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 :: (m -> UniqSM (LGraph m' l')) ->
275 (l -> UniqSM (LGraph m' l')) ->
276 (LGraph m l -> UniqSM (LGraph m' l'))
279 -- | It's possible that another form of translation would be more suitable:
280 translateA :: (m -> Agraph m' l') -> (l -> AGraph m' l') -> LGraph m l -> LGraph m' l'
283 ------------------- Last nodes
285 -- | We can't make a graph out of just any old 'last node' type. A last node
286 -- has to be able to find its successors, and we need to be able to create and
287 -- identify unconditional branches. We put these capabilities in a type class.
288 -- Moreover, the property of having successors is also shared by 'Block's and
289 -- 'ZTails', so it is useful to have that property in a type class of its own.
291 class HavingSuccessors b where
292 succs :: b -> [BlockId]
293 fold_succs :: (BlockId -> a -> a) -> b -> a -> a
295 fold_succs add l z = foldr add z $ succs l
297 class HavingSuccessors l => LastNode l where
298 mkBranchNode :: BlockId -> l
299 isBranchNode :: l -> Bool
300 branchNodeTarget :: l -> BlockId -- panics if not branch node
301 -- ^ N.B. This interface seems to make for more congenial clients than a
302 -- single function of type 'l -> Maybe BlockId'
304 instance HavingSuccessors l => HavingSuccessors (ZLast l) where
306 succs (LastOther l) = succs l
307 fold_succs _ LastExit z = z
308 fold_succs f (LastOther l) z = fold_succs f l z
310 instance LastNode l => LastNode (ZLast l) where
311 mkBranchNode id = LastOther $ mkBranchNode id
312 isBranchNode LastExit = False
313 isBranchNode (LastOther l) = isBranchNode l
314 branchNodeTarget LastExit = panic "branchNodeTarget LastExit"
315 branchNodeTarget (LastOther l) = branchNodeTarget l
317 instance LastNode l => HavingSuccessors (ZBlock m l) where
318 succs b = succs (last b)
320 instance LastNode l => HavingSuccessors (Block m l) where
321 succs b = succs (unzip b)
323 instance LastNode l => HavingSuccessors (ZTail m l) where
324 succs b = succs (lastTail b)
328 -- ================ IMPLEMENTATION ================--
330 ----- block manipulations
332 blockId (Block id _) = id
334 -- | Convert block between forms.
335 -- These functions are tail-recursive, so we can go as deep as we like
336 -- without fear of stack overflow.
338 ht_to_block head tail = case head of
339 ZFirst id -> Block id tail
340 ZHead h m -> ht_to_block h (ZTail m tail)
342 ht_to_last head (ZLast l) = (head, l)
343 ht_to_last head (ZTail m t) = ht_to_last (ZHead head m) t
345 zipht h t = ht_to_block h t
346 zip (ZBlock h t) = ht_to_block h t
347 goto_end (ZBlock h t) = ht_to_last h t
349 unzip (Block id t) = ZBlock (ZFirst id) t
351 head_id :: ZHead m -> BlockId
352 head_id (ZFirst id) = id
353 head_id (ZHead h _) = head_id h
355 last (ZBlock _ t) = lastTail t
357 lastTail :: ZTail m l -> ZLast l
358 lastTail (ZLast l) = l
359 lastTail (ZTail _ t) = lastTail t
361 tailOfLast l = ZLast (LastOther l) -- ^ tedious to write in every client
364 ------------------ simple graph manipulations
366 focus :: BlockId -> LGraph m l -> FGraph m l -- focus on edge out of node with id
367 focus id (LGraph entry blocks) =
368 case lookupBlockEnv blocks id of
369 Just b -> FGraph entry (unzip b) (delFromUFM blocks id)
370 Nothing -> panic "asked for nonexistent block in flow graph"
372 entry :: LGraph m l -> FGraph m l -- focus on edge out of entry node
373 entry g@(LGraph eid _) = focus eid g
375 -- | pull out a block satisfying the predicate, if any
376 splitp_blocks :: (Block m l -> Bool) -> BlockEnv (Block m l) ->
377 Maybe (Block m l, BlockEnv (Block m l))
378 splitp_blocks p blocks = lift $ foldUFM scan (Nothing, emptyBlockEnv) blocks
379 where scan b (yes, no) =
381 Nothing | p b -> (Just b, no)
382 | otherwise -> (yes, insertBlock b no)
383 Just _ -> (yes, insertBlock b no)
384 lift (Nothing, _) = Nothing
385 lift (Just b, bs) = Just (b, bs)
387 -- | 'insertBlock' should not be used to *replace* an existing block
388 -- but only to insert a new one
389 insertBlock :: Block m l -> BlockEnv (Block m l) -> BlockEnv (Block m l)
391 ASSERT (isNothing $ lookupBlockEnv bs id)
392 extendBlockEnv bs id b
395 -- | Used in assertions; tells if a graph has exactly one exit
396 single_exit :: LGraph l m -> Bool
397 single_exit g = foldUFM check 0 (lg_blocks g) == 1
398 where check block count = case last (unzip block) of
399 LastExit -> count + (1 :: Int)
402 -- | Used in assertions; tells if a graph has exactly one exit
403 single_exitg :: Graph l m -> Bool
404 single_exitg (Graph tail blocks) = foldUFM add (exit_count (lastTail tail)) blocks == 1
405 where add block count = count + exit_count (last (unzip block))
406 exit_count LastExit = 1 :: Int
409 ------------------ graph traversals
411 -- | This is the most important traversal over this data structure. It drops
412 -- unreachable code and puts blocks in an order that is good for solving forward
413 -- dataflow problems quickly. The reverse order is good for solving backward
414 -- dataflow problems quickly. The forward order is also reasonably good for
415 -- emitting instructions, except that it will not usually exploit Forrest
416 -- Baskett's trick of eliminating the unconditional branch from a loop. For
417 -- that you would need a more serious analysis, probably based on dominators, to
418 -- identify loop headers.
