% % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % % $Id: CgHeapery.lhs,v 1.30 2002/02/05 14:39:24 simonpj Exp $ % \section[CgHeapery]{Heap management functions} \begin{code} module CgHeapery ( fastEntryChecks, altHeapCheck, thunkChecks, allocDynClosure, inPlaceAllocDynClosure -- new functions, basically inserting macro calls into Code -- HWL ,fetchAndReschedule, yield ) where #include "HsVersions.h" import AbsCSyn import CLabel import CgMonad import CgStackery ( getFinalStackHW, mkTaggedStkAmodes, mkTagAssts ) import AbsCUtils ( mkAbstractCs, getAmodeRep ) import CgUsages ( getVirtAndRealHp, getRealSp, setVirtHp, setRealHp, initHeapUsage ) import ClosureInfo ( closureSize, closureGoodStuffSize, slopSize, allocProfilingMsg, ClosureInfo ) import PrimRep ( PrimRep(..), isFollowableRep ) import Unique ( Unique ) import CmdLineOpts ( opt_GranMacros ) import GlaExts import Outputable #ifdef DEBUG import PprAbsC ( pprMagicId ) -- tmp #endif \end{code} %************************************************************************ %* * \subsection[CgHeapery-heap-overflow]{Heap overflow checking} %* * %************************************************************************ The new code for heapChecks. For GrAnSim the code for doing a heap check and doing a context switch has been separated. Especially, the HEAP_CHK macro only performs a heap check. THREAD_CONTEXT_SWITCH should be used for doing a context switch. GRAN_FETCH_AND_RESCHEDULE must be put at the beginning of every slow entry code in order to simulate the fetching of closures. If fetching is necessary (i.e. current closure is not local) then an automatic context switch is done. ----------------------------------------------------------------------------- A heap/stack check at a fast entry point. \begin{code} fastEntryChecks :: [MagicId] -- Live registers -> [(VirtualSpOffset,Int)] -- stack slots to tag -> CLabel -- return point -> Bool -- node points to closure -> Code -> Code fastEntryChecks regs tags ret node_points code = mkTagAssts tags `thenFC` \tag_assts -> getFinalStackHW (\ spHw -> getRealSp `thenFC` \ sp -> let stk_words = spHw - sp in initHeapUsage (\ hHw -> getTickyCtrLabel `thenFC` \ ticky_ctr -> ( if all_pointers then -- heap checks are quite easy -- HWL: gran-yield immediately before heap check proper --(if node `elem` regs -- then yield regs True -- else absC AbsCNop ) `thenC` absC (checking_code stk_words hHw tag_assts free_reg (length regs) ticky_ctr) else -- they are complicated -- save all registers on the stack and adjust the stack pointer. -- ToDo: find the initial all-pointer segment and don't save them. mkTaggedStkAmodes sp addrmode_regs `thenFC` \(new_sp, stk_assts, more_tag_assts) -> -- only let the extra stack assignments affect the stack -- high water mark if we were doing a stack check anyway; -- otherwise we end up generating unnecessary stack checks. -- Careful about knot-tying loops! let real_stk_words = if new_sp - sp > stk_words && stk_words /= 0 then new_sp - sp else stk_words in let adjust_sp = CAssign (CReg Sp) (CAddr (spRel sp new_sp)) in absC (checking_code real_stk_words hHw (mkAbstractCs [tag_assts, stk_assts, more_tag_assts, adjust_sp]) (CReg node) 0 ticky_ctr) ) `thenC` setRealHp hHw `thenC` code)) where checking_code stk hp assts ret regs ctr = mkAbstractCs [ real_check, if hp == 0 then AbsCNop else profCtrAbsC SLIT("TICK_ALLOC_HEAP") [ mkIntCLit hp, CLbl ctr DataPtrRep ] ] where real_check | node_points = do_checks_np stk hp assts (regs+1) | otherwise = do_checks stk hp assts ret regs -- When node points to the closure for the function: do_checks_np :: Int -- stack headroom -> Int -- heap headroom -> AbstractC -- assignments