2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 % $Id: CgExpr.lhs,v 1.35 2000/07/11 16:03:37 simonmar 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 DataCon ( DataCon, dataConTyCon )
43 import PrimOp ( primOpOutOfLine, ccallMayGC,
44 getPrimOpResultInfo, PrimOp(..), PrimOpResultInfo(..)
46 import PrimRep ( getPrimRepSize, PrimRep(..), isFollowableRep )
47 import TyCon ( maybeTyConSingleCon,
48 isUnboxedTupleTyCon, isEnumerationTyCon )
49 import Type ( Type, typePrimRep, splitTyConApp_maybe, repType )
50 import Maybes ( assocMaybe, maybeToBool )
51 import Unique ( mkBuiltinUnique )
52 import BasicTypes ( TopLevelFlag(..), RecFlag(..) )
56 This module provides the support code for @StgToAbstractC@ to deal
57 with STG {\em expressions}. See also @CgClosure@, which deals
58 with closures, and @CgCon@, which deals with constructors.
61 cgExpr :: StgExpr -- input
65 %********************************************************
69 %********************************************************
71 ``Applications'' mean {\em tail calls}, a service provided by module
72 @CgTailCall@. This includes literals, which show up as
73 @(STGApp (StgLitArg 42) [])@.
76 cgExpr (StgApp fun args) = cgTailCall fun args
79 %********************************************************
81 %* STG ConApps (for inline versions) *
83 %********************************************************
86 cgExpr (StgConApp con args)
87 = getArgAmodes args `thenFC` \ amodes ->
88 cgReturnDataCon con amodes
91 Literals are similar to constructors; they return by putting
92 themselves in an appropriate register and returning to the address on
97 = performPrimReturn (text "literal" <+> ppr lit) (CLit lit)
101 %********************************************************
103 %* STG PrimApps (unboxed primitive ops) *
105 %********************************************************
107 Here is where we insert real live machine instructions.
109 NOTE about _ccall_GC_:
111 A _ccall_GC_ is treated as an out-of-line primop (returns True
112 for primOpOutOfLine) so that when we see the call in case context
113 case (ccall ...) of { ... }
114 we get a proper stack frame on the stack when we perform it. When we
115 get in a tail-call position, however, we need to actually perform the
116 call, so we treat it as an inline primop.
119 cgExpr (StgPrimApp op@(CCallOp ccall) args res_ty)
120 = primRetUnboxedTuple op args res_ty
122 -- tagToEnum# is special: we need to pull the constructor out of the table,
123 -- and perform an appropriate return.
125 cgExpr (StgPrimApp TagToEnumOp [arg] res_ty)
126 = ASSERT(isEnumerationTyCon tycon)
127 getArgAmode arg `thenFC` \amode ->
128 -- save the tag in a temporary in case amode overlaps
130 absC (CAssign dyn_tag amode) `thenC`
134 (CLbl (mkClosureTblLabel tycon) PtrRep)
135 dyn_tag PtrRep) PtrRep))
136 (\ sequel -> mkDynamicAlgReturnCode tycon dyn_tag sequel)
138 dyn_tag = CTemp (mkBuiltinUnique 0) IntRep
140 -- if you're reading this code in the attempt to figure
141 -- out why the compiler panic'ed here, it is probably because
142 -- you used tagToEnum# in a non-monomorphic setting, e.g.,
143 -- intToTg :: Enum a => Int -> a ; intToTg (I# x#) = tagToEnum# x#
147 (Just (tycon,_)) = splitTyConApp_maybe res_ty
150 cgExpr x@(StgPrimApp op args res_ty)
151 | primOpOutOfLine op = tailCallPrimOp op args
153 = ASSERT(op /= SeqOp) -- can't handle SeqOp
155 getArgAmodes args `thenFC` \ arg_amodes ->
157 case (getPrimOpResultInfo op) 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 name rhs) expr)
214 = cgRhs name rhs `thenFC` \ (name, info) ->
215 addBindC name info `thenC`
218 cgExpr (StgLet (StgRec pairs) expr)
219 = fixC (\ new_bindings -> addBindsC new_bindings `thenC`
220 listFCs [ cgRhs 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 :: Id -> StgRhs -> FCode (Id, CgIdInfo)
280 -- the Id is passed along so a binding can be set up
282 cgRhs 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 name (StgRhsClosure cc bi srt@(NoSRT) fvs upd_flag args body)
288 = mkRhsClosure name cc bi srt fvs upd_flag args body
289 cgRhs name (StgRhsClosure cc bi srt@(SRT _ _) fvs upd_flag args body)
290 = mkRhsClosure name cc bi srt fvs upd_flag args body
293 mkRhsClosure looks for two special forms of the right-hand side:
297 If neither happens, it just calls mkClosureLFInfo. You might think
298 that mkClosureLFInfo should do all this, but it seems wrong for the
299 latter to look at the structure of an expression
303 We look at the body of the closure to see if it's a selector---turgid,
304 but nothing deep. We are looking for a closure of {\em exactly} the
307 ... = [the_fv] \ u [] ->
309 con a_1 ... a_n -> a_i
313 mkRhsClosure bndr cc bi srt
314 [the_fv] -- Just one free var
315 upd_flag -- Updatable thunk
317 body@(StgCase (StgApp scrutinee [{-no args-}])
318 _ _ _ _ -- ignore uniq, etc.
