% % (c) The University of Glasgow 2006 % (c) The GRASP Project, Glasgow University, 1992-1998 % \section[CgCon]{Code generation for constructors} This module provides the support code for @StgToAbstractC@ to deal with {\em constructors} on the RHSs of let(rec)s. See also @CgClosure@, which deals with closures. \begin{code} module CgCon ( cgTopRhsCon, buildDynCon, bindConArgs, bindUnboxedTupleComponents, cgReturnDataCon, cgTyCon ) where #include "HsVersions.h" import CgMonad import StgSyn import CgBindery import CgStackery import CgUtils import CgCallConv import CgHeapery import CgTailCall import CgProf import CgTicky import CgInfoTbls import CLabel import ClosureInfo import OldCmmUtils import OldCmm import SMRep import CostCentre import TyCon import DataCon import Id import IdInfo import Type import PrelInfo import Outputable import ListSetOps import Util import Module import DynFlags import FastString import Platform import Control.Monad \end{code} %************************************************************************ %* * \subsection[toplevel-constructors]{Top-level constructors} %* * %************************************************************************ \begin{code} cgTopRhsCon :: Id -- Name of thing bound to this RHS -> DataCon -- Id -> [StgArg] -- Args -> FCode (Id, CgIdInfo) cgTopRhsCon id con args = do { dflags <- getDynFlags ; when (platformOS (targetPlatform dflags) == OSMinGW32) $ -- Windows DLLs have a problem with static cross-DLL refs. ASSERT( not (isDllConApp dflags con args) ) return () ; ASSERT( args `lengthIs` dataConRepRepArity con ) return () -- LAY IT OUT ; amodes <- getArgAmodes args ; let name = idName id lf_info = mkConLFInfo con closure_label = mkClosureLabel name $ idCafInfo id caffy = any stgArgHasCafRefs args (closure_info, amodes_w_offsets) = layOutStaticConstr dflags con amodes closure_rep = mkStaticClosureFields dflags closure_info dontCareCCS -- Because it's static data caffy -- Has CAF refs payload payload = map get_lit amodes_w_offsets get_lit (CmmLit lit, _offset) = lit get_lit other = pprPanic "CgCon.get_lit" (ppr other) -- NB1: amodes_w_offsets is sorted into ptrs first, then non-ptrs -- NB2: all the amodes should be Lits! -- BUILD THE OBJECT ; emitDataLits closure_label closure_rep -- RETURN ; returnFC (id, taggedStableIdInfo dflags id (mkLblExpr closure_label) lf_info con) } \end{code} %************************************************************************ %* * %* non-top-level constructors * %* * %************************************************************************ \subsection[code-for-constructors]{The code for constructors} \begin{code} buildDynCon :: Id -- Name of the thing to which this constr will -- be bound -> CostCentreStack -- Where to grab cost centre from; -- current CCS if currentOrSubsumedCCS -> DataCon -- The data constructor -> [(CgRep,CmmExpr)] -- Its args -> FCode CgIdInfo -- Return details about how to find it buildDynCon binder ccs con args = do dflags <- getDynFlags buildDynCon' dflags (targetPlatform dflags) binder ccs con args buildDynCon' :: DynFlags -> Platform -> Id -> CostCentreStack -> DataCon -> [(CgRep,CmmExpr)] -> FCode CgIdInfo -- We used to pass a boolean indicating whether all the -- args were of size zero, so we could use a static -- construtor; but I concluded that it just isn't worth it. -- Now I/O uses unboxed tuples there just aren't any constructors -- with all size-zero args. -- -- The reason for having a separate argument, rather than looking at -- the addr modes of the args is that we may be in a "knot", and -- premature looking at the args will cause the compiler to black-hole! \end{code} First we deal with the case of zero-arity constructors. Now, they will probably be unfolded, so we don't expect to see this case much, if at all, but it does no harm, and sets the scene for characters. In the case of zero-arity constructors, or, more accurately, those which have exclusively size-zero (VoidRep) args, we generate no code at all. \begin{code} buildDynCon' dflags _ binder _ con [] = returnFC (taggedStableIdInfo dflags binder (mkLblExpr (mkClosureLabel (dataConName con) (idCafInfo binder))) (mkConLFInfo con) con) \end{code} The following three paragraphs about @Char@-like and @Int@-like closures are obsolete, but I don't understand the details well enough to properly word them, sorry. I've changed the treatment of @Char@s to be analogous to @Int@s: only a subset is preallocated, because @Char@ has now 31 bits. Only literals are handled here. -- Qrczak Now for @Char@-like closures. We generate an assignment of the address of the closure to a temporary. It would be possible simply to generate no code, and record the addressing mode in the environment, but we'd have to be careful if the argument wasn't a constant --- so for simplicity we just always asssign to a temporary. Last special case: @Int@-like closures. We only special-case the situation in which the argument is a literal in the range @mIN_INTLIKE@..@mAX_INTLILKE@. NB: for @Char@-like closures we can work with any old argument, but for @Int@-like ones the argument has to be a literal. Reason: @Char@ like closures have an argument type which is guaranteed in range. Because of this, we use can safely return an addressing mode. We don't support this optimisation when compiling into Windows DLLs yet because they don't support cross package data references well. \begin{code} buildDynCon' dflags platform binder _ con [arg_amode] | maybeIntLikeCon con , platformOS platform /= OSMinGW32 || not (gopt Opt_PIC dflags) , (_, CmmLit (CmmInt val _)) <- arg_amode , let val_int = (fromIntegral val) :: Int , val_int <= mAX_INTLIKE dflags && val_int >= mIN_INTLIKE dflags = do { let intlike_lbl = mkCmmClosureLabel rtsPackageId (fsLit "stg_INTLIKE") offsetW = (val_int - mIN_INTLIKE dflags) * (fixedHdrSize dflags + 1) -- INTLIKE closures consist of a header and one word payload intlike_amode = CmmLit (cmmLabelOffW dflags intlike_lbl offsetW) ; returnFC (taggedStableIdInfo dflags binder intlike_amode (mkConLFInfo con) con) } buildDynCon' dflags platform binder _ con [arg_amode] | maybeCharLikeCon con , platformOS platform /= OSMinGW32 || not (gopt Opt_PIC dflags) , (_, CmmLit (CmmInt val _)) <- arg_amode , let val_int = (fromIntegral val) :: Int , val_int <= mAX_CHARLIKE dflags && val_int >= mIN_CHARLIKE dflags = do { let charlike_lbl = mkCmmClosureLabel rtsPackageId (fsLit "stg_CHARLIKE") offsetW = (val_int - mIN_CHARLIKE dflags) * (fixedHdrSize dflags + 1) -- CHARLIKE closures consist of a header and one word payload charlike_amode = CmmLit (cmmLabelOffW dflags charlike_lbl offsetW) ; returnFC (taggedStableIdInfo dflags binder charlike_amode (mkConLFInfo con) con) } \end{code} Now the general case. \begin{code} buildDynCon' dflags _ binder ccs con args = do { ; let (closure_info, amodes_w_offsets) = layOutDynConstr dflags con args ; hp_off <- allocDynClosure closure_info use_cc blame_cc amodes_w_offsets ; returnFC (taggedHeapIdInfo dflags binder hp_off lf_info con) } where lf_info = mkConLFInfo con use_cc -- cost-centre to stick in the object | isCurrentCCS ccs = curCCS | otherwise = panic "buildDynCon: non-current CCS not implemented" blame_cc = use_cc -- cost-centre on which to blame the alloc (same) \end{code} %************************************************************************ %* * %* constructor-related utility function: * %* bindConArgs is called from cgAlt of a case * %* * %************************************************************************ \subsection[constructor-utilities]{@bindConArgs@: constructor-related utility} @bindConArgs@ $con args$ augments the environment with bindings for the binders $args$, assuming that we have just returned from a @case@ which found a $con$. \begin{code} bindConArgs :: DataCon -> [Id] -> Code bindConArgs con args = do dflags <- getDynFlags let -- The binding below forces the masking out of the tag bits -- when accessing the constructor field. bind_arg (arg, offset) = bindNewToUntagNode arg offset (mkLFArgument arg) (tagForCon