2 -- | Converts C-- with full proceedures and parameters
3 -- to a CPS transformed C-- with the stack made manifest.
7 #include "HsVersions.h"
39 -----------------------------------------------------------------------------
40 -- |Top level driver for the CPS pass
41 -----------------------------------------------------------------------------
42 cmmCPS :: DynFlags -- ^ Dynamic flags: -dcmm-lint -ddump-cps-cmm
43 -> [Cmm] -- ^ Input C-- with Proceedures
44 -> IO [Cmm] -- ^ Output CPS transformed C--
45 cmmCPS dflags cmm_with_calls
46 = do { when (dopt Opt_DoCmmLinting dflags) $
47 do showPass dflags "CmmLint"
48 case firstJust $ map cmmLint cmm_with_calls of
49 Just err -> do printDump err
52 ; showPass dflags "CPS"
54 -- TODO: more lint checking
55 -- check for use of branches to non-existant blocks
56 -- check for use of Sp, SpLim, R1, R2, etc.
58 ; uniqSupply <- mkSplitUniqSupply 'p'
59 ; let supplies = listSplitUniqSupply uniqSupply
60 ; let cpsd_cmm = zipWith doCpsProc supplies cmm_with_calls
62 ; dumpIfSet_dyn dflags Opt_D_dump_cps_cmm "CPS Cmm" (pprCmms cpsd_cmm)
64 -- TODO: add option to dump Cmm to file
69 -----------------------------------------------------------------------------
70 -- |CPS a single CmmTop (proceedure)
71 -- Only 'CmmProc' are transformed 'CmmData' will be left alone.
72 -----------------------------------------------------------------------------
74 doCpsProc :: UniqSupply -> Cmm -> Cmm
76 = Cmm $ concat $ zipWith cpsProc (listSplitUniqSupply s) c
79 -> CmmTop -- ^Input procedure
80 -> [CmmTop] -- ^Output procedures;
81 -- a single input procedure is converted to
82 -- multiple output procedures
84 -- Data blocks don't need to be CPS transformed
85 cpsProc uniqSupply proc@(CmmData _ _) = [proc]
87 -- Empty functions just don't work with the CPS algorithm, but
88 -- they don't need the transformation anyway so just output them directly
89 cpsProc uniqSupply proc@(CmmProc _ _ _ [])
90 = pprTrace "cpsProc: unexpected empty proc" (ppr proc) [proc]
92 -- CPS transform for those procs that actually need it
95 -- * Introduce a stack-check block as the first block
96 -- * The first blocks gets a FunctionEntry; the rest are ControlEntry
97 -- * Now break each block into a bunch of blocks (at call sites);
98 -- all but the first will be ContinuationEntry
100 cpsProc uniqSupply (CmmProc info ident params blocks) = cps_procs
102 -- We need to be generating uniques for several things.
103 -- We could make this function monadic to handle that
104 -- but since there is no other reason to make it monadic,
105 -- we instead will just split them all up right here.
106 (uniqSupply1, uniqSupply2) = splitUniqSupply uniqSupply
107 uniques :: [[Unique]]
108 uniques = map uniqsFromSupply $ listSplitUniqSupply uniqSupply1
109 (stack_check_block_unique:stack_use_unique:adaptor_uniques) :
110 block_uniques = uniques
111 proc_uniques = map (map (map uniqsFromSupply . listSplitUniqSupply) . listSplitUniqSupply) $ listSplitUniqSupply uniqSupply2
113 stack_use = CmmLocal (LocalReg stack_use_unique (cmmRegRep spReg) KindPtr)
114 stack_check_block_id = BlockId stack_check_block_unique
115 stack_check_block = make_stack_check stack_check_block_id info stack_use (blockId $ head blocks)
117 forced_blocks = stack_check_block : blocks
119 CmmInfo maybe_gc_block_id update_frame _ = info
121 -- Break the block at each function call.
122 -- The part after the function call will have to become a continuation.
