Per stage headers, ghc_boot_platform.h -> stage 0 ghcplatform.h

The generated headers are now generated per stage, which means we can
skip hacks like `ghc_boot_platform.h` and just have that be the stage 0
header as proper. In general, stages are to be embraced: freely generate
everything in each stage but then just build what you depend on, and
everything is symmetrical and efficient. Trying to avoid stages because
bootstrapping is a mind bender just creates tons of bespoke
mini-mind-benders that add up to something far crazier.

Hadrian was pretty close to this "stage-major" approach already, and so
was fairly easy to fix. Make needed more work, however: it did know
about stages so at least there was a scaffold, but few packages except
for the compiler cared, and the compiler used its own counting system.
That said, make and Hadrian now work more similarly, which is good for
the transition to Hadrian. The merits of embracing stage aside, the
change may be worthy for easing that transition alone.

10 files changed, 102 insertions, 142 deletions

diff --git a/hadrian/src/Base.hs b/hadrian/src/Base.hs
index bc4eab354e..f7f1029d4e 100644
--- a/hadrian/src/Base.hs
+++ b/hadrian/src/Base.hs
@@ -23,7 +23,7 @@ module Base (
 
     -- * Paths
     hadrianPath, configPath, configFile, sourcePath, shakeFilesDir,
-    generatedDir, generatedPath, stageBinPath, stageLibPath, templateHscPath,
+    stageBinPath, stageLibPath, templateHscPath,
     ghcBinDeps, ghcLibDeps, includesDependencies, haddockDeps,
     relativePackageDbPath, packageDbPath, packageDbStamp, mingwStamp,
     ) where
@@ -68,22 +68,14 @@ sourcePath = hadrianPath -/- "src"
 configH :: FilePath
 configH = "mk/config.h"
 
-ghcVersionH :: Action FilePath
-ghcVersionH = generatedPath <&> (-/- "ghcversion.h")
+ghcVersionH :: Stage -> Action FilePath
+ghcVersionH stage = stageLibPath stage <&> (-/- "ghcversion.h")
 
 -- | The directory in 'buildRoot' containing the Shake database and other
 -- auxiliary files generated by Hadrian.
 shakeFilesDir :: FilePath
 shakeFilesDir = "hadrian"
 
--- | The directory in 'buildRoot' containing generated source files that are not
--- package-specific, e.g. @ghcplatform.h@.
-generatedDir :: FilePath
-generatedDir = "generated"
-
-generatedPath :: Action FilePath
-generatedPath = buildRoot <&> (-/- generatedDir)
-
 -- | Path to the package database for a given build stage, relative to the build
 -- root.
 relativePackageDbPath :: Stage -> FilePath
@@ -122,10 +114,11 @@ ghcBinDeps stage = mapM (\f -> stageLibPath stage <&> (-/- f))
     , "ghci-usage.txt"
     ]
 
-includesDependencies :: Action [FilePath]
-includesDependencies = do
-    path <- generatedPath
-    return $ (path -/-) <$> [ "ghcautoconf.h", "ghcplatform.h", "ghcversion.h" ]
+includesDependencies :: Stage -> Action [FilePath]
+includesDependencies stage = do
+    p <- stageLibPath stage
+    pure $ (p -/-) <$>
+      [ "ghcautoconf.h", "ghcplatform.h", "ghcversion.h" ]
 
 -- | Files the `haddock` binary depends on
 haddockDeps :: Stage -> Action [FilePath]
diff --git a/hadrian/src/Builder.hs b/hadrian/src/Builder.hs
index 587c62fa16..34027d7bbb 100644
--- a/hadrian/src/Builder.hs
+++ b/hadrian/src/Builder.hs
@@ -176,12 +176,12 @@ instance H.Builder Builder where
         Autoreconf dir -> return [dir -/- "configure.ac"]
         Configure  dir -> return [dir -/- "configure"]
 
-        Ghc _ Stage0 -> generatedGhcDependencies Stage0
+        Ghc _ Stage0 -> includesDependencies Stage0
         Ghc _ stage -> do
             root <- buildRoot
             touchyPath <- programPath (vanillaContext Stage0 touchy)
             unlitPath  <- builderPath Unlit
-            ghcgens <- generatedGhcDependencies stage
+            ghcgens <- includesDependencies stage
 
