Driver Rework Patch

This patch comprises of four different but closely related ideas. The
net result is fixing a large number of open issues with the driver
whilst making it simpler to understand.

1. Use the hash of the source file to determine whether the source file
has changed or not. This makes the recompilation checking more robust to
modern build systems which are liable to copy files around changing
their modification times.

2. Remove the concept of a "stable module", a stable module was one
where the object file was older than the source file, and all transitive
dependencies were also stable. Now we don't rely on the modification
time of the source file, the notion of stability is moot.

3. Fix TH/plugin recompilation after the removal of stable modules. The
TH recompilation check used to rely on stable modules. Now there is a
uniform and simple way, we directly track the linkables which were
loaded into the interpreter whilst compiling a module. This is an
over-approximation but more robust wrt package dependencies changing.

4. Fix recompilation checking for dynamic object files. Now we actually
check if the dynamic object file exists when compiling with -dynamic-too

Fixes #19774 #19771 #19758 #17434 #11556 #9121 #8211 #16495 #7277 #16093

1 files changed, 5 insertions, 42 deletions

diff --git a/compiler/GHC.hs b/compiler/GHC.hs
index f71caa6f15..7e882dbd8b 100644
--- a/compiler/GHC.hs
+++ b/compiler/GHC.hs
@@ -57,7 +57,7 @@ module GHC (
         SuccessFlag(..), succeeded, failed,
         defaultWarnErrLogger, WarnErrLogger,
         workingDirectoryChanged,
-        parseModule, typecheckModule, desugarModule, loadModule,
+        parseModule, typecheckModule, desugarModule,
         ParsedModule(..), TypecheckedModule(..), DesugaredModule(..),
         TypecheckedSource, ParsedSource, RenamedSource,   -- ditto
         TypecheckedMod, ParsedMod,
@@ -314,7 +314,6 @@ import GHC.Driver.Config
 import GHC.Driver.Main
 import GHC.Driver.Make
 import GHC.Driver.Hooks
-import GHC.Driver.Pipeline   ( compileOne' )
 import GHC.Driver.Monad
 import GHC.Driver.Ppr
 
@@ -357,6 +356,7 @@ import GHC.Utils.Misc
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Logger
+import GHC.Utils.Fingerprint
 
 import GHC.Core.Predicate
 import GHC.Core.Type  hiding( typeKind )
@@ -387,7 +387,6 @@ import GHC.Types.TyThing
 import GHC.Types.Name.Env
 import GHC.Types.Name.Ppr
 import GHC.Types.TypeEnv
-import GHC.Types.SourceFile
 
 import GHC.Unit
 import GHC.Unit.Env
@@ -407,7 +406,6 @@ import Data.Set (Set)
 import qualified Data.Set as S
 import qualified Data.Sequence as Seq
 import Data.Maybe
-import Data.Time
 import Data.Typeable    ( Typeable )
 import Data.Word        ( Word8 )
 import Control.Monad
@@ -750,7 +748,7 @@ setProgramDynFlags_ invalidate_needed dflags = do
 -- old log_action.  This is definitely wrong (#7478).
 --
 -- Hence, we invalidate the ModSummary cache after changing the
--- DynFlags.  We do this by tweaking the date on each ModSummary, so
+-- DynFlags.  We do this by tweaking the hash on each ModSummary, so
 -- that the next downsweep will think that all the files have changed
 -- and preprocess them again.  This won't necessarily cause everything
 -- to be recompiled, because by the time we check whether we need to
@@ -761,7 +759,7 @@ invalidateModSummaryCache :: GhcMonad m => m ()
 invalidateModSummaryCache =
   modifySession $ \h -> h { hsc_mod_graph = mapMG inval (hsc_mod_graph h) }
  where
-  inval ms = ms { ms_hs_date = addUTCTime (-1) (ms_hs_date ms) }
+  inval ms = ms { ms_hs_hash = fingerprint0 }
 
 -- | Returns the program 'DynFlags'.
 getProgramDynFlags :: GhcMonad m => m DynFlags
@@ -783,7 +781,7 @@ setInteractiveDynFlags dflags = do
 
     -- Initialise (load) plugins in the interactive environment with the new
     -- DynFlags
-    plugin_env <- liftIO $ initializePlugins $ mkInteractiveHscEnv $
+    plugin_env <- liftIO $ flip initializePlugins Nothing $ mkInteractiveHscEnv $
                     hsc_env0 { hsc_IC = ic0 { ic_dflags = dflags'' }}
 
     -- Update both plugins cache and DynFlags in the interactive context.
@@ -1185,41 +1183,6 @@ desugarModule tcm = do
        dm_core_module        = guts
      }
 
--- | Load a module.  Input doesn't need to be desugared.
---
--- A module must be loaded before dependent modules can be typechecked.  This
--- always includes generating a 'ModIface' and, depending on the
--- @DynFlags@\'s 'GHC.Driver.Session.backend', may also include code generation.
---
--- This function will always cause recompilation and will always overwrite
--- previous compilation results (potentially files on disk).
---
-loadModule :: (TypecheckedMod mod, GhcMonad m) => mod -> m mod
-loadModule tcm = do
-   let ms = modSummary tcm
-   let mod = ms_mod_name ms
-   let loc = ms_location ms
-   let (tcg, _details) = tm_internals tcm
-
-   mb_linkable <- case ms_obj_date ms of
-                     Just t | t > ms_hs_date ms  -> do
-                         l <- liftIO $ findObjectLinkable (ms_mod ms)
-                                                  (ml_obj_file loc) t
-                         return (Just l)
-                     _otherwise -> return Nothing
-
-   let source_modified | isNothing mb_linkable = SourceModified
-                       | otherwise             = SourceUnmodified
-                       -- we can't determine stability here
-
-   -- compile doesn't change the session
-   hsc_env <- getSession
-   mod_info <- liftIO $ compileOne' (Just tcg) Nothing
-                                    hsc_env ms 1 1 Nothing mb_linkable
-                                    source_modified
-
-   modifySession $ hscUpdateHPT (\hpt -> addToHpt hpt mod mod_info)
-   return tcm
 
 
 -- %************************************************************************