2 ( -- These data types and names are carefully thought out
3 BlockId(..), mkBlockId -- ToDo: BlockId should be abstract, but it isn't yet
4 , BlockEnv, emptyBlockEnv, lookupBlockEnv, extendBlockEnv, insertBlock, mkBlockEnv
5 , BlockSet, emptyBlockSet, elemBlockSet, extendBlockSet, mkBlockSet
6 , Graph(..), LGraph(..), FGraph(..)
7 , Block(..), ZBlock(..), ZHead(..), ZTail(..), ZLast(..)
8 , HavingSuccessors, succs, fold_succs
9 , LastNode, mkBranchNode, isBranchNode, branchNodeTarget
11 -- Observers and transformers
12 -- (open to renaming suggestions here)
13 , blockId, zip, unzip, last, goto_end, zipht, tailOfLast
14 , splice_tail, splice_head, splice_head_only', splice_head'
15 , of_block_list, to_block_list
16 , map_blocks, map_nodes, mapM_blocks
17 , postorder_dfs, postorder_dfs_from, postorder_dfs_from_except
24 , entry -- exported for the convenience of ZipDataflow0, at least for now
27 -- the following functions might one day be useful and can be found
28 -- either below or in ZipCfgExtras:
29 , entry, exit, focus, focusp, unfocus
30 , ht_to_block, ht_to_last,
31 , splice_focus_entry, splice_focus_exit
32 , fold_fwd_block, foldM_fwd_block
38 #include "HsVersions.h"
40 import CmmExpr ( UserOfLocalRegs(..) ) --for an instance
42 import Outputable hiding (empty)
49 import Prelude hiding (zip, unzip, last)
51 -------------------------------------------------------------------------
52 -- GENERIC ZIPPER-BASED CONTROL-FLOW GRAPH --
53 -------------------------------------------------------------------------
56 This module defines datatypes used to represent control-flow graphs,
57 along with some functions for analyzing and splicing graphs.
58 Functions for building graphs are found in a separate module 'MkZipCfg'.
60 Every graph has a distinguished entry point. A graph has at least one
61 exit; most exits are instructions (or statements) like 'jump' or
62 'return', which transfer control to other procedures, but a graph may
63 have up to one 'fall through' exit. (A graph that represents an
64 entire Haskell or C-- procedure does not have a 'fall through' exit.)
66 A graph is a collection of basic blocks. A basic block begins with a
67 label (unique id; see Note [Unique BlockId]) which is followed by a
68 sequence of zero or more 'middle' nodes; the basic block ends with a
69 'last' node. Each 'middle' node is a single-entry, single-exit,
70 uninterruptible computation. A 'last' node is a single-entry,
71 multiple-exit computation. A last node may have zero or more successors,
72 which are identified by their unique ids.
74 A special case of last node is the ``default exit,'' which represents
75 'falling off the end' of the graph. Such a node is always represented by
76 the data constructor 'LastExit'. A graph may contain at most one
77 'LastExit' node, and a graph representing a full procedure should not
78 contain any 'LastExit' nodes. 'LastExit' nodes are used only to splice
79 graphs together, either during graph construction (see module 'MkZipCfg')
80 or during optimization (see module 'ZipDataflow0').
82 A graph is parameterized over the types of middle and last nodes. Each of
83 these types will typically be instantiated with a subset of C-- statements
84 (see module 'ZipCfgCmmRep') or a subset of machine instructions (yet to be
85 implemented as of August 2007).
88 Note [Kinds of Graphs]
89 ~~~~~~~~~~~~~~~~~~~~~~
90 This module exposes three representations of graphs. In order of
91 increasing complexity, they are:
93 Graph m l The basic graph with its distinguished entry point
95 LGraph m l A graph with a *labelled* entry point
97 FGraph m l A labelled graph with the *focus* on a particular edge
99 There are three types because each type offers a slightly different
100 invariant or cost model.
102 * The distinguished entry of a Graph has no label. Because labels must be
103 unique, acquiring one requires a supply of Unique labels (BlockId's).
