Break up `Settings` into smaller structs

As far as I can tell, the fields within `Settings` aren't *intrinsicly*
related. They just happen to be initialized the same way (in particular
prior to the rest of `DynFlags`), and that is why they are grouped
together.

Within `Settings`, however, there are groups of settings that clearly do
share something in common, regardless of how they anything is
initialized.

In the spirit of GHC being a library, where the end cosumer may choose
to initialize this configuration in arbitrary ways, I made some new data
types for thoses groups internal to `Settings`, and used them to define
`Settings` instead. Hopefully this is a baby step towards a general
decoupling of the stateful and stateless parts of GHC.

9 files changed, 541 insertions, 190 deletions

diff --git a/compiler/ghc.cabal.in b/compiler/ghc.cabal.in
index 38ef67d495..e2d789b172 100644
--- a/compiler/ghc.cabal.in
+++ b/compiler/ghc.cabal.in
@@ -272,7 +272,10 @@ Library
         CmmType
         CmmUtils
         CmmLayoutStack
+        CliOption
         EnumSet
+        GhcNameVersion
+        FileSettings
         MkGraph
         PprBase
         PprC
@@ -395,6 +398,7 @@ Library
         Plugins
         TcPluginM
         PprTyThing
+        Settings
         StaticPtrTable
         SysTools
         SysTools.BaseDir
@@ -418,6 +422,7 @@ Library
         PrelNames
         PrelRules
         PrimOp
+        ToolSettings
         TysPrim
         TysWiredIn
         CostCentre
diff --git a/compiler/main/CliOption.hs b/compiler/main/CliOption.hs
new file mode 100644
index 0000000000..d42c5b4900
--- /dev/null
+++ b/compiler/main/CliOption.hs
@@ -0,0 +1,27 @@
+module CliOption
+  ( Option (..)
+  , showOpt
+  ) where
+
+import GhcPrelude
+
+-- -----------------------------------------------------------------------------
+-- Command-line options
+
+-- | When invoking external tools as part of the compilation pipeline, we
+-- pass these a sequence of options on the command-line. Rather than
+-- just using a list of Strings, we use a type that allows us to distinguish
+-- between filepaths and 'other stuff'. The reason for this is that
+-- this type gives us a handle on transforming filenames, and filenames only,
+-- to whatever format they're expected to be on a particular platform.
+data Option
+ = FileOption -- an entry that _contains_ filename(s) / filepaths.
+              String  -- a non-filepath prefix that shouldn't be
+                      -- transformed (e.g., "/out=")
+              String  -- the filepath/filename portion
+ | Option     String
+ deriving ( Eq )
+
+showOpt :: Option -> String
+showOpt (FileOption pre f) = pre ++ f
+showOpt (Option s)  = s
diff --git a/compiler/main/DynFlags.hs b/compiler/main/DynFlags.hs
index 15f254ad7c..1f0fb2f7ef 100644
--- a/compiler/main/DynFlags.hs
+++ b/compiler/main/DynFlags.hs
@@ -87,7 +87,66 @@ module DynFlags (
 
         -- ** System tool settings and locations
         Settings(..),
+        sProgramName,
+        sProjectVersion,
+        sGhcUsagePath,
+        sGhciUsagePath,
+        sToolDir,
+        sTopDir,
+        sTmpDir,
+        sSystemPackageConfig,
+        sLdSupportsCompactUnwind,
+        sLdSupportsBuildId,
+        sLdSupportsFilelist,
+        sLdIsGnuLd,
+        sGccSupportsNoPie,
+        sPgm_L,
+        sPgm_P,
+        sPgm_F,
+        sPgm_c,
+        sPgm_a,
+        sPgm_l,
+        sPgm_dll,
+        sPgm_T,
+        sPgm_windres,
+        sPgm_libtool,
+        sPgm_ar,
+        sPgm_ranlib,
+        sPgm_lo,
+        sPgm_lc,
+        sPgm_lcc,
+        sPgm_i,
+        sOpt_L,
+        sOpt_P,
+        sOpt_P_fingerprint,
+        sOpt_F,
+        sOpt_c,
+        sOpt_cxx,
+        sOpt_a,
+        sOpt_l,
+        sOpt_windres,
+        sOpt_lo,
+        sOpt_lc,
+        sOpt_lcc,
+        sOpt_i,
+        sExtraGccViaCFlags,
+        sTargetPlatformString,
+        sIntegerLibrary,
+        sIntegerLibraryType,
+        sGhcWithInterpreter,
+        sGhcWithNativeCodeGen,
+        sGhcWithSMP,
+        sGhcRTSWays,
+        sTablesNextToCode,
+        sLeadingUnderscore,
+        sLibFFI,
+        sGhcThreaded,
+        sGhcDebugged,
+        sGhcRtsWithLibdw,
         IntegerLibrary(..),
+        GhcNameVersion(..),
+        FileSettings(..),
+        PlatformMisc(..),
         targetPlatform, programName, projectVersion,
         ghcUsagePath, ghciUsagePath, topDir, tmpDir, rawSettings,
         versionedAppDir,
@@ -198,9 +257,11 @@ import {-# SOURCE #-} PrelNames ( mAIN )
 import {-# SOURCE #-} Packages (PackageState, emptyPackageState)
 import DriverPhases     ( Phase(..), phaseInputExt )
 import Config
+import CliOption
 import CmdLineParser hiding (WarnReason(..))
 import qualified CmdLineParser as Cmd
 import Constants
+import GhcNameVersion
 import Panic
 import qualified PprColour as Col
 import Util
@@ -211,7 +272,11 @@ import SrcLoc
 import BasicTypes       ( Alignment, alignmentOf, IntWithInf, treatZeroAsInf )
 import FastString
 import Fingerprint
+import FileSettings
 import Outputable
+import Settings
+import ToolSettings
+
 import Foreign.C        ( CInt(..) )
 import System.IO.Unsafe ( unsafeDupablePerformIO )
 import {-# SOURCE #-} ErrUtils ( Severity(..), MsgDoc, mkLocMessageAnn
@@ -1304,80 +1369,8 @@ type LlvmTargets = [(String, LlvmTarget)]
 type LlvmPasses = [(Int, String)]
 type LlvmConfig = (LlvmTargets, LlvmPasses)
 
