edx, dword ptr Dividend[4]
pop ecx
ret
DivU64x32 ENDP
END
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