dflags con) (_, args_w_offsets) = layOutDynConstr dflags con (addIdReps args) -- ASSERT(not (isUnboxedTupleCon con)) return () mapCs bind_arg args_w_offsets \end{code} Unboxed tuples are handled slightly differently - the object is returned in registers and on the stack instead of the heap. \begin{code} bindUnboxedTupleComponents :: [Id] -- Args -> FCode ([(Id,GlobalReg)], -- Regs assigned WordOff, -- Number of pointer stack slots WordOff, -- Number of non-pointer stack slots VirtualSpOffset) -- Offset of return address slot -- (= realSP on entry) bindUnboxedTupleComponents args = do { dflags <- getDynFlags ; vsp <- getVirtSp ; rsp <- getRealSp -- Assign as many components as possible to registers ; let (reg_args, stk_args) = assignReturnRegs dflags (addIdReps args) -- Separate the rest of the args into pointers and non-pointers (ptr_args, nptr_args) = separateByPtrFollowness stk_args -- Allocate the rest on the stack -- The real SP points to the return address, above which any -- leftover unboxed-tuple components will be allocated (ptr_sp, ptr_offsets) = mkVirtStkOffsets dflags rsp ptr_args (nptr_sp, nptr_offsets) = mkVirtStkOffsets dflags ptr_sp nptr_args ptrs = ptr_sp - rsp nptrs = nptr_sp - ptr_sp -- The stack pointer points to the last stack-allocated component ; setRealAndVirtualSp nptr_sp -- We have just allocated slots starting at real SP + 1, and set the new -- virtual SP to the topmost allocated slot. -- If the virtual SP started *below* the real SP, we've just jumped over -- some slots that won't be in the free-list, so put them there -- This commonly happens because we've freed the return-address slot -- (trimming back the virtual SP), but the real SP still points to that slot ; freeStackSlots [vsp+1,vsp+2 .. rsp] ; bindArgsToRegs reg_args ; bindArgsToStack ptr_offsets ; bindArgsToStack nptr_offsets ; returnFC (reg_args, ptrs, nptrs, rsp) } \end{code} %************************************************************************ %* * Actually generate code for a constructor return %* * %************************************************************************ Note: it's the responsibility of the @cgReturnDataCon@ caller to be sure the @amodes@ passed don't conflict with each other. \begin{code} cgReturnDataCon :: DataCon -> [(CgRep, CmmExpr)] -> Code cgReturnDataCon con amodes = do dflags <- getDynFlags if isUnboxedTupleCon con then returnUnboxedTuple amodes -- when profiling we can't shortcut here, we have to enter the closure -- for it to be marked as "used" for LDV profiling. else if gopt Opt_SccProfilingOn dflags then build_it_then (enter_it dflags) else ASSERT( amodes `lengthIs` dataConRepRepArity con ) do { EndOfBlockInfo _ sequel <- getEndOfBlockInfo ; case sequel of CaseAlts _ (Just (alts, deflt_lbl)) bndr -> -- Ho! We know the constructor so we can -- go straight to the right alternative case assocMaybe alts (dataConTagZ con) of { Just join_lbl -> build_it_then (jump_to join_lbl); Nothing -- Special case! We're returning a constructor to the default case -- of an enclosing case. For example: -- -- case (case e of (a,b) -> C a b) of -- D x -> ... -- y -> ...... -- -- In this case, -- if the default is a non-bind-default (ie does not use y), -- then we should simply jump to the default join point; | isDeadBinder bndr -> performReturn (jump_to deflt_lbl) | otherwise -> build_it_then (jump_to deflt_lbl) } _otherwise -- The usual case -> build_it_then $ emitReturnInstr node_live } where node_live = Just [node] enter_it dflags = stmtsC [ CmmAssign nodeReg (cmmUntag dflags (CmmReg nodeReg)), CmmJump (entryCode dflags $ closureInfoPtr dflags $ CmmReg nodeReg) node_live ] jump_to lbl = stmtC $ CmmJump (CmmLit lbl) node_live build_it_then return_code = do { -- BUILD THE OBJECT IN THE HEAP -- The first "con" says that the name bound to this -- closure is "con", which is a bit of a fudge, but it only -- affects profiling -- This Id is also used to get a unique for a -- temporary variable, if the closure is a CHARLIKE. -- funnily enough, this