2 -- | Converts continuations into full proceedures.
3 -- The main work of the CPS transform that everything else is setting-up.
5 Continuation(..), continuationLabel,
6 ContinuationFormat(..),
9 #include "HsVersions.h"
13 import CmmBrokenBlock -- Data types only
18 import CgProf (curCCS, curCCSAddr)
19 import CgUtils (cmmOffsetW)
30 import MachRegs (callerSaveVolatileRegs)
31 -- HACK: this is part of the NCG so we shouldn't use this, but we need
32 -- it for now to eliminate the need for saved regs to be in CmmCall.
33 -- The long term solution is to factor callerSaveVolatileRegs
34 -- from nativeGen into CPS
36 -- The format for the call to a continuation
37 -- The fst is the arguments that must be passed to the continuation
38 -- by the continuation's caller.
39 -- The snd is the live values that must be saved on stack.
40 -- A Nothing indicates an ignored slot.
41 -- The head of each list is the stack top or the first parameter.
43 -- The format for live values for a particular continuation
44 -- All on stack for now.
45 -- Head element is the top of the stack (or just under the header).
46 -- Nothing means an empty slot.
47 -- Future possibilities include callee save registers (i.e. passing slots in register)
48 -- and heap memory (not sure if that's usefull at all though, but it may
49 -- be worth exploring the design space).
51 continuationLabel (Continuation _ l _ _ _) = l
52 data Continuation info =
54 info -- Left <=> Continuation created by the CPS
55 -- Right <=> Function or Proc point
56 CLabel -- Used to generate both info & entry labels
57 CmmFormals -- Argument locals live on entry (C-- procedure params)
58 Bool -- ^ True <=> GC block so ignore stack size
59 [BrokenBlock] -- Code, may be empty. The first block is
60 -- the entry point. The order is otherwise initially
61 -- unimportant, but at some point the code gen will
64 -- the BlockId of the first block does not give rise
65 -- to a label. To jump to the first block in a Proc,
66 -- use the appropriate CLabel.
68 data ContinuationFormat
69 = ContinuationFormat {
70 continuation_formals :: CmmFormals,
71 continuation_label :: Maybe CLabel, -- The label occupying the top slot
72 continuation_frame_size :: WordOff, -- Total frame size in words (not including arguments)
73 continuation_stack :: [Maybe LocalReg] -- local reg offsets from stack top
76 -- A block can be a continuation of a call
77 -- A block can be a continuation of another block (w/ or w/o joins)
78 -- A block can be an entry to a function
80 -----------------------------------------------------------------------------
81 continuationToProc :: (WordOff, WordOff, [(CLabel, ContinuationFormat)])
84 -> Continuation CmmInfo
86 continuationToProc (max_stack, update_frame_size, formats) stack_use uniques
87 (Continuation info label formals _ blocks) =
88 CmmProc info label formals (concat $ zipWith3 continuationToProc' uniques blocks (True : repeat False))
90 curr_format = maybe unknown_block id $ lookup label formats
91 unknown_block = panic "unknown BlockId in continuationToProc"
92 curr_stack = continuation_frame_size curr_format
93 arg_stack = argumentsSize localRegRep formals
95 param_stmts :: [CmmStmt]
96 param_stmts = function_entry curr_format
101 CmmInfo (Just gc_block) _ _ ->
102 gc_stack_check' stack_use arg_stack (max_stack - curr_stack)
103 CmmInfo Nothing _ _ ->
104 panic "continuationToProc: missing GC block"
106 update_stmts :: [CmmStmt]
109 CmmInfo _ (Just (UpdateFrame target args)) _ ->
110 pack_frame curr_stack update_frame_size (Just target) (map Just args) ++
111 adjust_sp_reg (curr_stack - update_frame_size)
112 CmmInfo _ Nothing _ -> []
114 -- At present neither the Cmm parser nor the code generator
115 -- produce code that will allow the target of a CmmCondBranch
116 -- or a CmmSwitch to become a continuation or a proc-point.
117 -- If future revisions, might allow these to happen
118 -- then special care will have to be take to allow for that case.
