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,
25 bindArgsToRegs, newTempAmodeAndIdInfo,
26 idInfoToAmode, stableAmodeIdInfo,
27 heapIdInfo, CgIdInfo, bindNewToStack
29 import CgStackery ( mkTaggedVirtStkOffsets, freeStackSlots,
32 import CgUsages ( getRealSp, getVirtSp, setRealAndVirtualSp,
34 import CgClosure ( cgTopRhsClosure )
35 import CgRetConv ( assignRegs )
36 import Constants ( mAX_INTLIKE, mIN_INTLIKE, mIN_UPD_SIZE )
37 import CgHeapery ( allocDynClosure, inPlaceAllocDynClosure )
38 import CgTailCall ( performReturn, mkStaticAlgReturnCode, doTailCall,
39 mkUnboxedTupleReturnCode )
40 import CLabel ( mkClosureLabel )
41 import ClosureInfo ( mkClosureLFInfo, mkConLFInfo, mkLFArgument,
42 layOutDynCon, layOutDynClosure,
43 layOutStaticClosure, closureSize
45 import CostCentre ( currentOrSubsumedCCS, dontCareCCS, CostCentreStack,
47 import DataCon ( DataCon, dataConName, dataConTag, dataConTyCon,
48 isUnboxedTupleCon, isNullaryDataCon, dataConId, dataConWrapId
50 import Id ( Id, idName, idType, idPrimRep )
51 import Name ( nameModule, isLocallyDefinedName )
52 import Literal ( Literal(..) )
53 import PrelInfo ( maybeCharLikeCon, maybeIntLikeCon )
54 import PrimRep ( PrimRep(..), isFollowableRep )
55 import Unique ( Uniquable(..) )
57 import Panic ( assertPanic, trace )
60 %************************************************************************
62 \subsection[toplevel-constructors]{Top-level constructors}
64 %************************************************************************
67 cgTopRhsCon :: Id -- Name of thing bound to this RHS
70 -> FCode (Id, CgIdInfo)
71 cgTopRhsCon id con args
72 = ASSERT(not dynamic_con_or_args) -- checks for litlit args too
75 getArgAmodes args `thenFC` \ amodes ->
78 (closure_info, amodes_w_offsets)
79 = layOutStaticClosure name getAmodeRep amodes lf_info
84 closure_label -- Labelled with the name on lhs of defn
85 closure_info -- Closure is static
87 (map fst amodes_w_offsets)) -- Sorted into ptrs first, then nonptrs
92 returnFC (id, stableAmodeIdInfo id (CLbl closure_label PtrRep) lf_info)
94 lf_info = mkConLFInfo con
95 closure_label = mkClosureLabel name
98 top_ccc = mkCCostCentreStack dontCareCCS -- because it's static data
100 -- stuff needed by the assert pred only.
101 dynamic_con_or_args = isDllConApp con args
104 %************************************************************************
106 %* non-top-level constructors *
108 %************************************************************************
109 \subsection[code-for-constructors]{The code for constructors}
112 buildDynCon :: Id -- Name of the thing to which this constr will
114 -> CostCentreStack -- Where to grab cost centre from;
115 -- current CCS if currentOrSubsumedCCS
116 -> DataCon -- The data constructor
117 -> [CAddrMode] -- Its args
118 -> FCode CgIdInfo -- Return details about how to find it
120 -- We used to pass a boolean indicating whether all the
121 -- args were of size zero, so we could use a static
122 -- construtor; but I concluded that it just isn't worth it.
123 -- Now I/O uses unboxed tuples there just aren't any constructors
124 -- with all size-zero args.
126 -- The reason for having a separate argument, rather than looking at
127 -- the addr modes of the args is that we may be in a "knot", and
128 -- premature looking at the args will cause the compiler to black-hole!
131 First we deal with the case of zero-arity constructors. Now, they
132 will probably be unfolded, so we don't expect to see this case much,
133 if at all, but it does no harm, and sets the scene for characters.
135 In the case of zero-arity constructors, or, more accurately, those
136 which have exclusively size-zero (VoidRep) args, we generate no code
140 buildDynCon binder cc con []
141 = returnFC (stableAmodeIdInfo binder
142 (CLbl (mkClosureLabel (idName (dataConWrapId con))) PtrRep)
146 Now for @Char@-like closures. We generate an assignment of the
147 address of the closure to a temporary. It would be possible simply to
148 generate no code, and record the addressing mode in the environment,
149 but we'd have to be careful if the argument wasn't a constant --- so
150 for simplicity we just always asssign to a temporary.
