2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 % $Id: CgClosure.lhs,v 1.56 2002/03/14 15:27:17 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, isInternalName )
50 import Module ( Module, pprModule )
51 import ListSetOps ( minusList )
52 import PrimRep ( PrimRep(..) )
53 import PprType ( showTypeCategory )
54 import Util ( isIn, splitAtList )
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)
95 ({- if staticClosureRequired name binder_info lf_info
97 absC (mkStaticClosure closure_info ccs [] True)
103 -- GENERATE THE INFO TABLE (IF NECESSARY)
104 forkClosureBody (closureCodeBody binder_info closure_info
109 returnFC (id, cg_id_info)
113 %********************************************************
115 \subsection[non-top-level-closures]{Non top-level closures}
117 %********************************************************
119 For closures with free vars, allocate in heap.
124 -> CostCentreStack -- Optional cost centre annotation
130 -> [StgArg] -- payload
131 -> FCode (Id, CgIdInfo)
133 cgStdRhsClosure binder cc binder_info fvs args body lf_info payload
134 -- AHA! A STANDARD-FORM THUNK
136 -- LAY OUT THE OBJECT
137 getArgAmodes payload `thenFC` \ amodes ->
139 (closure_info, amodes_w_offsets)
140 = layOutDynClosure (idName binder) getAmodeRep amodes lf_info NoC_SRT
141 -- No SRT for a standard-form closure
143 (use_cc, blame_cc) = chooseDynCostCentres cc args fvs body
146 allocDynClosure closure_info use_cc blame_cc amodes_w_offsets
148 `thenFC` \ heap_offset ->
151 returnFC (binder, heapIdInfo binder heap_offset lf_info)
154 Here's the general case.
158 -> CostCentreStack -- Optional cost centre annotation
165 -> FCode (Id, CgIdInfo)
167 cgRhsClosure binder cc binder_info srt fvs args body lf_info
169 -- LAY OUT THE OBJECT
171 -- If the binder is itself a free variable, then don't store
172 -- it in the closure. Instead, just bind it to Node on entry.
173 -- NB we can be sure that Node will point to it, because we
174 -- havn't told mkClosureLFInfo about this; so if the binder
175 -- *was* a free var of its RHS, mkClosureLFInfo thinks it *is*
176 -- stored in the closure itself, so it will make sure that
177 -- Node points to it...
179 is_elem = isIn "cgRhsClosure"
181 binder_is_a_fv = binder `is_elem` fvs
182 reduced_fvs = if binder_is_a_fv
183 then fvs `minusList` [binder]
186 mapFCs getCAddrModeAndInfo reduced_fvs `thenFC` \ fvs_w_amodes_and_info ->
187 getSRTInfo srt `thenFC` \ srt_info ->
189 closure_info :: ClosureInfo
190 bind_details :: [((Id, CAddrMode, LambdaFormInfo), VirtualHeapOffset)]
192 (closure_info, bind_details)
193 = layOutDynClosure (idName binder) get_kind
194 fvs_w_amodes_and_info lf_info srt_info
196 bind_fv ((id, _, lf_info), offset) = bindNewToNode id offset lf_info
198 amodes_w_offsets = [(amode,offset) | ((_,amode,_), offset) <- bind_details]
200 get_kind (id, _, _) = idPrimRep id
202 -- BUILD ITS INFO TABLE AND CODE
205 mapCs bind_fv bind_details `thenC`
207 -- Bind the binder itself, if it is a free var
208 (if binder_is_a_fv then
209 bindNewToReg binder node lf_info
214 closureCodeBody binder_info closure_info cc args body
219 (use_cc, blame_cc) = chooseDynCostCentres cc args fvs body
221 allocDynClosure closure_info use_cc blame_cc amodes_w_offsets
222 ) `thenFC` \ heap_offset ->
225 returnFC (binder, heapIdInfo binder heap_offset lf_info)
228 %************************************************************************
230 \subsection[code-for-closures]{The code for closures}
232 %************************************************************************
235 closureCodeBody :: StgBinderInfo
236 -> ClosureInfo -- Lots of information about this closure
237 -> CostCentreStack -- Optional cost centre attached to closure
243 There are two main cases for the code for closures. If there are {\em
244 no arguments}, then the closure is a thunk, and not in normal form.