420 -- The ubiquity of 'postorder_dfs' is one reason for the ubiquity of the 'LGraph'
421 -- representation, when for most purposes the plain 'Graph' representation is
422 -- more mathematically elegant (but results in more complicated code).
424 -- Here's an easy way to go wrong! Consider
428 -- Then ordinary dfs would give [A,B,D,C] which has a back ref from C to D.
429 -- Better to geot [A,B,C,D]
432 postorder_dfs' :: LastNode l => LGraph m l -> [Block m l]
433 postorder_dfs' g@(LGraph _ blocks) =
434 let FGraph _ eblock _ = entry g
435 in vnode (zip eblock) (\acc _visited -> acc) [] emptyBlockSet
438 -- Block m l -> ([Block m l] -> BlockSet -> a) -> [Block m l] -> BlockSet -> a
439 vnode block@(Block id _) cont acc visited =
440 if elemBlockSet id visited then
443 vchildren block (get_children block) cont acc (extendBlockSet visited id)
444 vchildren block bs cont acc visited =
445 let next children acc visited =
446 case children of [] -> cont (block : acc) visited
447 (b:bs) -> vnode b (next bs) acc visited
448 in next bs acc visited
449 get_children block = foldl add_id [] (succs block)
450 add_id rst id = case lookupBlockEnv blocks id of
454 postorder_dfs g@(LGraph _ blockenv) =
455 let FGraph id eblock _ = entry g
457 postorder_dfs_from_except blockenv eblock (unitUniqSet id)
458 dfs2 = postorder_dfs' g
459 -- in ASSERT (map blockId dfs1 == map blockId dfs2) dfs2
460 in if (map blockId dfs1 == map blockId dfs2) then dfs2 else panic "inconsistent DFS"
463 :: (HavingSuccessors b, LastNode l) => BlockEnv (Block m l) -> b -> [Block m l]
464 postorder_dfs_from blocks b = postorder_dfs_from_except blocks b emptyBlockSet
466 postorder_dfs_from_except :: forall b m l . (HavingSuccessors b, LastNode l) => BlockEnv (Block m l) -> b -> BlockSet -> [Block m l]
467 postorder_dfs_from_except blocks b visited =
468 vchildren (get_children b) (\acc _visited -> acc) [] visited
471 -- Block m l -> ([Block m l] -> BlockSet -> a) -> [Block m l] -> BlockSet -> a
472 vnode block@(Block id _) cont acc visited =
473 if elemBlockSet id visited then
476 let cont' acc visited = cont (block:acc) visited in
477 vchildren (get_children block) cont' acc (extendBlockSet visited id)
478 vchildren bs cont acc visited =
479 let next children acc visited =
480 case children of [] -> cont acc visited
481 (b:bs) -> vnode b (next bs) acc visited
482 in next bs acc visited
483 get_children block = foldl add_id [] (succs block)
484 add_id rst id = case lookupBlockEnv blocks id of
489 -- | Slightly more complicated than the usual fold because we want to tell block
490 -- 'b1' what its inline successor is going to be, so that if 'b1' ends with
491 -- 'goto b2', the goto can be omitted.
