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
32 -- The format for the call to a continuation
33 -- The fst is the arguments that must be passed to the continuation
34 -- by the continuation's caller.
35 -- The snd is the live values that must be saved on stack.
36 -- A Nothing indicates an ignored slot.
37 -- The head of each list is the stack top or the first parameter.
39 -- The format for live values for a particular continuation
40 -- All on stack for now.
41 -- Head element is the top of the stack (or just under the header).
42 -- Nothing means an empty slot.
43 -- Future possibilities include callee save registers (i.e. passing slots in register)
44 -- and heap memory (not sure if that's usefull at all though, but it may
45 -- be worth exploring the design space).
47 continuationLabel (Continuation _ l _ _ _) = l
48 data Continuation info =
50 info -- Left <=> Continuation created by the CPS
51 -- Right <=> Function or Proc point
52 CLabel -- Used to generate both info & entry labels
53 CmmFormals -- Argument locals live on entry (C-- procedure params)
54 Bool -- ^ True <=> GC block so ignore stack size
55 [BrokenBlock] -- Code, may be empty. The first block is
56 -- the entry point. The order is otherwise initially
57 -- unimportant, but at some point the code gen will
60 -- the BlockId of the first block does not give rise
61 -- to a label. To jump to the first block in a Proc,
62 -- use the appropriate CLabel.
64 data ContinuationFormat
65 = ContinuationFormat {
66 continuation_formals :: CmmFormals,
67 continuation_label :: Maybe CLabel, -- The label occupying the top slot
68 continuation_frame_size :: WordOff, -- Total frame size in words (not including arguments)
69 continuation_stack :: [Maybe LocalReg] -- local reg offsets from stack top
72 -- A block can be a continuation of a call
73 -- A block can be a continuation of another block (w/ or w/o joins)
74 -- A block can be an entry to a function
76 -----------------------------------------------------------------------------
77 continuationToProc :: (WordOff, WordOff, [(CLabel, ContinuationFormat)])
80 -> Continuation CmmInfo
82 continuationToProc (max_stack, update_frame_size, formats) stack_use uniques
83 (Continuation info label formals _ blocks) =
84 CmmProc info label formals (concat $ zipWith3 continuationToProc' uniques blocks (True : repeat False))
86 curr_format = maybe unknown_block id $ lookup label formats
87 unknown_block = panic "unknown BlockId in continuationToProc"
88 curr_stack = continuation_frame_size curr_format
89 arg_stack = argumentsSize localRegRep formals
91 param_stmts :: [CmmStmt]
92 param_stmts = function_entry curr_format
96 assign_gc_stack_use stack_use arg_stack (max_stack - curr_stack)
98 update_stmts :: [CmmStmt]
101 CmmInfo _ (Just (UpdateFrame target args)) _ ->
102 pack_frame curr_stack update_frame_size (Just target) (map Just args) ++
103 adjust_sp_reg (curr_stack - update_frame_size)
104 CmmInfo _ Nothing _ -> []
106 continuationToProc' :: [[Unique]]
110 continuationToProc' uniques (BrokenBlock ident entry stmts _ exit) is_entry =
111 prefix_blocks ++ [BasicBlock ident fixed_main_stmts] ++ concat new_blocks
116 (BlockId prefix_unique)
117 (param_stmts ++ [CmmBranch ident])]
120 (prefix_unique : call_uniques) : new_block_uniques = uniques
121 toCLabel = mkReturnPtLabel . getUnique
123 block_for_branch :: Unique -> BlockId -> (BlockId, [CmmBasicBlock])
124 block_for_branch unique next
125 -- branches to the current function don't have to jump
126 | (mkReturnPtLabel $ getUnique next) == label
129 -- branches to any other function have to jump
130 | (Just cont_format) <- lookup (toCLabel next) formats
132 new_next = BlockId unique
133 cont_stack = continuation_frame_size cont_format
134 arguments = map formal_to_actual (continuation_formals cont_format)
136 [BasicBlock new_next $
137 pack_continuation curr_format cont_format ++
138 tail_call (curr_stack - cont_stack)
139 (CmmLit $ CmmLabel $ toCLabel next)
142 -- branches to blocks in the current function don't have to jump
146 -- Wrapper for block_for_branch for when the target
147 -- is inside a 'Maybe'.
148 block_for_branch' :: Unique -> Maybe BlockId -> (Maybe BlockId, [CmmBasicBlock])
149 block_for_branch' _ Nothing = (Nothing, [])
150 block_for_branch' unique (Just next) = (Just new_next, new_blocks)
151 where (new_next, new_blocks) = block_for_branch unique next
153 -- If the target of a switch, branch or cond branch becomes a proc point
154 -- then we have to make a new block what will then *jump* to the original target.