245 So it should set up an update frame (if it is shared). Also, it has
246 no argument satisfaction check, so fast and slow entry-point labels
250 closureCodeBody binder_info closure_info cc [] body
251 = -- thunks cannot have a primitive type!
252 getAbsC body_code `thenFC` \ body_absC ->
253 moduleName `thenFC` \ mod_name ->
255 absC (CClosureInfoAndCode closure_info body_absC Nothing
258 cl_descr mod_name = closureDescription mod_name (closureName closure_info)
260 body_label = entryLabelFromCI closure_info
262 is_box = case body of { StgApp fun [] -> True; _ -> False }
264 ticky_ent_lit = if (isStaticClosure closure_info)
265 then SLIT("TICK_ENT_STATIC_THK")
266 else SLIT("TICK_ENT_DYN_THK")
268 body_code = profCtrC ticky_ent_lit [] `thenC`
269 -- node always points when profiling, so this is ok:
271 thunkWrapper closure_info body_label (
272 -- We only enter cc after setting up update so
273 -- that cc of enclosing scope will be recorded
274 -- in update frame CAF/DICT functions will be
275 -- subsumed by this enclosing cc
276 enterCostCentreCode closure_info cc IsThunk is_box `thenC`
282 If there is {\em at least one argument}, then this closure is in
283 normal form, so there is no need to set up an update frame. On the
284 other hand, we do have to check that there are enough args, and
285 perform an update if not!
287 The Macros for GrAnSim are produced at the beginning of the
288 argSatisfactionCheck (by calling fetchAndReschedule). There info if
289 Node points to closure is available. -- HWL
292 closureCodeBody binder_info closure_info cc all_args body
293 = getEntryConvention name lf_info
294 (map idPrimRep all_args) `thenFC` \ entry_conv ->
296 -- get the current virtual Sp (it might not be zero, eg. if we're
297 -- compiling a let-no-escape).
298 getVirtSp `thenFC` \vSp ->
301 -- Figure out what is needed and what isn't
303 -- SDM: need everything for now in case the heap/stack check refers
305 slow_code_needed = True
306 --slowFunEntryCodeRequired name binder_info entry_conv
307 info_table_needed = True
308 --funInfoTableRequired name binder_info lf_info
310 -- Arg mapping for standard (slow) entry point; all args on stack,
312 (sp_all_args, arg_offsets, _)
313 = mkTaggedVirtStkOffsets vSp idPrimRep all_args
315 -- Arg mapping for the fast entry point; as many args as poss in
316 -- registers; the rest on the stack
317 -- arg_regs are the registers used for arg passing
318 -- stk_args are the args which are passed on the stack
320 -- Args passed on the stack are tagged, but the tags may not
321 -- actually be present (just gaps) if the function is called
322 -- by jumping directly to the fast entry point.
324 arg_regs = case entry_conv of
325 DirectEntry lbl arity regs -> regs
326 other -> [] -- "(HWL ignored; no args passed in regs)"
328 (reg_args, stk_args) = splitAtList arg_regs all_args
330 (sp_stk_args, stk_offsets, stk_tags)
331 = mkTaggedVirtStkOffsets vSp idPrimRep stk_args
333 -- HWL; Note: empty list of live regs in slow entry code
334 -- Old version (reschedule combined with heap check);
335 -- see argSatisfactionCheck for new version
336 --slow_entry_code = forceHeapCheck [node] True slow_entry_code'
337 -- where node = UnusedReg PtrRep 1
338 --slow_entry_code = forceHeapCheck [] True slow_entry_code'
341 = profCtrC slow_ticky_ent_lit [
342 CLbl ticky_ctr_label DataPtrRep
345 -- Bind args, and record expected position of stk ptrs
346 mapCs bindNewToStack arg_offsets `thenC`
347 setRealAndVirtualSp sp_all_args `thenC`
349 argSatisfactionCheck closure_info arg_regs `thenC`
351 -- OK, so there are enough args. Now we need to stuff as
352 -- many of them in registers as the fast-entry code
353 -- expects. Note that the zipWith will give up when it hits
354 -- the end of arg_regs.
