Faster PC Histogram

[mrutt92]

We have a PC histogram tool currently that parses a cycle-by-cycle trace file from simulation. The functionality is very helpful, but it comes at ~3x cost to simulation time and the trace file can grown to GBs in size for even relatively short simulations.

This PR provides a fast-functional PC histogram. The histogram is stored in memory while simulation is running and dumped to a file at the end of simulation. Some level of detail is lost such as the instruction opcode (instead we see either 'instr' or 'fp_instr'). However, the stall type information is retained.

The overhead from using the fast PC histogram was never more than 20% over fast non-profiling simulation and as much as 3x faster than enabling the trace.

Note that this is unsuitable for blood graph generation. You still need to use tracing for that.

[drichmond]

Very excited to see this merged in

[mrutt92]

@tommydcjung anything else? remove the macros and then good-to-go?

[tommydcjung]

@tommydcjung anything else? remove the macros and then good-to-go?

Can we remove the macros so we can look at the resulting code? we might find more issues then

[mrutt92]

@tommydcjung anything else? remove the macros and then good-to-go? Can we remove the macros so we can look at the resulting code? we might find more issues then

Are we done reviewing everything else?

[mrutt92]

i went ahead and removed the macros.

[mrutt92]

Ok good to go?

[mrutt92]

good-to-go?