1 {-# LANGUAGE ScopedTypeVariables #-}
3 ( -- These data types and names are carefully thought out
4 BlockId(..) -- ToDo: BlockId should be abstract, but it isn't yet
5 , BlockEnv, emptyBlockEnv, lookupBlockEnv, extendBlockEnv, insertBlock, mkBlockEnv
6 , BlockSet, emptyBlockSet, elemBlockSet, extendBlockSet, mkBlockSet
7 , Graph(..), LGraph(..), FGraph(..)
8 , Block(..), ZBlock(..), ZHead(..), ZTail(..), ZLast(..)
9 , HavingSuccessors, succs, fold_succs
10 , LastNode, mkBranchNode, isBranchNode, branchNodeTarget
12 -- Observers and transformers
13 -- (open to renaming suggestions here)
14 , blockId, zip, unzip, last, goto_end, zipht, tailOfLast
15 , splice_tail, splice_head, splice_head_only', splice_head'
16 , of_block_list, to_block_list
18 , postorder_dfs, postorder_dfs_from, postorder_dfs_from_except
25 , entry -- exported for the convenience of ZipDataflow, at least for now
28 -- the following functions might one day be useful and can be found
29 -- either below or in ZipCfgExtras:
30 , entry, exit, focus, focusp, unfocus
31 , ht_to_block, ht_to_last,
32 , splice_focus_entry, splice_focus_exit
33 , fold_fwd_block, foldM_fwd_block
39 #include "HsVersions.h"
41 import Outputable hiding (empty)
48 import Prelude hiding (zip, unzip, last)
50 -------------------------------------------------------------------------
51 -- GENERIC ZIPPER-BASED CONTROL-FLOW GRAPH --
52 -------------------------------------------------------------------------
55 This module defines datatypes used to represent control-flow graphs,
56 along with some functions for analyzing and splicing graphs.
57 Functions for building graphs are found in a separate module 'MkZipCfg'.
59 Every graph has a distinguished entry point. A graph has at least one
60 exit; most exits are instructions (or statements) like 'jump' or
61 'return', which transfer control to other procedures, but a graph may
62 have up to one 'fall through' exit. (A graph that represents an
63 entire Haskell or C-- procedure does not have a 'fall through' exit.)
65 A graph is a collection of basic blocks. A basic block begins with a
66 label (unique id; see Note [Unique BlockId]) which is followed by a
67 sequence of zero or more 'middle' nodes; the basic block ends with a
68 'last' node. Each 'middle' node is a single-entry, single-exit,
69 uninterruptible computation. A 'last' node is a single-entry,
70 multiple-exit computation. A last node may have zero or more successors,
71 which are identified by their unique ids.
73 A special case of last node is the ``default exit,'' which represents
74 'falling off the end' of the graph. Such a node is always represented by
75 the data constructor 'LastExit'. A graph may contain at most one
76 'LastExit' node, and a graph representing a full procedure should not
77 contain any 'LastExit' nodes. 'LastExit' nodes are used only to splice
78 graphs together, either during graph construction (see module 'MkZipCfg')
79 or during optimization (see module 'ZipDataflow').
81 A graph is parameterized over the types of middle and last nodes. Each of
82 these types will typically be instantiated with a subset of C-- statements
83 (see module 'ZipCfgCmmRep') or a subset of machine instructions (yet to be
84 implemented as of August 2007).
87 Note [Kinds of Graphs]
88 ~~~~~~~~~~~~~~~~~~~~~~
89 This module exposes three representations of graphs. In order of
90 increasing complexity, they are:
92 Graph m l The basic graph with its distinguished entry point
94 LGraph m l A graph with a *labelled* entry point
96 FGraph m l A labelled graph with the *focus* on a particular edge
98 There are three types because each type offers a slightly different
99 invariant or cost model.
101 * The distinguished entry of a Graph has no label. Because labels must be
102 unique, acquiring one requires a supply of Unique labels (BlockId's).
103 The primary advantage of the Graph representation is that we can build a
104 small Graph purely functionally, without needing a fresh BlockId or
105 Unique. For example, during optimization we can easily rewrite a single
106 middle node into a Graph containing a sequence of two middle nodes
107 followed by LastExit.
