main/DriverPipeline.hs

    {-# OPTIONS -fno-cse #-}
    {-# LANGUAGE NamedFieldPuns #-}
    -- -fno-cse is needed for GLOBAL_VAR's to behave properly

    -----------------------------------------------------------------------------
    --
    -- GHC Driver
    --
    -- (c) The University of Glasgow 2005
    --
    -----------------------------------------------------------------------------

    module DriverPipeline (
            -- Run a series of compilation steps in a pipeline, for a
            -- collection of source files.
       oneShot, compileFile,

            -- Interfaces for the batch-mode driver
       linkBinary,

            -- Interfaces for the compilation manager (interpreted/batch-mode)
       preprocess,
       compileOne, compileOne',
       link,

            -- Exports for hooks to override runPhase and link
       PhasePlus(..), CompPipeline(..), PipeEnv(..), PipeState(..),
       phaseOutputFilename, getPipeState, getPipeEnv,
       hscPostBackendPhase, getLocation, setModLocation, setDynFlags,
       runPhase, exeFileName,
       mkExtraObjToLinkIntoBinary, mkNoteObjsToLinkIntoBinary,
       maybeCreateManifest, runPhase_MoveBinary,
       linkingNeeded, checkLinkInfo
      ) where

    #include "HsVersions.h"

    import PipelineMonad
    import Packages
    import HeaderInfo
    import DriverPhases
    import SysTools
    import HscMain
    import Finder
    import HscTypes hiding ( Hsc )
    import Outputable
    import Module
    import UniqFM           ( eltsUFM )
    import ErrUtils
    import DynFlags
    import Config
    import Panic
    import Util
    import StringBuffer     ( hGetStringBuffer )
    import BasicTypes       ( SuccessFlag(..) )
    import Maybes           ( expectJust )
    import ParserCoreUtils  ( getCoreModuleName )
    import SrcLoc
    import FastString
    import LlvmCodeGen      ( llvmFixupAsm )
    import MonadUtils
    import Platform
    import TcRnTypes
    import Hooks

    import Exception
    import Data.IORef       ( readIORef )
    import System.Directory
    import System.FilePath
    import System.IO
    import Control.Monad
    import Data.List        ( isSuffixOf )
    import Data.Maybe
    import System.Environment
    import Data.Char

    -- ---------------------------------------------------------------------------
    -- Pre-process

    -- | Just preprocess a file, put the result in a temp. file (used by the
    -- compilation manager during the summary phase).
    --
    -- We return the augmented DynFlags, because they contain the result
    -- of slurping in the OPTIONS pragmas

    preprocess :: HscEnv
               -> (FilePath, Maybe Phase) -- ^ filename and starting phase
               -> IO (DynFlags, FilePath)
    preprocess hsc_env (filename, mb_phase) =
      ASSERT2(isJust mb_phase || isHaskellSrcFilename filename, text filename)
      runPipeline anyHsc hsc_env (filename, fmap RealPhase mb_phase)
            Nothing Temporary Nothing{-no ModLocation-} Nothing{-no stub-}

    -- ---------------------------------------------------------------------------

    -- | Compile
    --
    -- Compile a single module, under the control of the compilation manager.
    --
    -- This is the interface between the compilation manager and the
    -- compiler proper (hsc), where we deal with tedious details like
    -- reading the OPTIONS pragma from the source file, converting the
    -- C or assembly that GHC produces into an object file, and compiling
    -- FFI stub files.
    --
    -- NB.  No old interface can also mean that the source has changed.

    compileOne :: HscEnv
               -> ModSummary      -- ^ summary for module being compiled
               -> Int             -- ^ module N ...
               -> Int             -- ^ ... of M
               -> Maybe ModIface  -- ^ old interface, if we have one
               -> Maybe Linkable  -- ^ old linkable, if we have one
               -> SourceModified
               -> IO HomeModInfo   -- ^ the complete HomeModInfo, if successful

    compileOne = compileOne' Nothing (Just batchMsg)

    compileOne' :: Maybe TcGblEnv
                -> Maybe Messager
                -> HscEnv
                -> ModSummary      -- ^ summary for module being compiled
                -> Int             -- ^ module N ...
                -> Int             -- ^ ... of M
                -> Maybe ModIface  -- ^ old interface, if we have one
                -> Maybe Linkable  -- ^ old linkable, if we have one
                -> SourceModified
                -> IO HomeModInfo   -- ^ the complete HomeModInfo, if successful

    compileOne' m_tc_result mHscMessage
                hsc_env0 summary mod_index nmods mb_old_iface maybe_old_linkable
                source_modified0
     = do
       let dflags0     = ms_hspp_opts summary
           this_mod    = ms_mod summary
           src_flavour = ms_hsc_src summary
           location    = ms_location summary
           input_fn    = expectJust "compile:hs" (ml_hs_file location)
           input_fnpp  = ms_hspp_file summary
           mod_graph   = hsc_mod_graph hsc_env0
           needsTH     = any (xopt Opt_TemplateHaskell . ms_hspp_opts) mod_graph
           needsQQ     = any (xopt Opt_QuasiQuotes     . ms_hspp_opts) mod_graph
           needsLinker = needsTH || needsQQ
           isDynWay    = any (== WayDyn) (ways dflags0)
           isProfWay   = any (== WayProf) (ways dflags0)
       -- #8180 - when using TemplateHaskell, switch on -dynamic-too so
       -- the linker can correctly load the object files.
       let dflags1 = if needsLinker && dynamicGhc && not isDynWay && not isProfWay
                      then gopt_set dflags0 Opt_BuildDynamicToo
                      else dflags0

       debugTraceMsg dflags1 2 (text "compile: input file" <+> text input_fnpp)

       let basename = dropExtension input_fn

      -- We add the directory in which the .hs files resides) to the import path.
      -- This is needed when we try to compile the .hc file later, if it
      -- imports a _stub.h file that we created here.
       let current_dir = takeDirectory basename
           old_paths   = includePaths dflags1
           dflags      = dflags1 { includePaths = current_dir : old_paths }
           hsc_env     = hsc_env0 {hsc_dflags = dflags}

       -- Figure out what lang we're generating
       let hsc_lang = hscTarget dflags
       -- ... and what the next phase should be
       let next_phase = hscPostBackendPhase dflags src_flavour hsc_lang
       -- ... and what file to generate the output into
       output_fn <- getOutputFilename next_phase
                            Temporary basename dflags next_phase (Just location)

       let extCore_filename = basename ++ ".hcr"

       -- -fforce-recomp should also work with --make
       let force_recomp = gopt Opt_ForceRecomp dflags
           source_modified
             | force_recomp || isNothing maybe_old_linkable = SourceModified
             | otherwise = source_modified0
           object_filename = ml_obj_file location

       let always_do_basic_recompilation_check = case hsc_lang of
                                                 HscInterpreted -> True
                                                 _ -> False

       e <- genericHscCompileGetFrontendResult
                always_do_basic_recompilation_check
                m_tc_result mHscMessage
                hsc_env summary source_modified mb_old_iface (mod_index, nmods)

       case e of
           Left iface ->
               do details <- genModDetails hsc_env iface
                  MASSERT(isJust maybe_old_linkable)
                  return (HomeModInfo{ hm_details  = details,
                                       hm_iface    = iface,
                                       hm_linkable = maybe_old_linkable })

           Right (tc_result, mb_old_hash) ->
               -- run the compiler
               case hsc_lang of
                   HscInterpreted ->
                       case ms_hsc_src summary of
                       HsBootFile ->
                           do (iface, _changed, details) <- hscSimpleIface hsc_env tc_result mb_old_hash
                              return (HomeModInfo{ hm_details  = details,
                                                   hm_iface    = iface,
                                                   hm_linkable = maybe_old_linkable })
                       _ -> do guts0 <- hscDesugar hsc_env summary tc_result
                               guts <- hscSimplify hsc_env guts0
                               (iface, _changed, details, cgguts) <- hscNormalIface hsc_env extCore_filename guts mb_old_hash
                               (hasStub, comp_bc, modBreaks) <- hscInteractive hsc_env cgguts summary

                               stub_o <- case hasStub of
                                         Nothing -> return []
                                         Just stub_c -> do
                                             stub_o <- compileStub hsc_env stub_c
                                             return [DotO stub_o]

                               let hs_unlinked = [BCOs comp_bc modBreaks]
                                   unlinked_time = ms_hs_date summary
                                 -- Why do we use the timestamp of the source file here,
                                 -- rather than the current time?  This works better in
                                 -- the case where the local clock is out of sync
                                 -- with the filesystem's clock.  It's just as accurate:
                                 -- if the source is modified, then the linkable will
                                 -- be out of date.
                               let linkable = LM unlinked_time this_mod
                                              (hs_unlinked ++ stub_o)

                               return (HomeModInfo{ hm_details  = details,
                                                    hm_iface    = iface,
                                                    hm_linkable = Just linkable })
                   HscNothing ->
                       do (iface, _changed, details) <- hscSimpleIface hsc_env tc_result mb_old_hash
                          let linkable = if isHsBoot src_flavour
                                         then maybe_old_linkable
                                         else Just (LM (ms_hs_date summary) this_mod [])
                          return (HomeModInfo{ hm_details  = details,
                                               hm_iface    = iface,
                                               hm_linkable = linkable })

                   _ ->
                       case ms_hsc_src summary of
                       HsBootFile ->
                           do (iface, changed, details) <- hscSimpleIface hsc_env tc_result mb_old_hash
                              hscWriteIface dflags iface changed summary
                              touchObjectFile dflags object_filename
                              return (HomeModInfo{ hm_details  = details,
                                                   hm_iface    = iface,
                                                   hm_linkable = maybe_old_linkable })

                       _ -> do guts0 <- hscDesugar hsc_env summary tc_result
                               guts <- hscSimplify hsc_env guts0
                               (iface, changed, details, cgguts) <- hscNormalIface hsc_env extCore_filename guts mb_old_hash
                               hscWriteIface dflags iface changed summary

                               -- We're in --make mode: finish the compilation pipeline.
                               let mod_name = ms_mod_name summary
                               _ <- runPipeline StopLn hsc_env
                                                 (output_fn,
                                                  Just (HscOut src_flavour mod_name (HscRecomp cgguts summary)))
                                                 (Just basename)
                                                 Persistent
                                                 (Just location)
                                                 Nothing
                                     -- The object filename comes from the ModLocation
                               o_time <- getModificationUTCTime object_filename
                               let linkable = LM o_time this_mod [DotO object_filename]

                               return (HomeModInfo{ hm_details  = details,
                                                    hm_iface    = iface,
                                                    hm_linkable = Just linkable })

    -----------------------------------------------------------------------------
    -- stub .h and .c files (for foreign export support)

    -- The _stub.c file is derived from the haskell source file, possibly taking
    -- into account the -stubdir option.
    --
    -- The object file created by compiling the _stub.c file is put into a
    -- temporary file, which will be later combined with the main .o file
    -- (see the MergeStubs phase).

    compileStub :: HscEnv -> FilePath -> IO FilePath
    compileStub hsc_env stub_c = do
            (_, stub_o) <- runPipeline StopLn hsc_env (stub_c,Nothing)  Nothing
                                       Temporary Nothing{-no ModLocation-} Nothing

            return stub_o

    -- ---------------------------------------------------------------------------
    -- Link

    link :: GhcLink                 -- interactive or batch
         -> DynFlags                -- dynamic flags
         -> Bool                    -- attempt linking in batch mode?
         -> HomePackageTable        -- what to link
         -> IO SuccessFlag

