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 -- | These translation functions are speculative. I hope eventually
271 -- they will be used in the native-code back ends ---NR
272 translate :: (m -> UniqSM (LGraph m' l')) ->
273 (l -> UniqSM (LGraph m' l')) ->
274 (LGraph m l -> UniqSM (LGraph m' l'))
277 -- | It's possible that another form of translation would be more suitable:
278 translateA :: (m -> Agraph m' l') -> (l -> AGraph m' l') -> LGraph m l -> LGraph m' l'
281 ------------------- Last nodes
283 -- | We can't make a graph out of just any old 'last node' type. A last node
284 -- has to be able to find its successors, and we need to be able to create and
285 -- identify unconditional branches. We put these capabilities in a type class.
286 -- Moreover, the property of having successors is also shared by 'Block's and
287 -- 'ZTails', so it is useful to have that property in a type class of its own.
289 class HavingSuccessors b where
290 succs :: b -> [BlockId]
291 fold_succs :: (BlockId -> a -> a) -> b -> a -> a
293 fold_succs add l z = foldr add z $ succs l
295 class HavingSuccessors l => LastNode l where
296 mkBranchNode :: BlockId -> l
297 isBranchNode :: l -> Bool
298 branchNodeTarget :: l -> BlockId -- panics if not branch node
299 -- ^ N.B. This interface seems to make for more congenial clients than a
300 -- single function of type 'l -> Maybe BlockId'
302 instance HavingSuccessors l => HavingSuccessors (ZLast l) where
304 succs (LastOther l) = succs l
305 fold_succs _ LastExit z = z
306 fold_succs f (LastOther l) z = fold_succs f l z
308 instance LastNode l => LastNode (ZLast l) where
309 mkBranchNode id = LastOther $ mkBranchNode id
310 isBranchNode LastExit = False
311 isBranchNode (LastOther l) = isBranchNode l
312 branchNodeTarget LastExit = panic "branchNodeTarget LastExit"
313 branchNodeTarget (LastOther l) = branchNodeTarget l
315 instance LastNode l => HavingSuccessors (ZBlock m l) where
316 succs b = succs (last b)
318 instance LastNode l => HavingSuccessors (Block m l) where
319 succs b = succs (unzip b)
321 instance LastNode l => HavingSuccessors (ZTail m l) where
322 succs b = succs (lastTail b)
326 -- ================ IMPLEMENTATION ================--
328 ----- block manipulations
330 blockId (Block id _) = id
332 -- | Convert block between forms.
333 -- These functions are tail-recursive, so we can go as deep as we like
334 -- without fear of stack overflow.
336 ht_to_block head tail = case head of
337 ZFirst id -> Block id tail
338 ZHead h m -> ht_to_block h (ZTail m tail)
340 ht_to_last head (ZLast l) = (head, l)
341 ht_to_last head (ZTail m t) = ht_to_last (ZHead head m) t
343 zipht h t = ht_to_block h t
344 zip (ZBlock h t) = ht_to_block h t
345 goto_end (ZBlock h t) = ht_to_last h t
347 unzip (Block id t) = ZBlock (ZFirst id) t
349 head_id :: ZHead m -> BlockId
350 head_id (ZFirst id) = id
351 head_id (ZHead h _) = head_id h
353 last (ZBlock _ t) = lastTail t
355 lastTail :: ZTail m l -> ZLast l
356 lastTail (ZLast l) = l
357 lastTail (ZTail _ t) = lastTail t
359 tailOfLast l = ZLast (LastOther l) -- ^ tedious to write in every client
362 ------------------ simple graph manipulations
364 focus :: BlockId -> LGraph m l -> FGraph m l -- focus on edge out of node with id
365 focus id (LGraph entry blocks) =
366 case lookupBlockEnv blocks id of
367 Just b -> FGraph entry (unzip b) (delFromUFM blocks id)
368 Nothing -> panic "asked for nonexistent block in flow graph"
370 entry :: LGraph m l -> FGraph m l -- focus on edge out of entry node
371 entry g@(LGraph eid _) = focus eid g
373 -- | pull out a block satisfying the predicate, if any
374 splitp_blocks :: (Block m l -> Bool) -> BlockEnv (Block m l) ->
375 Maybe (Block m l, BlockEnv (Block m l))
376 splitp_blocks p blocks = lift $ foldUFM scan (Nothing, emptyBlockEnv) blocks
377 where scan b (yes, no) =
379 Nothing | p b -> (Just b, no)
380 | otherwise -> (yes, insertBlock b no)
381 Just _ -> (yes, insertBlock b no)
382 lift (Nothing, _) = Nothing
383 lift (Just b, bs) = Just (b, bs)