493 fold_layout f z g@(LGraph eid _) = fold (postorder_dfs g) z
494 where fold blocks z =
495 case blocks of [] -> z
497 b1 : b2 : bs -> fold (b2 : bs) (f b1 (nextlabel b2) z)
498 nextlabel (Block id _) =
499 if id == eid then panic "entry as successor"
502 -- | The rest of the traversals are straightforward
504 map_blocks f (LGraph eid blocks) = LGraph eid (mapUFM f blocks)
506 map_nodes idm middle last (LGraph eid blocks) = LGraph (idm eid) (mapUFM block blocks)
507 where block (Block id t) = Block (idm id) (tail t)
508 tail (ZTail m t) = ZTail (middle m) (tail t)
509 tail (ZLast LastExit) = ZLast LastExit
510 tail (ZLast (LastOther l)) = ZLast (LastOther (last l))
512 fold_blocks f z (LGraph _ blocks) = foldUFM f z blocks
514 of_block_list e blocks = LGraph e $ foldr insertBlock emptyBlockEnv blocks
515 to_block_list (LGraph _ blocks) = eltsUFM blocks
520 -- We want to be able to scrutinize a single-entry, single-exit 'LGraph' for
521 -- splicing purposes. There are two useful cases: the 'LGraph' is a single block
522 -- or it isn't. We use continuation-passing style.
524 prepare_for_splicing ::
525 LGraph m l -> (ZTail m l -> a) -> (ZTail m l -> ZHead m -> BlockEnv (Block m l) -> a)
527 prepare_for_splicing g single multi =
528 let FGraph _ gentry gblocks = entry g
529 ZBlock _ etail = gentry
530 in if isNullUFM gblocks then
532 LastExit -> single etail
533 _ -> panic "bad single block"
535 case splitp_blocks is_exit gblocks of
536 Nothing -> panic "Can't find an exit block"
537 Just (gexit, gblocks) ->
538 let (gh, gl) = goto_end $ unzip gexit in
539 case gl of LastExit -> multi etail gh gblocks
540 _ -> panic "exit is not exit?!"
542 prepare_for_splicing' ::
543 Graph m l -> (ZTail m l -> a) -> (ZTail m l -> ZHead m -> BlockEnv (Block m l) -> a)
545 prepare_for_splicing' (Graph etail gblocks) single multi =
546 if isNullUFM gblocks then
547 case lastTail etail of
548 LastExit -> single etail
549 _ -> panic "bad single block"
551 case splitp_blocks is_exit gblocks of
552 Nothing -> panic "Can't find an exit block"
553 Just (gexit, gblocks) ->
554 let (gh, gl) = goto_end $ unzip gexit in
555 case gl of LastExit -> multi etail gh gblocks
556 _ -> panic "exit is not exit?!"
558 is_exit :: Block m l -> Bool
559 is_exit b = case last (unzip b) of { LastExit -> True; _ -> False }
562 ASSERT (single_exit g) prepare_for_splicing g splice_one_block splice_many_blocks
563 where eid = head_id head
564 splice_one_block tail' =
565 case ht_to_last head tail' of
566 (head, LastExit) -> (LGraph eid emptyBlockEnv, head)
567 _ -> panic "spliced LGraph without exit"
568 splice_many_blocks entry exit others =
569 (LGraph eid (insertBlock (zipht head entry) others), exit)
571 splice_head' head g =
572 ASSERT (single_exitg g) prepare_for_splicing' g splice_one_block splice_many_blocks
573 where splice_one_block tail' =
574 case ht_to_last head tail' of
575 (head, LastExit) -> (emptyBlockEnv, head)
576 _ -> panic "spliced LGraph without exit"
577 splice_many_blocks entry exit others =
578 (insertBlock (zipht head entry) others, exit)
580 -- splice_tail :: Graph m l -> ZTail m l -> Graph m l
582 ASSERT (single_exitg g) prepare_for_splicing' g splice_one_block splice_many_blocks
583 where splice_one_block tail' = Graph (tail' `append_tails` tail) emptyBlockEnv
584 append_tails (ZLast LastExit) tail = tail
585 append_tails (ZLast _) _ = panic "spliced single block without LastExit"
586 append_tails (ZTail m t) tail = ZTail m (append_tails t tail)
587 splice_many_blocks entry exit others =
588 Graph entry (insertBlock (zipht exit tail) others)
592 AS SERT (single_exit g) prepare_for_splicing g splice_one_block splice_many_blocks
593 where splice_one_block tail' = -- return tail' .. tail
594 case ht_to_last (ZFirst (lg_entry g)) tail' of
596 case ht_to_block head' tail of
597 Block id t | id == lg_entry g -> (t, LGraph id emptyBlockEnv)
598 _ -> panic "entry in; garbage out"
599 _ -> panic "spliced single block without Exit"
600 splice_many_blocks entry exit others =
601 (entry, LGraph (lg_entry g) (insertBlock (zipht exit tail) others))
604 splice_head_only head g =
605 let FGraph eid gentry gblocks = entry g
607 ZBlock (ZFirst _) tail -> LGraph eid (insertBlock (zipht head tail) gblocks)
608 _ -> panic "entry not at start of block?!"