to perform on failure -> Int -- number of pointer registers live -> AbstractC do_checks_np 0 0 _ _ = AbsCNop do_checks_np 0 hp_words tag_assts ptrs = CCheck HP_CHK_NP [ mkIntCLit hp_words, mkIntCLit ptrs ] tag_assts do_checks_np stk_words 0 tag_assts ptrs = CCheck STK_CHK_NP [ mkIntCLit stk_words, mkIntCLit ptrs ] tag_assts do_checks_np stk_words hp_words tag_assts ptrs = CCheck HP_STK_CHK_NP [ mkIntCLit stk_words, mkIntCLit hp_words, mkIntCLit ptrs ] tag_assts -- When node doesn't point to the closure (we need an explicit retn addr) do_checks :: Int -- stack headroom -> Int -- heap headroom -> AbstractC -- assignments to perform on failure -> CAddrMode -- a register to hold the retn addr. -> Int -- number of pointer registers live -> AbstractC do_checks 0 0 _ _ _ = AbsCNop do_checks 0 hp_words tag_assts ret_reg ptrs = CCheck HP_CHK [ mkIntCLit hp_words, CLbl ret CodePtrRep, ret_reg, mkIntCLit ptrs ] tag_assts do_checks stk_words 0 tag_assts ret_reg ptrs = CCheck STK_CHK [ mkIntCLit stk_words, CLbl ret CodePtrRep, ret_reg, mkIntCLit ptrs ] tag_assts do_checks stk_words hp_words tag_assts ret_reg ptrs = CCheck HP_STK_CHK [ mkIntCLit stk_words, mkIntCLit hp_words, CLbl ret CodePtrRep, ret_reg, mkIntCLit ptrs ] tag_assts free_reg = case length regs + 1 of I# x -> CReg (VanillaReg PtrRep x) all_pointers = all pointer regs pointer (VanillaReg rep _) = isFollowableRep rep pointer _ = False addrmode_regs = map CReg regs -- Checking code for thunks is just a special case of fast entry points: thunkChecks :: CLabel -> Bool -> Code -> Code thunkChecks ret node_points code = fastEntryChecks [] [] ret node_points code \end{code} Heap checks in a case alternative are nice and easy, provided this is a bog-standard algebraic case. We have in our hand: * one return address, on the stack, * one return value, in Node. the canned code for this heap check failure just pushes Node on the stack, saying 'EnterGHC' to return. The scheduler will return by entering the top value on the stack, which in turn will return through the return address, getting us back to where we were. This is therefore only valid if the return value is *lifted* (just being boxed isn't good enough). Only a PtrRep will do. For primitive returns, we have an unlifted value in some register (either R1 or FloatReg1 or DblReg1). This means using specialised heap-check code for these cases. For unboxed tuple returns, there are an arbitrary number of possibly unboxed return values, some of which will be in registers, and the others will be on the stack, with gaps left for tagging the unboxed objects. If a heap check is required, we need to fill in these tags. The code below will cover all cases for the x86 architecture (where R1 is the only VanillaReg ever used). For other architectures, we'll have to do something about saving and restoring the other registers. \begin{code} altHeapCheck :: Bool -- is an algebraic alternative -> [MagicId] -- live registers -> [(VirtualSpOffset,Int)] -- stack slots to tag -> AbstractC -> Maybe Unique -- uniq of ret address (possibly) -> Code -> Code -- unboxed tuple alternatives and let-no-escapes (the two most annoying -- constructs to generate code for!): altHeapCheck is_fun regs tags fail_code (Just ret_addr) code = mkTagAssts tags `thenFC` \tag_assts1 -> let tag_assts = mkAbstractCs [fail_code, tag_assts1] in initHeapUsage (\ hHw -> do_heap_chk hHw tag_assts `thenC` code) where do_heap_chk words_required tag_assts = getTickyCtrLabel `thenFC` \ ctr -> absC ( if words_required == 0 then AbsCNop else mkAbstractCs [ checking_code tag_assts, profCtrAbsC SLIT("TICK_ALLOC_HEAP") [ mkIntCLit words_required, CLbl ctr DataPtrRep ] ] ) `thenC` setRealHp