Miscellany

> module Ex3FunctionsCodeGenerator where
> import Ex3FunctionsTypes
> import List

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Solution for Compilers exercise 3

Paul Kelly  Imperial College London  2006
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Fill in the gaps...

Part (1): translate function declaration
ls

> transFunction :: Function -> [Instr]
> transFunction (Defun fname paramname body)
>  = [Define fname] ++ transExp body allRegs ++ restoreRegs everyReg ++ [Ret]
> everyReg = [D0,D1, D2, D3, D4, D5, D6, D7]
> allRegs = [D1, D2, D3, D4, D5, D6, D7]

Part (2): saving registers

> saveRegs :: [Register] -> [Instr]
> saveRegs regs = map pusher (everyReg \\ regs)



Part (3): translate expression (ie function body, perhaps including
function calls)

> transExp :: Exp -> [Register] -> [Instr]
> transExp (Const x) (dst:rest) = [Mov (ImmNum x)(Reg (dst))]
> transExp (Var varNam) (dst:rest) = [Mov (Reg D0) (Reg (dst))]
> transExp (Minus (exp) (exp1)) (src:rest) | (weight (exp1) > weight (exp)) = transExp(exp1) (src:rest) ++ transExp(exp) (rest) ++ [Sub (Reg (head rest)) (Reg (src))]
>                                          | otherwise = transExp(exp) (src:rest) ++ transExp(exp1) (rest) ++ [Sub (Reg (src)) (Reg (head rest))]
> transExp (Apply (fname) (exp)) (reg:regs) = 	saveRegs (reg:regs) ++ transExp exp (reg:regs) ++  [Jsr fname] ++ [Mov (Reg D1) (Reg (head regs))] ++ restoreRegs (reg:regs)


> weight :: Exp -> Int
> weight (Const x) = 1
> weight (Var varName) = 1 
> weight (Minus exp exp1) |(weight(exp1)< weight(exp)) = 1 + weight (exp1)
>			  | otherwise = 1 + weight (exp)
> weight (Apply fname exp) = 1 + weight(exp)

> restoreRegs :: [Register] -> [Instr]
> restoreRegs regs = map popper (everyReg \\ regs)

> pusher reg = Mov (Reg reg) Push
> popper reg = Mov Pop (Reg reg)