Refactor Libffi and RTS rules

This removes a hack that copies libffi files to the rts
build directory. This was done in a libffi rule, but now
an rts rule correctly needs and copies the relevant
files from the libffi build dir to the rts build dir.

Issues: #16272 #16304

10 files changed, 256 insertions, 139 deletions

diff --git a/hadrian/src/Hadrian/Utilities.hs b/hadrian/src/Hadrian/Utilities.hs
index 42125c750b..e8bf7933e8 100644
--- a/hadrian/src/Hadrian/Utilities.hs
+++ b/hadrian/src/Hadrian/Utilities.hs
@@ -16,7 +16,7 @@ module Hadrian.Utilities (
     BuildRoot (..), buildRoot, buildRootRules, isGeneratedSource,
 
     -- * File system operations
-    copyFile, copyFileUntracked, createFileLinkUntracked, fixFile,
+    copyFile, copyFileUntracked, createFileLink, createFileLinkUntracked, fixFile,
     makeExecutable, moveFile, removeFile, createDirectory, copyDirectory,
     moveDirectory, removeDirectory,
 
@@ -289,14 +289,25 @@ infixl 1 <&>
 isGeneratedSource :: FilePath -> Action Bool
 isGeneratedSource file = buildRoot <&> (`isPrefixOf` file)
 
--- | Link a file tracking the source. Create the target directory if missing.
+-- | Link a file (without tracking the link target). Create the target directory
+-- if missing.
 createFileLinkUntracked :: FilePath -> FilePath -> Action ()
 createFileLinkUntracked linkTarget link = do
-    let dir = takeDirectory linkTarget
+    let dir = takeDirectory link
     liftIO $ IO.createDirectoryIfMissing True dir
     putProgressInfo =<< renderCreateFileLink linkTarget link
     quietly . liftIO $ IO.createFileLink linkTarget link
 
+-- | Link a file tracking the link target. Create the target directory if
+-- missing.
+createFileLink :: FilePath -> FilePath -> Action ()
+createFileLink linkTarget link = do
+    let source = if isAbsolute linkTarget
+                    then linkTarget
+                    else takeDirectory link -/- linkTarget
+    need [source]
+    createFileLinkUntracked linkTarget link
+
 -- | Copy a file tracking the source. Create the target directory if missing.
 copyFile :: FilePath -> FilePath -> Action ()
 copyFile source target = do
diff --git a/hadrian/src/Rules.hs b/hadrian/src/Rules.hs
index 78e3790d48..240e08dcdc 100644
--- a/hadrian/src/Rules.hs
+++ b/hadrian/src/Rules.hs
@@ -26,7 +26,6 @@ import qualified Rules.SimpleTargets
 import Settings
 import Target
 import UserSettings
-import Utilities
 
 
 -- | @tool-args@ is used by tooling in order to get the arguments necessary
@@ -120,7 +119,7 @@ packageTargets includeGhciLib stage pkg = do
             let pkgWays = if pkg == rts then getRtsWays else getLibraryWays
             ways  <- interpretInContext context pkgWays
             libs  <- mapM (pkgLibraryFile . Context stage pkg) ways
-            more  <- libraryTargets includeGhciLib context
+            more  <- Rules.Library.libraryTargets includeGhciLib context
             setupConfig <- pkgSetupConfigFile context
             return $ [setupConfig] ++ libs ++ more
         else do -- The only target of a program package is the executable.
diff --git a/hadrian/src/Rules/Compile.hs b/hadrian/src/Rules/Compile.hs
index 8bd60dd960..0bf6f1db01 100644
--- a/hadrian/src/Rules/Compile.hs
+++ b/hadrian/src/Rules/Compile.hs
@@ -10,6 +10,7 @@ import Rules.Generate
 import Settings
 import Target
 import Utilities
+import Rules.Library
 
