Store ModIface exports in an arraywip/D4170

Summary:
To lessen cascading changes, the old field name mi_exports (returning a list) is
exported as an accessor function and the field is replaced with mi_exports_arr.

There are many more lists that would likely benefit from the same treatment,
but one thing at a time.

Test Plan: Check gipedia

Reviewers: bgamari

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D4170

7 files changed, 46 insertions, 15 deletions

diff --git a/compiler/backpack/RnModIface.hs b/compiler/backpack/RnModIface.hs
index 2199965d13..2b9cdc1b01 100644
--- a/compiler/backpack/RnModIface.hs
+++ b/compiler/backpack/RnModIface.hs
@@ -101,7 +101,7 @@ rnModIface hsc_env insts nsubst iface = do
         sig_of <- case mi_sig_of iface of
                     Nothing -> return Nothing
                     Just x  -> fmap Just (rnModule x)
-        exports <- mapM rnAvailInfo (mi_exports iface)
+        exports <- mapM rnAvailInfo (mi_exports_arr iface)
         decls <- mapM rnIfaceDecl' (mi_decls iface)
         insts <- mapM rnIfaceClsInst (mi_insts iface)
         fams <- mapM rnIfaceFamInst (mi_fam_insts iface)
@@ -113,7 +113,7 @@ rnModIface hsc_env insts nsubst iface = do
                      , mi_sig_of = sig_of
                      , mi_insts = insts
                      , mi_fam_insts = fams
-                     , mi_exports = exports
+                     , mi_exports_arr = exports
                      , mi_decls = decls
                      , mi_deps = deps }
 
diff --git a/compiler/iface/LoadIface.hs b/compiler/iface/LoadIface.hs
index b91d984b9a..54a051dc17 100644
--- a/compiler/iface/LoadIface.hs
+++ b/compiler/iface/LoadIface.hs
@@ -947,7 +947,7 @@ initExternalPackageState
 ghcPrimIface :: ModIface
 ghcPrimIface
   = (emptyModIface gHC_PRIM) {
-        mi_exports  = ghcPrimExports,
+        mi_exports_arr = ghcPrimExports,
         mi_decls    = [],
         mi_fixities = fixities,
         mi_fix_fn  = mkIfaceFixCache fixities
diff --git a/compiler/iface/MkIface.hs b/compiler/iface/MkIface.hs
index a12cff2226..72b5e1f2a5 100644
--- a/compiler/iface/MkIface.hs
+++ b/compiler/iface/MkIface.hs
@@ -115,6 +115,7 @@ import Data.List
 import qualified Data.Map as Map
 import Data.Ord
 import Data.IORef
+import Data.Array
 import System.Directory
 import System.FilePath
 
@@ -260,7 +261,9 @@ mkIface_ hsc_env maybe_old_fingerprint
               mi_hsc_src     = hsc_src,
               mi_deps        = deps,
               mi_usages      = usages,
-              mi_exports     = mkIfaceExports exports,
+              mi_exports_arr = let
+                exports_list = mkIfaceExports exports
+                in listArray (0, length exports_list - 1) exports_list,
 
               -- Sort these lexicographically, so that
               -- the result is stable across compilations
diff --git a/compiler/main/HscTypes.hs b/compiler/main/HscTypes.hs
index b7baa57dff..9b2cd42505 100644
--- a/compiler/main/HscTypes.hs
+++ b/compiler/main/HscTypes.hs
@@ -77,7 +77,7 @@ module HscTypes (
 
         -- * Interfaces
         ModIface(..), mkIfaceWarnCache, mkIfaceHashCache, mkIfaceFixCache,
-        emptyIfaceWarnCache, mi_boot, mi_fix,
+        emptyIfaceWarnCache, mi_boot, mi_fix, mi_exports,
         mi_semantic_module,
         mi_free_holes,
         renameFreeHoles,
@@ -210,13 +210,14 @@ import qualified GHC.LanguageExtensions as LangExt
 
 import Foreign
 import Control.Monad    ( guard, liftM, ap )
-import Data.Foldable    ( foldl' )
+import Data.Foldable    ( foldl', toList )
 import Data.IORef
 import Data.Time
 import Exception
 import System.FilePath
 import Control.Concurrent
 import System.Process   ( ProcessHandle )
+import Data.Array
 
 -- -----------------------------------------------------------------------------
 -- Compilation state
@@ -877,7 +878,7 @@ data ModIface
                 -- NOT STRICT!  we read this field lazily from the interface file
                 -- It is *only* consulted by the recompilation checker
 
-        mi_exports  :: ![IfaceExport],
+        mi_exports_arr :: !(Array Int IfaceExport),
                 -- ^ Exports
                 -- Kept sorted by (mod,occ), to make version comparisons easier
                 -- Records the modules that are the declaration points for things
@@ -995,6 +996,9 @@ mi_free_holes iface =
   where
     cands = map fst (dep_mods (mi_deps iface))
 
