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, closureLFInfo,
42 layOutDynConstr, layOutDynClosure,
43 layOutStaticConstr, closureSize, mkStaticClosure
45 import CostCentre ( currentOrSubsumedCCS, dontCareCCS, CostCentreStack,
47 import DataCon ( DataCon, dataConName, dataConTag,
48 isUnboxedTupleCon, isNullaryDataCon, dataConId,
49 dataConWrapId, dataConRepArity
51 import Id ( Id, idName, idPrimRep, idCafInfo )
52 import IdInfo ( mayHaveCafRefs )
53 import Literal ( Literal(..) )
54 import PrelInfo ( maybeCharLikeCon, maybeIntLikeCon )
55 import PrimRep ( PrimRep(..), isFollowableRep )
56 import Unique ( Uniquable(..) )
61 %************************************************************************
63 \subsection[toplevel-constructors]{Top-level constructors}
65 %************************************************************************
68 cgTopRhsCon :: Id -- Name of thing bound to this RHS
71 -> FCode (Id, CgIdInfo)
72 cgTopRhsCon id con args
73 = ASSERT( not (isDllConApp con args) ) -- checks for litlit args too
74 ASSERT( args `lengthIs` dataConRepArity con )
77 getArgAmodes args `thenFC` \ amodes ->
81 lf_info = closureLFInfo closure_info
82 closure_label = mkClosureLabel name
83 (closure_info, amodes_w_offsets)
84 = layOutStaticConstr name con getAmodeRep amodes
90 dontCareCCS -- because it's static data
91 (map fst amodes_w_offsets) -- Sorted into ptrs first, then nonptrs
92 (mayHaveCafRefs (idCafInfo id))
96 returnFC (id, stableAmodeIdInfo id (CLbl closure_label PtrRep) lf_info)
99 %************************************************************************
101 %* non-top-level constructors *
103 %************************************************************************
104 \subsection[code-for-constructors]{The code for constructors}
107 buildDynCon :: Id -- Name of the thing to which this constr will
109 -> CostCentreStack -- Where to grab cost centre from;
110 -- current CCS if currentOrSubsumedCCS
111 -> DataCon -- The data constructor
112 -> [CAddrMode] -- Its args
113 -> FCode CgIdInfo -- Return details about how to find it
115 -- We used to pass a boolean indicating whether all the
116 -- args were of size zero, so we could use a static
117 -- construtor; but I concluded that it just isn't worth it.
118 -- Now I/O uses unboxed tuples there just aren't any constructors
119 -- with all size-zero args.
121 -- The reason for having a separate argument, rather than looking at
122 -- the addr modes of the args is that we may be in a "knot", and
123 -- premature looking at the args will cause the compiler to black-hole!
126 First we deal with the case of zero-arity constructors. Now, they
127 will probably be unfolded, so we don't expect to see this case much,
128 if at all, but it does no harm, and sets the scene for characters.
130 In the case of zero-arity constructors, or, more accurately, those
131 which have exclusively size-zero (VoidRep) args, we generate no code
135 buildDynCon binder cc con []
136 = returnFC (stableAmodeIdInfo binder
137 (CLbl (mkClosureLabel (idName (dataConWrapId con))) PtrRep)
141 The following three paragraphs about @Char@-like and @Int@-like
142 closures are obsolete, but I don't understand the details well enough
143 to properly word them, sorry. I've changed the treatment of @Char@s to
144 be analogous to @Int@s: only a subset is preallocated, because @Char@
145 has now 31 bits. Only literals are handled here. -- Qrczak
147 Now for @Char@-like closures. We generate an assignment of the
148 address of the closure to a temporary. It would be possible simply to
149 generate no code, and record the addressing mode in the environment,
150 but we'd have to be careful if the argument wasn't a constant --- so
151 for simplicity we just always asssign to a temporary.
153 Last special case: @Int@-like closures. We only special-case the
154 situation in which the argument is a literal in the range
155 @mIN_INTLIKE@..@mAX_INTLILKE@. NB: for @Char@-like closures we can
156 work with any old argument, but for @Int@-like ones the argument has
157 to be a literal. Reason: @Char@ like closures have an argument type
158 which is guaranteed in range.