-data IntegerLibrary
-    = IntegerGMP
-    | IntegerSimple
-    deriving (Read, Show, Eq)
-
-data Settings = Settings {
-  sTargetPlatform        :: Platform,       -- Filled in by SysTools
-  sGhcUsagePath          :: FilePath,       -- ditto
-  sGhciUsagePath         :: FilePath,       -- ditto
-  sToolDir               :: Maybe FilePath, -- ditto
-  sTopDir                :: FilePath,       -- ditto
-  sTmpDir                :: String,      -- no trailing '/'
-  sProgramName           :: String,
-  sProjectVersion        :: String,
-  -- You shouldn't need to look things up in rawSettings directly.
-  -- They should have their own fields instead.
-  sRawSettings           :: [(String, String)],
-  sExtraGccViaCFlags     :: [String],
-  sSystemPackageConfig   :: FilePath,
-  sLdSupportsCompactUnwind :: Bool,
-  sLdSupportsBuildId       :: Bool,
-  sLdSupportsFilelist      :: Bool,
-  sLdIsGnuLd               :: Bool,
-  sGccSupportsNoPie        :: Bool,
-  -- commands for particular phases
-  sPgm_L                 :: String,
-  sPgm_P                 :: (String,[Option]),
-  sPgm_F                 :: String,
-  sPgm_c                 :: (String,[Option]),
-  sPgm_a                 :: (String,[Option]),
-  sPgm_l                 :: (String,[Option]),
-  sPgm_dll               :: (String,[Option]),
-  sPgm_T                 :: String,
-  sPgm_windres           :: String,
-  sPgm_libtool           :: String,
-  sPgm_ar                :: String,
-  sPgm_ranlib            :: String,
-  sPgm_lo                :: (String,[Option]), -- LLVM: opt llvm optimiser
-  sPgm_lc                :: (String,[Option]), -- LLVM: llc static compiler
-  sPgm_lcc               :: (String,[Option]), -- LLVM: c compiler
-  sPgm_i                 :: String,
-  -- options for particular phases
-  sOpt_L                 :: [String],
-  sOpt_P                 :: [String],
-  sOpt_P_fingerprint     :: Fingerprint, -- cached Fingerprint of sOpt_P
-                                         -- See Note [Repeated -optP hashing]
-  sOpt_F                 :: [String],
-  sOpt_c                 :: [String],
-  sOpt_cxx               :: [String],
-  sOpt_a                 :: [String],
-  sOpt_l                 :: [String],
-  sOpt_windres           :: [String],
-  sOpt_lo                :: [String], -- LLVM: llvm optimiser
-  sOpt_lc                :: [String], -- LLVM: llc static compiler
-  sOpt_lcc               :: [String], -- LLVM: c compiler
-  sOpt_i                 :: [String], -- iserv options
-
-  sPlatformConstants     :: PlatformConstants,
-
-  -- Formerly Config.hs, target specific
-  sTargetPlatformString :: String, -- TODO Recalculate string from richer info?
-  sIntegerLibrary        :: String,
-  sIntegerLibraryType    :: IntegerLibrary,
-  sGhcWithInterpreter    :: Bool,
-  sGhcWithNativeCodeGen  :: Bool,
-  sGhcWithSMP            :: Bool,
-  sGhcRTSWays            :: String,
-  sTablesNextToCode      :: Bool,
-  sLeadingUnderscore     :: Bool,
-  sLibFFI                :: Bool,
-  sGhcThreaded           :: Bool,
-  sGhcDebugged           :: Bool,
-  sGhcRtsWithLibdw       :: Bool
- }
+-----------------------------------------------------------------------------
+-- Accessessors from 'DynFlags'
 
 targetPlatform :: DynFlags -> Platform
 targetPlatform dflags = sTargetPlatform (settings dflags)
@@ -2671,14 +2664,16 @@ setDumpPrefixForce f d = d { dumpPrefixForce = f}
 