             -- GHC from the previous stage is used to build artifacts in the
             -- current stage. Need the previous stage's GHC deps.
diff --git a/hadrian/src/Packages.hs b/hadrian/src/Packages.hs
index 53ecb6897e..c4ae780fb3 100644
--- a/hadrian/src/Packages.hs
+++ b/hadrian/src/Packages.hs
@@ -13,7 +13,7 @@ module Packages (
     -- * Package information
     programName, nonHsMainPackage, autogenPath, programPath, timeoutPath,
     rtsContext, rtsBuildPath, libffiBuildPath, libffiLibraryName,
-    generatedGhcDependencies, ensureConfigured
+    ensureConfigured
     ) where
 
 import Hadrian.Package
@@ -216,12 +216,3 @@ libffiLibraryName = do
         (True , False) -> "ffi"
         (False, False) -> "Cffi"
         (_    , True ) -> "Cffi-6"
-
--- | Generated header files required by GHC in runtime.
-generatedGhcDependencies :: Stage -> Action [FilePath]
-generatedGhcDependencies stage = do
-    let context = vanillaContext stage compiler
-    bh <- buildPath   context <&> (-/- "ghc_boot_platform.h")
-    ch <- contextPath context <&> (-/- "ghc_boot_platform.h")
-    is <- includesDependencies
-    return $ is ++ [bh, ch]
diff --git a/hadrian/src/Rules.hs b/hadrian/src/Rules.hs
index e72623d4ce..3f6397fdcc 100644
--- a/hadrian/src/Rules.hs
+++ b/hadrian/src/Rules.hs
@@ -46,7 +46,7 @@ toolArgsTarget = do
                              (Ghc ToolArgs Stage0) [] ["ignored"]
 
     -- need the autogenerated files so that they are precompiled
-    generatedGhcDependencies Stage0 >>= need
+    includesDependencies Stage0 >>= need
     interpret fake_target Rules.Generate.compilerDependencies >>= need
 
     root <- buildRoot
diff --git a/hadrian/src/Rules/Generate.hs b/hadrian/src/Rules/Generate.hs
index ef3d8aa3b4..c2c3c14372 100644
--- a/hadrian/src/Rules/Generate.hs
+++ b/hadrian/src/Rules/Generate.hs
@@ -1,9 +1,11 @@
 module Rules.Generate (
     isGeneratedCmmFile, compilerDependencies, generatePackageCode,
-    generateRules, copyRules, generatedDependencies, generatedGhcDependencies,
+    generateRules, copyRules, generatedDependencies,
     ghcPrimDependencies
     ) where
 
+import Data.Foldable (for_)
+
 import Base
 import qualified Context
 import Expression
@@ -16,6 +18,7 @@ import Packages
 import Rules.Gmp
 import Rules.Libffi
 import Settings
+import Settings.Builders.DeriveConstants (deriveConstantsPairs)
 import Target
 import Utilities
 
@@ -38,8 +41,8 @@ ghcPrimDependencies = do
     path  <- expr $ buildPath (vanillaContext stage ghcPrim)
     return [path -/- "GHC/Prim.hs", path -/- "GHC/PrimopWrappers.hs"]
 
-derivedConstantsDependencies :: [FilePath]
-derivedConstantsDependencies = fmap (generatedDir -/-)
+derivedConstantsFiles :: [FilePath]
+derivedConstantsFiles =
     [ "DerivedConstants.h"
     , "GHCConstantsHaskellExports.hs"
     , "GHCConstantsHaskellType.hs"
@@ -47,13 +50,13 @@ derivedConstantsDependencies = fmap (generatedDir -/-)
 
 compilerDependencies :: Expr [FilePath]
 compilerDependencies = do
-    root    <- getBuildRoot
     stage   <- getStage
     isGmp   <- (== integerGmp) <$> getIntegerPackage
     ghcPath <- expr $ buildPath (vanillaContext stage compiler)
     gmpPath <- expr gmpBuildPath
     rtsPath <- expr (rtsBuildPath stage)
-    mconcat [ return ((root -/-) <$> derivedConstantsDependencies)
+    libDir <- expr $ stageLibPath stage
+    mconcat [ return $ (libDir -/-) <$> derivedConstantsFiles
             , notStage0 ? isGmp ? return [gmpPath -/- gmpLibraryH]
             , notStage0 ? return ((rtsPath -/-) <$> libffiHeaderFiles)
             , return $ fmap (ghcPath -/-)
@@ -75,15 +78,15 @@ compilerDependencies = do
 
