From 71d6ead1c5a14f206f5d7c8d4b9d1cbfed4a90db Mon Sep 17 00:00:00 2001
From: Luke Lau <luke_lau@icloud.com>
Date: Sun, 19 May 2019 15:58:31 +0100
Subject: [PATCH] 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.
---
 Main.hs  | 20 ++++++++++++++++++--
 Utils.hs |  7 +++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/Main.hs b/Main.hs
index 2a5a7e0..c3f9292 100644
--- a/Main.hs
+++ b/Main.hs
@@ -2,6 +2,7 @@
 
 import AST as K -- K for Kaleidoscope
 import Utils
+import Control.Monad.Trans.Class
 import Control.Monad.Trans.Reader
 import Control.Monad.IO.Class
 import Data.String
@@ -13,16 +14,23 @@ 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
+  withContext $ \ctx -> withHostTargetMachineDefault $ \tm -> do
+    ast <- runReaderT (buildModuleT "main" repl) ctx
+    return ()
 
-repl :: ModuleBuilderT IO ()
+repl :: ModuleBuilderT (ReaderT Context IO) ()
 repl = do
   liftIO $ hPutStr stderr "ready> "
   mline <- liftIO $ catchIOError (Just <$> getLine) eofHandler
@@ -34,6 +42,14 @@ repl = do
         Just ast -> do
           hoist $ buildAST ast
           mostRecentDef >>= liftIO . Text.hPutStrLn stderr . ppll
+
+          ast <- moduleSoFar "main"
+          ctx <- lift ask
+          liftIO $ withModuleFromAST ctx ast $ \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
   where
     eofHandler e
diff --git a/Utils.hs b/Utils.hs
index 2a83c35..3bd3b37 100644
--- a/Utils.hs
+++ b/Utils.hs
@@ -4,11 +4,18 @@ Shoving away gross stuff into this one module.
 module Utils where
 
 import Control.Monad.Trans.State
+import Data.ByteString.Short (ShortByteString)
 import Data.Functor.Identity
 import LLVM.AST
 import LLVM.IRBuilder.Module
 import LLVM.IRBuilder.Internal.SnocList
 
+moduleSoFar :: MonadModuleBuilder m => ShortByteString -> m Module
+moduleSoFar nm = do
+  s <- liftModuleState get
+  let ds = getSnocList (builderDefs s)
+  return $ defaultModule { moduleName = nm, moduleDefinitions = ds }
+
 mostRecentDef :: Monad m => ModuleBuilderT m Definition
 mostRecentDef = last . getSnocList . builderDefs <$> liftModuleState get
 
-- 
2.30.2