1. Added comments to ASM files

[mirror_edk2.git] / MdePkg / Library / BaseLib / Ia32 / DivU64x64Remainder.asm

;------------------------------------------------------------------------------\r
;\r
; Copyright (c) 2006, Intel Corporation\r
; All rights reserved. This program and the accompanying materials\r
; are licensed and made available under the terms and conditions of the BSD License\r
; which accompanies this distribution.  The full text of the license may be found at\r
; http://opensource.org/licenses/bsd-license.php\r
;\r
; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
;\r
; Module Name:\r
;\r
;   DivU64x64Remainder.asm\r
;\r
; Abstract:\r
;\r
;   Calculate the quotient of a 64-bit integer by a 64-bit integer and returns\r
;   both the quotient and the remainder\r
;\r
;------------------------------------------------------------------------------\r
\r
    .386\r
    .model  flat,C\r
    .code\r
\r
EXTERN  InternalMathDivRemU64x32:PROC\r
\r
;------------------------------------------------------------------------------\r
; UINT64\r
; EFIAPI\r
; InternalMathDivRemU64x64 (\r
;   IN      UINT64                    Dividend,\r
;   IN      UINT64                    Divisor,\r
;   OUT     UINT64                    *Remainder    OPTIONAL\r
;   );\r
;------------------------------------------------------------------------------\r
InternalMathDivRemU64x64    PROC\r
    mov     ecx, [esp + 16]             ; ecx <- divisor[32..63]\r
    test    ecx, ecx\r
    jnz     _@DivRemU64x64              ; call _@DivRemU64x64 if Divisor > 2^32\r
    mov     ecx, [esp + 20]\r
    jecxz   @F\r
    and     dword ptr [ecx + 4], 0      ; zero high dword of remainder\r
    mov     [esp + 16], ecx             ; set up stack frame to match DivRemU64x32\r
@@:\r
    jmp     InternalMathDivRemU64x32\r
InternalMathDivRemU64x64    ENDP\r
\r
_@DivRemU64x64  PROC    USES    ebx esi edi\r
    mov     edx, dword ptr [esp + 20]\r
    mov     eax, dword ptr [esp + 16]   ; edx:eax <- dividend\r
    mov     edi, edx\r
    mov     esi, eax                    ; edi:esi <- dividend\r
    mov     ebx, dword ptr [esp + 24]   ; ecx:ebx <- divisor\r
@@:\r
    shr     edx, 1\r
    rcr     eax, 1\r
    shrd    ebx, ecx, 1\r
    shr     ecx, 1\r
    jnz     @B\r
    div     ebx\r
    mov     ebx, eax                    ; ebx <- quotient\r
    mov     ecx, [esp + 28]             ; ecx <- high dword of divisor\r
    mul     dword ptr [esp + 24]        ; edx:eax <- quotient * divisor[0..31]\r
    imul    ecx, ebx                    ; ecx <- quotient * divisor[32..63]\r
    add     edx, ecx                    ; edx <- (quotient * divisor)[32..63]\r
    mov     ecx, dword ptr [esp + 32]   ; ecx <- addr for Remainder\r
    jc      @TooLarge                   ; product > 2^64\r
    cmp     edi, edx                    ; compare high 32 bits\r
    ja      @Correct\r
    jb      @TooLarge                   ; product > dividend\r
    cmp     esi, eax\r
    jae     @Correct                    ; product <= dividend\r
@TooLarge:\r
    dec     ebx                         ; adjust quotient by -1\r
    jecxz   @Return                     ; return if Remainder == NULL\r
    sub     eax, dword ptr [esp + 24]\r
    sbb     edx, dword ptr [esp + 28]   ; edx:eax <- (quotient - 1) * divisor\r
@Correct:\r
    jecxz   @Return\r
    sub     esi, eax\r
    sbb     edi, edx                    ; edi:esi <- remainder\r
    mov     [ecx], esi\r
    mov     [ecx + 4], edi\r
@Return:\r
    mov     eax, ebx                    ; eax <- quotient\r
    xor     edx, edx                    ; quotient is 32 bits long\r
    ret\r
_@DivRemU64x64  ENDP\r
\r
    END\r