2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 % $Id: CgClosure.lhs,v 1.38 1999/11/11 17:50:49 simonpj Exp $
6 \section[CgClosure]{Code generation for closures}
8 This module provides the support code for @StgToAbstractC@ to deal
9 with {\em closures} on the RHSs of let(rec)s. See also
10 @CgCon@, which deals with constructors.
13 module CgClosure ( cgTopRhsClosure,
16 closureCodeBody ) where
18 #include "HsVersions.h"
20 import {-# SOURCE #-} CgExpr ( cgExpr )
26 import AbsCUtils ( mkAbstractCs, getAmodeRep )
27 import CgBindery ( getCAddrMode, getArgAmodes,
28 getCAddrModeAndInfo, bindNewToNode,
30 bindNewToReg, bindArgsToRegs,
31 stableAmodeIdInfo, heapIdInfo, CgIdInfo
33 import CgUpdate ( pushUpdateFrame )
34 import CgHeapery ( allocDynClosure,
35 fetchAndReschedule, yield, -- HWL
36 fastEntryChecks, thunkChecks
38 import CgStackery ( mkTaggedVirtStkOffsets, freeStackSlots )
39 import CgUsages ( adjustSpAndHp, setRealAndVirtualSp, getVirtSp,
40 getSpRelOffset, getHpRelOffset
42 import CLabel ( CLabel, mkClosureLabel, mkFastEntryLabel,
43 mkRednCountsLabel, mkInfoTableLabel
45 import ClosureInfo -- lots and lots of stuff
46 import CmdLineOpts ( opt_GranMacros, opt_SccProfilingOn, opt_DoTickyProfiling )
48 import Id ( Id, idName, idType, idPrimRep )
49 import Name ( Name, isLocalName )
50 import Module ( Module, pprModule )
51 import ListSetOps ( minusList )
52 import PrimRep ( PrimRep(..) )
53 import PprType ( showTypeCategory )
55 import CmdLineOpts ( opt_SccProfilingOn )
58 import Name ( nameOccName )
59 import OccName ( occNameFS )
61 getWrapperArgTypeCategories = panic "CgClosure.getWrapperArgTypeCategories (ToDo)"
64 %********************************************************
66 \subsection[closures-no-free-vars]{Top-level closures}
68 %********************************************************
70 For closures bound at top level, allocate in static space.
71 They should have no free variables.
75 -> CostCentreStack -- Optional cost centre annotation
80 -> FCode (Id, CgIdInfo)
82 cgTopRhsClosure id ccs binder_info args body lf_info
83 = -- LAY OUT THE OBJECT
85 closure_info = layOutStaticNoFVClosure name lf_info
88 -- BUILD THE OBJECT (IF NECESSARY)
89 ({- if staticClosureRequired name binder_info lf_info
91 (if opt_SccProfilingOn
94 closure_label -- Labelled with the name on lhs of defn
96 (mkCCostCentreStack ccs)
100 closure_label -- Labelled with the name on lhs of defn
110 -- GENERATE THE INFO TABLE (IF NECESSARY)
111 forkClosureBody (closureCodeBody binder_info closure_info
116 returnFC (id, cg_id_info)
119 closure_label = mkClosureLabel name
120 cg_id_info = stableAmodeIdInfo id (CLbl closure_label PtrRep) lf_info
123 %********************************************************
125 \subsection[non-top-level-closures]{Non top-level closures}
127 %********************************************************
129 For closures with free vars, allocate in heap.
134 -> CostCentreStack -- Optional cost centre annotation
140 -> [StgArg] -- payload
141 -> FCode (Id, CgIdInfo)
143 cgStdRhsClosure binder cc binder_info fvs args body lf_info payload
144 -- AHA! A STANDARD-FORM THUNK
146 -- LAY OUT THE OBJECT
147 getArgAmodes payload `thenFC` \ amodes ->
149 (closure_info, amodes_w_offsets)
150 = layOutDynClosure (idName binder) getAmodeRep amodes lf_info
152 (use_cc, blame_cc) = chooseDynCostCentres cc args fvs body
155 allocDynClosure closure_info use_cc blame_cc amodes_w_offsets
157 `thenFC` \ heap_offset ->
160 returnFC (binder, heapIdInfo binder heap_offset lf_info)
163 is_std_thunk = isStandardFormThunk lf_info
166 Here's the general case.
170 -> CostCentreStack -- Optional cost centre annotation
176 -> FCode (Id, CgIdInfo)
178 cgRhsClosure binder cc binder_info fvs args body lf_info
180 -- LAY OUT THE OBJECT
182 -- If the binder is itself a free variable, then don't store
183 -- it in the closure. Instead, just bind it to Node on entry.
