[llvm-dev] opt's -analyze feature and NPM

[Arthur Eubanks via llvm-dev]

opt has a flag -analyze which prints some debug information for analyses
that are run. This is done via Pass::print() within the pass manager.

This isn't implemented in NPM and since NPM is not so much into
subclassing, it's a bit awkward (but somewhat doable) to implement.
Probably a better alternative is to separate out the debug printing into a
flag, or into another pass. For example, some tests in Analysis/RegionInfo
run `opt -regions -analyze` for LPM, and `opt -passes='print<regions>'` to
test under NPM.

This is responsible for a significant amount of the remaining check-llvm
failures under NPM <https://bugs.llvm.org/show_bug.cgi?id=46651>. I'd like
to deprecate -analyze and migrate passes to either use a separate flag or
pass to print extra info. Any comments?

One tricky part about this is the existence of
update_analyze_test_checks.py. It uses some of the logs printed (per
function) by the -analyze infra to help with updating CHECK lines. This is
only used in ScalarEvolution and CostModel tests. If we decide to separate
out the -analyze printing for those passes into a separate flag/pass, we
could make those two passes mimic -analyze's logging to continue being able
to use update_analyze_test_checks.py if that's really wanted.
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