hadrian: Add omit_pragmas transformerwip/hadrian-interface-transformer

This transformer builds stage2 GHC with -fomit-interface-pragmas which
can greatly reduce the amount of rebuilding but still allows most the
tests to pass.

1 files changed, 8 insertions, 0 deletions

diff --git a/hadrian/src/Flavour.hs b/hadrian/src/Flavour.hs
index 61bca98053..d8f34347f4 100644
--- a/hadrian/src/Flavour.hs
+++ b/hadrian/src/Flavour.hs
@@ -43,6 +43,7 @@ flavourTransformers = M.fromList
     , "profiled_ghc" =: enableProfiledGhc
     , "no_dynamic_ghc" =: disableDynamicGhcPrograms
     , "no_profiled_libs" =: disableProfiledLibs
+    , "omit_pragmas" =: omitPragmas
     ]
   where (=:) = (,)
 
@@ -179,6 +180,13 @@ disableProfiledLibs :: Flavour -> Flavour
 disableProfiledLibs flavour =
     flavour { libraryWays = filter (not . wayUnit Profiling) <$> libraryWays flavour }
 
+-- | Build stage2 compiler with -fomit-interface-pragmas to reduce
+-- recompilation.
+omitPragmas :: Flavour -> Flavour
+omitPragmas =
+  let Right kv = parseKV "stage1.ghc.ghc.hs.opts += -fomit-interface-pragmas"
+      Right transformer = applySetting kv
+  in transformer
 
 -- * CLI and <root>/hadrian.settings options