184 -- NB we can be sure that Node will point to it, because we
185 -- havn't told mkClosureLFInfo about this; so if the binder
186 -- *was* a free var of its RHS, mkClosureLFInfo thinks it *is*
187 -- stored in the closure itself, so it will make sure that
188 -- Node points to it...
190 is_elem = isIn "cgRhsClosure"
192 binder_is_a_fv = binder `is_elem` fvs
193 reduced_fvs = if binder_is_a_fv
194 then fvs `minusList` [binder]
197 mapFCs getCAddrModeAndInfo reduced_fvs `thenFC` \ amodes_and_info ->
199 fvs_w_amodes_and_info = reduced_fvs `zip` amodes_and_info
201 closure_info :: ClosureInfo
202 bind_details :: [((Id, (CAddrMode, LambdaFormInfo)), VirtualHeapOffset)]
204 (closure_info, bind_details)
205 = layOutDynClosure (idName binder) get_kind fvs_w_amodes_and_info lf_info
207 bind_fv ((id, (_, lf_info)), offset) = bindNewToNode id offset lf_info
209 amodes_w_offsets = [(amode,offset) | ((_, (amode,_)), offset) <- bind_details]
211 get_kind (id, amode_and_info) = idPrimRep id
213 -- BUILD ITS INFO TABLE AND CODE
216 mapCs bind_fv bind_details `thenC`
218 -- Bind the binder itself, if it is a free var
219 (if binder_is_a_fv then
220 bindNewToReg binder node lf_info
225 closureCodeBody binder_info closure_info cc args body
230 (use_cc, blame_cc) = chooseDynCostCentres cc args fvs body
232 allocDynClosure closure_info use_cc blame_cc amodes_w_offsets
233 ) `thenFC` \ heap_offset ->
236 returnFC (binder, heapIdInfo binder heap_offset lf_info)
239 %************************************************************************
241 \subsection[code-for-closures]{The code for closures}
243 %************************************************************************
246 closureCodeBody :: StgBinderInfo
247 -> ClosureInfo -- Lots of information about this closure
248 -> CostCentreStack -- Optional cost centre attached to closure
254 There are two main cases for the code for closures. If there are {\em
255 no arguments}, then the closure is a thunk, and not in normal form.
256 So it should set up an update frame (if it is shared). Also, it has
257 no argument satisfaction check, so fast and slow entry-point labels
261 closureCodeBody binder_info closure_info cc [] body
262 = -- thunks cannot have a primitive type!
263 getAbsC body_code `thenFC` \ body_absC ->
264 moduleName `thenFC` \ mod_name ->
266 absC (CClosureInfoAndCode closure_info body_absC Nothing
269 cl_descr mod_name = closureDescription mod_name (closureName closure_info)
271 body_label = entryLabelFromCI closure_info
273 is_box = case body of { StgApp fun [] -> True; _ -> False }
275 body_code = profCtrC SLIT("TICK_ENT_THK") [] `thenC`
276 thunkWrapper closure_info body_label (
277 -- We only enter cc after setting up update so that cc
278 -- of enclosing scope will be recorded in update frame
279 -- CAF/DICT functions will be subsumed by this enclosing cc
280 enterCostCentreCode closure_info cc IsThunk is_box `thenC`
284 If there is {\em at least one argument}, then this closure is in
285 normal form, so there is no need to set up an update frame. On the
286 other hand, we do have to check that there are enough args, and
287 perform an update if not!
289 The Macros for GrAnSim are produced at the beginning of the
290 argSatisfactionCheck (by calling fetchAndReschedule). There info if
291 Node points to closure is available. -- HWL
294 closureCodeBody binder_info closure_info cc all_args body
295 = getEntryConvention name lf_info
296 (map idPrimRep all_args) `thenFC` \ entry_conv ->
298 -- get the current virtual Sp (it might not be zero, eg. if we're
299 -- compiling a let-no-escape).
