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