109 * In an LGraph, every basic block is labelled. The primary advantage of
110 this representation is its simplicity: each basic block can be treated
111 like any other. This representation is used for mapping, folding, and
112 translation, as well as layout.
114 Like any graph, an LGraph still has a distinguished entry point,
115 which you can discover using 'lg_entry'.
117 * An FGraph is an LGraph with the *focus* on one particular edge. The
118 primary advantage of this representation is that it provides
119 constant-time access to the nodes connected by that edge, and it also
120 allows constant-time, functional *replacement* of those nodes---in the
121 style of Huet's 'zipper'.
123 None of these representations is ideally suited to the incremental
124 construction of large graphs. A separate module, 'MkZipCfg', provides a
125 fourth representation that is asymptotically optimal for such construction.
129 --------------- Representation --------------------
131 -- | A basic block is a 'first' node, followed by zero or more 'middle'
132 -- nodes, followed by a 'last' node.
134 -- eventually this module should probably replace the original Cmm, but for
135 -- now we leave it to dynamic invariants what can be found where
138 = LastExit -- fall through; used for the block that has no last node
139 -- LastExit is a device used only for graphs under
140 -- construction, or framgments of graph under optimisation,
141 -- so we don't want to pollute the 'l' type parameter with it
144 data ZHead m = ZFirst BlockId | ZHead (ZHead m) m
145 -- ZHead is a (reversed) sequence of middle nodes labeled by a BlockId
146 data ZTail m l = ZLast (ZLast l) | ZTail m (ZTail m l)
147 -- ZTail is a sequence of middle nodes followed by a last node
149 -- | Blocks and flow graphs; see Note [Kinds of graphs]
150 data Block m l = Block BlockId (ZTail m l)
152 data Graph m l = Graph { g_entry :: (ZTail m l), g_blocks :: (BlockEnv (Block m l)) }
154 data LGraph m l = LGraph { lg_entry :: BlockId
155 , lg_blocks :: BlockEnv (Block m l) }
156 -- Invariant: lg_entry is in domain( lg_blocks )
158 -- | And now the zipper. The focus is between the head and tail.
159 -- We cannot ever focus on an inter-block edge.
160 data ZBlock m l = ZBlock (ZHead m) (ZTail m l)
161 data FGraph m l = FGraph { fg_entry :: BlockId
162 , fg_focus :: ZBlock m l
163 , fg_others :: BlockEnv (Block m l) }
164 -- Invariant: the block represented by 'fg_focus' is *not*
165 -- in the map 'fg_others'
167 ---- Utility functions ---
169 blockId :: Block m l -> BlockId
170 zip :: ZBlock m l -> Block m l
171 unzip :: Block m l -> ZBlock m l
173 last :: ZBlock m l -> ZLast l
174 goto_end :: ZBlock m l -> (ZHead m, ZLast l)
176 tailOfLast :: l -> ZTail m l
178 -- | Take a head and tail and go to beginning or end. The asymmetry
179 -- in the types and names is a bit unfortunate, but 'Block m l' is
180 -- effectively '(BlockId, ZTail m l)' and is accepted in many more places.
182 ht_to_block, zipht :: ZHead m -> ZTail m l -> Block m l
183 ht_to_last :: ZHead m -> ZTail m l -> (ZHead m, ZLast l)
185 -- | We can splice a single-entry, single-exit LGraph onto a head or a tail.
186 -- For a head, we have a head 'h' followed by a LGraph 'g'.
187 -- The entry node of 'g' gets joined to 'h', forming the entry into
188 -- the new LGraph. The exit of 'g' becomes the new head.
189 -- For both arguments and results, the order of values is the order of
190 -- control flow: before splicing, the head flows into the LGraph; after
191 -- splicing, the LGraph flows into the head.
192 -- Splicing a tail is the dual operation.
193 -- (In order to maintain the order-means-control-flow convention, the
194 -- orders are reversed.)
