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;------------------------------------------------------------------------------
;
; Copyright (c) 2006, Intel Corporation. All rights reserved.<BR>
; SPDX-License-Identifier: BSD-2-Clause-Patent
;
; Module Name:
;
; DivU64x64Remainder.nasm
;
; Abstract:
;
; Calculate the quotient of a 64-bit integer by a 64-bit integer and returns
; both the quotient and the remainder
;
;------------------------------------------------------------------------------
SECTION .text
extern ASM_PFX(InternalMathDivRemU64x32)
;------------------------------------------------------------------------------
; UINT64
; EFIAPI
; InternalMathDivRemU64x64 (
; IN UINT64 Dividend,
; IN UINT64 Divisor,
; OUT UINT64 *Remainder OPTIONAL
; );
;------------------------------------------------------------------------------
global ASM_PFX(InternalMathDivRemU64x64)
ASM_PFX(InternalMathDivRemU64x64):
mov ecx, [esp + 16] ; ecx <- divisor[32..63]
test ecx, ecx
jnz _@DivRemU64x64 ; call _@DivRemU64x64 if Divisor > 2^32
mov ecx, [esp + 20]
jecxz .0
and dword [ecx + 4], 0 ; zero high dword of remainder
mov [esp + 16], ecx ; set up stack frame to match DivRemU64x32
.0:
jmp ASM_PFX(InternalMathDivRemU64x32)
_@DivRemU64x64:
push ebx
push esi
push edi
mov edx, dword [esp + 20]
mov eax, dword [esp + 16] ; edx:eax <- dividend
mov edi, edx
mov esi, eax ; edi:esi <- dividend
mov ebx, dword [esp + 24] ; ecx:ebx <- divisor
.1:
shr edx, 1
rcr eax, 1
shrd ebx, ecx, 1
shr ecx, 1
jnz .1
div ebx
mov ebx, eax ; ebx <- quotient
mov ecx, [esp + 28] ; ecx <- high dword of divisor
mul dword [esp + 24] ; edx:eax <- quotient * divisor[0..31]
imul ecx, ebx ; ecx <- quotient * divisor[32..63]
add edx, ecx ; edx <- (quotient * divisor)[32..63]
mov ecx, dword [esp + 32] ; ecx <- addr for Remainder
jc @TooLarge ; product > 2^64
cmp edi, edx ; compare high 32 bits
ja @Correct
jb @TooLarge ; product > dividend
cmp esi, eax
jae @Correct ; product <= dividend
@TooLarge:
dec ebx ; adjust quotient by -1
jecxz @Return ; return if Remainder == NULL
sub eax, dword [esp + 24]
sbb edx, dword [esp + 28] ; edx:eax <- (quotient - 1) * divisor
@Correct:
jecxz @Return
sub esi, eax
sbb edi, edx ; edi:esi <- remainder
mov [ecx], esi
mov [ecx + 4], edi
@Return:
mov eax, ebx ; eax <- quotient
xor edx, edx ; quotient is 32 bits long
pop edi
pop esi
pop ebx
ret
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