    -- For the moment, in the batch linker, we don't bother to tell doLink
    -- which packages to link -- it just tries all that are available.
    -- batch_attempt_linking should only be *looked at* in batch mode.  It
    -- should only be True if the upsweep was successful and someone
    -- exports main, i.e., we have good reason to believe that linking
    -- will succeed.

    link ghcLink dflags
      = lookupHook linkHook l dflags ghcLink dflags
      where
        l LinkInMemory _ _ _
          = if cGhcWithInterpreter == "YES"
            then -- Not Linking...(demand linker will do the job)
                 return Succeeded
            else panicBadLink LinkInMemory

        l NoLink _ _ _
          = return Succeeded

        l LinkBinary dflags batch_attempt_linking hpt
          = link' dflags batch_attempt_linking hpt

        l LinkStaticLib dflags batch_attempt_linking hpt
          = link' dflags batch_attempt_linking hpt

        l LinkDynLib dflags batch_attempt_linking hpt
          = link' dflags batch_attempt_linking hpt

    panicBadLink :: GhcLink -> a
    panicBadLink other = panic ("link: GHC not built to link this way: " ++
                                show other)

    link' :: DynFlags                -- dynamic flags
          -> Bool                    -- attempt linking in batch mode?
          -> HomePackageTable        -- what to link
          -> IO SuccessFlag

    link' dflags batch_attempt_linking hpt
       | batch_attempt_linking
       = do
            let
                staticLink = case ghcLink dflags of
                              LinkStaticLib -> True
                              _ -> platformBinariesAreStaticLibs (targetPlatform dflags)

                home_mod_infos = eltsUFM hpt

                -- the packages we depend on
                pkg_deps  = concatMap (map fst . dep_pkgs . mi_deps . hm_iface) home_mod_infos

                -- the linkables to link
                linkables = map (expectJust "link".hm_linkable) home_mod_infos

            debugTraceMsg dflags 3 (text "link: linkables are ..." $$ vcat (map ppr linkables))

            -- check for the -no-link flag
            if isNoLink (ghcLink dflags)
              then do debugTraceMsg dflags 3 (text "link(batch): linking omitted (-c flag given).")
                      return Succeeded
              else do

            let getOfiles (LM _ _ us) = map nameOfObject (filter isObject us)
                obj_files = concatMap getOfiles linkables

                exe_file = exeFileName staticLink dflags

            linking_needed <- linkingNeeded dflags staticLink linkables pkg_deps

            if not (gopt Opt_ForceRecomp dflags) && not linking_needed
               then do debugTraceMsg dflags 2 (text exe_file <+> ptext (sLit "is up to date, linking not required."))
                       return Succeeded
               else do

            compilationProgressMsg dflags ("Linking " ++ exe_file ++ " ...")

            -- Don't showPass in Batch mode; doLink will do that for us.
            let link = case ghcLink dflags of
                    LinkBinary    -> linkBinary
                    LinkStaticLib -> linkStaticLibCheck
                    LinkDynLib    -> linkDynLibCheck
                    other         -> panicBadLink other
            link dflags obj_files pkg_deps

            debugTraceMsg dflags 3 (text "link: done")

            -- linkBinary only returns if it succeeds
            return Succeeded

       | otherwise
       = do debugTraceMsg dflags 3 (text "link(batch): upsweep (partially) failed OR" $$
                                    text "   Main.main not exported; not linking.")
            return Succeeded

    linkingNeeded :: DynFlags -> Bool -> [Linkable] -> [PackageId] -> IO Bool
    linkingNeeded dflags staticLink linkables pkg_deps = do
            -- if the modification time on the executable is later than the
            -- modification times on all of the objects and libraries, then omit
            -- linking (unless the -fforce-recomp flag was given).
      let exe_file = exeFileName staticLink dflags
      e_exe_time <- tryIO $ getModificationUTCTime exe_file
      case e_exe_time of
        Left _  -> return True
        Right t -> do
            -- first check object files and extra_ld_inputs
            let extra_ld_inputs = [ f | FileOption _ f <- ldInputs dflags ]
            e_extra_times <- mapM (tryIO . getModificationUTCTime) extra_ld_inputs
            let (errs,extra_times) = splitEithers e_extra_times
            let obj_times =  map linkableTime linkables ++ extra_times
            if not (null errs) || any (t <) obj_times
                then return True
                else do

            -- next, check libraries. XXX this only checks Haskell libraries,
            -- not extra_libraries or -l things from the command line.
            let pkg_map = pkgIdMap (pkgState dflags)
                pkg_hslibs  = [ (libraryDirs c, lib)
                              | Just c <- map (lookupPackage pkg_map) pkg_deps,
                                lib <- packageHsLibs dflags c ]

            pkg_libfiles <- mapM (uncurry (findHSLib dflags)) pkg_hslibs
            if any isNothing pkg_libfiles then return True else do
            e_lib_times <- mapM (tryIO . getModificationUTCTime)
                              (catMaybes pkg_libfiles)
            let (lib_errs,lib_times) = splitEithers e_lib_times
            if not (null lib_errs) || any (t <) lib_times
               then return True
               else checkLinkInfo dflags pkg_deps exe_file

    -- Returns 'False' if it was, and we can avoid linking, because the
    -- previous binary was linked with "the same options".
    checkLinkInfo :: DynFlags -> [PackageId] -> FilePath -> IO Bool
    checkLinkInfo dflags pkg_deps exe_file
     | not (platformSupportsSavingLinkOpts (platformOS (targetPlatform dflags)))
     -- ToDo: Windows and OS X do not use the ELF binary format, so
     -- readelf does not work there.  We need to find another way to do
     -- this.
     = return False -- conservatively we should return True, but not
                    -- linking in this case was the behaviour for a long
                    -- time so we leave it as-is.
     | otherwise
     = do
       link_info <- getLinkInfo dflags pkg_deps
       debugTraceMsg dflags 3 $ text ("Link info: " ++ link_info)
       m_exe_link_info <- readElfSection dflags ghcLinkInfoSectionName exe_file
       debugTraceMsg dflags 3 $ text ("Exe link info: " ++ show m_exe_link_info)
       return (Just link_info /= m_exe_link_info)

    platformSupportsSavingLinkOpts :: OS -> Bool
    platformSupportsSavingLinkOpts os
      | os == OSSolaris2 = False -- see #5382
      | otherwise        = osElfTarget os

    ghcLinkInfoSectionName :: String
    ghcLinkInfoSectionName = ".debug-ghc-link-info"
       -- if we use the ".debug" prefix, then strip will strip it by default

    findHSLib :: DynFlags -> [String] -> String -> IO (Maybe FilePath)
    findHSLib dflags dirs lib = do
      let batch_lib_file = if gopt Opt_Static dflags
                           then "lib" ++ lib <.> "a"
                           else mkSOName (targetPlatform dflags) lib
      found <- filterM doesFileExist (map (</> batch_lib_file) dirs)
      case found of
        [] -> return Nothing
        (x:_) -> return (Just x)

    -- -----------------------------------------------------------------------------
    -- Compile files in one-shot mode.

    oneShot :: HscEnv -> Phase -> [(String, Maybe Phase)] -> IO ()
    oneShot hsc_env stop_phase srcs = do
      o_files <- mapM (compileFile hsc_env stop_phase) srcs
      doLink (hsc_dflags hsc_env) stop_phase o_files

    compileFile :: HscEnv -> Phase -> (FilePath, Maybe Phase) -> IO FilePath
    compileFile hsc_env stop_phase (src, mb_phase) = do
       exists <- doesFileExist src
       when (not exists) $
            throwGhcExceptionIO (CmdLineError ("does not exist: " ++ src))

       let
            dflags    = hsc_dflags hsc_env
            split     = gopt Opt_SplitObjs dflags
            mb_o_file = outputFile dflags
            ghc_link  = ghcLink dflags      -- Set by -c or -no-link

            -- When linking, the -o argument refers to the linker's output.
            -- otherwise, we use it as the name for the pipeline's output.
            output
             -- If we are dong -fno-code, then act as if the output is
             -- 'Temporary'. This stops GHC trying to copy files to their
             -- final location.
             | HscNothing <- hscTarget dflags = Temporary
             | StopLn <- stop_phase, not (isNoLink ghc_link) = Persistent
                    -- -o foo applies to linker
             | isJust mb_o_file = SpecificFile
                    -- -o foo applies to the file we are compiling now
             | otherwise = Persistent

            stop_phase' = case stop_phase of
                            As _ | split -> SplitAs
                            _            -> stop_phase

       ( _, out_file) <- runPipeline stop_phase' hsc_env
                                (src, fmap RealPhase mb_phase) Nothing output
                                Nothing{-no ModLocation-} Nothing
       return out_file

    doLink :: DynFlags -> Phase -> [FilePath] -> IO ()
    doLink dflags stop_phase o_files
      | not (isStopLn stop_phase)
      = return ()           -- We stopped before the linking phase

      | otherwise
      = case ghcLink dflags of
            NoLink        -> return ()
            LinkBinary    -> linkBinary         dflags o_files []
            LinkStaticLib -> linkStaticLibCheck dflags o_files []
            LinkDynLib    -> linkDynLibCheck    dflags o_files []
            other         -> panicBadLink other

    -- ---------------------------------------------------------------------------

    -- | Run a compilation pipeline, consisting of multiple phases.
    --
    -- This is the interface to the compilation pipeline, which runs
    -- a series of compilation steps on a single source file, specifying
    -- at which stage to stop.
    --
    -- The DynFlags can be modified by phases in the pipeline (eg. by
    -- OPTIONS_GHC pragmas), and the changes affect later phases in the
    -- pipeline.
    runPipeline
      :: Phase                      -- ^ When to stop
      -> HscEnv                     -- ^ Compilation environment
      -> (FilePath,Maybe PhasePlus) -- ^ Input filename (and maybe -x suffix)
      -> Maybe FilePath             -- ^ original basename (if different from ^^^)
      -> PipelineOutput             -- ^ Output filename
      -> Maybe ModLocation          -- ^ A ModLocation, if this is a Haskell module
      -> Maybe FilePath             -- ^ stub object, if we have one
      -> IO (DynFlags, FilePath)    -- ^ (final flags, output filename)
    runPipeline stop_phase hsc_env0 (input_fn, mb_phase)
                 mb_basename output maybe_loc maybe_stub_o

        = do let
                 dflags0 = hsc_dflags hsc_env0

                 -- Decide where dump files should go based on the pipeline output
                 dflags = dflags0 { dumpPrefix = Just (basename ++ ".") }
                 hsc_env = hsc_env0 {hsc_dflags = dflags}

                 (input_basename, suffix) = splitExtension input_fn
                 suffix' = drop 1 suffix -- strip off the .
                 basename | Just b <- mb_basename = b
                          | otherwise             = input_basename

                 -- If we were given a -x flag, then use that phase to start from
                 start_phase = fromMaybe (RealPhase (startPhase suffix')) mb_phase

                 isHaskell (RealPhase (Unlit _)) = True
                 isHaskell (RealPhase (Cpp   _)) = True
                 isHaskell (RealPhase (HsPp  _)) = True
                 isHaskell (RealPhase (Hsc   _)) = True
                 isHaskell (HscOut {})           = True
                 isHaskell _                     = False

                 isHaskellishFile = isHaskell start_phase

                 env = PipeEnv{ pe_isHaskellishFile = isHaskellishFile,
                                stop_phase,
                                src_filename = input_fn,
                                src_basename = basename,
                                src_suffix = suffix',
                                output_spec = output }

