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/*[
ror.c
LOCAL CHAR SccsID[]="@(#)ror.c 1.5 02/09/94";
ROR CPU functions.
------------------
]*/
#include <insignia.h>
#include <host_def.h>
#include <xt.h>
#include <c_main.h>
#include <c_addr.h>
#include <c_bsic.h>
#include <c_prot.h>
#include <c_seg.h>
#include <c_stack.h>
#include <c_xcptn.h>
#include <c_reg.h>
#include <ror.h>
/*
=====================================================================
EXTERNAL FUNCTIONS START HERE.
=====================================================================
*/
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
/* Generic - one size fits all 'ror'. */
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
GLOBAL VOID
ROR
IFN3(
IU32 *, pop1, /* pntr to dst/src operand */
IU32, op2, /* rotation count operand */
IUM8, op_sz /* 8, 16 or 32-bit */
)
{
IU32 result;
IU32 feedback; /* Bit posn to feed Bit 0 back to */
ISM32 i;
ISM32 new_of;
/* only use lower five bits of count */
if ( (op2 &= 0x1f) == 0 )
return;
/*
================= ====
-> | | | | | | | | | --- --> |CF|
| ================= | ====
------------------------
*/
feedback = SZ2MSB(op_sz);
for ( result = *pop1, i = 0; i < op2; i++ )
{
if ( result & BIT0_MASK )
{
result = result >> 1 | feedback;
SET_CF(1);
}
else
{
result >>= 1;
SET_CF(0);
}
}
/* OF = MSB of result ^ (MSB-1) of result */
new_of = ((result ^ result << 1) & feedback) != 0;
if ( op2 == 1 )
{
SET_OF(new_of);
}
else
{
do_multiple_shiftrot_of(new_of);
}
*pop1 = result; /* Return answer */
}
|