385 -- | 'insertBlock' should not be used to *replace* an existing block
386 -- but only to insert a new one
387 insertBlock :: Block m l -> BlockEnv (Block m l) -> BlockEnv (Block m l)
389 ASSERT (isNothing $ lookupBlockEnv bs id)
390 extendBlockEnv bs id b
393 -- | Used in assertions; tells if a graph has exactly one exit
394 single_exit :: LGraph l m -> Bool
395 single_exit g = foldUFM check 0 (lg_blocks g) == 1
396 where check block count = case last (unzip block) of
397 LastExit -> count + (1 :: Int)
400 -- | Used in assertions; tells if a graph has exactly one exit
401 single_exitg :: Graph l m -> Bool
402 single_exitg (Graph tail blocks) = foldUFM add (exit_count (lastTail tail)) blocks == 1
403 where add block count = count + exit_count (last (unzip block))
404 exit_count LastExit = 1 :: Int
407 ------------------ graph traversals
409 -- | This is the most important traversal over this data structure. It drops
410 -- unreachable code and puts blocks in an order that is good for solving forward
411 -- dataflow problems quickly. The reverse order is good for solving backward
412 -- dataflow problems quickly. The forward order is also reasonably good for
413 -- emitting instructions, except that it will not usually exploit Forrest
414 -- Baskett's trick of eliminating the unconditional branch from a loop. For
415 -- that you would need a more serious analysis, probably based on dominators, to
416 -- identify loop headers.
418 -- The ubiquity of 'postorder_dfs' is one reason for the ubiquity of the 'LGraph'
419 -- representation, when for most purposes the plain 'Graph' representation is
420 -- more mathematically elegant (but results in more complicated code).
422 -- Here's an easy way to go wrong! Consider
426 -- Then ordinary dfs would give [A,B,D,C] which has a back ref from C to D.
427 -- Better to geot [A,B,C,D]
430 postorder_dfs' :: LastNode l => LGraph m l -> [Block m l]
431 postorder_dfs' g@(LGraph _ blocks) =
432 let FGraph _ eblock _ = entry g
433 in vnode (zip eblock) (\acc _visited -> acc) [] emptyBlockSet
436 -- Block m l -> ([Block m l] -> BlockSet -> a) -> [Block m l] -> BlockSet -> a
437 vnode block@(Block id _) cont acc visited =
438 if elemBlockSet id visited then
441 vchildren block (get_children block) cont acc (extendBlockSet visited id)
442 vchildren block bs cont acc visited =
443 let next children acc visited =
444 case children of [] -> cont (block : acc) visited
445 (b:bs) -> vnode b (next bs) acc visited
446 in next bs acc visited
447 get_children block = foldl add_id [] (succs block)
448 add_id rst id = case lookupBlockEnv blocks id of
452 postorder_dfs g@(LGraph _ blockenv) =
453 let FGraph id eblock _ = entry g
455 postorder_dfs_from_except blockenv eblock (unitUniqSet id)
456 dfs2 = postorder_dfs' g
457 -- in ASSERT (map blockId dfs1 == map blockId dfs2) dfs2
458 in if (map blockId dfs1 == map blockId dfs2) then dfs2 else panic "inconsistent DFS"
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
464 postorder_dfs_from_except :: forall b m l . (HavingSuccessors b, LastNode l) => BlockEnv (Block m l) -> b -> BlockSet -> [Block m l]
465 postorder_dfs_from_except blocks b visited =
466 vchildren (get_children b) (\acc _visited -> acc) [] visited
469 -- Block m l -> ([Block m l] -> BlockSet -> a) -> [Block m l] -> BlockSet -> a
470 vnode block@(Block id _) cont acc visited =
471 if elemBlockSet id visited then
474 let cont' acc visited = cont (block:acc) visited in
475 vchildren (get_children block) cont' acc (extendBlockSet visited id)
476 vchildren bs cont acc visited =
477 let next children acc visited =
478 case children of [] -> cont acc visited
479 (b:bs) -> vnode b (next bs) acc visited
480 in next bs acc visited
481 get_children block = foldl add_id [] (succs block)
482 add_id rst id = case lookupBlockEnv blocks id of
487 -- | Slightly more complicated than the usual fold because we want to tell block
488 -- 'b1' what its inline successor is going to be, so that if 'b1' ends with
489 -- 'goto b2', the goto can be omitted.