             -- We want to catch cases of "you can't get there from here" before
             -- we start the pipeline, because otherwise it will just run off the
             -- end.
             --
             -- There is a partial ordering on phases, where A < B iff A occurs
             -- before B in a normal compilation pipeline.

             let happensBefore' = happensBefore dflags
             case start_phase of
                 RealPhase start_phase' ->
                     when (not (start_phase' `happensBefore'` stop_phase)) $
                           throwGhcExceptionIO (UsageError
                                       ("cannot compile this file to desired target: "
                                          ++ input_fn))
                 HscOut {} -> return ()

             debugTraceMsg dflags 4 (text "Running the pipeline")
             r <- runPipeline' start_phase hsc_env env input_fn
                               maybe_loc maybe_stub_o

             -- If we are compiling a Haskell module, and doing
             -- -dynamic-too, but couldn't do the -dynamic-too fast
             -- path, then rerun the pipeline for the dyn way
             let dflags = extractDynFlags hsc_env
             -- NB: Currently disabled on Windows (ref #7134, #8228, and #5987)
             when (not $ platformOS (targetPlatform dflags) == OSMinGW32) $ do
               when isHaskellishFile $ whenCannotGenerateDynamicToo dflags $ do
                   debugTraceMsg dflags 4
                       (text "Running the pipeline again for -dynamic-too")
                   let dflags' = dynamicTooMkDynamicDynFlags dflags
                   hsc_env' <- newHscEnv dflags'
                   _ <- runPipeline' start_phase hsc_env' env input_fn
                                     maybe_loc maybe_stub_o
                   return ()
             return r

    runPipeline'
      :: PhasePlus                  -- ^ When to start
      -> HscEnv                     -- ^ Compilation environment
      -> PipeEnv
      -> FilePath                   -- ^ Input filename
      -> Maybe ModLocation          -- ^ A ModLocation, if this is a Haskell module
      -> Maybe FilePath             -- ^ stub object, if we have one
      -> IO (DynFlags, FilePath)    -- ^ (final flags, output filename)
    runPipeline' start_phase hsc_env env input_fn
                 maybe_loc maybe_stub_o
      = do
      -- Execute the pipeline...
      let state = PipeState{ hsc_env, maybe_loc, maybe_stub_o = maybe_stub_o }

      evalP (pipeLoop start_phase input_fn) env state

    -- ---------------------------------------------------------------------------
    -- outer pipeline loop

    -- | pipeLoop runs phases until we reach the stop phase
    pipeLoop :: PhasePlus -> FilePath -> CompPipeline (DynFlags, FilePath)
    pipeLoop phase input_fn = do
      env <- getPipeEnv
      dflags <- getDynFlags
      let happensBefore' = happensBefore dflags
          stopPhase = stop_phase env
      case phase of
       RealPhase realPhase | realPhase `eqPhase` stopPhase            -- All done
         -> -- Sometimes, a compilation phase doesn't actually generate any output
            -- (eg. the CPP phase when -fcpp is not turned on).  If we end on this
            -- stage, but we wanted to keep the output, then we have to explicitly
            -- copy the file, remembering to prepend a {-# LINE #-} pragma so that
            -- further compilation stages can tell what the original filename was.
            case output_spec env of
            Temporary ->
                return (dflags, input_fn)
            output ->
                do pst <- getPipeState
                   final_fn <- liftIO $ getOutputFilename
                                            stopPhase output (src_basename env)
                                            dflags stopPhase (maybe_loc pst)
                   when (final_fn /= input_fn) $ do
                      let msg = ("Copying `" ++ input_fn ++"' to `" ++ final_fn ++ "'")
                          line_prag = Just ("{-# LINE 1 \"" ++ src_filename env ++ "\" #-}\n")
                      liftIO $ copyWithHeader dflags msg line_prag input_fn final_fn
                   return (dflags, final_fn)

         | not (realPhase `happensBefore'` stopPhase)
            -- Something has gone wrong.  We'll try to cover all the cases when
            -- this could happen, so if we reach here it is a panic.
            -- eg. it might happen if the -C flag is used on a source file that
            -- has {-# OPTIONS -fasm #-}.
         -> panic ("pipeLoop: at phase " ++ show realPhase ++
               " but I wanted to stop at phase " ++ show stopPhase)

       _
         -> do liftIO $ debugTraceMsg dflags 4
                                      (ptext (sLit "Running phase") <+> ppr phase)
               (next_phase, output_fn) <- runHookedPhase phase input_fn dflags
               r <- pipeLoop next_phase output_fn
               case phase of
                   HscOut {} ->
                       whenGeneratingDynamicToo dflags $ do
                           setDynFlags $ dynamicTooMkDynamicDynFlags dflags
                           -- TODO shouldn't ignore result:
                           _ <- pipeLoop phase input_fn
                           return ()
                   _ ->
                       return ()
               return r

    runHookedPhase :: PhasePlus -> FilePath -> DynFlags
                   -> CompPipeline (PhasePlus, FilePath)
    runHookedPhase pp input dflags =
      lookupHook runPhaseHook runPhase dflags pp input dflags

    -- -----------------------------------------------------------------------------
    -- In each phase, we need to know into what filename to generate the
    -- output.  All the logic about which filenames we generate output
    -- into is embodied in the following function.

    phaseOutputFilename :: Phase{-next phase-} -> CompPipeline FilePath
    phaseOutputFilename next_phase = do
      PipeEnv{stop_phase, src_basename, output_spec} <- getPipeEnv
      PipeState{maybe_loc, hsc_env} <- getPipeState
      let dflags = hsc_dflags hsc_env
      liftIO $ getOutputFilename stop_phase output_spec
                                 src_basename dflags next_phase maybe_loc

    getOutputFilename
      :: Phase -> PipelineOutput -> String
      -> DynFlags -> Phase{-next phase-} -> Maybe ModLocation -> IO FilePath
    getOutputFilename stop_phase output basename dflags next_phase maybe_location
     | is_last_phase, Persistent   <- output = persistent_fn
     | is_last_phase, SpecificFile <- output = case outputFile dflags of
                                               Just f -> return f
                                               Nothing ->
                                                   panic "SpecificFile: No filename"
     | keep_this_output                      = persistent_fn
     | otherwise                             = newTempName dflags suffix
        where
              hcsuf      = hcSuf dflags
              odir       = objectDir dflags
              osuf       = objectSuf dflags
              keep_hc    = gopt Opt_KeepHcFiles dflags
              keep_s     = gopt Opt_KeepSFiles dflags
              keep_bc    = gopt Opt_KeepLlvmFiles dflags

              myPhaseInputExt HCc       = hcsuf
              myPhaseInputExt MergeStub = osuf
              myPhaseInputExt StopLn    = osuf
              myPhaseInputExt other     = phaseInputExt other

              is_last_phase = next_phase `eqPhase` stop_phase

              -- sometimes, we keep output from intermediate stages
              keep_this_output =
                   case next_phase of
                           As _    | keep_s     -> True
                           LlvmOpt | keep_bc    -> True
                           HCc     | keep_hc    -> True
                           _other               -> False

              suffix = myPhaseInputExt next_phase

              -- persistent object files get put in odir
              persistent_fn
                 | StopLn <- next_phase = return odir_persistent
                 | otherwise            = return persistent

              persistent = basename <.> suffix

              odir_persistent
                 | Just loc <- maybe_location = ml_obj_file loc
                 | Just d <- odir = d </> persistent
                 | otherwise      = persistent

    -- -----------------------------------------------------------------------------
    -- | Each phase in the pipeline returns the next phase to execute, and the
    -- name of the file in which the output was placed.
    --
    -- We must do things dynamically this way, because we often don't know
    -- what the rest of the phases will be until part-way through the
    -- compilation: for example, an {-# OPTIONS -fasm #-} at the beginning
    -- of a source file can change the latter stages of the pipeline from
    -- taking the LLVM route to using the native code generator.
    --
    runPhase :: PhasePlus   -- ^ Run this phase
             -> FilePath    -- ^ name of the input file
             -> DynFlags    -- ^ for convenience, we pass the current dflags in
             -> CompPipeline (PhasePlus,           -- next phase to run
                              FilePath)            -- output filename

            -- Invariant: the output filename always contains the output
            -- Interesting case: Hsc when there is no recompilation to do
            --                   Then the output filename is still a .o file

    -------------------------------------------------------------------------------
    -- Unlit phase

    runPhase (RealPhase (Unlit sf)) input_fn dflags
      = do
           output_fn <- phaseOutputFilename (Cpp sf)

           let flags = [ -- The -h option passes the file name for unlit to
                         -- put in a #line directive
                         SysTools.Option     "-h"
                       , SysTools.Option $ escape $ normalise input_fn
                       , SysTools.FileOption "" input_fn
                       , SysTools.FileOption "" output_fn
                       ]

           liftIO $ SysTools.runUnlit dflags flags

           return (RealPhase (Cpp sf), output_fn)
      where
           -- escape the characters \, ", and ', but don't try to escape
           -- Unicode or anything else (so we don't use Util.charToC
           -- here).  If we get this wrong, then in
           -- Coverage.addTicksToBinds where we check that the filename in
           -- a SrcLoc is the same as the source filenaame, the two will
           -- look bogusly different. See test:
           -- libraries/hpc/tests/function/subdir/tough2.lhs
           escape ('\\':cs) = '\\':'\\': escape cs
           escape ('\"':cs) = '\\':'\"': escape cs
           escape ('\'':cs) = '\\':'\'': escape cs
           escape (c:cs)    = c : escape cs
           escape []        = []

    -------------------------------------------------------------------------------
    -- Cpp phase : (a) gets OPTIONS out of file
    --             (b) runs cpp if necessary

    runPhase (RealPhase (Cpp sf)) input_fn dflags0
      = do
           src_opts <- liftIO $ getOptionsFromFile dflags0 input_fn
           (dflags1, unhandled_flags, warns)
               <- liftIO $ parseDynamicFilePragma dflags0 src_opts
           setDynFlags dflags1
           liftIO $ checkProcessArgsResult dflags1 unhandled_flags

           if not (xopt Opt_Cpp dflags1) then do
               -- we have to be careful to emit warnings only once.
               unless (gopt Opt_Pp dflags1) $
                   liftIO $ handleFlagWarnings dflags1 warns

               -- no need to preprocess CPP, just pass input file along
               -- to the next phase of the pipeline.
               return (RealPhase (HsPp sf), input_fn)
            else do
                output_fn <- phaseOutputFilename (HsPp sf)
                liftIO $ doCpp dflags1 True{-raw-}
                               input_fn output_fn
                -- re-read the pragmas now that we've preprocessed the file
                -- See #2464,#3457
                src_opts <- liftIO $ getOptionsFromFile dflags0 output_fn
                (dflags2, unhandled_flags, warns)
                    <- liftIO $ parseDynamicFilePragma dflags0 src_opts
                liftIO $ checkProcessArgsResult dflags2 unhandled_flags
                unless (gopt Opt_Pp dflags2) $
                    liftIO $ handleFlagWarnings dflags2 warns
                -- the HsPp pass below will emit warnings

                setDynFlags dflags2

                return (RealPhase (HsPp sf), output_fn)