155 proc_point_fix unique (CmmCondBranch test target)
156 = (CmmCondBranch test new_target, new_blocks)
157 where (new_target, new_blocks) = block_for_branch (head unique) target
158 proc_point_fix unique (CmmSwitch test targets)
159 = (CmmSwitch test new_targets, concat new_blocks)
160 where (new_targets, new_blocks) =
161 unzip $ zipWith block_for_branch' unique targets
162 proc_point_fix unique (CmmBranch target)
163 = (CmmBranch new_target, new_blocks)
164 where (new_target, new_blocks) = block_for_branch (head unique) target
165 proc_point_fix _ other = (other, [])
167 (fixed_main_stmts, new_blocks) = unzip $ zipWith proc_point_fix new_block_uniques main_stmts
170 FunctionEntry _ _ _ ->
171 -- Ugh, the statements for an update frame must come
172 -- *after* the GC check that was added at the beginning
173 -- of the CPS pass. So we have do edit the statements
174 -- a bit. This depends on the knowledge that the
175 -- statements in the first block are only the GC check.
176 -- That's fragile but it works for now.
177 gc_stmts ++ stmts ++ update_stmts ++ postfix_stmts
178 ControlEntry -> stmts ++ postfix_stmts
179 ContinuationEntry _ _ _ -> stmts ++ postfix_stmts
180 postfix_stmts = case exit of
181 -- Branches and switches may get modified by proc_point_fix
182 FinalBranch next -> [CmmBranch next]
183 FinalSwitch expr targets -> [CmmSwitch expr targets]
185 -- A return is a tail call to the stack top
186 FinalReturn arguments ->
188 (entryCode (CmmLoad (CmmReg spReg) wordRep))
192 FinalJump target arguments ->
193 tail_call curr_stack target arguments
195 -- A regular Cmm function call
196 FinalCall next (CmmCallee target CmmCallConv)
197 results arguments _ _ ->
198 pack_continuation curr_format cont_format ++
199 tail_call (curr_stack - cont_stack)
202 cont_format = maybe unknown_block id $
203 lookup (mkReturnPtLabel $ getUnique next) formats
204 cont_stack = continuation_frame_size cont_format
206 -- A safe foreign call
207 FinalCall next (CmmCallee target conv)
208 results arguments _ _ ->
210 foreignCall call_uniques' (CmmCallee new_target conv)
213 (call_uniques', target_stmts, new_target) =
214 maybeAssignTemp call_uniques target
217 FinalCall next (CmmPrim target)
218 results arguments _ _ ->
219 foreignCall call_uniques (CmmPrim target)
222 formal_to_actual reg = (CmmReg (CmmLocal reg), NoHint)
224 foreignCall :: [Unique] -> CmmCallTarget -> CmmHintFormals -> CmmActuals -> [CmmStmt]
225 foreignCall uniques call results arguments =
229 [CmmCall (CmmCallee suspendThread CCallConv)
231 [ (CmmReg (CmmGlobal BaseReg), PtrHint) ]
233 CmmCall call results new_args CmmUnsafe,
234 CmmCall (CmmCallee resumeThread CCallConv)
235 [ (new_base, PtrHint) ]
236 [ (CmmReg (CmmLocal id), PtrHint) ]
238 -- Assign the result to BaseReg: we
239 -- might now have a different Capability!
240 CmmAssign (CmmGlobal BaseReg) (CmmReg (CmmLocal new_base))] ++
242 loadThreadState tso_unique ++
243 [CmmJump (CmmReg spReg) (map (formal_to_actual . fst) results)]
245 (_, arg_stmts, new_args) =
246 loadArgsIntoTemps argument_uniques arguments
247 (caller_save, caller_load) =
248 callerSaveVolatileRegs (Just [{-only system regs-}])
249 new_base = LocalReg base_unique (cmmRegRep (CmmGlobal BaseReg)) KindNonPtr
250 id = LocalReg id_unique wordRep KindNonPtr
251 tso_unique : base_unique : id_unique : argument_uniques = uniques
253 -- -----------------------------------------------------------------------------
254 -- Save/restore the thread state in the TSO
256 suspendThread = CmmLit (CmmLabel (mkRtsCodeLabel SLIT("suspendThread")))
257 resumeThread = CmmLit (CmmLabel (mkRtsCodeLabel SLIT("resumeThread")))
259 -- This stuff can't be done in suspendThread/resumeThread, because it
260 -- refers to global registers which aren't available in the C world.