 import qualified Text.Parsec as Parsec
 
diff --git a/hadrian/src/Rules/Generate.hs b/hadrian/src/Rules/Generate.hs
index 2538e76c0a..d69dd38016 100644
--- a/hadrian/src/Rules/Generate.hs
+++ b/hadrian/src/Rules/Generate.hs
@@ -54,7 +54,7 @@ compilerDependencies = do
     rtsPath <- expr (rtsBuildPath stage)
     mconcat [ return ((root -/-) <$> derivedConstantsDependencies)
             , notStage0 ? isGmp ? return [gmpPath -/- gmpLibraryH]
-            , notStage0 ? return ((rtsPath -/-) <$> libffiDependencies)
+            , notStage0 ? return ((rtsPath -/-) <$> libffiHeaderFiles)
             , return $ fmap (ghcPath -/-)
                   [ "primop-can-fail.hs-incl"
                   , "primop-code-size.hs-incl"
@@ -80,7 +80,7 @@ generatedDependencies = do
     includes <- expr includesDependencies
     mconcat [ package compiler ? compilerDependencies
             , package ghcPrim  ? ghcPrimDependencies
-            , package rts      ? return (fmap (rtsPath -/-) libffiDependencies
+            , package rts      ? return (fmap (rtsPath -/-) libffiHeaderFiles
                 ++ includes
                 ++ fmap (root -/-) derivedConstantsDependencies)
             , stage0 ? return includes ]
diff --git a/hadrian/src/Rules/Libffi.hs b/hadrian/src/Rules/Libffi.hs
index ddc739d735..b185d9a601 100644
--- a/hadrian/src/Rules/Libffi.hs
+++ b/hadrian/src/Rules/Libffi.hs
@@ -1,4 +1,10 @@
-module Rules.Libffi (libffiRules, libffiDependencies, libffiName) where
+{-# LANGUAGE TypeFamilies #-}
+
+module Rules.Libffi (
+    LibffiDynLibs(..),
+    needLibffi, askLibffilDynLibs, libffiRules, libffiLibrary, libffiHeaderFiles,
+    libffiHeaders, libffiSystemHeaders, libffiName
+    ) where
 
 import Hadrian.Utilities
 
@@ -7,26 +13,33 @@ import Settings.Builders.Common
 import Target
 import Utilities
 
-{-
-Note [Hadrian: install libffi hack]
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+-- | Oracle question type. The oracle returns the list of dynamic
+-- libffi library file paths (all but one of which should be symlinks).
+newtype LibffiDynLibs = LibffiDynLibs Stage
+        deriving (Eq, Show, Hashable, Binary, NFData)
+type instance RuleResult LibffiDynLibs = [FilePath]
+
+askLibffilDynLibs :: Stage -> Action [FilePath]
+askLibffilDynLibs stage = askOracle (LibffiDynLibs stage)
 
-There are 2 important steps in handling libffi's .a and .so files:
+-- | The path to the dynamic library manifest file. The file contains all file
+-- paths to libffi dynamic library file paths.
+dynLibManifest' :: Monad m => m FilePath -> Stage -> m FilePath
+dynLibManifest' getRoot stage = do
+    root <- getRoot
+    return $ root -/- stageString stage -/- pkgName libffi -/- ".dynamiclibs"
 
-  1. libffi's .a and .so|.dynlib|.dll files are copied from the libffi build dir
-  to the rts build dir. This is because libffi is ultimately bundled with the
-  rts package. Relevant code is in the libffiRules function.
-  2. The rts is "installed" via the hadrian/src/Hadrian/Haskell/Cabal/Parse.hs
-  copyPackage action. This uses the "cabal copy" command which (among other
-  things) attempts to copy the bundled .a and .so|.dynlib|.dll files from the
-  rts build dir to the install dir.
+dynLibManifestRules :: Stage -> Rules FilePath
+dynLibManifestRules = dynLibManifest' buildRootRules
 
-There is an issue in step 1. that the name of the shared library files is not
-know untill after libffi is built. As a workaround, the rts package needs just
-the libffiDependencies, and the corresponding rule (defined below in
-libffiRules) does the extra work of installing the shared library files into the
-rts build directory after building libffi.
--}
+dynLibManifest :: Stage -> Action FilePath
+dynLibManifest = dynLibManifest' buildRoot
+
+-- | Need the (locally built) libffi library.
+needLibffi :: Stage -> Action ()
+needLibffi stage = do
+    manifest <- dynLibManifest stage
+    need [manifest]
 