makes the unique always come -- out as '54' :-) tickyReturnNewCon (length amodes) ; idinfo <- buildDynCon (dataConWorkId con) currentCCS con amodes ; amode <- idInfoToAmode idinfo ; checkedAbsC (CmmAssign nodeReg amode) ; performReturn return_code } \end{code} %************************************************************************ %* * Generating static stuff for algebraic data types %* * %************************************************************************ [These comments are rather out of date] \begin{tabular}{lll} Info tbls & Macro & Kind of constructor \\ \hline info & @CONST_INFO_TABLE@& Zero arity (no info -- compiler uses static closure)\\ info & @CHARLIKE_INFO_TABLE@& Charlike (no info -- compiler indexes fixed array)\\ info & @INTLIKE_INFO_TABLE@& Intlike; the one macro generates both info tbls\\ info & @SPEC_INFO_TABLE@& SPECish, and bigger than or equal to @MIN_UPD_SIZE@\\ info & @GEN_INFO_TABLE@& GENish (hence bigger than or equal to @MIN_UPD_SIZE@)\\ \end{tabular} Possible info tables for constructor con: \begin{description} \item[@_con_info@:] Used for dynamically let(rec)-bound occurrences of the constructor, and for updates. For constructors which are int-like, char-like or nullary, when GC occurs, the closure tries to get rid of itself. \item[@_static_info@:] Static occurrences of the constructor macro: @STATIC_INFO_TABLE@. \end{description} For zero-arity constructors, \tr{con}, we NO LONGER generate a static closure; it's place is taken by the top level defn of the constructor. For charlike and intlike closures there is a fixed array of static closures predeclared. \begin{code} cgTyCon :: TyCon -> FCode CmmGroup -- each constructor gets a separate CmmGroup cgTyCon tycon = do { dflags <- getDynFlags ; constrs <- mapM (getCmm . cgDataCon) (tyConDataCons tycon) -- Generate a table of static closures for an enumeration type -- Put the table after the data constructor decls, because the -- datatype closure table (for enumeration types) -- to (say) PrelBase_$wTrue_closure, which is defined in code_stuff -- Note that the closure pointers are tagged. -- XXX comment says to put table after constructor decls, but -- code appears to put it before --- NR 16 Aug 2007 ; extra <- if isEnumerationTyCon tycon then do tbl <- getCmm (emitRODataLits "cgTyCon" (mkLocalClosureTableLabel (tyConName tycon) NoCafRefs) [ CmmLabelOff (mkLocalClosureLabel (dataConName con) NoCafRefs) (tagForCon dflags con) | con <- tyConDataCons tycon]) return [tbl] else return [] ; return (concat (extra ++ constrs)) } \end{code} Generate the entry code, info tables, and (for niladic constructor) the static closure, for a constructor. \begin{code} cgDataCon :: DataCon -> Code cgDataCon data_con = do { dflags <- getDynFlags -- Don't need any dynamic closure code for zero-arity constructors ; let -- To allow the debuggers, interpreters, etc to cope with -- static data structures (ie those built at compile -- time), we take care that info-table contains the -- information we need. (static_cl_info, _) = layOutStaticConstr dflags data_con arg_reps (dyn_cl_info, arg_things) = layOutDynConstr dflags data_con arg_reps emit_info cl_info ticky_code = do { code_blks <- getCgStmts the_code ; emitClosureCodeAndInfoTable cl_info [] code_blks } where the_code = do { _ <- ticky_code ; ldvEnter (CmmReg nodeReg) ; body_code } arg_reps :: [(CgRep, UnaryType)] arg_reps = [(typeCgRep rep_ty, rep_ty) | ty <- dataConRepArgTys data_con, rep_ty <- flattenRepType (repType ty)] body_code = do { -- NB: We don't set CC when entering data (WDP 94/06) tickyReturnOldCon (length arg_things) -- The case continuation code is expecting a tagged pointer ; stmtC (CmmAssign nodeReg (tagCons dflags data_con (CmmReg nodeReg))) ; performReturn $ emitReturnInstr (Just []) } -- noStmts: Ptr to thing already in Node ; whenC (not (isNullaryRepDataCon data_con)) (emit_info dyn_cl_info tickyEnterDynCon) -- Dynamic-Closure first, to reduce forward references ; emit_info static_cl_info tickyEnterStaticCon } \end{code}