2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 % $Id: CgClosure.lhs,v 1.50 2001/10/03 13:59:22 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 )
60 import FastTypes ( iBox )
63 %********************************************************
65 \subsection[closures-no-free-vars]{Top-level closures}
67 %********************************************************
69 For closures bound at top level, allocate in static space.
70 They should have no free variables.
74 -> CostCentreStack -- Optional cost centre annotation
80 -> FCode (Id, CgIdInfo)
82 cgTopRhsClosure id ccs binder_info srt args body lf_info
85 getSRTInfo srt `thenFC` \ srt_info ->
88 closure_info = layOutStaticNoFVClosure name lf_info srt_info
89 closure_label = mkClosureLabel name
90 cg_id_info = stableAmodeIdInfo id (CLbl closure_label PtrRep) lf_info
93 -- BUILD THE OBJECT (IF NECESSARY)
94 ({- if staticClosureRequired name binder_info lf_info
96 (if opt_SccProfilingOn
99 closure_label -- Labelled with the name on lhs of defn
101 (mkCCostCentreStack ccs)
105 closure_label -- Labelled with the name on lhs of defn
115 -- GENERATE THE INFO TABLE (IF NECESSARY)
116 forkClosureBody (closureCodeBody binder_info closure_info
121 returnFC (id, cg_id_info)
125 %********************************************************
127 \subsection[non-top-level-closures]{Non top-level closures}
129 %********************************************************
131 For closures with free vars, allocate in heap.
136 -> CostCentreStack -- Optional cost centre annotation
142 -> [StgArg] -- payload
143 -> FCode (Id, CgIdInfo)
145 cgStdRhsClosure binder cc binder_info fvs args body lf_info payload
146 -- AHA! A STANDARD-FORM THUNK
148 -- LAY OUT THE OBJECT
149 getArgAmodes payload `thenFC` \ amodes ->
151 (closure_info, amodes_w_offsets)
152 = layOutDynClosure (idName binder) getAmodeRep amodes lf_info NoC_SRT
153 -- No SRT for a standard-form closure
155 (use_cc, blame_cc) = chooseDynCostCentres cc args fvs body
158 allocDynClosure closure_info use_cc blame_cc amodes_w_offsets
160 `thenFC` \ heap_offset ->
163 returnFC (binder, heapIdInfo binder heap_offset lf_info)
166 Here's the general case.
170 -> CostCentreStack -- Optional cost centre annotation
177 -> FCode (Id, CgIdInfo)
179 cgRhsClosure binder cc binder_info srt fvs args body lf_info
181 -- LAY OUT THE OBJECT
183 -- If the binder is itself a free variable, then don't store
184 -- it in the closure. Instead, just bind it to Node on entry.
185 -- NB we can be sure that Node will point to it, because we
186 -- havn't told mkClosureLFInfo about this; so if the binder
187 -- *was* a free var of its RHS, mkClosureLFInfo thinks it *is*
188 -- stored in the closure itself, so it will make sure that
189 -- Node points to it...
191 is_elem = isIn "cgRhsClosure"
193 binder_is_a_fv = binder `is_elem` fvs
194 reduced_fvs = if binder_is_a_fv
195 then fvs `minusList` [binder]
198 mapFCs getCAddrModeAndInfo reduced_fvs `thenFC` \ fvs_w_amodes_and_info ->
199 getSRTInfo srt `thenFC` \ srt_info ->
201 closure_info :: ClosureInfo
202 bind_details :: [((Id, CAddrMode, LambdaFormInfo), VirtualHeapOffset)]
204 (closure_info, bind_details)
205 = layOutDynClosure (idName binder) get_kind
206 fvs_w_amodes_and_info lf_info srt_info
208 bind_fv ((id, _, lf_info), offset) = bindNewToNode id offset lf_info
210 amodes_w_offsets = [(amode,offset) | ((_,amode,_), offset) <- bind_details]
212 get_kind (id, _, _) = idPrimRep id
214 -- BUILD ITS INFO TABLE AND CODE
217 mapCs bind_fv bind_details `thenC`
219 -- Bind the binder itself, if it is a free var
220 (if binder_is_a_fv then
221 bindNewToReg binder node lf_info
226 closureCodeBody binder_info closure_info cc args body
231 (use_cc, blame_cc) = chooseDynCostCentres cc args fvs body
233 allocDynClosure closure_info use_cc blame_cc amodes_w_offsets
234 ) `thenFC` \ heap_offset ->
237 returnFC (binder, heapIdInfo binder heap_offset lf_info)
240 %************************************************************************
242 \subsection[code-for-closures]{The code for closures}
244 %************************************************************************
247 closureCodeBody :: StgBinderInfo
248 -> ClosureInfo -- Lots of information about this closure
249 -> CostCentreStack -- Optional cost centre attached to closure
255 There are two main cases for the code for closures. If there are {\em
256 no arguments}, then the closure is a thunk, and not in normal form.