 -- | Context for @libffi@.
 libffiContext :: Stage -> Action Context
@@ -51,18 +64,21 @@ libffiName' windows dynamic
     = (if dynamic then "" else "C")
     ++ (if windows then "ffi-6" else "ffi")
 
-libffiDependencies :: [FilePath]
-libffiDependencies = ["ffi.h", "ffitarget.h"]
-
 libffiLibrary :: FilePath
 libffiLibrary = "inst/lib/libffi.a"
 
-rtsLibffiLibrary :: Stage -> Way -> Action FilePath
-rtsLibffiLibrary stage way = do
-    name    <- libffiLibraryName
-    suf     <- libsuf stage way
-    rtsPath <- rtsBuildPath stage
-    return $ rtsPath -/- "lib" ++ name ++ suf
+libffiHeaderFiles :: [FilePath]
+libffiHeaderFiles = ["ffi.h", "ffitarget.h"]
+
+libffiHeaders :: Stage -> Action [FilePath]
+libffiHeaders stage = do
+    path <- libffiBuildPath stage
+    return $ fmap ((path -/- "inst/include") -/-) libffiHeaderFiles
+
+libffiSystemHeaders :: Action [FilePath]
+libffiSystemHeaders = do
+    ffiIncludeDir <- setting FfiIncludeDir
+    return $ fmap (ffiIncludeDir -/-) libffiHeaderFiles
 
 fixLibffiMakefile :: FilePath -> String -> String
 fixLibffiMakefile top =
@@ -88,84 +104,46 @@ configureEnvironment stage = do
              , return . AddEnv "LDFLAGS" $ unwords ldFlags ++ " -w" ]
 
 libffiRules :: Rules ()
-libffiRules = forM_ [Stage1 ..] $ \stage -> do
+libffiRules = do
+  _ <- addOracleCache $ \ (LibffiDynLibs stage)
+                         -> readFileLines =<< dynLibManifest stage
+  forM_ [Stage1 ..] $ \stage -> do
     root <- buildRootRules
     let path       = root -/- stageString stage
         libffiPath = path -/- pkgName libffi -/- "build"
-        libffiOuts = [libffiPath -/- libffiLibrary] ++
-                     fmap ((path -/- "rts/build") -/-) libffiDependencies
 