104 The primary advantage of the Graph representation is that we can build a
105 small Graph purely functionally, without needing a fresh BlockId or
106 Unique. For example, during optimization we can easily rewrite a single
107 middle node into a Graph containing a sequence of two middle nodes
108 followed by LastExit.
110 * In an LGraph, every basic block is labelled. The primary advantage of
111 this representation is its simplicity: each basic block can be treated
112 like any other. This representation is used for mapping, folding, and
113 translation, as well as layout.
115 Like any graph, an LGraph still has a distinguished entry point,
116 which you can discover using 'lg_entry'.
118 * An FGraph is an LGraph with the *focus* on one particular edge. The
119 primary advantage of this representation is that it provides
120 constant-time access to the nodes connected by that edge, and it also
121 allows constant-time, functional *replacement* of those nodes---in the
122 style of Huet's 'zipper'.
124 None of these representations is ideally suited to the incremental
125 construction of large graphs. A separate module, 'MkZipCfg', provides a
126 fourth representation that is asymptotically optimal for such construction.
130 --------------- Representation --------------------
132 -- | A basic block is a 'first' node, followed by zero or more 'middle'
133 -- nodes, followed by a 'last' node.
135 -- eventually this module should probably replace the original Cmm, but for
136 -- now we leave it to dynamic invariants what can be found where
139 = LastExit -- fall through; used for the block that has no last node
140 -- LastExit is a device used only for graphs under
141 -- construction, or framgments of graph under optimisation,
142 -- so we don't want to pollute the 'l' type parameter with it
145 --So that we don't have orphan instances, this goes here or in CmmExpr.
146 --At least UserOfLocalRegs (ZLast Last) is needed (Last defined elsewhere),
147 --but there's no need for non-Haskell98 instances for that.
148 instance UserOfLocalRegs a => UserOfLocalRegs (ZLast a) where
149 foldRegsUsed f z (LastOther l) = foldRegsUsed f z l
150 foldRegsUsed _f z LastExit = z
153 data ZHead m = ZFirst BlockId | ZHead (ZHead m) m
154 -- ZHead is a (reversed) sequence of middle nodes labeled by a BlockId
155 data ZTail m l = ZLast (ZLast l) | ZTail m (ZTail m l)
156 -- ZTail is a sequence of middle nodes followed by a last node
158 -- | Blocks and flow graphs; see Note [Kinds of graphs]
159 data Block m l = Block BlockId (ZTail m l)
161 data Graph m l = Graph { g_entry :: (ZTail m l), g_blocks :: (BlockEnv (Block m l)) }
163 data LGraph m l = LGraph { lg_entry :: BlockId
164 , lg_blocks :: BlockEnv (Block m l) }
165 -- Invariant: lg_entry is in domain( lg_blocks )
167 -- | And now the zipper. The focus is between the head and tail.
168 -- We cannot ever focus on an inter-block edge.
169 data ZBlock m l = ZBlock (ZHead m) (ZTail m l)
170 data FGraph m l = FGraph { fg_entry :: BlockId
171 , fg_focus :: ZBlock m l
172 , fg_others :: BlockEnv (Block m l) }
173 -- Invariant: the block represented by 'fg_focus' is *not*
174 -- in the map 'fg_others'
176 ---- Utility functions ---
178 blockId :: Block m l -> BlockId
179 zip :: ZBlock m l -> Block m l
180 unzip :: Block m l -> ZBlock m l
182 last :: ZBlock m l -> ZLast l
183 goto_end :: ZBlock m l -> (ZHead m, ZLast l)
185 tailOfLast :: l -> ZTail m l
187 -- | Take a head and tail and go to beginning or end. The asymmetry
188 -- in the types and names is a bit unfortunate, but 'Block m l' is
189 -- effectively '(BlockId, ZTail m l)' and is accepted in many more places.
191 ht_to_block, zipht :: ZHead m -> ZTail m l -> Block m l
192 ht_to_last :: ZHead m -> ZTail m l -> (ZHead m, ZLast l)
194 -- | We can splice a single-entry, single-exit LGraph onto a head or a tail.
