From 3c40705b60d40f4c863c72091b3b4f30ff79c916 Mon Sep 17 00:00:00 2001
From: Tom Smeding <tom.smeding@gmail.com>
Date: Wed, 24 Apr 2019 15:17:09 +0200
Subject: Prepare for setting up register spilling

---
 Lower.hs | 49 +++++++++++++++++++++++++------------------------
 1 file changed, 25 insertions(+), 24 deletions(-)

diff --git a/Lower.hs b/Lower.hs
index cde2e2b..778193b 100644
--- a/Lower.hs
+++ b/Lower.hs
@@ -1,13 +1,3 @@
--- TODO
--- Use the link register, R14, for the frame pointer (i.e. points to the
--- link register stack slot, from which argument positions are independent
--- of spill space). Upon a function call, the frame pointer needs to be
--- pushed because R14 is overwritten by the call. The value 8 can be
--- obtained each time through a Li on a new temporary.
--- If that works out to be impossible, use R12 as the constant 8.
-
-
-
 {-# LANGUAGE TupleSections, MultiWayIf, GeneralizedNewtypeDeriving #-}
 module Lower(lowerIR) where
 
@@ -23,7 +13,7 @@ data AsmProgram' = AsmProgram' [(Label, [AsmInstr'])]
   deriving (Show)
 
 data AsmInstr'
-    = Li ARef Int
+    = Li ARef Immediate
     | Mv ARef ARef
     | Arith Arith ARef ARef ARef
     | Not ARef ARef
@@ -33,6 +23,10 @@ data AsmInstr'
     -- Load/Store: 'Int' is number of BYTES.
     | Load Int ARef ARef
     | Store Int ARef ARef
+    -- Macro's that will be instantiated with code to set up and clean up
+    -- the register spill space. Will use R14 as temporary.
+    | SetupSpill
+    | CleanupSpill
   deriving (Show)
 
 data ARef
@@ -43,6 +37,11 @@ data ARef
     | ANone
   deriving (Show)
 
+data Immediate
+    = Imm Int
+    | FPOffset Int
+  deriving (Show)
+
 newtype Label = Label String
   deriving (Show)
 
@@ -148,7 +147,7 @@ lowerIns (dest, instruction) gfds = case instruction of
 
     IParam idx -> do
         offsetr <- genTemp
-        return [Li offsetr (8 * (idx + 1))
+        return [Li offsetr (FPOffset (8 * (idx + 1)))
                ,Arith Add offsetr offsetr (ASysReg 15)
                ,Load 8 (toARefStore dest) offsetr]
 
@@ -181,12 +180,12 @@ lowerIns (dest, instruction) gfds = case instruction of
         -- push arg1
         -- call [closurer]
         -- add rsp, (8 * N)
-        -- add rsp, rcx
+        -- add rsp, [closurer + 8]
         -- mov dest, rax
 
         return $
             inss1 ++ inss2 ++
-            [Li eightr 8
+            [Li eightr (Imm 8)
             -- Copy the closure parameters: first make space
             ,Arith Add walkr closurer eightr
             ,Load 8 numitemsr walkr
@@ -202,7 +201,7 @@ lowerIns (dest, instruction) gfds = case instruction of
             ,Arith Sub (ASysReg 15) (ASysReg 15) eightr
             ,Store 8 (ASysReg 15) closurebufr
             ,Jcc CCNZ (ASysReg 0) (Label "__builtin_memcpy")
-            ,Li twentyfourr 24
+            ,Li twentyfourr (Imm 24)
             ,Arith Add (ASysReg 15) (ASysReg 15) twentyfourr] ++
             -- Copy the function parameters
             concat [[Arith Sub (ASysReg 15) (ASysReg 15) eightr
@@ -213,7 +212,7 @@ lowerIns (dest, instruction) gfds = case instruction of
             ,Arith Add (ASysReg 14) (ASysReg 0) eightr
             ,JccR CCNZ (ASysReg 0) funptrr
             -- Clean up the stack
-            ,Li stackshiftr (8 * length argrs)
+            ,Li stackshiftr (Imm (8 * length argrs))
             ,Arith Add stackshiftr stackshiftr numbytesr
             ,Arith Add (ASysReg 15) (ASysReg 15) stackshiftr
             ,Mv (toARefStore dest) (ASysReg 13)]
@@ -234,17 +233,17 @@ lowerIns (dest, instruction) gfds = case instruction of
                     (inss, refs') <- toARefs refs
                     return $
                         inss ++
-                        [Li eightr 8
+                        [Li eightr (Imm 8)
                         -- First call malloc to obtain an allocation
                         ,Arith Sub (ASysReg 15) (ASysReg 15) eightr
-                        ,Li allocsizer (16 + 8 * length refs)
+                        ,Li allocsizer (Imm (16 + 8 * length refs))
                         ,Store 8 (ASysReg 15) allocsizer
                         ,Jcc CCNZ (ASysReg 0) (Label "__builtin_malloc")
                         ,Mv destr (ASysReg 13)
                         -- Then put the right data in the closure allocation
                         ,Store 8 destr (ALabel ("BB" ++ show initBId))
                         ,Arith Add itemr destr eightr
-                        ,Li numitemsr (length refs')
+                        ,Li numitemsr (Imm (length refs'))
                         ,Store 8 itemr numitemsr] ++
                         concat [[Arith Add itemr itemr eightr, Store 8 itemr ref]
                                | ref <- refs']
@@ -253,12 +252,13 @@ lowerIns (dest, instruction) gfds = case instruction of
         return []
 
     IFunctionEntry -> do
-        -- We need to push the link register
+        -- We need to push the link register and set up the spill space
         eightr <- genTemp
         return
-            [Li eightr 8
+            [Li eightr (Imm 8)
             ,Arith Sub (ASysReg 15) (ASysReg 15) eightr
-            ,Store 8 (ASysReg 15) (ASysReg 14)]
+            ,Store 8 (ASysReg 15) (ASysReg 14)
+            ,SetupSpill]
 
 lowerTerm :: Terminator -> LM [AsmInstr']
 lowerTerm terminator = case terminator of
@@ -279,8 +279,9 @@ lowerTerm terminator = case terminator of
         return $
             inss ++
             [Mv (ASysReg 13) valr
+            ,CleanupSpill
             ,Load 8 ptrr (ASysReg 15)
-            ,Li eightr 8
+            ,Li eightr (Imm 8)
             ,Arith Add (ASysReg 15) (ASysReg 15) eightr
             ,JccR CCNZ (ASysReg 0) ptrr]
 
@@ -300,7 +301,7 @@ lowerBuiltin (RSClo "+") [arg1, arg2] = Just $ do
 lowerBuiltin _ _ = Nothing
 
 toARef :: Ref -> LM ([AsmInstr'], ARef)
-toARef (RConst val) = genTemp >>= \r -> return ([Li r val], r)
+toARef (RConst val) = genTemp >>= \r -> return ([Li r (Imm val)], r)
 toARef ref = return ([], toARefStore ref)
 
 toARefs :: [Ref] -> LM ([AsmInstr'], [ARef])
-- 
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