-- | Generating C calls
module SPARC.CodeGen.CCall (


import SPARC.CodeGen.Gen64
import SPARC.CodeGen.Gen32
import SPARC.CodeGen.Base
import SPARC.Stack
import SPARC.Instr
import SPARC.Imm
import SPARC.Regs
import SPARC.Base
import NCGMonad
import PIC
import Instruction
import Size
import Reg

import Cmm
import CLabel
import BasicTypes

import OrdList
import FastString
import Outputable

   Now the biggest nightmare---calls.  Most of the nastiness is buried in
   @get_arg@, which moves the arguments to the correct registers/stack
   locations.  Apart from that, the code is easy.
   The SPARC calling convention is an absolute
   nightmare.  The first 6x32 bits of arguments are mapped into
   %o0 through %o5, and the remaining arguments are dumped to the
   stack, beginning at [%sp+92].  (Note that %o6 == %sp.)

   If we have to put args on the stack, move %o6==%sp down by
   the number of words to go on the stack, to ensure there's enough space.

   According to Fraser and Hanson's lcc book, page 478, fig 17.2,
   16 words above the stack pointer is a word for the address of
   a structure return value.  I use this as a temporary location
   for moving values from float to int regs.  Certainly it isn't
   safe to put anything in the 16 words starting at %sp, since
   this area can get trashed at any time due to window overflows
   caused by signal handlers.

   A final complication (if the above isn't enough) is that 
   we can't blithely calculate the arguments one by one into
   %o0 .. %o5.  Consider the following nested calls:

       fff a (fff b c)

   Naive code moves a into %o0, and (fff b c) into %o1.  Unfortunately
   the inner call will itself use %o0, which trashes the value put there
   in preparation for the outer call.  Upshot: we need to calculate the
   args into temporary regs, and move those to arg regs or onto the
   stack only immediately prior to the call proper.  Sigh.

    :: CmmCallTarget		-- function to call
    -> HintedCmmFormals		-- where to put the result
    -> HintedCmmActuals		-- arguments (of mixed type)
    -> NatM InstrBlock

-- On SPARC under TSO (Total Store Ordering), writes earlier in the instruction stream
-- are guaranteed to take place before writes afterwards (unlike on PowerPC). 
-- Ref: Section 8.4 of the SPARC V9 Architecture manual.
-- In the SPARC case we don't need a barrier.
genCCall (CmmPrim (MO_WriteBarrier)) _ _
 = do	return nilOL

genCCall target dest_regs argsAndHints 
 = do	 	
	-- strip hints from the arg regs
	let args :: [CmmExpr]
	    args  = map hintlessCmm argsAndHints

	-- work out the arguments, and assign them to integer regs
	argcode_and_vregs	<- mapM arg_to_int_vregs args
	let (argcodes, vregss)	= unzip argcode_and_vregs
	let vregs		= concat vregss

	let n_argRegs		= length allArgRegs
	let n_argRegs_used 	= min (length vregs) n_argRegs

	-- deal with static vs dynamic call targets
	callinsns <- case target of
		CmmCallee (CmmLit (CmmLabel lbl)) _ -> 
			return (unitOL (CALL (Left (litToImm (CmmLabel lbl))) n_argRegs_used False))

		CmmCallee expr _
		 -> do	(dyn_c, [dyn_r]) <- arg_to_int_vregs expr
			return (dyn_c `snocOL` CALL (Right dyn_r) n_argRegs_used False)

		CmmPrim mop 
		 -> do	res	<- outOfLineFloatOp mop
			lblOrMopExpr <- case res of
				Left lbl -> do
					return (unitOL (CALL (Left (litToImm (CmmLabel lbl))) n_argRegs_used False))

		       		Right mopExpr -> do
					(dyn_c, [dyn_r]) <- arg_to_int_vregs mopExpr
					return (dyn_c `snocOL` CALL (Right dyn_r) n_argRegs_used False)

			return lblOrMopExpr

	let argcode = concatOL argcodes

	let (move_sp_down, move_sp_up)
	           = let diff = length vregs - n_argRegs
	                 nn   = if odd diff then diff + 1 else diff -- keep 8-byte alignment
	             in  if   nn <= 0
	                 then (nilOL, nilOL)
	                 else (unitOL (moveSp (-1*nn)), unitOL (moveSp (1*nn)))

        let transfer_code
           	= toOL (move_final vregs allArgRegs extraStackArgsHere)
	 $ 	argcode			`appOL`
		move_sp_down		`appOL`
		transfer_code		`appOL`
		callinsns		`appOL`
		unitOL NOP		`appOL`
		move_sp_up		`appOL`
		assign_code dest_regs

-- | Generate code to calculate an argument, and move it into one
-- 	or two integer vregs.
arg_to_int_vregs :: CmmExpr -> NatM (OrdList Instr, [Reg])
arg_to_int_vregs arg