195 -- For a head, we have a head 'h' followed by a LGraph 'g'.
196 -- The entry node of 'g' gets joined to 'h', forming the entry into
197 -- the new LGraph. The exit of 'g' becomes the new head.
198 -- For both arguments and results, the order of values is the order of
199 -- control flow: before splicing, the head flows into the LGraph; after
200 -- splicing, the LGraph flows into the head.
201 -- Splicing a tail is the dual operation.
202 -- (In order to maintain the order-means-control-flow convention, the
203 -- orders are reversed.)
205 -- For example, assume
207 -- grph = (M, [M: <stuff>,
209 -- N: y:=x; LastExit])
210 -- tail = [return (y,x)]
212 -- Then splice_head head grph
213 -- = ((L, [L: x:=0; goto M,
218 -- Then splice_tail grph tail
220 -- , (???, [<blocks>,
221 -- N: y:=x; return (y,x)])
223 splice_head :: ZHead m -> LGraph m l -> (LGraph m l, ZHead m)
224 splice_head' :: ZHead m -> Graph m l -> (BlockEnv (Block m l), ZHead m)
225 splice_tail :: Graph m l -> ZTail m l -> Graph m l
227 -- | We can also splice a single-entry, no-exit Graph into a head.
228 splice_head_only :: ZHead m -> LGraph m l -> LGraph m l
229 splice_head_only' :: ZHead m -> Graph m l -> LGraph m l
232 -- | A safe operation
234 -- | Conversion to and from the environment form is convenient. For
235 -- layout or dataflow, however, one will want to use 'postorder_dfs'
236 -- in order to get the blocks in an order that relates to the control
237 -- flow in the procedure.
238 of_block_list :: BlockId -> [Block m l] -> LGraph m l -- N log N
239 to_block_list :: LGraph m l -> [Block m l] -- N log N
241 -- | Traversal: 'postorder_dfs' returns a list of blocks reachable
242 -- from the entry node. This list has the following property:
244 -- Say a "back reference" exists if one of a block's
245 -- control-flow successors precedes it in the output list
247 -- Then there are as few back references as possible
249 -- The output is suitable for use in
250 -- a forward dataflow problem. For a backward problem, simply reverse
251 -- the list. ('postorder_dfs' is sufficiently tricky to implement that
252 -- one doesn't want to try and maintain both forward and backward
255 postorder_dfs :: LastNode l => LGraph m l -> [Block m l]
257 -- | For layout, we fold over pairs of 'Block m l' and 'Maybe BlockId'
258 -- in layout order. The 'Maybe BlockId', if present, identifies the
259 -- block that will be the layout successor of the current block. This
260 -- may be useful to help an emitter omit the final 'goto' of a block
261 -- that flows directly to its layout successor.
263 -- For example: fold_layout f z [ L1:B1, L2:B2, L3:B3 ]
264 -- = z <$> f (L1:B1) (Just L2)
265 -- <$> f (L2:B2) (Just L3)
266 -- <$> f (L3:B3) Nothing
267 -- where a <$> f = f a
269 LastNode l => (Block m l -> Maybe BlockId -> a -> a) -> a -> LGraph m l-> a
271 -- | We can also fold over blocks in an unspecified order. The
272 -- 'ZipCfgExtras' module provides a monadic version, which we
273 -- haven't needed (else it would be here).
274 fold_blocks :: (Block m l -> a -> a) -> a -> LGraph m l -> a
276 map_nodes :: (BlockId -> BlockId) -> (m -> m') -> (l -> l') -> LGraph m l -> LGraph m' l'
277 -- mapping includes the entry id!