    -------------------------------------------------------------------------------
    -- HsPp phase

    runPhase (RealPhase (HsPp sf)) input_fn dflags
      = do
           if not (gopt Opt_Pp dflags) then
               -- no need to preprocess, just pass input file along
               -- to the next phase of the pipeline.
              return (RealPhase (Hsc sf), input_fn)
            else do
                PipeEnv{src_basename, src_suffix} <- getPipeEnv
                let orig_fn = src_basename <.> src_suffix
                output_fn <- phaseOutputFilename (Hsc sf)
                liftIO $ SysTools.runPp dflags
                               ( [ SysTools.Option     orig_fn
                                 , SysTools.Option     input_fn
                                 , SysTools.FileOption "" output_fn
                                 ]
                               )

                -- re-read pragmas now that we've parsed the file (see #3674)
                src_opts <- liftIO $ getOptionsFromFile dflags output_fn
                (dflags1, unhandled_flags, warns)
                    <- liftIO $ parseDynamicFilePragma dflags src_opts
                setDynFlags dflags1
                liftIO $ checkProcessArgsResult dflags1 unhandled_flags
                liftIO $ handleFlagWarnings dflags1 warns

                return (RealPhase (Hsc sf), output_fn)

    -----------------------------------------------------------------------------
    -- Hsc phase

    -- Compilation of a single module, in "legacy" mode (_not_ under
    -- the direction of the compilation manager).
    runPhase (RealPhase (Hsc src_flavour)) input_fn dflags0
     = do   -- normal Hsc mode, not mkdependHS

            PipeEnv{ stop_phase=stop,
                     src_basename=basename,
                     src_suffix=suff } <- getPipeEnv

      -- we add the current directory (i.e. the directory in which
      -- the .hs files resides) to the include path, since this is
      -- what gcc does, and it's probably what you want.
            let current_dir = takeDirectory basename
                paths = includePaths dflags0
                dflags = dflags0 { includePaths = current_dir : paths }

            setDynFlags dflags

      -- gather the imports and module name
            (hspp_buf,mod_name,imps,src_imps) <- liftIO $
                case src_flavour of
                    ExtCoreFile -> do  -- no explicit imports in ExtCore input.
                        m <- getCoreModuleName input_fn
                        return (Nothing, mkModuleName m, [], [])

                    _           -> do
                        buf <- hGetStringBuffer input_fn
                        (src_imps,imps,L _ mod_name) <- getImports dflags buf input_fn (basename <.> suff)
                        return (Just buf, mod_name, imps, src_imps)

      -- Take -o into account if present
      -- Very like -ohi, but we must *only* do this if we aren't linking
      -- (If we're linking then the -o applies to the linked thing, not to
      -- the object file for one module.)
      -- Note the nasty duplication with the same computation in compileFile above
            location <- getLocation src_flavour mod_name

            let o_file = ml_obj_file location -- The real object file

      -- Figure out if the source has changed, for recompilation avoidance.
      --
      -- Setting source_unchanged to True means that M.o seems
      -- to be up to date wrt M.hs; so no need to recompile unless imports have
      -- changed (which the compiler itself figures out).
      -- Setting source_unchanged to False tells the compiler that M.o is out of
      -- date wrt M.hs (or M.o doesn't exist) so we must recompile regardless.
            src_timestamp <- liftIO $ getModificationUTCTime (basename <.> suff)

            source_unchanged <- liftIO $
              if not (isStopLn stop)
                    -- SourceModified unconditionally if
                    --      (a) recompilation checker is off, or
                    --      (b) we aren't going all the way to .o file (e.g. ghc -S)
                 then return SourceModified
                    -- Otherwise look at file modification dates
                 else do o_file_exists <- doesFileExist o_file
                         if not o_file_exists
                            then return SourceModified       -- Need to recompile
                            else do t2 <- getModificationUTCTime o_file
                                    if t2 > src_timestamp
                                      then return SourceUnmodified
                                      else return SourceModified

            let extCore_filename = basename ++ ".hcr"

            PipeState{hsc_env=hsc_env'} <- getPipeState

      -- Tell the finder cache about this module
            mod <- liftIO $ addHomeModuleToFinder hsc_env' mod_name location

      -- Make the ModSummary to hand to hscMain
            let
                mod_summary = ModSummary {  ms_mod       = mod,
                                            ms_hsc_src   = src_flavour,
                                            ms_hspp_file = input_fn,
                                            ms_hspp_opts = dflags,
                                            ms_hspp_buf  = hspp_buf,
                                            ms_location  = location,
                                            ms_hs_date   = src_timestamp,
                                            ms_obj_date  = Nothing,
                                            ms_textual_imps = imps,
                                            ms_srcimps      = src_imps }

      -- run the compiler!
            result <- liftIO $ hscCompileOneShot hsc_env' extCore_filename
                                   mod_summary source_unchanged

            return (HscOut src_flavour mod_name result,
                    panic "HscOut doesn't have an input filename")

    runPhase (HscOut src_flavour mod_name result) _ dflags = do
            location <- getLocation src_flavour mod_name
            setModLocation location

            let o_file = ml_obj_file location -- The real object file
                hsc_lang = hscTarget dflags
                next_phase = hscPostBackendPhase dflags src_flavour hsc_lang

            case result of
                HscNotGeneratingCode ->
                    return (RealPhase next_phase,
                            panic "No output filename from Hsc when no-code")
                HscUpToDate ->
                    do liftIO $ touchObjectFile dflags o_file
                       -- The .o file must have a later modification date
                       -- than the source file (else we wouldn't get Nothing)
                       -- but we touch it anyway, to keep 'make' happy (we think).
                       return (RealPhase StopLn, o_file)
                HscUpdateBoot ->
                    do -- In the case of hs-boot files, generate a dummy .o-boot
                       -- stamp file for the benefit of Make
                       liftIO $ touchObjectFile dflags o_file
                       return (RealPhase next_phase, o_file)
                HscRecomp cgguts mod_summary
                  -> do output_fn <- phaseOutputFilename next_phase

                        PipeState{hsc_env=hsc_env'} <- getPipeState

                        (outputFilename, mStub) <- liftIO $ hscGenHardCode hsc_env' cgguts mod_summary output_fn
                        case mStub of
                            Nothing -> return ()
                            Just stub_c ->
                                do stub_o <- liftIO $ compileStub hsc_env' stub_c
                                   setStubO stub_o

                        return (RealPhase next_phase, outputFilename)

    -----------------------------------------------------------------------------
    -- Cmm phase

    runPhase (RealPhase CmmCpp) input_fn dflags
      = do
           output_fn <- phaseOutputFilename Cmm
           liftIO $ doCpp dflags False{-not raw-}
                          input_fn output_fn
           return (RealPhase Cmm, output_fn)

    runPhase (RealPhase Cmm) input_fn dflags
      = do
            let hsc_lang = hscTarget dflags

            let next_phase = hscPostBackendPhase dflags HsSrcFile hsc_lang

            output_fn <- phaseOutputFilename next_phase

            PipeState{hsc_env} <- getPipeState

            liftIO $ hscCompileCmmFile hsc_env input_fn output_fn

            return (RealPhase next_phase, output_fn)

    -----------------------------------------------------------------------------
    -- Cc phase

    -- we don't support preprocessing .c files (with -E) now.  Doing so introduces
    -- way too many hacks, and I can't say I've ever used it anyway.

    runPhase (RealPhase cc_phase) input_fn dflags
       | any (cc_phase `eqPhase`) [Cc, Ccpp, HCc, Cobjc, Cobjcpp]
       = do
            let platform = targetPlatform dflags
                hcc = cc_phase `eqPhase` HCc

            let cmdline_include_paths = includePaths dflags

            -- HC files have the dependent packages stamped into them
            pkgs <- if hcc then liftIO $ getHCFilePackages input_fn else return []

            -- add package include paths even if we're just compiling .c
            -- files; this is the Value Add(TM) that using ghc instead of
            -- gcc gives you :)
            pkg_include_dirs <- liftIO $ getPackageIncludePath dflags pkgs
            let include_paths = foldr (\ x xs -> ("-I" ++ x) : xs) []
                                  (cmdline_include_paths ++ pkg_include_dirs)

            let gcc_extra_viac_flags = extraGccViaCFlags dflags
            let pic_c_flags = picCCOpts dflags

            let verbFlags = getVerbFlags dflags

            -- cc-options are not passed when compiling .hc files.  Our
            -- hc code doesn't not #include any header files anyway, so these
            -- options aren't necessary.
            pkg_extra_cc_opts <- liftIO $
              if cc_phase `eqPhase` HCc
                 then return []
                 else getPackageExtraCcOpts dflags pkgs

            framework_paths <-
                if platformUsesFrameworks platform
                then do pkgFrameworkPaths <- liftIO $ getPackageFrameworkPath dflags pkgs
                        let cmdlineFrameworkPaths = frameworkPaths dflags
                        return $ map ("-F"++)
                                     (cmdlineFrameworkPaths ++ pkgFrameworkPaths)
                else return []

            let split_objs = gopt Opt_SplitObjs dflags
                split_opt | hcc && split_objs = [ "-DUSE_SPLIT_MARKERS" ]
                          | otherwise         = [ ]

            let cc_opt | optLevel dflags >= 2 = [ "-O2" ]
                       | optLevel dflags >= 1 = [ "-O" ]
                       | otherwise            = []

            -- Decide next phase
            let next_phase = As False
            output_fn <- phaseOutputFilename next_phase

            let
              more_hcc_opts =
                    -- on x86 the floating point regs have greater precision
                    -- than a double, which leads to unpredictable results.
                    -- By default, we turn this off with -ffloat-store unless
                    -- the user specified -fexcess-precision.
                    (if platformArch platform == ArchX86 &&
                        not (gopt Opt_ExcessPrecision dflags)
                            then [ "-ffloat-store" ]
                            else []) ++

                    -- gcc's -fstrict-aliasing allows two accesses to memory
                    -- to be considered non-aliasing if they have different types.
                    -- This interacts badly with the C code we generate, which is
                    -- very weakly typed, being derived from C--.
                    ["-fno-strict-aliasing"]

            let gcc_lang_opt | cc_phase `eqPhase` Ccpp    = "c++"
                             | cc_phase `eqPhase` Cobjc   = "objective-c"
                             | cc_phase `eqPhase` Cobjcpp = "objective-c++"
                             | otherwise                  = "c"
            liftIO $ SysTools.runCc dflags (
                    -- force the C compiler to interpret this file as C when
                    -- compiling .hc files, by adding the -x c option.
                    -- Also useful for plain .c files, just in case GHC saw a
                    -- -x c option.
                            [ SysTools.Option "-x", SysTools.Option gcc_lang_opt
                            , SysTools.FileOption "" input_fn
                            , SysTools.Option "-o"
                            , SysTools.FileOption "" output_fn
                            ]
                           ++ map SysTools.Option (
                              pic_c_flags

                    -- Stub files generated for foreign exports references the runIO_closure
                    -- and runNonIO_closure symbols, which are defined in the base package.
                    -- These symbols are imported into the stub.c file via RtsAPI.h, and the
                    -- way we do the import depends on whether we're currently compiling
                    -- the base package or not.
                           ++ (if platformOS platform == OSMinGW32 &&
                                  thisPackage dflags == basePackageId
                                    then [ "-DCOMPILING_BASE_PACKAGE" ]
                                    else [])

            -- We only support SparcV9 and better because V8 lacks an atomic CAS
            -- instruction. Note that the user can still override this
            -- (e.g., -mcpu=ultrasparc) as GCC picks the "best" -mcpu flag
            -- regardless of the ordering.
            --
            -- This is a temporary hack. See #2872, commit
            -- 5bd3072ac30216a505151601884ac88bf404c9f2
                           ++ (if platformArch platform == ArchSPARC
                               then ["-mcpu=v9"]
                               else [])

