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 (isDllConApp con args)) -- checks for litlit args too
74 closure_label = mkClosureLabel name
75 lf_info = mkConLFInfo con
76 cg_id_info = stableAmodeIdInfo id (CLbl closure_label PtrRep) lf_info
81 getArgAmodes args `thenFC` \ amodes ->
84 (closure_info, amodes_w_offsets)
85 = layOutStaticClosure name getAmodeRep amodes lf_info
90 closure_label -- Labelled with the name on lhs of defn
91 closure_info -- Closure is static
92 (mkCCostCentreStack dontCareCCS) -- because it's static data
93 (map fst amodes_w_offsets)) -- Sorted into ptrs first, then nonptrs
98 returnFC (id, stableAmodeIdInfo id (CLbl closure_label PtrRep) lf_info)
101 %************************************************************************
103 %* non-top-level constructors *
105 %************************************************************************
106 \subsection[code-for-constructors]{The code for constructors}
109 buildDynCon :: Id -- Name of the thing to which this constr will
111 -> CostCentreStack -- Where to grab cost centre from;
112 -- current CCS if currentOrSubsumedCCS
113 -> DataCon -- The data constructor
114 -> [CAddrMode] -- Its args
115 -> FCode CgIdInfo -- Return details about how to find it
117 -- We used to pass a boolean indicating whether all the
118 -- args were of size zero, so we could use a static
119 -- construtor; but I concluded that it just isn't worth it.
120 -- Now I/O uses unboxed tuples there just aren't any constructors
121 -- with all size-zero args.
123 -- The reason for having a separate argument, rather than looking at
124 -- the addr modes of the args is that we may be in a "knot", and
125 -- premature looking at the args will cause the compiler to black-hole!
128 First we deal with the case of zero-arity constructors. Now, they
129 will probably be unfolded, so we don't expect to see this case much,
130 if at all, but it does no harm, and sets the scene for characters.
132 In the case of zero-arity constructors, or, more accurately, those
133 which have exclusively size-zero (VoidRep) args, we generate no code
137 buildDynCon binder cc con []
138 = returnFC (stableAmodeIdInfo binder
139 (CLbl (mkClosureLabel (idName (dataConWrapId con))) PtrRep)
143 The following three paragraphs about @Char@-like and @Int@-like
144 closures are obsolete, but I don't understand the details well enough
145 to properly word them, sorry. I've changed the treatment of @Char@s to
146 be analogous to @Int@s: only a subset is preallocated, because @Char@
147 has now 31 bits. Only literals are handled here. -- Qrczak
149 Now for @Char@-like closures. We generate an assignment of the
150 address of the closure to a temporary. It would be possible simply to
151 generate no code, and record the addressing mode in the environment,
152 but we'd have to be careful if the argument wasn't a constant --- so
153 for simplicity we just always asssign to a temporary.
155 Last special case: @Int@-like closures. We only special-case the
156 situation in which the argument is a literal in the range
157 @mIN_INTLIKE@..@mAX_INTLILKE@. NB: for @Char@-like closures we can
158 work with any old argument, but for @Int@-like ones the argument has
159 to be a literal. Reason: @Char@ like closures have an argument type
160 which is guaranteed in range.
162 Because of this, we use can safely return an addressing mode.
165 buildDynCon binder cc con [arg_amode]
166 | maybeIntLikeCon con && in_range_int_lit arg_amode
167 = returnFC (stableAmodeIdInfo binder (CIntLike arg_amode) (mkConLFInfo con))
169 in_range_int_lit (CLit (MachInt val)) = val <= mAX_INTLIKE && val >= mIN_INTLIKE
170 in_range_int_lit _other_amode = False
172 buildDynCon binder cc con [arg_amode]
173 | maybeCharLikeCon con && in_range_char_lit arg_amode
174 = returnFC (stableAmodeIdInfo binder (CCharLike arg_amode) (mkConLFInfo con))
176 in_range_char_lit (CLit (MachChar val)) = val <= mAX_CHARLIKE && val >= mIN_CHARLIKE
