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 ( mkVirtStkOffsets, freeStackSlots, updateFrameSize )
30 import CgUsages ( getRealSp, getVirtSp, setRealAndVirtualSp,
32 import CgRetConv ( assignRegs )
33 import Constants ( mAX_INTLIKE, mIN_INTLIKE, mAX_CHARLIKE, mIN_CHARLIKE,
35 import CgHeapery ( allocDynClosure )
36 import CgTailCall ( performReturn, mkStaticAlgReturnCode,
38 import CLabel ( mkClosureLabel )
39 import ClosureInfo ( mkConLFInfo, mkLFArgument, layOutDynConstr,
40 layOutStaticConstr, closureSize, mkStaticClosure
42 import CostCentre ( currentOrSubsumedCCS, dontCareCCS, CostCentreStack,
44 import DataCon ( DataCon, dataConTag,
45 isUnboxedTupleCon, isNullaryDataCon, dataConWorkId,
46 dataConName, dataConRepArity
48 import Id ( Id, idName, idPrimRep, isDeadBinder )
49 import Literal ( Literal(..) )
50 import PrelInfo ( maybeCharLikeCon, maybeIntLikeCon )
51 import PrimRep ( PrimRep(..), isFollowableRep )
52 import Unique ( Uniquable(..) )
56 import List ( partition )
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
72 ASSERT( args `lengthIs` dataConRepArity con )
75 getArgAmodes args `thenFC` \ amodes ->
79 lf_info = mkConLFInfo con
80 closure_label = mkClosureLabel name
81 (closure_info, amodes_w_offsets)
82 = layOutStaticConstr con getAmodeRep amodes
83 caffy = any stgArgHasCafRefs args
90 dontCareCCS -- because it's static data
91 (map fst amodes_w_offsets) -- Sorted into ptrs first, then nonptrs
94 -- NOTE: can't use idCafInfo instead of nonEmptySRT above,
95 -- because top-level constructors that were floated by
96 -- CorePrep don't have CafInfo attached. The SRT is more
100 returnFC (id, stableAmodeIdInfo id (CLbl closure_label PtrRep) lf_info)
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 (dataConName 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 lf_info = mkConLFInfo con
191 (closure_info, amodes_w_offsets) = layOutDynConstr con getAmodeRep args
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 arg)
224 (_, args_w_offsets) = layOutDynConstr 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 Int, -- Number of pointer stack slots
235 Int, -- Number of non-pointer stack slots
236 VirtualSpOffset) -- Offset of return address slot
237 -- (= realSP on entry)
239 bindUnboxedTupleComponents args
240 = -- Assign as many components as possible to registers
241 let (arg_regs, _leftovers) = assignRegs [] (map idPrimRep args)
242 (reg_args, stk_args) = splitAtList arg_regs args
244 -- separate the rest of the args into pointers and non-pointers
245 (ptr_args, nptr_args) =
246 partition (isFollowableRep . idPrimRep) stk_args
249 -- Allocate the rest on the stack
250 -- The real SP points to the return address, above which any
251 -- leftover unboxed-tuple components will be allocated
252 getVirtSp `thenFC` \ vsp ->
253 getRealSp `thenFC` \ rsp ->
255 (ptr_sp, ptr_offsets) = mkVirtStkOffsets rsp idPrimRep ptr_args
256 (nptr_sp, nptr_offsets) = mkVirtStkOffsets ptr_sp idPrimRep nptr_args
258 nptrs = nptr_sp - ptr_sp
261 -- The stack pointer points to the last stack-allocated component
262 setRealAndVirtualSp nptr_sp `thenC`
264 -- We have just allocated slots starting at real SP + 1, and set the new
265 -- virtual SP to the topmost allocated slot.
266 -- If the virtual SP started *below* the real SP, we've just jumped over
267 -- some slots that won't be in the free-list, so put them there
268 -- This commonly happens because we've freed the return-address slot
269 -- (trimming back the virtual SP), but the real SP still points to that slot
270 freeStackSlots [vsp+1,vsp+2 .. rsp] `thenC`
272 bindArgsToRegs reg_args arg_regs `thenC`
273 mapCs bindNewToStack ptr_offsets `thenC`
274 mapCs bindNewToStack nptr_offsets `thenC`
276 returnFC (arg_regs, ptrs, nptrs, rsp)
279 %************************************************************************
281 \subsubsection[CgRetConv-cgReturnDataCon]{Actually generate code for a constructor return}
283 %************************************************************************
286 Note: it's the responsibility of the @cgReturnDataCon@ caller to be
287 sure the @amodes@ passed don't conflict with each other.
289 cgReturnDataCon :: DataCon -> [CAddrMode] -> Code
291 cgReturnDataCon con amodes
292 = ASSERT( amodes `lengthIs` dataConRepArity con )
293 getEndOfBlockInfo `thenFC` \ (EndOfBlockInfo args_sp sequel) ->
297 CaseAlts _ (Just (alts, Just (deflt_bndr, (_,deflt_lbl)))) False
298 | not (dataConTag con `is_elem` map fst alts)
300 -- Special case! We're returning a constructor to the default case
301 -- of an enclosing case. For example:
303 -- case (case e of (a,b) -> C a b) of
305 -- y -> ...<returning here!>...
308 -- if the default is a non-bind-default (ie does not use y),
309 -- then we should simply jump to the default join point;
311 if isDeadBinder deflt_bndr
312 then performReturn AbsCNop {- No reg assts -} jump_to_join_point
313 else build_it_then jump_to_join_point
315 is_elem = isIn "cgReturnDataCon"
316 jump_to_join_point sequel = absC (CJump (CLbl deflt_lbl CodePtrRep))
317 -- Ignore the sequel: we've already looked at it above
319 other_sequel -- The usual case
320 | isUnboxedTupleCon con -> returnUnboxedTuple amodes
321 | otherwise -> build_it_then (mkStaticAlgReturnCode con)
324 move_to_reg :: CAddrMode -> MagicId -> AbstractC
325 move_to_reg src_amode dest_reg = CAssign (CReg dest_reg) src_amode
327 build_it_then return =
328 -- BUILD THE OBJECT IN THE HEAP
329 -- The first "con" says that the name bound to this
330 -- closure is "con", which is a bit of a fudge, but it only
333 -- This Id is also used to get a unique for a
334 -- temporary variable, if the closure is a CHARLIKE.
335 -- funnily enough, this makes the unique always come
337 buildDynCon (dataConWorkId con) currentCCS con amodes `thenFC` \ idinfo ->
338 idInfoToAmode PtrRep idinfo `thenFC` \ amode ->
342 profCtrC FSLIT("TICK_RET_NEW") [mkIntCLit (length amodes)] `thenC`
343 -- could use doTailCall here.
344 performReturn (move_to_reg amode node) return