                           -- GCC 4.6+ doesn't like -Wimplicit when compiling C++.
                           ++ (if (cc_phase /= Ccpp && cc_phase /= Cobjcpp)
                                 then ["-Wimplicit"]
                                 else [])

                           ++ (if hcc
                                 then gcc_extra_viac_flags ++ more_hcc_opts
                                 else [])
                           ++ verbFlags
                           ++ [ "-S" ]
                           ++ cc_opt
                           ++ [ "-D__GLASGOW_HASKELL__="++cProjectVersionInt ]
                           ++ framework_paths
                           ++ split_opt
                           ++ include_paths
                           ++ pkg_extra_cc_opts
                           ))

            return (RealPhase next_phase, output_fn)

    -----------------------------------------------------------------------------
    -- Splitting phase

    runPhase (RealPhase Splitter) input_fn dflags
      = do  -- tmp_pfx is the prefix used for the split .s files

            split_s_prefix <- liftIO $ SysTools.newTempName dflags "split"
            let n_files_fn = split_s_prefix

            liftIO $ SysTools.runSplit dflags
                              [ SysTools.FileOption "" input_fn
                              , SysTools.FileOption "" split_s_prefix
                              , SysTools.FileOption "" n_files_fn
                              ]

            -- Save the number of split files for future references
            s <- liftIO $ readFile n_files_fn
            let n_files = read s :: Int
                dflags' = dflags { splitInfo = Just (split_s_prefix, n_files) }

            setDynFlags dflags'

            -- Remember to delete all these files
            liftIO $ addFilesToClean dflags'
                                     [ split_s_prefix ++ "__" ++ show n ++ ".s"
                                     | n <- [1..n_files]]

            return (RealPhase SplitAs,
                    "**splitter**") -- we don't use the filename in SplitAs

    -----------------------------------------------------------------------------
    -- As, SpitAs phase : Assembler

    -- This is for calling the assembler on a regular assembly file (not split).
    runPhase (RealPhase (As with_cpp)) input_fn dflags
      = do
            -- LLVM from version 3.0 onwards doesn't support the OS X system
            -- assembler, so we use clang as the assembler instead. (#5636)
            let whichAsProg | hscTarget dflags == HscLlvm &&
                              platformOS (targetPlatform dflags) == OSDarwin
                            = do
                                -- be careful what options we call clang with
                                -- see #5903 and #7617 for bugs caused by this.
                                llvmVer <- liftIO $ figureLlvmVersion dflags
                                return $ case llvmVer of
                                    Just n | n >= 30 -> SysTools.runClang
                                    _                -> SysTools.runAs

                            | otherwise = return SysTools.runAs

            as_prog <- whichAsProg
            let cmdline_include_paths = includePaths dflags

            next_phase <- maybeMergeStub
            output_fn <- phaseOutputFilename next_phase

            -- we create directories for the object file, because it
            -- might be a hierarchical module.
            liftIO $ createDirectoryIfMissing True (takeDirectory output_fn)

            ccInfo <- liftIO $ getCompilerInfo dflags
            let runAssembler inputFilename outputFilename
                    = liftIO $ as_prog dflags
                           ([ SysTools.Option ("-I" ++ p) | p <- cmdline_include_paths ]

            -- We only support SparcV9 and better because V8 lacks an atomic CAS
            -- instruction so we have to make sure that the assembler accepts the
            -- instruction set. Note that the user can still override this
            -- (e.g., -mcpu=ultrasparc). GCC picks the "best" -mcpu flag
            -- regardless of the ordering.
            --
            -- This is a temporary hack.
                           ++ (if platformArch (targetPlatform dflags) == ArchSPARC
                               then [SysTools.Option "-mcpu=v9"]
                               else [])
                           ++ (if any (ccInfo ==) [Clang, AppleClang, AppleClang51]
                                then [SysTools.Option "-Qunused-arguments"]
                                else [])
                           ++ [ SysTools.Option "-x"
                              , if with_cpp
                                  then SysTools.Option "assembler-with-cpp"
                                  else SysTools.Option "assembler"
                              , SysTools.Option "-c"
                              , SysTools.FileOption "" inputFilename
                              , SysTools.Option "-o"
                              , SysTools.FileOption "" outputFilename
                              ])

            liftIO $ debugTraceMsg dflags 4 (text "Running the assembler")
            runAssembler input_fn output_fn
            return (RealPhase next_phase, output_fn)

    -- This is for calling the assembler on a split assembly file (so a collection
    -- of assembly files)
    runPhase (RealPhase SplitAs) _input_fn dflags
      = do
            -- we'll handle the stub_o file in this phase, so don't MergeStub,
            -- just jump straight to StopLn afterwards.
            let next_phase = StopLn
            output_fn <- phaseOutputFilename next_phase

            let base_o = dropExtension output_fn
                osuf = objectSuf dflags
                split_odir  = base_o ++ "_" ++ osuf ++ "_split"

            -- this also creates the hierarchy
            liftIO $ createDirectoryIfMissing True split_odir

            -- remove M_split/ *.o, because we're going to archive M_split/ *.o
            -- later and we don't want to pick up any old objects.
            fs <- liftIO $ getDirectoryContents split_odir
            liftIO $ mapM_ removeFile $
                    map (split_odir </>) $ filter (osuf `isSuffixOf`) fs

            let (split_s_prefix, n) = case splitInfo dflags of
                                      Nothing -> panic "No split info"
                                      Just x -> x

            let split_s   n = split_s_prefix ++ "__" ++ show n <.> "s"

                split_obj :: Int -> FilePath
                split_obj n = split_odir </>
                              takeFileName base_o ++ "__" ++ show n <.> osuf

            let assemble_file n
                  = SysTools.runAs dflags (

            -- We only support SparcV9 and better because V8 lacks an atomic CAS
            -- instruction so we have to make sure that the assembler accepts the
            -- instruction set. Note that the user can still override this
            -- (e.g., -mcpu=ultrasparc). GCC picks the "best" -mcpu flag
            -- regardless of the ordering.
            --
            -- This is a temporary hack.
                              (if platformArch (targetPlatform dflags) == ArchSPARC
                               then [SysTools.Option "-mcpu=v9"]
                               else []) ++

                              [ SysTools.Option "-c"
                              , SysTools.Option "-o"
                              , SysTools.FileOption "" (split_obj n)
                              , SysTools.FileOption "" (split_s n)
                              ])

            liftIO $ mapM_ assemble_file [1..n]

            -- Note [pipeline-split-init]
            -- If we have a stub file, it may contain constructor
            -- functions for initialisation of this module.  We can't
            -- simply leave the stub as a separate object file, because it
            -- will never be linked in: nothing refers to it.  We need to
            -- ensure that if we ever refer to the data in this module
            -- that needs initialisation, then we also pull in the
            -- initialisation routine.
            --
            -- To that end, we make a DANGEROUS ASSUMPTION here: the data
            -- that needs to be initialised is all in the FIRST split
            -- object.  See Note [codegen-split-init].

            PipeState{maybe_stub_o} <- getPipeState
            case maybe_stub_o of
                Nothing     -> return ()
                Just stub_o -> liftIO $ do
                         tmp_split_1 <- newTempName dflags osuf
                         let split_1 = split_obj 1
                         copyFile split_1 tmp_split_1
                         removeFile split_1
                         joinObjectFiles dflags [tmp_split_1, stub_o] split_1

            -- join them into a single .o file
            liftIO $ joinObjectFiles dflags (map split_obj [1..n]) output_fn

            return (RealPhase next_phase, output_fn)

    -----------------------------------------------------------------------------
    -- LlvmOpt phase

    runPhase (RealPhase LlvmOpt) input_fn dflags
      = do
        ver <- liftIO $ readIORef (llvmVersion dflags)

        let opt_lvl  = max 0 (min 2 $ optLevel dflags)
            -- don't specify anything if user has specified commands. We do this
            -- for opt but not llc since opt is very specifically for optimisation
            -- passes only, so if the user is passing us extra options we assume
            -- they know what they are doing and don't get in the way.
            optFlag  = if null (getOpts dflags opt_lo)
                           then map SysTools.Option $ words (llvmOpts ver !! opt_lvl)
                           else []
            tbaa | ver < 29                 = "" -- no tbaa in 2.8 and earlier
                 | gopt Opt_LlvmTBAA dflags = "--enable-tbaa=true"
                 | otherwise                = "--enable-tbaa=false"

        output_fn <- phaseOutputFilename LlvmLlc

        liftIO $ SysTools.runLlvmOpt dflags
                   ([ SysTools.FileOption "" input_fn,
                        SysTools.Option "-o",
                        SysTools.FileOption "" output_fn]
                    ++ optFlag
                    ++ [SysTools.Option tbaa])

        return (RealPhase LlvmLlc, output_fn)
      where
            -- we always (unless -optlo specified) run Opt since we rely on it to
            -- fix up some pretty big deficiencies in the code we generate
            llvmOpts ver = [ "-mem2reg -globalopt"
                           , if ver >= 34 then "-O1 -globalopt" else "-O1"
                             -- LLVM 3.4 -O1 doesn't eliminate aliases reliably (bug #8855)
                           , "-O2"
                           ]

    -----------------------------------------------------------------------------
    -- LlvmLlc phase

    runPhase (RealPhase LlvmLlc) input_fn dflags
      = do
        ver <- liftIO $ readIORef (llvmVersion dflags)

        let opt_lvl = max 0 (min 2 $ optLevel dflags)
            -- iOS requires external references to be loaded indirectly from the
            -- DATA segment or dyld traps at runtime writing into TEXT: see #7722
            rmodel | platformOS (targetPlatform dflags) == OSiOS = "dynamic-no-pic"
                   | gopt Opt_PIC dflags                         = "pic"
                   | not (gopt Opt_Static dflags)                = "dynamic-no-pic"
                   | otherwise                                   = "static"
            tbaa | ver < 29                 = "" -- no tbaa in 2.8 and earlier
                 | gopt Opt_LlvmTBAA dflags = "--enable-tbaa=true"
                 | otherwise                = "--enable-tbaa=false"