152 Last special case: @Int@-like closures. We only special-case the
153 situation in which the argument is a literal in the range
154 @mIN_INTLIKE@..@mAX_INTLILKE@. NB: for @Char@-like closures we can
155 work with any old argument, but for @Int@-like ones the argument has
156 to be a literal. Reason: @Char@ like closures have an argument type
157 which is guaranteed in range.
159 Because of this, we use can safely return an addressing mode.
162 buildDynCon binder cc con [arg_amode]
164 | maybeCharLikeCon con
165 = absC (CAssign temp_amode (CCharLike arg_amode)) `thenC`
166 returnFC temp_id_info
168 | maybeIntLikeCon con && in_range_int_lit arg_amode
169 = returnFC (stableAmodeIdInfo binder (CIntLike arg_amode) (mkConLFInfo con))
171 (temp_amode, temp_id_info) = newTempAmodeAndIdInfo binder (mkConLFInfo con)
173 in_range_int_lit (CLit (MachInt val)) = val <= mAX_INTLIKE && val >= mIN_INTLIKE
174 in_range_int_lit other_amode = False
177 Now the general case.
180 buildDynCon binder ccs con args
181 = allocDynClosure closure_info use_cc blame_cc amodes_w_offsets `thenFC` \ hp_off ->
182 returnFC (heapIdInfo binder hp_off lf_info)
184 (closure_info, amodes_w_offsets)
185 = layOutDynClosure (idName binder) getAmodeRep args lf_info
186 lf_info = mkConLFInfo con
188 use_cc -- cost-centre to stick in the object
189 = if currentOrSubsumedCCS ccs
190 then CReg CurCostCentre
191 else mkCCostCentreStack ccs
193 blame_cc = use_cc -- cost-centre on which to blame the alloc (same)
197 %************************************************************************
199 %* constructor-related utility function: *
200 %* bindConArgs is called from cgAlt of a case *
202 %************************************************************************
203 \subsection[constructor-utilities]{@bindConArgs@: constructor-related utility}
205 @bindConArgs@ $con args$ augments the environment with bindings for the
206 binders $args$, assuming that we have just returned from a @case@ which
211 :: DataCon -> [Id] -- Constructor and args
215 = ASSERT(not (isUnboxedTupleCon con))
216 mapCs bind_arg args_w_offsets
218 bind_arg (arg, offset) = bindNewToNode arg offset mkLFArgument
219 (_, args_w_offsets) = layOutDynCon con idPrimRep args
222 Unboxed tuples are handled slightly differently - the object is
223 returned in registers and on the stack instead of the heap.
226 bindUnboxedTupleComponents
228 -> FCode ([MagicId], -- regs assigned
229 [(VirtualSpOffset,Int)], -- tag slots
230 Bool) -- any components on stack?
232 bindUnboxedTupleComponents args
233 = -- Assign as many components as possible to registers
234 let (arg_regs, leftovers) = assignRegs [] (map idPrimRep args)
235 (reg_args, stk_args) = splitAt (length arg_regs) args
238 -- Allocate the rest on the stack (ToDo: separate out pointers)
239 getVirtSp `thenFC` \ vsp ->
240 getRealSp `thenFC` \ rsp ->
241 let (top_sp, stk_offsets, tags) =
242 mkTaggedVirtStkOffsets rsp idPrimRep stk_args
245 -- The stack pointer points to the last stack-allocated component
246 setRealAndVirtualSp top_sp `thenC`
248 -- need to explicitly free any empty slots we just jumped over
249 (if vsp < rsp then freeStackSlots [vsp+1 .. rsp] else nopC) `thenC`
251 bindArgsToRegs reg_args arg_regs `thenC`
252 mapCs bindNewToStack stk_offsets `thenC`
253 returnFC (arg_regs,tags, not (null stk_offsets))
256 %************************************************************************
258 \subsubsection[CgRetConv-cgReturnDataCon]{Actually generate code for a constructor return}
260 %************************************************************************
263 Note: it's the responsibility of the @cgReturnDataCon@ caller to be
264 sure the @amodes@ passed don't conflict with each other.
