Separate CPR analysis from the Demand analyserwip/sep-cpr

The reasons for that can be found in the wiki:
https://gitlab.haskell.org/ghc/ghc/wikis/nested-cpr/split-off-cpr

We now run CPR after demand analysis (except for after the final demand
analysis run just before code gen). CPR got its own dump flags
(`-ddump-cpr-anal`, `-ddump-cpr-signatures`), but not its own flag to
activate/deactivate. It will run with `-fstrictness`/`-fworker-wrapper`.

As explained on the wiki page, this step is necessary for a sane Nested
CPR analysis. And it has quite positive impact on compiler performance:

Metric Decrease:
    T9233
    T9675
    T9961
    T15263

1 files changed, 9 insertions, 0 deletions

diff --git a/compiler/GHC/Iface/Tidy.hs b/compiler/GHC/Iface/Tidy.hs
index 8da7700e0e..2b1a4b7108 100644
--- a/compiler/GHC/Iface/Tidy.hs
+++ b/compiler/GHC/Iface/Tidy.hs
@@ -40,6 +40,7 @@ import IdInfo
 import InstEnv
 import Type             ( tidyTopType )
 import Demand           ( appIsBottom, isTopSig, isBottomingSig )
+import Cpr              ( mkCprSig, botCpr )
 import BasicTypes
 import Name hiding (varName)
 import NameSet
@@ -1150,6 +1151,7 @@ tidyTopIdInfo dflags rhs_tidy_env name orig_rhs tidy_rhs idinfo show_unfold
                         --      c.f. CoreTidy.tidyLetBndr
         `setArityInfo`      arity
         `setStrictnessInfo` final_sig
+        `setCprInfo`        final_cpr
         `setUnfoldingInfo`  minimal_unfold_info  -- See note [Preserve evaluatedness]
                                                  -- in CoreTidy
 
@@ -1157,6 +1159,7 @@ tidyTopIdInfo dflags rhs_tidy_env name orig_rhs tidy_rhs idinfo show_unfold
   = vanillaIdInfo
         `setArityInfo`         arity
         `setStrictnessInfo`    final_sig
+        `setCprInfo`           final_cpr
         `setOccInfo`           robust_occ_info
         `setInlinePragInfo`    (inlinePragInfo idinfo)
         `setUnfoldingInfo`     unfold_info
@@ -1180,6 +1183,12 @@ tidyTopIdInfo dflags rhs_tidy_env name orig_rhs tidy_rhs idinfo show_unfold
               | Just (_, nsig) <- mb_bot_str = nsig
               | otherwise                    = sig
 
+    cpr = cprInfo idinfo
+    final_cpr | Just _ <- mb_bot_str
+              = mkCprSig arity botCpr
+              | otherwise
+              = cpr
+
     _bottom_hidden id_sig = case mb_bot_str of
                                   Nothing         -> False
                                   Just (arity, _) -> not (appIsBottom id_sig arity)