 -- XXX HACK: Prelude> words "'does not' work" ===> ["'does","not'","work"]
 -- Config.hs should really use Option.
-setPgmP   f = let (pgm:args) = words f in alterSettings (\s -> s { sPgm_P   = (pgm, map Option args)})
-addOptl   f = alterSettings (\s -> s { sOpt_l   = f : sOpt_l s})
-addOptc   f = alterSettings (\s -> s { sOpt_c   = f : sOpt_c s})
-addOptcxx f = alterSettings (\s -> s { sOpt_cxx = f : sOpt_cxx s})
-addOptP   f = alterSettings (\s -> s { sOpt_P   = f : sOpt_P s
-                                     , sOpt_P_fingerprint = fingerprintStrings (f : sOpt_P s)
-                                     })
-                                     -- See Note [Repeated -optP hashing]
+setPgmP   f = alterToolSettings (\s -> s { toolSettings_pgm_P   = (pgm, map Option args)})
+  where (pgm:args) = words f
+addOptl   f = alterToolSettings (\s -> s { toolSettings_opt_l   = f : toolSettings_opt_l s})
+addOptc   f = alterToolSettings (\s -> s { toolSettings_opt_c   = f : toolSettings_opt_c s})
+addOptcxx f = alterToolSettings (\s -> s { toolSettings_opt_cxx = f : toolSettings_opt_cxx s})
+addOptP   f = alterToolSettings $ \s -> s
+          { toolSettings_opt_P   = f : toolSettings_opt_P s
+          , toolSettings_opt_P_fingerprint = fingerprintStrings (f : toolSettings_opt_P s)
+          }
+          -- See Note [Repeated -optP hashing]
   where
   fingerprintStrings ss = fingerprintFingerprints $ map fingerprintString ss
 
@@ -2710,27 +2705,6 @@ addGhciScript f d = d { ghciScripts = f : ghciScripts d}
 
 setInteractivePrint f d = d { interactivePrint = Just f}
 
--- -----------------------------------------------------------------------------
--- Command-line options
-
--- | When invoking external tools as part of the compilation pipeline, we
--- pass these a sequence of options on the command-line. Rather than
--- just using a list of Strings, we use a type that allows us to distinguish
--- between filepaths and 'other stuff'. The reason for this is that
--- this type gives us a handle on transforming filenames, and filenames only,
--- to whatever format they're expected to be on a particular platform.
-data Option
- = FileOption -- an entry that _contains_ filename(s) / filepaths.
-              String  -- a non-filepath prefix that shouldn't be
-                      -- transformed (e.g., "/out=")
-              String  -- the filepath/filename portion
- | Option     String
- deriving ( Eq )
-
-showOpt :: Option -> String
-showOpt (FileOption pre f) = pre ++ f
-showOpt (Option s)  = s
-
 -----------------------------------------------------------------------------
 -- Setting the optimisation level
 
@@ -3031,64 +3005,66 @@ dynamic_flags_deps = [
         ------- Specific phases  --------------------------------------------
     -- need to appear before -pgmL to be parsed as LLVM flags.
   , make_ord_flag defFlag "pgmlo"
-      (hasArg (\f -> alterSettings (\s -> s { sPgm_lo  = (f,[])})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_lo  = (f,[]) }
   , make_ord_flag defFlag "pgmlc"
-      (hasArg (\f -> alterSettings (\s -> s { sPgm_lc  = (f,[])})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_lc  = (f,[]) }
   , make_ord_flag defFlag "pgmi"
-      (hasArg (\f -> alterSettings (\s -> s { sPgm_i  =  f})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_i   =  f }
   , make_ord_flag defFlag "pgmL"
-      (hasArg (\f -> alterSettings (\s -> s { sPgm_L   = f})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_L   = f }
   , make_ord_flag defFlag "pgmP"
       (hasArg setPgmP)
   , make_ord_flag defFlag "pgmF"
-      (hasArg (\f -> alterSettings (\s -> s { sPgm_F   = f})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_F   = f }
   , make_ord_flag defFlag "pgmc"
-      (hasArg (\f -> alterSettings (\s -> s { sPgm_c   = (f,[]),
-                                              -- Don't pass -no-pie with -pgmc
-                                              -- (see #15319)
-                                              sGccSupportsNoPie = False})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s
+         { toolSettings_pgm_c   = (f,[])
+         , -- Don't pass -no-pie with -pgmc
+           -- (see #15319)
+           toolSettings_ccSupportsNoPie = False
+         }
   , make_ord_flag defFlag "pgms"
       (HasArg (\_ -> addWarn "Object splitting was removed in GHC 8.8"))
   , make_ord_flag defFlag "pgma"
-      (hasArg (\f -> alterSettings (\s -> s { sPgm_a   = (f,[])})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_a   = (f,[]) }
   , make_ord_flag defFlag "pgml"
-      (hasArg (\f -> alterSettings (\s -> s { sPgm_l   = (f,[])})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_l   = (f,[]) }
   , make_ord_flag defFlag "pgmdll"
-      (hasArg (\f -> alterSettings (\s -> s { sPgm_dll = (f,[])})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_dll = (f,[]) }
   , make_ord_flag defFlag "pgmwindres"
-      (hasArg (\f -> alterSettings (\s -> s { sPgm_windres = f})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_windres = f }
   , make_ord_flag defFlag "pgmlibtool"
-      (hasArg (\f -> alterSettings (\s -> s { sPgm_libtool = f})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_libtool = f }
   , make_ord_flag defFlag "pgmar"
-      (hasArg (\f -> alterSettings (\s -> s { sPgm_ar = f})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_ar = f }
   , make_ord_flag defFlag "pgmranlib"
-      (hasArg (\f -> alterSettings (\s -> s { sPgm_ranlib = f})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_ranlib = f }
 
