driver: Cleanups related to ModLocation

ModLocation is the data type which tells you the locations of all the
build products which can affect recompilation. It is now computed in one
place and not modified through the pipeline. Important locations will
now just consult ModLocation rather than construct the dynamic object
path incorrectly.

* Add paths for dynamic object and dynamic interface files to
  ModLocation.
* Always use the paths from mod location when looking for where to find
  any interface or object file.
* Always use the paths in a ModLocation when deciding where to write an
  interface and object file.
* Remove `dynamicOutputFile` and `dynamicOutputHi` functions which
  *calculated* (incorrectly) the location of `dyn_o` and `dyn_hi` files.
* Don't set `outputFile_` and so-on in `enableCodeGenWhen`, `-o` and
  hence `outputFile_` should not affect the location of object files in
  `--make` mode. It is now sufficient to just update the ModLocation with
  the temporary paths.
* In `hscGenBackendPipeline` don't recompute the `ModLocation` to
  account for `-dynamic-too`, the paths are now accurate from the start
  of the run.
* Rename `getLocation` to `mkOneShotModLocation`, as that's the only
  place it's used. Increase the locality of the definition by moving it
  close to the use-site.
* Load the dynamic interface from ml_dyn_hi_file rather than attempting
  to reconstruct it in load_dynamic_too.
* Add a variety of tests to check how -o -dyno etc interact with each
  other.

Some other clean-ups

* DeIOify mkHomeModLocation and friends, they are all pure functions.
* Move FinderOpts into GHC.Driver.Config.Finder, next to initFinderOpts.
* Be more precise about whether we mean outputFile or outputFile_: there
  were many places where outputFile was used but the result shouldn't have
  been affected by `-dyno` (for example the filename of the resulting
  executable). In these places dynamicNow would never be set but it's
  still more precise to not allow for this possibility.
* Typo fixes suffices -> suffixes in the appropiate places.

3 files changed, 28 insertions, 5 deletions

diff --git a/compiler/GHC/Unit/Module/Graph.hs b/compiler/GHC/Unit/Module/Graph.hs
index 027cbef51b..bf7abfea99 100644
--- a/compiler/GHC/Unit/Module/Graph.hs
+++ b/compiler/GHC/Unit/Module/Graph.hs
@@ -204,7 +204,7 @@ showModMsg dflags recomp (ModuleNode (ExtendedModSummary mod_summary _)) =
     op       = normalise
     mod      = moduleName (ms_mod mod_summary)
     mod_str  = showPpr dflags mod ++ hscSourceString (ms_hsc_src mod_summary)
-    dyn_file = op $ msDynObjFilePath mod_summary dflags
+    dyn_file = op $ msDynObjFilePath mod_summary
     obj_file = case backend dflags of
                 Interpreter | recomp -> "interpreted"
                 NoBackend            -> "nothing"
diff --git a/compiler/GHC/Unit/Module/Location.hs b/compiler/GHC/Unit/Module/Location.hs
index ff5354bfdb..866ccf127a 100644
--- a/compiler/GHC/Unit/Module/Location.hs
+++ b/compiler/GHC/Unit/Module/Location.hs
@@ -16,7 +16,7 @@ import GHC.Utils.Outputable
 -- | Module Location
 --
 -- Where a module lives on the file system: the actual locations
--- of the .hs, .hi and .o files, if we have them.
+-- of the .hs, .hi, .dyn_hi, .o, .dyn_o and .hie files, if we have them.
 --
 -- For a module in another unit, the ml_hs_file and ml_obj_file components of
 -- ModLocation are undefined.
@@ -25,6 +25,16 @@ import GHC.Utils.Outputable
 -- correspond to actual files yet: for example, even if the object
 -- file doesn't exist, the ModLocation still contains the path to
 -- where the object file will reside if/when it is created.
+--
+-- The paths of anything which can affect recompilation should be placed inside
+-- ModLocation.
+--
+-- When a ModLocation is created none of the filepaths will have -boot suffixes.
+-- This is because in --make mode the ModLocation is put in the finder cache which
+-- is indexed by ModuleName, when a ModLocation is retrieved from the FinderCache
+-- the boot suffixes are appended.
+-- The other case is in -c mode, there the ModLocation immediately gets given the
+-- boot suffixes in mkOneShotModLocation.
 
 data ModLocation
    = ModLocation {
@@ -37,12 +47,20 @@ data ModLocation
                 -- yet.  Always of form foo.hi, even if there is an
                 -- hi-boot file (we add the -boot suffix later)
 
+        ml_dyn_hi_file :: FilePath,
+                -- ^ Where the .dyn_hi file is, whether or not it exists
+                -- yet.
+
         ml_obj_file  :: FilePath,
                 -- ^ Where the .o file is, whether or not it exists yet.
                 -- (might not exist either because the module hasn't
                 -- been compiled yet, or because it is part of a
                 -- unit with a .a file)
 
+        ml_dyn_obj_file :: FilePath,
+                -- ^ Where the .dy file is, whether or not it exists
+                -- yet.
+
         ml_hie_file  :: FilePath
                 -- ^ Where the .hie file is, whether or not it exists
                 -- yet.
@@ -73,7 +91,9 @@ addBootSuffixLocn :: ModLocation -> ModLocation
 addBootSuffixLocn locn
   = locn { ml_hs_file  = fmap addBootSuffix (ml_hs_file locn)
          , ml_hi_file  = addBootSuffix (ml_hi_file locn)
+         , ml_dyn_hi_file = addBootSuffix (ml_dyn_hi_file locn)
          , ml_obj_file = addBootSuffix (ml_obj_file locn)
+         , ml_dyn_obj_file = addBootSuffix (ml_dyn_obj_file locn)
          , ml_hie_file = addBootSuffix (ml_hie_file locn) }
 
 -- | Add the @-boot@ suffix to all output file paths associated with the
@@ -81,7 +101,10 @@ addBootSuffixLocn locn
 addBootSuffixLocnOut :: ModLocation -> ModLocation
 addBootSuffixLocnOut locn
   = locn { ml_hi_file  = addBootSuffix (ml_hi_file locn)
+         , ml_dyn_hi_file = addBootSuffix (ml_dyn_hi_file locn)
          , ml_obj_file = addBootSuffix (ml_obj_file locn)
-         , ml_hie_file = addBootSuffix (ml_hie_file locn) }
+         , ml_dyn_obj_file = addBootSuffix (ml_dyn_obj_file locn)
+         , ml_hie_file = addBootSuffix (ml_hie_file locn)
+         }
 
 
diff --git a/compiler/GHC/Unit/Module/ModSummary.hs b/compiler/GHC/Unit/Module/ModSummary.hs
index 1a8cddec61..9cf736a37a 100644
--- a/compiler/GHC/Unit/Module/ModSummary.hs
+++ b/compiler/GHC/Unit/Module/ModSummary.hs
@@ -156,8 +156,8 @@ msHsFilePath  ms = expectJust "msHsFilePath" (ml_hs_file  (ms_location ms))
 msHiFilePath  ms = ml_hi_file  (ms_location ms)
 msObjFilePath ms = ml_obj_file (ms_location ms)
 
-msDynObjFilePath :: ModSummary -> DynFlags -> FilePath
-msDynObjFilePath ms dflags = dynamicOutputFile dflags (msObjFilePath ms)
+msDynObjFilePath :: ModSummary -> FilePath
+msDynObjFilePath ms = ml_dyn_obj_file (ms_location ms)
 
 -- | Did this 'ModSummary' originate from a hs-boot file?
 isBootSummary :: ModSummary -> IsBootInterface