        -- hidden debugging flag '-dno-llvm-mangler' to skip mangling
        let next_phase = case gopt Opt_NoLlvmMangler dflags of
                             False                            -> LlvmMangle
                             True | gopt Opt_SplitObjs dflags -> Splitter
                             True                             -> As False

        output_fn <- phaseOutputFilename next_phase

        liftIO $ SysTools.runLlvmLlc dflags
                    ([ SysTools.Option (llvmOpts !! opt_lvl),
                        SysTools.Option $ "-relocation-model=" ++ rmodel,
                        SysTools.FileOption "" input_fn,
                        SysTools.Option "-o", SysTools.FileOption "" output_fn]
                    ++ [SysTools.Option tbaa]
                    ++ map SysTools.Option fpOpts
                    ++ map SysTools.Option abiOpts
                    ++ map SysTools.Option sseOpts
                    ++ map SysTools.Option avxOpts
                    ++ map SysTools.Option avx512Opts
                    ++ map SysTools.Option stackAlignOpts)

        return (RealPhase next_phase, output_fn)
      where
            -- Bug in LLVM at O3 on OSX.
            llvmOpts = if platformOS (targetPlatform dflags) == OSDarwin
                       then ["-O1", "-O2", "-O2"]
                       else ["-O1", "-O2", "-O3"]
            -- On ARMv7 using LLVM, LLVM fails to allocate floating point registers
            -- while compiling GHC source code. It's probably due to fact that it
            -- does not enable VFP by default. Let's do this manually here
            fpOpts = case platformArch (targetPlatform dflags) of
                       ArchARM ARMv7 ext _ -> if (elem VFPv3 ext)
                                          then ["-mattr=+v7,+vfp3"]
                                          else if (elem VFPv3D16 ext)
                                               then ["-mattr=+v7,+vfp3,+d16"]
                                               else []
                       ArchARM ARMv6 ext _ -> if (elem VFPv2 ext)
                                              then ["-mattr=+v6,+vfp2"]
                                              else ["-mattr=+v6"]
                       _                 -> []
            -- On Ubuntu/Debian with ARM hard float ABI, LLVM's llc still
            -- compiles into soft-float ABI. We need to explicitly set abi
            -- to hard
            abiOpts = case platformArch (targetPlatform dflags) of
                        ArchARM _ _ HARD -> ["-float-abi=hard"]
                        ArchARM _ _ _    -> []
                        _                -> []

            sseOpts | isSse4_2Enabled dflags = ["-mattr=+sse42"]
                    | isSse2Enabled dflags   = ["-mattr=+sse2"]
                    | isSseEnabled dflags    = ["-mattr=+sse"]
                    | otherwise              = []

            avxOpts | isAvx512fEnabled dflags = ["-mattr=+avx512f"]
                    | isAvx2Enabled dflags    = ["-mattr=+avx2"]
                    | isAvxEnabled dflags     = ["-mattr=+avx"]
                    | otherwise               = []

            avx512Opts =
              [ "-mattr=+avx512cd" | isAvx512cdEnabled dflags ] ++
              [ "-mattr=+avx512er" | isAvx512erEnabled dflags ] ++
              [ "-mattr=+avx512pf" | isAvx512pfEnabled dflags ]

            stackAlignOpts =
                case platformArch (targetPlatform dflags) of
                  ArchX86_64 | isAvxEnabled dflags -> ["-stack-alignment=32"]
                  _                                -> []

    -----------------------------------------------------------------------------
    -- LlvmMangle phase

    runPhase (RealPhase LlvmMangle) input_fn dflags
      = do
          let next_phase = if gopt Opt_SplitObjs dflags then Splitter else As False
          output_fn <- phaseOutputFilename next_phase
          liftIO $ llvmFixupAsm dflags input_fn output_fn
          return (RealPhase next_phase, output_fn)

    -----------------------------------------------------------------------------
    -- merge in stub objects

    runPhase (RealPhase MergeStub) input_fn dflags
     = do
         PipeState{maybe_stub_o} <- getPipeState
         output_fn <- phaseOutputFilename StopLn
         liftIO $ createDirectoryIfMissing True (takeDirectory output_fn)
         case maybe_stub_o of
           Nothing ->
             panic "runPhase(MergeStub): no stub"
           Just stub_o -> do
             liftIO $ joinObjectFiles dflags [input_fn, stub_o] output_fn
             return (RealPhase StopLn, output_fn)

    -- warning suppression
    runPhase (RealPhase other) _input_fn _dflags =
       panic ("runPhase: don't know how to run phase " ++ show other)

    maybeMergeStub :: CompPipeline Phase
    maybeMergeStub
     = do
         PipeState{maybe_stub_o} <- getPipeState
         if isJust maybe_stub_o then return MergeStub else return StopLn

    getLocation :: HscSource -> ModuleName -> CompPipeline ModLocation
    getLocation src_flavour mod_name = do
        dflags <- getDynFlags

        PipeEnv{ src_basename=basename,
                 src_suffix=suff } <- getPipeEnv

        -- Build a ModLocation to pass to hscMain.
        -- The source filename is rather irrelevant by now, but it's used
        -- by hscMain for messages.  hscMain also needs
        -- the .hi and .o filenames, and this is as good a way
        -- as any to generate them, and better than most. (e.g. takes
        -- into account the -osuf flags)
        location1 <- liftIO $ mkHomeModLocation2 dflags mod_name basename suff

        -- Boot-ify it if necessary
        let location2 | isHsBoot src_flavour = addBootSuffixLocn location1
                      | otherwise            = location1

        -- Take -ohi into account if present
        -- This can't be done in mkHomeModuleLocation because
        -- it only applies to the module being compiles
        let ohi = outputHi dflags
            location3 | Just fn <- ohi = location2{ ml_hi_file = fn }
                      | otherwise      = location2

        -- Take -o into account if present
        -- Very like -ohi, but we must *only* do this if we aren't linking
        -- (If we're linking then the -o applies to the linked thing, not to
        -- the object file for one module.)
        -- Note the nasty duplication with the same computation in compileFile above
        let expl_o_file = outputFile dflags
            location4 | Just ofile <- expl_o_file
                      , isNoLink (ghcLink dflags)
                      = location3 { ml_obj_file = ofile }
                      | otherwise = location3

        return location4

    -----------------------------------------------------------------------------
    -- MoveBinary sort-of-phase
    -- After having produced a binary, move it somewhere else and generate a
    -- wrapper script calling the binary. Currently, we need this only in
    -- a parallel way (i.e. in GUM), because PVM expects the binary in a
    -- central directory.
    -- This is called from linkBinary below, after linking. I haven't made it
    -- a separate phase to minimise interfering with other modules, and
    -- we don't need the generality of a phase (MoveBinary is always
    -- done after linking and makes only sense in a parallel setup)   -- HWL

    runPhase_MoveBinary :: DynFlags -> FilePath -> IO Bool
    runPhase_MoveBinary dflags input_fn
        | WayPar `elem` ways dflags && not (gopt Opt_Static dflags) =
            panic ("Don't know how to combine PVM wrapper and dynamic wrapper")
        | WayPar `elem` ways dflags = do
            let sysMan = pgm_sysman dflags
            pvm_root <- getEnv "PVM_ROOT"
            pvm_arch <- getEnv "PVM_ARCH"
            let
               pvm_executable_base = "=" ++ input_fn
               pvm_executable = pvm_root ++ "/bin/" ++ pvm_arch ++ "/" ++ pvm_executable_base
            -- nuke old binary; maybe use configur'ed names for cp and rm?
            _ <- tryIO (removeFile pvm_executable)
            -- move the newly created binary into PVM land
            copy dflags "copying PVM executable" input_fn pvm_executable
            -- generate a wrapper script for running a parallel prg under PVM
            writeFile input_fn (mk_pvm_wrapper_script pvm_executable pvm_executable_base sysMan)
            return True
        | otherwise = return True

    mkExtraObj :: DynFlags -> Suffix -> String -> IO FilePath
    mkExtraObj dflags extn xs
     = do cFile <- newTempName dflags extn
          oFile <- newTempName dflags "o"
          writeFile cFile xs
          let rtsDetails = getPackageDetails (pkgState dflags) rtsPackageId
          SysTools.runCc dflags
                         ([Option        "-c",
                           FileOption "" cFile,
                           Option        "-o",
                           FileOption "" oFile]
                          ++ map (FileOption "-I") (includeDirs rtsDetails))
          return oFile

    -- When linking a binary, we need to create a C main() function that
    -- starts everything off.  This used to be compiled statically as part
    -- of the RTS, but that made it hard to change the -rtsopts setting,
    -- so now we generate and compile a main() stub as part of every
    -- binary and pass the -rtsopts setting directly to the RTS (#5373)
    --
    mkExtraObjToLinkIntoBinary :: DynFlags -> IO FilePath
    mkExtraObjToLinkIntoBinary dflags = do
       when (gopt Opt_NoHsMain dflags && haveRtsOptsFlags dflags) $ do
          log_action dflags dflags SevInfo noSrcSpan defaultUserStyle
              (text "Warning: -rtsopts and -with-rtsopts have no effect with -no-hs-main." $$
               text "    Call hs_init_ghc() from your main() function to set these options.")

       mkExtraObj dflags "c" (showSDoc dflags main)

      where
        main
          | gopt Opt_NoHsMain dflags = empty
          | otherwise = vcat [
                 ptext (sLit "#include \"Rts.h\""),
                 ptext (sLit "extern StgClosure ZCMain_main_closure;"),
                 ptext (sLit "int main(int argc, char *argv[])"),
                 char '{',
                 ptext (sLit "    RtsConfig __conf = defaultRtsConfig;"),
                 ptext (sLit "    __conf.rts_opts_enabled = ")
                     <> text (show (rtsOptsEnabled dflags)) <> semi,
                 case rtsOpts dflags of
                    Nothing   -> empty
                    Just opts -> ptext (sLit "    __conf.rts_opts= ") <>
                                   text (show opts) <> semi,
                 ptext (sLit "    __conf.rts_hs_main = rtsTrue;"),
                 ptext (sLit "    return hs_main(argc, argv, &ZCMain_main_closure,__conf);"),
                 char '}',
                 char '\n' -- final newline, to keep gcc happy
               ]

    -- Write out the link info section into a new assembly file. Previously
    -- this was included as inline assembly in the main.c file but this
    -- is pretty fragile. gas gets upset trying to calculate relative offsets
    -- that span the .note section (notably .text) when debug info is present
    mkNoteObjsToLinkIntoBinary :: DynFlags -> [PackageId] -> IO [FilePath]
    mkNoteObjsToLinkIntoBinary dflags dep_packages = do
       link_info <- getLinkInfo dflags dep_packages

       if (platformSupportsSavingLinkOpts (platformOS (targetPlatform dflags)))
         then fmap (:[]) $ mkExtraObj dflags "s" (showSDoc dflags (link_opts link_info))
         else return []

      where
        link_opts info = hcat [
              text "\t.section ", text ghcLinkInfoSectionName,
                                       text ",\"\",",
                                       text elfSectionNote,
                                       text "\n",

              text "\t.ascii \"", info', text "\"\n",

              -- ALL generated assembly must have this section to disable
              -- executable stacks.  See also
              -- compiler/nativeGen/AsmCodeGen.lhs for another instance
              -- where we need to do this.
              (if platformHasGnuNonexecStack (targetPlatform dflags)
               then text ".section .note.GNU-stack,\"\",@progbits\n"
               else empty)

               ]
              where
                info' = text $ escape info

                escape :: String -> String
                escape = concatMap (charToC.fromIntegral.ord)

                elfSectionNote :: String
                elfSectionNote = case platformArch (targetPlatform dflags) of
                                   ArchARM _ _ _ -> "%note"
                                   _             -> "@note"

    -- The "link info" is a string representing the parameters of the
    -- link.  We save this information in the binary, and the next time we
    -- link, if nothing else has changed, we use the link info stored in
    -- the existing binary to decide whether to re-link or not.
    getLinkInfo :: DynFlags -> [PackageId] -> IO String
    getLinkInfo dflags dep_packages = do
       package_link_opts <- getPackageLinkOpts dflags dep_packages
       pkg_frameworks <- if platformUsesFrameworks (targetPlatform dflags)
                         then getPackageFrameworks dflags dep_packages
                         else return []
       let extra_ld_inputs = ldInputs dflags
       let
          link_info = (package_link_opts,
                       pkg_frameworks,
                       rtsOpts dflags,
                       rtsOptsEnabled dflags,
                       gopt Opt_NoHsMain dflags,
                       map showOpt extra_ld_inputs,
                       getOpts dflags opt_l)
       --
       return (show link_info)