 generatedDependencies :: Expr [FilePath]
 generatedDependencies = do
-    root     <- getBuildRoot
     stage    <- getStage
     rtsPath  <- expr (rtsBuildPath stage)
-    includes <- expr includesDependencies
+    includes <- expr $ includesDependencies stage
+    libDir <- expr $ stageLibPath stage
     mconcat [ package compiler ? compilerDependencies
             , package ghcPrim  ? ghcPrimDependencies
             , package rts      ? return (fmap (rtsPath -/-) libffiHeaderFiles
                 ++ includes
-                ++ fmap (root -/-) derivedConstantsDependencies)
+                ++ ((libDir -/-) <$> derivedConstantsFiles))
             , stage0 ? return includes ]
 
 generate :: FilePath -> Context -> Expr String -> Action ()
@@ -121,21 +124,18 @@ generatePackageCode context@(Context stage pkg _) = do
 
     when (pkg == compiler) $ do
         root -/- primopsTxt stage %> \file -> do
-            includes <- includesDependencies
+            includes <- includesDependencies stage
             need $ [primopsSource] ++ includes
             build $ target context HsCpp [primopsSource] [file]
 
-        root -/- stageString stage -/- "**" -/- "ghc_boot_platform.h" %>
-            go generateGhcBootPlatformH
-
     when (pkg == rts) $ do
         root -/- "**" -/- dir -/- "cmm/AutoApply.cmm" %> \file ->
             build $ target context GenApply [] [file]
         -- TODO: This should be fixed properly, e.g. generated here on demand.
-        (root -/- "**" -/- dir -/- "DerivedConstants.h") <~ (buildRoot <&> (-/- generatedDir))
-        (root -/- "**" -/- dir -/- "ghcautoconf.h") <~ (buildRoot <&> (-/- generatedDir))
-        (root -/- "**" -/- dir -/- "ghcplatform.h") <~ (buildRoot <&> (-/- generatedDir))
-        (root -/- "**" -/- dir -/- "ghcversion.h") <~ (buildRoot <&> (-/- generatedDir))
+        (root -/- "**" -/- dir -/- "DerivedConstants.h") <~ stageLibPath stage
+        (root -/- "**" -/- dir -/- "ghcautoconf.h") <~ stageLibPath stage
+        (root -/- "**" -/- dir -/- "ghcplatform.h") <~ stageLibPath stage
+        (root -/- "**" -/- dir -/- "ghcversion.h") <~ stageLibPath stage
  where
     pattern <~ mdir = pattern %> \file -> do
         dir <- mdir
@@ -162,7 +162,6 @@ copyRules = do
         prefix -/- "ghci-usage.txt"    <~ return "driver"
         prefix -/- "llvm-targets"      <~ return "."
         prefix -/- "llvm-passes"       <~ return "."
-        prefix -/- "platformConstants" <~ (buildRoot <&> (-/- generatedDir))
         prefix -/- "template-hsc.h"    <~ return (pkgPath hsc2hs)
 
         prefix -/- "html/**"           <~ return "utils/haddock/haddock-api/resources"
@@ -175,20 +174,19 @@ generateRules = do
     (root -/- "ghc-stage1") <~+ ghcWrapper Stage1
     (root -/- "ghc-stage2") <~+ ghcWrapper Stage2
 
-    priority 2.0 $ (root -/- generatedDir -/- "ghcautoconf.h") <~ generateGhcAutoconfH
-    priority 2.0 $ (root -/- generatedDir -/- "ghcplatform.h") <~ generateGhcPlatformH
-    priority 2.0 $ (root -/- generatedDir -/-  "ghcversion.h") <~ generateGhcVersionH
     forM_ [Stage0 ..] $ \stage -> do
         let prefix = root -/- stageString stage -/- "lib"
             go gen file = generate file (semiEmptyTarget stage) gen
-        priority 2.0 $ (prefix -/- "settings") %> go generateSettings
-
-    -- TODO: simplify, get rid of fake rts context
-    root -/- generatedDir -/- "**" %> \file -> do
-        withTempDir $ \dir -> build $
-            target (rtsContext Stage1) DeriveConstants [] [file, dir]
+        (prefix -/- "ghcplatform.h") %> go generateGhcPlatformH
+        (prefix -/- "settings") %> go generateSettings
+        (prefix -/- "ghcautoconf.h") %> go generateGhcAutoconfH
+        (prefix -/- "ghcversion.h") %> go generateGhcVersionH
+        -- TODO: simplify, get rid of fake rts context
+        for_ (fst <$> deriveConstantsPairs) $ \constantsFile ->
+            prefix -/- constantsFile %> \file -> do
+                withTempDir $ \dir -> build $
+                    target (rtsContext stage) DeriveConstants [] [file, dir]
   where
-    file <~  gen = file %> \out -> generate out emptyTarget gen
     file <~+ gen = file %> \out -> generate out emptyTarget gen >> makeExecutable out
 