491 fold_layout f z g@(LGraph eid _) = fold (postorder_dfs g) z
492 where fold blocks z =
493 case blocks of [] -> z
495 b1 : b2 : bs -> fold (b2 : bs) (f b1 (nextlabel b2) z)
496 nextlabel (Block id _) =
497 if id == eid then panic "entry as successor"
500 -- | The rest of the traversals are straightforward
502 map_nodes idm middle last (LGraph eid blocks) = LGraph (idm eid) (mapUFM block blocks)
503 where block (Block id t) = Block (idm id) (tail t)
504 tail (ZTail m t) = ZTail (middle m) (tail t)
505 tail (ZLast LastExit) = ZLast LastExit
506 tail (ZLast (LastOther l)) = ZLast (LastOther (last l))
508 fold_blocks f z (LGraph _ blocks) = foldUFM f z blocks
510 of_block_list e blocks = LGraph e $ foldr insertBlock emptyBlockEnv blocks
511 to_block_list (LGraph _ blocks) = eltsUFM blocks
516 -- We want to be able to scrutinize a single-entry, single-exit 'LGraph' for
517 -- splicing purposes. There are two useful cases: the 'LGraph' is a single block
518 -- or it isn't. We use continuation-passing style.
520 prepare_for_splicing ::
521 LGraph m l -> (ZTail m l -> a) -> (ZTail m l -> ZHead m -> BlockEnv (Block m l) -> a)
523 prepare_for_splicing g single multi =
524 let FGraph _ gentry gblocks = entry g
525 ZBlock _ etail = gentry
526 in if isNullUFM gblocks then
528 LastExit -> single etail
529 _ -> panic "bad single block"
531 case splitp_blocks is_exit gblocks of
532 Nothing -> panic "Can't find an exit block"
533 Just (gexit, gblocks) ->
534 let (gh, gl) = goto_end $ unzip gexit in
535 case gl of LastExit -> multi etail gh gblocks
536 _ -> panic "exit is not exit?!"
538 prepare_for_splicing' ::
539 Graph m l -> (ZTail m l -> a) -> (ZTail m l -> ZHead m -> BlockEnv (Block m l) -> a)
541 prepare_for_splicing' (Graph etail gblocks) single multi =
542 if isNullUFM gblocks then
543 case lastTail etail of
544 LastExit -> single etail
545 _ -> panic "bad single block"
547 case splitp_blocks is_exit gblocks of
548 Nothing -> panic "Can't find an exit block"
549 Just (gexit, gblocks) ->
550 let (gh, gl) = goto_end $ unzip gexit in
551 case gl of LastExit -> multi etail gh gblocks
552 _ -> panic "exit is not exit?!"
554 is_exit :: Block m l -> Bool
555 is_exit b = case last (unzip b) of { LastExit -> True; _ -> False }
558 ASSERT (single_exit g) prepare_for_splicing g splice_one_block splice_many_blocks
559 where eid = head_id head
560 splice_one_block tail' =
561 case ht_to_last head tail' of
562 (head, LastExit) -> (LGraph eid emptyBlockEnv, head)
563 _ -> panic "spliced LGraph without exit"
564 splice_many_blocks entry exit others =
565 (LGraph eid (insertBlock (zipht head entry) others), exit)
567 splice_head' head g =
568 ASSERT (single_exitg g) prepare_for_splicing' g splice_one_block splice_many_blocks
569 where splice_one_block tail' =
570 case ht_to_last head tail' of
571 (head, LastExit) -> (emptyBlockEnv, head)
572 _ -> panic "spliced LGraph without exit"
573 splice_many_blocks entry exit others =
574 (insertBlock (zipht head entry) others, exit)
576 -- splice_tail :: Graph m l -> ZTail m l -> Graph m l
578 ASSERT (single_exitg g) prepare_for_splicing' g splice_one_block splice_many_blocks
579 where splice_one_block tail' = Graph (tail' `append_tails` tail) emptyBlockEnv
580 append_tails (ZLast LastExit) tail = tail
581 append_tails (ZLast _) _ = panic "spliced single block without LastExit"
582 append_tails (ZTail m t) tail = ZTail m (append_tails t tail)
583 splice_many_blocks entry exit others =
584 Graph entry (insertBlock (zipht exit tail) others)
588 AS SERT (single_exit g) prepare_for_splicing g splice_one_block splice_many_blocks
589 where splice_one_block tail' = -- return tail' .. tail
590 case ht_to_last (ZFirst (lg_entry g)) tail' of
592 case ht_to_block head' tail of
593 Block id t | id == lg_entry g -> (t, LGraph id emptyBlockEnv)
594 _ -> panic "entry in; garbage out"
595 _ -> panic "spliced single block without Exit"
596 splice_many_blocks entry exit others =
597 (entry, LGraph (lg_entry g) (insertBlock (zipht exit tail) others))
600 splice_head_only head g =
601 let FGraph eid gentry gblocks = entry g
603 ZBlock (ZFirst _) tail -> LGraph eid (insertBlock (zipht head tail) gblocks)
604 _ -> panic "entry not at start of block?!"