257 So it should set up an update frame (if it is shared). Also, it has
258 no argument satisfaction check, so fast and slow entry-point labels
262 closureCodeBody binder_info closure_info cc [] body
263 = -- thunks cannot have a primitive type!
264 getAbsC body_code `thenFC` \ body_absC ->
265 moduleName `thenFC` \ mod_name ->
267 absC (CClosureInfoAndCode closure_info body_absC Nothing
270 cl_descr mod_name = closureDescription mod_name (closureName closure_info)
272 body_label = entryLabelFromCI closure_info
274 is_box = case body of { StgApp fun [] -> True; _ -> False }
276 body_code = profCtrC SLIT("TICK_ENT_THK") [] `thenC`
277 thunkWrapper closure_info body_label (
278 -- We only enter cc after setting up update so that cc
279 -- of enclosing scope will be recorded in update frame
280 -- CAF/DICT functions will be subsumed by this enclosing cc
281 enterCostCentreCode closure_info cc IsThunk is_box `thenC`
285 If there is {\em at least one argument}, then this closure is in
286 normal form, so there is no need to set up an update frame. On the
287 other hand, we do have to check that there are enough args, and
288 perform an update if not!
290 The Macros for GrAnSim are produced at the beginning of the
291 argSatisfactionCheck (by calling fetchAndReschedule). There info if
292 Node points to closure is available. -- HWL
295 closureCodeBody binder_info closure_info cc all_args body
296 = getEntryConvention name lf_info
297 (map idPrimRep all_args) `thenFC` \ entry_conv ->
299 -- get the current virtual Sp (it might not be zero, eg. if we're
300 -- compiling a let-no-escape).
301 getVirtSp `thenFC` \vSp ->
304 -- Figure out what is needed and what isn't
306 -- SDM: need everything for now in case the heap/stack check refers
308 slow_code_needed = True
309 --slowFunEntryCodeRequired name binder_info entry_conv
310 info_table_needed = True
311 --funInfoTableRequired name binder_info lf_info
313 -- Arg mapping for standard (slow) entry point; all args on stack,
315 (sp_all_args, arg_offsets, _)
316 = mkTaggedVirtStkOffsets vSp idPrimRep all_args
318 -- Arg mapping for the fast entry point; as many args as poss in
319 -- registers; the rest on the stack
320 -- arg_regs are the registers used for arg passing
321 -- stk_args are the args which are passed on the stack
323 -- Args passed on the stack are tagged, but the tags may not
324 -- actually be present (just gaps) if the function is called
325 -- by jumping directly to the fast entry point.
327 arg_regs = case entry_conv of
328 DirectEntry lbl arity regs -> regs
329 other -> [] -- "(HWL ignored; no args passed in regs)"
331 num_arg_regs = length arg_regs
333 (reg_args, stk_args) = splitAt num_arg_regs all_args
335 (sp_stk_args, stk_offsets, stk_tags)
336 = mkTaggedVirtStkOffsets vSp idPrimRep stk_args
338 -- HWL; Note: empty list of live regs in slow entry code
339 -- Old version (reschedule combined with heap check);
340 -- see argSatisfactionCheck for new version
341 --slow_entry_code = forceHeapCheck [node] True slow_entry_code'
342 -- where node = UnusedReg PtrRep 1
343 --slow_entry_code = forceHeapCheck [] True slow_entry_code'
346 = profCtrC SLIT("TICK_ENT_FUN_STD") [
347 CLbl ticky_ctr_label DataPtrRep
350 -- Bind args, and record expected position of stk ptrs
351 mapCs bindNewToStack arg_offsets `thenC`
352 setRealAndVirtualSp sp_all_args `thenC`
354 argSatisfactionCheck closure_info arg_regs `thenC`
356 -- OK, so there are enough args. Now we need to stuff as
357 -- many of them in registers as the fast-entry code
358 -- expects. Note that the zipWith will give up when it hits
359 -- the end of arg_regs.
