1 {-# LANGUAGE ScopedTypeVariables #-}
3 ( -- These data types and names are carefully thought out
4 BlockId(..), freshBlockId -- ToDo: BlockId should be abstract,
6 , BlockEnv, emptyBlockEnv, lookupBlockEnv, extendBlockEnv, insertBlock, mkBlockEnv
7 , BlockSet, emptyBlockSet, elemBlockSet, extendBlockSet, mkBlockSet
8 , Graph(..), LGraph(..), FGraph(..)
9 , Block(..), ZBlock(..), ZHead(..), ZTail(..), ZLast(..)
10 , HavingSuccessors, succs, fold_succs
11 , LastNode, mkBranchNode, isBranchNode, branchNodeTarget
13 -- Observers and transformers
14 -- (open to renaming suggestions here)
15 , blockId, zip, unzip, last, goto_end, zipht, tailOfLast
16 , splice_tail, splice_head, splice_head_only', splice_head'
17 , of_block_list, to_block_list
19 , postorder_dfs, postorder_dfs_from, postorder_dfs_from_except
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 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
102 be unique, acquiring one requires a monadic operation ('freshBlockId').
103 The primary advantage of the Graph representation is that we can build
104 a small Graph purely functionally, without entering a monad. For
105 example, during optimization we can easily rewrite a single middle
106 node into a Graph containing a sequence of two middle nodes followed by
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 -- | The string argument to 'freshBlockId' was originally helpful in debugging the Quick C--
170 -- compiler, so I have kept it here even though at present it is thrown away at
171 -- this spot---there's no reason a BlockId couldn't one day carry a string.
172 freshBlockId :: String -> UniqSM BlockId
174 blockId :: Block m l -> BlockId
175 zip :: ZBlock m l -> Block m l
176 unzip :: Block m l -> ZBlock m l
178 last :: ZBlock m l -> ZLast l
179 goto_end :: ZBlock m l -> (ZHead m, ZLast l)
181 tailOfLast :: l -> ZTail m l
183 -- | Take a head and tail and go to beginning or end. The asymmetry
184 -- in the types and names is a bit unfortunate, but 'Block m l' is
185 -- effectively '(BlockId, ZTail m l)' and is accepted in many more places.
187 ht_to_block, zipht :: ZHead m -> ZTail m l -> Block m l
188 ht_to_last :: ZHead m -> ZTail m l -> (ZHead m, ZLast l)
190 -- | We can splice a single-entry, single-exit LGraph onto a head or a tail.
191 -- For a head, we have a head 'h' followed by a LGraph 'g'.
192 -- The entry node of 'g' gets joined to 'h', forming the entry into
193 -- the new LGraph. The exit of 'g' becomes the new head.
194 -- For both arguments and results, the order of values is the order of
195 -- control flow: before splicing, the head flows into the LGraph; after
196 -- splicing, the LGraph flows into the head.
197 -- Splicing a tail is the dual operation.
198 -- (In order to maintain the order-means-control-flow convention, the
199 -- orders are reversed.)
201 -- For example, assume
203 -- grph = (M, [M: <stuff>,
205 -- N: y:=x; LastExit])
206 -- tail = [return (y,x)]
208 -- Then splice_head head grph
209 -- = ((L, [L: x:=0; goto M,
214 -- Then splice_tail grph tail
216 -- , (???, [<blocks>,
217 -- N: y:=x; return (y,x)])
219 splice_head :: ZHead m -> LGraph m l -> (LGraph m l, ZHead m)
220 splice_head' :: ZHead m -> Graph m l -> (BlockEnv (Block m l), ZHead m)
221 splice_tail :: Graph m l -> ZTail m l -> Graph m l
223 -- | We can also splice a single-entry, no-exit Graph into a head.
224 splice_head_only :: ZHead m -> LGraph m l -> LGraph m l
225 splice_head_only' :: ZHead m -> Graph m l -> LGraph m l
228 -- | A safe operation
230 -- | Conversion to and from the environment form is convenient. For
231 -- layout or dataflow, however, one will want to use 'postorder_dfs'
232 -- in order to get the blocks in an order that relates to the control
233 -- flow in the procedure.
234 of_block_list :: BlockId -> [Block m l] -> LGraph m l -- N log N
235 to_block_list :: LGraph m l -> [Block m l] -- N log N
237 -- | Traversal: 'postorder_dfs' returns a list of blocks reachable
238 -- from the entry node. This list has the following property:
240 -- Say a "back reference" exists if one of a block's
241 -- control-flow successors precedes it in the output list
243 -- Then there are as few back references as possible
245 -- The output is suitable for use in
246 -- a forward dataflow problem. For a backward problem, simply reverse
247 -- the list. ('postorder_dfs' is sufficiently tricky to implement that
248 -- one doesn't want to try and maintain both forward and backward
251 postorder_dfs :: LastNode l => LGraph m l -> [Block m l]
253 -- | For layout, we fold over pairs of 'Block m l' and 'Maybe BlockId'
254 -- in layout order. The 'Maybe BlockId', if present, identifies the
255 -- block that will be the layout successor of the current block. This
256 -- may be useful to help an emitter omit the final 'goto' of a block
257 -- that flows directly to its layout successor.