    -- generates a Perl skript starting a parallel prg under PVM
    mk_pvm_wrapper_script :: String -> String -> String -> String
    mk_pvm_wrapper_script pvm_executable pvm_executable_base sysMan = unlines $
     [
      "eval 'exec perl -S $0 ${1+\"$@\"}'",
      "  if $running_under_some_shell;",
      "# =!=!=!=!=!=!=!=!=!=!=!",
      "# This script is automatically generated: DO NOT EDIT!!!",
      "# Generated by Glasgow Haskell Compiler",
      "# ngoqvam choHbogh vaj' vIHoHnISbej !!!!",
      "#",
      "$pvm_executable      = '" ++ pvm_executable ++ "';",
      "$pvm_executable_base = '" ++ pvm_executable_base ++ "';",
      "$SysMan = '" ++ sysMan ++ "';",
      "",
      {- ToDo: add the magical shortcuts again iff we actually use them -- HWL
      "# first, some magical shortcuts to run "commands" on the binary",
      "# (which is hidden)",
      "if ($#ARGV == 1 && $ARGV[0] eq '+RTS' && $ARGV[1] =~ /^--((size|file|strip|rm|nm).*)/ ) {",
      "    local($cmd) = $1;",
      "    system("$cmd $pvm_executable");",
      "    exit(0); # all done",
      "}", -}
      "",
      "# Now, run the real binary; process the args first",
      "$ENV{'PE'} = $pvm_executable_base;", --  ++ pvm_executable_base,
      "$debug = '';",
      "$nprocessors = 0; # the default: as many PEs as machines in PVM config",
      "@nonPVM_args = ();",
      "$in_RTS_args = 0;",
      "",
      "args: while ($a = shift(@ARGV)) {",
      "    if ( $a eq '+RTS' ) {",
      "        $in_RTS_args = 1;",
      "    } elsif ( $a eq '-RTS' ) {",
      "        $in_RTS_args = 0;",
      "    }",
      "    if ( $a eq '-d' && $in_RTS_args ) {",
      "        $debug = '-';",
      "    } elsif ( $a =~ /^-qN(\\d+)/ && $in_RTS_args ) {",
      "        $nprocessors = $1;",
      "    } elsif ( $a =~ /^-qp(\\d+)/ && $in_RTS_args ) {",
      "        $nprocessors = $1;",
      "    } else {",
      "        push(@nonPVM_args, $a);",
      "    }",
      "}",
      "",
      "local($return_val) = 0;",
      "# Start the parallel execution by calling SysMan",
      "system(\"$SysMan $debug $pvm_executable $nprocessors @nonPVM_args\");",
      "$return_val = $?;",
      "# ToDo: fix race condition moving files and flushing them!!",
      "system(\"cp $ENV{'HOME'}/$pvm_executable_base.???.gr .\") if -f \"$ENV{'HOME'}/$pvm_executable_base.002.gr\";",
      "exit($return_val);"
     ]

    -----------------------------------------------------------------------------
    -- Look for the /* GHC_PACKAGES ... */ comment at the top of a .hc file

    getHCFilePackages :: FilePath -> IO [PackageId]
    getHCFilePackages filename =
      Exception.bracket (openFile filename ReadMode) hClose $ \h -> do
        l <- hGetLine h
        case l of
          '/':'*':' ':'G':'H':'C':'_':'P':'A':'C':'K':'A':'G':'E':'S':rest ->
              return (map stringToPackageId (words rest))
          _other ->
              return []

    -----------------------------------------------------------------------------
    -- Static linking, of .o files

    -- The list of packages passed to link is the list of packages on
    -- which this program depends, as discovered by the compilation
    -- manager.  It is combined with the list of packages that the user
    -- specifies on the command line with -package flags.
    --
    -- In one-shot linking mode, we can't discover the package
    -- dependencies (because we haven't actually done any compilation or
    -- read any interface files), so the user must explicitly specify all
    -- the packages.

    linkBinary :: DynFlags -> [FilePath] -> [PackageId] -> IO ()
    linkBinary = linkBinary' False

    linkBinary' :: Bool -> DynFlags -> [FilePath] -> [PackageId] -> IO ()
    linkBinary' staticLink dflags o_files dep_packages = do
        let platform = targetPlatform dflags
            mySettings = settings dflags
            verbFlags = getVerbFlags dflags
            output_fn = exeFileName staticLink dflags

        -- get the full list of packages to link with, by combining the
        -- explicit packages with the auto packages and all of their
        -- dependencies, and eliminating duplicates.

        full_output_fn <- if isAbsolute output_fn
                          then return output_fn
                          else do d <- getCurrentDirectory
                                  return $ normalise (d </> output_fn)
        pkg_lib_paths <- getPackageLibraryPath dflags dep_packages
        let pkg_lib_path_opts = concatMap get_pkg_lib_path_opts pkg_lib_paths
            get_pkg_lib_path_opts l
             | osElfTarget (platformOS platform) &&
               dynLibLoader dflags == SystemDependent &&
               not (gopt Opt_Static dflags)
                = let libpath = if gopt Opt_RelativeDynlibPaths dflags
                                then "$ORIGIN" </>
                                     (l `makeRelativeTo` full_output_fn)
                                else l
                      rpath = if gopt Opt_RPath dflags
                              then ["-Wl,-rpath",      "-Wl," ++ libpath]
                              else []
                      -- Solaris 11's linker does not support -rpath-link option. It silently
                      -- ignores it and then complains about next option which is -l<some
                      -- dir> as being a directory and not expected object file, E.g
                      -- ld: elf error: file
                      -- /tmp/ghc-src/libraries/base/dist-install/build:
                      -- elf_begin: I/O error: region read: Is a directory
                      rpathlink = if (platformOS platform) == OSSolaris2
                                  then []
                                  else ["-Wl,-rpath-link", "-Wl," ++ l]
                  in ["-L" ++ l] ++ rpathlink ++ rpath
             | osMachOTarget (platformOS platform) &&
               dynLibLoader dflags == SystemDependent &&
               not (gopt Opt_Static dflags) &&
               gopt Opt_RPath dflags
                = let libpath = if gopt Opt_RelativeDynlibPaths dflags
                                then "@loader_path" </>
                                     (l `makeRelativeTo` full_output_fn)
                                else l
                  in ["-L" ++ l] ++ ["-Wl,-rpath", "-Wl," ++ libpath]
             | otherwise = ["-L" ++ l]

        let lib_paths = libraryPaths dflags
        let lib_path_opts = map ("-L"++) lib_paths

        extraLinkObj <- mkExtraObjToLinkIntoBinary dflags
        noteLinkObjs <- mkNoteObjsToLinkIntoBinary dflags dep_packages

        pkg_link_opts <- do
            (package_hs_libs, extra_libs, other_flags) <- getPackageLinkOpts dflags dep_packages
            return $ if staticLink
                then package_hs_libs -- If building an executable really means making a static
                                     -- library (e.g. iOS), then we only keep the -l options for
                                     -- HS packages, because libtool doesn't accept other options.
                                     -- In the case of iOS these need to be added by hand to the
                                     -- final link in Xcode.
                else other_flags ++ package_hs_libs ++ extra_libs -- -Wl,-u,<sym> contained in other_flags
                                                                  -- needs to be put before -l<package>,
                                                                  -- otherwise Solaris linker fails linking
                                                                  -- a binary with unresolved symbols in RTS
                                                                  -- which are defined in base package
                                                                  -- the reason for this is a note in ld(1) about
                                                                  -- '-u' option: "The placement of this option
                                                                  -- on the command line is significant.
                                                                  -- This option must be placed before the library
                                                                  -- that defines the symbol."

        pkg_framework_path_opts <-
            if platformUsesFrameworks platform
            then do pkg_framework_paths <- getPackageFrameworkPath dflags dep_packages
                    return $ map ("-F" ++) pkg_framework_paths
            else return []

        framework_path_opts <-
            if platformUsesFrameworks platform
            then do let framework_paths = frameworkPaths dflags
                    return $ map ("-F" ++) framework_paths
            else return []

        pkg_framework_opts <-
            if platformUsesFrameworks platform
            then do pkg_frameworks <- getPackageFrameworks dflags dep_packages
                    return $ concat [ ["-framework", fw] | fw <- pkg_frameworks ]
            else return []

        framework_opts <-
            if platformUsesFrameworks platform
            then do let frameworks = cmdlineFrameworks dflags
                    -- reverse because they're added in reverse order from
                    -- the cmd line:
                    return $ concat [ ["-framework", fw]
                                    | fw <- reverse frameworks ]
            else return []

            -- probably _stub.o files
        let extra_ld_inputs = ldInputs dflags

        -- Here are some libs that need to be linked at the *end* of
        -- the command line, because they contain symbols that are referred to
        -- by the RTS.  We can't therefore use the ordinary way opts for these.
        let
            debug_opts | WayDebug `elem` ways dflags = [
    #if defined(HAVE_LIBBFD)
                            "-lbfd", "-liberty"
    #endif
                             ]
                       | otherwise            = []

        let thread_opts
             | WayThreaded `elem` ways dflags =
                let os = platformOS (targetPlatform dflags)
                in if os == OSOsf3 then ["-lpthread", "-lexc"]
                   else if os `elem` [OSMinGW32, OSFreeBSD, OSOpenBSD,
                                      OSNetBSD, OSHaiku, OSQNXNTO, OSiOS]
                   then []
                   else ["-lpthread"]
             | otherwise               = []

        rc_objs <- maybeCreateManifest dflags output_fn

        let link = if staticLink
                       then SysTools.runLibtool
                       else SysTools.runLink
        link dflags (
                           map SysTools.Option verbFlags
                          ++ [ SysTools.Option "-o"
                             , SysTools.FileOption "" output_fn
                             ]
                          ++ map SysTools.Option (
                             []

                          -- Permit the linker to auto link _symbol to _imp_symbol.
                          -- This lets us link against DLLs without needing an "import library".
                          ++ (if platformOS platform == OSMinGW32
                              then ["-Wl,--enable-auto-import"]
                              else [])

                          -- '-no_compact_unwind'
                          -- C++/Objective-C exceptions cannot use optimised
                          -- stack unwinding code. The optimised form is the
                          -- default in Xcode 4 on at least x86_64, and
                          -- without this flag we're also seeing warnings
                          -- like
                          --     ld: warning: could not create compact unwind for .LFB3: non-standard register 5 being saved in prolog
                          -- on x86.
                          ++ (if sLdSupportsCompactUnwind mySettings &&
                                 not staticLink &&
                                 (platformOS platform == OSDarwin || platformOS platform == OSiOS) &&
                                 case platformArch platform of
                                   ArchX86 -> True
                                   ArchX86_64 -> True
                                   ArchARM {} -> True
                                   _ -> False
                              then ["-Wl,-no_compact_unwind"]
                              else [])

                          -- '-no_pie'
                          -- iOS uses 'dynamic-no-pic', so we must pass this to ld to suppress a warning; see #7722
                          ++ (if platformOS platform == OSiOS &&
                                 not staticLink
                              then ["-Wl,-no_pie"]
                              else [])

                          -- '-Wl,-read_only_relocs,suppress'
                          -- ld gives loads of warnings like:
                          --     ld: warning: text reloc in _base_GHCziArr_unsafeArray_info to _base_GHCziArr_unsafeArray_closure
                          -- when linking any program. We're not sure
                          -- whether this is something we ought to fix, but
                          -- for now this flags silences them.
                          ++ (if platformOS   platform == OSDarwin &&
                                 platformArch platform == ArchX86 &&
                                 not staticLink
                              then ["-Wl,-read_only_relocs,suppress"]
                              else [])

