Fire RULES in the Specialiser

The Specialiser has, for some time, fires class-op RULES in the
specialiser itself: see
   Note [Specialisation modulo dictionary selectors]

This MR beefs it up a bit, so that it fires /all/ RULES in the
specialiser, not just class-op rules.  See
   Note [Fire rules in the specialiser]
The result is a bit more specialisation; see test
   simplCore/should_compile/T21851_2

This pushed me into a bit of refactoring.  I made a new data types
GHC.Core.Rules.RuleEnv, which combines
  - the several source of rules (local, home-package, external)
  - the orphan-module dependencies

in a single record for `getRules` to consult.  That drove a bunch of
follow-on refactoring, including allowing me to remove
cr_visible_orphan_mods from the CoreReader data type.

I moved some of the RuleBase/RuleEnv stuff into GHC.Core.Rule.

The reorganisation in the Simplifier improve compile times a bit
(geom mean -0.1%), but T9961 is an outlier

Metric Decrease:
    T9961

1 files changed, 10 insertions, 11 deletions

diff --git a/compiler/GHC/Driver/Config/Core/Opt/Simplify.hs b/compiler/GHC/Driver/Config/Core/Opt/Simplify.hs
index 86284c8be9..75ae439df3 100644
--- a/compiler/GHC/Driver/Config/Core/Opt/Simplify.hs
+++ b/compiler/GHC/Driver/Config/Core/Opt/Simplify.hs
@@ -6,7 +6,7 @@ module GHC.Driver.Config.Core.Opt.Simplify
 
 import GHC.Prelude
 
-import GHC.Core ( RuleBase )
+import GHC.Core.Rules ( RuleBase )
 import GHC.Core.Opt.Pipeline.Types ( CoreToDo(..) )
 import GHC.Core.Opt.Simplify ( SimplifyExprOpts(..), SimplifyOpts(..) )
 import GHC.Core.Opt.Simplify.Env ( FloatEnable(..), SimplMode(..) )
@@ -40,20 +40,19 @@ initSimplifyExprOpts dflags ic = SimplifyExprOpts
   }
 
 initSimplifyOpts :: DynFlags -> [Var] -> Int -> SimplMode -> RuleBase -> SimplifyOpts
-initSimplifyOpts dflags extra_vars iterations mode rule_base = let
+initSimplifyOpts dflags extra_vars iterations mode hpt_rule_base = let
   -- This is a particularly ugly construction, but we will get rid of it in !8341.
   opts = SimplifyOpts
     { so_dump_core_sizes = not $ gopt Opt_SuppressCoreSizes dflags
-    , so_iterations = iterations
-    , so_mode = mode
+    , so_iterations      = iterations
+    , so_mode            = mode
     , so_pass_result_cfg = if gopt Opt_DoCoreLinting dflags
-      then Just $ initLintPassResultConfig dflags extra_vars (CoreDoSimplify opts)
-      else Nothing
-    , so_rule_base = rule_base
-    , so_top_env_cfg = TopEnvConfig
-        { te_history_size = historySize dflags
-        , te_tick_factor = simplTickFactor dflags
-        }
+                           then Just $ initLintPassResultConfig dflags extra_vars
+                                                            (CoreDoSimplify opts)
+                           else Nothing
+    , so_hpt_rules       = hpt_rule_base
+    , so_top_env_cfg     = TopEnvConfig { te_history_size = historySize dflags
+                                        , te_tick_factor = simplTickFactor dflags }
     }
   in opts