2 % (c) The GRASP Project, Glasgow University, 1992-1998
4 \section[CgCon]{Code generation for constructors}
6 This module provides the support code for @StgToAbstractC@ to deal
7 with {\em constructors} on the RHSs of let(rec)s. See also
8 @CgClosure@, which deals with closures.
12 cgTopRhsCon, buildDynCon,
13 bindConArgs, bindUnboxedTupleComponents,
17 #include "HsVersions.h"
23 import AbsCUtils ( getAmodeRep )
24 import CgBindery ( getArgAmodes, bindNewToNode,
26 idInfoToAmode, stableAmodeIdInfo,
27 heapIdInfo, CgIdInfo, bindNewToStack
29 import CgStackery ( mkTaggedVirtStkOffsets, freeStackSlots,
32 import CgUsages ( getRealSp, getVirtSp, setRealAndVirtualSp,
34 import CgRetConv ( assignRegs )
35 import Constants ( mAX_INTLIKE, mIN_INTLIKE, mAX_CHARLIKE, mIN_CHARLIKE,
37 import CgHeapery ( allocDynClosure, inPlaceAllocDynClosure )
38 import CgTailCall ( performReturn, mkStaticAlgReturnCode, doTailCall,
39 mkUnboxedTupleReturnCode )
40 import CLabel ( mkClosureLabel )
41 import ClosureInfo ( mkConLFInfo, mkLFArgument,
42 layOutDynCon, layOutDynClosure,
43 layOutStaticClosure, closureSize
45 import CostCentre ( currentOrSubsumedCCS, dontCareCCS, CostCentreStack,
47 import DataCon ( DataCon, dataConName, dataConTag,
48 isUnboxedTupleCon, isNullaryDataCon, dataConId, dataConWrapId
50 import Id ( Id, idName, idPrimRep )
51 import Literal ( Literal(..) )
52 import PrelInfo ( maybeCharLikeCon, maybeIntLikeCon )
53 import PrimRep ( PrimRep(..), isFollowableRep )
54 import Unique ( Uniquable(..) )
59 %************************************************************************
61 \subsection[toplevel-constructors]{Top-level constructors}
63 %************************************************************************
66 cgTopRhsCon :: Id -- Name of thing bound to this RHS
69 -> FCode (Id, CgIdInfo)
70 cgTopRhsCon id con args
71 = ASSERT(not dynamic_con_or_args) -- checks for litlit args too
74 getArgAmodes args `thenFC` \ amodes ->
77 (closure_info, amodes_w_offsets)
78 = layOutStaticClosure name getAmodeRep amodes lf_info
83 closure_label -- Labelled with the name on lhs of defn
84 closure_info -- Closure is static
86 (map fst amodes_w_offsets)) -- Sorted into ptrs first, then nonptrs
91 returnFC (id, stableAmodeIdInfo id (CLbl closure_label PtrRep) lf_info)
93 lf_info = mkConLFInfo con
94 closure_label = mkClosureLabel name
97 top_ccc = mkCCostCentreStack dontCareCCS -- because it's static data
99 -- stuff needed by the assert pred only.
100 dynamic_con_or_args = isDllConApp con args
103 %************************************************************************
105 %* non-top-level constructors *
107 %************************************************************************
108 \subsection[code-for-constructors]{The code for constructors}
111 buildDynCon :: Id -- Name of the thing to which this constr will
113 -> CostCentreStack -- Where to grab cost centre from;
114 -- current CCS if currentOrSubsumedCCS
115 -> DataCon -- The data constructor
116 -> [CAddrMode] -- Its args
117 -> FCode CgIdInfo -- Return details about how to find it
119 -- We used to pass a boolean indicating whether all the
120 -- args were of size zero, so we could use a static
121 -- construtor; but I concluded that it just isn't worth it.
122 -- Now I/O uses unboxed tuples there just aren't any constructors
123 -- with all size-zero args.
125 -- The reason for having a separate argument, rather than looking at
126 -- the addr modes of the args is that we may be in a "knot", and
127 -- premature looking at the args will cause the compiler to black-hole!
130 First we deal with the case of zero-arity constructors. Now, they
131 will probably be unfolded, so we don't expect to see this case much,
132 if at all, but it does no harm, and sets the scene for characters.
