Hello All,
I'm currently trying to modify O3CPU to have deeper pipeline stages.
The extra stages will be dummy stages that only affects the CPI.
What would be the easiest way to do so?
I tried inserting one dummy stage between fetch and decode stages.
Currently, I have added {dummy1.cc, dummy1.hh, dummy1_impl.hh} that are
made from decode* files.
I also had to modify, {cpu.hh, cpu_policy.hh, cpu.cc, decode.hh,
decode_impl.hh, comm.hh, O3CPU.py, fetch.hh, fetch_impl.hh} files to apply
changes in the pipeline.
I have the SPARC_SE compiled without branch predictions stuff (from decode
stage) removed from the dummy stage and I receive an error during
fetch_impl.hh checkSignalsAndUpdate.
void DefaultDummy1<Impl>::readStallSignals(ThreadID) [with Impl =
O3CPUImpl]: Assertion `stalls[tid].dummy1' failed
I tried removing the dummy1's stall check and now it gives me,
void DefaultDummy1<Impl>::readStallSignals(ThreadID) [with Impl =
O3CPUImpl]: Assertion `stalls[tid].rename' failed
Meaning that the decode stage stall check is passed. I decided to step back
and figure out what I need to really do instead of just trying out different
things.
1. Is this the easiest way to add dummy stages that doesn't do anything?
2. What are the things I need to have and shouldn't have in my dummy
stage?
I would think that branch prediction stuff can go but stall checking could
remain. I actually left the decode branch stuff in there because I was getting
errors compiling them on my initial effort to remove them.
-Glenn
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