-----------------------------------------------------------------------------
--
-- Code generation for PrimOps.
--
-- (c) The University of Glasgow 2004-2006
--
-----------------------------------------------------------------------------

module CgPrimOp (
   cgPrimOp
 ) where

import BasicTypes
import ForeignCall
import ClosureInfo
import StgSyn
import CgForeignCall
import CgBindery
import CgMonad
import CgHeapery
import CgInfoTbls
import CgTicky
import CgProf
import CgUtils
import OldCmm
import CLabel
import OldCmmUtils
import PrimOp
import SMRep
import Module
import Constants
import Outputable
import FastString

-- ---------------------------------------------------------------------------
-- Code generation for PrimOps

cgPrimOp   :: [CmmFormal]	-- where to put the results
	   -> PrimOp		-- the op
	   -> [StgArg]		-- arguments
	   -> StgLiveVars	-- live vars, in case we need to save them
	   -> Code

cgPrimOp results op args live
  = do arg_exprs <- getArgAmodes args
       let non_void_args = [ e | (r,e) <- arg_exprs, nonVoidArg r ] 
       emitPrimOp results op non_void_args live


emitPrimOp :: [CmmFormal]	-- where to put the results
	   -> PrimOp		-- the op
	   -> [CmmExpr]		-- arguments
	   -> StgLiveVars	-- live vars, in case we need to save them
	   -> Code

--  First we handle various awkward cases specially.  The remaining
-- easy cases are then handled by translateOp, defined below.

emitPrimOp [res_r,res_c] IntAddCOp [aa,bb] _
{- 
   With some bit-twiddling, we can define int{Add,Sub}Czh portably in
   C, and without needing any comparisons.  This may not be the
   fastest way to do it - if you have better code, please send it! --SDM
  
   Return : r = a + b,  c = 0 if no overflow, 1 on overflow.
  
   We currently don't make use of the r value if c is != 0 (i.e. 
   overflow), we just convert to big integers and try again.  This
   could be improved by making r and c the correct values for
   plugging into a new J#.  
   
   { r = ((I_)(a)) + ((I_)(b));					\
     c = ((StgWord)(~(((I_)(a))^((I_)(b))) & (((I_)(a))^r)))	\
         >> (BITS_IN (I_) - 1);					\
   } 
   Wading through the mass of bracketry, it seems to reduce to:
   c = ( (~(a^b)) & (a^r) ) >>unsigned (BITS_IN(I_)-1)

-}
   = stmtsC [
        CmmAssign (CmmLocal res_r) (CmmMachOp mo_wordAdd [aa,bb]),
        CmmAssign (CmmLocal res_c) $
	  CmmMachOp mo_wordUShr [
		CmmMachOp mo_wordAnd [
		    CmmMachOp mo_wordNot [CmmMachOp mo_wordXor [aa,bb]],
		    CmmMachOp mo_wordXor [aa, CmmReg (CmmLocal res_r)]
		], 
	        CmmLit (mkIntCLit (wORD_SIZE_IN_BITS - 1))
	  ]
     ]


emitPrimOp [res_r,res_c] IntSubCOp [aa,bb] _
{- Similarly:
   #define subIntCzh(r,c,a,b)					\
   { r = ((I_)(a)) - ((I_)(b));					\
     c = ((StgWord)((((I_)(a))^((I_)(b))) & (((I_)(a))^r)))	\
         >> (BITS_IN (I_) - 1);					\
   }

   c =  ((a^b) & (a^r)) >>unsigned (BITS_IN(I_)-1)
-}
   = stmtsC [
        CmmAssign (CmmLocal res_r) (CmmMachOp mo_wordSub [aa,bb]),
        CmmAssign (CmmLocal res_c) $
	  CmmMachOp mo_wordUShr [
		CmmMachOp mo_wordAnd [
		    CmmMachOp mo_wordXor [aa,bb],
		    CmmMachOp mo_wordXor [aa, CmmReg (CmmLocal res_r)]
		], 
	        CmmLit (mkIntCLit (wORD_SIZE_IN_BITS - 1))
	  ]
     ]


emitPrimOp [res] ParOp [arg] live
  = do
	-- for now, just implement this in a C function
	-- later, we might want to inline it.
    vols <- getVolatileRegs live
    emitForeignCall' PlayRisky
	[CmmHinted res NoHint]
    	(CmmCallee newspark CCallConv) 
	[   (CmmHinted (CmmReg (CmmGlobal BaseReg)) AddrHint)
          , (CmmHinted arg AddrHint)  ] 
	(Just vols)
        NoC_SRT -- No SRT b/c we do PlayRisky
        CmmMayReturn
  where
        newspark = CmmLit (CmmLabel (mkCmmCodeLabel rtsPackageId (fsLit "newSpark")))

emitPrimOp [res] SparkOp [arg] live = do
    -- returns the value of arg in res.  We're going to therefore
    -- refer to arg twice (once to pass to newSpark(), and once to
    -- assign to res), so put it in a temporary.
    tmp <- newTemp bWord
    stmtC (CmmAssign (CmmLocal tmp) arg)

    vols <- getVolatileRegs live
    emitForeignCall' PlayRisky []
    	(CmmCallee newspark CCallConv) 
	[   (CmmHinted (CmmReg (CmmGlobal BaseReg)) AddrHint)
          , (CmmHinted arg AddrHint)  ] 
	(Just vols)
        NoC_SRT -- No SRT b/c we do PlayRisky
        CmmMayReturn
    stmtC (CmmAssign (CmmLocal res) (CmmReg (CmmLocal tmp)))
  where
	newspark = CmmLit (CmmLabel (mkCmmCodeLabel rtsPackageId (fsLit "newSpark")))


emitPrimOp [res] ReadMutVarOp [mutv] _
   = stmtC (CmmAssign (CmmLocal res) (cmmLoadIndexW mutv fixedHdrSize gcWord))

emitPrimOp [] WriteMutVarOp [mutv,var] live
   = do
	stmtC (CmmStore (cmmOffsetW mutv fixedHdrSize) var)
	vols <- getVolatileRegs live
	emitForeignCall' PlayRisky
		[{-no results-}]
		(CmmCallee (CmmLit (CmmLabel mkDirty_MUT_VAR_Label))
			 CCallConv)
		[   (CmmHinted (CmmReg (CmmGlobal BaseReg)) AddrHint)
                  , (CmmHinted mutv AddrHint)  ]
		(Just vols)
                NoC_SRT -- No SRT b/c we do PlayRisky
                CmmMayReturn

