path: root/ghc/compiler/codeGen/CgCallConv.hs

-----------------------------------------------------------------------------
--
--		CgCallConv
--
-- The datatypes and functions here encapsulate the 
-- calling and return conventions used by the code generator.
--
-- (c) The University of Glasgow 2004
--
-----------------------------------------------------------------------------


module CgCallConv (
	-- Argument descriptors
	mkArgDescr, argDescrType,

	-- Liveness
	isBigLiveness, buildContLiveness, mkRegLiveness, 
	smallLiveness, mkLivenessCLit,

	-- Register assignment
	assignCallRegs, assignReturnRegs, assignPrimOpCallRegs,

	-- Calls
	constructSlowCall, slowArgs, slowCallPattern,

	-- Returns
	CtrlReturnConvention(..),
	ctrlReturnConvAlg,
	dataReturnConvPrim,
	getSequelAmode
    ) where

#include "HsVersions.h"

import CgUtils		( emitRODataLits, mkWordCLit )
import CgMonad

import Constants	( mAX_FAMILY_SIZE_FOR_VEC_RETURNS,
			  mAX_Vanilla_REG, mAX_Float_REG,
			  mAX_Double_REG, mAX_Long_REG,
			  mAX_Real_Vanilla_REG, mAX_Real_Float_REG,
			  mAX_Real_Double_REG, mAX_Real_Long_REG,
			  bITMAP_BITS_SHIFT
			)

import ClosureInfo	( ArgDescr(..), Liveness(..) )
import CgStackery	( getSpRelOffset )
import SMRep
import MachOp		( wordRep )
import Cmm		( CmmExpr(..), GlobalReg(..), CmmLit(..), CmmReg(..), node )
import CmmUtils		( mkLblExpr )
import CLabel
import Maybes		( mapCatMaybes )
import Id		( Id )
import Name		( Name )
import TyCon		( TyCon, tyConFamilySize )
import Bitmap		( Bitmap, mAX_SMALL_BITMAP_SIZE, 
			  mkBitmap, intsToReverseBitmap )
import Util		( isn'tIn, sortLe )
import StaticFlags	( opt_Unregisterised )
import FastString	( LitString )
import Outputable
import DATA_BITS


-------------------------------------------------------------------------
--
--	Making argument descriptors
--
--  An argument descriptor describes the layout of args on the stack,
--  both for 	* GC (stack-layout) purposes, and 
--		* saving/restoring registers when a heap-check fails
--
-- Void arguments aren't important, therefore (contrast constructSlowCall)
--
-------------------------------------------------------------------------

-- bring in ARG_P, ARG_N, etc.
#include "../includes/StgFun.h"

-------------------------
argDescrType :: ArgDescr -> Int
-- The "argument type" RTS field type
argDescrType (ArgSpec n) = n
argDescrType (ArgGen liveness)
  | isBigLiveness liveness = ARG_GEN_BIG
  | otherwise		   = ARG_GEN


mkArgDescr :: Name -> [Id] -> FCode ArgDescr
mkArgDescr nm args 
  = case stdPattern arg_reps of
	Just spec_id -> return (ArgSpec spec_id)
	Nothing      -> do { liveness <- mkLiveness nm size bitmap
			   ; return (ArgGen liveness) }
  where
    arg_reps = filter nonVoidArg (map idCgRep args)
	-- Getting rid of voids eases matching of standard patterns

    bitmap   = mkBitmap arg_bits
    arg_bits = argBits arg_reps
    size     = length arg_bits

argBits :: [CgRep] -> [Bool]	-- True for non-ptr, False for ptr
argBits [] 		= []
argBits (PtrArg : args) = False : argBits args
argBits (arg    : args) = take (cgRepSizeW arg) (repeat True) ++ argBits args

stdPattern :: [CgRep] -> Maybe Int
stdPattern [PtrArg]    = Just ARG_P
stdPattern [FloatArg]  = Just ARG_F
stdPattern [DoubleArg] = Just ARG_D
stdPattern [LongArg]   = Just ARG_L
stdPattern [NonPtrArg] = Just ARG_N
	 
stdPattern [NonPtrArg,NonPtrArg] = Just ARG_NN
stdPattern [NonPtrArg,PtrArg]    = Just ARG_NP
stdPattern [PtrArg,NonPtrArg]    = Just ARG_PN
stdPattern [PtrArg,PtrArg]       = Just ARG_PP