123 broken_blocks :: ([(BlockId, ContFormat)], [BrokenBlock])
125 (\x -> (concatMap fst x, concatMap snd x)) $
126 zipWith3 (breakBlock (maybeToList maybe_gc_block_id))
129 (FunctionEntry info ident params :
132 f' = selectContinuations (fst broken_blocks)
133 broken_blocks' = map (makeContinuationEntries f') $
135 zipWith (adaptBlockToFormat f')
139 -- Calculate live variables for each broken block.
141 -- Nothing can be live on entry to the first block
142 -- so we could take the tail, but for now we wont
143 -- to help future proof the code.
144 live :: BlockEntryLiveness
145 live = cmmLiveness $ map cmmBlockFromBrokenBlock broken_blocks'
147 -- Calculate which blocks must be made into full fledged procedures.
148 proc_points :: UniqSet BlockId
149 proc_points = calculateProcPoints broken_blocks'
151 -- Construct a map so we can lookup a broken block by its 'BlockId'.
152 block_env :: BlockEnv BrokenBlock
153 block_env = blocksToBlockEnv broken_blocks'
155 -- Group the blocks into continuations based on the set of proc-points.
156 continuations :: [Continuation (Either C_SRT CmmInfo)]
157 continuations = map (gatherBlocksIntoContinuation live proc_points block_env)
158 (uniqSetToList proc_points)
160 -- Select the stack format on entry to each continuation.
161 -- Return the max stack offset and an association list
163 -- This is an association list instead of a UniqFM because
164 -- CLabel's don't have a 'Uniqueable' instance.
165 formats :: [(CLabel, -- key
166 (CmmFormals, -- arguments
167 Maybe CLabel, -- label in top slot
168 [Maybe LocalReg]))] -- slots
169 formats = selectContinuationFormat live continuations
171 -- Do a little meta-processing on the stack formats such as
172 -- getting the individual frame sizes and the maximum frame size
173 formats' :: (WordOff, WordOff, [(CLabel, ContinuationFormat)])
174 formats'@(_, _, format_list) = processFormats formats update_frame continuations
176 -- Update the info table data on the continuations with
177 -- the selected stack formats.
178 continuations' :: [Continuation CmmInfo]
179 continuations' = map (applyContinuationFormat format_list) continuations
181 -- Do the actual CPS transform.
182 cps_procs :: [CmmTop]
183 cps_procs = zipWith (continuationToProc formats' stack_use) proc_uniques continuations'
185 make_stack_check stack_check_block_id info stack_use next_block_id =
186 BasicBlock stack_check_block_id $
187 check_stmts ++ [CmmBranch next_block_id]
191 -- If we are given a stack check handler,
192 -- then great, well check the stack.
193 CmmInfo (Just gc_block) _ _
195 (CmmMachOp (MO_U_Lt $ cmmRegRep spReg)
196 [CmmReg stack_use, CmmReg spLimReg])
198 -- If we aren't given a stack check handler,
199 -- then humph! we just won't check the stack for them.