 -- TODO: Use the Types, Luke! (drop partial function)
@@ -225,39 +223,44 @@ cppify = replaceEq '-' '_' . replaceEq '.' '_'
 generateGhcPlatformH :: Expr String
 generateGhcPlatformH = do
     trackGenerateHs
-    hostPlatform   <- getSetting HostPlatform
-    hostArch       <- getSetting HostArch
-    hostOs         <- getSetting HostOs
-    hostVendor     <- getSetting HostVendor
-    targetPlatform <- getSetting TargetPlatform
-    targetArch     <- getSetting TargetArch
-    targetOs       <- getSetting TargetOs
-    targetVendor   <- getSetting TargetVendor
+    stage    <- getStage
+    let chooseSetting x y = getSetting $ if stage == Stage0 then x else y
+    buildPlatform  <- chooseSetting BuildPlatform HostPlatform
+    buildArch      <- chooseSetting BuildArch     HostArch
+    buildOs        <- chooseSetting BuildOs       HostOs
+    buildVendor    <- chooseSetting BuildVendor   HostVendor
+    hostPlatform   <- chooseSetting HostPlatform  TargetPlatform
+    hostArch       <- chooseSetting HostArch      TargetArch
+    hostOs         <- chooseSetting HostOs        TargetOs
+    hostVendor     <- chooseSetting HostVendor    TargetVendor
     ghcUnreg       <- getFlag    GhcUnregisterised
     return . unlines $
         [ "#if !defined(__GHCPLATFORM_H__)"
         , "#define __GHCPLATFORM_H__"
         , ""
-        , "#define BuildPlatform_TYPE  " ++ cppify hostPlatform
-        , "#define HostPlatform_TYPE   " ++ cppify targetPlatform
+        , "#define BuildPlatform_NAME  " ++ show buildPlatform
+        , "#define HostPlatform_NAME   " ++ show hostPlatform
         , ""
-        , "#define " ++ cppify hostPlatform   ++ "_BUILD 1"
-        , "#define " ++ cppify targetPlatform ++ "_HOST 1"
+        , "#define BuildPlatform_TYPE  " ++ cppify buildPlatform
+        , "#define HostPlatform_TYPE   " ++ cppify hostPlatform
         , ""
-        , "#define " ++ hostArch   ++ "_BUILD_ARCH 1"
-        , "#define " ++ targetArch ++ "_HOST_ARCH 1"
-        , "#define BUILD_ARCH " ++ show hostArch
-        , "#define HOST_ARCH "  ++ show targetArch
+        , "#define " ++ cppify buildPlatform   ++ "_BUILD 1"
+        , "#define " ++ cppify hostPlatform ++ "_HOST 1"
         , ""
-        , "#define " ++ hostOs   ++ "_BUILD_OS 1"
-        , "#define " ++ targetOs ++ "_HOST_OS 1"
-        , "#define BUILD_OS " ++ show hostOs
-        , "#define HOST_OS "  ++ show targetOs
+        , "#define " ++ buildArch   ++ "_BUILD_ARCH 1"
+        , "#define " ++ hostArch ++ "_HOST_ARCH 1"
+        , "#define BUILD_ARCH " ++ show buildArch
+        , "#define HOST_ARCH "  ++ show hostArch
         , ""
-        , "#define " ++ hostVendor   ++ "_BUILD_VENDOR 1"
-        , "#define " ++ targetVendor ++ "_HOST_VENDOR 1"
-        , "#define BUILD_VENDOR " ++ show hostVendor
-        , "#define HOST_VENDOR "  ++ show targetVendor
+        , "#define " ++ buildOs   ++ "_BUILD_OS 1"
+        , "#define " ++ hostOs ++ "_HOST_OS 1"
+        , "#define BUILD_OS " ++ show buildOs
+        , "#define HOST_OS "  ++ show hostOs
+        , ""
+        , "#define " ++ buildVendor   ++ "_BUILD_VENDOR 1"
+        , "#define " ++ hostVendor ++ "_HOST_VENDOR 1"
+        , "#define BUILD_VENDOR " ++ show buildVendor
+        , "#define HOST_VENDOR "  ++ show hostVendor
         , ""
         ]
         ++
@@ -351,7 +354,7 @@ generateConfigHs = do
         , ""
         , "import GHC.Version"
         , ""
-        , "#include \"ghc_boot_platform.h\""
+        , "#include \"ghcplatform.h\""
         , ""
         , "cBuildPlatformString :: String"
         , "cBuildPlatformString = BuildPlatform_NAME"
@@ -395,47 +398,6 @@ generateGhcAutoconfH = do
             = "/* #undef " ++ takeWhile (/=' ') (drop 8 s) ++ " */"
         | otherwise = s
 
