reactos/lib/rtl/i386/allmul_asm.s

   1 /*
   2  * COPYRIGHT:         See COPYING in the top level directory
   3  * PROJECT:           ReactOS kernel
   4  * PURPOSE:           Run-Time Library
   5  * FILE:              lib/rtl/i386/allmul.S
   6  * PROGRAMER:         Alex Ionescu (alex@relsoft.net)
   7  *                    Eric Kohl (ekohl@rz-online.de)
   8  *
   9  * Copyright (C) 2002 Michael Ringgaard.
  10  * All rights reserved.
  11  *
  12  * Redistribution and use in source and binary forms, with or without
  13  * modification, are permitted provided that the following conditions
  14  * are met:
  15  *
  16  * 1. Redistributions of source code must retain the above copyright
  17  *    notice, this list of conditions and the following disclaimer.
  18  * 2. Redistributions in binary form must reproduce the above copyright
  19  *    notice, this list of conditions and the following disclaimer in the
  20  *    documentation and/or other materials provided with the distribution.
  21  * 3. Neither the name of the project nor the names of its contributors
  22  *    may be used to endorse or promote products derived from this software
  23  *    without specific prior written permission.
  24
  25  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
  29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  31  * OR SERVICES// LOSS OF USE, DATA, OR PROFITS// OR BUSINESS INTERRUPTION)
  32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  35  * SUCH DAMAGE.
  36  */
  37
  38 .globl __allmul
  39
  40 .intel_syntax noprefix
  41
  42 /* FUNCTIONS ***************************************************************/
  43
  44 //
  45 // llmul - long multiply routine
  46 //
  47 // Purpose:
  48 //       Does a long multiply (same for signed/unsigned)
  49 //       Parameters are not changed.
  50 //
  51 // Entry:
  52 //       Parameters are passed on the stack:
  53 //               1st pushed: multiplier (QWORD)
  54 //               2nd pushed: multiplicand (QWORD)
  55 //
  56 // Exit:
  57 //       EDX:EAX - product of multiplier and multiplicand
  58 //       NOTE: parameters are removed from the stack
  59 //
  60 // Uses:
  61 //       ECX
  62 //
  63
  64 __allmul:
  65
  66 #define ALO  [esp + 4]       // stack address of a
  67 #define AHI  [esp + 8]       // stack address of a
  68 #define BLO  [esp + 12]      // stack address of b
  69 #define BHI  [esp + 16]      // stack address of b
  70
  71 //
  72 //       AHI, BHI : upper 32 bits of A and B
  73 //       ALO, BLO : lower 32 bits of A and B
  74 //
  75 //             ALO * BLO
  76 //       ALO * BHI
  77 // +     BLO * AHI
  78 // ---------------------
  79 //
  80
  81         mov     eax,AHI
  82         mov     ecx,BHI
  83         or      ecx,eax         //test for both hiwords zero.
  84         mov     ecx,BLO
  85         jnz     short hard      //both are zero, just mult ALO and BLO
  86
  87         mov     eax,AHI
  88         mul     ecx
  89
  90         ret     16              // callee restores the stack
  91
  92 hard:
  93         push    ebx
  94
  95 // must redefine A and B since esp has been altered
  96
  97 #define A2LO  [esp + 4]       // stack address of a
  98 #define A2HI  [esp + 8]       // stack address of a
  99 #define B2LO  [esp + 12]      // stack address of b
 100 #define B2HI  [esp + 16]      // stack address of b
 101
 102         mul     ecx             //eax has AHI, ecx has BLO, so AHI * BLO
 103         mov     ebx,eax         //save result
 104
 105         mov     eax,A2LO
 106         mul     dword ptr B2HI //ALO * BHI
 107         add     ebx,eax         //ebx = ((ALO * BHI) + (AHI * BLO))
 108
 109         mov     eax,A2LO  //ecx = BLO
 110         mul     ecx             //so edx:eax = ALO*BLO
 111         add     edx,ebx         //now edx has all the LO*HI stuff
 112
 113         pop     ebx
 114
 115         ret     16              // callee restores the stack
 116