Change `-fprof-late` to insert cost centres after unfolding creation.wip/andreask/late_cc

The former behaviour of adding cost centres after optimization but
before unfoldings are created is not available via the flag
`prof-late-inline` instead.

I also reduced the overhead of -fprof-late* by pushing the cost centres
into lambdas. This means the cost centres will only account for
execution of functions and not their partial application.

Further I made LATE_CC cost centres it's own CC flavour so they now
won't clash with user defined ones if a user uses the same string for
a custom scc.

LateCC: Don't put cost centres inside constructor workers.

With -fprof-late they are rarely useful as the worker is usually
inlined. Even if the worker is not inlined or we use -fprof-late-linline
they are generally not helpful but bloat compile and run time
significantly. So we just don't add sccs inside constructor workers.

-------------------------
Metric Decrease:
    T13701
-------------------------

1 files changed, 2 insertions, 2 deletions

diff --git a/compiler/GHC/Iface/Tidy.hs b/compiler/GHC/Iface/Tidy.hs
index 1edd3cb9bf..7fec591196 100644
--- a/compiler/GHC/Iface/Tidy.hs
+++ b/compiler/GHC/Iface/Tidy.hs
@@ -347,7 +347,7 @@ data UnfoldingExposure
 
 data TidyOpts = TidyOpts
   { opt_name_cache        :: !NameCache
-  , opt_collect_ccs       :: !Bool
+  , opt_collect_ccs       :: !Bool -- ^ Always true if we compile with -prof
   , opt_unfolding_opts    :: !UnfoldingOpts
   , opt_expose_unfoldings :: !UnfoldingExposure
       -- ^ Which unfoldings to expose
@@ -468,7 +468,7 @@ tidyProgram opts (ModGuts { mg_module           = mod
 -- unfoldings.
 collectCostCentres :: Module -> CoreProgram -> [CoreRule] -> S.Set CostCentre
 collectCostCentres mod_name binds rules
-  = foldl' go_bind (go_rules S.empty) binds
+  = {-# SCC collectCostCentres #-} foldl' go_bind (go_rules S.empty) binds
   where
     go cs e = case e of
       Var{} -> cs