300 getVirtSp `thenFC` \vSp ->
303 -- Figure out what is needed and what isn't
305 -- SDM: need everything for now in case the heap/stack check refers
307 slow_code_needed = True
308 --slowFunEntryCodeRequired name binder_info entry_conv
309 info_table_needed = True
310 --funInfoTableRequired name binder_info lf_info
312 -- Arg mapping for standard (slow) entry point; all args on stack,
314 (sp_all_args, arg_offsets, arg_tags)
315 = mkTaggedVirtStkOffsets vSp idPrimRep all_args
317 -- Arg mapping for the fast entry point; as many args as poss in
318 -- registers; the rest on the stack
319 -- arg_regs are the registers used for arg passing
320 -- stk_args are the args which are passed on the stack
322 -- Args passed on the stack are tagged, but the tags may not
323 -- actually be present (just gaps) if the function is called
324 -- by jumping directly to the fast entry point.
326 arg_regs = case entry_conv of
327 DirectEntry lbl arity regs -> regs
328 other -> panic "closureCodeBody:arg_regs"
330 num_arg_regs = length arg_regs
332 (reg_args, stk_args) = splitAt num_arg_regs all_args
334 (sp_stk_args, stk_offsets, stk_tags)
335 = mkTaggedVirtStkOffsets vSp idPrimRep stk_args
337 -- HWL; Note: empty list of live regs in slow entry code
338 -- Old version (reschedule combined with heap check);
339 -- see argSatisfactionCheck for new version
340 --slow_entry_code = forceHeapCheck [node] True slow_entry_code'
341 -- where node = UnusedReg PtrRep 1
342 --slow_entry_code = forceHeapCheck [] True slow_entry_code'
345 = profCtrC SLIT("TICK_ENT_FUN_STD") [
346 CLbl ticky_ctr_label DataPtrRep
349 -- Bind args, and record expected position of stk ptrs
350 mapCs bindNewToStack arg_offsets `thenC`
351 setRealAndVirtualSp sp_all_args `thenC`
353 argSatisfactionCheck closure_info `thenC`
355 -- OK, so there are enough args. Now we need to stuff as
356 -- many of them in registers as the fast-entry code
357 -- expects. Note that the zipWith will give up when it hits
358 -- the end of arg_regs.
360 mapFCs getCAddrMode all_args `thenFC` \ stk_amodes ->
361 absC (mkAbstractCs (zipWith assign_to_reg arg_regs stk_amodes))
364 -- Now adjust real stack pointers (no need to adjust Hp,
365 -- but call this function for convenience).
366 adjustSpAndHp sp_stk_args `thenC`
368 absC (CFallThrough (CLbl fast_label CodePtrRep))
370 assign_to_reg reg_id amode = CAssign (CReg reg_id) amode
373 -- Old version (reschedule combined with heap check);
374 -- see argSatisfactionCheck for new version
375 -- fast_entry_code = forceHeapCheck [] True fast_entry_code'
378 = moduleName `thenFC` \ mod_name ->
379 profCtrC SLIT("TICK_CTR") [
380 CLbl ticky_ctr_label DataPtrRep,
381 mkCString (_PK_ (ppr_for_ticky_name mod_name name)),
382 mkIntCLit stg_arity, -- total # of args
383 mkIntCLit sp_stk_args, -- # passed on stk
384 mkCString (_PK_ (map (showTypeCategory . idType) all_args))
387 profCtrC SLIT("TICK_ENT_FUN_DIRECT") [
388 CLbl ticky_ctr_label DataPtrRep
391 -- Nuked for now; see comment at end of file
392 -- CString (_PK_ (show_wrapper_name wrapper_maybe)),
393 -- CString (_PK_ (show_wrapper_arg_kinds wrapper_maybe))
396 -- Bind args to regs/stack as appropriate, and
397 -- record expected position of sps.