     -- We set a higher priority because this rule overlaps with the build rule
     -- for static libraries 'Rules.Library.libraryRules'.
-    -- See [Hadrian: install libffi hack], this rule installs libffi into the
-    -- rts build path.
-    priority 2.0 $ libffiOuts &%> \_ -> do
+    dynLibMan <- dynLibManifestRules stage
+    let topLevelTargets =  [ libffiPath -/- libffiLibrary
+                           , dynLibMan
+                           ]
+    priority 2 $ topLevelTargets &%> \_ -> do
         context <- libffiContext stage
-        useSystemFfi <- flag UseSystemFfi
-        rtsPath      <- rtsBuildPath stage
-        if useSystemFfi
-        then do
-            ffiIncludeDir <- setting FfiIncludeDir
-            putBuild "| System supplied FFI library will be used"
-            forM_ ["ffi.h", "ffitarget.h"] $ \file ->
-                copyFile (ffiIncludeDir -/- file) (rtsPath -/- file)
-            putSuccess "| Successfully copied system FFI library header files"
-        else do
-            build $ target context (Make libffiPath) [] []
-
-            -- Here we produce 'libffiDependencies'
-            headers <- liftIO $ getDirectoryFilesIO libffiPath ["inst/include/*"]
-            forM_ headers $ \header -> do
-                let target = rtsPath -/- takeFileName header
-                copyFileUntracked (libffiPath -/- header) target
-                produces [target]
-
-            -- Find ways.
-            ways <- interpretInContext context
-                                       (getLibraryWays <> getRtsWays)
-            let (dynamicWays, staticWays) = partition (wayUnit Dynamic) ways
-
-            -- Install static libraries.
-            forM_ staticWays $ \way -> do
-                rtsLib <- rtsLibffiLibrary stage way
-                copyFileUntracked (libffiPath -/- "inst/lib/libffi.a") rtsLib
-                produces [rtsLib]
-
-            -- Install dynamic libraries.
-            when (not $ null dynamicWays) $ do
-                -- Find dynamic libraries.
-                windows <- windowsHost
-                osx     <- osxHost
-                let libffiName'' = libffiName' windows True
-                (dynLibsSrcDir, dynLibFiles) <- if windows
-                    then do
-                        let libffiDll = "lib" ++ libffiName'' ++ ".dll"
-                        return (libffiPath -/- "inst/bin", [libffiDll])
-                    else do
-                        let libffiLibPath = libffiPath -/- "inst/lib"
-                        dynLibsRelative <- liftIO $ getDirectoryFilesIO
-                            libffiLibPath
-                            (if osx
-                                then ["lib" ++ libffiName'' ++ ".dylib*"]
-                                else ["lib" ++ libffiName'' ++ ".so*"])
-                        return (libffiLibPath, dynLibsRelative)
-
-                -- Install dynamic libraries.
-                rtsPath <- rtsBuildPath stage
-                forM_ dynLibFiles $ \dynLibFile -> do
-                    let target = rtsPath -/- dynLibFile
-                    copyFileUntracked (dynLibsSrcDir -/- dynLibFile) target
-
-                    -- On OSX the dylib's id must be updated to a relative path.
-                    when osx $ cmd
-                        [ "install_name_tool"
-                        , "-id", "@rpath/" ++ dynLibFile
-                        , target
-                        ]
-
-                    produces [target]
-
-            putSuccess "| Successfully bundled custom library 'libffi' with rts"
+
+        -- Note this build needs the Makefile, triggering the rules bellow.
+        build $ target context (Make libffiPath) [] []
+
+        -- Find dynamic libraries.
+        dynLibFiles <- do
+            windows <- windowsHost
+            osx     <- osxHost
+            let libffiName'' = libffiName' windows True
+            if windows
+                then
+                    let libffiDll = "lib" ++ libffiName'' ++ ".dll"
+                    in return [libffiPath -/- "inst/bin" -/- libffiDll]
+                else do
+                    let libffiLibPath = libffiPath -/- "inst/lib"
+                    dynLibsRelative <- liftIO $ getDirectoryFilesIO
+                        libffiLibPath
+                        (if osx
+                            then ["lib" ++ libffiName'' ++ ".dylib*"]
+                            else ["lib" ++ libffiName'' ++ ".so*"])
+                    return (fmap (libffiLibPath -/-) dynLibsRelative)
+
+        writeFileLines dynLibMan dynLibFiles
+        putSuccess "| Successfully build libffi."
 
     fmap (libffiPath -/-) ["Makefile.in", "configure" ] &%> \[mkIn, _] -> do
         -- Extract libffi tar file
diff --git a/hadrian/src/Rules/Library.hs b/hadrian/src/Rules/Library.hs
index 6340f4f962..aea855df11 100644
--- a/hadrian/src/Rules/Library.hs
+++ b/hadrian/src/Rules/Library.hs
@@ -1,4 +1,4 @@
-module Rules.Library (libraryRules) where
+module Rules.Library (libraryRules, needLibrary, libraryTargets) where
 
 import Hadrian.BuildPath
 import Hadrian.Haskell.Cabal
@@ -11,7 +11,7 @@ import Expression hiding (way, package)
 import Oracles.ModuleFiles
 import Packages
 import Rules.Gmp
-import Rules.Libffi (libffiDependencies)
+import Rules.Rts (needRtsLibffiTargets)
 import Target
 import Utilities
 
@@ -86,14 +86,6 @@ buildDynamicLibUnix root suffix dynlibpath = do
     let context = libDynContext dynlib
     deps <- contextDependencies context
     need =<< mapM pkgRegisteredLibraryFile deps
-
-    -- TODO should this be somewhere else?
-    -- Custom build step to generate libffi.so* in the rts build directory.
-    when (package context == rts) . interpretInContext context $ do
-        stage   <- getStage
-        rtsPath <- expr (rtsBuildPath stage)
-        expr $ need ((rtsPath -/-) <$> libffiDependencies)
-
     objs <- libraryObjects context
     build $ target context (Ghc LinkHs $ Context.stage context) objs [dynlibpath]
 