                          ++ o_files
                          ++ lib_path_opts)
                          ++ extra_ld_inputs
                          ++ map SysTools.Option (
                             rc_objs
                          ++ framework_path_opts
                          ++ framework_opts
                          ++ pkg_lib_path_opts
                          ++ extraLinkObj:noteLinkObjs
                          ++ pkg_link_opts
                          ++ pkg_framework_path_opts
                          ++ pkg_framework_opts
                          ++ debug_opts
                          ++ thread_opts
                        ))

        -- parallel only: move binary to another dir -- HWL
        success <- runPhase_MoveBinary dflags output_fn
        unless success $
            throwGhcExceptionIO (InstallationError ("cannot move binary"))

    exeFileName :: Bool -> DynFlags -> FilePath
    exeFileName staticLink dflags
      | Just s <- outputFile dflags =
          case platformOS (targetPlatform dflags) of
              OSMinGW32 -> s <?.> "exe"
              _         -> if staticLink
                             then s <?.> "a"
                             else s
      | otherwise =
          if platformOS (targetPlatform dflags) == OSMinGW32
          then "main.exe"
          else if staticLink
               then "liba.a"
               else "a.out"
     where s <?.> ext | null (takeExtension s) = s <.> ext
                      | otherwise              = s

    maybeCreateManifest
       :: DynFlags
       -> FilePath                          -- filename of executable
       -> IO [FilePath]                     -- extra objects to embed, maybe
    maybeCreateManifest dflags exe_filename
     | platformOS (targetPlatform dflags) == OSMinGW32 &&
       gopt Opt_GenManifest dflags
        = do let manifest_filename = exe_filename <.> "manifest"

             writeFile manifest_filename $
                 "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>\n"++
                 "  <assembly xmlns=\"urn:schemas-microsoft-com:asm.v1\" manifestVersion=\"1.0\">\n"++
                 "  <assemblyIdentity version=\"1.0.0.0\"\n"++
                 "     processorArchitecture=\"X86\"\n"++
                 "     name=\"" ++ dropExtension exe_filename ++ "\"\n"++
                 "     type=\"win32\"/>\n\n"++
                 "  <trustInfo xmlns=\"urn:schemas-microsoft-com:asm.v3\">\n"++
                 "    <security>\n"++
                 "      <requestedPrivileges>\n"++
                 "        <requestedExecutionLevel level=\"asInvoker\" uiAccess=\"false\"/>\n"++
                 "        </requestedPrivileges>\n"++
                 "       </security>\n"++
                 "  </trustInfo>\n"++
                 "</assembly>\n"

             -- Windows will find the manifest file if it is named
             -- foo.exe.manifest. However, for extra robustness, and so that
             -- we can move the binary around, we can embed the manifest in
             -- the binary itself using windres:
             if not (gopt Opt_EmbedManifest dflags) then return [] else do

             rc_filename <- newTempName dflags "rc"
             rc_obj_filename <- newTempName dflags (objectSuf dflags)

             writeFile rc_filename $
                 "1 24 MOVEABLE PURE " ++ show manifest_filename ++ "\n"
                   -- magic numbers :-)
                   -- show is a bit hackish above, but we need to escape the
                   -- backslashes in the path.

             runWindres dflags $ map SysTools.Option $
                   ["--input="++rc_filename,
                    "--output="++rc_obj_filename,
                    "--output-format=coff"]
                   -- no FileOptions here: windres doesn't like seeing
                   -- backslashes, apparently

             removeFile manifest_filename

             return [rc_obj_filename]
     | otherwise = return []

    linkDynLibCheck :: DynFlags -> [String] -> [PackageId] -> IO ()
    linkDynLibCheck dflags o_files dep_packages
     = do
        when (haveRtsOptsFlags dflags) $ do
          log_action dflags dflags SevInfo noSrcSpan defaultUserStyle
              (text "Warning: -rtsopts and -with-rtsopts have no effect with -shared." $$
               text "    Call hs_init_ghc() from your main() function to set these options.")

        linkDynLib dflags o_files dep_packages

    linkStaticLibCheck :: DynFlags -> [String] -> [PackageId] -> IO ()
    linkStaticLibCheck dflags o_files dep_packages
     = do
        when (platformOS (targetPlatform dflags) `notElem` [OSiOS, OSDarwin]) $
          throwGhcExceptionIO (ProgramError "Static archive creation only supported on Darwin/OS X/iOS")
        linkBinary' True dflags o_files dep_packages

    -- -----------------------------------------------------------------------------
    -- Running CPP

    doCpp :: DynFlags -> Bool -> FilePath -> FilePath -> IO ()
    doCpp dflags raw input_fn output_fn = do
        let hscpp_opts = picPOpts dflags
        let cmdline_include_paths = includePaths dflags

        pkg_include_dirs <- getPackageIncludePath dflags []
        let include_paths = foldr (\ x xs -> "-I" : x : xs) []
                              (cmdline_include_paths ++ pkg_include_dirs)

        let verbFlags = getVerbFlags dflags

        let cpp_prog args | raw       = SysTools.runCpp dflags args
                          | otherwise = SysTools.runCc dflags (SysTools.Option "-E" : args)

        let target_defs =
              [ "-D" ++ HOST_OS     ++ "_BUILD_OS=1",
                "-D" ++ HOST_ARCH   ++ "_BUILD_ARCH=1",
                "-D" ++ TARGET_OS   ++ "_HOST_OS=1",
                "-D" ++ TARGET_ARCH ++ "_HOST_ARCH=1" ]
            -- remember, in code we *compile*, the HOST is the same our TARGET,
            -- and BUILD is the same as our HOST.

        let sse_defs =
              [ "-D__SSE__=1"    | isSseEnabled    dflags ] ++
              [ "-D__SSE2__=1"   | isSse2Enabled   dflags ] ++
              [ "-D__SSE4_2__=1" | isSse4_2Enabled dflags ]

        let avx_defs =
              [ "-D__AVX__=1"  | isAvxEnabled  dflags ] ++
              [ "-D__AVX2__=1" | isAvx2Enabled dflags ] ++
              [ "-D__AVX512CD__=1" | isAvx512cdEnabled dflags ] ++
              [ "-D__AVX512ER__=1" | isAvx512erEnabled dflags ] ++
              [ "-D__AVX512F__=1"  | isAvx512fEnabled  dflags ] ++
              [ "-D__AVX512PF__=1" | isAvx512pfEnabled dflags ]

        backend_defs <- getBackendDefs dflags

        cpp_prog       (   map SysTools.Option verbFlags
                        ++ map SysTools.Option include_paths
                        ++ map SysTools.Option hsSourceCppOpts
                        ++ map SysTools.Option target_defs
                        ++ map SysTools.Option backend_defs
                        ++ map SysTools.Option hscpp_opts
                        ++ map SysTools.Option sse_defs
                        ++ map SysTools.Option avx_defs
            -- Set the language mode to assembler-with-cpp when preprocessing. This
            -- alleviates some of the C99 macro rules relating to whitespace and the hash
            -- operator, which we tend to abuse. Clang in particular is not very happy
            -- about this.
                        ++ [ SysTools.Option     "-x"
                           , SysTools.Option     "assembler-with-cpp"
                           , SysTools.Option     input_fn
            -- We hackily use Option instead of FileOption here, so that the file
            -- name is not back-slashed on Windows.  cpp is capable of
            -- dealing with / in filenames, so it works fine.  Furthermore
            -- if we put in backslashes, cpp outputs #line directives
            -- with *double* backslashes.   And that in turn means that
            -- our error messages get double backslashes in them.
            -- In due course we should arrange that the lexer deals
            -- with these \\ escapes properly.
                           , SysTools.Option     "-o"
                           , SysTools.FileOption "" output_fn
                           ])

    getBackendDefs :: DynFlags -> IO [String]
    getBackendDefs dflags | hscTarget dflags == HscLlvm = do
        llvmVer <- figureLlvmVersion dflags
        return $ case llvmVer of
                   Just n -> [ "-D__GLASGOW_HASKELL_LLVM__="++show n ]
                   _      -> []

    getBackendDefs _ =
        return []

    hsSourceCppOpts :: [String]
    -- Default CPP defines in Haskell source
    hsSourceCppOpts =
            [ "-D__GLASGOW_HASKELL__="++cProjectVersionInt ]

    -- ---------------------------------------------------------------------------
    -- join object files into a single relocatable object file, using ld -r

    joinObjectFiles :: DynFlags -> [FilePath] -> FilePath -> IO ()
    joinObjectFiles dflags o_files output_fn = do
      let mySettings = settings dflags
          ldIsGnuLd = sLdIsGnuLd mySettings
          osInfo = platformOS (targetPlatform dflags)
          ld_r args cc = SysTools.runLink dflags ([
                           SysTools.Option "-nostdlib",
                           SysTools.Option "-Wl,-r"
                         ]
                         ++ (if any (cc ==) [Clang, AppleClang, AppleClang51]
                              then []
                              else [SysTools.Option "-nodefaultlibs"])
                         ++ (if osInfo == OSFreeBSD
                              then [SysTools.Option "-L/usr/lib"]
                              else [])
                            -- gcc on sparc sets -Wl,--relax implicitly, but
                            -- -r and --relax are incompatible for ld, so
                            -- disable --relax explicitly.
                         ++ (if platformArch (targetPlatform dflags) == ArchSPARC
                             && ldIsGnuLd
                                then [SysTools.Option "-Wl,-no-relax"]
                                else [])
                         ++ map SysTools.Option ld_build_id
                         ++ [ SysTools.Option "-o",
                              SysTools.FileOption "" output_fn ]
                         ++ args)

          -- suppress the generation of the .note.gnu.build-id section,
          -- which we don't need and sometimes causes ld to emit a
          -- warning:
          ld_build_id | sLdSupportsBuildId mySettings = ["-Wl,--build-id=none"]
                      | otherwise                     = []

      ccInfo <- getCompilerInfo dflags
      if ldIsGnuLd
         then do
              script <- newTempName dflags "ldscript"
              writeFile script $ "INPUT(" ++ unwords o_files ++ ")"
              ld_r [SysTools.FileOption "" script] ccInfo
         else if sLdSupportsFilelist mySettings
         then do
              filelist <- newTempName dflags "filelist"
              writeFile filelist $ unlines o_files
              ld_r [SysTools.Option "-Wl,-filelist",
                    SysTools.FileOption "-Wl," filelist] ccInfo
         else do
              ld_r (map (SysTools.FileOption "") o_files) ccInfo

    -- -----------------------------------------------------------------------------
    -- Misc.

    -- | What phase to run after one of the backend code generators has run
    hscPostBackendPhase :: DynFlags -> HscSource -> HscTarget -> Phase
    hscPostBackendPhase _ HsBootFile _    =  StopLn
    hscPostBackendPhase dflags _ hsc_lang =
      case hsc_lang of
            HscC -> HCc
            HscAsm | gopt Opt_SplitObjs dflags -> Splitter
                   | otherwise                 -> As False
            HscLlvm        -> LlvmOpt
            HscNothing     -> StopLn
            HscInterpreted -> StopLn

    touchObjectFile :: DynFlags -> FilePath -> IO ()
    touchObjectFile dflags path = do
      createDirectoryIfMissing True $ takeDirectory path
      SysTools.touch dflags "Touching object file" path

    haveRtsOptsFlags :: DynFlags -> Bool
    haveRtsOptsFlags dflags =
             isJust (rtsOpts dflags) || case rtsOptsEnabled dflags of
                                            RtsOptsSafeOnly -> False
                                            _ -> True