--  #define sizzeofByteArrayzh(r,a) \
--     r = ((StgArrWords *)(a))->bytes
emitPrimOp [res] SizeofByteArrayOp [arg] _
   = stmtC $
	CmmAssign (CmmLocal res) (cmmLoadIndexW arg fixedHdrSize bWord)

--  #define sizzeofMutableByteArrayzh(r,a) \
--      r = ((StgArrWords *)(a))->bytes
emitPrimOp [res] SizeofMutableByteArrayOp [arg] live
   = emitPrimOp [res] SizeofByteArrayOp [arg] live


--  #define touchzh(o)                  /* nothing */
emitPrimOp [] TouchOp [_] _
   = nopC

--  #define byteArrayContentszh(r,a) r = BYTE_ARR_CTS(a)
emitPrimOp [res] ByteArrayContents_Char [arg] _
   = stmtC (CmmAssign (CmmLocal res) (cmmOffsetB arg arrWordsHdrSize))

--  #define stableNameToIntzh(r,s)   (r = ((StgStableName *)s)->sn)
emitPrimOp [res] StableNameToIntOp [arg] _
   = stmtC (CmmAssign (CmmLocal res) (cmmLoadIndexW arg fixedHdrSize bWord))

--  #define eqStableNamezh(r,sn1,sn2)					\
--    (r = (((StgStableName *)sn1)->sn == ((StgStableName *)sn2)->sn))
emitPrimOp [res] EqStableNameOp [arg1,arg2] _
   = stmtC (CmmAssign (CmmLocal res) (CmmMachOp mo_wordEq [
				cmmLoadIndexW arg1 fixedHdrSize bWord,
				cmmLoadIndexW arg2 fixedHdrSize bWord
			 ]))


emitPrimOp [res] ReallyUnsafePtrEqualityOp [arg1,arg2] _
   = stmtC (CmmAssign (CmmLocal res) (CmmMachOp mo_wordEq [arg1,arg2]))

--  #define addrToHValuezh(r,a) r=(P_)a
emitPrimOp [res] AddrToHValueOp [arg] _
   = stmtC (CmmAssign (CmmLocal res) arg)

--  #define dataToTagzh(r,a)  r=(GET_TAG(((StgClosure *)a)->header.info))
--  Note: argument may be tagged!
emitPrimOp [res] DataToTagOp [arg] _
   = stmtC (CmmAssign (CmmLocal res) (getConstrTag (cmmUntag arg)))

{- Freezing arrays-of-ptrs requires changing an info table, for the
   benefit of the generational collector.  It needs to scavenge mutable
   objects, even if they are in old space.  When they become immutable,
   they can be removed from this scavenge list.	 -}

--  #define unsafeFreezzeArrayzh(r,a)
--	{
--        SET_INFO((StgClosure *)a,&stg_MUT_ARR_PTRS_FROZEN0_info);
--	  r = a;
--	}
emitPrimOp [res] UnsafeFreezeArrayOp [arg] _
   = stmtsC [ setInfo arg (CmmLit (CmmLabel mkMAP_FROZEN_infoLabel)),
	     CmmAssign (CmmLocal res) arg ]

--  #define unsafeFreezzeByteArrayzh(r,a)	r=(a)
emitPrimOp [res] UnsafeFreezeByteArrayOp [arg] _
   = stmtC (CmmAssign (CmmLocal res) arg)

emitPrimOp [] CopyArrayOp [src,src_off,dst,dst_off,n] live =
    doCopyArrayOp src src_off dst dst_off n live
emitPrimOp [] CopyMutableArrayOp [src,src_off,dst,dst_off,n] live =
    doCopyMutableArrayOp src src_off dst dst_off n live
emitPrimOp [res] CloneArrayOp [src,src_off,n] live =
    emitCloneArray mkMAP_FROZEN_infoLabel res src src_off n live
emitPrimOp [res] CloneMutableArrayOp [src,src_off,n] live =
    emitCloneArray mkMAP_DIRTY_infoLabel res src src_off n live
emitPrimOp [res] FreezeArrayOp [src,src_off,n] live =
    emitCloneArray mkMAP_FROZEN_infoLabel res src src_off n live
emitPrimOp [res] ThawArrayOp [src,src_off,n] live =
    emitCloneArray mkMAP_DIRTY_infoLabel res src src_off n live

-- Reading/writing pointer arrays

emitPrimOp [r] ReadArrayOp  [obj,ix]   _  = doReadPtrArrayOp r obj ix
emitPrimOp [r] IndexArrayOp [obj,ix]   _  = doReadPtrArrayOp r obj ix
emitPrimOp []  WriteArrayOp [obj,ix,v] _  = doWritePtrArrayOp obj ix v

emitPrimOp [res] SizeofArrayOp [arg] _
   = stmtC $ CmmAssign (CmmLocal res) (cmmLoadIndexW arg (fixedHdrSize + oFFSET_StgMutArrPtrs_ptrs) bWord)
emitPrimOp [res] SizeofMutableArrayOp [arg] live
   = emitPrimOp [res] SizeofArrayOp [arg] live

-- IndexXXXoffAddr

emitPrimOp res IndexOffAddrOp_Char      args _ = doIndexOffAddrOp (Just mo_u_8ToWord) b8 res args
emitPrimOp res IndexOffAddrOp_WideChar  args _ = doIndexOffAddrOp (Just mo_u_32ToWord) b32 res args
emitPrimOp res IndexOffAddrOp_Int       args _ = doIndexOffAddrOp Nothing bWord res args
emitPrimOp res IndexOffAddrOp_Word      args _ = doIndexOffAddrOp Nothing bWord res args
emitPrimOp res IndexOffAddrOp_Addr      args _ = doIndexOffAddrOp Nothing bWord res args
emitPrimOp res IndexOffAddrOp_Float     args _ = doIndexOffAddrOp Nothing f32 res args
emitPrimOp res IndexOffAddrOp_Double    args _ = doIndexOffAddrOp Nothing f64 res args
emitPrimOp res IndexOffAddrOp_StablePtr args _ = doIndexOffAddrOp Nothing bWord res args
emitPrimOp res IndexOffAddrOp_Int8      args _ = doIndexOffAddrOp (Just mo_s_8ToWord)  b8  res args
emitPrimOp res IndexOffAddrOp_Int16     args _ = doIndexOffAddrOp (Just mo_s_16ToWord) b16 res args
emitPrimOp res IndexOffAddrOp_Int32     args _ = doIndexOffAddrOp (Just mo_s_32ToWord) b32 res args
emitPrimOp res IndexOffAddrOp_Int64     args _ = doIndexOffAddrOp Nothing b64 res args
emitPrimOp res IndexOffAddrOp_Word8     args _ = doIndexOffAddrOp (Just mo_u_8ToWord) b8   res args
emitPrimOp res IndexOffAddrOp_Word16    args _ = doIndexOffAddrOp (Just mo_u_16ToWord) b16 res args
emitPrimOp res IndexOffAddrOp_Word32    args _ = doIndexOffAddrOp (Just mo_u_32ToWord) b32 res args
emitPrimOp res IndexOffAddrOp_Word64    args _ = doIndexOffAddrOp Nothing b64 res args