610 splice_head_only' head (Graph tail gblocks) =
611 let eblock = zipht head tail in
612 LGraph (blockId eblock) (insertBlock eblock gblocks)
617 translate txm txl (LGraph eid blocks) =
618 do blocks' <- foldUFM txblock (return emptyBlockEnv) blocks
619 return $ LGraph eid blocks'
622 -- Block m l -> UniqSM (BlockEnv (Block m' l')) -> UniqSM (BlockEnv (Block m' l'))
623 txblock (Block id t) expanded =
624 do blocks' <- expanded
625 txtail (ZFirst id) t blocks'
626 -- txtail :: ZHead m' -> ZTail m l -> BlockEnv (Block m' l') ->
627 -- UniqSM (BlockEnv (Block m' l'))
628 txtail h (ZTail m t) blocks' =
630 let (g, h') = splice_head h m'
631 txtail h' t (plusUFM (lg_blocks g) blocks')
632 txtail h (ZLast (LastOther l)) blocks' =
634 return $ plusUFM (lg_blocks (splice_head_only h l')) blocks'
635 txtail h (ZLast LastExit) blocks' =
636 return $ insertBlock (zipht h (ZLast LastExit)) blocks'
638 ----------------------------------------------------------------
639 --- Block Ids, their environments, and their sets
641 {- Note [Unique BlockId]
642 ~~~~~~~~~~~~~~~~~~~~~~~~
643 Although a 'BlockId' is a local label, for reasons of implementation,
644 'BlockId's must be unique within an entire compilation unit. The reason
645 is that each local label is mapped to an assembly-language label, and in
646 most assembly languages allow, a label is visible throughout the enitre
647 compilation unit in which it appears.
650 newtype BlockId = BlockId Unique
653 instance Uniquable BlockId where
654 getUnique (BlockId u) = u
656 instance Show BlockId where
657 show (BlockId u) = show u
659 instance Outputable BlockId where
660 ppr = ppr . getUnique
663 type BlockEnv a = UniqFM {- BlockId -} a
664 emptyBlockEnv :: BlockEnv a
665 emptyBlockEnv = emptyUFM
666 lookupBlockEnv :: BlockEnv a -> BlockId -> Maybe a
667 lookupBlockEnv = lookupUFM
668 extendBlockEnv :: BlockEnv a -> BlockId -> a -> BlockEnv a
669 extendBlockEnv = addToUFM
670 mkBlockEnv :: [(BlockId,a)] -> BlockEnv a
671 mkBlockEnv = listToUFM
673 type BlockSet = UniqSet BlockId
674 emptyBlockSet :: BlockSet
675 emptyBlockSet = emptyUniqSet
676 elemBlockSet :: BlockId -> BlockSet -> Bool
677 elemBlockSet = elementOfUniqSet
678 extendBlockSet :: BlockSet -> BlockId -> BlockSet
679 extendBlockSet = addOneToUniqSet
680 mkBlockSet :: [BlockId] -> BlockSet
681 mkBlockSet = mkUniqSet
683 ----------------------------------------------------------------
685 ----------------------------------------------------------------
687 -- putting this code in PprCmmZ leads to circular imports :-(
689 instance (Outputable m, Outputable l) => Outputable (ZTail m l) where
692 pprTail :: (Outputable m, Outputable l) => ZTail m l -> SDoc
693 pprTail (ZTail m t) = ppr m $$ ppr t
694 pprTail (ZLast LastExit) = text "<exit>"
695 pprTail (ZLast (LastOther l)) = ppr l
697 pprLgraph :: (Outputable m, Outputable l, LastNode l) => LGraph m l -> SDoc
698 pprLgraph g = text "{" $$ nest 2 (vcat $ map pprBlock blocks) $$ text "}"
699 where pprBlock (Block id tail) = ppr id <> colon $$ ppr tail
700 blocks = postorder_dfs g
702 pprGraph :: (Outputable m, Outputable l, LastNode l) => Graph m l -> SDoc
703 pprGraph (Graph tail blockenv) =
704 text "{" $$ nest 2 (ppr tail $$ (vcat $ map pprBlock blocks)) $$ text "}"
705 where pprBlock (Block id tail) = ppr id <> colon $$ ppr tail
706 blocks = postorder_dfs_from blockenv tail
708 _unused :: FS.FastString