263 -- CurrentTSO->sp = Sp;
264 [CmmStore (cmmOffset stgCurrentTSO tso_SP) stgSp,
266 -- and save the current cost centre stack in the TSO when profiling:
267 if opt_SccProfilingOn
268 then [CmmStore (cmmOffset stgCurrentTSO tso_CCCS) curCCS]
271 -- CurrentNursery->free = Hp+1;
272 closeNursery = CmmStore nursery_bdescr_free (cmmOffsetW stgHp 1)
274 loadThreadState tso_unique =
277 CmmAssign (CmmLocal tso) stgCurrentTSO,
279 CmmAssign sp (CmmLoad (cmmOffset (CmmReg (CmmLocal tso)) tso_SP)
281 -- SpLim = tso->stack + RESERVED_STACK_WORDS;
282 CmmAssign spLim (cmmOffsetW (cmmOffset (CmmReg (CmmLocal tso)) tso_STACK)
283 rESERVED_STACK_WORDS)
286 -- and load the current cost centre stack from the TSO when profiling:
287 if opt_SccProfilingOn
288 then [CmmStore curCCSAddr
289 (CmmLoad (cmmOffset (CmmReg (CmmLocal tso)) tso_CCCS) wordRep)]
291 where tso = LocalReg tso_unique wordRep KindNonPtr -- TODO FIXME NOW
295 -- Hp = CurrentNursery->free - 1;
296 CmmAssign hp (cmmOffsetW (CmmLoad nursery_bdescr_free wordRep) (-1)),
298 -- HpLim = CurrentNursery->start +
299 -- CurrentNursery->blocks*BLOCK_SIZE_W - 1;
302 (CmmLoad nursery_bdescr_start wordRep)
304 (CmmMachOp mo_wordMul [
305 CmmMachOp (MO_S_Conv I32 wordRep)
306 [CmmLoad nursery_bdescr_blocks I32],
307 CmmLit (mkIntCLit bLOCK_SIZE)
315 nursery_bdescr_free = cmmOffset stgCurrentNursery oFFSET_bdescr_free
316 nursery_bdescr_start = cmmOffset stgCurrentNursery oFFSET_bdescr_start
317 nursery_bdescr_blocks = cmmOffset stgCurrentNursery oFFSET_bdescr_blocks
319 tso_SP = tsoFieldB oFFSET_StgTSO_sp
320 tso_STACK = tsoFieldB oFFSET_StgTSO_stack
321 tso_CCCS = tsoProfFieldB oFFSET_StgTSO_CCCS
323 -- The TSO struct has a variable header, and an optional StgTSOProfInfo in
324 -- the middle. The fields we're interested in are after the StgTSOProfInfo.
325 tsoFieldB :: ByteOff -> ByteOff
327 | opt_SccProfilingOn = off + sIZEOF_StgTSOProfInfo + fixedHdrSize * wORD_SIZE
328 | otherwise = off + fixedHdrSize * wORD_SIZE
330 tsoProfFieldB :: ByteOff -> ByteOff
331 tsoProfFieldB off = off + fixedHdrSize * wORD_SIZE
335 stgCurrentTSO = CmmReg currentTSO
336 stgCurrentNursery = CmmReg currentNursery
339 spLim = CmmGlobal SpLim
341 hpLim = CmmGlobal HpLim
342 currentTSO = CmmGlobal CurrentTSO
343 currentNursery = CmmGlobal CurrentNursery
345 -----------------------------------------------------------------------------
346 -- Functions that generate CmmStmt sequences
347 -- for packing/unpacking continuations
348 -- and entering/exiting functions
350 tail_call :: WordOff -> CmmExpr -> CmmActuals -> [CmmStmt]
351 tail_call spRel target arguments
352 = store_arguments ++ adjust_sp_reg spRel ++ jump where
354 [stack_put spRel expr offset
355 | ((expr, _), StackParam offset) <- argument_formats] ++
356 [global_put expr global
357 | ((expr, _), RegisterParam global) <- argument_formats]
358 jump = [CmmJump target arguments]
360 argument_formats = assignArguments (cmmExprRep . fst) arguments
362 adjust_sp_reg spRel =
365 else [CmmAssign spReg (CmmRegOff spReg (spRel*wORD_SIZE))]
367 assign_gc_stack_use stack_use arg_stack max_frame_size =
368 if max_frame_size > arg_stack
369 then [CmmAssign stack_use (CmmRegOff spReg (-max_frame_size*wORD_SIZE))]
370 else [CmmAssign stack_use (CmmReg spLimReg)]
371 -- Trick the optimizer into eliminating the branch for us
373 gc_stack_check :: BlockId -> WordOff -> [CmmStmt]
374 gc_stack_check gc_block max_frame_size
375 = check_stack_limit where
376 check_stack_limit = [
378 (CmmMachOp (MO_U_Lt $ cmmRegRep spReg)
379 [CmmRegOff spReg (-max_frame_size*wORD_SIZE),
384 pack_continuation :: ContinuationFormat -- ^ The current format
385 -> ContinuationFormat -- ^ The return point format