-- ReadXXXoffAddr, which are identical, for our purposes, to IndexXXXoffAddr.

emitPrimOp res ReadOffAddrOp_Char      args _ = doIndexOffAddrOp (Just mo_u_8ToWord) b8 res args
emitPrimOp res ReadOffAddrOp_WideChar  args _ = doIndexOffAddrOp (Just mo_u_32ToWord) b32 res args
emitPrimOp res ReadOffAddrOp_Int       args _ = doIndexOffAddrOp Nothing bWord res args
emitPrimOp res ReadOffAddrOp_Word      args _ = doIndexOffAddrOp Nothing bWord res args
emitPrimOp res ReadOffAddrOp_Addr      args _ = doIndexOffAddrOp Nothing bWord res args
emitPrimOp res ReadOffAddrOp_Float     args _ = doIndexOffAddrOp Nothing f32 res args
emitPrimOp res ReadOffAddrOp_Double    args _ = doIndexOffAddrOp Nothing f64 res args
emitPrimOp res ReadOffAddrOp_StablePtr args _ = doIndexOffAddrOp Nothing bWord res args
emitPrimOp res ReadOffAddrOp_Int8      args _ = doIndexOffAddrOp (Just mo_s_8ToWord) b8  res args
emitPrimOp res ReadOffAddrOp_Int16     args _ = doIndexOffAddrOp (Just mo_s_16ToWord) b16 res args
emitPrimOp res ReadOffAddrOp_Int32     args _ = doIndexOffAddrOp (Just mo_s_32ToWord) b32 res args
emitPrimOp res ReadOffAddrOp_Int64     args _ = doIndexOffAddrOp Nothing b64 res args
emitPrimOp res ReadOffAddrOp_Word8     args _ = doIndexOffAddrOp (Just mo_u_8ToWord) b8  res args
emitPrimOp res ReadOffAddrOp_Word16    args _ = doIndexOffAddrOp (Just mo_u_16ToWord) b16 res args
emitPrimOp res ReadOffAddrOp_Word32    args _ = doIndexOffAddrOp (Just mo_u_32ToWord) b32 res args
emitPrimOp res ReadOffAddrOp_Word64    args _ = doIndexOffAddrOp Nothing b64 res args

-- IndexXXXArray

emitPrimOp res IndexByteArrayOp_Char      args _ = doIndexByteArrayOp (Just mo_u_8ToWord) b8 res args
emitPrimOp res IndexByteArrayOp_WideChar  args _ = doIndexByteArrayOp (Just mo_u_32ToWord) b32 res args
emitPrimOp res IndexByteArrayOp_Int       args _ = doIndexByteArrayOp Nothing bWord res args
emitPrimOp res IndexByteArrayOp_Word      args _ = doIndexByteArrayOp Nothing bWord res args
emitPrimOp res IndexByteArrayOp_Addr      args _ = doIndexByteArrayOp Nothing bWord res args
emitPrimOp res IndexByteArrayOp_Float     args _ = doIndexByteArrayOp Nothing f32 res args
emitPrimOp res IndexByteArrayOp_Double    args _ = doIndexByteArrayOp Nothing f64 res args
emitPrimOp res IndexByteArrayOp_StablePtr args _ = doIndexByteArrayOp Nothing bWord res args
emitPrimOp res IndexByteArrayOp_Int8      args _ = doIndexByteArrayOp (Just mo_s_8ToWord) b8  res args
emitPrimOp res IndexByteArrayOp_Int16     args _ = doIndexByteArrayOp (Just mo_s_16ToWord) b16  res args
emitPrimOp res IndexByteArrayOp_Int32     args _ = doIndexByteArrayOp (Just mo_s_32ToWord) b32  res args
emitPrimOp res IndexByteArrayOp_Int64     args _ = doIndexByteArrayOp Nothing b64  res args
emitPrimOp res IndexByteArrayOp_Word8     args _ = doIndexByteArrayOp (Just mo_u_8ToWord) b8  res args
emitPrimOp res IndexByteArrayOp_Word16    args _ = doIndexByteArrayOp (Just mo_u_16ToWord) b16  res args
emitPrimOp res IndexByteArrayOp_Word32    args _ = doIndexByteArrayOp (Just mo_u_32ToWord) b32  res args
emitPrimOp res IndexByteArrayOp_Word64    args _ = doIndexByteArrayOp Nothing b64  res args

-- ReadXXXArray, identical to IndexXXXArray.