stdPattern [NonPtrArg,NonPtrArg,NonPtrArg] = Just ARG_NNN
stdPattern [NonPtrArg,NonPtrArg,PtrArg]    = Just ARG_NNP
stdPattern [NonPtrArg,PtrArg,NonPtrArg]    = Just ARG_NPN
stdPattern [NonPtrArg,PtrArg,PtrArg]	   = Just ARG_NPP
stdPattern [PtrArg,NonPtrArg,NonPtrArg]    = Just ARG_PNN
stdPattern [PtrArg,NonPtrArg,PtrArg]	   = Just ARG_PNP
stdPattern [PtrArg,PtrArg,NonPtrArg]	   = Just ARG_PPN
stdPattern [PtrArg,PtrArg,PtrArg]	   = Just ARG_PPP
	 
stdPattern [PtrArg,PtrArg,PtrArg,PtrArg]	       = Just ARG_PPPP
stdPattern [PtrArg,PtrArg,PtrArg,PtrArg,PtrArg]        = Just ARG_PPPPP
stdPattern [PtrArg,PtrArg,PtrArg,PtrArg,PtrArg,PtrArg] = Just ARG_PPPPPP
stdPattern other = Nothing


-------------------------------------------------------------------------
--
--	Liveness info
--
-------------------------------------------------------------------------

mkLiveness :: Name -> Int -> Bitmap -> FCode Liveness
mkLiveness name size bits
  | size > mAX_SMALL_BITMAP_SIZE		-- Bitmap does not fit in one word
  = do	{ let lbl = mkBitmapLabel name
	; emitRODataLits lbl ( mkWordCLit (fromIntegral size)
		             : map mkWordCLit bits)
	; return (BigLiveness lbl) }
  
  | otherwise		-- Bitmap fits in one word
  = let
        small_bits = case bits of 
			[]  -> 0
			[b] -> fromIntegral b
			_   -> panic "livenessToAddrMode"
    in
    return (smallLiveness size small_bits)

smallLiveness :: Int -> StgWord -> Liveness
smallLiveness size small_bits = SmallLiveness bits
  where bits = fromIntegral size .|. (small_bits `shiftL` bITMAP_BITS_SHIFT)

-------------------
isBigLiveness :: Liveness -> Bool
isBigLiveness (BigLiveness _)   = True
isBigLiveness (SmallLiveness _) = False

-------------------
mkLivenessCLit :: Liveness -> CmmLit
mkLivenessCLit (BigLiveness lbl)    = CmmLabel lbl
mkLivenessCLit (SmallLiveness bits) = mkWordCLit bits


-------------------------------------------------------------------------
--
--		Bitmap describing register liveness
--		across GC when doing a "generic" heap check
--		(a RET_DYN stack frame).
--
-- NB. Must agree with these macros (currently in StgMacros.h): 
-- GET_NON_PTRS(), GET_PTRS(), GET_LIVENESS().
-------------------------------------------------------------------------

mkRegLiveness :: [(Id, GlobalReg)] -> Int -> Int -> StgWord
mkRegLiveness regs ptrs nptrs
  = (fromIntegral nptrs `shiftL` 16) .|. 
    (fromIntegral ptrs  `shiftL` 24) .|.
    all_non_ptrs `xor` reg_bits regs
  where
    all_non_ptrs = 0xff

    reg_bits [] = 0
    reg_bits ((id, VanillaReg i) : regs) | isFollowableArg (idCgRep id)
  	= (1 `shiftL` (i - 1)) .|. reg_bits regs
    reg_bits (_ : regs)
	= reg_bits regs
  
-------------------------------------------------------------------------
--
--		Pushing the arguments for a slow call
--
-------------------------------------------------------------------------

-- For a slow call, we must take a bunch of arguments and intersperse
-- some stg_ap_<pattern>_ret_info return addresses.
constructSlowCall :: [(CgRep,CmmExpr)] -> (CLabel, [(CgRep,CmmExpr)])
   -- don't forget the zero case
constructSlowCall [] 
  = (stg_ap_0, [])
  where
    stg_ap_0 = enterRtsRetLabel SLIT("stg_ap_0")

constructSlowCall amodes
  = (stg_ap_pat, these ++ slowArgs rest)
  where 
    stg_ap_pat = enterRtsRetLabel arg_pat
    (arg_pat, these, rest) = matchSlowPattern amodes

enterRtsRetLabel arg_pat
  | tablesNextToCode = mkRtsRetInfoLabel arg_pat
  | otherwise        = mkRtsRetLabel arg_pat