--- | Generate @ghc_boot_platform.h@ headers.
-generateGhcBootPlatformH :: Expr String
-generateGhcBootPlatformH = do
-    trackGenerateHs
-    stage <- getStage
-    let chooseSetting x y = getSetting $ if stage == Stage0 then x else y
-    buildPlatform  <- chooseSetting BuildPlatform HostPlatform
-    buildArch      <- chooseSetting BuildArch     HostArch
-    buildOs        <- chooseSetting BuildOs       HostOs
-    buildVendor    <- chooseSetting BuildVendor   HostVendor
-    hostPlatform   <- chooseSetting HostPlatform  TargetPlatform
-    hostArch       <- chooseSetting HostArch      TargetArch
-    hostOs         <- chooseSetting HostOs        TargetOs
-    hostVendor     <- chooseSetting HostVendor    TargetVendor
-    return $ unlines
-        [ "#if !defined(__PLATFORM_H__)"
-        , "#define __PLATFORM_H__"
-        , ""
-        , "#define BuildPlatform_NAME  " ++ show buildPlatform
-        , "#define HostPlatform_NAME   " ++ show hostPlatform
-        , ""
-        , "#define " ++ cppify buildPlatform  ++ "_BUILD 1"
-        , "#define " ++ cppify hostPlatform   ++ "_HOST 1"
-        , ""
-        , "#define " ++ buildArch  ++ "_BUILD_ARCH 1"
-        , "#define " ++ hostArch   ++ "_HOST_ARCH 1"
-        , "#define BUILD_ARCH "  ++ show buildArch
-        , "#define HOST_ARCH "   ++ show hostArch
-        , ""
-        , "#define " ++ buildOs  ++ "_BUILD_OS 1"
-        , "#define " ++ hostOs   ++ "_HOST_OS 1"
-        , "#define BUILD_OS "  ++ show buildOs
-        , "#define HOST_OS "   ++ show hostOs
-        , ""
-        , "#define " ++ buildVendor  ++ "_BUILD_VENDOR 1"
-        , "#define " ++ hostVendor   ++ "_HOST_VENDOR 1"
-        , "#define BUILD_VENDOR "  ++ show buildVendor
-        , "#define HOST_VENDOR "   ++ show hostVendor
-        , ""
-        , "#endif /* __PLATFORM_H__ */" ]
-
 -- | Generate @ghcversion.h@ header.
 generateGhcVersionH :: Expr String
 generateGhcVersionH = do
diff --git a/hadrian/src/Settings/Builders/Cabal.hs b/hadrian/src/Settings/Builders/Cabal.hs
index 96f67b4abf..763f51636b 100644
--- a/hadrian/src/Settings/Builders/Cabal.hs
+++ b/hadrian/src/Settings/Builders/Cabal.hs
@@ -99,15 +99,16 @@ libraryArgs = do
 configureArgs :: Args
 configureArgs = do
     top  <- expr topDirectory
-    root <- getBuildRoot
     pkg  <- getPackage
+    stage <- getStage
+    libPath <- expr $ stageLibPath stage
     let conf key expr = do
             values <- unwords <$> expr
             not (null values) ?
                 arg ("--configure-option=" ++ key ++ "=" ++ values)
         cFlags   = mconcat [ remove ["-Werror"] cArgs
                            , getStagedSettingList ConfCcArgs
-                           , arg $ "-I" ++ top -/- root -/- generatedDir
+                           , arg $ "-I" ++ libPath
                            -- See https://github.com/snowleopard/hadrian/issues/523
                            , arg $ "-iquote"
                            , arg $ top -/- pkgPath pkg
@@ -127,7 +128,7 @@ configureArgs = do
         , conf "--with-curses-libraries"  $ arg =<< getSetting CursesLibDir
         , flag CrossCompiling ? (conf "--host" $ arg =<< getSetting TargetPlatformFull)
         , conf "--with-cc" $ arg =<< getBuilderPath . (Cc CompileC) =<< getStage
-        , notStage0 ? (arg =<< ("--ghc-option=-ghcversion-file=" ++) <$> expr ((-/-) <$> topDirectory <*> ghcVersionH))]
+        , notStage0 ? (arg =<< ("--ghc-option=-ghcversion-file=" ++) <$> expr ((-/-) <$> topDirectory <*> ghcVersionH stage))]
 