259 -- For example: fold_layout f z [ L1:B1, L2:B2, L3:B3 ]
260 -- = z <$> f (L1:B1) (Just L2)
261 -- <$> f (L2:B2) (Just L3)
262 -- <$> f (L3:B3) Nothing
263 -- where a <$> f = f a
265 LastNode l => (Block m l -> Maybe BlockId -> a -> a) -> a -> LGraph m l-> a
267 -- | We can also fold over blocks in an unspecified order. The
268 -- 'ZipCfgExtras' module provides a monadic version, which we
269 -- haven't needed (else it would be here).
270 fold_blocks :: (Block m l -> a -> a) -> a -> LGraph m l -> a
272 map_nodes :: (BlockId -> BlockId) -> (m -> m') -> (l -> l') -> LGraph m l -> LGraph m' l'
273 -- mapping includes the entry id!
275 -- | These translation functions are speculative. I hope eventually
276 -- they will be used in the native-code back ends ---NR
277 translate :: (m -> UniqSM (LGraph m' l')) ->
278 (l -> UniqSM (LGraph m' l')) ->
279 (LGraph m l -> UniqSM (LGraph m' l'))
282 -- | It's possible that another form of translation would be more suitable:
283 translateA :: (m -> Agraph m' l') -> (l -> AGraph m' l') -> LGraph m l -> LGraph m' l'
286 ------------------- Last nodes
288 -- | We can't make a graph out of just any old 'last node' type. A last node
289 -- has to be able to find its successors, and we need to be able to create and
290 -- identify unconditional branches. We put these capabilities in a type class.
291 -- Moreover, the property of having successors is also shared by 'Block's and
292 -- 'ZTails', so it is useful to have that property in a type class of its own.
294 class HavingSuccessors b where
295 succs :: b -> [BlockId]
296 fold_succs :: (BlockId -> a -> a) -> b -> a -> a
298 fold_succs add l z = foldr add z $ succs l
300 class HavingSuccessors l => LastNode l where
301 mkBranchNode :: BlockId -> l
302 isBranchNode :: l -> Bool
303 branchNodeTarget :: l -> BlockId -- panics if not branch node
304 -- ^ N.B. This interface seems to make for more congenial clients than a
305 -- single function of type 'l -> Maybe BlockId'
307 instance HavingSuccessors l => HavingSuccessors (ZLast l) where
309 succs (LastOther l) = succs l
310 fold_succs _ LastExit z = z
311 fold_succs f (LastOther l) z = fold_succs f l z
313 instance LastNode l => LastNode (ZLast l) where
314 mkBranchNode id = LastOther $ mkBranchNode id
315 isBranchNode LastExit = False
316 isBranchNode (LastOther l) = isBranchNode l
317 branchNodeTarget LastExit = panic "branchNodeTarget LastExit"
318 branchNodeTarget (LastOther l) = branchNodeTarget l
320 instance LastNode l => HavingSuccessors (ZBlock m l) where
321 succs b = succs (last b)
323 instance LastNode l => HavingSuccessors (Block m l) where
324 succs b = succs (unzip b)
326 instance LastNode l => HavingSuccessors (ZTail m l) where
327 succs b = succs (lastTail b)
331 -- ================ IMPLEMENTATION ================--
333 ----- block manipulations
335 blockId (Block id _) = id
337 freshBlockId _ = do { u <- getUniqueUs; return $ BlockId u }
339 -- | Convert block between forms.
340 -- These functions are tail-recursive, so we can go as deep as we like
341 -- without fear of stack overflow.