160 Because of this, we use can safely return an addressing mode.
163 buildDynCon binder cc con [arg_amode]
164 | maybeIntLikeCon con && in_range_int_lit arg_amode
165 = returnFC (stableAmodeIdInfo binder (CIntLike arg_amode) (mkConLFInfo con))
167 in_range_int_lit (CLit (MachInt val)) = val <= mAX_INTLIKE && val >= mIN_INTLIKE
168 in_range_int_lit _other_amode = False
170 buildDynCon binder cc con [arg_amode]
171 | maybeCharLikeCon con && in_range_char_lit arg_amode
172 = returnFC (stableAmodeIdInfo binder (CCharLike arg_amode) (mkConLFInfo con))
174 in_range_char_lit (CLit (MachChar val)) = val <= mAX_CHARLIKE && val >= mIN_CHARLIKE
175 in_range_char_lit _other_amode = False
178 Now the general case.
181 buildDynCon binder ccs con args
182 = allocDynClosure closure_info use_cc blame_cc amodes_w_offsets `thenFC` \ hp_off ->
183 returnFC (heapIdInfo binder hp_off lf_info)
185 (closure_info, amodes_w_offsets)
186 = layOutDynClosure (idName binder) getAmodeRep args lf_info NoC_SRT
187 lf_info = mkConLFInfo con
189 use_cc -- cost-centre to stick in the object
190 = if currentOrSubsumedCCS ccs
191 then CReg CurCostCentre
192 else mkCCostCentreStack ccs
194 blame_cc = use_cc -- cost-centre on which to blame the alloc (same)
198 %************************************************************************
200 %* constructor-related utility function: *
201 %* bindConArgs is called from cgAlt of a case *
203 %************************************************************************
204 \subsection[constructor-utilities]{@bindConArgs@: constructor-related utility}
206 @bindConArgs@ $con args$ augments the environment with bindings for the
207 binders $args$, assuming that we have just returned from a @case@ which
212 :: DataCon -> [Id] -- Constructor and args
216 = ASSERT(not (isUnboxedTupleCon con))
217 mapCs bind_arg args_w_offsets
219 bind_arg (arg, offset) = bindNewToNode arg offset mkLFArgument
220 (_, args_w_offsets) = layOutDynConstr bogus_name con idPrimRep args
222 bogus_name = panic "bindConArgs"
225 Unboxed tuples are handled slightly differently - the object is
226 returned in registers and on the stack instead of the heap.
229 bindUnboxedTupleComponents
231 -> FCode ([MagicId], -- regs assigned
232 [(VirtualSpOffset,Int)], -- tag slots
233 Bool) -- any components on stack?
235 bindUnboxedTupleComponents args
236 = -- Assign as many components as possible to registers
237 let (arg_regs, _leftovers) = assignRegs [] (map idPrimRep args)
238 (reg_args, stk_args) = splitAtList arg_regs args
241 -- Allocate the rest on the stack (ToDo: separate out pointers)
242 getVirtSp `thenFC` \ vsp ->
243 getRealSp `thenFC` \ rsp ->
244 let (top_sp, stk_offsets, tags) =
245 mkTaggedVirtStkOffsets rsp idPrimRep stk_args
248 -- The stack pointer points to the last stack-allocated component
249 setRealAndVirtualSp top_sp `thenC`
251 -- need to explicitly free any empty slots we just jumped over
252 (if vsp < rsp then freeStackSlots [vsp+1 .. rsp] else nopC) `thenC`
254 bindArgsToRegs reg_args arg_regs `thenC`
255 mapCs bindNewToStack stk_offsets `thenC`
256 returnFC (arg_regs,tags, not (null stk_offsets))
259 %************************************************************************
261 \subsubsection[CgRetConv-cgReturnDataCon]{Actually generate code for a constructor return}
263 %************************************************************************
266 Note: it's the responsibility of the @cgReturnDataCon@ caller to be
267 sure the @amodes@ passed don't conflict with each other.
