Hello,
I'm working on the GNU simulator using cgen, which I have partway
working at this point, and I've come across an interesting problem
when comparing its results against or1ksim.
When dumping a trace of the executed instructions using or1ksim, some
instructions are not being disassembled properly in the trace, even
though they appear to be simulated correctly. This does not happen
for every instruction. A lot of them are disassembled just fine.
For example, I put a simple program through or1ksim, and the trace
dumps the following line:
S 00000180: a8200001 <invalid>
The instruction is an l.ori instruction, from crt0.S in libgloss:
/* Clear status register, set supervisor mode */
l.ori r1, r0, SPR_SR_SM
SPR_SR_SM is equal to 0x1, so the encoding of this instruction should be:
101010 00001 00000 0000 0000 0000 0001
which matches the opcode 0xa8200001 in the output from or1ksim and in
the binary.
So basically, it looks like or1ksim is unable to disassemble some
instructions for printing, but is able to simulate them just fine.
Has anyone else seen this, or am I missing something?
-Pete
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