356 mapFCs getCAddrMode all_args `thenFC` \ stk_amodes ->
357 absC (mkAbstractCs (zipWith assign_to_reg arg_regs stk_amodes))
360 -- Now adjust real stack pointers (no need to adjust Hp,
361 -- but call this function for convenience).
362 adjustSpAndHp sp_stk_args `thenC`
364 absC (CFallThrough (CLbl fast_label CodePtrRep))
366 assign_to_reg reg_id amode = CAssign (CReg reg_id) amode
369 -- Old version (reschedule combined with heap check);
370 -- see argSatisfactionCheck for new version
371 -- fast_entry_code = forceHeapCheck [] True fast_entry_code'
374 mod_name <- moduleName
375 profCtrC SLIT("TICK_CTR") [
376 CLbl ticky_ctr_label DataPtrRep,
377 mkCString (_PK_ (ppr_for_ticky_name mod_name name)),
378 mkIntCLit stg_arity, -- total # of args
379 mkIntCLit sp_stk_args, -- # passed on stk
380 mkCString (_PK_ (map (showTypeCategory . idType) all_args))
383 profCtrC fast_ticky_ent_lit [
384 CLbl ticky_ctr_label DataPtrRep
387 -- Nuked for now; see comment at end of file
388 -- CString (_PK_ (show_wrapper_name wrapper_maybe)),
389 -- CString (_PK_ (show_wrapper_arg_kinds wrapper_maybe))
392 -- Bind args to regs/stack as appropriate, and
393 -- record expected position of sps.
394 bindArgsToRegs reg_args arg_regs
395 mapCs bindNewToStack stk_offsets
396 setRealAndVirtualSp sp_stk_args
398 -- free up the stack slots containing tags
399 freeStackSlots (map fst stk_tags)
401 -- Enter the closures cc, if required
402 enterCostCentreCode closure_info cc IsFunction False
405 funWrapper closure_info arg_regs stk_tags info_label
406 (prof >> cgExpr body)
409 setTickyCtrLabel ticky_ctr_label (
411 -- Make a labelled code-block for the slow and fast entry code
412 forkAbsC (if slow_code_needed then slow_entry_code else absC AbsCNop)
413 `thenFC` \ slow_abs_c ->
414 forkAbsC fast_entry_code `thenFC` \ fast_abs_c ->
415 moduleName `thenFC` \ mod_name ->
417 -- Now either construct the info table, or put the fast code in alone
418 -- (We never have slow code without an info table)
419 -- XXX probably need the info table and slow entry code in case of
420 -- a heap check failure.
422 if info_table_needed then
423 CClosureInfoAndCode closure_info slow_abs_c (Just fast_abs_c)
426 CCodeBlock fast_label fast_abs_c
430 ticky_ctr_label = mkRednCountsLabel name
432 (slow_ticky_ent_lit, fast_ticky_ent_lit) =
433 if (isStaticClosure closure_info)
434 then (SLIT("TICK_ENT_STATIC_FUN_STD"), SLIT("TICK_ENT_STATIC_FUN_DIRECT"))
435 else (SLIT("TICK_ENT_DYN_FUN_STD"), SLIT("TICK_ENT_DYN_FUN_DIRECT"))
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 | isInternalName 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 ASSERT2(not (noCCSAttached ccs), ppr (closureName closure_info) <+> ppr 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 isDerivedFromCurrentCCS 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 ->
600 -- enter for Ldv profiling
601 (if node_points then ldvEnter else nopC) `thenC`
604 then yield arg_regs node_points
605 else absC AbsCNop) `thenC`
607 -- heap and/or stack checks
608 fastEntryChecks arg_regs stk_tags info_label node_points (
610 -- Finally, do the business
616 %************************************************************************
618 \subsubsubsection[update-and-BHs]{Update and black-hole wrappers}
620 %************************************************************************
624 blackHoleIt :: ClosureInfo -> Bool -> Code -- Only called for closures with no args
626 blackHoleIt closure_info node_points
627 = if blackHoleOnEntry closure_info && node_points
630 info_label = infoTableLabelFromCI closure_info
631 args = [ CLbl info_label DataPtrRep ]
633 absC (if closureSingleEntry(closure_info) then
634 CMacroStmt UPD_BH_SINGLE_ENTRY args
636 CMacroStmt UPD_BH_UPDATABLE args)
642 setupUpdate :: ClosureInfo -> Code -> Code -- Only called for closures with no args
643 -- Nota Bene: this function does not change Node (even if it's a CAF),
644 -- so that the cost centre in the original closure can still be
645 -- extracted by a subsequent ENTER_CC_TCL
647 -- I've tidied up the code for this function, but it should still do the same as
648 -- it did before (modulo ticky stuff). KSW 1999-04.
