• Simon Marlow's avatar
    Overhaul of infrastructure for profiling, coverage (HPC) and breakpoints · 7bb0447d
    Simon Marlow authored
    User visible changes
    Flags renamed (the old ones are still accepted for now):
      OLD            NEW
      ---------      ------------
      -auto-all      -fprof-auto
      -auto          -fprof-exported
      -caf-all       -fprof-cafs
    New flags:
      -fprof-auto              Annotates all bindings (not just top-level
                               ones) with SCCs
      -fprof-top               Annotates just top-level bindings with SCCs
      -fprof-exported          Annotates just exported bindings with SCCs
      -fprof-no-count-entries  Do not maintain entry counts when profiling
                               (can make profiled code go faster; useful with
                               heap profiling where entry counts are not used)
    Cost-centre stacks have a new semantics, which should in most cases
    result in more useful and intuitive profiles.  If you find this not to
    be the case, please let me know.  This is the area where I have been
    experimenting most, and the current solution is probably not the
    final version, however it does address all the outstanding bugs and
    seems to be better than GHC 7.2.
    Stack traces
    +RTS -xc now gives more information.  If the exception originates from
    a CAF (as is common, because GHC tends to lift exceptions out to the
    top-level), then the RTS walks up the stack and reports the stack in
    the enclosing update frame(s).
    Result: +RTS -xc is much more useful now - but you still have to
    compile for profiling to get it.  I've played around a little with
    adding 'head []' to GHC itself, and +RTS -xc does pinpoint the problem
    quite accurately.
    I plan to add more facilities for stack tracing (e.g. in GHCi) in the
    Coverage (HPC)
     * derived instances are now coloured yellow if they weren't used
     * likewise record field names
     * entry counts are more accurate (hpc --fun-entry-count)
     * tab width is now correct (markup was previously off in source with
    Internal changes
    In Core, the Note constructor has been replaced by
            Tick (Tickish b) (Expr b)
    which is used to represent all the kinds of source annotation we
    support: profiling SCCs, HPC ticks, and GHCi breakpoints.
    Depending on the properties of the Tickish, different transformations
    apply to Tick.  See CoreUtils.mkTick for details.
    This commit closes the following tickets, test cases to follow:
      - Close #2552: not a bug, but the behaviour is now more intuitive
        (test is T2552)
      - Close #680 (test is T680)
      - Close #1531 (test is result001)
      - Close #949 (test is T949)
      - Close #2466: test case has bitrotted (doesn't compile against current
        version of vector-space package)