115 lines
2.1 KiB
NASM
115 lines
2.1 KiB
NASM
|
page ,132
|
||
|
|
title lmul - long multiply routine
|
||
|
|
;***
|
||
|
|
;lmul.asm - long multiply routine
|
||
|
|
;
|
||
|
|
; Copyright (c) Microsoft Corporation. All rights reserved.
|
||
|
|
;
|
||
|
|
;Purpose:
|
||
|
|
; Defines long multiply routines
|
||
|
|
; Both signed and unsigned routines are the same, since multiply's
|
||
|
|
; work out the same in 2's complement
|
||
|
|
; creates the following routines:
|
||
|
|
; __aFlmul, __aFulmul (large, medium model)
|
||
|
|
; __aNlmul, __aNulmul (small, compact model)
|
||
|
|
;
|
||
|
|
;*******************************************************************************
|
||
|
|
|
||
|
|
.xlist
|
||
|
|
include ulhelp.inc
|
||
|
|
.list
|
||
|
|
|
||
|
|
sBegin code
|
||
|
|
assumes cs,code
|
||
|
|
assumes ds,data
|
||
|
|
|
||
|
|
page
|
||
|
|
;***
|
||
|
|
;lmul - long multiply routine
|
||
|
|
;
|
||
|
|
;Purpose:
|
||
|
|
; Does a long multiply (same for signed/unsigned)
|
||
|
|
; Parameters are not changed.
|
||
|
|
;
|
||
|
|
;Entry:
|
||
|
|
; Parameters are passed on the stack:
|
||
|
|
; 1st pushed: multiplier (DWORD)
|
||
|
|
; 2nd pushed: multiplicand (DWORD)
|
||
|
|
;
|
||
|
|
;Exit:
|
||
|
|
; DX:AX - product of multiplier and multiplicand
|
||
|
|
; NOTE: parameters are removed from the stack
|
||
|
|
;
|
||
|
|
;Uses:
|
||
|
|
; CX
|
||
|
|
;
|
||
|
|
;Exceptions:
|
||
|
|
;
|
||
|
|
;*******************************************************************************
|
||
|
|
|
||
|
|
if sizeC
|
||
|
|
cProc _aFulmul,<PUBLIC>,<>
|
||
|
|
cBegin nogen
|
||
|
|
cEnd nogen
|
||
|
|
else
|
||
|
|
cProc _aNulmul,<PUBLIC>,<>
|
||
|
|
cBegin nogen
|
||
|
|
cEnd nogen
|
||
|
|
endif
|
||
|
|
|
||
|
|
|
||
|
|
if sizeC
|
||
|
|
cProc _aFlmul,<PUBLIC>,<>
|
||
|
|
else
|
||
|
|
cProc _aNlmul,<PUBLIC>,<>
|
||
|
|
endif
|
||
|
|
|
||
|
|
cBegin
|
||
|
|
A equ BPARGBAS[bp] ; stack address of a
|
||
|
|
B equ BPARGBAS+4[bp] ; stack address of b
|
||
|
|
|
||
|
|
;
|
||
|
|
; AHI, BHI : upper 16 bits of A and B
|
||
|
|
; ALO, BLO : lower 16 bits of A and B
|
||
|
|
;
|
||
|
|
; ALO * BLO
|
||
|
|
; ALO * BHI
|
||
|
|
; + BLO * AHI
|
||
|
|
; ---------------------
|
||
|
|
;
|
||
|
|
mov ax,HIWORD(A)
|
||
|
|
mov cx,HIWORD(B)
|
||
|
|
or cx,ax ;test for both hiwords zero.
|
||
|
|
mov cx,LOWORD(B)
|
||
|
|
jnz hard ;both are zero, just mult ALO and BLO
|
||
|
|
|
||
|
|
mov ax,LOWORD(A)
|
||
|
|
mul cx
|
||
|
|
|
||
|
|
pop bp
|
||
|
|
ret
|
||
|
|
return 8 ; callee restores the stack
|
||
|
|
|
||
|
|
hard:
|
||
|
|
push bx
|
||
|
|
|
||
|
|
mul cx ;ax has AHI, cx has BLO, so AHI * BLO
|
||
|
|
mov bx,ax ;save result
|
||
|
|
|
||
|
|
mov ax,LOWORD(A)
|
||
|
|
mul word ptr HIWORD(B) ;ALO * BHI
|
||
|
|
add bx,ax ;bx = ((ALO * BHI) + (AHI * BLO))
|
||
|
|
|
||
|
|
mov ax,LOWORD(A) ;cx = BLO
|
||
|
|
mul cx ;so dx:ax = ALO*BLO
|
||
|
|
add dx,bx ;now dx has all the LO*HI stuff
|
||
|
|
|
||
|
|
pop bx
|
||
|
|
|
||
|
|
cEnd nolocals
|
||
|
|
return 8 ; callee restores the stack
|
||
|
|
|
||
|
|
sEnd
|
||
|
|
|
||
|
|
end
|