119 continuationToProc' :: [Unique]
123 continuationToProc' uniques (BrokenBlock ident entry stmts _ exit) is_entry =
124 prefix_blocks ++ [main_block]
127 case gc_prefix ++ param_prefix of
129 entry_stmts -> [BasicBlock prefix_id
130 (entry_stmts ++ [CmmBranch ident])]
132 prefix_unique : call_uniques = uniques
133 toCLabel = mkReturnPtLabel . getUnique
135 block_for_branch unique next
136 | (Just cont_format) <- lookup (toCLabel next) formats
138 new_next = BlockId unique
139 cont_stack = continuation_frame_size cont_format
140 arguments = map formal_to_actual (continuation_formals cont_format)
142 [BasicBlock new_next $
143 pack_continuation False curr_format cont_format ++
144 tail_call (curr_stack - cont_stack)
145 (CmmLit $ CmmLabel $ toCLabel next)
150 block_for_branch' :: Unique -> Maybe BlockId -> (Maybe BlockId, [CmmBasicBlock])
151 block_for_branch' _ Nothing = (Nothing, [])
152 block_for_branch' unique (Just next) = (Just new_next, new_blocks)
153 where (new_next, new_blocks) = block_for_branch unique next
157 FunctionEntry _ _ _ ->
158 -- Ugh, the statements for an update frame must come
159 -- *after* the GC check that was added at the beginning
160 -- of the CPS pass. So we have do edit the statements
161 -- a bit. This depends on the knowledge that the
162 -- statements in the first block are only the GC check.
163 -- That's fragile but it works for now.
164 BasicBlock ident (stmts ++ update_stmts ++ postfix_stmts)
165 ControlEntry -> BasicBlock ident (stmts ++ postfix_stmts)
166 ContinuationEntry _ _ _ -> BasicBlock ident (stmts ++ postfix_stmts)
167 prefix_id = BlockId prefix_unique
168 gc_prefix = case entry of
169 FunctionEntry _ _ _ -> gc_stmts
171 ContinuationEntry _ _ _ -> []
172 param_prefix = if is_entry
175 postfix_stmts = case exit of
177 if (mkReturnPtLabel $ getUnique next) == label
178 then [CmmBranch next]
179 else case lookup (mkReturnPtLabel $ getUnique next) formats of
180 Nothing -> [CmmBranch next]
182 pack_continuation False curr_format cont_format ++
183 tail_call (curr_stack - cont_stack)
184 (CmmLit $ CmmLabel $ mkReturnPtLabel $ getUnique next)
187 cont_stack = continuation_frame_size cont_format
188 arguments = map formal_to_actual (continuation_formals cont_format)
189 FinalSwitch expr targets -> [CmmSwitch expr targets]
190 FinalReturn arguments ->
192 (CmmLoad (CmmReg spReg) wordRep)
194 FinalJump target arguments ->
195 tail_call curr_stack target arguments
197 -- A regular Cmm function call
198 FinalCall next (CmmForeignCall target CmmCallConv)
199 results arguments _ _ ->
200 pack_continuation True curr_format cont_format ++
201 tail_call (curr_stack - cont_stack)
204 cont_format = maybe unknown_block id $
205 lookup (mkReturnPtLabel $ getUnique next) formats
206 cont_stack = continuation_frame_size cont_format
208 -- A safe foreign call
209 FinalCall next (CmmForeignCall target conv)
210 results arguments _ _ ->
212 foreignCall call_uniques' (CmmForeignCall new_target conv)
215 (call_uniques', target_stmts, new_target) =
216 maybeAssignTemp call_uniques target
219 FinalCall next (CmmPrim target)
220 results arguments _ _ ->
221 foreignCall call_uniques (CmmPrim target)
224 formal_to_actual reg = (CmmReg (CmmLocal reg), NoHint)
226 foreignCall :: [Unique] -> CmmCallTarget -> CmmHintFormals -> CmmActuals -> [CmmStmt]
227 foreignCall uniques call results arguments =
231 [CmmCall (CmmForeignCall suspendThread CCallConv)
233 [ (CmmReg (CmmGlobal BaseReg), PtrHint) ]
235 CmmCall call results new_args CmmUnsafe,
236 CmmCall (CmmForeignCall resumeThread CCallConv)
237 [ (new_base, PtrHint) ]
238 [ (CmmReg (CmmLocal id), PtrHint) ]
240 -- Assign the result to BaseReg: we
241 -- might now have a different Capability!
242 CmmAssign (CmmGlobal BaseReg) (CmmReg (CmmLocal new_base))] ++
244 loadThreadState tso_unique ++
245 [CmmJump (CmmReg spReg) (map (formal_to_actual . fst) results)]
247 (_, arg_stmts, new_args) =
248 loadArgsIntoTemps argument_uniques arguments
249 (caller_save, caller_load) =
250 callerSaveVolatileRegs (Just [{-only system regs-}])
251 new_base = LocalReg base_unique (cmmRegRep (CmmGlobal BaseReg)) KindNonPtr
252 id = LocalReg id_unique wordRep KindNonPtr
253 tso_unique : base_unique : id_unique : argument_uniques = uniques
255 -- -----------------------------------------------------------------------------
256 -- Save/restore the thread state in the TSO
258 suspendThread = CmmLit (CmmLabel (mkRtsCodeLabel SLIT("suspendThread")))
259 resumeThread = CmmLit (CmmLabel (mkRtsCodeLabel SLIT("resumeThread")))
261 -- This stuff can't be done in suspendThread/resumeThread, because it
262 -- refers to global registers which aren't available in the C world.