398 bindArgsToRegs reg_args arg_regs `thenC`
399 mapCs bindNewToStack stk_offsets `thenC`
400 setRealAndVirtualSp sp_stk_args `thenC`
402 -- free up the stack slots containing tags
403 freeStackSlots (map fst stk_tags) `thenC`
405 -- Enter the closures cc, if required
406 enterCostCentreCode closure_info cc IsFunction False `thenC`
409 funWrapper closure_info arg_regs stk_tags info_label (cgExpr body)
412 setTickyCtrLabel ticky_ctr_label (
414 -- Make a labelled code-block for the slow and fast entry code
415 forkAbsC (if slow_code_needed then slow_entry_code else absC AbsCNop)
416 `thenFC` \ slow_abs_c ->
417 forkAbsC fast_entry_code `thenFC` \ fast_abs_c ->
418 moduleName `thenFC` \ mod_name ->
420 -- Now either construct the info table, or put the fast code in alone
421 -- (We never have slow code without an info table)
422 -- XXX probably need the info table and slow entry code in case of
423 -- a heap check failure.
425 if info_table_needed then
426 CClosureInfoAndCode closure_info slow_abs_c (Just fast_abs_c)
429 CCodeBlock fast_label fast_abs_c
433 ticky_ctr_label = mkRednCountsLabel name
435 stg_arity = length all_args
436 lf_info = closureLFInfo closure_info
438 cl_descr mod_name = closureDescription mod_name name
440 -- Manufacture labels
441 name = closureName closure_info
442 fast_label = mkFastEntryLabel name stg_arity
443 info_label = mkInfoTableLabel name
446 -- When printing the name of a thing in a ticky file, we want to
447 -- give the module name even for *local* things. We print
448 -- just "x (M)" rather that "M.x" to distinguish them from the global kind.
449 ppr_for_ticky_name mod_name name
450 | isLocalName name = showSDocDebug (ppr name <+> (parens (ppr mod_name)))
451 | otherwise = showSDocDebug (ppr name)
454 For lexically scoped profiling we have to load the cost centre from
455 the closure entered, if the costs are not supposed to be inherited.
456 This is done immediately on entering the fast entry point.
458 Load current cost centre from closure, if not inherited.
459 Node is guaranteed to point to it, if profiling and not inherited.
462 data IsThunk = IsThunk | IsFunction -- Bool-like, local
468 :: ClosureInfo -> CostCentreStack
470 -> Bool -- is_box: this closure is a special box introduced by SCCfinal
473 enterCostCentreCode closure_info ccs is_thunk is_box
474 = if not opt_SccProfilingOn then
477 ASSERT(not (noCCSAttached ccs))
479 if isSubsumedCCS ccs then
480 ASSERT(isToplevClosure closure_info)
481 ASSERT(is_thunk == IsFunction)
482 costCentresC SLIT("ENTER_CCS_FSUB") []
484 else if isCurrentCCS ccs then
485 if re_entrant && not is_box
486 then costCentresC SLIT("ENTER_CCS_FCL") [CReg node]
487 else costCentresC SLIT("ENTER_CCS_TCL") [CReg node]
489 else if isCafCCS ccs then
490 ASSERT(isToplevClosure closure_info)
491 ASSERT(is_thunk == IsThunk)
492 -- might be a PAP, in which case we want to subsume costs
494 then costCentresC SLIT("ENTER_CCS_FSUB") []
495 else costCentresC SLIT("ENTER_CCS_CAF") c_ccs
497 else panic "enterCostCentreCode"
500 c_ccs = [mkCCostCentreStack ccs]
501 re_entrant = closureReEntrant closure_info
504 %************************************************************************
506 \subsubsection[pre-closure-code-stuff]{Pre-closure-code code}
508 %************************************************************************
510 The argument-satisfaction check code is placed after binding
511 the arguments to their stack locations. Hence, the virtual stack
512 pointer is pointing after all the args, and virtual offset 1 means
513 the base of frame and hence most distant arg. Hence
514 virtual offset 0 is just beyond the most distant argument; the
515 relative offset of this word tells how many words of arguments
519 argSatisfactionCheck :: ClosureInfo -> Code
521 argSatisfactionCheck closure_info
523 = nodeMustPointToIt (closureLFInfo closure_info) `thenFC` \ node_points ->
526 emit_gran_macros = opt_GranMacros
530 -- absC (CMacroStmt GRAN_FETCH []) `thenC`
531 -- forceHeapCheck [] node_points (absC AbsCNop) `thenC`
534 then fetchAndReschedule [] node_points
535 else yield [] node_points
536 else absC AbsCNop) `thenC`
538 getSpRelOffset 0 `thenFC` \ (SpRel sp) ->
541 rel_arg = mkIntCLit off
545 absC (CMacroStmt ARGS_CHK [rel_arg]) -- node already points
547 absC (CMacroStmt ARGS_CHK_LOAD_NODE [rel_arg, set_Node_to_this])
549 -- We must tell the arg-satis macro whether Node is pointing to
550 -- the closure or not. If it isn't so pointing, then we give to
551 -- the macro the (static) address of the closure.