 
     -- need to appear before -optl/-opta to be parsed as LLVM flags.
   , make_ord_flag defFlag "optlo"
-      (hasArg (\f -> alterSettings (\s -> s { sOpt_lo  = f : sOpt_lo s})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_opt_lo  = f : toolSettings_opt_lo s }
   , make_ord_flag defFlag "optlc"
-      (hasArg (\f -> alterSettings (\s -> s { sOpt_lc  = f : sOpt_lc s})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_opt_lc  = f : toolSettings_opt_lc s }
   , make_ord_flag defFlag "opti"
-      (hasArg (\f -> alterSettings (\s -> s { sOpt_i   = f : sOpt_i s})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_opt_i   = f : toolSettings_opt_i s }
   , make_ord_flag defFlag "optL"
-      (hasArg (\f -> alterSettings (\s -> s { sOpt_L   = f : sOpt_L s})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_opt_L   = f : toolSettings_opt_L s }
   , make_ord_flag defFlag "optP"
       (hasArg addOptP)
   , make_ord_flag defFlag "optF"
-      (hasArg (\f -> alterSettings (\s -> s { sOpt_F   = f : sOpt_F s})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_opt_F   = f : toolSettings_opt_F s }
   , make_ord_flag defFlag "optc"
       (hasArg addOptc)
   , make_ord_flag defFlag "optcxx"
       (hasArg addOptcxx)
   , make_ord_flag defFlag "opta"
-      (hasArg (\f -> alterSettings (\s -> s { sOpt_a   = f : sOpt_a s})))
+      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_opt_a   = f : toolSettings_opt_a s }
   , make_ord_flag defFlag "optl"
       (hasArg addOptl)
   , make_ord_flag defFlag "optwindres"
-      (hasArg (\f ->
-        alterSettings (\s -> s { sOpt_windres = f : sOpt_windres s})))
+      $ hasArg $ \f ->
+        alterToolSettings $ \s -> s { toolSettings_opt_windres = f : toolSettings_opt_windres s }
 
   , make_ord_flag defGhcFlag "split-objs"
       (NoArg $ addWarn "ignoring -split-objs")
@@ -5110,6 +5086,12 @@ unSetExtensionFlag' f dflags = xopt_unset dflags f
 alterSettings :: (Settings -> Settings) -> DynFlags -> DynFlags
 alterSettings f dflags = dflags { settings = f (settings dflags) }
 
+alterFileSettings :: (FileSettings -> FileSettings) -> DynFlags -> DynFlags
+alterFileSettings = alterSettings . \f settings -> settings { sFileSettings = f (sFileSettings settings) }
+
+alterToolSettings :: (ToolSettings -> ToolSettings) -> DynFlags -> DynFlags
+alterToolSettings = alterSettings . \f settings -> settings { sToolSettings = f (sToolSettings settings) }
+
 --------------------------
 setDumpFlag' :: DumpFlag -> DynP ()
 setDumpFlag' dump_flag
@@ -5545,7 +5527,7 @@ splitPathList s = filter notNull (splitUp s)
 -- tmpDir, where we store temporary files.
 
 setTmpDir :: FilePath -> DynFlags -> DynFlags
-setTmpDir dir = alterSettings (\s -> s { sTmpDir = normalise dir })
+setTmpDir dir = alterFileSettings $ \s -> s { fileSettings_tmpDir = normalise dir }
   -- we used to fix /cygdrive/c/.. on Windows, but this doesn't
   -- seem necessary now --SDM 7/2/2008
 