196 -- For example, assume
198 -- grph = (M, [M: <stuff>,
200 -- N: y:=x; LastExit])
201 -- tail = [return (y,x)]
203 -- Then splice_head head grph
204 -- = ((L, [L: x:=0; goto M,
209 -- Then splice_tail grph tail
211 -- , (???, [<blocks>,
212 -- N: y:=x; return (y,x)])
214 splice_head :: ZHead m -> LGraph m l -> (LGraph m l, ZHead m)
215 splice_head' :: ZHead m -> Graph m l -> (BlockEnv (Block m l), ZHead m)
216 splice_tail :: Graph m l -> ZTail m l -> Graph m l
218 -- | We can also splice a single-entry, no-exit Graph into a head.
219 splice_head_only :: ZHead m -> LGraph m l -> LGraph m l
220 splice_head_only' :: ZHead m -> Graph m l -> LGraph m l
223 -- | A safe operation
225 -- | Conversion to and from the environment form is convenient. For
226 -- layout or dataflow, however, one will want to use 'postorder_dfs'
227 -- in order to get the blocks in an order that relates to the control
228 -- flow in the procedure.
229 of_block_list :: BlockId -> [Block m l] -> LGraph m l -- N log N
230 to_block_list :: LGraph m l -> [Block m l] -- N log N
232 -- | Traversal: 'postorder_dfs' returns a list of blocks reachable
233 -- from the entry node. This list has the following property:
235 -- Say a "back reference" exists if one of a block's
236 -- control-flow successors precedes it in the output list
238 -- Then there are as few back references as possible
240 -- The output is suitable for use in
241 -- a forward dataflow problem. For a backward problem, simply reverse
242 -- the list. ('postorder_dfs' is sufficiently tricky to implement that
243 -- one doesn't want to try and maintain both forward and backward
246 postorder_dfs :: LastNode l => LGraph m l -> [Block m l]
248 -- | For layout, we fold over pairs of 'Block m l' and 'Maybe BlockId'
249 -- in layout order. The 'Maybe BlockId', if present, identifies the
250 -- block that will be the layout successor of the current block. This
251 -- may be useful to help an emitter omit the final 'goto' of a block
252 -- that flows directly to its layout successor.
254 -- For example: fold_layout f z [ L1:B1, L2:B2, L3:B3 ]
255 -- = z <$> f (L1:B1) (Just L2)
256 -- <$> f (L2:B2) (Just L3)
257 -- <$> f (L3:B3) Nothing
258 -- where a <$> f = f a
260 LastNode l => (Block m l -> Maybe BlockId -> a -> a) -> a -> LGraph m l-> a
262 -- | We can also fold over blocks in an unspecified order. The
263 -- 'ZipCfgExtras' module provides a monadic version, which we
264 -- haven't needed (else it would be here).
265 fold_blocks :: (Block m l -> a -> a) -> a -> LGraph m l -> a
267 map_nodes :: (BlockId -> BlockId) -> (m -> m') -> (l -> l') -> LGraph m l -> LGraph m' l'
268 -- mapping includes the entry id!
270 map_blocks :: (Block m l -> Block m' l') -> LGraph m' l' -> LGraph m' l'
272 -- | These translation functions are speculative. I hope eventually
273 -- they will be used in the native-code back ends ---NR
274 translate :: Monad tm =>
275 (m -> tm (LGraph m' l')) ->
276 (l -> tm (LGraph m' l')) ->
277 (LGraph m l -> tm (LGraph m' l'))
280 -- | It's possible that another form of translation would be more suitable:
281 translateA :: (m -> Agraph m' l') -> (l -> AGraph m' l') -> LGraph m l -> LGraph m' l'
284 ------------------- Last nodes
286 -- | We can't make a graph out of just any old 'last node' type. A last node
287 -- has to be able to find its successors, and we need to be able to create and
288 -- identify unconditional branches. We put these capabilities in a type class.
289 -- Moreover, the property of having successors is also shared by 'Block's and
290 -- 'ZTails', so it is useful to have that property in a type class of its own.