-- | 'slowArgs' takes a list of function arguments and prepares them for
-- pushing on the stack for "extra" arguments to a function which requires
-- fewer arguments than we currently have.
slowArgs :: [(CgRep,CmmExpr)] -> [(CgRep,CmmExpr)]
slowArgs [] = []
slowArgs amodes = (NonPtrArg, mkLblExpr stg_ap_pat) : args ++ slowArgs rest
  where	(arg_pat, args, rest) = matchSlowPattern amodes
	stg_ap_pat = mkRtsRetInfoLabel arg_pat
  
matchSlowPattern :: [(CgRep,CmmExpr)] 
		 -> (LitString, [(CgRep,CmmExpr)], [(CgRep,CmmExpr)])
matchSlowPattern amodes = (arg_pat, these, rest)
  where (arg_pat, n)  = slowCallPattern (map fst amodes)
	(these, rest) = splitAt n amodes

-- These cases were found to cover about 99% of all slow calls:
slowCallPattern (PtrArg: PtrArg: PtrArg: PtrArg: PtrArg: PtrArg: _) = (SLIT("stg_ap_pppppp"), 6)
slowCallPattern (PtrArg: PtrArg: PtrArg: PtrArg: PtrArg: _) 	= (SLIT("stg_ap_ppppp"), 5)
slowCallPattern (PtrArg: PtrArg: PtrArg: PtrArg: _) 	= (SLIT("stg_ap_pppp"), 4)
slowCallPattern (PtrArg: PtrArg: PtrArg: VoidArg: _) 	= (SLIT("stg_ap_pppv"), 4)
slowCallPattern (PtrArg: PtrArg: PtrArg: _)       	= (SLIT("stg_ap_ppp"), 3)
slowCallPattern (PtrArg: PtrArg: VoidArg: _)       	= (SLIT("stg_ap_ppv"), 3)
slowCallPattern (PtrArg: PtrArg: _)			= (SLIT("stg_ap_pp"), 2)
slowCallPattern (PtrArg: VoidArg: _)			= (SLIT("stg_ap_pv"), 2)
slowCallPattern (PtrArg: _)				= (SLIT("stg_ap_p"), 1)
slowCallPattern (VoidArg: _)				= (SLIT("stg_ap_v"), 1)
slowCallPattern (NonPtrArg: _)				= (SLIT("stg_ap_n"), 1)
slowCallPattern (FloatArg: _)				= (SLIT("stg_ap_f"), 1)
slowCallPattern (DoubleArg: _)				= (SLIT("stg_ap_d"), 1)
slowCallPattern (LongArg: _)				= (SLIT("stg_ap_l"), 1)
slowCallPattern _  = panic "CgStackery.slowCallPattern"

-------------------------------------------------------------------------
--
--		Return conventions
--
-------------------------------------------------------------------------

-- A @CtrlReturnConvention@ says how {\em control} is returned.

data CtrlReturnConvention
  = VectoredReturn	Int	-- size of the vector table (family size)
  | UnvectoredReturn    Int 	-- family size

ctrlReturnConvAlg :: TyCon -> CtrlReturnConvention
ctrlReturnConvAlg tycon
  = case (tyConFamilySize tycon) of
      size -> -- we're supposed to know...
	if (size > (1::Int) && size <= mAX_FAMILY_SIZE_FOR_VEC_RETURNS) then
	    VectoredReturn size
	else
	    UnvectoredReturn size	
  -- NB: unvectored returns Include size 0 (no constructors), so that
  --     the following perverse code compiles (it crashed GHC in 5.02)
  -- 	    data T1
  --	    data T2 = T2 !T1 Int
  --     The only value of type T1 is bottom, which never returns anyway.

dataReturnConvPrim :: CgRep -> CmmReg
dataReturnConvPrim PtrArg    = CmmGlobal (VanillaReg 1)
dataReturnConvPrim NonPtrArg = CmmGlobal (VanillaReg 1)
dataReturnConvPrim LongArg   = CmmGlobal (LongReg 1)
dataReturnConvPrim FloatArg  = CmmGlobal (FloatReg 1)
dataReturnConvPrim DoubleArg = CmmGlobal (DoubleReg 1)
dataReturnConvPrim VoidArg   = panic "dataReturnConvPrim: void"


-- getSequelAmode returns an amode which refers to an info table.  The info
-- table will always be of the RET(_VEC)?_(BIG|SMALL) kind.  We're careful
-- not to handle real code pointers, just in case we're compiling for 
-- an unregisterised/untailcallish architecture, where info pointers and
-- code pointers aren't the same.
-- DIRE WARNING.
-- The OnStack case of sequelToAmode delivers an Amode which is only
-- valid just before the final control transfer, because it assumes
-- that Sp is pointing to the top word of the return address.  This
-- seems unclean but there you go.