266 cgReturnDataCon :: DataCon -> [CAddrMode] -> Code
268 cgReturnDataCon con amodes
269 = getEndOfBlockInfo `thenFC` \ (EndOfBlockInfo args_sp sequel) ->
273 CaseAlts _ (Just (alts, Just (maybe_deflt, (_,deflt_lbl))))
274 | not (dataConTag con `is_elem` map fst alts)
276 -- Special case! We're returning a constructor to the default case
277 -- of an enclosing case. For example:
279 -- case (case e of (a,b) -> C a b) of
281 -- y -> ...<returning here!>...
284 -- if the default is a non-bind-default (ie does not use y),
285 -- then we should simply jump to the default join point;
288 Nothing -> performReturn AbsCNop {- No reg assts -} jump_to_join_point
289 Just _ -> build_it_then jump_to_join_point
291 is_elem = isIn "cgReturnDataCon"
292 jump_to_join_point sequel = absC (CJump (CLbl deflt_lbl CodePtrRep))
293 -- Ignore the sequel: we've already looked at it above
295 -- If the sequel is an update frame, we might be able to
296 -- do update in place...
298 | not (isNullaryDataCon con) -- no nullary constructors, please
299 && not (maybeCharLikeCon con) -- no chars please (these are all static)
300 && not (any isFollowableRep (map getAmodeRep amodes))
301 -- no ptrs please (generational gc...)
302 && closureSize closure_info <= mIN_UPD_SIZE
303 -- don't know the real size of the
304 -- thunk, so assume mIN_UPD_SIZE
306 -> -- get a new temporary and make it point to the updatee
309 temp = CTemp uniq PtrRep
312 profCtrC SLIT("TICK_UPD_CON_IN_PLACE")
313 [mkIntCLit (length amodes)] `thenC`
315 getSpRelOffset args_sp `thenFC` \ sp_rel ->
317 (CMacroExpr PtrRep UPD_FRAME_UPDATEE [CAddr sp_rel]))
320 -- stomp all over it with the new constructor
321 inPlaceAllocDynClosure closure_info temp (CReg CurCostCentre) stuff
324 -- don't forget to update Su from the update frame
325 absC (CMacroStmt UPDATE_SU_FROM_UPD_FRAME [CAddr sp_rel]) `thenC`
327 -- set Node to point to the closure being returned
328 -- (can't be done earlier: node might conflict with amodes)
329 absC (CAssign (CReg node) temp) `thenC`
331 -- pop the update frame off the stack, and do the proper
333 let new_sp = args_sp - updateFrameSize in
334 setEndOfBlockInfo (EndOfBlockInfo new_sp (OnStack new_sp)) $
335 performReturn (AbsCNop) (mkStaticAlgReturnCode con)
337 where (closure_info, stuff)
338 = layOutDynClosure (dataConName con)
339 getAmodeRep amodes lf_info
341 lf_info = mkConLFInfo con
343 other_sequel -- The usual case
345 | isUnboxedTupleCon con ->
346 -- Return unboxed tuple in registers
347 let (ret_regs, leftovers) =
348 assignRegs [] (map getAmodeRep amodes)
350 profCtrC SLIT("TICK_RET_UNBOXED_TUP")
351 [mkIntCLit (length amodes)] `thenC`
353 doTailCall amodes ret_regs
354 mkUnboxedTupleReturnCode
355 (length leftovers) {- fast args arity -}
356 AbsCNop {-no pending assigments-}
357 Nothing {-not a let-no-escape-}
358 False {-node doesn't point-}
361 build_it_then (mkStaticAlgReturnCode con)
364 move_to_reg :: CAddrMode -> MagicId -> AbstractC
365 move_to_reg src_amode dest_reg = CAssign (CReg dest_reg) src_amode
367 build_it_then return =
368 -- BUILD THE OBJECT IN THE HEAP
369 -- The first "con" says that the name bound to this
370 -- closure is "con", which is a bit of a fudge, but it only
373 -- This Id is also used to get a unique for a
374 -- temporary variable, if the closure is a CHARLIKE.
375 -- funnily enough, this makes the unique always come
377 buildDynCon (dataConId con) currentCCS con amodes `thenFC` \ idinfo ->
378 idInfoToAmode PtrRep idinfo `thenFC` \ amode ->
382 profCtrC SLIT("TICK_RET_NEW") [mkIntCLit (length amodes)] `thenC`
383 -- could use doTailCall here.
384 performReturn (move_to_reg amode node) return