Add Deref Mut cursor in L3 IR

gibbon-compiler/src/Gibbon/L3/Syntax.hs

@@ -100,6 +100,12 @@ data E3Ext loc dec =
   | SSPop SSModality Var Var
   | Assert (PreExp E3Ext loc dec) -- ^ Translates to assert statements in C.
     -- ^ Analogous to L2's extensions.
+    -- Instroduce some new IR for mutable cursors 
+  | DerefMutableCursor Var -- ^ Read a mutable cursor, maybe this should be names to ReadMutableCursor etc. 
+                           -- Returns a CursorTy type
+
+
+
   deriving (Show, Ord, Eq, Read, Generic, NFData)
 
 instance FreeVars (E3Ext l d) where

gibbon-compiler/src/Gibbon/Passes/Cursorize.hs

@@ -406,7 +406,26 @@ cursorizeExp ddfs fundefs denv tenv senv ex =
         LetParRegionE reg sz _ bod -> do
           mkLets (regionToBinds True reg sz) <$> go bod
 
-        BoundsCheck i bound cur -> return $ Ext $ L3.BoundsCheck i (toLocVar bound) (toLocVar cur)
+        BoundsCheck i bound cur -> do
+                                   case (isMutableCursorTy bound, isMutableCursorTy cur) of 
+                                        (True, True)   -> do 
+                                                          bound' <- gensym "newDerefBound"
+                                                          cur' <- gensym "newDerefCur"
+                                                          let newBoundCheckExpr = Ext $ L3.BoundsCheck i bound' cur'
+                                                          exp' <- genReadMutableCursor bound newBoundCheckExpr bound' 
+                                                          exp'' <- genReadMutableCursor cur exp' cur'
+                                                          return $ exp''
+                                        (False, True)  -> do 
+                                                          cur' <- gensym "newDerefCur"
+                                                          let newBoundCheckExpr = Ext $ L3.BoundsCheck i (toLocVar bound) cur'
+                                                          exp' <- genReadMutableCursor cur newBoundCheckExpr cur'
+                                                          return $ exp'
+                                        (True, False)  -> do 
+                                                          bound' <- gensym "newDerefBound"
+                                                          let newBoundCheckExpr = Ext $ L3.BoundsCheck i bound' (toLocVar cur)
+                                                          exp' <- genReadMutableCursor bound newBoundCheckExpr bound' 
+                                                          return $ exp'
+                                        (False, False) -> return $ Ext $ L3.BoundsCheck i (toLocVar bound) (toLocVar cur)
 
         FromEndE{} -> error $ "cursorizeExp: TODO FromEndE" ++ sdoc ext
 
@@ -430,6 +449,24 @@ cursorizeExp ddfs fundefs denv tenv senv ex =
     go = cursorizeExp ddfs fundefs denv tenv senv
 
 
+-- genDerefOrVar :: LocArg -> Exp3 -> Var -> PassM (Either Var Exp3)
+-- genDerefOrVar locArg bod var = case isMutableCursorTy locArg of 
+--                                   True -> genReadMutableCursor locArg bod 
+--                                   False -> 
+
+isMutableCursorTy :: LocArg -> Bool 
+isMutableCursorTy locArg = case locArg of 
+                                  Loc LREM{lremLoc, lremReg, lremEndReg, lremMode} -> case lremMode of 
+                                                                                          OutputMutable -> True 
+                                                                                          _ -> False
+                                  _ -> False
+
+genReadMutableCursor :: LocArg -> Exp3 -> Var -> PassM Exp3
+genReadMutableCursor locArg bod newCursor = do
+                                  let derefCursorExp = Ext $ L3.DerefMutableCursor (toLocVar locArg)
+                                  return $ LetE (newCursor, [], CursorTy, derefCursorExp) bod
+
+
 -- Cursorize expressions producing `Packed` values
 cursorizePackedExp :: DDefs Ty2 -> FunDefs2 -> DepEnv -> TyEnv Ty2 -> SyncEnv -> Exp2
                    -> PassM (DiExp Exp3)