202 -----------------------------------------------------------------------------
204 collectNonProcPointTargets ::
205 UniqSet BlockId -> BlockEnv BrokenBlock
206 -> UniqSet BlockId -> [BlockId] -> UniqSet BlockId
207 collectNonProcPointTargets proc_points blocks current_targets new_blocks =
208 if sizeUniqSet current_targets == sizeUniqSet new_targets
211 (collectNonProcPointTargets proc_points blocks)
215 blocks' = map (lookupWithDefaultUFM blocks (panic "TODO")) new_blocks
217 -- Note the subtlety that since the extra branch after a call
218 -- will always be to a block that is a proc-point,
219 -- this subtraction will always remove that case
220 uniqSetToList $ (unionManyUniqSets $ map (mkUniqSet . brokenBlockTargets) blocks')
221 `minusUniqSet` proc_points
222 -- TODO: remove redundant uniqSetToList
223 new_targets = current_targets `unionUniqSets` (mkUniqSet targets)
225 -- TODO: insert proc point code here
226 -- * Branches and switches to proc points may cause new blocks to be created
227 -- (or proc points could leave behind phantom blocks that just jump to them)
228 -- * Proc points might get some live variables passed as arguments
230 gatherBlocksIntoContinuation ::
231 BlockEntryLiveness -> UniqSet BlockId -> BlockEnv BrokenBlock
232 -> BlockId -> Continuation (Either C_SRT CmmInfo)
233 gatherBlocksIntoContinuation live proc_points blocks start =
234 Continuation info_table clabel params is_gc_cont body
236 children = (collectNonProcPointTargets proc_points blocks (unitUniqSet start) [start]) `minusUniqSet` (unitUniqSet start)
237 start_block = lookupWithDefaultUFM blocks unknown_block start
238 children_blocks = map (lookupWithDefaultUFM blocks unknown_block) (uniqSetToList children)
239 unknown_block = panic "unknown block in gatherBlocksIntoContinuation"
240 body = start_block : children_blocks
242 -- We can't properly annotate the continuation's stack parameters
243 -- at this point because this is before stack selection
244 -- but we want to keep the C_SRT around so we use 'Either'.
245 info_table = case start_block_entry of
246 FunctionEntry info _ _ -> Right info
247 ContinuationEntry _ srt _ -> Left srt
248 ControlEntry -> Right (CmmInfo Nothing Nothing CmmNonInfoTable)
250 is_gc_cont = case start_block_entry of
251 FunctionEntry _ _ _ -> False
252 ContinuationEntry _ _ gc_cont -> gc_cont
253 ControlEntry -> False
255 start_block_entry = brokenBlockEntry start_block
256 clabel = case start_block_entry of
257 FunctionEntry _ label _ -> label
258 _ -> mkReturnPtLabel $ getUnique start
259 params = case start_block_entry of
260 FunctionEntry _ _ args -> args
261 ContinuationEntry args _ _ -> args
264 lookupWithDefaultUFM live unknown_block start
265 -- it's a proc-point, pass lives in parameter registers
267 --------------------------------------------------------------------------------
268 -- For now just select the continuation orders in the order they are in the set with no gaps
270 selectContinuationFormat :: BlockEnv CmmLive
271 -> [Continuation (Either C_SRT CmmInfo)]
272 -> [(CLabel, (CmmFormals, Maybe CLabel, [Maybe LocalReg]))]
273 selectContinuationFormat live continuations =
274 map (\c -> (continuationLabel c, selectContinuationFormat' c)) continuations
276 -- User written continuations
277 selectContinuationFormat' (Continuation
278 (Right (CmmInfo _ _ (CmmInfoTable _ _ (ContInfo format srt))))
280 (formals, Just label, format)
281 -- Either user written non-continuation code
282 -- or CPS generated proc-points
283 selectContinuationFormat' (Continuation (Right _) _ formals _ _) =
284 (formals, Nothing, [])
285 -- CPS generated continuations
286 selectContinuationFormat' (Continuation (Left srt) label formals _ blocks) =
287 -- TODO: assumes the first block is the entry block
288 let ident = brokenBlockId $ head blocks -- TODO: CLabel isn't a uniquable, but we need a better way than this
291 map Just $ uniqSetToList $
292 lookupWithDefaultUFM live unknown_block ident)
294 unknown_block = panic "unknown BlockId in selectContinuationFormat"
296 processFormats :: [(CLabel, (CmmFormals, Maybe CLabel, [Maybe LocalReg]))]
298 -> [Continuation (Either C_SRT CmmInfo)]
299 -> (WordOff, WordOff, [(CLabel, ContinuationFormat)])
300 processFormats formats update_frame continuations =
301 (max_size + update_frame_size, update_frame_size, formats')
304 0 : map (continuationMaxStack formats') continuations
305 formats' = map make_format formats
306 make_format (label, (formals, top, stack)) =
309 continuation_formals = formals,
310 continuation_label = top,
311 continuation_frame_size = stack_size stack +
315 continuation_stack = stack })
317 update_frame_size = case update_frame of
319 (Just (UpdateFrame _ args))
320 -> label_size + update_size args
323 update_size (expr:exprs) = width + update_size exprs
325 width = machRepByteWidth (cmmExprRep expr) `quot` wORD_SIZE
326 -- TODO: it would be better if we had a machRepWordWidth
328 -- TODO: get rid of "+ 1" etc.