292 class HavingSuccessors b where
293 succs :: b -> [BlockId]
294 fold_succs :: (BlockId -> a -> a) -> b -> a -> a
296 fold_succs add l z = foldr add z $ succs l
298 class HavingSuccessors l => LastNode l where
299 mkBranchNode :: BlockId -> l
300 isBranchNode :: l -> Bool
301 branchNodeTarget :: l -> BlockId -- panics if not branch node
302 -- ^ N.B. This interface seems to make for more congenial clients than a
303 -- single function of type 'l -> Maybe BlockId'
305 instance HavingSuccessors l => HavingSuccessors (ZLast l) where
307 succs (LastOther l) = succs l
308 fold_succs _ LastExit z = z
309 fold_succs f (LastOther l) z = fold_succs f l z
311 instance LastNode l => LastNode (ZLast l) where
312 mkBranchNode id = LastOther $ mkBranchNode id
313 isBranchNode LastExit = False
314 isBranchNode (LastOther l) = isBranchNode l
315 branchNodeTarget LastExit = panic "branchNodeTarget LastExit"
316 branchNodeTarget (LastOther l) = branchNodeTarget l
318 instance LastNode l => HavingSuccessors (ZBlock m l) where
319 succs b = succs (last b)
321 instance LastNode l => HavingSuccessors (Block m l) where
322 succs b = succs (unzip b)
324 instance LastNode l => HavingSuccessors (ZTail m l) where
325 succs b = succs (lastTail b)
329 -- ================ IMPLEMENTATION ================--
331 ----- block manipulations
333 blockId (Block id _) = id
335 -- | Convert block between forms.
336 -- These functions are tail-recursive, so we can go as deep as we like
337 -- without fear of stack overflow.
339 ht_to_block head tail = case head of
340 ZFirst id -> Block id tail
341 ZHead h m -> ht_to_block h (ZTail m tail)
343 ht_to_last head (ZLast l) = (head, l)
344 ht_to_last head (ZTail m t) = ht_to_last (ZHead head m) t
346 zipht h t = ht_to_block h t
347 zip (ZBlock h t) = ht_to_block h t
348 goto_end (ZBlock h t) = ht_to_last h t
350 unzip (Block id t) = ZBlock (ZFirst id) t
352 head_id :: ZHead m -> BlockId
353 head_id (ZFirst id) = id
354 head_id (ZHead h _) = head_id h
356 last (ZBlock _ t) = lastTail t
358 lastTail :: ZTail m l -> ZLast l
359 lastTail (ZLast l) = l
360 lastTail (ZTail _ t) = lastTail t
362 tailOfLast l = ZLast (LastOther l) -- ^ tedious to write in every client
365 ------------------ simple graph manipulations
367 focus :: BlockId -> LGraph m l -> FGraph m l -- focus on edge out of node with id
368 focus id (LGraph entry blocks) =
369 case lookupBlockEnv blocks id of
370 Just b -> FGraph entry (unzip b) (delFromUFM blocks id)
371 Nothing -> panic "asked for nonexistent block in flow graph"
373 entry :: LGraph m l -> FGraph m l -- focus on edge out of entry node
374 entry g@(LGraph eid _) = focus eid g
376 -- | pull out a block satisfying the predicate, if any
377 splitp_blocks :: (Block m l -> Bool) -> BlockEnv (Block m l) ->
378 Maybe (Block m l, BlockEnv (Block m l))
379 splitp_blocks p blocks = lift $ foldUFM scan (Nothing, emptyBlockEnv) blocks
380 where scan b (yes, no) =
382 Nothing | p b -> (Just b, no)
383 | otherwise -> (yes, insertBlock b no)
384 Just _ -> (yes, insertBlock b no)
385 lift (Nothing, _) = Nothing
386 lift (Just b, bs) = Just (b, bs)
388 -- | 'insertBlock' should not be used to *replace* an existing block
389 -- but only to insert a new one
390 insertBlock :: Block m l -> BlockEnv (Block m l) -> BlockEnv (Block m l)
392 ASSERT (isNothing $ lookupBlockEnv bs id)
393 extendBlockEnv bs id b
396 -- | Used in assertions; tells if a graph has exactly one exit
397 single_exit :: LGraph l m -> Bool
398 single_exit g = foldUFM check 0 (lg_blocks g) == 1
399 where check block count = case last (unzip block) of
400 LastExit -> count + (1 :: Int)
403 -- | Used in assertions; tells if a graph has exactly one exit
404 single_exitg :: Graph l m -> Bool
405 single_exitg (Graph tail blocks) = foldUFM add (exit_count (lastTail tail)) blocks == 1
406 where add block count = count + exit_count (last (unzip block))
407 exit_count LastExit = 1 :: Int
410 ------------------ graph traversals
412 -- | This is the most important traversal over this data structure. It drops
413 -- unreachable code and puts blocks in an order that is good for solving forward
414 -- dataflow problems quickly. The reverse order is good for solving backward
415 -- dataflow problems quickly. The forward order is also reasonably good for
416 -- emitting instructions, except that it will not usually exploit Forrest
417 -- Baskett's trick of eliminating the unconditional branch from a loop. For
418 -- that you would need a more serious analysis, probably based on dominators, to
419 -- identify loop headers.