134 In the case of zero-arity constructors, or, more accurately, those
135 which have exclusively size-zero (VoidRep) args, we generate no code
139 buildDynCon binder cc con []
140 = returnFC (stableAmodeIdInfo binder
141 (CLbl (mkClosureLabel (idName (dataConWrapId con))) PtrRep)
145 The following three paragraphs about @Char@-like and @Int@-like
146 closures are obsolete, but I don't understand the details well enough
147 to properly word them, sorry. I've changed the treatment of @Char@s to
148 be analogous to @Int@s: only a subset is preallocated, because @Char@
149 has now 31 bits. Only literals are handled here. -- Qrczak
151 Now for @Char@-like closures. We generate an assignment of the
152 address of the closure to a temporary. It would be possible simply to
153 generate no code, and record the addressing mode in the environment,
154 but we'd have to be careful if the argument wasn't a constant --- so
155 for simplicity we just always asssign to a temporary.
157 Last special case: @Int@-like closures. We only special-case the
158 situation in which the argument is a literal in the range
159 @mIN_INTLIKE@..@mAX_INTLILKE@. NB: for @Char@-like closures we can
160 work with any old argument, but for @Int@-like ones the argument has
161 to be a literal. Reason: @Char@ like closures have an argument type
162 which is guaranteed in range.
164 Because of this, we use can safely return an addressing mode.
167 buildDynCon binder cc con [arg_amode]
168 | maybeIntLikeCon con && in_range_int_lit arg_amode
169 = returnFC (stableAmodeIdInfo binder (CIntLike arg_amode) (mkConLFInfo con))
171 in_range_int_lit (CLit (MachInt val)) = val <= mAX_INTLIKE && val >= mIN_INTLIKE
172 in_range_int_lit _other_amode = False
174 buildDynCon binder cc con [arg_amode]
175 | maybeCharLikeCon con && in_range_char_lit arg_amode
176 = returnFC (stableAmodeIdInfo binder (CCharLike arg_amode) (mkConLFInfo con))
178 in_range_char_lit (CLit (MachChar val)) = val <= mAX_CHARLIKE && val >= mIN_CHARLIKE
179 in_range_char_lit _other_amode = False
182 Now the general case.
185 buildDynCon binder ccs con args
186 = allocDynClosure closure_info use_cc blame_cc amodes_w_offsets `thenFC` \ hp_off ->
187 returnFC (heapIdInfo binder hp_off lf_info)
189 (closure_info, amodes_w_offsets)
190 = layOutDynClosure (idName binder) getAmodeRep args lf_info
191 lf_info = mkConLFInfo con
193 use_cc -- cost-centre to stick in the object
194 = if currentOrSubsumedCCS ccs
195 then CReg CurCostCentre
196 else mkCCostCentreStack ccs
198 blame_cc = use_cc -- cost-centre on which to blame the alloc (same)
202 %************************************************************************
204 %* constructor-related utility function: *
205 %* bindConArgs is called from cgAlt of a case *
207 %************************************************************************
208 \subsection[constructor-utilities]{@bindConArgs@: constructor-related utility}
210 @bindConArgs@ $con args$ augments the environment with bindings for the
211 binders $args$, assuming that we have just returned from a @case@ which
216 :: DataCon -> [Id] -- Constructor and args
220 = ASSERT(not (isUnboxedTupleCon con))
221 mapCs bind_arg args_w_offsets
223 bind_arg (arg, offset) = bindNewToNode arg offset mkLFArgument
224 (_, args_w_offsets) = layOutDynCon con idPrimRep args
227 Unboxed tuples are handled slightly differently - the object is
228 returned in registers and on the stack instead of the heap.
231 bindUnboxedTupleComponents
233 -> FCode ([MagicId], -- regs assigned
234 [(VirtualSpOffset,Int)], -- tag slots
235 Bool) -- any components on stack?
237 bindUnboxedTupleComponents args
238 = -- Assign as many components as possible to registers
239 let (arg_regs, leftovers) = assignRegs [] (map idPrimRep args)
240 (reg_args, stk_args) = splitAt (length arg_regs) args
243 -- Allocate the rest on the stack (ToDo: separate out pointers)
244 getVirtSp `thenFC` \ vsp ->
245 getRealSp `thenFC` \ rsp ->
246 let (top_sp, stk_offsets, tags) =
247 mkTaggedVirtStkOffsets rsp idPrimRep stk_args
250 -- The stack pointer points to the last stack-allocated component
251 setRealAndVirtualSp top_sp `thenC`
253 -- need to explicitly free any empty slots we just jumped over
254 (if vsp < rsp then freeStackSlots [vsp+1 .. rsp] else nopC) `thenC`
256 bindArgsToRegs reg_args arg_regs `thenC`
257 mapCs bindNewToStack stk_offsets `thenC`
258 returnFC (arg_regs,tags, not (null stk_offsets))
261 %************************************************************************
263 \subsubsection[CgRetConv-cgReturnDataCon]{Actually generate code for a constructor return}
265 %************************************************************************
268 Note: it's the responsibility of the @cgReturnDataCon@ caller to be
269 sure the @amodes@ passed don't conflict with each other.