diff --git a/compiler/main/FileSettings.hs b/compiler/main/FileSettings.hs
new file mode 100644
index 0000000000..f531d206a9
--- /dev/null
+++ b/compiler/main/FileSettings.hs
@@ -0,0 +1,16 @@
+module FileSettings
+  ( FileSettings (..)
+  ) where
+
+import GhcPrelude
+
+-- | Paths to various files and directories used by GHC, including those that
+-- provide more settings.
+data FileSettings = FileSettings
+  { fileSettings_ghcUsagePath        :: FilePath       -- ditto
+  , fileSettings_ghciUsagePath       :: FilePath       -- ditto
+  , fileSettings_toolDir             :: Maybe FilePath -- ditto
+  , fileSettings_topDir              :: FilePath       -- ditto
+  , fileSettings_tmpDir              :: String      -- no trailing '/'
+  , fileSettings_systemPackageConfig :: FilePath
+  }
diff --git a/compiler/main/GhcNameVersion.hs b/compiler/main/GhcNameVersion.hs
new file mode 100644
index 0000000000..96e04186a7
--- /dev/null
+++ b/compiler/main/GhcNameVersion.hs
@@ -0,0 +1,11 @@
+module GhcNameVersion
+  ( GhcNameVersion (..)
+  ) where
+
+import GhcPrelude
+
+-- | Settings for what GHC this is.
+data GhcNameVersion = GhcNameVersion
+  { ghcNameVersion_programName    :: String
+  , ghcNameVersion_projectVersion :: String
+  }
diff --git a/compiler/main/Settings.hs b/compiler/main/Settings.hs
new file mode 100644
index 0000000000..5a5f5ca3c9
--- /dev/null
+++ b/compiler/main/Settings.hs
@@ -0,0 +1,203 @@
+module Settings
+  ( Settings (..)
+  , sProgramName
+  , sProjectVersion
+  , sGhcUsagePath
+  , sGhciUsagePath
+  , sToolDir
+  , sTopDir
+  , sTmpDir
+  , sSystemPackageConfig
+  , sLdSupportsCompactUnwind
+  , sLdSupportsBuildId
+  , sLdSupportsFilelist
+  , sLdIsGnuLd
+  , sGccSupportsNoPie
+  , sPgm_L
+  , sPgm_P
+  , sPgm_F
+  , sPgm_c
+  , sPgm_a
+  , sPgm_l
+  , sPgm_dll
+  , sPgm_T
+  , sPgm_windres
+  , sPgm_libtool
+  , sPgm_ar
+  , sPgm_ranlib
+  , sPgm_lo
+  , sPgm_lc
+  , sPgm_lcc
+  , sPgm_i
+  , sOpt_L
+  , sOpt_P
+  , sOpt_P_fingerprint
+  , sOpt_F
+  , sOpt_c
+  , sOpt_cxx
+  , sOpt_a
+  , sOpt_l
+  , sOpt_windres
+  , sOpt_lo
+  , sOpt_lc
+  , sOpt_lcc
+  , sOpt_i
+  , sExtraGccViaCFlags
+  , sTargetPlatformString
+  , sIntegerLibrary
+  , sIntegerLibraryType
+  , sGhcWithInterpreter
+  , sGhcWithNativeCodeGen
+  , sGhcWithSMP
+  , sGhcRTSWays
+  , sTablesNextToCode
+  , sLeadingUnderscore
+  , sLibFFI
+  , sGhcThreaded
+  , sGhcDebugged
+  , sGhcRtsWithLibdw
+  ) where
+
+import GhcPrelude
+
+import CliOption
+import Fingerprint
+import FileSettings
+import GhcNameVersion
+import Platform
+import PlatformConstants
+import ToolSettings
+
+data Settings = Settings
+  { sGhcNameVersion    :: {-# UNPACk #-} !GhcNameVersion
+  , sFileSettings      :: {-# UNPACK #-} !FileSettings
+  , sTargetPlatform    :: Platform       -- Filled in by SysTools
+  , sToolSettings      :: {-# UNPACK #-} !ToolSettings
+  , sPlatformMisc      :: {-# UNPACK #-} !PlatformMisc
+  , sPlatformConstants :: PlatformConstants
+
+  -- You shouldn't need to look things up in rawSettings directly.
+  -- They should have their own fields instead.
+  , sRawSettings       :: [(String, String)]
+  }
+
+-----------------------------------------------------------------------------
+-- Accessessors from 'Settings'
+
+sProgramName         :: Settings -> String
+sProgramName = ghcNameVersion_programName . sGhcNameVersion
+sProjectVersion      :: Settings -> String
+sProjectVersion = ghcNameVersion_projectVersion . sGhcNameVersion
+
+sGhcUsagePath        :: Settings -> FilePath
+sGhcUsagePath = fileSettings_ghcUsagePath . sFileSettings
+sGhciUsagePath       :: Settings -> FilePath
+sGhciUsagePath = fileSettings_ghciUsagePath . sFileSettings
+sToolDir             :: Settings -> Maybe FilePath
+sToolDir = fileSettings_toolDir . sFileSettings
+sTopDir              :: Settings -> FilePath
+sTopDir = fileSettings_topDir . sFileSettings
+sTmpDir              :: Settings -> String
+sTmpDir = fileSettings_tmpDir . sFileSettings
+sSystemPackageConfig :: Settings -> FilePath
+sSystemPackageConfig = fileSettings_systemPackageConfig . sFileSettings
+
+sLdSupportsCompactUnwind :: Settings -> Bool
+sLdSupportsCompactUnwind = toolSettings_ldSupportsCompactUnwind . sToolSettings
+sLdSupportsBuildId :: Settings -> Bool
+sLdSupportsBuildId = toolSettings_ldSupportsBuildId . sToolSettings
+sLdSupportsFilelist :: Settings -> Bool
