1 files changed, 26 insertions, 29 deletions
diff --git a/compiler.hs b/compiler.hs
index 8a98a2d..eab7058 100644
--- a/compiler.hs
+++ b/compiler.hs
@@ -36,51 +36,48 @@ compile (Program inss) = runLineWriter $ do
     mapM_ compileIns inss
     emit0 epilogue
 
-cursor :: String
-cursor = "rbx"
+cursorReg :: String
+cursorReg = "rbx"
+
+cursorOffset :: Offset -> String
+cursorOffset 0 = cursorReg
+cursorOffset off = cursorReg ++ " + " ++ show off
 
 compileIns :: Instruction -> LineWriter ()
-compileIns (IAdd v off) = emit $ "add byte [" ++ cursor ++ " + " ++ show off ++ "], " ++ show v
-compileIns (ISet v off) = emit $ "mov byte [" ++ cursor ++ " + " ++ show off ++ "], " ++ show v
-compileIns (IMove from []) = do
-    emit $ "mov byte [" ++ cursor ++ " + " ++ show from ++ "], 0"
-compileIns (IMove from [(o,m)]) = do
-    emit $ "mov al, [" ++ cursor ++ " + " ++ show from ++ "]"
-    if m == 1 then return ()
-              else do
-                       emit $ "mov cl, " ++ show m
-                       emit "mul byte cl"
-    emit $ "add [" ++ cursor ++ " + " ++ show o ++ "], al"
-    emit $ "mov byte [" ++ cursor ++ " + " ++ show from ++ "], 0"
-compileIns (IMove from tos) = do
-    emit $ "mov dl, [" ++ cursor ++ " + " ++ show from ++ "]"
-    emit $ "mov byte [" ++ cursor ++ " + " ++ show from ++ "], 0"
-    forM_ tos $ \(o,m) -> do
-        emit "mov al, dl"
-        if m == 1 then return ()
-                  else do
-                           emit $ "mov cl, " ++ show m
-                           emit "mul byte cl"
-        emit $ "add [" ++ cursor ++ " + " ++ show o ++ "], al"
-compileIns (ISlide off) = emit $ "add " ++ cursor ++ ", " ++ show off
+compileIns (IAdd v off) = emit $ "add byte [" ++ cursorOffset off ++ "], " ++ show v
+compileIns (ISet v off) = emit $ "mov byte [" ++ cursorOffset off ++ "], " ++ show v
+compileIns (ICopy _ _ 0) = return ()
+compileIns (ICopy from to m) = do
+    emit $ "mov al, [" ++ cursorOffset from ++ "]"
+    case m of
+        1 -> return ()
+        _ | Just p <- isTwoPower m -> emit $ "shl al, " ++ show p
+          | otherwise -> do
+                             emit $ "mov cl, " ++ show m
+                             emit "mul byte cl"
+    emit $ "add [" ++ cursorOffset to ++ "], al"
+compileIns (ISlide off) = emit $ "add " ++ cursorReg ++ ", " ++ show off
 compileIns (ILoop inss off) = do
     loopid <- genId
-    emit $ "cmp byte [" ++ cursor ++ " + " ++ show off ++ "], 0"
+    emit $ "cmp byte [" ++ cursorOffset off ++ "], 0"
     emit $ "jz .Laf_" ++ show loopid
     emit0 $ ".Lbd_" ++ show loopid ++ ":"
     mapM_ compileIns inss
-    emit $ "cmp byte [" ++ cursor ++ " + " ++ show off ++ "], 0"
+    emit $ "cmp byte [" ++ cursorOffset off ++ "], 0"
     emit $ "jnz .Lbd_" ++ show loopid
     emit0 $ ".Laf_" ++ show loopid ++ ":"
 compileIns (IInput off) = do
     emit "call _getchar"
-    emit $ "mov [" ++ cursor ++ " + " ++ show off ++ "], al"
+    emit $ "mov [" ++ cursorOffset off ++ "], al"
 compileIns (IOutput off) = do
     emit "xor edi, edi"
-    emit $ "mov dil, [" ++ cursor ++ " + " ++ show off ++ "]"
+    emit $ "mov dil, [" ++ cursorOffset off ++ "]"
     emit "call _putchar"
 compileIns IStart = return ()
 
+isTwoPower :: Byte -> Maybe Int
+isTwoPower v = findIndex (==v) (take 8 $ iterate (* 2) 1)
+
 
 prologue :: String
 prologue =