265 -- CurrentTSO->sp = Sp;
266 [CmmStore (cmmOffset stgCurrentTSO tso_SP) stgSp,
268 -- and save the current cost centre stack in the TSO when profiling:
269 if opt_SccProfilingOn
270 then [CmmStore (cmmOffset stgCurrentTSO tso_CCCS) curCCS]
273 -- CurrentNursery->free = Hp+1;
274 closeNursery = CmmStore nursery_bdescr_free (cmmOffsetW stgHp 1)
276 loadThreadState tso_unique =
279 CmmAssign (CmmLocal tso) stgCurrentTSO,
281 CmmAssign sp (CmmLoad (cmmOffset (CmmReg (CmmLocal tso)) tso_SP)
283 -- SpLim = tso->stack + RESERVED_STACK_WORDS;
284 CmmAssign spLim (cmmOffsetW (cmmOffset (CmmReg (CmmLocal tso)) tso_STACK)
285 rESERVED_STACK_WORDS)
288 -- and load the current cost centre stack from the TSO when profiling:
289 if opt_SccProfilingOn
290 then [CmmStore curCCSAddr
291 (CmmLoad (cmmOffset (CmmReg (CmmLocal tso)) tso_CCCS) wordRep)]
293 where tso = LocalReg tso_unique wordRep KindNonPtr -- TODO FIXME NOW
297 -- Hp = CurrentNursery->free - 1;
298 CmmAssign hp (cmmOffsetW (CmmLoad nursery_bdescr_free wordRep) (-1)),
300 -- HpLim = CurrentNursery->start +
301 -- CurrentNursery->blocks*BLOCK_SIZE_W - 1;
304 (CmmLoad nursery_bdescr_start wordRep)
306 (CmmMachOp mo_wordMul [
307 CmmMachOp (MO_S_Conv I32 wordRep)
308 [CmmLoad nursery_bdescr_blocks I32],
309 CmmLit (mkIntCLit bLOCK_SIZE)
317 nursery_bdescr_free = cmmOffset stgCurrentNursery oFFSET_bdescr_free
318 nursery_bdescr_start = cmmOffset stgCurrentNursery oFFSET_bdescr_start
319 nursery_bdescr_blocks = cmmOffset stgCurrentNursery oFFSET_bdescr_blocks
321 tso_SP = tsoFieldB oFFSET_StgTSO_sp
322 tso_STACK = tsoFieldB oFFSET_StgTSO_stack
323 tso_CCCS = tsoProfFieldB oFFSET_StgTSO_CCCS
325 -- The TSO struct has a variable header, and an optional StgTSOProfInfo in
326 -- the middle. The fields we're interested in are after the StgTSOProfInfo.
327 tsoFieldB :: ByteOff -> ByteOff
329 | opt_SccProfilingOn = off + sIZEOF_StgTSOProfInfo + fixedHdrSize * wORD_SIZE
330 | otherwise = off + fixedHdrSize * wORD_SIZE
332 tsoProfFieldB :: ByteOff -> ByteOff
333 tsoProfFieldB off = off + fixedHdrSize * wORD_SIZE
337 stgCurrentTSO = CmmReg currentTSO
338 stgCurrentNursery = CmmReg currentNursery
341 spLim = CmmGlobal SpLim
343 hpLim = CmmGlobal HpLim
344 currentTSO = CmmGlobal CurrentTSO
345 currentNursery = CmmGlobal CurrentNursery
347 -----------------------------------------------------------------------------
348 -- Functions that generate CmmStmt sequences
349 -- for packing/unpacking continuations
350 -- and entering/exiting functions
352 tail_call :: WordOff -> CmmExpr -> CmmActuals -> [CmmStmt]
353 tail_call spRel target arguments
354 = store_arguments ++ adjust_sp_reg spRel ++ jump where
356 [stack_put spRel expr offset
357 | ((expr, _), StackParam offset) <- argument_formats] ++
358 [global_put expr global
359 | ((expr, _), RegisterParam global) <- argument_formats]
360 jump = [CmmJump target arguments]
362 argument_formats = assignArguments (cmmExprRep . fst) arguments
364 adjust_sp_reg spRel =
367 else [CmmAssign spReg (CmmRegOff spReg (spRel*wORD_SIZE))]
369 gc_stack_check' stack_use arg_stack max_frame_size =
370 if max_frame_size > arg_stack
371 then [CmmAssign stack_use (CmmRegOff spReg (-max_frame_size*wORD_SIZE))]
372 else [CmmAssign stack_use (CmmReg spLimReg)]
373 -- Trick the optimizer into eliminating the branch for us
375 gc_stack_check :: BlockId -> WordOff -> [CmmStmt]
376 gc_stack_check gc_block max_frame_size
377 = check_stack_limit where
378 check_stack_limit = [
380 (CmmMachOp (MO_U_Lt $ cmmRegRep spReg)
381 [CmmRegOff spReg (-max_frame_size*wORD_SIZE),
386 pack_continuation :: Bool -- ^ Whether to set the top/header
387 -- of the stack. We only need to
388 -- set it if we are calling down
389 -- as opposed to continuation
391 -> ContinuationFormat -- ^ The current format