421 -- The ubiquity of 'postorder_dfs' is one reason for the ubiquity of the 'LGraph'
422 -- representation, when for most purposes the plain 'Graph' representation is
423 -- more mathematically elegant (but results in more complicated code).
425 -- Here's an easy way to go wrong! Consider
429 -- Then ordinary dfs would give [A,B,D,C] which has a back ref from C to D.
430 -- Better to geot [A,B,C,D]
433 postorder_dfs g@(LGraph _ blockenv) =
434 let FGraph id eblock _ = entry g in
435 zip eblock : postorder_dfs_from_except blockenv eblock (unitUniqSet id)
437 postorder_dfs_from_except :: (HavingSuccessors b, LastNode l)
438 => BlockEnv (Block m l) -> b -> BlockSet -> [Block m l]
439 postorder_dfs_from_except blocks b visited =
440 vchildren (get_children b) (\acc _visited -> acc) [] visited
443 -- Block m l -> ([Block m l] -> BlockSet -> a) -> [Block m l] -> BlockSet -> a
444 vnode block@(Block id _) cont acc visited =
445 if elemBlockSet id visited then
448 let cont' acc visited = cont (block:acc) visited in
449 vchildren (get_children block) cont' acc (extendBlockSet visited id)
450 vchildren bs cont acc visited =
451 let next children acc visited =
452 case children of [] -> cont acc visited
453 (b:bs) -> vnode b (next bs) acc visited
454 in next bs acc visited
455 get_children block = foldl add_id [] (succs block)
456 add_id rst id = case lookupBlockEnv blocks id of
461 :: (HavingSuccessors b, LastNode l) => BlockEnv (Block m l) -> b -> [Block m l]
462 postorder_dfs_from blocks b = postorder_dfs_from_except blocks b emptyBlockSet
466 -- | Slightly more complicated than the usual fold because we want to tell block
467 -- 'b1' what its inline successor is going to be, so that if 'b1' ends with
468 -- 'goto b2', the goto can be omitted.
470 fold_layout f z g@(LGraph eid _) = fold (postorder_dfs g) z
471 where fold blocks z =
472 case blocks of [] -> z
474 b1 : b2 : bs -> fold (b2 : bs) (f b1 (nextlabel b2) z)
475 nextlabel (Block id _) =
476 if id == eid then panic "entry as successor"
479 -- | The rest of the traversals are straightforward
481 map_blocks f (LGraph eid blocks) = LGraph eid (mapUFM f blocks)
483 map_nodes idm middle last (LGraph eid blocks) = LGraph (idm eid) (mapUFM block blocks)
484 where block (Block id t) = Block (idm id) (tail t)
485 tail (ZTail m t) = ZTail (middle m) (tail t)
486 tail (ZLast LastExit) = ZLast LastExit
487 tail (ZLast (LastOther l)) = ZLast (LastOther (last l))
489 fold_blocks f z (LGraph _ blocks) = foldUFM f z blocks
491 of_block_list e blocks = LGraph e $ foldr insertBlock emptyBlockEnv blocks
492 to_block_list (LGraph _ blocks) = eltsUFM blocks
497 -- We want to be able to scrutinize a single-entry, single-exit 'LGraph' for
498 -- splicing purposes. There are two useful cases: the 'LGraph' is a single block
499 -- or it isn't. We use continuation-passing style.