words_required where non_void_regs = filter (/= VoidReg) regs checking_code tag_assts = case non_void_regs of {- no: there might be stuff on top of the retn. addr. on the stack. [{-no regs-}] -> CCheck HP_CHK_NOREGS [mkIntCLit words_required] tag_assts -} -- this will cover all cases for x86 [VanillaReg rep 1#] | isFollowableRep rep -> CCheck HP_CHK_UT_ALT [mkIntCLit words_required, mkIntCLit 1, mkIntCLit 0, CReg (VanillaReg RetRep 2#), CLbl (mkReturnInfoLabel ret_addr) RetRep] tag_assts | otherwise -> CCheck HP_CHK_UT_ALT [mkIntCLit words_required, mkIntCLit 0, mkIntCLit 1, CReg (VanillaReg RetRep 2#), CLbl (mkReturnInfoLabel ret_addr) RetRep] tag_assts several_regs -> let liveness = mkRegLiveness several_regs in CCheck HP_CHK_GEN [mkIntCLit words_required, mkIntCLit (I# (word2Int# liveness)), -- HP_CHK_GEN needs a direct return address, -- not an info table (might be different if -- we're not assembly-mangling/tail-jumping etc.) CLbl (mkReturnPtLabel ret_addr) RetRep] tag_assts -- normal algebraic and primitive case alternatives: altHeapCheck is_fun regs [] AbsCNop Nothing code = initHeapUsage (\ hHw -> do_heap_chk hHw `thenC` code) where do_heap_chk :: HeapOffset -> Code do_heap_chk words_required = getTickyCtrLabel `thenFC` \ ctr -> absC ( if words_required == 0 then AbsCNop else mkAbstractCs [ checking_code, profCtrAbsC SLIT("TICK_ALLOC_HEAP") [ mkIntCLit words_required, CLbl ctr DataPtrRep ] ] ) `thenC` setRealHp words_required where non_void_regs = filter (/= VoidReg) regs checking_code = case non_void_regs of -- No regs live: probably a Void return [] -> CCheck HP_CHK_NOREGS [mkIntCLit words_required] AbsCNop -- The SEQ case (polymophic/function typed case branch) -- We need this case because the closure in Node won't return -- directly when we enter it (it could be a function), so the -- heap check code needs to push a seq frame on top of the stack. [VanillaReg rep 1#] | rep == PtrRep && is_fun -> CCheck HP_CHK_SEQ_NP [mkIntCLit words_required, mkIntCLit 1{-regs live-}] AbsCNop -- R1 is lifted (the common case) [VanillaReg rep 1#] | rep == PtrRep -> CCheck HP_CHK_NP [mkIntCLit words_required, mkIntCLit 1{-regs live-}] AbsCNop -- R1 is boxed, but unlifted | isFollowableRep rep -> CCheck HP_CHK_UNPT_R1 [mkIntCLit words_required] AbsCNop -- R1 is unboxed | otherwise -> CCheck HP_CHK_UNBX_R1 [mkIntCLit words_required] AbsCNop -- FloatReg1 [FloatReg 1#] -> CCheck HP_CHK_F1 [mkIntCLit words_required] AbsCNop -- DblReg1 [DoubleReg 1#] -> CCheck HP_CHK_D1 [mkIntCLit words_required] AbsCNop -- LngReg1 [LongReg _ 1#] -> CCheck HP_CHK_L1 [mkIntCLit words_required] AbsCNop #ifdef DEBUG _ -> panic ("CgHeapery.altHeapCheck: unimplemented heap-check, live regs = " ++ showSDoc (sep (map pprMagicId non_void_regs))) #endif -- build up a bitmap of the live pointer registers #if __GLASGOW_HASKELL__ >= 503 shiftL = uncheckedShiftL# #else shiftL = shiftL# #endif mkRegLiveness :: [MagicId] -> Word# mkRegLiveness [] = int2Word# 0# mkRegLiveness (VanillaReg rep i : regs) | isFollowableRep rep = ((int2Word# 1#) `shiftL` (i -# 1#)) `or#` mkRegLiveness regs mkRegLiveness (_ : regs) = mkRegLiveness regs -- The two functions below are only used in a GranSim setup -- Emit macro for simulating a fetch and then reschedule fetchAndReschedule :: [MagicId] -- Live registers -> Bool -- Node reqd? -> Code fetchAndReschedule regs node_reqd = if (node `elem` regs || node_reqd) then fetch_code `thenC` reschedule_code else absC AbsCNop where liveness_mask = mkRegLiveness regs reschedule_code = absC (CMacroStmt GRAN_RESCHEDULE [ mkIntCLit (I# (word2Int# liveness_mask)), mkIntCLit (if node_reqd then 1 else 0)]) --HWL: generate GRAN_FETCH macro for