329 label_size = 1 :: WordOff
332 stack_size (Nothing:formats) = 1 + stack_size formats -- one dead word
333 stack_size (Just reg:formats) = width + stack_size formats
335 width = machRepByteWidth (localRegRep reg) `quot` wORD_SIZE
336 -- TODO: it would be better if we had a machRepWordWidth
338 continuationMaxStack :: [(CLabel, ContinuationFormat)]
341 continuationMaxStack _ (Continuation _ _ _ True _) = 0
342 continuationMaxStack formats (Continuation _ label _ False blocks) =
343 max_arg_size + continuation_frame_size stack_format
345 stack_format = maybe unknown_format id $ lookup label formats
346 unknown_format = panic "Unknown format in continuationMaxStack"
348 max_arg_size = maximum $ 0 : map block_max_arg_size blocks
350 block_max_arg_size block =
351 maximum (final_arg_size (brokenBlockExit block) :
352 map stmt_arg_size (brokenBlockStmts block))
354 final_arg_size (FinalReturn args) =
355 argumentsSize (cmmExprRep . fst) args
356 final_arg_size (FinalJump _ args) =
357 argumentsSize (cmmExprRep . fst) args
358 final_arg_size (FinalCall next _ _ args _ _ True) = 0
359 final_arg_size (FinalCall next _ _ args _ _ False) =
360 -- We have to account for the stack used when we build a frame
361 -- for the *next* continuation from *this* continuation
362 argumentsSize (cmmExprRep . fst) args +
363 continuation_frame_size next_format
365 next_format = maybe unknown_format id $ lookup next' formats
366 next' = mkReturnPtLabel $ getUnique next
370 stmt_arg_size (CmmJump _ args) =
371 argumentsSize (cmmExprRep . fst) args
372 stmt_arg_size (CmmCall _ _ _ (CmmSafe _) _) =
373 panic "Safe call in processFormats"
374 stmt_arg_size (CmmReturn _) =
375 panic "CmmReturn in processFormats"
378 -----------------------------------------------------------------------------
379 applyContinuationFormat :: [(CLabel, ContinuationFormat)]
380 -> Continuation (Either C_SRT CmmInfo)
381 -> Continuation CmmInfo
383 -- User written continuations
384 applyContinuationFormat formats (Continuation
385 (Right (CmmInfo gc update_frame (CmmInfoTable prof tag (ContInfo _ srt))))
386 label formals is_gc blocks) =
387 Continuation (CmmInfo gc update_frame (CmmInfoTable prof tag (ContInfo format srt)))
388 label formals is_gc blocks
390 format = continuation_stack $ maybe unknown_block id $ lookup label formats
391 unknown_block = panic "unknown BlockId in applyContinuationFormat"
393 -- Either user written non-continuation code or CPS generated proc-point
394 applyContinuationFormat formats (Continuation
395 (Right info) label formals is_gc blocks) =
396 Continuation info label formals is_gc blocks
398 -- CPS generated continuations
399 applyContinuationFormat formats (Continuation
400 (Left srt) label formals is_gc blocks) =
401 Continuation (CmmInfo gc Nothing (CmmInfoTable prof tag (ContInfo (continuation_stack $ format) srt)))
402 label formals is_gc blocks
404 gc = Nothing -- Generated continuations never need a stack check
405 -- TODO prof: this is the same as the current implementation
406 -- but I think it could be improved
407 prof = ProfilingInfo zeroCLit zeroCLit
408 tag = rET_SMALL -- cmmToRawCmm may convert it to rET_BIG
409 format = maybe unknown_block id $ lookup label formats
410 unknown_block = panic "unknown BlockId in applyContinuationFormat"