emitPrimOp res ReadByteArrayOp_Char       args _ = doIndexByteArrayOp (Just mo_u_8ToWord) b8 res args
emitPrimOp res ReadByteArrayOp_WideChar   args _ = doIndexByteArrayOp (Just mo_u_32ToWord) b32 res args
emitPrimOp res ReadByteArrayOp_Int        args _ = doIndexByteArrayOp Nothing bWord res args
emitPrimOp res ReadByteArrayOp_Word       args _ = doIndexByteArrayOp Nothing bWord res args
emitPrimOp res ReadByteArrayOp_Addr       args _ = doIndexByteArrayOp Nothing bWord res args
emitPrimOp res ReadByteArrayOp_Float      args _ = doIndexByteArrayOp Nothing f32 res args
emitPrimOp res ReadByteArrayOp_Double     args _ = doIndexByteArrayOp Nothing f64 res args
emitPrimOp res ReadByteArrayOp_StablePtr  args _ = doIndexByteArrayOp Nothing bWord res args
emitPrimOp res ReadByteArrayOp_Int8       args _ = doIndexByteArrayOp (Just mo_s_8ToWord) b8  res args
emitPrimOp res ReadByteArrayOp_Int16      args _ = doIndexByteArrayOp (Just mo_s_16ToWord) b16  res args
emitPrimOp res ReadByteArrayOp_Int32      args _ = doIndexByteArrayOp (Just mo_s_32ToWord) b32  res args
emitPrimOp res ReadByteArrayOp_Int64      args _ = doIndexByteArrayOp Nothing b64  res args
emitPrimOp res ReadByteArrayOp_Word8      args _ = doIndexByteArrayOp (Just mo_u_8ToWord) b8  res args
emitPrimOp res ReadByteArrayOp_Word16     args _ = doIndexByteArrayOp (Just mo_u_16ToWord) b16  res args
emitPrimOp res ReadByteArrayOp_Word32     args _ = doIndexByteArrayOp (Just mo_u_32ToWord) b32  res args
emitPrimOp res ReadByteArrayOp_Word64     args _ = doIndexByteArrayOp Nothing b64  res args

-- WriteXXXoffAddr

emitPrimOp res WriteOffAddrOp_Char       args _ = doWriteOffAddrOp (Just mo_WordTo8) b8 res args
emitPrimOp res WriteOffAddrOp_WideChar   args _ = doWriteOffAddrOp (Just mo_WordTo32) b32 res args
emitPrimOp res WriteOffAddrOp_Int        args _ = doWriteOffAddrOp Nothing bWord res args
emitPrimOp res WriteOffAddrOp_Word       args _ = doWriteOffAddrOp Nothing bWord res args
emitPrimOp res WriteOffAddrOp_Addr       args _ = doWriteOffAddrOp Nothing bWord res args
emitPrimOp res WriteOffAddrOp_Float      args _ = doWriteOffAddrOp Nothing f32 res args
emitPrimOp res WriteOffAddrOp_Double     args _ = doWriteOffAddrOp Nothing f64 res args
emitPrimOp res WriteOffAddrOp_StablePtr  args _ = doWriteOffAddrOp Nothing bWord res args
emitPrimOp res WriteOffAddrOp_Int8       args _ = doWriteOffAddrOp (Just mo_WordTo8) b8  res args
emitPrimOp res WriteOffAddrOp_Int16      args _ = doWriteOffAddrOp (Just mo_WordTo16) b16 res args
emitPrimOp res WriteOffAddrOp_Int32      args _ = doWriteOffAddrOp (Just mo_WordTo32) b32 res args
emitPrimOp res WriteOffAddrOp_Int64      args _ = doWriteOffAddrOp Nothing b64 res args
emitPrimOp res WriteOffAddrOp_Word8      args _ = doWriteOffAddrOp (Just mo_WordTo8) b8  res args
emitPrimOp res WriteOffAddrOp_Word16     args _ = doWriteOffAddrOp (Just mo_WordTo16) b16 res args
emitPrimOp res WriteOffAddrOp_Word32     args _ = doWriteOffAddrOp (Just mo_WordTo32) b32 res args
emitPrimOp res WriteOffAddrOp_Word64     args _ = doWriteOffAddrOp Nothing b64 res args

-- WriteXXXArray

emitPrimOp res WriteByteArrayOp_Char      args _ = doWriteByteArrayOp (Just mo_WordTo8) b8 res args
emitPrimOp res WriteByteArrayOp_WideChar  args _ = doWriteByteArrayOp (Just mo_WordTo32) b32 res args
emitPrimOp res WriteByteArrayOp_Int       args _ = doWriteByteArrayOp Nothing bWord res args
emitPrimOp res WriteByteArrayOp_Word      args _ = doWriteByteArrayOp Nothing bWord res args
emitPrimOp res WriteByteArrayOp_Addr      args _ = doWriteByteArrayOp Nothing bWord res args
emitPrimOp res WriteByteArrayOp_Float     args _ = doWriteByteArrayOp Nothing f32 res args
emitPrimOp res WriteByteArrayOp_Double    args _ = doWriteByteArrayOp Nothing f64 res args
emitPrimOp res WriteByteArrayOp_StablePtr args _ = doWriteByteArrayOp Nothing bWord res args
emitPrimOp res WriteByteArrayOp_Int8      args _ = doWriteByteArrayOp (Just mo_WordTo8) b8  res args
emitPrimOp res WriteByteArrayOp_Int16     args _ = doWriteByteArrayOp (Just mo_WordTo16) b16  res args
emitPrimOp res WriteByteArrayOp_Int32     args _ = doWriteByteArrayOp (Just mo_WordTo32) b32  res args
emitPrimOp res WriteByteArrayOp_Int64     args _ = doWriteByteArrayOp Nothing b64  res args
emitPrimOp res WriteByteArrayOp_Word8     args _ = doWriteByteArrayOp (Just mo_WordTo8) b8  res args
emitPrimOp res WriteByteArrayOp_Word16    args _ = doWriteByteArrayOp (Just mo_WordTo16) b16  res args
emitPrimOp res WriteByteArrayOp_Word32    args _ = doWriteByteArrayOp (Just mo_WordTo32) b32  res args
emitPrimOp res WriteByteArrayOp_Word64    args _ = doWriteByteArrayOp Nothing b64  res args

-- Copying byte arrays

emitPrimOp [] CopyByteArrayOp [src,src_off,dst,dst_off,n] live =
    doCopyByteArrayOp src src_off dst dst_off n live
emitPrimOp [] CopyMutableByteArrayOp [src,src_off,dst,dst_off,n] live =
    doCopyMutableByteArrayOp src src_off dst dst_off n live


-- The rest just translate straightforwardly
emitPrimOp [res] op [arg] _
   | nopOp op
   = stmtC (CmmAssign (CmmLocal res) arg)

   | Just (mop,rep) <- narrowOp op
   = stmtC (CmmAssign (CmmLocal res) $
	    CmmMachOp (mop rep wordWidth) [CmmMachOp (mop wordWidth rep) [arg]])

emitPrimOp [res] op args live
   | Just prim <- callishOp op
   = do vols <- getVolatileRegs live
	emitForeignCall' PlayRisky
	   [CmmHinted res NoHint] 
	   (CmmPrim prim) 
	   [CmmHinted a NoHint | a<-args]  -- ToDo: hints?
	   (Just vols)
           NoC_SRT -- No SRT b/c we do PlayRisky
           CmmMayReturn

   | Just mop <- translateOp op
   = let stmt = CmmAssign (CmmLocal res) (CmmMachOp mop args) in
     stmtC stmt

emitPrimOp _ op _ _
 = pprPanic "emitPrimOp: can't translate PrimOp" (ppr op)