 bootPackageConstraints :: Args
 bootPackageConstraints = stage0 ? do
@@ -140,8 +141,9 @@ bootPackageConstraints = stage0 ? do
 
 cppArgs :: Args
 cppArgs = do
-    root <- getBuildRoot
-    arg $ "-I" ++ root -/- generatedDir
+    stage <- getStage
+    libPath <- expr $ stageLibPath stage
+    arg $ "-I" ++ libPath
 
 withBuilderKey :: Builder -> String
 withBuilderKey b = case b of
diff --git a/hadrian/src/Settings/Builders/Common.hs b/hadrian/src/Settings/Builders/Common.hs
index 5856935fb9..7d9e0fe716 100644
--- a/hadrian/src/Settings/Builders/Common.hs
+++ b/hadrian/src/Settings/Builders/Common.hs
@@ -22,15 +22,16 @@ import UserSettings
 cIncludeArgs :: Args
 cIncludeArgs = do
     pkg     <- getPackage
-    root    <- getBuildRoot
     path    <- getBuildPath
     incDirs <- getContextData includeDirs
     depDirs <- getContextData depIncludeDirs
+    stage <- getStage
     iconvIncludeDir <- getSetting IconvIncludeDir
     gmpIncludeDir   <- getSetting GmpIncludeDir
     ffiIncludeDir   <- getSetting FfiIncludeDir
+    libPath <- expr $ stageLibPath stage
     mconcat [ notStage0 ||^ package compiler ? arg "-Iincludes"
-            , arg $ "-I" ++ root -/- generatedDir
+            , arg $ "-I" ++ libPath
             , arg $ "-I" ++ path
             , pure . map ("-I"++) . filter (/= "") $ [iconvIncludeDir, gmpIncludeDir]
             , flag UseSystemFfi ? arg ("-I" ++ ffiIncludeDir)
diff --git a/hadrian/src/Settings/Builders/DeriveConstants.hs b/hadrian/src/Settings/Builders/DeriveConstants.hs
index 90068b3c4a..0747162f43 100644
--- a/hadrian/src/Settings/Builders/DeriveConstants.hs
+++ b/hadrian/src/Settings/Builders/DeriveConstants.hs
@@ -1,8 +1,19 @@
-module Settings.Builders.DeriveConstants (deriveConstantsBuilderArgs) where
+module Settings.Builders.DeriveConstants (
+    deriveConstantsBuilderArgs, deriveConstantsPairs
+    ) where
 
 import Builder
 import Settings.Builders.Common
 
+deriveConstantsPairs :: [(String, String)]
+deriveConstantsPairs =
+  [ ("DerivedConstants.h", "--gen-header")
+  , ("GHCConstantsHaskellType.hs", "--gen-haskell-type")
+  , ("platformConstants", "--gen-haskell-value")
+  , ("GHCConstantsHaskellWrappers.hs", "--gen-haskell-wrappers")
+  , ("GHCConstantsHaskellExports.hs", "--gen-haskell-exports")
+  ]
+
 -- TODO: do we need to support `includes_CC_OPTS += -DDYNAMIC_BY_DEFAULT`?
 deriveConstantsBuilderArgs :: Args
 deriveConstantsBuilderArgs = builder DeriveConstants ? do
@@ -12,11 +23,8 @@ deriveConstantsBuilderArgs = builder DeriveConstants ? do
             [a, b] -> (a, b)
             _      -> error $ "DeriveConstants: expected two outputs, got " ++ show outs
     mconcat
-        [ output "**/DerivedConstants.h"             ? arg "--gen-header"
-        , output "**/GHCConstantsHaskellType.hs"     ? arg "--gen-haskell-type"
-        , output "**/platformConstants"              ? arg "--gen-haskell-value"
-        , output "**/GHCConstantsHaskellWrappers.hs" ? arg "--gen-haskell-wrappers"
-        , output "**/GHCConstantsHaskellExports.hs"  ? arg "--gen-haskell-exports"
+        [ mconcat $ flip fmap deriveConstantsPairs $ \(fileName, flag) ->
+            output ("**/" ++ fileName) ? arg flag
         , arg "-o", arg outputFile
         , arg "--tmpdir", arg tempDir
         , arg "--gcc-program", arg =<< getBuilderPath (Cc CompileC Stage1)
@@ -28,13 +36,14 @@ deriveConstantsBuilderArgs = builder DeriveConstants ? do
 
