2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 % $Id: CgExpr.lhs,v 1.43 2001/05/22 13:43:15 simonpj Exp $
6 %********************************************************
8 \section[CgExpr]{Converting @StgExpr@s}
10 %********************************************************
13 module CgExpr ( cgExpr ) where
15 #include "HsVersions.h"
17 import Constants ( mAX_SPEC_SELECTEE_SIZE, mAX_SPEC_AP_SIZE )
21 import AbsCUtils ( mkAbstractCs )
22 import CLabel ( mkClosureTblLabel )
24 import SMRep ( fixedHdrSize )
25 import CgBindery ( getArgAmodes, getArgAmode, CgIdInfo,
26 nukeDeadBindings, addBindC, addBindsC )
27 import CgCase ( cgCase, saveVolatileVarsAndRegs,
28 restoreCurrentCostCentre )
29 import CgClosure ( cgRhsClosure, cgStdRhsClosure )
30 import CgCon ( buildDynCon, cgReturnDataCon )
31 import CgLetNoEscape ( cgLetNoEscapeClosure )
32 import CgRetConv ( dataReturnConvPrim )
33 import CgTailCall ( cgTailCall, performReturn, performPrimReturn,
34 mkDynamicAlgReturnCode, mkPrimReturnCode,
35 tailCallPrimOp, returnUnboxedTuple
37 import ClosureInfo ( mkClosureLFInfo, mkSelectorLFInfo,
38 mkApLFInfo, layOutDynCon )
39 import CostCentre ( sccAbleCostCentre, isSccCountCostCentre )
40 import Id ( idPrimRep, idType, Id )
42 import PrimOp ( primOpOutOfLine, getPrimOpResultInfo, PrimOp(..), PrimOpResultInfo(..) )
43 import PrimRep ( PrimRep(..), isFollowableRep )
44 import TyCon ( maybeTyConSingleCon,
45 isUnboxedTupleTyCon, isEnumerationTyCon )
46 import Type ( Type, typePrimRep, tyConAppArgs, tyConAppTyCon, repType )
47 import Maybes ( maybeToBool )
48 import ListSetOps ( assocMaybe )
49 import Unique ( mkBuiltinUnique )
50 import BasicTypes ( TopLevelFlag(..), RecFlag(..) )
54 This module provides the support code for @StgToAbstractC@ to deal
55 with STG {\em expressions}. See also @CgClosure@, which deals
56 with closures, and @CgCon@, which deals with constructors.
59 cgExpr :: StgExpr -- input
63 %********************************************************
67 %********************************************************
69 ``Applications'' mean {\em tail calls}, a service provided by module
70 @CgTailCall@. This includes literals, which show up as
71 @(STGApp (StgLitArg 42) [])@.
74 cgExpr (StgApp fun args) = cgTailCall fun args
77 %********************************************************
79 %* STG ConApps (for inline versions) *
81 %********************************************************
84 cgExpr (StgConApp con args)
85 = getArgAmodes args `thenFC` \ amodes ->
86 cgReturnDataCon con amodes
89 Literals are similar to constructors; they return by putting
90 themselves in an appropriate register and returning to the address on
95 = performPrimReturn (text "literal" <+> ppr lit) (CLit lit)
99 %********************************************************
101 %* STG PrimApps (unboxed primitive ops) *
103 %********************************************************
105 Here is where we insert real live machine instructions.
107 NOTE about _ccall_GC_:
109 A _ccall_GC_ is treated as an out-of-line primop (returns True
110 for primOpOutOfLine) so that when we see the call in case context
111 case (ccall ...) of { ... }
112 we get a proper stack frame on the stack when we perform it. When we
113 get in a tail-call position, however, we need to actually perform the
114 call, so we treat it as an inline primop.
117 cgExpr (StgOpApp op@(StgFCallOp _ _) args res_ty)
118 = primRetUnboxedTuple op args res_ty
120 -- tagToEnum# is special: we need to pull the constructor out of the table,
121 -- and perform an appropriate return.