553 set_Node_to_this = CLbl (closureLabelFromCI closure_info) PtrRep
556 %************************************************************************
558 \subsubsection[closure-code-wrappers]{Wrappers around closure code}
560 %************************************************************************
563 thunkWrapper:: ClosureInfo -> CLabel -> Code -> Code
564 thunkWrapper closure_info lbl thunk_code
565 = -- Stack and heap overflow checks
566 nodeMustPointToIt (closureLFInfo closure_info) `thenFC` \ node_points ->
569 emit_gran_macros = opt_GranMacros
571 -- HWL: insert macros for GrAnSim; 2 versions depending on liveness of node
572 -- (we prefer fetchAndReschedule-style context switches to yield ones)
575 then fetchAndReschedule [] node_points
576 else yield [] node_points
577 else absC AbsCNop) `thenC`
579 -- stack and/or heap checks
580 thunkChecks lbl node_points (
582 -- Overwrite with black hole if necessary
583 blackHoleIt closure_info node_points `thenC`
585 setupUpdate closure_info ( -- setupUpdate *encloses* the rest
587 -- Finally, do the business
591 funWrapper :: ClosureInfo -- Closure whose code body this is
592 -> [MagicId] -- List of argument registers (if any)
593 -> [(VirtualSpOffset,Int)] -- tagged stack slots
594 -> CLabel -- info table for heap check ret.
595 -> Code -- Body of function being compiled
597 funWrapper closure_info arg_regs stk_tags info_label fun_body
598 = -- Stack overflow check
599 nodeMustPointToIt (closureLFInfo closure_info) `thenFC` \ node_points ->
601 emit_gran_macros = opt_GranMacros
605 then yield arg_regs node_points
606 else absC AbsCNop) `thenC`
608 -- heap and/or stack checks
609 fastEntryChecks arg_regs stk_tags info_label node_points (
611 -- Finally, do the business
617 %************************************************************************
619 \subsubsubsection[update-and-BHs]{Update and black-hole wrappers}
621 %************************************************************************
625 blackHoleIt :: ClosureInfo -> Bool -> Code -- Only called for closures with no args
627 blackHoleIt closure_info node_points
628 = if blackHoleOnEntry closure_info && node_points
631 info_label = infoTableLabelFromCI closure_info
632 args = [ CLbl info_label DataPtrRep ]
634 absC (if closureSingleEntry(closure_info) then
635 CMacroStmt UPD_BH_SINGLE_ENTRY args
637 CMacroStmt UPD_BH_UPDATABLE args)
643 setupUpdate :: ClosureInfo -> Code -> Code -- Only called for closures with no args
644 -- Nota Bene: this function does not change Node (even if it's a CAF),
645 -- so that the cost centre in the original closure can still be
646 -- extracted by a subsequent ENTER_CC_TCL
648 -- I've tidied up the code for this function, but it should still do the same as
649 -- it did before (modulo ticky stuff). KSW 1999-04.
650 setupUpdate closure_info code
651 = if closureReEntrant closure_info
655 case (closureUpdReqd closure_info, isStaticClosure closure_info) of
656 (False,False) -> profCtrC SLIT("TICK_UPDF_OMITTED") [] `thenC`
658 (False,True ) -> (if opt_DoTickyProfiling
660 -- blackhole the SE CAF
661 link_caf seCafBlackHoleClosureInfo `thenFC` \ _ -> nopC
664 profCtrC SLIT("TICK_UPD_CAF_BH_SINGLE_ENTRY") [mkCString cl_name] `thenC`
665 profCtrC SLIT("TICK_UPDF_OMITTED") [] `thenC`
667 (True ,False) -> pushUpdateFrame (CReg node) code
668 (True ,True ) -> -- blackhole the (updatable) CAF:
669 link_caf cafBlackHoleClosureInfo `thenFC` \ update_closure ->
670 profCtrC SLIT("TICK_UPD_CAF_BH_UPDATABLE") [mkCString cl_name] `thenC`
671 pushUpdateFrame update_closure code
673 cl_name :: FAST_STRING
674 cl_name = (occNameFS . nameOccName . closureName) closure_info
676 link_caf :: (ClosureInfo -> ClosureInfo) -- function yielding BH closure_info
677 -> FCode CAddrMode -- Returns amode for closure to be updated
679 = -- To update a CAF we must allocate a black hole, link the CAF onto the
680 -- CAF list, then update the CAF to point to the fresh black hole.