+sLdSupportsFilelist = toolSettings_ldSupportsFilelist . sToolSettings
+sLdIsGnuLd :: Settings -> Bool
+sLdIsGnuLd = toolSettings_ldIsGnuLd . sToolSettings
+sGccSupportsNoPie :: Settings -> Bool
+sGccSupportsNoPie = toolSettings_ccSupportsNoPie . sToolSettings
+
+sPgm_L :: Settings -> String
+sPgm_L = toolSettings_pgm_L . sToolSettings
+sPgm_P :: Settings -> (String, [Option])
+sPgm_P = toolSettings_pgm_P . sToolSettings
+sPgm_F :: Settings -> String
+sPgm_F = toolSettings_pgm_F . sToolSettings
+sPgm_c :: Settings -> (String, [Option])
+sPgm_c = toolSettings_pgm_c . sToolSettings
+sPgm_a :: Settings -> (String, [Option])
+sPgm_a = toolSettings_pgm_a . sToolSettings
+sPgm_l :: Settings -> (String, [Option])
+sPgm_l = toolSettings_pgm_l . sToolSettings
+sPgm_dll :: Settings -> (String, [Option])
+sPgm_dll = toolSettings_pgm_dll . sToolSettings
+sPgm_T :: Settings -> String
+sPgm_T = toolSettings_pgm_T . sToolSettings
+sPgm_windres :: Settings -> String
+sPgm_windres = toolSettings_pgm_windres . sToolSettings
+sPgm_libtool :: Settings -> String
+sPgm_libtool = toolSettings_pgm_libtool . sToolSettings
+sPgm_ar :: Settings -> String
+sPgm_ar = toolSettings_pgm_ar . sToolSettings
+sPgm_ranlib :: Settings -> String
+sPgm_ranlib = toolSettings_pgm_ranlib . sToolSettings
+sPgm_lo :: Settings -> (String, [Option])
+sPgm_lo = toolSettings_pgm_lo . sToolSettings
+sPgm_lc :: Settings -> (String, [Option])
+sPgm_lc = toolSettings_pgm_lc . sToolSettings
+sPgm_lcc :: Settings -> (String, [Option])
+sPgm_lcc = toolSettings_pgm_lcc . sToolSettings
+sPgm_i :: Settings -> String
+sPgm_i = toolSettings_pgm_i . sToolSettings
+sOpt_L :: Settings -> [String]
+sOpt_L = toolSettings_opt_L . sToolSettings
+sOpt_P :: Settings -> [String]
+sOpt_P = toolSettings_opt_P . sToolSettings
+sOpt_P_fingerprint :: Settings -> Fingerprint
+sOpt_P_fingerprint = toolSettings_opt_P_fingerprint . sToolSettings
+sOpt_F :: Settings -> [String]
+sOpt_F = toolSettings_opt_F . sToolSettings
+sOpt_c :: Settings -> [String]
+sOpt_c = toolSettings_opt_c . sToolSettings
+sOpt_cxx :: Settings -> [String]
+sOpt_cxx = toolSettings_opt_cxx . sToolSettings
+sOpt_a :: Settings -> [String]
+sOpt_a = toolSettings_opt_a . sToolSettings
+sOpt_l :: Settings -> [String]
+sOpt_l = toolSettings_opt_l . sToolSettings
+sOpt_windres :: Settings -> [String]
+sOpt_windres = toolSettings_opt_windres . sToolSettings
+sOpt_lo :: Settings -> [String]
+sOpt_lo = toolSettings_opt_lo . sToolSettings
+sOpt_lc :: Settings -> [String]
+sOpt_lc = toolSettings_opt_lc . sToolSettings
+sOpt_lcc :: Settings -> [String]
+sOpt_lcc = toolSettings_opt_lcc . sToolSettings
+sOpt_i :: Settings -> [String]
+sOpt_i = toolSettings_opt_i . sToolSettings
+
+sExtraGccViaCFlags :: Settings -> [String]
+sExtraGccViaCFlags = toolSettings_extraGccViaCFlags . sToolSettings
+
+sTargetPlatformString :: Settings -> String
+sTargetPlatformString = platformMisc_targetPlatformString . sPlatformMisc
+sIntegerLibrary :: Settings -> String
+sIntegerLibrary = platformMisc_integerLibrary . sPlatformMisc
+sIntegerLibraryType :: Settings -> IntegerLibrary
+sIntegerLibraryType = platformMisc_integerLibraryType . sPlatformMisc
+sGhcWithInterpreter :: Settings -> Bool
+sGhcWithInterpreter = platformMisc_ghcWithInterpreter . sPlatformMisc
+sGhcWithNativeCodeGen :: Settings -> Bool
+sGhcWithNativeCodeGen = platformMisc_ghcWithNativeCodeGen . sPlatformMisc
+sGhcWithSMP :: Settings -> Bool
+sGhcWithSMP = platformMisc_ghcWithSMP . sPlatformMisc
+sGhcRTSWays :: Settings -> String
+sGhcRTSWays = platformMisc_ghcRTSWays . sPlatformMisc
+sTablesNextToCode :: Settings -> Bool
+sTablesNextToCode = platformMisc_tablesNextToCode . sPlatformMisc
+sLeadingUnderscore :: Settings -> Bool
+sLeadingUnderscore = platformMisc_leadingUnderscore . sPlatformMisc
+sLibFFI :: Settings -> Bool
+sLibFFI = platformMisc_libFFI . sPlatformMisc
+sGhcThreaded :: Settings -> Bool
+sGhcThreaded = platformMisc_ghcThreaded . sPlatformMisc
+sGhcDebugged :: Settings -> Bool
+sGhcDebugged = platformMisc_ghcDebugged . sPlatformMisc
+sGhcRtsWithLibdw :: Settings -> Bool
+sGhcRtsWithLibdw = platformMisc_ghcRtsWithLibdw . sPlatformMisc
diff --git a/compiler/main/SysTools.hs b/compiler/main/SysTools.hs
index b3dc60654e..763477a1c9 100644
--- a/compiler/main/SysTools.hs
+++ b/compiler/main/SysTools.hs
@@ -49,6 +49,7 @@ import Platform
 import Util
 import DynFlags
 import Fingerprint
+import ToolSettings
 
