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/*-------------------------------------------------------------------------
_divuint.c - routine for unsigned int (16 bit) division
Copyright (C) 1999, Jean-Louis Vern <jlvern AT gmail.com>
This library is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this library; see the file COPYING. If not, write to the
Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
MA 02110-1301, USA.
As a special exception, if you link this library with other files,
some of which are compiled with SDCC, to produce an executable,
this library does not by itself cause the resulting executable to
be covered by the GNU General Public License. This exception does
not however invalidate any other reasons why the executable file
might be covered by the GNU General Public License.
-------------------------------------------------------------------------*/
/* Assembler-functions are provided for:
mcs51 small
mcs51 small stack-auto
*/
#include <stdbool.h>
#if !defined(__SDCC_USE_XSTACK) && !defined(_SDCC_NO_ASM_LIB_FUNCS)
# if defined(__SDCC_mcs51)
# if defined(__SDCC_MODEL_SMALL)
# if defined(__SDCC_STACK_AUTO)
# define _DIVUINT_ASM_SMALL_AUTO
# else
# define _DIVUINT_ASM_SMALL
# endif
# endif
# endif
#endif
#if defined _DIVUINT_ASM_SMALL || defined _DIVUINT_ASM_SMALL_AUTO
static void
_divuint_dummy (void) __naked
{
__asm
.globl __divuint
__divuint:
#define count r2
#define reste_l r3
#define reste_h r4
#define xl dpl
#define xh dph
#if defined(__SDCC_PARMS_IN_BANK1)
#define yl (b1_0)
#define yh (b1_1)
#else // __SDCC_PARMS_IN_BANK1
#if defined(__SDCC_STACK_AUTO)
.globl __divint
mov a,sp
add a,#-2 ; 2 bytes return address
mov r0,a ; r0 points to yh
mov a,@r0 ; load yh
mov r1,a
dec r0
mov a,@r0 ; load yl
mov r0,a
#define yl r0
#define yh r1
__divint: ; entry point for __divsint
#else // __SDCC_STACK_AUTO
#if defined(__SDCC_NOOVERLAY)
.area DSEG (DATA)
#else
.area OSEG (OVR,DATA)
#endif
.globl __divuint_PARM_2
.globl __divsint_PARM_2
__divuint_PARM_2:
__divsint_PARM_2:
.ds 2
.area CSEG (CODE)
#define yl (__divuint_PARM_2)
#define yh (__divuint_PARM_2 + 1)
#endif // __SDCC_STACK_AUTO
#endif // __SDCC_PARMS_IN_BANK1
mov count,#16
clr a
mov reste_l,a
mov reste_h,a
loop:
mov a,xl ; x <<= 1
add a,acc
mov xl,a
mov a,xh
rlc a
mov xh,a
mov a,reste_l ; reste <<= 1
rlc a ; feed in carry
mov reste_l,a
mov a,reste_h
rlc a
mov reste_h,a
mov a,reste_l ; reste - y
subb a,yl ; here carry is always clear, because
; reste <<= 1 never overflows
mov b,a
mov a,reste_h
subb a,yh
jc smaller ; reste >= y?
mov reste_h,a ; -> yes; reste = reste - y;
mov reste_l,b
orl xl,#1
smaller: ; -> no
djnz count,loop
ret
__endasm;
}
#else // defined _DIVUINT_ASM_SMALL || defined _DIVUINT_ASM_SMALL_AUTO
#define MSB_SET(x) ((x >> (8*sizeof(x)-1)) & 1)
unsigned int
_divuint (unsigned int x, unsigned int y)
{
unsigned int reste = 0;
unsigned char count = 16;
bool c;
do
{
// reste: x <- 0;
c = MSB_SET(x);
x <<= 1;
reste <<= 1;
if (c)
reste |= 1;
if (reste >= y)
{
reste -= y;
// x <- (result = 1)
x |= 1;
}
}
while (--count);
return x;
}
#endif // defined _DIVUINT_ASM_SMALL || defined _DIVUINT_ASM_SMALL_AUTO
|