-- These PrimOps are NOPs in Cmm

nopOp :: PrimOp -> Bool
nopOp Int2WordOp     = True
nopOp Word2IntOp     = True
nopOp Int2AddrOp     = True
nopOp Addr2IntOp     = True
nopOp ChrOp	     = True  -- Int# and Char# are rep'd the same
nopOp OrdOp	     = True
nopOp _		     = False

-- These PrimOps turn into double casts

narrowOp :: PrimOp -> Maybe (Width -> Width -> MachOp, Width)
narrowOp Narrow8IntOp   = Just (MO_SS_Conv, W8)
narrowOp Narrow16IntOp  = Just (MO_SS_Conv, W16)
narrowOp Narrow32IntOp  = Just (MO_SS_Conv, W32)
narrowOp Narrow8WordOp  = Just (MO_UU_Conv, W8)
narrowOp Narrow16WordOp = Just (MO_UU_Conv, W16)
narrowOp Narrow32WordOp = Just (MO_UU_Conv, W32)
narrowOp _ 		= Nothing

-- Native word signless ops

translateOp :: PrimOp -> Maybe MachOp
translateOp IntAddOp       = Just mo_wordAdd
translateOp IntSubOp       = Just mo_wordSub
translateOp WordAddOp      = Just mo_wordAdd
translateOp WordSubOp      = Just mo_wordSub
translateOp AddrAddOp      = Just mo_wordAdd
translateOp AddrSubOp      = Just mo_wordSub

translateOp IntEqOp        = Just mo_wordEq
translateOp IntNeOp        = Just mo_wordNe
translateOp WordEqOp       = Just mo_wordEq
translateOp WordNeOp       = Just mo_wordNe
translateOp AddrEqOp       = Just mo_wordEq
translateOp AddrNeOp       = Just mo_wordNe

translateOp AndOp          = Just mo_wordAnd
translateOp OrOp           = Just mo_wordOr
translateOp XorOp          = Just mo_wordXor
translateOp NotOp          = Just mo_wordNot
translateOp SllOp	   = Just mo_wordShl
translateOp SrlOp	   = Just mo_wordUShr

translateOp AddrRemOp	   = Just mo_wordURem

-- Native word signed ops

translateOp IntMulOp        = Just mo_wordMul
translateOp IntMulMayOfloOp = Just (MO_S_MulMayOflo wordWidth)
translateOp IntQuotOp       = Just mo_wordSQuot
translateOp IntRemOp        = Just mo_wordSRem
translateOp IntNegOp        = Just mo_wordSNeg


translateOp IntGeOp        = Just mo_wordSGe
translateOp IntLeOp        = Just mo_wordSLe
translateOp IntGtOp        = Just mo_wordSGt
translateOp IntLtOp        = Just mo_wordSLt

translateOp ISllOp	   = Just mo_wordShl
translateOp ISraOp	   = Just mo_wordSShr
translateOp ISrlOp	   = Just mo_wordUShr

-- Native word unsigned ops

translateOp WordGeOp       = Just mo_wordUGe
translateOp WordLeOp       = Just mo_wordULe
translateOp WordGtOp       = Just mo_wordUGt
translateOp WordLtOp       = Just mo_wordULt

translateOp WordMulOp      = Just mo_wordMul
translateOp WordQuotOp     = Just mo_wordUQuot
translateOp WordRemOp      = Just mo_wordURem

translateOp AddrGeOp       = Just mo_wordUGe
translateOp AddrLeOp       = Just mo_wordULe
translateOp AddrGtOp       = Just mo_wordUGt
translateOp AddrLtOp       = Just mo_wordULt

-- Char# ops

translateOp CharEqOp       = Just (MO_Eq wordWidth)
translateOp CharNeOp       = Just (MO_Ne wordWidth)
translateOp CharGeOp       = Just (MO_U_Ge wordWidth)
translateOp CharLeOp       = Just (MO_U_Le wordWidth)
translateOp CharGtOp       = Just (MO_U_Gt wordWidth)
translateOp CharLtOp       = Just (MO_U_Lt wordWidth)

-- Double ops

translateOp DoubleEqOp     = Just (MO_F_Eq W64)
translateOp DoubleNeOp     = Just (MO_F_Ne W64)
translateOp DoubleGeOp     = Just (MO_F_Ge W64)
translateOp DoubleLeOp     = Just (MO_F_Le W64)
translateOp DoubleGtOp     = Just (MO_F_Gt W64)
translateOp DoubleLtOp     = Just (MO_F_Lt W64)

translateOp DoubleAddOp    = Just (MO_F_Add W64)
translateOp DoubleSubOp    = Just (MO_F_Sub W64)
translateOp DoubleMulOp    = Just (MO_F_Mul W64)
translateOp DoubleDivOp    = Just (MO_F_Quot W64)
translateOp DoubleNegOp    = Just (MO_F_Neg W64)

-- Float ops

translateOp FloatEqOp     = Just (MO_F_Eq W32)
translateOp FloatNeOp     = Just (MO_F_Ne W32)
translateOp FloatGeOp     = Just (MO_F_Ge W32)
translateOp FloatLeOp     = Just (MO_F_Le W32)
translateOp FloatGtOp     = Just (MO_F_Gt W32)
translateOp FloatLtOp     = Just (MO_F_Lt W32)

translateOp FloatAddOp    = Just (MO_F_Add  W32)
translateOp FloatSubOp    = Just (MO_F_Sub  W32)
translateOp FloatMulOp    = Just (MO_F_Mul  W32)
translateOp FloatDivOp    = Just (MO_F_Quot W32)
translateOp FloatNegOp    = Just (MO_F_Neg  W32)

-- Conversions

translateOp Int2DoubleOp   = Just (MO_SF_Conv wordWidth W64)
translateOp Double2IntOp   = Just (MO_FS_Conv W64 wordWidth)

translateOp Int2FloatOp    = Just (MO_SF_Conv wordWidth W32)
translateOp Float2IntOp    = Just (MO_FS_Conv W32 wordWidth)

translateOp Float2DoubleOp = Just (MO_FF_Conv W32 W64)
translateOp Double2FloatOp = Just (MO_FF_Conv W64 W32)