getSequelAmode :: FCode CmmExpr
getSequelAmode
  = do	{ EndOfBlockInfo virt_sp sequel <- getEndOfBlockInfo
	; case sequel of
	    OnStack -> do { sp_rel <- getSpRelOffset virt_sp
			  ; returnFC (CmmLoad sp_rel wordRep) }

	    UpdateCode 	           -> returnFC (CmmLit (CmmLabel mkUpdInfoLabel))
	    CaseAlts lbl _ _ True  -> returnFC (CmmLit (CmmLabel mkSeqInfoLabel))
	    CaseAlts lbl _ _ False -> returnFC (CmmLit (CmmLabel lbl))
	}

-------------------------------------------------------------------------
--
--		Build a liveness mask for the current stack
--
-------------------------------------------------------------------------

-- There are four kinds of things on the stack:
--
--	- pointer variables (bound in the environment)
-- 	- non-pointer variables (boudn in the environment)
-- 	- free slots (recorded in the stack free list)
-- 	- non-pointer data slots (recorded in the stack free list)
-- 
-- We build up a bitmap of non-pointer slots by searching the environment
-- for all the pointer variables, and subtracting these from a bitmap
-- with initially all bits set (up to the size of the stack frame).

buildContLiveness :: Name		-- Basis for label (only)
		  -> [VirtualSpOffset] 	-- Live stack slots
		  -> FCode Liveness
buildContLiveness name live_slots
 = do	{ stk_usg    <- getStkUsage
	; let	StackUsage { realSp = real_sp, 
			     frameSp = frame_sp } = stk_usg

		start_sp :: VirtualSpOffset
		start_sp = real_sp - retAddrSizeW
		-- In a continuation, we want a liveness mask that 
		-- starts from just after the return address, which is 
		-- on the stack at real_sp.

		frame_size :: WordOff
		frame_size = start_sp - frame_sp
		-- real_sp points to the frame-header for the current
		-- stack frame, and the end of this frame is frame_sp.
		-- The size is therefore real_sp - frame_sp - retAddrSizeW
		-- (subtract one for the frame-header = return address).
	
		rel_slots :: [WordOff]
	 	rel_slots = sortLe (<=) 
	    	    [ start_sp - ofs  -- Get slots relative to top of frame
	    	    | ofs <- live_slots ]

		bitmap = intsToReverseBitmap frame_size rel_slots

	; WARN( not (all (>=0) rel_slots), 
		ppr name $$ ppr live_slots $$ ppr frame_size $$ ppr start_sp $$ ppr rel_slots )
	  mkLiveness name frame_size bitmap }


-------------------------------------------------------------------------
--
--		Register assignment
--
-------------------------------------------------------------------------

--  How to assign registers for 
--
--	1) Calling a fast entry point.
--	2) Returning an unboxed tuple.
--	3) Invoking an out-of-line PrimOp.
--
-- Registers are assigned in order.
-- 
-- If we run out, we don't attempt to assign any further registers (even
-- though we might have run out of only one kind of register); we just
-- return immediately with the left-overs specified.
-- 
-- The alternative version @assignAllRegs@ uses the complete set of
-- registers, including those that aren't mapped to real machine
-- registers.  This is used for calling special RTS functions and PrimOps
-- which expect their arguments to always be in the same registers.

assignCallRegs, assignPrimOpCallRegs, assignReturnRegs
	:: [(CgRep,a)]		-- Arg or result values to assign
	-> ([(a, GlobalReg)],	-- Register assignment in same order
				-- for *initial segment of* input list
				--   (but reversed; doesn't matter)
				-- VoidRep args do not appear here
	    [(CgRep,a)])	-- Leftover arg or result values

assignCallRegs args
  = assign_regs args (mkRegTbl [node])
	-- The entry convention for a function closure
	-- never uses Node for argument passing; instead
	-- Node points to the function closure itself

assignPrimOpCallRegs args
 = assign_regs args (mkRegTbl_allRegs [])
	-- For primops, *all* arguments must be passed in registers

assignReturnRegs args
 = assign_regs args (mkRegTbl [])
	-- For returning unboxed tuples etc, 
	-- we use all regs

