Refactor iface file generation:wip/osa1/backend_refactoring

This commit refactors interface file generation to allow information
from the later passed (NCG, STG) to be stored in interface files.

We achieve this by splitting interface file generation into two parts:
* Partial interfaces, built based on the result of the core pipeline
* A fully instantiated interface, which also contains the final
fingerprints and can optionally contain information produced by the backend.

This change is required by !1304 and !1530.

-dynamic-too handling is refactored too: previously when generating code
we'd branch on -dynamic-too *before* code generation, but now we do it
after.

(Original code written by @AndreasK in !1530)

Performance
~~~~~~~~~~~

Before this patch interface files where created and immediately flushed
to disk which made space leaks impossible.
With this change we instead use NFData to force all iface related data
structures to avoid space leaks.

In the process of refactoring it was discovered that the code in the
ToIface Module allocated a lot of thunks which were immediately forced
when writing/forcing the interface file. So we made this module more
strict to avoid creating many of those thunks.

Bottom line is that allocations go down by about ~0.1% compared to
master.
Residency is not meaningfully different after this patch.
Runtime was not benchmarked.

Co-Authored-By: Andreas Klebinger <klebinger.andreas@gmx.at>
Co-Authored-By: Ömer Sinan Ağacan <omer@well-typed.com>

3 files changed, 6 insertions, 6 deletions

diff --git a/compiler/rename/RnEnv.hs b/compiler/rename/RnEnv.hs
index d9dbbee891..c84e7bd328 100644
--- a/compiler/rename/RnEnv.hs
+++ b/compiler/rename/RnEnv.hs
@@ -1266,10 +1266,10 @@ warnIfDeprecated gre@(GRE { gre_name = name, gre_imp = iss })
 
 lookupImpDeprec :: ModIface -> GlobalRdrElt -> Maybe WarningTxt
 lookupImpDeprec iface gre
-  = mi_warn_fn iface (greOccName gre) `mplus`  -- Bleat if the thing,
+  = mi_warn_fn (mi_final_exts iface) (greOccName gre) `mplus`  -- Bleat if the thing,
     case gre_par gre of                      -- or its parent, is warn'd
-       ParentIs  p              -> mi_warn_fn iface (nameOccName p)
-       FldParent { par_is = p } -> mi_warn_fn iface (nameOccName p)
+       ParentIs  p              -> mi_warn_fn (mi_final_exts iface) (nameOccName p)
+       FldParent { par_is = p } -> mi_warn_fn (mi_final_exts iface) (nameOccName p)
        NoParent                 -> Nothing
 
 {-
diff --git a/compiler/rename/RnFixity.hs b/compiler/rename/RnFixity.hs
index 198a0441e5..68d1348871 100644
--- a/compiler/rename/RnFixity.hs
+++ b/compiler/rename/RnFixity.hs
@@ -157,7 +157,7 @@ lookupFixityRn_help' name occ
       -- loadInterfaceForName will find B.hi even if B is a hidden module,
       -- and that's what we want.
       = do { iface <- loadInterfaceForName doc name
-           ; let mb_fix = mi_fix_fn iface occ
+           ; let mb_fix = mi_fix_fn (mi_final_exts iface) occ
            ; let msg = case mb_fix of
                             Nothing ->
                                   text "looking up name" <+> ppr name
diff --git a/compiler/rename/RnNames.hs b/compiler/rename/RnNames.hs
index 738f4c6ab5..7b9a385e48 100644
--- a/compiler/rename/RnNames.hs
+++ b/compiler/rename/RnNames.hs
@@ -393,8 +393,8 @@ calculateAvails :: DynFlags
 calculateAvails dflags iface mod_safe' want_boot imported_by =
   let imp_mod    = mi_module iface
       imp_sem_mod= mi_semantic_module iface
-      orph_iface = mi_orphan iface
-      has_finsts = mi_finsts iface
+      orph_iface = mi_orphan (mi_final_exts iface)
+      has_finsts = mi_finsts (mi_final_exts iface)
       deps       = mi_deps iface
       trust      = getSafeMode $ mi_trust iface
       trust_pkg  = mi_trust_pkg iface