501 prepare_for_splicing ::
502 LGraph m l -> (ZTail m l -> a) -> (ZTail m l -> ZHead m -> BlockEnv (Block m l) -> a)
504 prepare_for_splicing g single multi =
505 let FGraph _ gentry gblocks = entry g
506 ZBlock _ etail = gentry
507 in if isNullUFM gblocks then
509 LastExit -> single etail
510 _ -> panic "bad single block"
512 case splitp_blocks is_exit gblocks of
513 Nothing -> panic "Can't find an exit block"
514 Just (gexit, gblocks) ->
515 let (gh, gl) = goto_end $ unzip gexit in
516 case gl of LastExit -> multi etail gh gblocks
517 _ -> panic "exit is not exit?!"
519 prepare_for_splicing' ::
520 Graph m l -> (ZTail m l -> a) -> (ZTail m l -> ZHead m -> BlockEnv (Block m l) -> a)
522 prepare_for_splicing' (Graph etail gblocks) single multi =
523 if isNullUFM gblocks then
524 case lastTail etail of
525 LastExit -> single etail
526 _ -> panic "bad single block"
528 case splitp_blocks is_exit gblocks of
529 Nothing -> panic "Can't find an exit block"
530 Just (gexit, gblocks) ->
531 let (gh, gl) = goto_end $ unzip gexit in
532 case gl of LastExit -> multi etail gh gblocks
533 _ -> panic "exit is not exit?!"
535 is_exit :: Block m l -> Bool
536 is_exit b = case last (unzip b) of { LastExit -> True; _ -> False }
539 ASSERT (single_exit g) prepare_for_splicing g splice_one_block splice_many_blocks
540 where eid = head_id head
541 splice_one_block tail' =
542 case ht_to_last head tail' of
543 (head, LastExit) -> (LGraph eid emptyBlockEnv, head)
544 _ -> panic "spliced LGraph without exit"
545 splice_many_blocks entry exit others =
546 (LGraph eid (insertBlock (zipht head entry) others), exit)
548 splice_head' head g =
549 ASSERT (single_exitg g) prepare_for_splicing' g splice_one_block splice_many_blocks
550 where splice_one_block tail' =
551 case ht_to_last head tail' of
552 (head, LastExit) -> (emptyBlockEnv, head)
553 _ -> panic "spliced LGraph without exit"
554 splice_many_blocks entry exit others =
555 (insertBlock (zipht head entry) others, exit)
557 -- splice_tail :: Graph m l -> ZTail m l -> Graph m l
559 ASSERT (single_exitg g) prepare_for_splicing' g splice_one_block splice_many_blocks
560 where splice_one_block tail' = Graph (tail' `append_tails` tail) emptyBlockEnv
561 append_tails (ZLast LastExit) tail = tail
562 append_tails (ZLast _) _ = panic "spliced single block without LastExit"
563 append_tails (ZTail m t) tail = ZTail m (append_tails t tail)
564 splice_many_blocks entry exit others =
565 Graph entry (insertBlock (zipht exit tail) others)
569 AS SERT (single_exit g) prepare_for_splicing g splice_one_block splice_many_blocks
570 where splice_one_block tail' = -- return tail' .. tail
571 case ht_to_last (ZFirst (lg_entry g)) tail' of
573 case ht_to_block head' tail of
574 Block id t | id == lg_entry g -> (t, LGraph id emptyBlockEnv)
575 _ -> panic "entry in; garbage out"
576 _ -> panic "spliced single block without Exit"
577 splice_many_blocks entry exit others =
578 (entry, LGraph (lg_entry g) (insertBlock (zipht exit tail) others))
581 splice_head_only head g =
582 let FGraph eid gentry gblocks = entry g
584 ZBlock (ZFirst _) tail -> LGraph eid (insertBlock (zipht head tail) gblocks)
585 _ -> panic "entry not at start of block?!"