279 map_blocks :: (Block m l -> Block m' l') -> LGraph m l -> LGraph m' l'
280 mapM_blocks :: Monad mm
281 => (Block m l -> mm (Block m' l')) -> LGraph m l -> mm (LGraph m' l')
283 -- | These translation functions are speculative. I hope eventually
284 -- they will be used in the native-code back ends ---NR
285 translate :: Monad tm =>
286 (m -> tm (LGraph m' l')) ->
287 (l -> tm (LGraph m' l')) ->
288 (LGraph m l -> tm (LGraph m' l'))
291 -- | It's possible that another form of translation would be more suitable:
292 translateA :: (m -> Agraph m' l') -> (l -> AGraph m' l') -> LGraph m l -> LGraph m' l'
295 ------------------- Last nodes
297 -- | We can't make a graph out of just any old 'last node' type. A last node
298 -- has to be able to find its successors, and we need to be able to create and
299 -- identify unconditional branches. We put these capabilities in a type class.
300 -- Moreover, the property of having successors is also shared by 'Block's and
301 -- 'ZTails', so it is useful to have that property in a type class of its own.
303 class HavingSuccessors b where
304 succs :: b -> [BlockId]
305 fold_succs :: (BlockId -> a -> a) -> b -> a -> a
307 fold_succs add l z = foldr add z $ succs l
309 class HavingSuccessors l => LastNode l where
310 mkBranchNode :: BlockId -> l
311 isBranchNode :: l -> Bool
312 branchNodeTarget :: l -> BlockId -- panics if not branch node
313 -- ^ N.B. This interface seems to make for more congenial clients than a
314 -- single function of type 'l -> Maybe BlockId'
316 instance HavingSuccessors l => HavingSuccessors (ZLast l) where
318 succs (LastOther l) = succs l
319 fold_succs _ LastExit z = z
320 fold_succs f (LastOther l) z = fold_succs f l z
322 instance LastNode l => LastNode (ZLast l) where
323 mkBranchNode id = LastOther $ mkBranchNode id
324 isBranchNode LastExit = False
325 isBranchNode (LastOther l) = isBranchNode l
326 branchNodeTarget LastExit = panic "branchNodeTarget LastExit"
327 branchNodeTarget (LastOther l) = branchNodeTarget l
329 instance LastNode l => HavingSuccessors (ZBlock m l) where
330 succs b = succs (last b)
332 instance LastNode l => HavingSuccessors (Block m l) where
333 succs b = succs (unzip b)
335 instance LastNode l => HavingSuccessors (ZTail m l) where
336 succs b = succs (lastTail b)
340 -- ================ IMPLEMENTATION ================--
342 ----- block manipulations
344 blockId (Block id _) = id
346 -- | Convert block between forms.
347 -- These functions are tail-recursive, so we can go as deep as we like
348 -- without fear of stack overflow.
350 ht_to_block head tail = case head of
351 ZFirst id -> Block id tail
352 ZHead h m -> ht_to_block h (ZTail m tail)
354 ht_to_last head (ZLast l) = (head, l)
355 ht_to_last head (ZTail m t) = ht_to_last (ZHead head m) t
357 zipht h t = ht_to_block h t
358 zip (ZBlock h t) = ht_to_block h t
359 goto_end (ZBlock h t) = ht_to_last h t
361 unzip (Block id t) = ZBlock (ZFirst id) t
363 head_id :: ZHead m -> BlockId
364 head_id (ZFirst id) = id
365 head_id (ZHead h _) = head_id h
367 last (ZBlock _ t) = lastTail t
369 lastTail :: ZTail m l -> ZLast l
370 lastTail (ZLast l) = l
371 lastTail (ZTail _ t) = lastTail t
373 tailOfLast l = ZLast (LastOther l) -- ^ tedious to write in every client
376 ------------------ simple graph manipulations
378 focus :: BlockId -> LGraph m l -> FGraph m l -- focus on edge out of node with id
379 focus id (LGraph entry blocks) =
380 case lookupBlockEnv blocks id of
381 Just b -> FGraph entry (unzip b) (delFromUFM blocks id)
382 Nothing -> panic "asked for nonexistent block in flow graph"
384 entry :: LGraph m l -> FGraph m l -- focus on edge out of entry node
385 entry g@(LGraph eid _) = focus eid g