-- Word comparisons masquerading as more exotic things.

translateOp SameMutVarOp           = Just mo_wordEq
translateOp SameMVarOp             = Just mo_wordEq
translateOp SameMutableArrayOp     = Just mo_wordEq
translateOp SameMutableByteArrayOp = Just mo_wordEq
translateOp SameTVarOp             = Just mo_wordEq
translateOp EqStablePtrOp          = Just mo_wordEq

translateOp _ = Nothing

-- These primops are implemented by CallishMachOps, because they sometimes
-- turn into foreign calls depending on the backend.

callishOp :: PrimOp -> Maybe CallishMachOp
callishOp DoublePowerOp  = Just MO_F64_Pwr
callishOp DoubleSinOp    = Just MO_F64_Sin
callishOp DoubleCosOp    = Just MO_F64_Cos
callishOp DoubleTanOp    = Just MO_F64_Tan
callishOp DoubleSinhOp   = Just MO_F64_Sinh
callishOp DoubleCoshOp   = Just MO_F64_Cosh
callishOp DoubleTanhOp   = Just MO_F64_Tanh
callishOp DoubleAsinOp   = Just MO_F64_Asin
callishOp DoubleAcosOp   = Just MO_F64_Acos
callishOp DoubleAtanOp   = Just MO_F64_Atan
callishOp DoubleLogOp    = Just MO_F64_Log
callishOp DoubleExpOp    = Just MO_F64_Exp
callishOp DoubleSqrtOp   = Just MO_F64_Sqrt

callishOp FloatPowerOp  = Just MO_F32_Pwr
callishOp FloatSinOp    = Just MO_F32_Sin
callishOp FloatCosOp    = Just MO_F32_Cos
callishOp FloatTanOp    = Just MO_F32_Tan
callishOp FloatSinhOp   = Just MO_F32_Sinh
callishOp FloatCoshOp   = Just MO_F32_Cosh
callishOp FloatTanhOp   = Just MO_F32_Tanh
callishOp FloatAsinOp   = Just MO_F32_Asin
callishOp FloatAcosOp   = Just MO_F32_Acos
callishOp FloatAtanOp   = Just MO_F32_Atan
callishOp FloatLogOp    = Just MO_F32_Log
callishOp FloatExpOp    = Just MO_F32_Exp
callishOp FloatSqrtOp   = Just MO_F32_Sqrt

callishOp _ = Nothing

------------------------------------------------------------------------------
-- Helpers for translating various minor variants of array indexing.

-- Bytearrays outside the heap; hence non-pointers
doIndexOffAddrOp, doIndexByteArrayOp 
	:: Maybe MachOp -> CmmType 
	-> [LocalReg] -> [CmmExpr] -> Code
doIndexOffAddrOp maybe_post_read_cast rep [res] [addr,idx]
   = mkBasicIndexedRead 0 maybe_post_read_cast rep res addr idx
doIndexOffAddrOp _ _ _ _
   = panic "CgPrimOp: doIndexOffAddrOp"

doIndexByteArrayOp maybe_post_read_cast rep [res] [addr,idx]
   = mkBasicIndexedRead arrWordsHdrSize maybe_post_read_cast rep res addr idx
doIndexByteArrayOp _ _ _ _ 
   = panic "CgPrimOp: doIndexByteArrayOp"

doReadPtrArrayOp :: LocalReg -> CmmExpr -> CmmExpr -> Code
doReadPtrArrayOp res addr idx
   = mkBasicIndexedRead arrPtrsHdrSize Nothing gcWord res addr idx


doWriteOffAddrOp, doWriteByteArrayOp 
	:: Maybe MachOp -> CmmType 
	-> [LocalReg] -> [CmmExpr] -> Code
doWriteOffAddrOp maybe_pre_write_cast rep [] [addr,idx,val]
   = mkBasicIndexedWrite 0 maybe_pre_write_cast rep addr idx val
doWriteOffAddrOp _ _ _ _
   = panic "CgPrimOp: doWriteOffAddrOp"

doWriteByteArrayOp maybe_pre_write_cast rep [] [addr,idx,val]
   = mkBasicIndexedWrite arrWordsHdrSize maybe_pre_write_cast rep addr idx val
doWriteByteArrayOp _ _ _ _ 
   = panic "CgPrimOp: doWriteByteArrayOp"

doWritePtrArrayOp :: CmmExpr -> CmmExpr -> CmmExpr -> Code
doWritePtrArrayOp addr idx val
   = do mkBasicIndexedWrite arrPtrsHdrSize Nothing bWord addr idx val
        stmtC (setInfo addr (CmmLit (CmmLabel mkMAP_DIRTY_infoLabel)))
   -- the write barrier.  We must write a byte into the mark table:
   -- bits8[a + header_size + StgMutArrPtrs_size(a) + x >> N]
        stmtC $ CmmStore (
          cmmOffsetExpr
           (cmmOffsetExprW (cmmOffsetB addr arrPtrsHdrSize)
                          (loadArrPtrsSize addr))
           (CmmMachOp mo_wordUShr [idx,
                                   CmmLit (mkIntCLit mUT_ARR_PTRS_CARD_BITS)])
          ) (CmmLit (CmmInt 1 W8))

loadArrPtrsSize :: CmmExpr -> CmmExpr
loadArrPtrsSize addr = CmmLoad (cmmOffsetB addr off) bWord
 where off = fixedHdrSize*wORD_SIZE + oFFSET_StgMutArrPtrs_ptrs

mkBasicIndexedRead :: ByteOff -> Maybe MachOp -> CmmType 
		   -> LocalReg -> CmmExpr -> CmmExpr -> Code
mkBasicIndexedRead off Nothing read_rep res base idx
   = stmtC (CmmAssign (CmmLocal res) (cmmLoadIndexOffExpr off read_rep base idx))
mkBasicIndexedRead off (Just cast) read_rep res base idx
   = stmtC (CmmAssign (CmmLocal res) (CmmMachOp cast [
				cmmLoadIndexOffExpr off read_rep base idx]))

mkBasicIndexedWrite :: ByteOff -> Maybe MachOp -> CmmType 
		    -> CmmExpr -> CmmExpr -> CmmExpr -> Code
mkBasicIndexedWrite off Nothing write_rep base idx val
   = stmtC (CmmStore (cmmIndexOffExpr off write_rep base idx) val)
mkBasicIndexedWrite off (Just cast) write_rep base idx val
   = stmtC (CmmStore (cmmIndexOffExpr off write_rep base idx) (CmmMachOp cast [val]))

