Refactor iface file generation:

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>

1 files changed, 20 insertions, 17 deletions

diff --git a/compiler/iface/LoadIface.hs b/compiler/iface/LoadIface.hs
index f501e0354b..446477d018 100644
--- a/compiler/iface/LoadIface.hs
+++ b/compiler/iface/LoadIface.hs
@@ -7,6 +7,7 @@ Loading interface files
 -}
 
 {-# LANGUAGE CPP, BangPatterns, RecordWildCards, NondecreasingIndentation #-}
+{-# LANGUAGE TypeFamilies #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 module LoadIface (
         -- Importing one thing
@@ -422,7 +423,7 @@ loadInterface doc_str mod from
                            Succeeded hi_boot_file -> computeInterface doc_str hi_boot_file mod
         ; case read_result of {
             Failed err -> do
-                { let fake_iface = emptyModIface mod
+                { let fake_iface = emptyFullModIface mod
 
                 ; updateEps_ $ \eps ->
                         eps { eps_PIT = extendModuleEnv (eps_PIT eps) (mi_module fake_iface) fake_iface }
@@ -965,7 +966,7 @@ findAndReadIface doc_str mod wanted_mod_with_insts hi_boot_file
                   r <- read_file dynFilePath
                   case r of
                       Succeeded (dynIface, _)
-                       | mi_mod_hash iface == mi_mod_hash dynIface ->
+                       | mi_mod_hash (mi_final_exts iface) == mi_mod_hash (mi_final_exts dynIface) ->
                           return ()
                        | otherwise ->
                           do traceIf (text "Dynamic hash doesn't match")
@@ -1039,13 +1040,15 @@ initExternalPackageState
 
 ghcPrimIface :: ModIface
 ghcPrimIface
-  = (emptyModIface gHC_PRIM) {
+  = empty_iface {
         mi_exports  = ghcPrimExports,
         mi_decls    = [],
         mi_fixities = fixities,
-        mi_fix_fn  = mkIfaceFixCache fixities
-    }
+        mi_final_exts = (mi_final_exts empty_iface){ mi_fix_fn = mkIfaceFixCache fixities }
+        }
   where
+    empty_iface = emptyFullModIface gHC_PRIM
+
     -- The fixities listed here for @`seq`@ or @->@ should match
     -- those in primops.txt.pp (from which Haddock docs are generated).
     fixities = (getOccName seqId, Fixity NoSourceText 0 InfixR)
@@ -1118,21 +1121,21 @@ pprModIfaceSimple iface = ppr (mi_module iface) $$ pprDeps (mi_deps iface) $$ ne
 
 pprModIface :: ModIface -> SDoc
 -- Show a ModIface
-pprModIface iface
+pprModIface iface@ModIface{ mi_final_exts = exts }
  = vcat [ text "interface"
                 <+> ppr (mi_module iface) <+> pp_hsc_src (mi_hsc_src iface)
-                <+> (if mi_orphan iface then text "[orphan module]" else Outputable.empty)
-                <+> (if mi_finsts iface then text "[family instance module]" else Outputable.empty)
-                <+> (if mi_hpc    iface then text "[hpc]" else Outputable.empty)
+                <+> (if mi_orphan exts then text "[orphan module]" else Outputable.empty)
+                <+> (if mi_finsts exts then text "[family instance module]" else Outputable.empty)
+                <+> (if mi_hpc iface then text "[hpc]" else Outputable.empty)
                 <+> integer hiVersion
-        , nest 2 (text "interface hash:" <+> ppr (mi_iface_hash iface))
-        , nest 2 (text "ABI hash:" <+> ppr (mi_mod_hash iface))
-        , nest 2 (text "export-list hash:" <+> ppr (mi_exp_hash iface))
-        , nest 2 (text "orphan hash:" <+> ppr (mi_orphan_hash iface))
-        , nest 2 (text "flag hash:" <+> ppr (mi_flag_hash iface))
-        , nest 2 (text "opt_hash:" <+> ppr (mi_opt_hash iface))
-        , nest 2 (text "hpc_hash:" <+> ppr (mi_hpc_hash iface))
-        , nest 2 (text "plugin_hash:" <+> ppr (mi_plugin_hash iface))
+        , nest 2 (text "interface hash:" <+> ppr (mi_iface_hash exts))
+        , nest 2 (text "ABI hash:" <+> ppr (mi_mod_hash exts))
+        , nest 2 (text "export-list hash:" <+> ppr (mi_exp_hash exts))
+        , nest 2 (text "orphan hash:" <+> ppr (mi_orphan_hash exts))
+        , nest 2 (text "flag hash:" <+> ppr (mi_flag_hash exts))
+        , nest 2 (text "opt_hash:" <+> ppr (mi_opt_hash exts))
+        , nest 2 (text "hpc_hash:" <+> ppr (mi_hpc_hash exts))
+        , nest 2 (text "plugin_hash:" <+> ppr (mi_plugin_hash exts))
         , nest 2 (text "sig of:" <+> ppr (mi_sig_of iface))
         , nest 2 (text "used TH splices:" <+> ppr (mi_used_th iface))
         , nest 2 (text "where")