 includeCcArgs :: Args
 includeCcArgs = do
-    root <- getBuildRoot
+    stage <- getStage
+    libPath <- expr $ stageLibPath stage
     mconcat [ cArgs
             , cWarnings
             , getSettingList $ ConfCcArgs Stage1
             , flag GhcUnregisterised ? arg "-DUSE_MINIINTERPRETER"
             , arg "-Irts"
             , arg "-Iincludes"
-            , arg $ "-I" ++ root -/- generatedDir
+            , arg $ "-I" ++ libPath
             , notM ghcWithSMP ? arg "-DNOSMP"
             , arg "-fcommon" ]
diff --git a/hadrian/src/Settings/Builders/Ghc.hs b/hadrian/src/Settings/Builders/Ghc.hs
index 2db62aa4e1..54315484c1 100644
--- a/hadrian/src/Settings/Builders/Ghc.hs
+++ b/hadrian/src/Settings/Builders/Ghc.hs
@@ -161,7 +161,8 @@ commonGhcArgs :: Args
 commonGhcArgs = do
     way  <- getWay
     path <- getBuildPath
-    ghcVersion <- expr ghcVersionH
+    stage <- getStage
+    ghcVersion <- expr $ ghcVersionH stage
     mconcat [ arg "-hisuf", arg $ hisuf way
             , arg "-osuf" , arg $  osuf way
             , arg "-hcsuf", arg $ hcsuf way
@@ -208,10 +209,11 @@ includeGhcArgs :: Args
 includeGhcArgs = do
     pkg     <- getPackage
     path    <- getBuildPath
-    root    <- getBuildRoot
     context <- getContext
     srcDirs <- getContextData srcDirs
     autogen <- expr $ autogenPath context
+    stage <- getStage
+    libPath <- expr $ stageLibPath stage
     let cabalMacros = autogen -/- "cabal_macros.h"
     expr $ need [cabalMacros]
     mconcat [ arg "-i"
@@ -219,6 +221,6 @@ includeGhcArgs = do
             , arg $ "-i" ++ autogen
             , pure [ "-i" ++ pkgPath pkg -/- dir | dir <- srcDirs ]
             , cIncludeArgs
-            , arg $      "-I" ++ root -/- generatedDir
-            , arg $ "-optc-I" ++ root -/- generatedDir
+            , arg $      "-I" ++ libPath
+            , arg $ "-optc-I" ++ libPath
             , pure ["-optP-include", "-optP" ++ cabalMacros] ]
diff --git a/hadrian/src/Settings/Builders/HsCpp.hs b/hadrian/src/Settings/Builders/HsCpp.hs
index e33061c9d0..4595e2098e 100644
--- a/hadrian/src/Settings/Builders/HsCpp.hs
+++ b/hadrian/src/Settings/Builders/HsCpp.hs
@@ -6,12 +6,12 @@ import Settings.Builders.Common
 hsCppBuilderArgs :: Args
 hsCppBuilderArgs = builder HsCpp ? do
     stage   <- getStage
-    root    <- getBuildRoot
     ghcPath <- expr $ buildPath (vanillaContext stage compiler)
+    libPath <- expr $ stageLibPath stage
     mconcat [ getSettingList HsCppArgs
             , arg "-P"
             , arg "-Iincludes"
-            , arg $ "-I" ++ root -/- generatedDir
+            , arg $ "-I" ++ libPath
             , arg $ "-I" ++ ghcPath
             , arg "-x", arg "c"
             , arg =<< getInput ]