From 4d4c0e626e0002e19345a1fd47145c1701583d4c Mon Sep 17 00:00:00 2001
From: Luke Lau <luke_lau@icloud.com>
Date: Sun, 2 Jun 2019 19:33:35 +0100
Subject: [PATCH] Find our JIT'ed function and run it

Here is where the magic happens. We first mangle the symbol before
passing it to findSymbolIn: The compilation then happens here. It will
spit back a FFI pointer, which we then need to invoke ourselves.

In order to do this we have to specify the Haskell type of the function
that we're pointing to, which resides in C-land, hence the ccall
attribute in our foreign declaration.

Try it out!
---
 Main.hs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Main.hs b/Main.hs
index 5bc3a3e..48d93a2 100644
--- a/Main.hs
+++ b/Main.hs
@@ -9,6 +9,7 @@ import Control.Monad.IO.Class
 import Data.String
 import qualified Data.Map as Map
 import qualified Data.Text.Lazy.IO as Text
+import Foreign.Ptr
 import LLVM.AST.AddrSpace
 import LLVM.AST.Constant
 import LLVM.AST.Float
@@ -27,6 +28,8 @@ import System.IO
 import System.IO.Error
 import Text.Read (readMaybe)
 
+foreign import ccall "dynamic" mkFun :: FunPtr (IO Double) -> IO Double
+
 data JITEnv = JITEnv
   { jitEnvContext :: Context
   , jitEnvCompileLayer :: IRCompileLayer ObjectLinkingLayer
@@ -84,7 +87,9 @@ repl = do
 jit :: JITEnv -> Module -> IO Double
 jit JITEnv{jitEnvCompileLayer=compLayer, jitEnvModuleKey=mdlKey} mdl =
   withModule compLayer mdlKey mdl $ do
-    return 0
+    mangled <- mangleSymbol compLayer "__anon_expr"
+    Right (JITSymbol fPtr _) <- findSymbolIn compLayer mdlKey mangled False
+    mkFun (castPtrToFunPtr (wordPtrToPtr fPtr))
 
 type Binds = Map.Map String Operand
 
-- 
2.30.2