 import System.FilePath
 import System.IO
@@ -282,68 +283,82 @@ initSysTools top_dir
        ghcDebugged <- getBooleanSetting "Use Debugging"
        ghcRtsWithLibdw <- getBooleanSetting "RTS expects libdw"
 
-       return $ Settings {
-                    sTargetPlatform = platform,
-                    sTmpDir         = normalise tmpdir,
-                    sGhcUsagePath   = ghc_usage_msg_path,
-                    sGhciUsagePath  = ghci_usage_msg_path,
-                    sToolDir        = mtool_dir,
-                    sTopDir         = top_dir,
-                    sRawSettings    = mySettings,
-                    sExtraGccViaCFlags = words myExtraGccViaCFlags,
-                    sSystemPackageConfig = pkgconfig_path,
-                    sLdSupportsCompactUnwind = ldSupportsCompactUnwind,
-                    sLdSupportsBuildId       = ldSupportsBuildId,
-                    sLdSupportsFilelist      = ldSupportsFilelist,
-                    sLdIsGnuLd               = ldIsGnuLd,
-                    sGccSupportsNoPie        = gccSupportsNoPie,
-                    sProgramName             = "ghc",
-                    sProjectVersion          = cProjectVersion,
-                    sPgm_L   = unlit_path,
-                    sPgm_P   = (cpp_prog, cpp_args),
-                    sPgm_F   = "",
-                    sPgm_c   = (gcc_prog, gcc_args),
-                    sPgm_a   = (as_prog, as_args),
-                    sPgm_l   = (ld_prog, ld_args),
-                    sPgm_dll = (mkdll_prog,mkdll_args),
-                    sPgm_T   = touch_path,
-                    sPgm_windres = windres_path,
-                    sPgm_libtool = libtool_path,
-                    sPgm_ar = ar_path,
-                    sPgm_ranlib = ranlib_path,
-                    sPgm_lo  = (lo_prog,[]),
-                    sPgm_lc  = (lc_prog,[]),
-                    sPgm_lcc = (lcc_prog,[]),
-                    sPgm_i   = iserv_prog,
-                    sOpt_L       = [],
-                    sOpt_P       = [],
-                    sOpt_P_fingerprint = fingerprint0,
-                    sOpt_F       = [],
-                    sOpt_c       = [],
-                    sOpt_cxx     = [],
-                    sOpt_a       = [],
-                    sOpt_l       = [],
-                    sOpt_windres = [],
-                    sOpt_lcc     = [],
-                    sOpt_lo      = [],
-                    sOpt_lc      = [],
-                    sOpt_i       = [],
-                    sPlatformConstants = platformConstants,
-
-                    sTargetPlatformString = targetPlatformString,
-                    sIntegerLibrary = integerLibrary,
-                    sIntegerLibraryType = integerLibraryType,
-                    sGhcWithInterpreter = ghcWithInterpreter,
-                    sGhcWithNativeCodeGen = ghcWithNativeCodeGen,
-                    sGhcWithSMP = ghcWithSMP,
-                    sGhcRTSWays = ghcRTSWays,
-                    sTablesNextToCode = tablesNextToCode,
-                    sLeadingUnderscore = leadingUnderscore,
-                    sLibFFI = useLibFFI,
-                    sGhcThreaded = ghcThreaded,
-                    sGhcDebugged = ghcDebugged,
-                    sGhcRtsWithLibdw = ghcRtsWithLibdw
-             }
+       return $ Settings
+         { sGhcNameVersion = GhcNameVersion
+           { ghcNameVersion_programName = "ghc"
+           , ghcNameVersion_projectVersion = cProjectVersion
+           }
+
+         , sFileSettings = FileSettings
+           { fileSettings_tmpDir         = normalise tmpdir
+           , fileSettings_ghcUsagePath   = ghc_usage_msg_path
+           , fileSettings_ghciUsagePath  = ghci_usage_msg_path
+           , fileSettings_toolDir        = mtool_dir
+           , fileSettings_topDir         = top_dir
+           , fileSettings_systemPackageConfig = pkgconfig_path
+           }
+
+         , sToolSettings = ToolSettings
+           { toolSettings_ldSupportsCompactUnwind = ldSupportsCompactUnwind
+           , toolSettings_ldSupportsBuildId       = ldSupportsBuildId
+           , toolSettings_ldSupportsFilelist      = ldSupportsFilelist
+           , toolSettings_ldIsGnuLd               = ldIsGnuLd
+           , toolSettings_ccSupportsNoPie         = gccSupportsNoPie
+
+           , toolSettings_pgm_L   = unlit_path
+           , toolSettings_pgm_P   = (cpp_prog, cpp_args)
+           , toolSettings_pgm_F   = ""
+           , toolSettings_pgm_c   = (gcc_prog, gcc_args)
+           , toolSettings_pgm_a   = (as_prog, as_args)
+           , toolSettings_pgm_l   = (ld_prog, ld_args)
+           , toolSettings_pgm_dll = (mkdll_prog,mkdll_args)
+           , toolSettings_pgm_T   = touch_path
+           , toolSettings_pgm_windres = windres_path
+           , toolSettings_pgm_libtool = libtool_path
+           , toolSettings_pgm_ar = ar_path
+           , toolSettings_pgm_ranlib = ranlib_path
+           , toolSettings_pgm_lo  = (lo_prog,[])
+           , toolSettings_pgm_lc  = (lc_prog,[])
+           , toolSettings_pgm_lcc = (lcc_prog,[])
+           , toolSettings_pgm_i   = iserv_prog
+           , toolSettings_opt_L       = []
+           , toolSettings_opt_P       = []
+           , toolSettings_opt_P_fingerprint = fingerprint0
+           , toolSettings_opt_F       = []
+           , toolSettings_opt_c       = []
+           , toolSettings_opt_cxx     = []
+           , toolSettings_opt_a       = []
+           , toolSettings_opt_l       = []
+           , toolSettings_opt_windres = []
+           , toolSettings_opt_lcc     = []
+           , toolSettings_opt_lo      = []
+           , toolSettings_opt_lc      = []
+           , toolSettings_opt_i       = []
+
+           , toolSettings_extraGccViaCFlags = words myExtraGccViaCFlags
+           }
+
+         , sTargetPlatform = platform
+         , sPlatformMisc = PlatformMisc
+           { platformMisc_targetPlatformString = targetPlatformString
+           , platformMisc_integerLibrary = integerLibrary
+           , platformMisc_integerLibraryType = integerLibraryType
+           , platformMisc_ghcWithInterpreter = ghcWithInterpreter
+           , platformMisc_ghcWithNativeCodeGen = ghcWithNativeCodeGen
+           , platformMisc_ghcWithSMP = ghcWithSMP
+           , platformMisc_ghcRTSWays = ghcRTSWays
+           , platformMisc_tablesNextToCode = tablesNextToCode
+           , platformMisc_leadingUnderscore = leadingUnderscore
+           , platformMisc_libFFI = useLibFFI
+           , platformMisc_ghcThreaded = ghcThreaded
+           , platformMisc_ghcDebugged = ghcDebugged
+           , platformMisc_ghcRtsWithLibdw = ghcRtsWithLibdw
+           }
+
+         , sPlatformConstants = platformConstants
+
+         , sRawSettings    = mySettings
+         }
 