@@ -152,6 +144,32 @@ libraryObjects context@Context{..} = do
     need $ noHsObjs ++ hsObjs
     return (noHsObjs ++ hsObjs)
 
+-- | Return extra library targets.
+extraTargets :: Context -> Action [FilePath]
+extraTargets context
+    | package context == rts  = needRtsLibffiTargets (Context.stage context)
+    | otherwise               = return []
+
+-- | Given a library 'Package' this action computes all of its targets. Needing
+-- all the targets should build the library such that it is ready to be
+-- registered into the package database.
+-- See 'packageTargets' for the explanation of the @includeGhciLib@ parameter.
+libraryTargets :: Bool -> Context -> Action [FilePath]
+libraryTargets includeGhciLib context@Context {..} = do
+    libFile  <- pkgLibraryFile     context
+    ghciLib  <- pkgGhciLibraryFile context
+    ghci     <- if includeGhciLib && not (wayUnit Dynamic way)
+                then interpretInContext context $ getContextData buildGhciLib
+                else return False
+    extra    <- extraTargets context
+    return $ [ libFile ]
+          ++ [ ghciLib | ghci ]
+          ++ extra
+
+-- | Coarse-grain 'need': make sure all given libraries are fully built.
+needLibrary :: [Context] -> Action ()
+needLibrary cs = need =<< concatMapM (libraryTargets True) cs
+
 -- * Library paths types and parsers
 
 -- | > libHS<pkg name>-<pkg version>[_<way suffix>].a
diff --git a/hadrian/src/Rules/Program.hs b/hadrian/src/Rules/Program.hs
index bd4c4e358d..7efe6c42ae 100644
--- a/hadrian/src/Rules/Program.hs
+++ b/hadrian/src/Rules/Program.hs
@@ -14,6 +14,7 @@ import Settings
 import Settings.Default
 import Target
 import Utilities
+import Rules.Library
 
 -- | TODO: Drop code duplication
 buildProgramRules :: [(Resource, Int)] -> Rules ()
diff --git a/hadrian/src/Rules/Register.hs b/hadrian/src/Rules/Register.hs
index 39899738c1..700756eaad 100644
--- a/hadrian/src/Rules/Register.hs
+++ b/hadrian/src/Rules/Register.hs
@@ -12,6 +12,7 @@ import Rules.Rts
 import Settings
 import Target
 import Utilities
+import Rules.Library
 
 import Distribution.Version (Version)
 import qualified Distribution.Parsec as Cabal
@@ -109,8 +110,7 @@ buildConf _ context@Context {..} conf = do
         need [ path -/- "DerivedConstants.h"
              , path -/- "ghcautoconf.h"
              , path -/- "ghcplatform.h"
-             , path -/- "ghcversion.h"
-             , path -/- "ffi.h" ]
+             , path -/- "ghcversion.h" ]
 
     when (package == integerGmp) $ need [path -/- gmpLibraryH]
 
diff --git a/hadrian/src/Rules/Rts.hs b/hadrian/src/Rules/Rts.hs
index b7e3d49b53..b7f39609b9 100644
--- a/hadrian/src/Rules/Rts.hs
+++ b/hadrian/src/Rules/Rts.hs
@@ -1,16 +1,17 @@
-module Rules.Rts (rtsRules, needRtsSymLinks) where
+module Rules.Rts (rtsRules, needRtsLibffiTargets, needRtsSymLinks) where
 
-import Packages (rts)
+import Packages (rts, rtsBuildPath, libffiBuildPath, libffiLibraryName, rtsContext)
+import Rules.Libffi
 import Hadrian.Utilities
 import Settings.Builders.Common
 
