Overhaul of infrastructure for profiling, coverage (HPC) and breakpoints

User visible changes
====================

Profilng
--------

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
future.

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
   tabs)

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In Core, the Note constructor has been replaced by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.

Tickets
=======

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)

3 files changed, 16 insertions, 8 deletions

diff --git a/compiler/stranal/DmdAnal.lhs b/compiler/stranal/DmdAnal.lhs
index 9955490c25..f52ab78180 100644
--- a/compiler/stranal/DmdAnal.lhs
+++ b/compiler/stranal/DmdAnal.lhs
@@ -166,8 +166,8 @@ dmdAnal env dmd (Cast e co)
 	-- inside recursive products -- we might not reach
 	-- a fixpoint.  So revert to a vanilla Eval demand
 
-dmdAnal env dmd (Note n e)
-  = (dmd_ty, Note n e')
+dmdAnal env dmd (Tick t e)
+  = (dmd_ty, Tick t e')
   where
     (dmd_ty, e') = dmdAnal env dmd e
 
diff --git a/compiler/stranal/WorkWrap.lhs b/compiler/stranal/WorkWrap.lhs
index c1e9c48390..c947388d18 100644
--- a/compiler/stranal/WorkWrap.lhs
+++ b/compiler/stranal/WorkWrap.lhs
@@ -110,8 +110,8 @@ wwExpr (Lam binder expr)
 wwExpr (App f a)
   = App <$> wwExpr f <*> wwExpr a
 
-wwExpr (Note note expr)
-  = Note note <$> wwExpr expr
+wwExpr (Tick note expr)
+  = Tick note <$> wwExpr expr
 
 wwExpr (Cast expr co) = do
     new_expr <- wwExpr expr
@@ -379,7 +379,7 @@ get_one_shots :: Expr Var -> [Bool]
 get_one_shots (Lam b e)
   | isId b    = isOneShotLambda b : get_one_shots e
   | otherwise = get_one_shots e
-get_one_shots (Note _ e) = get_one_shots e
+get_one_shots (Tick _ e) = get_one_shots e
 get_one_shots _    	 = noOneShotInfo
 \end{code}
 
diff --git a/compiler/stranal/WwLib.lhs b/compiler/stranal/WwLib.lhs
index 223cb81e8c..b18ded3118 100644
--- a/compiler/stranal/WwLib.lhs
+++ b/compiler/stranal/WwLib.lhs
@@ -475,10 +475,18 @@ mkWWcpr body_ty _other		-- No CPR info
 --	\ x -> case (_scc_ "foo" E) of I# x -> x)
 --
 -- This transform doesn't move work or allocation
--- from one cost centre to another
+-- from one cost centre to another.
+--
+-- Later [SDM]: presumably this is because we want the simplifier to
+-- eliminate the case, and the scc would get in the way?  I'm ok with
+-- including the case itself in the cost centre, since it is morally
+-- part of the function (post transformation) anyway.
+
 workerCase :: Id -> CoreExpr -> [Id] -> DataCon -> CoreExpr -> CoreExpr
-workerCase bndr (Note (SCC cc) e) args con body = Note (SCC cc) (mkUnpackCase bndr e args con body)
-workerCase bndr e args con body = mkUnpackCase bndr e args con body
+workerCase bndr (Tick tickish e) args con body
+   = Tick tickish (mkUnpackCase bndr e args con body)
+workerCase bndr e args con body
+   = mkUnpackCase bndr e args con body
 \end{code}