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, 15 insertions, 7 deletions

diff --git a/compiler/GHC/Unit/Module/ModSummary.hs b/compiler/GHC/Unit/Module/ModSummary.hs
index 324cca33a3..339afd4564 100644
--- a/compiler/GHC/Unit/Module/ModSummary.hs
+++ b/compiler/GHC/Unit/Module/ModSummary.hs
@@ -10,6 +10,7 @@ module GHC.Unit.Module.ModSummary
    , ms_installed_mod
    , ms_mod_name
    , ms_imps
+   , ms_mnwib
    , ms_home_allimps
    , ms_home_srcimps
    , ms_home_imps
@@ -39,6 +40,7 @@ import GHC.Data.Maybe
 import GHC.Data.FastString
 import GHC.Data.StringBuffer ( StringBuffer )
 
+import GHC.Utils.Fingerprint
 import GHC.Utils.Outputable
 
 import Data.Time
@@ -73,14 +75,15 @@ data ModSummary
           -- ^ The module source either plain Haskell, hs-boot, or hsig
         ms_location     :: ModLocation,
           -- ^ Location of the various files belonging to the module
-        ms_hs_date      :: UTCTime,
-          -- ^ Timestamp of source file
+        ms_hs_hash      :: Fingerprint,
+          -- ^ Content hash of source file
         ms_obj_date     :: Maybe UTCTime,
           -- ^ Timestamp of object, if we have one
+        ms_dyn_obj_date     :: !(Maybe UTCTime),
+          -- ^ Timestamp of dynamic object, if we have one
         ms_iface_date   :: Maybe UTCTime,
-          -- ^ Timestamp of hi file, if we *only* are typechecking (it is
-          -- 'Nothing' otherwise.
-          -- See Note [Recompilation checking in -fno-code mode] and #9243
+          -- ^ Timestamp of hi file, if we have one
+          -- See Note [When source is considered modified] and #9243
         ms_hie_date   :: Maybe UTCTime,
           -- ^ Timestamp of hie file, if we have one
         ms_srcimps      :: [(Maybe FastString, Located ModuleName)],
@@ -145,7 +148,7 @@ ms_home_imps = home_imps . ms_imps
 -- and let @compile@ read from that file on the way back up.
 
 -- The ModLocation is stable over successive up-sweeps in GHCi, wheres
--- the ms_hs_date and imports can, of course, change
+-- the ms_hs_hash and imports can, of course, change
 
 msHsFilePath, msHiFilePath, msObjFilePath :: ModSummary -> FilePath
 msHsFilePath  ms = expectJust "msHsFilePath" (ml_hs_file  (ms_location ms))
@@ -159,10 +162,13 @@ msDynObjFilePath ms dflags = dynamicOutputFile dflags (msObjFilePath ms)
 isBootSummary :: ModSummary -> IsBootInterface
 isBootSummary ms = if ms_hsc_src ms == HsBootFile then IsBoot else NotBoot
 
+ms_mnwib :: ModSummary -> ModuleNameWithIsBoot
+ms_mnwib ms = GWIB (ms_mod_name ms) (isBootSummary ms)
+
 instance Outputable ModSummary where
    ppr ms
       = sep [text "ModSummary {",
-             nest 3 (sep [text "ms_hs_date = " <> text (show (ms_hs_date ms)),
+             nest 3 (sep [text "ms_hs_hash = " <> text (show (ms_hs_hash ms)),
                           text "ms_mod =" <+> ppr (ms_mod ms)
                                 <> text (hscSourceString (ms_hsc_src ms)) <> comma,
                           text "ms_textual_imps =" <+> ppr (ms_textual_imps ms),
@@ -170,6 +176,8 @@ instance Outputable ModSummary where
              char '}'
             ]
 
+-- | Find the first target in the provided list which matches the specified
+-- 'ModSummary'.
 findTarget :: ModSummary -> [Target] -> Maybe Target
 findTarget ms ts =
   case filter (matches ms) ts of