RSIM Bug Report #15
| Version of RSIM | 1.0 |
| Bug number | 15 |
| Bug class | 4 |
| Date | 3/2/99 |
| Reported by | internal |
| Affects | Write ancillary state register instructions |
| Files | predecode_instr.cc , funcs.cc , except.cc |
Problem Description
The implementation of the write ancillary state register instruction
did not match the description given in the SPARC architecture reference.
In particular, only one source register was accepted, whereas the
reference requires the XOR of two source registers. (In practice, this
does not seem to have affected any applications under the distribution
version of RSIM, since this instruction [called arithS2 in RSIM] was
only used for deprecated multiply and divide forms, and even then seems
to have not used the 2nd source register for any non-zero value.)
Suggested work-around
This requires the following changes:
In predecode_instr.cc, replace the existing function
arith_spec2 with the following:
<![CDATA[
int arith_spec2(instr *in, unsigned undec)
{
/* NOTE: arith_spec1 can either be write of some state register or
a software-initiated reset.
Here is the register mapping:
rd register type
0 Y register (for old mul/div ops)
1 reserved
2 Condition Codes Reg (xcc/icc)
3 ASI reg
4,5 Ancillary state registers (reserved)
6 FP registers status register
7-14 Ancillary state regs (reserved)
15 Software initiated reset
16-31 imp-dep
*/
in->rd = STATE_REGISTERS + Extract(undec,29,25); /* this is all for write state register */
in->rs1 = Extract(undec,18,14);
if (in->rd == STATE_CCR)
{
in->rd = COND_ICC; /* they're the same thing... */
}
if ((in->aux1 = Extract(undec,13,13)))
{
in->imm = SE(Extract(undec,12,0),13);
}
else
{
in->rs2 = Extract(undec,4,0);
}
/* we will implement the other specialties later.... */
return 1;
}
]]>
In funcs.cc, in the function fnarithSPECIAL2, replace
the expression <![CDATA[inst->rdvali=inst->rs1vali;]]> with:
<![CDATA[
if (inst->code->aux1)
{
inst->rdvali=inst->rs1vali ^ inst->code->imm;
}
else
{
inst->rdvali=inst->rs1vali ^ inst->rs2vali;
}
]]>
In except.cc, in the function
ProcessSerializedInstruction, make the same change as in
funcs.cc for the code in case iarithSPECIAL2 .
<![CDATA[
]]>