387 -- | pull out a block satisfying the predicate, if any
388 splitp_blocks :: (Block m l -> Bool) -> BlockEnv (Block m l) ->
389 Maybe (Block m l, BlockEnv (Block m l))
390 splitp_blocks p blocks = lift $ foldUFM scan (Nothing, emptyBlockEnv) blocks
391 where scan b (yes, no) =
393 Nothing | p b -> (Just b, no)
394 | otherwise -> (yes, insertBlock b no)
395 Just _ -> (yes, insertBlock b no)
396 lift (Nothing, _) = Nothing
397 lift (Just b, bs) = Just (b, bs)
399 -- | 'insertBlock' should not be used to *replace* an existing block
400 -- but only to insert a new one
401 insertBlock :: Block m l -> BlockEnv (Block m l) -> BlockEnv (Block m l)
403 ASSERT (isNothing $ lookupBlockEnv bs id)
404 extendBlockEnv bs id b
407 -- | Used in assertions; tells if a graph has exactly one exit
408 single_exit :: LGraph l m -> Bool
409 single_exit g = foldUFM check 0 (lg_blocks g) == 1
410 where check block count = case last (unzip block) of
411 LastExit -> count + (1 :: Int)
414 -- | Used in assertions; tells if a graph has exactly one exit
415 single_exitg :: Graph l m -> Bool
416 single_exitg (Graph tail blocks) = foldUFM add (exit_count (lastTail tail)) blocks == 1
417 where add block count = count + exit_count (last (unzip block))
418 exit_count LastExit = 1 :: Int
421 ------------------ graph traversals
423 -- | This is the most important traversal over this data structure. It drops
424 -- unreachable code and puts blocks in an order that is good for solving forward
425 -- dataflow problems quickly. The reverse order is good for solving backward
426 -- dataflow problems quickly. The forward order is also reasonably good for
427 -- emitting instructions, except that it will not usually exploit Forrest
428 -- Baskett's trick of eliminating the unconditional branch from a loop. For
429 -- that you would need a more serious analysis, probably based on dominators, to
430 -- identify loop headers.
432 -- The ubiquity of 'postorder_dfs' is one reason for the ubiquity of the 'LGraph'
433 -- representation, when for most purposes the plain 'Graph' representation is
434 -- more mathematically elegant (but results in more complicated code).
436 -- Here's an easy way to go wrong! Consider
440 -- Then ordinary dfs would give [A,B,D,C] which has a back ref from C to D.
441 -- Better to geot [A,B,C,D]
444 postorder_dfs g@(LGraph _ blockenv) =
445 let FGraph id eblock _ = entry g in
446 zip eblock : postorder_dfs_from_except blockenv eblock (unitUniqSet id)
448 postorder_dfs_from_except :: (HavingSuccessors b, LastNode l)
449 => BlockEnv (Block m l) -> b -> BlockSet -> [Block m l]
450 postorder_dfs_from_except blocks b visited =
451 vchildren (get_children b) (\acc _visited -> acc) [] visited
454 -- Block m l -> ([Block m l] -> BlockSet -> a) -> [Block m l] -> BlockSet -> a
455 vnode block@(Block id _) cont acc visited =
456 if elemBlockSet id visited then
459 let cont' acc visited = cont (block:acc) visited in
460 vchildren (get_children block) cont' acc (extendBlockSet visited id)
461 vchildren bs cont acc visited =
462 let next children acc visited =
463 case children of [] -> cont acc visited
464 (b:bs) -> vnode b (next bs) acc visited
465 in next bs acc visited
466 get_children block = foldl add_id [] (succs block)
467 add_id rst id = case lookupBlockEnv blocks id of
472 :: (HavingSuccessors b, LastNode l) => BlockEnv (Block m l) -> b -> [Block m l]
473 postorder_dfs_from blocks b = postorder_dfs_from_except blocks b emptyBlockSet
477 -- | Slightly more complicated than the usual fold because we want to tell block
478 -- 'b1' what its inline successor is going to be, so that if 'b1' ends with
479 -- 'goto b2', the goto can be omitted.
