df1651b5a4
git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@344 6ac86273-5f31-0410-b378-82cca8765d1b
110 lines
3.9 KiB
PHP
110 lines
3.9 KiB
PHP
; this one adapted from elks, http://elks.sourceforge.net
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; multiply cx:bx * dx:ax, result in dx:ax
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%macro LMULU 0
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push si
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push cx
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mov si, ax ; save _ax in si
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mov ax, bx ; cx:ax = _cx:_bx
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mul dx ; dx:ax = _bx*_dx (forget dx)
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xchg cx, ax ; cx = low(_dx*_bx)
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mul si ; dx:ax = _cx*_ax (forget dx)
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add cx, ax ; cx = low(_cx*_ax + _dx*_bx)
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mov ax, si ; restore _ax
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mul bx ; dx:ax = _bx*_ax
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add dx, cx ; dx = high(_bx*_ax)+low(_cx*_ax + _dx*_bx)
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pop cx
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pop si
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ret
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%endmacro
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; divide dx:ax / cx:bx, quotient in dx:ax, remainder in cx:bx
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%macro LDIVMODU 0
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; this one is adapted from an assembly gem:
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; gem writer: Norbert Juffa, norbert.juffa@amd.com
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; Dividing 64-bit unsigned integers Assembler / 80386
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; Here is a division routine for dividing two 64-bit unsigned integers.
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; I derived it by modifying some old
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; 16-bit code for dividing 32-bit integers that I did several years ago for a
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; Turbo-Pascal replacement library.
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; If a 64-bit signed integer division is needed, appropriate shell code for
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; this routine can easily be written.
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;
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; (adapted back to 32-bit by Bart Oldeman ;-))
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;
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; __U4D divides two unsigned long numbers, the dividend and the divisor
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; resulting in a quotient and a remainder.
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;
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; input:
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; dx:ax = dividend
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; cx:bx = divisor
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;
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; output:
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; dx:ax = quotient of division of dividend by divisor
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; cx:bx = remainder of division of dividend by divisor
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;
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; destroys:
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; flags
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;
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test cx, cx ; divisor > 2^32-1 ?
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jnz %%big_divisor ; yes, divisor > 32^32-1
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cmp dx, bx ; only one division needed ? (ecx = 0)
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jb %%one_div ; yes, one division sufficient
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xchg cx, ax ; save dividend-lo in cx, ax=0
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xchg ax, dx ; get dividend-hi in ax, dx=0
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div bx ; quotient-hi in eax
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xchg ax, cx ; cx = quotient-hi, ax =dividend-lo
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%%one_div:
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div bx ; ax = quotient-lo
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mov bx, dx ; bx = remainder-lo
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mov dx, cx ; dx = quotient-hi(quotient in dx:ax)
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xor cx, cx ; cx = remainder-hi (rem. in cx:bx)
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ret
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%%big_divisor:
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push si ; save temp
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push di ; variables
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push dx ; save
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push ax ; dividend
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mov si, bx ; divisor now in
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mov di, cx ; di:bx and cx:si
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%%shift_loop:
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shr dx, 1 ; shift both
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rcr ax, 1 ; divisor and
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shr di, 1 ; and dividend
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rcr bx, 1 ; right by 1 bit
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jnz %%shift_loop ; loop if di non-zero (rcr does not touch ZF)
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mov di, cx ; restore original divisor (di:si)
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div bx ; compute quotient
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pop bx ; get dividend lo-word
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mov cx, ax ; save quotient
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mul di ; quotient * divisor hi-word (low only)
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xchg ax, di ; save in di
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mov ax, cx ; ax=quotient
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mul si ; quotient * divisor lo-word
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add dx, di ; dx:ax = quotient * divisor
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sub bx, ax ; dividend-lo - (quot.*divisor)-lo
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mov ax, cx ; get quotient
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pop cx ; restore dividend hi-word
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sbb cx, dx ; subtract divisor * quot. from dividend
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sbb dx, dx ; 0 if remainder > 0, else FFFFFFFFh
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and si, dx ; nothing to add
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and di, dx ; back if remainder positive
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add bx, si ; correct remaider
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adc cx, di ; and quotient if
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add ax, dx ; necessary
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xor dx, dx ; clear hi-word of quot (ax<=FFFFFFFFh)
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pop di ; restore temp
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pop si ; variables
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ret
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%endmacro
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