GrAnSim -- currently GRAN_FETCH and GRAN_FETCH_AND_RESCHEDULE are miai fetch_code = absC (CMacroStmt GRAN_FETCH []) \end{code} The @GRAN_YIELD@ macro is taken from JSM's code for Concurrent Haskell. It allows to context-switch at places where @node@ is not alive (it uses the @Continue@ rather than the @EnterNodeCode@ function in the RTS). We emit this kind of macro at the beginning of the following kinds of basic bocks: \begin{itemize} \item Slow entry code where node is not alive (see @CgClosure.lhs@). Normally we use @fetchAndReschedule@ at a slow entry code. \item Fast entry code (see @CgClosure.lhs@). \item Alternatives in case expressions (@CLabelledCode@ structures), provided that they are not inlined (see @CgCases.lhs@). These alternatives will be turned into separate functions. \end{itemize} \begin{code} yield :: [MagicId] -- Live registers -> Bool -- Node reqd? -> Code yield regs node_reqd = if opt_GranMacros && node_reqd then yield_code else absC AbsCNop where liveness_mask = mkRegLiveness regs yield_code = absC (CMacroStmt GRAN_YIELD [mkIntCLit (I# (word2Int# liveness_mask))]) \end{code} %************************************************************************ %* * \subsection[initClosure]{Initialise a dynamic closure} %* * %************************************************************************ @allocDynClosure@ puts the thing in the heap, and modifies the virtual Hp to account for this. \begin{code} allocDynClosure :: ClosureInfo -> CAddrMode -- Cost Centre to stick in the object -> CAddrMode -- Cost Centre to blame for this alloc -- (usually the same; sometimes "OVERHEAD") -> [(CAddrMode, VirtualHeapOffset)] -- Offsets from start of the object -- ie Info ptr has offset zero. -> FCode VirtualHeapOffset -- Returns virt offset of object allocDynClosure closure_info use_cc blame_cc amodes_with_offsets = getVirtAndRealHp `thenFC` \ (virtHp, realHp) -> -- FIND THE OFFSET OF THE INFO-PTR WORD -- virtHp points to last allocated word, ie 1 *before* the -- info-ptr word of new object. let info_offset = virtHp + 1 -- do_move IS THE ASSIGNMENT FUNCTION do_move (amode, offset_from_start) = CAssign (CVal (hpRel realHp (info_offset + offset_from_start)) (getAmodeRep amode)) amode in -- SAY WHAT WE ARE ABOUT TO DO profCtrC (allocProfilingMsg closure_info) [mkIntCLit (closureGoodStuffSize closure_info), mkIntCLit slop_size] `thenC` -- GENERATE THE CODE absC ( mkAbstractCs ( [ CInitHdr closure_info (CAddr (hpRel realHp info_offset)) use_cc closure_size ] ++ (map do_move amodes_with_offsets))) `thenC` -- BUMP THE VIRTUAL HEAP POINTER setVirtHp (virtHp + closure_size) `thenC` -- RETURN PTR TO START OF OBJECT returnFC info_offset where closure_size = closureSize closure_info slop_size = slopSize closure_info \end{code} Occasionally we can update a closure in place instead of allocating new space for it. This is the function that does the business, assuming: - node points to the closure to be overwritten - the new closure doesn't contain any pointers if we're using a generational collector. \begin{code} inPlaceAllocDynClosure :: ClosureInfo -> CAddrMode -- Pointer to beginning of closure -> CAddrMode -- Cost Centre to stick in the object -> [(CAddrMode, VirtualHeapOffset)] -- Offsets from start of the object -- ie Info ptr has offset zero. -> Code inPlaceAllocDynClosure closure_info head use_cc amodes_with_offsets = let -- do_move IS THE ASSIGNMENT FUNCTION do_move (amode, offset_from_start) = CAssign (CVal (CIndex head (mkIntCLit offset_from_start) WordRep) (getAmodeRep amode)) amode in -- GENERATE THE CODE absC ( mkAbstractCs ( [ CInitHdr closure_info head use_cc 0{-no alloc-} ] ++ (map do_move amodes_with_offsets))) \end{code}