269 cgReturnDataCon :: DataCon -> [CAddrMode] -> Code
271 cgReturnDataCon con amodes
272 = ASSERT( amodes `lengthIs` dataConRepArity con )
273 getEndOfBlockInfo `thenFC` \ (EndOfBlockInfo args_sp sequel) ->
277 CaseAlts _ (Just (alts, Just (maybe_deflt, (_,deflt_lbl))))
278 | not (dataConTag con `is_elem` map fst alts)
280 -- Special case! We're returning a constructor to the default case
281 -- of an enclosing case. For example:
283 -- case (case e of (a,b) -> C a b) of
285 -- y -> ...<returning here!>...
288 -- if the default is a non-bind-default (ie does not use y),
289 -- then we should simply jump to the default join point;
292 Nothing -> performReturn AbsCNop {- No reg assts -} jump_to_join_point
293 Just _ -> build_it_then jump_to_join_point
295 is_elem = isIn "cgReturnDataCon"
296 jump_to_join_point sequel = absC (CJump (CLbl deflt_lbl CodePtrRep))
297 -- Ignore the sequel: we've already looked at it above
299 -- If the sequel is an update frame, we might be able to
300 -- do update in place...
302 | not (isNullaryDataCon con) -- no nullary constructors, please
303 && not (any isFollowableRep (map getAmodeRep amodes))
304 -- no ptrs please (generational gc...)
305 && closureSize closure_info <= mIN_UPD_SIZE
306 -- don't know the real size of the
307 -- thunk, so assume mIN_UPD_SIZE
309 -> -- get a new temporary and make it point to the updatee
312 temp = CTemp uniq PtrRep
315 profCtrC SLIT("TICK_UPD_CON_IN_PLACE")
316 [mkIntCLit (length amodes)] `thenC`
318 getSpRelOffset args_sp `thenFC` \ sp_rel ->
320 (CMacroExpr PtrRep UPD_FRAME_UPDATEE [CAddr sp_rel]))
323 -- stomp all over it with the new constructor
324 inPlaceAllocDynClosure closure_info temp (CReg CurCostCentre) stuff
327 -- don't forget to update Su from the update frame
328 absC (CMacroStmt UPDATE_SU_FROM_UPD_FRAME [CAddr sp_rel]) `thenC`
330 -- set Node to point to the closure being returned
331 -- (can't be done earlier: node might conflict with amodes)
332 absC (CAssign (CReg node) temp) `thenC`
334 -- pop the update frame off the stack, and do the proper
336 let new_sp = args_sp - updateFrameSize in
337 setEndOfBlockInfo (EndOfBlockInfo new_sp (OnStack new_sp)) $
338 performReturn (AbsCNop) (mkStaticAlgReturnCode con)
341 (closure_info, stuff)
342 = layOutDynConstr (dataConName con) con getAmodeRep amodes
344 other_sequel -- The usual case
346 | isUnboxedTupleCon con ->
347 -- Return unboxed tuple in registers
348 let (ret_regs, leftovers) =
349 assignRegs [] (map getAmodeRep amodes)
351 profCtrC SLIT("TICK_RET_UNBOXED_TUP")
352 [mkIntCLit (length amodes)] `thenC`
354 doTailCall amodes ret_regs
355 mkUnboxedTupleReturnCode
356 (length leftovers) {- fast args arity -}
357 AbsCNop {-no pending assigments-}
358 Nothing {-not a let-no-escape-}
359 False {-node doesn't point-}
362 build_it_then (mkStaticAlgReturnCode con)
365 move_to_reg :: CAddrMode -> MagicId -> AbstractC
366 move_to_reg src_amode dest_reg = CAssign (CReg dest_reg) src_amode
368 build_it_then return =
369 -- BUILD THE OBJECT IN THE HEAP
370 -- The first "con" says that the name bound to this
371 -- closure is "con", which is a bit of a fudge, but it only
374 -- This Id is also used to get a unique for a
375 -- temporary variable, if the closure is a CHARLIKE.
376 -- funnily enough, this makes the unique always come
378 buildDynCon (dataConId con) currentCCS con amodes `thenFC` \ idinfo ->
379 idInfoToAmode PtrRep idinfo `thenFC` \ amode ->
383 profCtrC SLIT("TICK_RET_NEW") [mkIntCLit (length amodes)] `thenC`
384 -- could use doTailCall here.
385 performReturn (move_to_reg amode node) return