1 files changed, 81 insertions, 0 deletions
diff --git a/Lower.hs b/Lower.hs
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index 0000000..46aaad5
--- /dev/null
+++ b/Lower.hs
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+{-# LANGUAGE TupleSections #-}
+module Lower(lowerIR) where
+
+import AST (Name)
+import Data.List
+import qualified Data.Map.Strict as Map
+import Intermediate
+
+
+-- Not yet regalloc'd
+data AsmProgram' = AsmProgram' [(Label, [AsmInstr'])]
+
+data AsmInstr'
+    = Li Ref Int
+    | Mv Ref Ref
+    | Arith Arith Ref Ref Ref
+    | Not Ref Ref
+    | Call Ref Label
+    | Jcc CCond Ref Label
+    | JccR CCond Ref Ref
+    | Load Int Ref Ref
+    | Store Int Ref Ref
+
+newtype Label = Label String
+
+data Arith = Add | Sub | Mul | Div | Lt | Lte | And | Or | Xor | Sll | Slr | Sar
+
+data CCond = CCZ | CCNZ
+
+type GFDMap = Map.Map Name GlobFuncDef
+
+type BId = Int
+
+
+-- Calling convention:
+-- Upon function entry, the stack should look as follows:
+-- - Closure item 1
+-- - Closure item 2
+-- ...
+-- - Closure item N
+-- - Argument 1
+-- - Arugment 2
+-- ...
+-- - Argument M
+-- - Link register [pushed by callee]
+
+
+lowerIR :: IRProgram -> AsmProgram'
+lowerIR (IRProgram bbs gfds datatbl) =
+    let argcmap = floodArgCount gfds bbs
+    in AsmProgram' [(Label ("BB" ++ show bid), lowerBB bb gfds argcmap)
+                   | bb@(BB bid _ _) <- bbs]
+
+lowerBB :: BB -> GFDMap -> Map.Map BId Int -> [AsmInstr']
+lowerBB (BB bid inss term) gfds argcmap = concatMap (\ins -> lowerIns ins gfds argcmap) inss
+
+lowerIns :: Instruction -> GFDMap -> Map.Map BId Int -> [AsmInstr']
+lowerIns (dest, instruction) gfds argcmap = case instruction of
+    IAssign src -> [Mv dest src]
+    IParam idx  ->  undefined
+
+floodArgCount :: GFDMap -> [BB] -> Map.Map BId Int
+floodArgCount gfds bbs = go Map.empty [(bid, n) | GlobFuncDef bid n _ <- Map.elems gfds]
+  where
+    bbMap :: Map.Map Int BB
+    bbMap = Map.fromList [(bid, bb) | bb@(BB bid _ _) <- bbs]
+
+    go :: Map.Map BId Int -> [(Int, Int)] -> Map.Map BId Int
+    go result frontier =
+        let result' = foldl' (\mp (bid, n) -> Map.insert bid n mp) result frontier
+            frontier' = concat [map (,n) (nexts bid \\ Map.keys result')
+                               | (bid, n) <- frontier]
+        in go result' frontier'
+
+    nexts :: BId -> [BId]
+    nexts bid = case let BB _ _ term = bbMap Map.! bid in term of
+        IBr _ a b -> [a, b]
+        IJmp a    -> [a]
+        IRet _    -> []
+        IExit     -> []
+        IUnknown  -> []