361 mapFCs getCAddrMode all_args `thenFC` \ stk_amodes ->
362 absC (mkAbstractCs (zipWith assign_to_reg arg_regs stk_amodes))
365 -- Now adjust real stack pointers (no need to adjust Hp,
366 -- but call this function for convenience).
367 adjustSpAndHp sp_stk_args `thenC`
369 absC (CFallThrough (CLbl fast_label CodePtrRep))
371 assign_to_reg reg_id amode = CAssign (CReg reg_id) amode
374 -- Old version (reschedule combined with heap check);
375 -- see argSatisfactionCheck for new version
376 -- fast_entry_code = forceHeapCheck [] True fast_entry_code'
379 mod_name <- moduleName
380 profCtrC SLIT("TICK_CTR") [
381 CLbl ticky_ctr_label DataPtrRep,
382 mkCString (_PK_ (ppr_for_ticky_name mod_name name)),
383 mkIntCLit stg_arity, -- total # of args
384 mkIntCLit sp_stk_args, -- # passed on stk
385 mkCString (_PK_ (map (showTypeCategory . idType) all_args))
388 profCtrC SLIT("TICK_ENT_FUN_DIRECT") [
389 CLbl ticky_ctr_label DataPtrRep
392 -- Nuked for now; see comment at end of file
393 -- CString (_PK_ (show_wrapper_name wrapper_maybe)),
394 -- CString (_PK_ (show_wrapper_arg_kinds wrapper_maybe))
397 -- Bind args to regs/stack as appropriate, and
398 -- record expected position of sps.
399 bindArgsToRegs reg_args arg_regs
400 mapCs bindNewToStack stk_offsets
401 setRealAndVirtualSp sp_stk_args
403 -- free up the stack slots containing tags
404 freeStackSlots (map fst stk_tags)
406 -- Enter the closures cc, if required
407 enterCostCentreCode closure_info cc IsFunction False
410 funWrapper closure_info arg_regs stk_tags info_label
411 (prof >> cgExpr body)
414 setTickyCtrLabel ticky_ctr_label (
416 -- Make a labelled code-block for the slow and fast entry code
417 forkAbsC (if slow_code_needed then slow_entry_code else absC AbsCNop)
418 `thenFC` \ slow_abs_c ->
419 forkAbsC fast_entry_code `thenFC` \ fast_abs_c ->
420 moduleName `thenFC` \ mod_name ->
422 -- Now either construct the info table, or put the fast code in alone
423 -- (We never have slow code without an info table)
424 -- XXX probably need the info table and slow entry code in case of
425 -- a heap check failure.
427 if info_table_needed then
428 CClosureInfoAndCode closure_info slow_abs_c (Just fast_abs_c)
431 CCodeBlock fast_label fast_abs_c
435 ticky_ctr_label = mkRednCountsLabel name
437 stg_arity = length all_args
438 lf_info = closureLFInfo closure_info
440 cl_descr mod_name = closureDescription mod_name name
442 -- Manufacture labels
443 name = closureName closure_info
444 fast_label = mkFastEntryLabel name stg_arity
445 info_label = mkInfoTableLabel name
448 -- When printing the name of a thing in a ticky file, we want to
449 -- give the module name even for *local* things. We print
450 -- just "x (M)" rather that "M.x" to distinguish them from the global kind.
451 ppr_for_ticky_name mod_name name
452 | isLocalName name = showSDocDebug (ppr name <+> (parens (ppr mod_name)))
453 | otherwise = showSDocDebug (ppr name)
456 For lexically scoped profiling we have to load the cost centre from
457 the closure entered, if the costs are not supposed to be inherited.