123 cgExpr (StgOpApp (StgPrimOp TagToEnumOp) [arg] res_ty)
124 = ASSERT(isEnumerationTyCon tycon)
125 getArgAmode arg `thenFC` \amode ->
126 -- save the tag in a temporary in case amode overlaps
128 absC (CAssign dyn_tag amode) `thenC`
132 (CLbl (mkClosureTblLabel tycon) PtrRep)
133 dyn_tag PtrRep) PtrRep))
134 (\ sequel -> mkDynamicAlgReturnCode tycon dyn_tag sequel)
136 dyn_tag = CTemp (mkBuiltinUnique 0) IntRep
138 -- if you're reading this code in the attempt to figure
139 -- out why the compiler panic'ed here, it is probably because
140 -- you used tagToEnum# in a non-monomorphic setting, e.g.,
141 -- intToTg :: Enum a => Int -> a ; intToTg (I# x#) = tagToEnum# x#
145 tycon = tyConAppTyCon res_ty
148 cgExpr x@(StgOpApp op@(StgPrimOp primop) args res_ty)
149 | primOpOutOfLine primop
150 = tailCallPrimOp primop args
153 = ASSERT(primop /= SeqOp) -- can't handle SeqOp
155 getArgAmodes args `thenFC` \ arg_amodes ->
157 case (getPrimOpResultInfo primop) of
160 let result_amode = CReg (dataReturnConvPrim kind) in
162 (COpStmt [result_amode] op arg_amodes [{-no vol_regs-}])
163 (mkPrimReturnCode (text "primapp)" <+> ppr x))
165 -- otherwise, must be returning an enumerated type (eg. Bool).
166 -- we've only got the tag in R2, so we have to load the constructor
170 | isUnboxedTupleTyCon tycon -> primRetUnboxedTuple op args res_ty
172 | isEnumerationTyCon tycon ->
174 (COpStmt [dyn_tag] op arg_amodes [{-no vol_regs-}])
176 absC (CAssign (CReg node) closure_lbl) `thenC`
177 mkDynamicAlgReturnCode tycon dyn_tag sequel)
180 -- Pull a unique out of thin air to put the tag in.
181 -- It shouldn't matter if this overlaps with anything - we're
182 -- about to return anyway.
183 dyn_tag = CTemp (mkBuiltinUnique 0) IntRep
185 closure_lbl = CVal (CIndex
186 (CLbl (mkClosureTblLabel tycon) PtrRep)
187 dyn_tag PtrRep) PtrRep
191 %********************************************************
193 %* Case expressions *
195 %********************************************************
196 Case-expression conversion is complicated enough to have its own
200 cgExpr (StgCase expr live_vars save_vars bndr srt alts)
201 = cgCase expr live_vars save_vars bndr srt alts
205 %********************************************************
209 %********************************************************
210 \subsection[let-and-letrec-codegen]{Converting @StgLet@ and @StgLetrec@}
213 cgExpr (StgLet (StgNonRec srt name rhs) expr)
214 = cgRhs srt name rhs `thenFC` \ (name, info) ->
215 addBindC name info `thenC`
218 cgExpr (StgLet (StgRec srt pairs) expr)
219 = fixC (\ new_bindings -> addBindsC new_bindings `thenC`
220 listFCs [ cgRhs srt b e | (b,e) <- pairs ]
221 ) `thenFC` \ new_bindings ->
223 addBindsC new_bindings `thenC`
228 cgExpr (StgLetNoEscape live_in_whole_let live_in_rhss bindings body)
229 = -- Figure out what volatile variables to save
230 nukeDeadBindings live_in_whole_let `thenC`
231 saveVolatileVarsAndRegs live_in_rhss
232 `thenFC` \ (save_assts, rhs_eob_info, maybe_cc_slot) ->
233 -- ToDo: cost centre???
234 restoreCurrentCostCentre maybe_cc_slot `thenFC` \ restore_cc ->
236 -- Save those variables right now!
