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/*[
shld.c
LOCAL CHAR SccsID[]="@(#)shld.c 1.6 09/02/94";
SHLD 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 <shld.h>
/*
=====================================================================
EXTERNAL FUNCTIONS START HERE.
=====================================================================
*/
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
/* Generic - one size fits all 'shld'. */
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
GLOBAL VOID
SHLD
IFN4(
IU32 *, pop1, /* pntr to dst/lsrc operand */
IU32, op2, /* rsrc operand */
IU32, op3, /* shift count operand */
IUM8, op_sz /* 16 or 32-bit */
)
{
IU32 result;
IU32 msb;
ISM32 new_of;
/* only use lower five bits of count, ie modulo 32 */
if ( (op3 &= 0x1f) == 0 )
return;
/*
NB. Intel doc. says that if op3 >= op_sz then the operation
is undefined. In practice if op_sz is 32 then as op3 is taken
modulo 32 it can never be in the undefined range and if op_sz
is 16 the filler bits from op2 are 'recycled' for counts of 16
and above.
*/
/*
==== ================= =================
|CF| <-- | | | |op1| | | | <-- | | | |op2| | | |
==== ================= =================
*/
if ( op_sz == 16 )
{
op2 = op2 << 16 | op2; /* Double up filler bits */
}
/* Do all but last shift */
op3 = op3 - 1; /* op3 now in range 0 - 30 */
if ( op3 != 0 )
{
result = *pop1 << op3 | op2 >> 32-op3;
op2 = op2 << op3;
}
else
{
result = *pop1;
}
/* Last shift will put MSB into carry */
msb = SZ2MSB(op_sz);
SET_CF((result & msb) != 0);
/* Now do final shift */
result = result << 1 | op2 >> 31;
result = result & SZ2MASK(op_sz);
SET_PF(pf_table[result & 0xff]);
SET_ZF(result == 0);
SET_SF((result & msb) != 0);
/* OF set if sign changes */
new_of = GET_CF() ^ GET_SF();
if ( op3 == 0 ) /* NB Count has been decremented! */
{
SET_OF(new_of);
}
else
{
#ifdef SET_UNDEFINED_SHxD_FLAG
/* Set OF to changed SF(original) and SF(result) */
new_of = ((result ^ *pop1) & SZ2MSB(op_sz)) != 0;
SET_OF(new_of);
#else /* SET_UNDEFINED_SHxD_FLAG */
do_multiple_shiftrot_of(new_of);
#endif /* SET_UNDEFINED_SHxD_FLAG */
}
/* Set undefined flag(s) */
#ifdef SET_UNDEFINED_FLAG
SET_AF(UNDEFINED_FLAG);
#endif
*pop1 = result; /* Return answer */
}
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