From: Luke Lau <luke_lau@icloud.com>
Date: Sun, 2 Jun 2019 18:33:35 +0000 (+0100)
Subject: Find our JIT'ed function and run it
X-Git-Url: http://git.lukelau.me/?p=kaleidoscope-hs.git;a=commitdiff_plain;h=bc95ec9770ea2b19dd773dd4cec05d61b4684e95

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!
---

diff --git a/Main.hs b/Main.hs
index bc7c307..468573d 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
@@ -83,8 +86,10 @@ repl = do
 
 jit :: JITEnv -> Module -> IO Double
 jit JITEnv{jitEnvCompileLayer=compLayer, jitEnvModuleKey=mdlKey} mdl =
-  withModule compLayer mdlKey mdl $
-    return 0
+  withModule compLayer mdlKey mdl $ do
+    mangled <- mangleSymbol compLayer "__anon_expr"
+    Right (JITSymbol fPtr _) <- findSymbolIn compLayer mdlKey mangled False
+    mkFun (castPtrToFunPtr (wordPtrToPtr fPtr))
 
 type Binds = Map.Map String Operand