392 -> ContinuationFormat -- ^ The return point format
394 pack_continuation allow_header_set
395 (ContinuationFormat _ curr_id curr_frame_size _)
396 (ContinuationFormat _ cont_id cont_frame_size live_regs)
397 = pack_frame curr_frame_size cont_frame_size maybe_header continuation_args
399 continuation_function = CmmLit $ CmmLabel $ fromJust cont_id
400 continuation_args = map (maybe Nothing (Just . CmmReg . CmmLocal))
403 case (curr_id, cont_id) of
404 (Just x, Just y) -> x /= y
407 maybe_header = if allow_header_set && needs_header_set
408 then Just continuation_function
411 pack_frame :: WordOff -- ^ Current frame size
412 -> WordOff -- ^ Next frame size
413 -> Maybe CmmExpr -- ^ Next frame header if any
414 -> [Maybe CmmExpr] -- ^ Next frame data
416 pack_frame curr_frame_size next_frame_size next_frame_header frame_args =
417 store_live_values ++ set_stack_header
419 -- TODO: only save variables when actually needed
420 -- (may be handled by latter pass)
422 [stack_put spRel expr offset
423 | (expr, offset) <- cont_offsets]
425 case next_frame_header of
427 Just expr -> [stack_put spRel expr 0]
429 -- TODO: factor with function_entry and CmmInfo.hs(?)
430 cont_offsets = mkOffsets label_size frame_args
432 label_size = 1 :: WordOff
434 mkOffsets size [] = []
435 mkOffsets size (Nothing:exprs) = mkOffsets (size+1) exprs
436 mkOffsets size (Just expr:exprs) = (expr, size):mkOffsets (size + width) exprs
438 width = machRepByteWidth (cmmExprRep expr) `quot` wORD_SIZE
439 -- TODO: it would be better if we had a machRepWordWidth
441 spRel = curr_frame_size - next_frame_size
444 -- Lazy adjustment of stack headers assumes all blocks
445 -- that could branch to eachother (i.e. control blocks)
446 -- have the same stack format (this causes a problem
447 -- only for proc-point).
448 function_entry :: ContinuationFormat -> [CmmStmt]
449 function_entry (ContinuationFormat formals _ _ live_regs)
450 = load_live_values ++ load_args where
451 -- TODO: only save variables when actually needed
452 -- (may be handled by latter pass)
454 [stack_get 0 reg offset
455 | (reg, offset) <- curr_offsets]
457 [stack_get 0 reg offset
458 | (reg, StackParam offset) <- argument_formats] ++
459 [global_get reg global
460 | (reg, RegisterParam global) <- argument_formats]
462 argument_formats = assignArguments (localRegRep) formals
464 -- TODO: eliminate copy/paste with pack_continuation
465 curr_offsets = mkOffsets label_size live_regs
467 label_size = 1 :: WordOff
469 mkOffsets size [] = []
470 mkOffsets size (Nothing:regs) = mkOffsets (size+1) regs
471 mkOffsets size (Just reg:regs) = (reg, size):mkOffsets (size + width) regs
473 width = machRepByteWidth (localRegRep reg) `quot` wORD_SIZE
474 -- TODO: it would be better if we had a machRepWordWidth
476 -----------------------------------------------------------------------------
477 -- Section: Stack and argument register puts and gets
478 -----------------------------------------------------------------------------
481 -- |Construct a 'CmmStmt' that will save a value on the stack
482 stack_put :: WordOff -- ^ Offset from the real 'Sp' that 'offset'
483 -- is relative to (added to offset)
484 -> CmmExpr -- ^ What to store onto the stack
485 -> WordOff -- ^ Where on the stack to store it
486 -- (positive <=> higher addresses)
488 stack_put spRel expr offset =
489 CmmStore (CmmRegOff spReg (wORD_SIZE*(spRel + offset))) expr
491 --------------------------------
497 stack_get spRel reg offset =
498 CmmAssign (CmmLocal reg)
499 (CmmLoad (CmmRegOff spReg (wORD_SIZE*(spRel + offset)))
501 global_put :: CmmExpr -> GlobalReg -> CmmStmt
502 global_put expr global = CmmAssign (CmmGlobal global) expr
503 global_get :: LocalReg -> GlobalReg -> CmmStmt
504 global_get reg global = CmmAssign (CmmLocal reg) (CmmReg (CmmGlobal global))