481 fold_layout f z g@(LGraph eid _) = fold (postorder_dfs g) z
482 where fold blocks z =
483 case blocks of [] -> z
485 b1 : b2 : bs -> fold (b2 : bs) (f b1 (nextlabel b2) z)
486 nextlabel (Block id _) =
487 if id == eid then panic "entry as successor"
490 -- | The rest of the traversals are straightforward
492 map_blocks f (LGraph eid blocks) = LGraph eid (mapUFM f blocks)
494 map_nodes idm middle last (LGraph eid blocks) = LGraph (idm eid) (mapUFM block blocks)
495 where block (Block id t) = Block (idm id) (tail t)
496 tail (ZTail m t) = ZTail (middle m) (tail t)
497 tail (ZLast LastExit) = ZLast LastExit
498 tail (ZLast (LastOther l)) = ZLast (LastOther (last l))
501 mapM_blocks f (LGraph eid blocks) = blocks' >>= return . LGraph eid
503 foldUFM (\b mblocks -> do { blocks <- mblocks
505 ; return $ insertBlock b blocks })
506 (return emptyBlockEnv) blocks
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 -> tm (BlockEnv (Block m' l')) -> tm (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 -- tm (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 mkBlockId :: Unique -> BlockId
653 mkBlockId uniq = BlockId uniq
655 instance Show BlockId where
656 show (BlockId u) = show u
658 instance Outputable BlockId where
659 ppr = ppr . getUnique
662 type BlockEnv a = UniqFM {- BlockId -} a
663 emptyBlockEnv :: BlockEnv a
664 emptyBlockEnv = emptyUFM
665 lookupBlockEnv :: BlockEnv a -> BlockId -> Maybe a
666 lookupBlockEnv = lookupUFM
667 extendBlockEnv :: BlockEnv a -> BlockId -> a -> BlockEnv a
668 extendBlockEnv = addToUFM
669 mkBlockEnv :: [(BlockId,a)] -> BlockEnv a
670 mkBlockEnv = listToUFM
672 type BlockSet = UniqSet BlockId
673 emptyBlockSet :: BlockSet
674 emptyBlockSet = emptyUniqSet
675 elemBlockSet :: BlockId -> BlockSet -> Bool
676 elemBlockSet = elementOfUniqSet
677 extendBlockSet :: BlockSet -> BlockId -> BlockSet
678 extendBlockSet = addOneToUniqSet
679 mkBlockSet :: [BlockId] -> BlockSet
680 mkBlockSet = mkUniqSet
682 ----------------------------------------------------------------
684 ----------------------------------------------------------------
686 -- putting this code in PprCmmZ leads to circular imports :-(
688 instance (Outputable m, Outputable l) => Outputable (ZTail m l) where
691 instance (Outputable m, Outputable l, LastNode l) => Outputable (LGraph m l) where
694 instance (Outputable l) => Outputable (ZLast l) where
697 pprTail :: (Outputable m, Outputable l) => ZTail m l -> SDoc
698 pprTail (ZTail m t) = ppr m $$ ppr t
699 pprTail (ZLast l) = ppr l
701 pprLast :: (Outputable l) => ZLast l -> SDoc
702 pprLast LastExit = text "<exit>"
703 pprLast (LastOther l) = ppr l
705 pprLgraph :: (Outputable m, Outputable l, LastNode l) => LGraph m l -> SDoc
706 pprLgraph g = text "{" $$ nest 2 (vcat $ map pprBlock blocks) $$ text "}"
707 where pprBlock (Block id tail) = ppr id <> colon $$ ppr tail
708 blocks = postorder_dfs g
710 pprGraph :: (Outputable m, Outputable l, LastNode l) => Graph m l -> SDoc
711 pprGraph (Graph tail blockenv) =
712 text "{" $$ nest 2 (ppr tail $$ (vcat $ map pprBlock blocks)) $$ text "}"
713 where pprBlock (Block id tail) = ppr id <> colon $$ ppr tail
714 blocks = postorder_dfs_from blockenv tail