177 in_range_char_lit _other_amode = False
180 Now the general case.
183 buildDynCon binder ccs con args
184 = allocDynClosure closure_info use_cc blame_cc amodes_w_offsets `thenFC` \ hp_off ->
185 returnFC (heapIdInfo binder hp_off lf_info)
187 (closure_info, amodes_w_offsets)
188 = layOutDynClosure (idName binder) getAmodeRep args lf_info
189 lf_info = mkConLFInfo con
191 use_cc -- cost-centre to stick in the object
192 = if currentOrSubsumedCCS ccs
193 then CReg CurCostCentre
194 else mkCCostCentreStack ccs
196 blame_cc = use_cc -- cost-centre on which to blame the alloc (same)
200 %************************************************************************
202 %* constructor-related utility function: *
203 %* bindConArgs is called from cgAlt of a case *
205 %************************************************************************
206 \subsection[constructor-utilities]{@bindConArgs@: constructor-related utility}
208 @bindConArgs@ $con args$ augments the environment with bindings for the
209 binders $args$, assuming that we have just returned from a @case@ which
214 :: DataCon -> [Id] -- Constructor and args
218 = ASSERT(not (isUnboxedTupleCon con))
219 mapCs bind_arg args_w_offsets
221 bind_arg (arg, offset) = bindNewToNode arg offset mkLFArgument
222 (_, args_w_offsets) = layOutDynCon con idPrimRep args
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) = splitAt (length 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 = getEndOfBlockInfo `thenFC` \ (EndOfBlockInfo args_sp sequel) ->
276 CaseAlts _ (Just (alts, Just (maybe_deflt, (_,deflt_lbl))))
277 | not (dataConTag con `is_elem` map fst alts)
279 -- Special case! We're returning a constructor to the default case
280 -- of an enclosing case. For example:
282 -- case (case e of (a,b) -> C a b) of
284 -- y -> ...<returning here!>...
287 -- if the default is a non-bind-default (ie does not use y),
288 -- then we should simply jump to the default join point;
291 Nothing -> performReturn AbsCNop {- No reg assts -} jump_to_join_point
292 Just _ -> build_it_then jump_to_join_point
294 is_elem = isIn "cgReturnDataCon"
295 jump_to_join_point sequel = absC (CJump (CLbl deflt_lbl CodePtrRep))
296 -- Ignore the sequel: we've already looked at it above
298 -- If the sequel is an update frame, we might be able to
299 -- do update in place...
301 | not (isNullaryDataCon con) -- no nullary constructors, please
302 && not (any isFollowableRep (map getAmodeRep amodes))
303 -- no ptrs please (generational gc...)
304 && closureSize closure_info <= mIN_UPD_SIZE
305 -- don't know the real size of the
306 -- thunk, so assume mIN_UPD_SIZE
308 -> -- get a new temporary and make it point to the updatee
311 temp = CTemp uniq PtrRep
314 profCtrC SLIT("TICK_UPD_CON_IN_PLACE")
315 [mkIntCLit (length amodes)] `thenC`
317 getSpRelOffset args_sp `thenFC` \ sp_rel ->
319 (CMacroExpr PtrRep UPD_FRAME_UPDATEE [CAddr sp_rel]))
322 -- stomp all over it with the new constructor
323 inPlaceAllocDynClosure closure_info temp (CReg CurCostCentre) stuff
326 -- don't forget to update Su from the update frame
327 absC (CMacroStmt UPDATE_SU_FROM_UPD_FRAME [CAddr sp_rel]) `thenC`
329 -- set Node to point to the closure being returned
330 -- (can't be done earlier: node might conflict with amodes)
331 absC (CAssign (CReg node) temp) `thenC`
333 -- pop the update frame off the stack, and do the proper
335 let new_sp = args_sp - updateFrameSize in
336 setEndOfBlockInfo (EndOfBlockInfo new_sp (OnStack new_sp)) $
337 performReturn (AbsCNop) (mkStaticAlgReturnCode con)
339 where (closure_info, stuff)
340 = layOutDynClosure (dataConName con)
341 getAmodeRep amodes lf_info
343 lf_info = mkConLFInfo con
345 other_sequel -- The usual case
347 | isUnboxedTupleCon con ->
348 -- Return unboxed tuple in registers
349 let (ret_regs, leftovers) =
350 assignRegs [] (map getAmodeRep amodes)
352 profCtrC SLIT("TICK_RET_UNBOXED_TUP")
353 [mkIntCLit (length amodes)] `thenC`
355 doTailCall amodes ret_regs
356 mkUnboxedTupleReturnCode
357 (length leftovers) {- fast args arity -}
358 AbsCNop {-no pending assigments-}
359 Nothing {-not a let-no-escape-}
360 False {-node doesn't point-}
363 build_it_then (mkStaticAlgReturnCode con)
366 move_to_reg :: CAddrMode -> MagicId -> AbstractC
367 move_to_reg src_amode dest_reg = CAssign (CReg dest_reg) src_amode
369 build_it_then return =
370 -- BUILD THE OBJECT IN THE HEAP
371 -- The first "con" says that the name bound to this
372 -- closure is "con", which is a bit of a fudge, but it only
375 -- This Id is also used to get a unique for a
376 -- temporary variable, if the closure is a CHARLIKE.
377 -- funnily enough, this makes the unique always come
379 buildDynCon (dataConId con) currentCCS con amodes `thenFC` \ idinfo ->
380 idInfoToAmode PtrRep idinfo `thenFC` \ amode ->
384 profCtrC SLIT("TICK_RET_NEW") [mkIntCLit (length amodes)] `thenC`
385 -- could use doTailCall here.
386 performReturn (move_to_reg amode node) return