458 This is done immediately on entering the fast entry point.
460 Load current cost centre from closure, if not inherited.
461 Node is guaranteed to point to it, if profiling and not inherited.
464 data IsThunk = IsThunk | IsFunction -- Bool-like, local
470 :: ClosureInfo -> CostCentreStack
472 -> Bool -- is_box: this closure is a special box introduced by SCCfinal
475 enterCostCentreCode closure_info ccs is_thunk is_box
476 = if not opt_SccProfilingOn then
479 ASSERT(not (noCCSAttached ccs))
481 if isSubsumedCCS ccs then
482 ASSERT(isToplevClosure closure_info)
483 ASSERT(is_thunk == IsFunction)
484 costCentresC SLIT("ENTER_CCS_FSUB") []
486 else if isCurrentCCS ccs then
487 if re_entrant && not is_box
488 then costCentresC SLIT("ENTER_CCS_FCL") [CReg node]
489 else costCentresC SLIT("ENTER_CCS_TCL") [CReg node]
491 else if isCafCCS ccs then
492 ASSERT(isToplevClosure closure_info)
493 ASSERT(is_thunk == IsThunk)
494 -- might be a PAP, in which case we want to subsume costs
496 then costCentresC SLIT("ENTER_CCS_FSUB") []
497 else costCentresC SLIT("ENTER_CCS_CAF") c_ccs
499 else panic "enterCostCentreCode"
502 c_ccs = [mkCCostCentreStack ccs]
503 re_entrant = closureReEntrant closure_info
506 %************************************************************************
508 \subsubsection[pre-closure-code-stuff]{Pre-closure-code code}
510 %************************************************************************
512 The argument-satisfaction check code is placed after binding
513 the arguments to their stack locations. Hence, the virtual stack
514 pointer is pointing after all the args, and virtual offset 1 means
515 the base of frame and hence most distant arg. Hence
516 virtual offset 0 is just beyond the most distant argument; the
517 relative offset of this word tells how many words of arguments
521 argSatisfactionCheck :: ClosureInfo -> [MagicId] {-GRAN-} -> Code
523 argSatisfactionCheck closure_info arg_regs
525 = nodeMustPointToIt (closureLFInfo closure_info) `thenFC` \ node_points ->
528 -- emit_gran_macros = opt_GranMacros
532 -- absC (CMacroStmt GRAN_FETCH []) `thenC`
533 -- forceHeapCheck [] node_points (absC AbsCNop) `thenC`
535 -- then if node_points
536 -- then fetchAndReschedule arg_regs node_points
537 -- else yield arg_regs node_points
538 -- else absC AbsCNop) `thenC`
540 getSpRelOffset 0 `thenFC` \ (SpRel sp) ->
543 rel_arg = mkIntCLit off
547 absC (CMacroStmt ARGS_CHK [rel_arg]) -- node already points
549 absC (CMacroStmt ARGS_CHK_LOAD_NODE [rel_arg, set_Node_to_this])
551 -- We must tell the arg-satis macro whether Node is pointing to
552 -- the closure or not. If it isn't so pointing, then we give to
553 -- the macro the (static) address of the closure.
555 set_Node_to_this = CLbl (closureLabelFromCI closure_info) PtrRep
558 %************************************************************************
560 \subsubsection[closure-code-wrappers]{Wrappers around closure code}
562 %************************************************************************
565 thunkWrapper:: ClosureInfo -> CLabel -> Code -> Code
566 thunkWrapper closure_info lbl thunk_code
567 = -- Stack and heap overflow checks
568 nodeMustPointToIt (closureLFInfo closure_info) `thenFC` \ node_points ->
570 -- HWL: insert macros for GrAnSim; 2 versions depending on liveness of node
571 -- (we prefer fetchAndReschedule-style context switches to yield ones)
574 then fetchAndReschedule [] node_points
575 else yield [] node_points
576 else absC AbsCNop) `thenC`
578 -- stack and/or heap checks
579 thunkChecks lbl node_points (
581 -- Overwrite with black hole if necessary
582 blackHoleIt closure_info node_points `thenC`
584 setupUpdate closure_info ( -- setupUpdate *encloses* the rest
586 -- Finally, do the business
590 funWrapper :: ClosureInfo -- Closure whose code body this is
591 -> [MagicId] -- List of argument registers (if any)
592 -> [(VirtualSpOffset,Int)] -- tagged stack slots
593 -> CLabel -- info table for heap check ret.
