Benchmarking an optimisation

To test your whizzy new optimisation with nofib, you will want to:

1. Build the inplace stage2 compiler with a flag that controls whether it runs or not
2. Run the nofib suite with that flag on and then off, and compare the two runs:

make -k >& log1
make -k EXTRA_HC_OPTS=-fenable-cool-optimisation >& log2
nofib-analyse log1 log2

The output of the nofib-analyse tool is quite readable. Be warned: missing values in the output typically mean that the benchmark crashed and may indicate a problem with your optimisation.

If the comparison identifies any particularly bad benchmark results, you can run them individually by changing into their directory and running something like:

EXTRA_HC_OPTS="-fenable-cool-optimisation -ddump-simpl" make

You can add whatever dumping flags you need to see the output and understand what is going wrong.