387 pack_continuation (ContinuationFormat _ curr_id curr_frame_size _)
388 (ContinuationFormat _ cont_id cont_frame_size live_regs)
389 = pack_frame curr_frame_size cont_frame_size maybe_header continuation_args
391 continuation_args = map (maybe Nothing (Just . CmmReg . CmmLocal))
394 case (curr_id, cont_id) of
395 (Just x, Just y) -> x /= y
398 maybe_header = if needs_header_set
399 then maybe Nothing (Just . CmmLit . CmmLabel . entryLblToInfoLbl) cont_id
402 pack_frame :: WordOff -- ^ Current frame size
403 -> WordOff -- ^ Next frame size
404 -> Maybe CmmExpr -- ^ Next frame header if any
405 -> [Maybe CmmExpr] -- ^ Next frame data
407 pack_frame curr_frame_size next_frame_size next_frame_header frame_args =
408 store_live_values ++ set_stack_header
410 -- TODO: only save variables when actually needed
411 -- (may be handled by latter pass)
413 [stack_put spRel expr offset
414 | (expr, offset) <- cont_offsets]
416 case next_frame_header of
418 Just expr -> [stack_put spRel expr 0]
420 -- TODO: factor with function_entry and CmmInfo.hs(?)
421 cont_offsets = mkOffsets label_size frame_args
423 label_size = 1 :: WordOff
425 mkOffsets size [] = []
426 mkOffsets size (Nothing:exprs) = mkOffsets (size+1) exprs
427 mkOffsets size (Just expr:exprs) = (expr, size):mkOffsets (size + width) exprs
429 width = machRepByteWidth (cmmExprRep expr) `quot` wORD_SIZE
430 -- TODO: it would be better if we had a machRepWordWidth
432 spRel = curr_frame_size - next_frame_size
435 -- Lazy adjustment of stack headers assumes all blocks
436 -- that could branch to eachother (i.e. control blocks)
437 -- have the same stack format (this causes a problem
438 -- only for proc-point).
439 function_entry :: ContinuationFormat -> [CmmStmt]
440 function_entry (ContinuationFormat formals _ _ live_regs)
441 = load_live_values ++ load_args where
442 -- TODO: only save variables when actually needed
443 -- (may be handled by latter pass)
445 [stack_get 0 reg offset
446 | (reg, offset) <- curr_offsets]
448 [stack_get 0 reg offset
449 | (reg, StackParam offset) <- argument_formats] ++
450 [global_get reg global
451 | (reg, RegisterParam global) <- argument_formats]
453 argument_formats = assignArguments (localRegRep) formals
455 -- TODO: eliminate copy/paste with pack_continuation
456 curr_offsets = mkOffsets label_size live_regs
458 label_size = 1 :: WordOff
460 mkOffsets size [] = []
461 mkOffsets size (Nothing:regs) = mkOffsets (size+1) regs
462 mkOffsets size (Just reg:regs) = (reg, size):mkOffsets (size + width) regs
464 width = machRepByteWidth (localRegRep reg) `quot` wORD_SIZE
465 -- TODO: it would be better if we had a machRepWordWidth
467 -----------------------------------------------------------------------------
468 -- Section: Stack and argument register puts and gets
469 -----------------------------------------------------------------------------
472 -- |Construct a 'CmmStmt' that will save a value on the stack
473 stack_put :: WordOff -- ^ Offset from the real 'Sp' that 'offset'
474 -- is relative to (added to offset)
475 -> CmmExpr -- ^ What to store onto the stack
476 -> WordOff -- ^ Where on the stack to store it
477 -- (positive <=> higher addresses)
479 stack_put spRel expr offset =
480 CmmStore (CmmRegOff spReg (wORD_SIZE*(spRel + offset))) expr
482 --------------------------------
488 stack_get spRel reg offset =
489 CmmAssign (CmmLocal reg)
490 (CmmLoad (CmmRegOff spReg (wORD_SIZE*(spRel + offset)))
492 global_put :: CmmExpr -> GlobalReg -> CmmStmt
493 global_put expr global = CmmAssign (CmmGlobal global) expr
494 global_get :: LocalReg -> GlobalReg -> CmmStmt
495 global_get reg global = CmmAssign (CmmLocal reg) (CmmReg (CmmGlobal global))