649 setupUpdate closure_info code
650 = if closureReEntrant closure_info
654 case (closureUpdReqd closure_info, isStaticClosure closure_info) of
655 (False,False) -> profCtrC SLIT("TICK_UPDF_OMITTED") [] `thenC`
657 (False,True ) -> (if opt_DoTickyProfiling
659 -- blackhole the SE CAF
660 link_caf seCafBlackHoleClosureInfo `thenFC` \ _ -> nopC
663 profCtrC SLIT("TICK_UPD_CAF_BH_SINGLE_ENTRY") [mkCString cl_name] `thenC`
664 profCtrC SLIT("TICK_UPDF_OMITTED") [] `thenC`
666 (True ,False) -> pushUpdateFrame (CReg node) code
667 (True ,True ) -> -- blackhole the (updatable) CAF:
668 link_caf cafBlackHoleClosureInfo `thenFC` \ update_closure ->
669 profCtrC SLIT("TICK_UPD_CAF_BH_UPDATABLE") [mkCString cl_name] `thenC`
670 pushUpdateFrame update_closure code
672 cl_name :: FAST_STRING
673 cl_name = (occNameFS . nameOccName . closureName) closure_info
675 link_caf :: (ClosureInfo -> ClosureInfo) -- function yielding BH closure_info
676 -> FCode CAddrMode -- Returns amode for closure to be updated
678 = -- To update a CAF we must allocate a black hole, link the CAF onto the
679 -- CAF list, then update the CAF to point to the fresh black hole.
680 -- This function returns the address of the black hole, so it can be
681 -- updated with the new value when available.
683 -- Alloc black hole specifying CC_HDR(Node) as the cost centre
685 use_cc = CMacroExpr PtrRep CCS_HDR [nodeReg]
688 allocDynClosure (bhCI closure_info) use_cc blame_cc [] `thenFC` \ heap_offset ->
689 getHpRelOffset heap_offset `thenFC` \ hp_rel ->
690 let amode = CAddr hp_rel
692 absC (CMacroStmt UPD_CAF [CReg node, amode]) `thenC`
696 %************************************************************************
698 \subsection[CgClosure-Description]{Profiling Closure Description.}
700 %************************************************************************
702 For "global" data constructors the description is simply occurrence
703 name of the data constructor itself (see \ref{CgConTbls-info-tables}).
705 Otherwise it is determind by @closureDescription@ from the let
709 closureDescription :: Module -- Module
710 -> Name -- Id of closure binding
713 -- Not called for StgRhsCon which have global info tables built in
714 -- CgConTbls.lhs with a description generated from the data constructor
716 closureDescription mod_name name
726 chooseDynCostCentres ccs args fvs body
728 use_cc -- cost-centre we record in the object
729 = if currentOrSubsumedCCS ccs
730 then CReg CurCostCentre
731 else mkCCostCentreStack ccs
733 blame_cc -- cost-centre on whom we blame the allocation
734 = case (args, fvs, body) of
735 ([], _, StgApp fun [{-no args-}])
736 -> mkCCostCentreStack overheadCCS
739 -- if it's an utterly trivial RHS, then it must be
740 -- one introduced by boxHigherOrderArgs for profiling,
741 -- so we charge it to "OVERHEAD".
743 -- This looks like a HACK to me --SDM