237 absC save_assts `thenC`
239 -- Produce code for the rhss
240 -- and add suitable bindings to the environment
241 cgLetNoEscapeBindings live_in_rhss rhs_eob_info maybe_cc_slot bindings `thenC`
244 setEndOfBlockInfo rhs_eob_info (cgExpr body)
248 %********************************************************
252 %********************************************************
254 SCC expressions are treated specially. They set the current cost
257 cgExpr (StgSCC cc expr)
258 = ASSERT(sccAbleCostCentre cc)
261 [mkCCostCentre cc, mkIntCLit (if isSccCountCostCentre cc then 1 else 0)]
266 ToDo: counting of dict sccs ...
268 %********************************************************
270 %* Non-top-level bindings *
272 %********************************************************
273 \subsection[non-top-level-bindings]{Converting non-top-level bindings}
275 We rely on the support code in @CgCon@ (to do constructors) and
276 in @CgClosure@ (to do closures).
279 cgRhs :: SRT -> Id -> StgRhs -> FCode (Id, CgIdInfo)
280 -- the Id is passed along so a binding can be set up
282 cgRhs srt name (StgRhsCon maybe_cc con args)
283 = getArgAmodes args `thenFC` \ amodes ->
284 buildDynCon name maybe_cc con amodes `thenFC` \ idinfo ->
285 returnFC (name, idinfo)
287 cgRhs srt name (StgRhsClosure cc bi fvs upd_flag args body)
288 = mkRhsClosure name cc bi srt fvs upd_flag args body
291 mkRhsClosure looks for two special forms of the right-hand side:
295 If neither happens, it just calls mkClosureLFInfo. You might think
296 that mkClosureLFInfo should do all this, but it seems wrong for the
297 latter to look at the structure of an expression
301 We look at the body of the closure to see if it's a selector---turgid,
302 but nothing deep. We are looking for a closure of {\em exactly} the
305 ... = [the_fv] \ u [] ->
307 con a_1 ... a_n -> a_i
311 mkRhsClosure bndr cc bi srt
312 [the_fv] -- Just one free var
313 upd_flag -- Updatable thunk
315 body@(StgCase (StgApp scrutinee [{-no args-}])
316 _ _ _ _ -- ignore uniq, etc.
317 (StgAlgAlts (Just tycon)
318 [(con, params, use_mask,
319 (StgApp selectee [{-no args-}]))]
321 | the_fv == scrutinee -- Scrutinee is the only free variable
322 && maybeToBool maybe_offset -- Selectee is a component of the tuple
323 && offset_into_int <= mAX_SPEC_SELECTEE_SIZE -- Offset is small enough
324 = ASSERT(is_single_constructor)
325 cgStdRhsClosure bndr cc bi [the_fv] [] body lf_info [StgVarArg the_fv]
327 lf_info = mkSelectorLFInfo (idType bndr) offset_into_int
328 (isUpdatable upd_flag)
329 (_, params_w_offsets) = layOutDynCon con idPrimRep params
330 maybe_offset = assocMaybe params_w_offsets selectee
331 Just the_offset = maybe_offset
332 offset_into_int = the_offset - fixedHdrSize
333 is_single_constructor = maybeToBool (maybeTyConSingleCon tycon)
340 A more generic AP thunk of the form
342 x = [ x_1...x_n ] \.. [] -> x_1 ... x_n
344 A set of these is compiled statically into the RTS, so we just use
345 those. We could extend the idea to thunks where some of the x_i are
346 global ids (and hence not free variables), but this would entail
347 generating a larger thunk. It might be an option for non-optimising
350 We only generate an Ap thunk if all the free variables are pointers,
351 for semi-obvious reasons.