--- | Dynamic RTS library files need symlinks without the dummy version number.
--- This is for backwards compatibility (the old make build system omitted the
--- dummy version number).
--- This rule has priority 3 to override the general rule for generating shared
+-- | This rule has priority 3 to override the general rule for generating shared
 -- library files (see Rules.Library.libraryRules).
 rtsRules :: Rules ()
 rtsRules = priority 3 $ do
+    -- Dynamic RTS library files need symlinks without the dummy version number.
+    -- This is for backwards compatibility (the old make build system omitted the
+    -- dummy version number).
     root <- buildRootRules
     [ root -/- "//libHSrts_*-ghc*.so",
       root -/- "//libHSrts_*-ghc*.dylib",
@@ -20,6 +21,129 @@ rtsRules = priority 3 $ do
             (addRtsDummyVersion $ takeFileName rtsLibFilePath')
             rtsLibFilePath'
 
+    -- Libffi
+    forM_ [Stage1 ..] $ \ stage -> do
+        let buildPath = root -/- buildDir (rtsContext stage)
+
+        -- Header files
+        (fmap (buildPath -/-) libffiHeaderFiles) &%> const (copyLibffiHeaders stage)
+
+        -- Static libraries.
+        buildPath -/- "libCffi*.a"     %> copyLibffiStatic stage
+
+        -- Dynamic libraries
+        buildPath -/- "libffi*.dylib*" %> copyLibffiDynamicUnix stage ".dylib"
+        buildPath -/- "libffi*.so*"    %> copyLibffiDynamicUnix stage ".so"
+        buildPath -/- "libffi*.dll*"   %> copyLibffiDynamicWin  stage
+
+withLibffi :: Stage -> (FilePath -> FilePath -> Action a) -> Action a
+withLibffi stage action = needLibffi stage
+                        >> (join $ action <$> libffiBuildPath stage
+                                          <*> rtsBuildPath    stage)
+
+-- | Copy all header files wither from the system libffi or from the libffi
+-- build dir to the rts build dir.
+copyLibffiHeaders :: Stage -> Action ()
+copyLibffiHeaders stage = do
+    rtsPath      <- rtsBuildPath stage
+    useSystemFfi <- flag UseSystemFfi
+    (fromStr, headers) <- if useSystemFfi
+        then ("system",) <$> libffiSystemHeaders
+        else needLibffi stage
+          >> ("custom",) <$> libffiHeaders stage
+    forM_ headers $ \ header -> copyFile header
+                                         (rtsPath -/- takeFileName header)
+    putSuccess $ "| Successfully copied " ++ fromStr ++ " FFI library header "
+                ++ "files to RTS build directory."
+
+-- | Copy a static library file from the libffi build dir to the rts build dir.
+copyLibffiStatic :: Stage -> FilePath -> Action ()
+copyLibffiStatic stage target = withLibffi stage $ \ libffiPath _ -> do
+    -- Copy the vanilla library, and symlink the rest to it.
+    vanillaLibFile <- rtsLibffiLibrary stage vanilla
+    if target == vanillaLibFile
+    then copyFile' (libffiPath -/- libffiLibrary) target
+    else createFileLink (takeFileName vanillaLibFile) target
+
+
+-- | Copy a dynamic library file from the libffi build dir to the rts build dir.
+copyLibffiDynamicUnix :: Stage -> String -> FilePath -> Action ()
+copyLibffiDynamicUnix stage libSuf target = do
+    needLibffi stage
+    dynLibs <- askLibffilDynLibs stage
+
+    -- If no version number suffix, then copy else just symlink.
+    let versionlessSourceFilePath = fromMaybe
+                (error $ "Needed " ++ show target ++ " which is not any of " ++
+                    "libffi's built shared libraries: " ++ show dynLibs)
+                (find (libSuf `isSuffixOf`) dynLibs)
+    let versionlessSourceFileName = takeFileName versionlessSourceFilePath
+    if versionlessSourceFileName == takeFileName target
+    then do
+        copyFile' versionlessSourceFilePath target
+
+        -- On OSX the dylib's id must be updated to a relative path.
+        osx <- osxHost
+        when osx $ cmd
+            [ "install_name_tool"
+            , "-id", "@rpath/" ++ takeFileName target
+            , target
+            ]