-- ----------------------------------------------------------------------------
-- Misc utils

cmmIndexOffExpr :: ByteOff -> CmmType -> CmmExpr -> CmmExpr -> CmmExpr
cmmIndexOffExpr off rep base idx
   = cmmIndexExpr (typeWidth rep) (cmmOffsetB base off) idx

cmmLoadIndexOffExpr :: ByteOff -> CmmType -> CmmExpr -> CmmExpr -> CmmExpr
cmmLoadIndexOffExpr off rep base idx
   = CmmLoad (cmmIndexOffExpr off rep base idx) rep

setInfo :: CmmExpr -> CmmExpr -> CmmStmt
setInfo closure_ptr info_ptr = CmmStore closure_ptr info_ptr

-- ----------------------------------------------------------------------------
-- Copying byte arrays

-- | Takes a source 'ByteArray#', an offset in the source array, a
-- destination 'MutableByteArray#', an offset into the destination
-- array, and the number of bytes to copy.  Copies the given number of
-- bytes from the source array to the destination array.
doCopyByteArrayOp :: CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr
                  -> StgLiveVars -> Code
doCopyByteArrayOp = emitCopyByteArray copy
  where
    -- Copy data (we assume the arrays aren't overlapping since
    -- they're of different types)
    copy _src _dst dst_p src_p bytes live =
        emitMemcpyCall dst_p src_p bytes (CmmLit (mkIntCLit 1)) live

-- | Takes a source 'MutableByteArray#', an offset in the source
-- array, a destination 'MutableByteArray#', an offset into the
-- destination array, and the number of bytes to copy.  Copies the
-- given number of bytes from the source array to the destination
-- array.
doCopyMutableByteArrayOp :: CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr
                         -> StgLiveVars -> Code
doCopyMutableByteArrayOp = emitCopyByteArray copy
  where
    -- The only time the memory might overlap is when the two arrays
    -- we were provided are the same array!
    -- TODO: Optimize branch for common case of no aliasing.
    copy src dst dst_p src_p bytes live =
        emitIfThenElse (cmmEqWord src dst)
        (emitMemmoveCall dst_p src_p bytes (CmmLit (mkIntCLit 1)) live)
        (emitMemcpyCall dst_p src_p bytes (CmmLit (mkIntCLit 1)) live)

emitCopyByteArray :: (CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr
                  -> StgLiveVars -> Code)
                  -> CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr
                  -> StgLiveVars
                  -> Code
emitCopyByteArray copy src src_off dst dst_off n live = do
    dst_p <- assignTemp $ cmmOffsetExpr (cmmOffsetB dst arrWordsHdrSize) dst_off
    src_p <- assignTemp $ cmmOffsetExpr (cmmOffsetB src arrWordsHdrSize) src_off
    copy src dst dst_p src_p n live

-- ----------------------------------------------------------------------------
-- Copying pointer arrays

-- EZY: This code has an unusually high amount of assignTemp calls, seen
-- nowhere else in the code generator.  This is mostly because these
-- "primitive" ops result in a surprisingly large amount of code.  It
-- will likely be worthwhile to optimize what is emitted here, so that
-- our optimization passes don't waste time repeatedly optimizing the
-- same bits of code.

-- | Takes a source 'Array#', an offset in the source array, a
-- destination 'MutableArray#', an offset into the destination array,
-- and the number of elements to copy.  Copies the given number of
-- elements from the source array to the destination array.
doCopyArrayOp :: CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr
              -> StgLiveVars -> Code
doCopyArrayOp = emitCopyArray copy
  where
    -- Copy data (we assume the arrays aren't overlapping since
    -- they're of different types)
    copy _src _dst dst_p src_p bytes live =
        emitMemcpyCall dst_p src_p bytes (CmmLit (mkIntCLit wORD_SIZE)) live

-- | Takes a source 'MutableArray#', an offset in the source array, a
-- destination 'MutableArray#', an offset into the destination array,
-- and the number of elements to copy.  Copies the given number of
-- elements from the source array to the destination array.
doCopyMutableArrayOp :: CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr
                     -> StgLiveVars -> Code
doCopyMutableArrayOp = emitCopyArray copy
  where
    -- The only time the memory might overlap is when the two arrays
    -- we were provided are the same array!
    -- TODO: Optimize branch for common case of no aliasing.
    copy src dst dst_p src_p bytes live =
        emitIfThenElse (cmmEqWord src dst)
        (emitMemmoveCall dst_p src_p bytes (CmmLit (mkIntCLit wORD_SIZE)) live)
        (emitMemcpyCall dst_p src_p bytes (CmmLit (mkIntCLit wORD_SIZE)) live)

emitCopyArray :: (CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr
                  -> StgLiveVars -> Code)
              -> CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr
              -> StgLiveVars
              -> Code
emitCopyArray copy src0 src_off0 dst0 dst_off0 n0 live = do
    -- Assign the arguments to temporaries so the code generator can
    -- calculate liveness for us.
    src <- assignTemp_ src0
    src_off <- assignTemp_ src_off0
    dst <- assignTemp_ dst0
    dst_off <- assignTemp_ dst_off0
    n <- assignTemp_ n0