	-- If the expr produces a 64 bit int, then we can just use iselExpr64
	| isWord64 (cmmExprType arg)
	= do	(ChildCode64 code r_lo) <- iselExpr64 arg
	  	let r_hi 		= getHiVRegFromLo r_lo
		return (code, [r_hi, r_lo])

	| otherwise
	= do	(src, code) 	<- getSomeReg arg
		let pk   	= cmmExprType arg

		case cmmTypeSize pk of

		 -- Load a 64 bit float return value into two integer regs.
		 FF64 -> do
			v1 <- getNewRegNat II32
			v2 <- getNewRegNat II32

			let code2 = 
				code				`snocOL`
		                FMOV FF64 src f0		`snocOL`
		                ST   FF32  f0 (spRel 16)	`snocOL`
		                LD   II32  (spRel 16) v1	`snocOL`
		                ST   FF32  f1 (spRel 16)	`snocOL`
		                LD   II32  (spRel 16) v2

			return	(code2, [v1,v2])

		 -- Load a 32 bit float return value into an integer reg
		 FF32 -> do
			v1 <- getNewRegNat II32
			let code2 =
				code                    	`snocOL`
				ST   FF32  src (spRel 16)  	`snocOL`
				LD   II32  (spRel 16) v1
			return (code2, [v1])

		 -- Move an integer return value into its destination reg.
		 _ -> do
			v1 <- getNewRegNat II32
			let code2 = 
				code				`snocOL`
				OR False g0 (RIReg src) v1
			return (code2, [v1])

-- | Move args from the integer vregs into which they have been 
-- 	marshalled, into %o0 .. %o5, and the rest onto the stack.
move_final :: [Reg] -> [Reg] -> Int -> [Instr]

-- all args done
move_final [] _ _
	= []

-- out of aregs; move to stack
move_final (v:vs) [] offset     
	= ST II32 v (spRel offset)
	: move_final vs [] (offset+1)

-- move into an arg (%o[0..5]) reg
move_final (v:vs) (a:az) offset 
	= OR False g0 (RIReg v) a
	: move_final vs az offset

-- | Assign results returned from the call into their 
--	desination regs.
assign_code :: [CmmHinted LocalReg] -> OrdList Instr

assign_code []	= nilOL

assign_code [CmmHinted dest _hint]	
 = let	rep	= localRegType dest
	width	= typeWidth rep
	r_dest 	= getRegisterReg (CmmLocal dest)

		| isFloatType rep 
		, W32	<- width
		= unitOL $ FMOV FF32 (regSingle $ fReg 0) r_dest

		| isFloatType rep
		, W64	<- width
		= unitOL $ FMOV FF64 (regSingle $ fReg 0) r_dest

		| not $ isFloatType rep
		, W32	<- width
		= unitOL $ mkRegRegMoveInstr (regSingle $ oReg 0) r_dest

		| not $ isFloatType rep
		, W64		<- width
		, r_dest_hi	<- getHiVRegFromLo r_dest
		= toOL 	[ mkRegRegMoveInstr (regSingle $ oReg 0) r_dest_hi
			, mkRegRegMoveInstr (regSingle $ oReg 1) r_dest]

		| otherwise
		= panic "SPARC.CodeGen.GenCCall: no match"
   in	result

assign_code _
	= panic "SPARC.CodeGen.GenCCall: no match"

-- | Generate a call to implement an out-of-line floating point operation
	:: CallishMachOp 
	-> NatM (Either CLabel CmmExpr)

outOfLineFloatOp mop 
 = do	let functionName
 		= outOfLineFloatOp_table mop
 	dflags	<- getDynFlagsNat
	mopExpr <- cmmMakeDynamicReference dflags addImportNat CallReference 
		$  mkForeignLabel functionName Nothing True IsFunction

	let mopLabelOrExpr 
		= case mopExpr of
			CmmLit (CmmLabel lbl) 	-> Left lbl
                        _ 			-> Right mopExpr

	return mopLabelOrExpr

-- | Decide what C function to use to implement a CallishMachOp
	:: CallishMachOp
	-> FastString
outOfLineFloatOp_table mop
 = case mop of
	MO_F32_Exp    -> fsLit "expf"
	MO_F32_Log    -> fsLit "logf"
	MO_F32_Sqrt   -> fsLit "sqrtf"
	MO_F32_Pwr    -> fsLit "powf"

	MO_F32_Sin    -> fsLit "sinf"
	MO_F32_Cos    -> fsLit "cosf"
	MO_F32_Tan    -> fsLit "tanf"

	MO_F32_Asin   -> fsLit "asinf"
	MO_F32_Acos   -> fsLit "acosf"
	MO_F32_Atan   -> fsLit "atanf"

	MO_F32_Sinh   -> fsLit "sinhf"
	MO_F32_Cosh   -> fsLit "coshf"
	MO_F32_Tanh   -> fsLit "tanhf"

	MO_F64_Exp    -> fsLit "exp"
	MO_F64_Log    -> fsLit "log"
	MO_F64_Sqrt   -> fsLit "sqrt"
	MO_F64_Pwr    -> fsLit "pow"

	MO_F64_Sin    -> fsLit "sin"
	MO_F64_Cos    -> fsLit "cos"
	MO_F64_Tan    -> fsLit "tan"

	MO_F64_Asin   -> fsLit "asin"
	MO_F64_Acos   -> fsLit "acos"
	MO_F64_Atan   -> fsLit "atan"

	MO_F64_Sinh   -> fsLit "sinh"
	MO_F64_Cosh   -> fsLit "cosh"
	MO_F64_Tanh   -> fsLit "tanh"

	_ -> pprPanic "outOfLineFloatOp(sparc): Unknown callish mach op "
              		(pprCallishMachOp mop)