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, 11 insertions, 6 deletions

diff --git a/compiler/GHC/Driver/Backpack.hs b/compiler/GHC/Driver/Backpack.hs
index dceed41099..1d5b567359 100644
--- a/compiler/GHC/Driver/Backpack.hs
+++ b/compiler/GHC/Driver/Backpack.hs
@@ -50,6 +50,7 @@ import GHC.Types.Unique.DFM
 import GHC.Types.Unique.DSet
 
 import GHC.Utils.Outputable
+import GHC.Utils.Fingerprint
 import GHC.Utils.Misc
 import GHC.Utils.Panic
 import GHC.Utils.Error
@@ -184,6 +185,9 @@ withBkpSession cid insts deps session_type do_this = do
             { backend = case session_type of
                             TcSession -> NoBackend
                             _         -> backend dflags
+            , ghcLink = case session_type of
+                            TcSession -> NoLink
+                            _         -> ghcLink dflags
             , homeUnitInstantiations_ = insts
                                      -- if we don't have any instantiation, don't
                                      -- fill `homeUnitInstanceOfId` as it makes no
@@ -333,7 +337,7 @@ buildUnit session cid insts lunit = do
             linkables = map (expectJust "bkp link" . hm_linkable)
                       . filter ((==HsSrcFile) . mi_hsc_src . hm_iface)
                       $ home_mod_infos
-            getOfiles (LM _ _ us) = map nameOfObject (filter isObject us)
+            getOfiles LM{ linkableUnlinked = us } = map nameOfObject (filter isObject us)
             obj_files = concatMap getOfiles linkables
             state     = hsc_units hsc_env
 
@@ -751,7 +755,7 @@ summariseRequirement pn mod_name = do
                  (unpackFS pn_fs </> moduleNameSlashes mod_name) "hsig"
 
     env <- getBkpEnv
-    time <- liftIO $ getModificationUTCTime (bkp_filename env)
+    src_hash <- liftIO $ getFileHash (bkp_filename env)
     hi_timestamp <- liftIO $ modificationTimeIfExists (ml_hi_file location)
     hie_timestamp <- liftIO $ modificationTimeIfExists (ml_hie_file location)
     let loc = srcLocSpan (mkSrcLoc (mkFastString (bkp_filename env)) 1 1)
@@ -765,8 +769,9 @@ summariseRequirement pn mod_name = do
         ms_mod = mod,
         ms_hsc_src = HsigFile,
         ms_location = location,
-        ms_hs_date = time,
+        ms_hs_hash = src_hash,
         ms_obj_date = Nothing,
+        ms_dyn_obj_date = Nothing,
         ms_iface_date = hi_timestamp,
         ms_hie_date = hie_timestamp,
         ms_srcimps = [],
@@ -802,7 +807,6 @@ summariseDecl _pn hsc_src lmodname@(L loc modname) Nothing
                          emptyModNodeMap -- GHC API recomp not supported
                          (hscSourceToIsBoot hsc_src)
                          lmodname
-                         True -- Target lets you disallow, but not here
                          Nothing -- GHC API buffer support not supported
                          [] -- No exclusions
          case r of
@@ -849,7 +853,7 @@ hsModuleToModSummary pn hsc_src modname
                         _ -> location0
     -- This duplicates a pile of logic in GHC.Driver.Make
     env <- getBkpEnv
-    time <- liftIO $ getModificationUTCTime (bkp_filename env)
+    src_hash <- liftIO $ getFileHash (bkp_filename env)
     hi_timestamp <- liftIO $ modificationTimeIfExists (ml_hi_file location)
     hie_timestamp <- liftIO $ modificationTimeIfExists (ml_hie_file location)
 
@@ -898,8 +902,9 @@ hsModuleToModSummary pn hsc_src modname
                     hpm_module = hsmod,
                     hpm_src_files = [] -- TODO if we preprocessed it
                 }),
-            ms_hs_date = time,
+            ms_hs_hash = src_hash,
             ms_obj_date = Nothing, -- TODO do this, but problem: hi_timestamp is BOGUS
+            ms_dyn_obj_date = Nothing, -- TODO do this, but problem: hi_timestamp is BOGUS
             ms_iface_date = hi_timestamp,
             ms_hie_date = hie_timestamp
           }