/*-------------------------------------------------------------------------
-
_moduint.c :- routine for unsigned int (16 bit) modulus
Written By - Sandeep Dutta . sandeep.dutta@usa.net (1999)
under the terms of the GNU Library 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 Library General Public License for more details.
-
+
You should have received a copy of the GNU Library General Public License
along with this program; if not, write to the Free Software
Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
-
+
In other words, you are welcome to use, share and improve this program.
You are forbidden to forbid anyone else to use, share and improve
- what you give them. Help stamp out software-hoarding!
+ what you give them. Help stamp out software-hoarding!
-------------------------------------------------------------------------*/
+/* Assembler-functions are provided for:
+ mcs51 small
+ mcs51 small stack-auto
+*/
+
+#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 _MODUINT_ASM_SMALL_AUTO
+# else
+# define _MODUINT_ASM_SMALL
+# endif
+# endif
+# endif
+#endif
+
+#if defined _MODUINT_ASM_SMALL || defined _MODUINT_ASM_SMALL_AUTO
+
+static void
+_moduint_dummy (void) _naked
+{
+ _asm
+
+ .globl __moduint
+
+ __moduint:
+
+ #define count r2
+ #define al dpl
+ #define ah dph
+
+#if defined(SDCC_STACK_AUTO) && !defined(SDCC_PARMS_IN_BANK1)
+
+ ar0 = 0 ; BUG register set is not considered
+ ar1 = 1
+
+ .globl __modint
+
+ mov a,sp
+ add a,#-2 ; 2 bytes return address
+ mov r0,a ; r0 points to bh
+ mov ar1,@r0 ; load bh
+ dec r0
+ mov ar0,@r0 ; load bl
+
+ #define bl r0
+ #define bh r1
+
+ __modint: ; entry point for __modsint
+
+
+#else // SDCC_STACK_AUTO
+
+#if !defined(SDCC_PARMS_IN_BANK1)
+#if defined(SDCC_NOOVERLAY)
+ .area DSEG (DATA)
+#else
+ .area OSEG (OVR,DATA)
+#endif
+
+ .globl __moduint_PARM_2
+ .globl __modsint_PARM_2
+
+ __moduint_PARM_2:
+ __modsint_PARM_2:
+ .ds 2
+
+ .area CSEG (CODE)
+
+ #define bl (__moduint_PARM_2)
+ #define bh (__moduint_PARM_2 + 1)
+#else
+ #define bl (b1_0)
+ #define bh (b1_1)
+#endif
+#endif // SDCC_STACK_AUTO
+
+ mov a,bl ; avoid endless loop
+ orl a,bh
+ jz div_by_0
+
+ mov count,#1
+
+ loop1: mov a,bl ; b <<= 1
+ add a,acc
+ mov bl,a
+ mov a,bh
+ rlc a
+ jc msbset
+ mov bh,a
+
+ mov a,al ; a - b
+ subb a,bl ; here carry is always clear
+ mov a,ah
+ subb a,bh
+
+ jc start
+
+ inc count
+ sjmp loop1
+
+
+ start: clr c
+ mov a,bh ; b >>= 1;
+ msbset: rrc a
+ mov bh,a
+ mov a,bl
+ rrc a
+ mov bl,a
+
+
+ loop2: clr c
+ mov a,al ; a - b
+ subb a,bl
+
+ mov b,a
+ mov a,ah
+ subb a,bh
+
+ jc smaller ; a >= b?
+
+ mov ah,a ; -> yes; a = a - b;
+ mov al,b
+ smaller: ; -> no
+ clr c
+ mov a,bh ; b >>= 1;
+ rrc a
+ mov bh,a
+ mov a,bl
+ rrc a
+ mov bl,a
+
+ djnz count,loop2
+ div_by_0:
+ ret
+
+ _endasm ;
+}
+
+#else // defined _MODUINT_ASM_SMALL || defined _MODUINT_ASM_SMALL_AUTO
+
#define MSB_SET(x) ((x >> (8*sizeof(x)-1)) & 1)
-unsigned int _moduint (unsigned int a ,unsigned int b)
+unsigned int
+_moduint (unsigned int a, unsigned int b)
{
- unsigned char count = 0;
+ unsigned char count = 0;
- while (!MSB_SET(b)) {
- b <<= 1;
- if (b > a)
- {
- b >>=1;
- break;
- }
- count++;
- }
-
- do {
- if (b <= a) {
- a -= b;
- }
- b >>= 1;
- } while (count--);
-
- return a;
+ while (!MSB_SET(b))
+ {
+ b <<= 1;
+ if (b > a)
+ {
+ b >>=1;
+ break;
+ }
+ count++;
+ }
+ do
+ {
+ if (a >= b)
+ a -= b;
+ b >>= 1;
+ }
+ while (count--);
+ return a;
}
+
+#endif // defined _MODUINT_ASM_SMALL || defined _MODUINT_ASM_SMALL_AUTO
projects / fw / sdcc / blobdiff