+    else createFileLink versionlessSourceFileName target
+
+-- | Copy a dynamic library file from the libffi build dir to the rts build dir.
+copyLibffiDynamicWin :: Stage -> FilePath -> Action ()
+copyLibffiDynamicWin stage target = do
+    needLibffi stage
+    dynLibs <- askLibffilDynLibs stage
+    let source = fromMaybe
+            (error $ "Needed " ++ show target ++ " which is not any of " ++
+                "libffi's built shared libraries: " ++ show dynLibs)
+            (find (\ lib -> takeFileName target == takeFileName lib) dynLibs)
+    copyFile' source target
+
+rtsLibffiLibrary :: Stage -> Way -> Action FilePath
+rtsLibffiLibrary stage way = do
+    name    <- libffiLibraryName
+    suf     <- libsuf stage way
+    rtsPath <- rtsBuildPath stage
+    return $ rtsPath -/- "lib" ++ name ++ suf
+
+-- | Get the libffi files bundled with the rts (header and library files).
+-- Unless using the system libffi, this needs the libffi library. It must be
+-- built before the targets can be calcuulated.
+needRtsLibffiTargets :: Stage -> Action [FilePath]
+needRtsLibffiTargets stage = do
+    rtsPath      <- rtsBuildPath stage
+    useSystemFfi <- flag UseSystemFfi
+
+    -- Header files (in the rts build dir).
+    let headers = fmap (rtsPath -/-) libffiHeaderFiles
+
+    if useSystemFfi
+    then return headers
+    else do
+        -- Need Libffi
+        -- This returns the dynamic library files (in the Libffi build dir).
+        needLibffi stage
+        dynLibffSource <- askLibffilDynLibs stage
+
+        -- Header files (in the rts build dir).
+        let headers = fmap (rtsPath -/-) libffiHeaderFiles
+
+        -- Dynamic library files (in the rts build dir).
+        let dynLibffis = fmap (\ lib -> rtsPath -/- takeFileName lib)
+                              dynLibffSource
+
+        -- Static Libffi files (in the rts build dir).
+        staticLibffis <- do
+            ways <- interpretInContext (stageContext stage)
+                                       (getLibraryWays <> getRtsWays)
+            let staticWays = filter (not . wayUnit Dynamic) ways
+            mapM (rtsLibffiLibrary stage) staticWays
+
+        return $ concat [ headers, dynLibffis, staticLibffis ]
+
 -- Need symlinks generated by rtsRules.
 needRtsSymLinks :: Stage -> [Way] -> Action ()
 needRtsSymLinks stage rtsWays
diff --git a/hadrian/src/Utilities.hs b/hadrian/src/Utilities.hs
index 2cc7a6e368..419d505bd8 100644
--- a/hadrian/src/Utilities.hs
+++ b/hadrian/src/Utilities.hs
@@ -2,7 +2,7 @@ module Utilities (
     build, buildWithResources, buildWithCmdOptions,
     askWithResources,
     runBuilder, runBuilderWith,
-    needLibrary, contextDependencies, stage1Dependencies, libraryTargets,
+    contextDependencies, stage1Dependencies,
     topsortPackages, cabalDependencies
     ) where
 
@@ -55,21 +55,6 @@ stage1Dependencies :: Package -> Action [Package]
 stage1Dependencies =
     fmap (map Context.package) . contextDependencies . vanillaContext Stage1
 
--- | Given a library 'Package' this action computes all of its targets. See
--- 'packageTargets' for the explanation of the @includeGhciLib@ parameter.
-libraryTargets :: Bool -> Context -> Action [FilePath]
-libraryTargets includeGhciLib context@Context {..} = do
-    libFile  <- pkgLibraryFile     context
-    ghciLib  <- pkgGhciLibraryFile context
-    ghci     <- if includeGhciLib && not (wayUnit Dynamic way)
-                then interpretInContext context $ getContextData buildGhciLib
-                else return False
-    return $ [ libFile ] ++ [ ghciLib | ghci ]
-
--- | Coarse-grain 'need': make sure all given libraries are fully built.
-needLibrary :: [Context] -> Action ()
-needLibrary cs = need =<< concatMapM (libraryTargets True) cs
-
 -- HACK (izgzhen), see https://github.com/snowleopard/hadrian/issues/344.
 -- | Topological sort of packages according to their dependencies.
 topsortPackages :: [Package] -> Action [Package]