Add 'hadrian/' from commit '45f3bff7016a2a0cd9a5455a882ced984655e90b'

git-subtree-dir: hadrian
git-subtree-mainline: 575b35f4cdc18045bccd42d341d6f25d95c0696c
git-subtree-split: 45f3bff7016a2a0cd9a5455a882ced984655e90b

1 files changed, 26 insertions, 0 deletions

diff --git a/hadrian/src/Target.hs b/hadrian/src/Target.hs
new file mode 100644
index 0000000000..30c8d98d14
--- /dev/null
+++ b/hadrian/src/Target.hs
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+module Target (
+    Target, target, context, builder, inputs, outputs, trackArgument,
+    module Builder
+    ) where
+
+import Data.Char
+import Data.List.Extra
+
+import qualified Hadrian.Target as H
+import Hadrian.Target hiding (Target)
+
+import Builder
+import Context
+
+type Target = H.Target Context Builder
+
+-- | Some arguments do not affect build results and therefore do not need to be
+-- tracked by the build system. A notable example is "-jN" that controls Make's
+-- parallelism. Given a 'Target' and an argument, this function should return
+-- 'True' only if the argument needs to be tracked.
+trackArgument :: Target -> String -> Bool
+trackArgument target arg = case builder target of
+    (Make _) -> not $ threadArg arg
+    _        -> True
+  where
+    threadArg s = dropWhileEnd isDigit s `elem` ["-j", "MAKEFLAGS=-j", "THREADS="]