 
 {- Note [Windows stack usage]
diff --git a/compiler/main/ToolSettings.hs b/compiler/main/ToolSettings.hs
new file mode 100644
index 0000000000..e15c6923e2
--- /dev/null
+++ b/compiler/main/ToolSettings.hs
@@ -0,0 +1,64 @@
+module ToolSettings
+  ( ToolSettings (..)
+  ) where
+
+import GhcPrelude
+
+import CliOption
+import Fingerprint
+
+-- | Settings for other executables GHC calls.
+--
+-- Probably should futher split down by phase, or split between
+-- platform-specific and platform-agnostic.
+data ToolSettings = ToolSettings
+  { toolSettings_ldSupportsCompactUnwind :: Bool
+  , toolSettings_ldSupportsBuildId       :: Bool
+  , toolSettings_ldSupportsFilelist      :: Bool
+  , toolSettings_ldIsGnuLd               :: Bool
+  , toolSettings_ccSupportsNoPie         :: Bool
+
+  -- commands for particular phases
+  , toolSettings_pgm_L       :: String
+  , toolSettings_pgm_P       :: (String, [Option])
+  , toolSettings_pgm_F       :: String
+  , toolSettings_pgm_c       :: (String, [Option])
+  , toolSettings_pgm_a       :: (String, [Option])
+  , toolSettings_pgm_l       :: (String, [Option])
+  , toolSettings_pgm_dll     :: (String, [Option])
+  , toolSettings_pgm_T       :: String
+  , toolSettings_pgm_windres :: String
+  , toolSettings_pgm_libtool :: String
+  , toolSettings_pgm_ar      :: String
+  , toolSettings_pgm_ranlib  :: String
+  , -- | LLVM: opt llvm optimiser
+    toolSettings_pgm_lo      :: (String, [Option])
+  , -- | LLVM: llc static compiler
+    toolSettings_pgm_lc      :: (String, [Option])
+  , -- | LLVM: c compiler
+    toolSettings_pgm_lcc     :: (String, [Option])
+  , toolSettings_pgm_i       :: String
+
+  -- options for particular phases
+  , toolSettings_opt_L             :: [String]
+  , toolSettings_opt_P             :: [String]
+  , -- | cached Fingerprint of sOpt_P
+    -- See Note [Repeated -optP hashing]
+    toolSettings_opt_P_fingerprint :: Fingerprint
+  , toolSettings_opt_F             :: [String]
+  , toolSettings_opt_c             :: [String]
+  , toolSettings_opt_cxx           :: [String]
+  , toolSettings_opt_a             :: [String]
+  , toolSettings_opt_l             :: [String]
+  , toolSettings_opt_windres       :: [String]
+  , -- | LLVM: llvm optimiser
+    toolSettings_opt_lo            :: [String]
+  , -- | LLVM: llc static compiler
+    toolSettings_opt_lc            :: [String]
+  , -- | LLVM: c compiler
+    toolSettings_opt_lcc           :: [String]
+  , -- | iserv options
+    toolSettings_opt_i             :: [String]
+
+  , toolSettings_extraGccViaCFlags :: [String]
+  }
diff --git a/compiler/utils/Platform.hs b/compiler/utils/Platform.hs
index 449a62a5b6..5f7d939f0d 100644
--- a/compiler/utils/Platform.hs
+++ b/compiler/utils/Platform.hs
@@ -16,6 +16,9 @@ module Platform (
         osMachOTarget,
         osSubsectionsViaSymbols,
         platformUsesFrameworks,
+
+        PlatformMisc(..),
+        IntegerLibrary(..),
 )
 
 where
@@ -160,3 +163,28 @@ osSubsectionsViaSymbols :: OS -> Bool
 osSubsectionsViaSymbols OSDarwin = True
 osSubsectionsViaSymbols _        = False
 
+-- | Platform-specific settings formerly hard-coded in Config.hs.
+--
+-- These should probably be all be triaged whether they can be computed from
+-- other settings or belong in another another place (like 'Platform' above).
+data PlatformMisc = PlatformMisc
+  { -- TODO Recalculate string from richer info?
+    platformMisc_targetPlatformString :: String
+  , platformMisc_integerLibrary       :: String
+  , platformMisc_integerLibraryType   :: IntegerLibrary
+  , platformMisc_ghcWithInterpreter   :: Bool
+  , platformMisc_ghcWithNativeCodeGen :: Bool
+  , platformMisc_ghcWithSMP           :: Bool
+  , platformMisc_ghcRTSWays           :: String
+  , platformMisc_tablesNextToCode     :: Bool
+  , platformMisc_leadingUnderscore    :: Bool
+  , platformMisc_libFFI               :: Bool
+  , platformMisc_ghcThreaded          :: Bool
+  , platformMisc_ghcDebugged          :: Bool
+  , platformMisc_ghcRtsWithLibdw      :: Bool
+  }
+
+data IntegerLibrary
+    = IntegerGMP
+    | IntegerSimple
+    deriving (Read, Show, Eq)