+mi_exports :: ModIface -> [IfaceExport]
+mi_exports = toList . mi_exports_arr
+
 -- | Given a set of free holes, and a unit identifier, rename
 -- the free holes according to the instantiation of the unit
 -- identifier.  For example, if we have A and B free, and
@@ -1022,7 +1026,7 @@ instance Binary ModIface where
                  mi_finsts    = hasFamInsts,
                  mi_deps      = deps,
                  mi_usages    = usages,
-                 mi_exports   = exports,
+                 mi_exports_arr =  exports,
                  mi_exp_hash  = exp_hash,
                  mi_used_th   = used_th,
                  mi_fixities  = fixities,
@@ -1103,7 +1107,7 @@ instance Binary ModIface where
                  mi_finsts      = hasFamInsts,
                  mi_deps        = deps,
                  mi_usages      = usages,
-                 mi_exports     = exports,
+                 mi_exports_arr = exports,
                  mi_exp_hash    = exp_hash,
                  mi_used_th     = used_th,
                  mi_anns        = anns,
@@ -1141,7 +1145,7 @@ emptyModIface mod
                mi_hsc_src     = HsSrcFile,
                mi_deps        = noDependencies,
                mi_usages      = [],
-               mi_exports     = [],
+               mi_exports_arr = array (0,-1) [],
                mi_exp_hash    = fingerprint0,
                mi_used_th     = False,
                mi_fixities    = [],
diff --git a/compiler/prelude/PrelInfo.hs b/compiler/prelude/PrelInfo.hs
index 8d1f140ca2..06b79d0537 100644
--- a/compiler/prelude/PrelInfo.hs
+++ b/compiler/prelude/PrelInfo.hs
@@ -247,13 +247,13 @@ GHC.Prim "exports" all the primops and primitive types, some
 wired-in Ids.
 -}
 
-ghcPrimExports :: [IfaceExport]
-ghcPrimExports
- = map (avail . idName) ghcPrimIds ++
+ghcPrimExports :: Array Int IfaceExport
+ghcPrimExports = let
+ exports_list = map (avail . idName) ghcPrimIds ++
    map (avail . idName . primOpId) allThePrimOps ++
    [ AvailTC n [n] []
    | tc <- funTyCon : primTyCons, let n = tyConName tc  ]
-
+ in listArray (0, length exports_list - 1) exports_list
 {-
 ************************************************************************
 *                                                                      *
diff --git a/compiler/typecheck/TcBackpack.hs b/compiler/typecheck/TcBackpack.hs
index 31055fdb7c..83d7c0a34e 100644
--- a/compiler/typecheck/TcBackpack.hs
+++ b/compiler/typecheck/TcBackpack.hs
@@ -66,6 +66,7 @@ import Util
 
 import Control.Monad
 import Data.List (find, foldl')
+import Data.Array
 
 import {-# SOURCE #-} TcRnDriver
 
@@ -362,7 +363,7 @@ tcRnMergeSignatures hsc_env hpm orig_tcg_env iface =
 thinModIface :: [AvailInfo] -> ModIface -> ModIface
 thinModIface avails iface =
     iface {
-        mi_exports = avails,
+        mi_exports_arr = listArray (0, length avails - 1) avails,
         -- mi_fixities = ...,
         -- mi_warns = ...,
         -- mi_anns = ...,
diff --git a/compiler/utils/Binary.hs b/compiler/utils/Binary.hs
index a7bbfd51ad..9dfe2d7d80 100644
--- a/compiler/utils/Binary.hs
+++ b/compiler/utils/Binary.hs
@@ -73,6 +73,8 @@ import SrcLoc
 
 import Foreign
 import Data.Array
+import Data.Array.IO
+import Data.Array.Unsafe
 import Data.ByteString (ByteString)
 import qualified Data.ByteString.Internal as BS
 import qualified Data.ByteString.Unsafe   as BS
@@ -93,6 +95,7 @@ import System.IO.Unsafe         ( unsafeInterleaveIO )
 import System.IO.Error          ( mkIOError, eofErrorType )
 import GHC.Real                 ( Ratio(..) )
 import GHC.Serialized
+import Data.Foldable
 
 type BinArray = ForeignPtr Word8
 
@@ -413,6 +416,26 @@ instance Binary a => Binary [a] where
             loop n = do a <- get bh; as <- loop (n-1); return (a:as)
         loop len
 
+instance Binary a => Binary (Array Int a) where
+    put_ bh l = do
+        let len = length l
+        if (len < 0xff)
+          then putByte bh (fromIntegral len :: Word8)
+          else do putByte bh 0xff; put_ bh (fromIntegral len :: Word32)
+        mapM_ (put_ bh) l
+    get bh = do
+        b <- getByte bh
+        len <- if b == 0xff
+                  then get bh
+                  else return (fromIntegral b :: Word32)
+        let last_index = fromIntegral len - 1
+        arr <- newIOArray_ (0, last_index)
+        when (len > 0) $ for_ [0..last_index] $
+          \i -> get bh >>= writeArray arr i
+        unsafeFreeze arr
+      where
+        newIOArray_ = newArray_ :: (Int, Int) -> IO (IOArray Int a)
+
 instance (Binary a, Binary b) => Binary (a,b) where
     put_ bh (a,b) = do put_ bh a; put_ bh b
     get bh        = do a <- get bh