681 -- This function returns the address of the black hole, so it can be
682 -- updated with the new value when available.
684 -- Alloc black hole specifying CC_HDR(Node) as the cost centre
685 -- Hack Warning: Using a CLitLit to get CAddrMode !
687 use_cc = CLitLit SLIT("CCS_HDR(R1.p)") PtrRep
690 allocDynClosure (bhCI closure_info) use_cc blame_cc [] `thenFC` \ heap_offset ->
691 getHpRelOffset heap_offset `thenFC` \ hp_rel ->
692 let amode = CAddr hp_rel
694 absC (CMacroStmt UPD_CAF [CReg node, amode]) `thenC`
698 %************************************************************************
700 \subsection[CgClosure-Description]{Profiling Closure Description.}
702 %************************************************************************
704 For "global" data constructors the description is simply occurrence
705 name of the data constructor itself (see \ref{CgConTbls-info-tables}).
707 Otherwise it is determind by @closureDescription@ from the let
711 closureDescription :: Module -- Module
712 -> Name -- Id of closure binding
715 -- Not called for StgRhsCon which have global info tables built in
716 -- CgConTbls.lhs with a description generated from the data constructor
718 closureDescription mod_name name
728 chooseDynCostCentres ccs args fvs body
730 use_cc -- cost-centre we record in the object
731 = if currentOrSubsumedCCS ccs
732 then CReg CurCostCentre
733 else mkCCostCentreStack ccs
735 blame_cc -- cost-centre on whom we blame the allocation
736 = case (args, fvs, body) of
737 ([], _, StgApp fun [{-no args-}])
738 -> mkCCostCentreStack overheadCCS
741 -- if it's an utterly trivial RHS, then it must be
742 -- one introduced by boxHigherOrderArgs for profiling,
743 -- so we charge it to "OVERHEAD".
745 -- This looks like a HACK to me --SDM
752 ========================================================================
753 OLD CODE THAT EMITTED INFORMATON FOR QUANTITATIVE ANALYSIS
755 It's pretty wierd, so I've nuked it for now. SLPJ Nov 96
758 getWrapperArgTypeCategories
759 :: Type -- wrapper's type
760 -> StrictnessInfo bdee -- strictness info about its args
763 getWrapperArgTypeCategories _ NoStrictnessInfo = Nothing
764 getWrapperArgTypeCategories _ BottomGuaranteed
765 = trace "getWrapperArgTypeCategories:BottomGuaranteed!" Nothing -- wrong
766 getWrapperArgTypeCategories _ (StrictnessInfo [] _) = Nothing
768 getWrapperArgTypeCategories ty (StrictnessInfo arg_info _)
769 = Just (mkWrapperArgTypeCategories ty arg_info)
771 mkWrapperArgTypeCategories
772 :: Type -- wrapper's type
773 -> [Demand] -- info about its arguments
774 -> String -- a string saying lots about the args
776 mkWrapperArgTypeCategories wrapper_ty wrap_info
777 = case (splitFunTy_maybe wrapper_ty) of { Just (arg_tys,_) ->
778 map do_one (wrap_info `zip` (map showTypeCategory arg_tys)) }
780 -- ToDo: this needs FIXING UP (it was a hack anyway...)
781 do_one (WwPrim, _) = 'P'
782 do_one (WwEnum, _) = 'E'
783 do_one (WwStrict, arg_ty_char) = arg_ty_char
784 do_one (WwUnpack _ _ _, arg_ty_char)
785 = if arg_ty_char `elem` "CIJFDTS"
786 then toLower arg_ty_char
787 else if arg_ty_char == '+' then 't'
788 else trace ("mkWrapp..:funny char:"++[arg_ty_char]) '-'
789 do_one (other_wrap_info, _) = '-'