271 cgReturnDataCon :: DataCon -> [CAddrMode] -> Code
273 cgReturnDataCon con amodes
274 = getEndOfBlockInfo `thenFC` \ (EndOfBlockInfo args_sp sequel) ->
278 CaseAlts _ (Just (alts, Just (maybe_deflt, (_,deflt_lbl))))
279 | not (dataConTag con `is_elem` map fst alts)
281 -- Special case! We're returning a constructor to the default case
282 -- of an enclosing case. For example:
284 -- case (case e of (a,b) -> C a b) of
286 -- y -> ...<returning here!>...
289 -- if the default is a non-bind-default (ie does not use y),
290 -- then we should simply jump to the default join point;
293 Nothing -> performReturn AbsCNop {- No reg assts -} jump_to_join_point
294 Just _ -> build_it_then jump_to_join_point
296 is_elem = isIn "cgReturnDataCon"
297 jump_to_join_point sequel = absC (CJump (CLbl deflt_lbl CodePtrRep))
298 -- Ignore the sequel: we've already looked at it above
300 -- If the sequel is an update frame, we might be able to
301 -- do update in place...
303 | not (isNullaryDataCon con) -- no nullary constructors, please
304 && not (any isFollowableRep (map getAmodeRep amodes))
305 -- no ptrs please (generational gc...)
306 && closureSize closure_info <= mIN_UPD_SIZE
307 -- don't know the real size of the
308 -- thunk, so assume mIN_UPD_SIZE
310 -> -- get a new temporary and make it point to the updatee
313 temp = CTemp uniq PtrRep
316 profCtrC SLIT("TICK_UPD_CON_IN_PLACE")
317 [mkIntCLit (length amodes)] `thenC`
319 getSpRelOffset args_sp `thenFC` \ sp_rel ->
321 (CMacroExpr PtrRep UPD_FRAME_UPDATEE [CAddr sp_rel]))
324 -- stomp all over it with the new constructor
325 inPlaceAllocDynClosure closure_info temp (CReg CurCostCentre) stuff
328 -- don't forget to update Su from the update frame
329 absC (CMacroStmt UPDATE_SU_FROM_UPD_FRAME [CAddr sp_rel]) `thenC`
331 -- set Node to point to the closure being returned
332 -- (can't be done earlier: node might conflict with amodes)
333 absC (CAssign (CReg node) temp) `thenC`
335 -- pop the update frame off the stack, and do the proper
337 let new_sp = args_sp - updateFrameSize in
338 setEndOfBlockInfo (EndOfBlockInfo new_sp (OnStack new_sp)) $
339 performReturn (AbsCNop) (mkStaticAlgReturnCode con)
341 where (closure_info, stuff)
342 = layOutDynClosure (dataConName con)
343 getAmodeRep amodes lf_info
345 lf_info = mkConLFInfo con
347 other_sequel -- The usual case
349 | isUnboxedTupleCon con ->
350 -- Return unboxed tuple in registers
351 let (ret_regs, leftovers) =
352 assignRegs [] (map getAmodeRep amodes)
354 profCtrC SLIT("TICK_RET_UNBOXED_TUP")
355 [mkIntCLit (length amodes)] `thenC`
357 doTailCall amodes ret_regs
358 mkUnboxedTupleReturnCode
359 (length leftovers) {- fast args arity -}
360 AbsCNop {-no pending assigments-}
361 Nothing {-not a let-no-escape-}
362 False {-node doesn't point-}
365 build_it_then (mkStaticAlgReturnCode con)
368 move_to_reg :: CAddrMode -> MagicId -> AbstractC
369 move_to_reg src_amode dest_reg = CAssign (CReg dest_reg) src_amode
371 build_it_then return =
372 -- BUILD THE OBJECT IN THE HEAP
373 -- The first "con" says that the name bound to this
374 -- closure is "con", which is a bit of a fudge, but it only
377 -- This Id is also used to get a unique for a
378 -- temporary variable, if the closure is a CHARLIKE.
379 -- funnily enough, this makes the unique always come
381 buildDynCon (dataConId con) currentCCS con amodes `thenFC` \ idinfo ->
382 idInfoToAmode PtrRep idinfo `thenFC` \ amode ->
386 profCtrC SLIT("TICK_RET_NEW") [mkIntCLit (length amodes)] `thenC`
387 -- could use doTailCall here.
388 performReturn (move_to_reg amode node) return