587 splice_head_only' head (Graph tail gblocks) =
588 let eblock = zipht head tail in
589 LGraph (blockId eblock) (insertBlock eblock gblocks)
594 translate txm txl (LGraph eid blocks) =
595 do blocks' <- foldUFM txblock (return emptyBlockEnv) blocks
596 return $ LGraph eid blocks'
599 -- Block m l -> tm (BlockEnv (Block m' l')) -> tm (BlockEnv (Block m' l'))
600 txblock (Block id t) expanded =
601 do blocks' <- expanded
602 txtail (ZFirst id) t blocks'
603 -- txtail :: ZHead m' -> ZTail m l -> BlockEnv (Block m' l') ->
604 -- tm (BlockEnv (Block m' l'))
605 txtail h (ZTail m t) blocks' =
607 let (g, h') = splice_head h m'
608 txtail h' t (plusUFM (lg_blocks g) blocks')
609 txtail h (ZLast (LastOther l)) blocks' =
611 return $ plusUFM (lg_blocks (splice_head_only h l')) blocks'
612 txtail h (ZLast LastExit) blocks' =
613 return $ insertBlock (zipht h (ZLast LastExit)) blocks'
615 ----------------------------------------------------------------
616 --- Block Ids, their environments, and their sets
618 {- Note [Unique BlockId]
619 ~~~~~~~~~~~~~~~~~~~~~~~~
620 Although a 'BlockId' is a local label, for reasons of implementation,
621 'BlockId's must be unique within an entire compilation unit. The reason
622 is that each local label is mapped to an assembly-language label, and in
623 most assembly languages allow, a label is visible throughout the enitre
624 compilation unit in which it appears.
627 newtype BlockId = BlockId Unique
630 instance Uniquable BlockId where
631 getUnique (BlockId u) = u
633 instance Show BlockId where
634 show (BlockId u) = show u
636 instance Outputable BlockId where
637 ppr = ppr . getUnique
640 type BlockEnv a = UniqFM {- BlockId -} a
641 emptyBlockEnv :: BlockEnv a
642 emptyBlockEnv = emptyUFM
643 lookupBlockEnv :: BlockEnv a -> BlockId -> Maybe a
644 lookupBlockEnv = lookupUFM
645 extendBlockEnv :: BlockEnv a -> BlockId -> a -> BlockEnv a
646 extendBlockEnv = addToUFM
647 mkBlockEnv :: [(BlockId,a)] -> BlockEnv a
648 mkBlockEnv = listToUFM
650 type BlockSet = UniqSet BlockId
651 emptyBlockSet :: BlockSet
652 emptyBlockSet = emptyUniqSet
653 elemBlockSet :: BlockId -> BlockSet -> Bool
654 elemBlockSet = elementOfUniqSet
655 extendBlockSet :: BlockSet -> BlockId -> BlockSet
656 extendBlockSet = addOneToUniqSet
657 mkBlockSet :: [BlockId] -> BlockSet
658 mkBlockSet = mkUniqSet
660 ----------------------------------------------------------------
662 ----------------------------------------------------------------
664 -- putting this code in PprCmmZ leads to circular imports :-(
666 instance (Outputable m, Outputable l) => Outputable (ZTail m l) where
669 pprTail :: (Outputable m, Outputable l) => ZTail m l -> SDoc
670 pprTail (ZTail m t) = ppr m $$ ppr t
671 pprTail (ZLast LastExit) = text "<exit>"
672 pprTail (ZLast (LastOther l)) = ppr l
674 pprLgraph :: (Outputable m, Outputable l, LastNode l) => LGraph m l -> SDoc
675 pprLgraph g = text "{" $$ nest 2 (vcat $ map pprBlock blocks) $$ text "}"
676 where pprBlock (Block id tail) = ppr id <> colon $$ ppr tail
677 blocks = postorder_dfs g
679 pprGraph :: (Outputable m, Outputable l, LastNode l) => Graph m l -> SDoc
680 pprGraph (Graph tail blockenv) =
681 text "{" $$ nest 2 (ppr tail $$ (vcat $ map pprBlock blocks)) $$ text "}"
682 where pprBlock (Block id tail) = ppr id <> colon $$ ppr tail
683 blocks = postorder_dfs_from blockenv tail
685 _unused :: FS.FastString