594 -> Code -- Body of function being compiled
596 funWrapper closure_info arg_regs stk_tags info_label fun_body
597 = -- Stack overflow check
598 nodeMustPointToIt (closureLFInfo closure_info) `thenFC` \ node_points ->
601 then yield arg_regs node_points
602 else absC AbsCNop) `thenC`
604 -- heap and/or stack checks
605 fastEntryChecks arg_regs stk_tags info_label node_points (
607 -- Finally, do the business
613 %************************************************************************
615 \subsubsubsection[update-and-BHs]{Update and black-hole wrappers}
617 %************************************************************************
621 blackHoleIt :: ClosureInfo -> Bool -> Code -- Only called for closures with no args
623 blackHoleIt closure_info node_points
624 = if blackHoleOnEntry closure_info && node_points
627 info_label = infoTableLabelFromCI closure_info
628 args = [ CLbl info_label DataPtrRep ]
630 absC (if closureSingleEntry(closure_info) then
631 CMacroStmt UPD_BH_SINGLE_ENTRY args
633 CMacroStmt UPD_BH_UPDATABLE args)
639 setupUpdate :: ClosureInfo -> Code -> Code -- Only called for closures with no args
640 -- Nota Bene: this function does not change Node (even if it's a CAF),
641 -- so that the cost centre in the original closure can still be
642 -- extracted by a subsequent ENTER_CC_TCL
644 -- I've tidied up the code for this function, but it should still do the same as
645 -- it did before (modulo ticky stuff). KSW 1999-04.
646 setupUpdate closure_info code
647 = if closureReEntrant closure_info
651 case (closureUpdReqd closure_info, isStaticClosure closure_info) of
652 (False,False) -> profCtrC SLIT("TICK_UPDF_OMITTED") [] `thenC`
654 (False,True ) -> (if opt_DoTickyProfiling
656 -- blackhole the SE CAF
657 link_caf seCafBlackHoleClosureInfo `thenFC` \ _ -> nopC
660 profCtrC SLIT("TICK_UPD_CAF_BH_SINGLE_ENTRY") [mkCString cl_name] `thenC`
661 profCtrC SLIT("TICK_UPDF_OMITTED") [] `thenC`
663 (True ,False) -> pushUpdateFrame (CReg node) code
664 (True ,True ) -> -- blackhole the (updatable) CAF:
665 link_caf cafBlackHoleClosureInfo `thenFC` \ update_closure ->
666 profCtrC SLIT("TICK_UPD_CAF_BH_UPDATABLE") [mkCString cl_name] `thenC`
667 pushUpdateFrame update_closure code
669 cl_name :: FAST_STRING
670 cl_name = (occNameFS . nameOccName . closureName) closure_info
672 link_caf :: (ClosureInfo -> ClosureInfo) -- function yielding BH closure_info
673 -> FCode CAddrMode -- Returns amode for closure to be updated
675 = -- To update a CAF we must allocate a black hole, link the CAF onto the
676 -- CAF list, then update the CAF to point to the fresh black hole.
677 -- This function returns the address of the black hole, so it can be
678 -- updated with the new value when available.
680 -- Alloc black hole specifying CC_HDR(Node) as the cost centre
682 use_cc = CMacroExpr PtrRep CCS_HDR [nodeReg]
685 allocDynClosure (bhCI closure_info) use_cc blame_cc [] `thenFC` \ heap_offset ->
686 getHpRelOffset heap_offset `thenFC` \ hp_rel ->
687 let amode = CAddr hp_rel
689 absC (CMacroStmt UPD_CAF [CReg node, amode]) `thenC`
693 %************************************************************************
695 \subsection[CgClosure-Description]{Profiling Closure Description.}
697 %************************************************************************
699 For "global" data constructors the description is simply occurrence
700 name of the data constructor itself (see \ref{CgConTbls-info-tables}).
702 Otherwise it is determind by @closureDescription@ from the let
706 closureDescription :: Module -- Module
707 -> Name -- Id of closure binding
710 -- Not called for StgRhsCon which have global info tables built in
711 -- CgConTbls.lhs with a description generated from the data constructor
713 closureDescription mod_name name
723 chooseDynCostCentres ccs args fvs body
725 use_cc -- cost-centre we record in the object
726 = if currentOrSubsumedCCS ccs
727 then CReg CurCostCentre
728 else mkCCostCentreStack ccs
730 blame_cc -- cost-centre on whom we blame the allocation
731 = case (args, fvs, body) of
732 ([], _, StgApp fun [{-no args-}])
733 -> mkCCostCentreStack overheadCCS
736 -- if it's an utterly trivial RHS, then it must be
737 -- one introduced by boxHigherOrderArgs for profiling,
738 -- so we charge it to "OVERHEAD".
740 -- This looks like a HACK to me --SDM