Set up the LLVM context and optimise the module

Now that we have some LLVM IR generated, we can run PassManager on our
module to get a bunch of neat optimisations on it. Try it out with 3 + 2
to see some constant folding.
Note that the original tutorial uses FunctionPassManager which optimises
on a function per function basis: llvm-hs doesn't expose this yet (and
this is all using the legacy pass manager anyway), so for now we just
optimise the entire module at the end.

diff --git a/Main.hs b/Main.hs
index 2a5a7e0fbc6c490b0d90af2da2e54a843138341f..bff1c08c965c037080cc6aba052a60c40f1dc999 100644 (file)
--- a/Main.hs
+++ b/Main.hs
@@ -13,14 +13,25 @@ import LLVM.AST.Float
 import LLVM.AST.FloatingPointPredicate hiding (False, True)
 import LLVM.AST.Operand
 import LLVM.AST.Type as Type
+import LLVM.Context
 import LLVM.IRBuilder
+import LLVM.Module
+import LLVM.PassManager
 import LLVM.Pretty
+import LLVM.Target
 import System.IO
 import System.IO.Error
 import Text.Read (readMaybe)
 
 main :: IO ()
-main = buildModuleT "main" repl >>= Text.hPutStrLn stderr . ("\n" <>) . ppll
+main = do
+  mdl' <- buildModuleT "main" repl
+  withContext $ \ctx -> withHostTargetMachine $ \tm ->
+    withModuleFromAST ctx mdl' $ \mdl -> do
+      let spec = defaultCuratedPassSetSpec { optLevel = Just 3 }
+      -- this returns true if the module was modified
+      withPassManager spec $ flip runPassManager mdl
+      Text.hPutStrLn stderr . ("\n" <>) . ppllvm =<< moduleAST mdl
 
 repl :: ModuleBuilderT IO ()
 repl = do