hadrian: add flag to skip rebuilding dependency information #17636

4 files changed, 30 insertions, 3 deletions

diff --git a/hadrian/README.md b/hadrian/README.md
index 6a9346b997..d0ab7a274d 100644
--- a/hadrian/README.md
+++ b/hadrian/README.md
@@ -104,6 +104,8 @@ simply drop the `--freeze1` flag and Hadrian will rebuild all out-of-date files.
 * `--freeze2`: just like `--freeze1` but tell Hadrian to additionally freeze
 Stage2 GHC.
 
+* `--skip-depends`: skips rebuilding Haskell module dependency files.
+
 * `--integer-simple`: build GHC using the `integer-simple` integer library
 (instead of `integer-gmp`).
 
diff --git a/hadrian/doc/make.md b/hadrian/doc/make.md
index 318b736fa5..b047baed1d 100644
--- a/hadrian/doc/make.md
+++ b/hadrian/doc/make.md
@@ -208,3 +208,17 @@ time you fire up a build. This is not possible with the Make build system.
   # Hadrian
   build nofib # builds the compiler and everything we need if necessary, too
   ```
+
+- `make FAST=YES`
+
+  Partially supported in hadrian with the `--skip-depends` argument. Since
+  hadrian is not directory aware some of the features of `FAST=YES` are not
+  replicated.
+
+  ```sh
+  # Make
+  make FAST=YES
+
+  # Hadrian
+  build --skip-depends
+  ```
diff --git a/hadrian/src/CommandLine.hs b/hadrian/src/CommandLine.hs
index 4582a8b258..080c4a2f6c 100644
--- a/hadrian/src/CommandLine.hs
+++ b/hadrian/src/CommandLine.hs
@@ -1,5 +1,5 @@
 module CommandLine (
-    optDescrs, cmdLineArgsMap, cmdFlavour, lookupFreeze1, lookupFreeze2,
+    optDescrs, cmdLineArgsMap, cmdFlavour, lookupFreeze1, lookupFreeze2, lookupSkipDepends,
     cmdBignum, cmdBignumCheck, cmdProgressInfo, cmdConfigure, cmdCompleteSetting,
     cmdDocsArgs, lookupBuildRoot, TestArgs(..), TestSpeed(..), defaultTestArgs,
     cmdPrefix
@@ -26,6 +26,7 @@ data CommandLineArgs = CommandLineArgs
     , flavour        :: Maybe String
     , freeze1        :: Bool
     , freeze2        :: Bool
+    , skipDepends    :: Bool
     , bignum         :: Maybe String
     , bignumCheck    :: Bool
     , progressInfo   :: ProgressInfo
@@ -43,6 +44,7 @@ defaultCommandLineArgs = CommandLineArgs
     , flavour        = Nothing
     , freeze1        = False
     , freeze2        = False
+    , skipDepends    = False
     , bignum         = Nothing
     , bignumCheck    = False
     , progressInfo   = Brief
@@ -114,9 +116,10 @@ readBuildRoot ms =
     set :: BuildRoot -> CommandLineArgs -> CommandLineArgs
     set flag flags = flags { buildRoot = flag }
 
-readFreeze1, readFreeze2 :: Either String (CommandLineArgs -> CommandLineArgs)
+readFreeze1, readFreeze2, readSkipDepends :: Either String (CommandLineArgs -> CommandLineArgs)
 readFreeze1 = Right $ \flags -> flags { freeze1 = True }
 readFreeze2 = Right $ \flags -> flags { freeze1 = True, freeze2 = True }
+readSkipDepends = Right $ \flags -> flags { skipDepends = True }
 
 readProgressInfo :: Maybe String -> Either String (CommandLineArgs -> CommandLineArgs)
 readProgressInfo ms =
@@ -256,6 +259,8 @@ optDescrs =
       "Freeze Stage1 GHC."
     , Option [] ["freeze2"] (NoArg readFreeze2)
       "Freeze Stage2 GHC."
+    , Option [] ["skip-depends"] (NoArg readSkipDepends)
+      "Skip rebuilding dependency information."
     , Option [] ["bignum"] (OptArg readBignum "BIGNUM")
       "Select GHC BigNum backend: native, gmp, ffi."
     , Option [] ["progress-info"] (OptArg readProgressInfo "STYLE")
@@ -361,6 +366,9 @@ lookupFreeze1 = freeze1 . lookupExtra defaultCommandLineArgs
 lookupFreeze2 :: Map.HashMap TypeRep Dynamic -> Bool
 lookupFreeze2 = freeze2 . lookupExtra defaultCommandLineArgs
 
+lookupSkipDepends :: Map.HashMap TypeRep Dynamic -> Bool
+lookupSkipDepends = skipDepends . lookupExtra defaultCommandLineArgs
+
 cmdBignum :: Action (Maybe String)
 cmdBignum = bignum <$> cmdLineArgs
 
diff --git a/hadrian/src/Main.hs b/hadrian/src/Main.hs
index 632b742624..bc04c707d8 100644
--- a/hadrian/src/Main.hs
+++ b/hadrian/src/Main.hs
@@ -35,7 +35,10 @@ main = do
                   ] ++
                   [ (RebuildLater, buildRoot -/- "stage1/**")
                   | CommandLine.lookupFreeze2 argsMap
-                  ]
+                  ] ++
+                  (if CommandLine.lookupSkipDepends argsMap
+                   then [(RebuildLater, buildRoot -/- "**/.dependencies.mk"), (RebuildLater, buildRoot -/- "**/.dependencies")]
+                   else [])
 
     cwd <- getCurrentDirectory
     shakeColor <- shouldUseColor