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127 lines
2.8 KiB
127 lines
2.8 KiB
/*[
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shrd.c
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LOCAL CHAR SccsID[]="@(#)shrd.c 1.6 09/02/94";
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SHRD CPU functions.
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-------------------
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]*/
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#include <insignia.h>
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#include <host_def.h>
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#include <xt.h>
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#include <c_main.h>
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#include <c_addr.h>
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#include <c_bsic.h>
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#include <c_prot.h>
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#include <c_seg.h>
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#include <c_stack.h>
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#include <c_xcptn.h>
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#include <c_reg.h>
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#include <shrd.h>
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/*
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=====================================================================
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EXTERNAL FUNCTIONS START HERE.
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=====================================================================
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*/
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/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
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/* Generic - one size fits all 'shrd'. */
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/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
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GLOBAL VOID
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SHRD
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IFN4(
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IU32 *, pop1, /* pntr to dst/lsrc operand */
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IU32, op2, /* rsrc operand */
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IU32, op3, /* shift count operand */
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IUM8, op_sz /* 16 or 32-bit */
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)
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{
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IU32 result;
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IU32 msb;
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ISM32 new_of;
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/* only use lower five bits of count */
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if ( (op3 &= 0x1f) == 0 )
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return;
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/*
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NB. Intel doc. says that if op3 >= op_sz then the operation
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is undefined. In practice if op_sz is 32 then as op3 is taken
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modulo 32 it can never be in the undefined range and if op_sz
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is 16 the filler bits from op2 are 'recycled' for counts of 16
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and above.
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*/
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/*
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================= ================= ====
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| | | |op2| | | | --> | | | |op1| | | | --> |CF|
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================= ================= ====
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*/
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if ( op_sz == 16 )
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{
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*pop1 = op2 << 16 | *pop1; /* Double up filler bits */
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}
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/* Do all but last shift */
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op3 = op3 - 1; /* op3 now in range 0 - 30 */
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if ( op3 != 0 )
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{
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result = *pop1 >> op3 | op2 << 32-op3;
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op2 = op2 >> op3;
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}
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else
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{
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result = *pop1;
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}
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SET_CF((result & BIT0_MASK) != 0); /* last shift puts LSB in CF */
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/* save msb */
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msb = SZ2MSB(op_sz);
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msb = (result & msb) != 0;
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/* Now do final shift */
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result = result >> 1 | op2 << 31;
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result = result & SZ2MASK(op_sz);
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SET_PF(pf_table[result & 0xff]);
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SET_ZF(result == 0);
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SET_SF((result & SZ2MSB(op_sz)) != 0);
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/* set OF if sign changes */
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new_of = msb ^ GET_SF();
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if ( op3 == 0 ) /* NB Count has been decremented! */
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{
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SET_OF(new_of);
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}
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else
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{
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#ifdef SET_UNDEFINED_SHxD_FLAG
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/* Set OF to changed SF(original) and SF(result) */
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new_of = ((result ^ *pop1) & SZ2MSB(op_sz)) != 0;
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SET_OF(new_of);
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#else /* SET_UNDEFINED_SHxD_FLAG */
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do_multiple_shiftrot_of(new_of);
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#endif /* SET_UNDEFINED_SHxD_FLAG */
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}
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/* Set undefined flag(s) */
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#ifdef SET_UNDEFINED_FLAG
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SET_AF(UNDEFINED_FLAG);
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#endif
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*pop1 = result; /* Return answer */
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}
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