assign_regs :: [(CgRep,a)]     	-- Arg or result values to assign
	    -> AvailRegs	-- Regs still avail: Vanilla, Float, Double, Longs
	    -> ([(a, GlobalReg)], [(CgRep, a)])
assign_regs args supply
  = go args [] supply
  where
    go [] acc supply = (acc, [])	-- Return the results reversed (doesn't matter)
    go ((VoidArg,_) : args) acc supply 	-- Skip void arguments; they aren't passed, and
	= go args acc supply		-- there's nothign to bind them to
    go ((rep,arg) : args) acc supply 
	= case assign_reg rep supply of
		Just (reg, supply') -> go args ((arg,reg):acc) supply'
		Nothing	   	    -> (acc, (rep,arg):args) 	-- No more regs

assign_reg :: CgRep -> AvailRegs -> Maybe (GlobalReg, AvailRegs)
assign_reg FloatArg  (vs, f:fs, ds, ls) = Just (FloatReg f,   (vs, fs, ds, ls))
assign_reg DoubleArg (vs, fs, d:ds, ls) = Just (DoubleReg d,  (vs, fs, ds, ls))
assign_reg LongArg   (vs, fs, ds, l:ls) = Just (LongReg l,    (vs, fs, ds, ls))
assign_reg PtrArg    (v:vs, fs, ds, ls) = Just (VanillaReg v, (vs, fs, ds, ls))
assign_reg NonPtrArg (v:vs, fs, ds, ls) = Just (VanillaReg v, (vs, fs, ds, ls))
    -- PtrArg and NonPtrArg both go in a vanilla register
assign_reg other     not_enough_regs    = Nothing


-------------------------------------------------------------------------
--
--		Register supplies
--
-------------------------------------------------------------------------

-- Vanilla registers can contain pointers, Ints, Chars.
-- Floats and doubles have separate register supplies.
--
-- We take these register supplies from the *real* registers, i.e. those
-- that are guaranteed to map to machine registers.

useVanillaRegs | opt_Unregisterised = 0
	       | otherwise          = mAX_Real_Vanilla_REG
useFloatRegs   | opt_Unregisterised = 0
	       | otherwise          = mAX_Real_Float_REG
useDoubleRegs  | opt_Unregisterised = 0
	       | otherwise          = mAX_Real_Double_REG
useLongRegs    | opt_Unregisterised = 0
	       | otherwise          = mAX_Real_Long_REG

vanillaRegNos, floatRegNos, doubleRegNos, longRegNos :: [Int]
vanillaRegNos	 = regList useVanillaRegs
floatRegNos	 = regList useFloatRegs
doubleRegNos	 = regList useDoubleRegs
longRegNos       = regList useLongRegs

allVanillaRegNos, allFloatRegNos, allDoubleRegNos, allLongRegNos :: [Int]
allVanillaRegNos = regList mAX_Vanilla_REG
allFloatRegNos	 = regList mAX_Float_REG
allDoubleRegNos	 = regList mAX_Double_REG
allLongRegNos	 = regList mAX_Long_REG

regList 0 = []
regList n = [1 .. n]

type AvailRegs = ( [Int]   -- available vanilla regs.
		 , [Int]   -- floats
		 , [Int]   -- doubles
		 , [Int]   -- longs (int64 and word64)
		 )

mkRegTbl :: [GlobalReg] -> AvailRegs
mkRegTbl regs_in_use
  = mkRegTbl' regs_in_use vanillaRegNos floatRegNos doubleRegNos longRegNos

mkRegTbl_allRegs :: [GlobalReg] -> AvailRegs
mkRegTbl_allRegs regs_in_use
  = mkRegTbl' regs_in_use allVanillaRegNos allFloatRegNos allDoubleRegNos allLongRegNos

mkRegTbl' regs_in_use vanillas floats doubles longs
  = (ok_vanilla, ok_float, ok_double, ok_long)
  where
    ok_vanilla = mapCatMaybes (select VanillaReg) vanillas
    ok_float   = mapCatMaybes (select FloatReg)	  floats
    ok_double  = mapCatMaybes (select DoubleReg)  doubles
    ok_long    = mapCatMaybes (select LongReg)    longs   
				    -- rep isn't looked at, hence we can use any old rep.

    select :: (Int -> GlobalReg) -> Int{-cand-} -> Maybe Int
	-- one we've unboxed the Int, we make a GlobalReg
	-- and see if it is already in use; if not, return its number.

    select mk_reg_fun cand
      = let
	    reg = mk_reg_fun cand
	in
	if reg `not_elem` regs_in_use
	then Just cand
	else Nothing
      where
	not_elem = isn'tIn "mkRegTbl"