    -- Set the dirty bit in the header.
    stmtC (setInfo dst (CmmLit (CmmLabel mkMAP_DIRTY_infoLabel)))

    dst_elems_p <- assignTemp $ cmmOffsetB dst arrPtrsHdrSize
    dst_p <- assignTemp $ cmmOffsetExprW dst_elems_p dst_off
    src_p <- assignTemp $ cmmOffsetExprW (cmmOffsetB src arrPtrsHdrSize) src_off
    bytes <- assignTemp $ cmmMulWord n (CmmLit (mkIntCLit wORD_SIZE))

    copy src dst dst_p src_p bytes live

    -- The base address of the destination card table
    dst_cards_p <- assignTemp $ cmmOffsetExprW dst_elems_p (loadArrPtrsSize dst)

    emitSetCards dst_off dst_cards_p n live

-- | Takes an info table label, a register to return the newly
-- allocated array in, a source array, an offset in the source array,
-- and the number of elements to copy.  Allocates a new array and
-- initializes it form the source array.
emitCloneArray :: CLabel -> CmmFormal -> CmmExpr -> CmmExpr -> CmmExpr
               -> StgLiveVars -> Code
emitCloneArray info_p res_r src0 src_off0 n0 live = do
    -- Assign the arguments to temporaries so the code generator can
    -- calculate liveness for us.
    src <- assignTemp_ src0
    src_off <- assignTemp_ src_off0
    n <- assignTemp_ n0

    card_words <- assignTemp $ (n `cmmUShrWord`
                                (CmmLit (mkIntCLit mUT_ARR_PTRS_CARD_BITS)))
                  `cmmAddWord` CmmLit (mkIntCLit 1)
    size <- assignTemp $ n `cmmAddWord` card_words
    words <- assignTemp $ arrPtrsHdrSizeW `cmmAddWord` size

    arr_r <- newTemp bWord
    emitAllocateCall arr_r myCapability words live
    tickyAllocPrim (CmmLit (mkIntCLit arrPtrsHdrSize)) (n `cmmMulWord` wordSize)
        (CmmLit $ mkIntCLit 0)

    let arr = CmmReg (CmmLocal arr_r)
    emitSetDynHdr arr (CmmLit (CmmLabel info_p)) curCCSAddr
    stmtC $ CmmStore (cmmOffsetB arr (fixedHdrSize * wORD_SIZE +
                                      oFFSET_StgMutArrPtrs_ptrs)) n
    stmtC $ CmmStore (cmmOffsetB arr (fixedHdrSize * wORD_SIZE +
                                      oFFSET_StgMutArrPtrs_size)) size

    dst_p <- assignTemp $ cmmOffsetB arr arrPtrsHdrSize
    src_p <- assignTemp $ cmmOffsetExprW (cmmOffsetB src arrPtrsHdrSize)
             src_off

    emitMemcpyCall dst_p src_p (n `cmmMulWord` wordSize)
        (CmmLit (mkIntCLit wORD_SIZE)) live

    emitMemsetCall (cmmOffsetExprW dst_p n)
        (CmmLit (mkIntCLit 1))
        (card_words `cmmMulWord` wordSize)
        (CmmLit (mkIntCLit wORD_SIZE))
        live
    stmtC $ CmmAssign (CmmLocal res_r) arr
  where
    arrPtrsHdrSizeW = CmmLit $ mkIntCLit $ fixedHdrSize +
                      (sIZEOF_StgMutArrPtrs_NoHdr `div` wORD_SIZE)
    wordSize = CmmLit (mkIntCLit wORD_SIZE)
    myCapability = CmmReg baseReg `cmmSubWord`
                   CmmLit (mkIntCLit oFFSET_Capability_r)

-- | Takes and offset in the destination array, the base address of
-- the card table, and the number of elements affected (*not* the
-- number of cards).  Marks the relevant cards as dirty.
emitSetCards :: CmmExpr -> CmmExpr -> CmmExpr -> StgLiveVars -> Code
emitSetCards dst_start dst_cards_start n live = do
    start_card <- assignTemp $ card dst_start
    emitMemsetCall (dst_cards_start `cmmAddWord` start_card)
        (CmmLit (mkIntCLit 1))
        ((card (dst_start `cmmAddWord` n) `cmmSubWord` start_card)
         `cmmAddWord` CmmLit (mkIntCLit 1))
        (CmmLit (mkIntCLit wORD_SIZE))
        live
  where
    -- Convert an element index to a card index
    card i = i `cmmUShrWord` (CmmLit (mkIntCLit mUT_ARR_PTRS_CARD_BITS))

-- | Emit a call to @memcpy@.
emitMemcpyCall :: CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr -> StgLiveVars
               -> Code
emitMemcpyCall dst src n align live = do
    vols <- getVolatileRegs live
    emitForeignCall' PlayRisky
        [{-no results-}]
        (CmmPrim MO_Memcpy)
        [ (CmmHinted dst AddrHint)
        , (CmmHinted src AddrHint)
        , (CmmHinted n NoHint)
        , (CmmHinted align NoHint)
        ]
        (Just vols)
        NoC_SRT -- No SRT b/c we do PlayRisky
        CmmMayReturn

-- | Emit a call to @memmove@.
emitMemmoveCall :: CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr -> StgLiveVars
                -> Code
emitMemmoveCall dst src n align live = do
    vols <- getVolatileRegs live
    emitForeignCall' PlayRisky
        [{-no results-}]
        (CmmPrim MO_Memmove)
        [ (CmmHinted dst AddrHint)
        , (CmmHinted src AddrHint)
        , (CmmHinted n NoHint)
        , (CmmHinted align NoHint)
        ]
        (Just vols)
        NoC_SRT -- No SRT b/c we do PlayRisky
        CmmMayReturn

-- | Emit a call to @memset@.  The second argument must be a word but
-- its value must fit inside an unsigned char.
emitMemsetCall :: CmmExpr -> CmmExpr -> CmmExpr -> CmmExpr -> StgLiveVars
               -> Code
emitMemsetCall dst c n align live = do
    vols <- getVolatileRegs live
    emitForeignCall' PlayRisky
        [{-no results-}]
        (CmmPrim MO_Memset)
        [ (CmmHinted dst AddrHint)
        , (CmmHinted c NoHint)
        , (CmmHinted n NoHint)
        , (CmmHinted align NoHint)
        ]
        (Just vols)
        NoC_SRT -- No SRT b/c we do PlayRisky
        CmmMayReturn

-- | Emit a call to @allocate@.
emitAllocateCall :: LocalReg -> CmmExpr -> CmmExpr -> StgLiveVars -> Code
emitAllocateCall res cap n live = do
    vols <- getVolatileRegs live
    emitForeignCall' PlayRisky
        [CmmHinted res AddrHint]
        (CmmCallee allocate CCallConv)
        [ (CmmHinted cap AddrHint)
        , (CmmHinted n NoHint)
        ]
        (Just vols)
        NoC_SRT -- No SRT b/c we do PlayRisky
        CmmMayReturn
  where
    allocate = CmmLit (CmmLabel (mkForeignLabel (fsLit "allocate") Nothing
                                 ForeignLabelInExternalPackage IsFunction))