320 [(con, params, use_mask,
321 (StgApp selectee [{-no args-}]))]
323 | the_fv == scrutinee -- Scrutinee is the only free variable
324 && maybeToBool maybe_offset -- Selectee is a component of the tuple
325 && offset_into_int <= mAX_SPEC_SELECTEE_SIZE -- Offset is small enough
326 = ASSERT(is_single_constructor)
327 cgStdRhsClosure bndr cc bi [the_fv] [] body lf_info [StgVarArg the_fv]
329 lf_info = mkSelectorLFInfo (idType bndr) offset_into_int
330 (isUpdatable upd_flag)
331 (_, params_w_offsets) = layOutDynCon con idPrimRep params
332 maybe_offset = assocMaybe params_w_offsets selectee
333 Just the_offset = maybe_offset
334 offset_into_int = the_offset - fixedHdrSize
335 is_single_constructor = maybeToBool (maybeTyConSingleCon tycon)
336 tycon = dataConTyCon con
343 A more generic AP thunk of the form
345 x = [ x_1...x_n ] \.. [] -> x_1 ... x_n
347 A set of these is compiled statically into the RTS, so we just use
348 those. We could extend the idea to thunks where some of the x_i are
349 global ids (and hence not free variables), but this would entail
350 generating a larger thunk. It might be an option for non-optimising
353 We only generate an Ap thunk if all the free variables are pointers,
354 for semi-obvious reasons.
357 mkRhsClosure bndr cc bi srt
360 [] -- No args; a thunk
361 body@(StgApp fun_id args)
363 | length args + 1 == arity
364 && all isFollowableRep (map idPrimRep fvs)
365 && isUpdatable upd_flag
366 && arity <= mAX_SPEC_AP_SIZE
369 = cgStdRhsClosure bndr cc bi fvs [] body lf_info payload
372 lf_info = mkApLFInfo (idType bndr) upd_flag arity
373 -- the payload has to be in the correct order, hence we can't
375 payload = StgVarArg fun_id : args
382 mkRhsClosure bndr cc bi srt fvs upd_flag args body
383 = getSRTLabel `thenFC` \ srt_label ->
385 mkClosureLFInfo bndr NotTopLevel fvs upd_flag args srt_label srt
387 cgRhsClosure bndr cc bi fvs args body lf_info
391 %********************************************************
393 %* Let-no-escape bindings
395 %********************************************************
397 cgLetNoEscapeBindings live_in_rhss rhs_eob_info maybe_cc_slot (StgNonRec binder rhs)
398 = cgLetNoEscapeRhs live_in_rhss rhs_eob_info maybe_cc_slot
399 NonRecursive binder rhs
400 `thenFC` \ (binder, info) ->
403 cgLetNoEscapeBindings live_in_rhss rhs_eob_info maybe_cc_slot (StgRec pairs)
404 = fixC (\ new_bindings ->
405 addBindsC new_bindings `thenC`
406 listFCs [ cgLetNoEscapeRhs full_live_in_rhss
407 rhs_eob_info maybe_cc_slot Recursive b e
409 ) `thenFC` \ new_bindings ->
411 addBindsC new_bindings
413 -- We add the binders to the live-in-rhss set so that we don't
414 -- delete the bindings for the binder from the environment!
415 full_live_in_rhss = live_in_rhss `unionVarSet` (mkVarSet [b | (b,r) <- pairs])
418 :: StgLiveVars -- Live in rhss
420 -> Maybe VirtualSpOffset
424 -> FCode (Id, CgIdInfo)
426 cgLetNoEscapeRhs full_live_in_rhss rhs_eob_info maybe_cc_slot rec binder
427 (StgRhsClosure cc bi srt _ 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 maybe_cc_slot rec args body
435 -- For a constructor RHS we want to generate a single chunk of code which
436 -- can be jumped to from many places, which will return the constructor.
437 -- It's easy; just behave as if it was an StgRhsClosure with a ConApp inside!
438 cgLetNoEscapeRhs full_live_in_rhss rhs_eob_info maybe_cc_slot rec binder
439 (StgRhsCon cc con args)
440 = cgLetNoEscapeClosure binder cc stgArgOcc{-safe-} NoSRT full_live_in_rhss rhs_eob_info maybe_cc_slot rec
441 [] --No args; the binder is data structure, not a function
445 Little helper for primitives that return unboxed tuples.
449 primRetUnboxedTuple :: PrimOp -> [StgArg] -> Type -> Code
450 primRetUnboxedTuple op args res_ty
451 = getArgAmodes args `thenFC` \ arg_amodes ->
453 put all the arguments in temporaries so they don't get stomped when
454 we push the return address.
458 arg_uniqs = map mkBuiltinUnique [0 .. n_args-1]
459 arg_reps = map getArgPrimRep args
460 arg_temps = zipWith CTemp arg_uniqs arg_reps
462 absC (mkAbstractCs (zipWith CAssign arg_temps arg_amodes)) `thenC`
464 allocate some temporaries for the return values.
467 (tc,ty_args) = case splitTyConApp_maybe (repType res_ty) of
468 Nothing -> pprPanic "primRetUnboxedTuple" (ppr 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 []))