606 splice_head_only' head (Graph tail gblocks) =
607 let eblock = zipht head tail in
608 LGraph (blockId eblock) (insertBlock eblock gblocks)
613 translate txm txl (LGraph eid blocks) =
614 do blocks' <- foldUFM txblock (return emptyBlockEnv) blocks
615 return $ LGraph eid blocks'
618 -- Block m l -> UniqSM (BlockEnv (Block m' l')) -> UniqSM (BlockEnv (Block m' l'))
619 txblock (Block id t) expanded =
620 do blocks' <- expanded
621 txtail (ZFirst id) t blocks'
622 -- txtail :: ZHead m' -> ZTail m l -> BlockEnv (Block m' l') ->
623 -- UniqSM (BlockEnv (Block m' l'))
624 txtail h (ZTail m t) blocks' =
626 let (g, h') = splice_head h m'
627 txtail h' t (plusUFM (lg_blocks g) blocks')
628 txtail h (ZLast (LastOther l)) blocks' =
630 return $ plusUFM (lg_blocks (splice_head_only h l')) blocks'
631 txtail h (ZLast LastExit) blocks' =
632 return $ insertBlock (zipht h (ZLast LastExit)) blocks'
634 ----------------------------------------------------------------
635 --- Block Ids, their environments, and their sets
637 {- Note [Unique BlockId]
638 ~~~~~~~~~~~~~~~~~~~~~~~~
639 Although a 'BlockId' is a local label, for reasons of implementation,
640 'BlockId's must be unique within an entire compilation unit. The reason
641 is that each local label is mapped to an assembly-language label, and in
642 most assembly languages allow, a label is visible throughout the enitre
643 compilation unit in which it appears.
646 newtype BlockId = BlockId Unique
649 instance Uniquable BlockId where
650 getUnique (BlockId u) = u
652 instance Show BlockId where
653 show (BlockId u) = show u
655 instance Outputable BlockId where
656 ppr = ppr . getUnique
659 type BlockEnv a = UniqFM {- BlockId -} a
660 emptyBlockEnv :: BlockEnv a
661 emptyBlockEnv = emptyUFM
662 lookupBlockEnv :: BlockEnv a -> BlockId -> Maybe a
663 lookupBlockEnv = lookupUFM
664 extendBlockEnv :: BlockEnv a -> BlockId -> a -> BlockEnv a
665 extendBlockEnv = addToUFM
666 mkBlockEnv :: [(BlockId,a)] -> BlockEnv a
667 mkBlockEnv = listToUFM
669 type BlockSet = UniqSet BlockId
670 emptyBlockSet :: BlockSet
671 emptyBlockSet = emptyUniqSet
672 elemBlockSet :: BlockId -> BlockSet -> Bool
673 elemBlockSet = elementOfUniqSet
674 extendBlockSet :: BlockSet -> BlockId -> BlockSet
675 extendBlockSet = addOneToUniqSet
676 mkBlockSet :: [BlockId] -> BlockSet
677 mkBlockSet = mkUniqSet
679 ----------------------------------------------------------------
681 ----------------------------------------------------------------
683 -- putting this code in PprCmmZ leads to circular imports :-(
685 instance (Outputable m, Outputable l) => Outputable (ZTail m l) where
688 pprTail :: (Outputable m, Outputable l) => ZTail m l -> SDoc
689 pprTail (ZTail m t) = ppr m $$ ppr t
690 pprTail (ZLast LastExit) = text "<exit>"
691 pprTail (ZLast (LastOther l)) = ppr l
693 pprLgraph :: (Outputable m, Outputable l, LastNode l) => LGraph m l -> SDoc
694 pprLgraph g = text "{" $$ nest 2 (vcat $ map pprBlock blocks) $$ text "}"
695 where pprBlock (Block id tail) = ppr id <> colon $$ ppr tail
696 blocks = postorder_dfs g
698 pprGraph :: (Outputable m, Outputable l, LastNode l) => Graph m l -> SDoc
699 pprGraph (Graph tail blockenv) =
700 text "{" $$ nest 2 (ppr tail $$ (vcat $ map pprBlock blocks)) $$ text "}"
701 where pprBlock (Block id tail) = ppr id <> colon $$ ppr tail
702 blocks = postorder_dfs_from blockenv tail
704 _unused :: FS.FastString