354 mkRhsClosure bndr cc bi srt
357 [] -- No args; a thunk
358 body@(StgApp fun_id args)
360 | length args + 1 == arity
361 && all isFollowableRep (map idPrimRep fvs)
362 && isUpdatable upd_flag
363 && arity <= mAX_SPEC_AP_SIZE
366 = cgStdRhsClosure bndr cc bi fvs [] body lf_info payload
369 lf_info = mkApLFInfo (idType bndr) upd_flag arity
370 -- the payload has to be in the correct order, hence we can't
372 payload = StgVarArg fun_id : args
379 mkRhsClosure bndr cc bi srt fvs upd_flag args body
380 = getSRTLabel `thenFC` \ srt_label ->
382 mkClosureLFInfo bndr NotTopLevel fvs upd_flag args srt_label srt
384 cgRhsClosure bndr cc bi fvs args body lf_info
388 %********************************************************
390 %* Let-no-escape bindings
392 %********************************************************
394 cgLetNoEscapeBindings live_in_rhss rhs_eob_info maybe_cc_slot
395 (StgNonRec srt binder rhs)
396 = cgLetNoEscapeRhs live_in_rhss rhs_eob_info maybe_cc_slot
397 NonRecursive srt binder rhs
398 `thenFC` \ (binder, info) ->
401 cgLetNoEscapeBindings live_in_rhss rhs_eob_info maybe_cc_slot
403 = fixC (\ new_bindings ->
404 addBindsC new_bindings `thenC`
405 listFCs [ cgLetNoEscapeRhs full_live_in_rhss
406 rhs_eob_info maybe_cc_slot Recursive srt b e
408 ) `thenFC` \ new_bindings ->
410 addBindsC new_bindings
412 -- We add the binders to the live-in-rhss set so that we don't
413 -- delete the bindings for the binder from the environment!
414 full_live_in_rhss = live_in_rhss `unionVarSet` (mkVarSet [b | (b,r) <- pairs])
417 :: StgLiveVars -- Live in rhss
419 -> Maybe VirtualSpOffset
424 -> FCode (Id, CgIdInfo)
426 cgLetNoEscapeRhs full_live_in_rhss rhs_eob_info maybe_cc_slot rec srt binder
427 (StgRhsClosure cc bi _ upd_flag args body)
428 = -- We could check the update flag, but currently we don't switch it off
429 -- for let-no-escaped things, so we omit the check too!
431 -- Updatable -> panic "cgLetNoEscapeRhs" -- Nothing to update!
432 -- other -> cgLetNoEscapeClosure binder cc bi live_in_whole_let live_in_rhss args body
433 cgLetNoEscapeClosure binder cc bi srt full_live_in_rhss rhs_eob_info
434 maybe_cc_slot rec args body
436 -- For a constructor RHS we want to generate a single chunk of code which
437 -- can be jumped to from many places, which will return the constructor.
438 -- It's easy; just behave as if it was an StgRhsClosure with a ConApp inside!
439 cgLetNoEscapeRhs full_live_in_rhss rhs_eob_info maybe_cc_slot rec srt binder
440 (StgRhsCon cc con args)
441 = cgLetNoEscapeClosure binder cc noBinderInfo{-safe-} srt
442 full_live_in_rhss rhs_eob_info maybe_cc_slot rec
443 [] --No args; the binder is data structure, not a function
447 Little helper for primitives that return unboxed tuples.
451 primRetUnboxedTuple :: StgOp -> [StgArg] -> Type -> Code
452 primRetUnboxedTuple op args res_ty
453 = getArgAmodes args `thenFC` \ arg_amodes ->
455 put all the arguments in temporaries so they don't get stomped when
456 we push the return address.
460 arg_uniqs = map mkBuiltinUnique [0 .. n_args-1]
461 arg_reps = map getArgPrimRep args
462 arg_temps = zipWith CTemp arg_uniqs arg_reps
464 absC (mkAbstractCs (zipWith CAssign arg_temps arg_amodes)) `thenC`
466 allocate some temporaries for the return values.
469 ty_args = tyConAppArgs (repType res_ty)
470 prim_reps = map typePrimRep ty_args
471 temp_uniqs = map mkBuiltinUnique [ n_args .. n_args + length ty_args - 1]
472 temp_amodes = zipWith CTemp temp_uniqs prim_reps
474 returnUnboxedTuple temp_amodes (absC (COpStmt temp_amodes op arg_temps []))