343 ht_to_block head tail = case head of
344 ZFirst id -> Block id tail
345 ZHead h m -> ht_to_block h (ZTail m tail)
347 ht_to_last head (ZLast l) = (head, l)
348 ht_to_last head (ZTail m t) = ht_to_last (ZHead head m) t
350 zipht h t = ht_to_block h t
351 zip (ZBlock h t) = ht_to_block h t
352 goto_end (ZBlock h t) = ht_to_last h t
354 unzip (Block id t) = ZBlock (ZFirst id) t
356 head_id :: ZHead m -> BlockId
357 head_id (ZFirst id) = id
358 head_id (ZHead h _) = head_id h
360 last (ZBlock _ t) = lastTail t
362 lastTail :: ZTail m l -> ZLast l
363 lastTail (ZLast l) = l
364 lastTail (ZTail _ t) = lastTail t
366 tailOfLast l = ZLast (LastOther l) -- ^ tedious to write in every client
369 ------------------ simple graph manipulations
371 focus :: BlockId -> LGraph m l -> FGraph m l -- focus on edge out of node with id
372 focus id (LGraph entry blocks) =
373 case lookupBlockEnv blocks id of
374 Just b -> FGraph entry (unzip b) (delFromUFM blocks id)
375 Nothing -> panic "asked for nonexistent block in flow graph"
377 entry :: LGraph m l -> FGraph m l -- focus on edge out of entry node
378 entry g@(LGraph eid _) = focus eid g
380 -- | pull out a block satisfying the predicate, if any
381 splitp_blocks :: (Block m l -> Bool) -> BlockEnv (Block m l) ->
382 Maybe (Block m l, BlockEnv (Block m l))
383 splitp_blocks p blocks = lift $ foldUFM scan (Nothing, emptyBlockEnv) blocks
384 where scan b (yes, no) =
386 Nothing | p b -> (Just b, no)
387 | otherwise -> (yes, insertBlock b no)
388 Just _ -> (yes, insertBlock b no)
389 lift (Nothing, _) = Nothing
390 lift (Just b, bs) = Just (b, bs)
392 -- | 'insertBlock' should not be used to *replace* an existing block
393 -- but only to insert a new one
394 insertBlock :: Block m l -> BlockEnv (Block m l) -> BlockEnv (Block m l)
396 ASSERT (isNothing $ lookupBlockEnv bs id)
397 extendBlockEnv bs id b
400 -- | Used in assertions; tells if a graph has exactly one exit
401 single_exit :: LGraph l m -> Bool
402 single_exit g = foldUFM check 0 (lg_blocks g) == 1
403 where check block count = case last (unzip block) of
404 LastExit -> count + (1 :: Int)
407 -- | Used in assertions; tells if a graph has exactly one exit
408 single_exitg :: Graph l m -> Bool
409 single_exitg (Graph tail blocks) = foldUFM add (exit_count (lastTail tail)) blocks == 1
410 where add block count = count + exit_count (last (unzip block))
411 exit_count LastExit = 1 :: Int
414 ------------------ graph traversals
416 -- | This is the most important traversal over this data structure. It drops
417 -- unreachable code and puts blocks in an order that is good for solving forward
418 -- dataflow problems quickly. The reverse order is good for solving backward
419 -- dataflow problems quickly. The forward order is also reasonably good for
420 -- emitting instructions, except that it will not usually exploit Forrest
421 -- Baskett's trick of eliminating the unconditional branch from a loop. For
422 -- that you would need a more serious analysis, probably based on dominators, to
423 -- identify loop headers.
425 -- The ubiquity of 'postorder_dfs' is one reason for the ubiquity of the 'LGraph'
426 -- representation, when for most purposes the plain 'Graph' representation is
427 -- more mathematically elegant (but results in more complicated code).
429 -- Here's an easy way to go wrong! Consider
433 -- Then ordinary dfs would give [A,B,D,C] which has a back ref from C to D.
434 -- Better to geot [A,B,C,D]
437 postorder_dfs' :: LastNode l => LGraph m l -> [Block m l]
438 postorder_dfs' g@(LGraph _ blocks) =
439 let FGraph _ eblock _ = entry g
440 in vnode (zip eblock) (\acc _visited -> acc) [] emptyBlockSet
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 vchildren block (get_children block) cont acc (extendBlockSet visited id)
449 vchildren block bs cont acc visited =
450 let next children acc visited =
451 case children of [] -> cont (block : acc) visited
452 (b:bs) -> vnode b (next bs) acc visited
453 in next bs acc visited
454 get_children block = foldl add_id [] (succs block)
455 add_id rst id = case lookupBlockEnv blocks id of
459 postorder_dfs g@(LGraph _ blockenv) =
460 let FGraph id eblock _ = entry g
462 postorder_dfs_from_except blockenv eblock (unitUniqSet id)
463 dfs2 = postorder_dfs' g
464 in ASSERT (map blockId dfs1 == map blockId dfs2) dfs2
467 :: (HavingSuccessors b, LastNode l) => BlockEnv (Block m l) -> b -> [Block m l]
468 postorder_dfs_from blocks b = postorder_dfs_from_except blocks b emptyBlockSet
470 postorder_dfs_from_except :: forall b m l . (HavingSuccessors b, LastNode l) => BlockEnv (Block m l) -> b -> BlockSet -> [Block m l]
471 postorder_dfs_from_except blocks b visited =
472 vchildren (get_children b) (\acc _visited -> acc) [] visited
475 -- Block m l -> ([Block m l] -> BlockSet -> a) -> [Block m l] -> BlockSet -> a
476 vnode block@(Block id _) cont acc visited =
477 if elemBlockSet id visited then
480 let cont' acc visited = cont (block:acc) visited in
481 vchildren (get_children block) cont' acc (extendBlockSet visited id)
482 vchildren bs cont acc visited =
483 let next children acc visited =
484 case children of [] -> cont acc visited
485 (b:bs) -> vnode b (next bs) acc visited
486 in next bs acc visited
487 get_children block = foldl add_id [] (succs block)
488 add_id rst id = case lookupBlockEnv blocks id of
493 -- | Slightly more complicated than the usual fold because we want to tell block
494 -- 'b1' what its inline successor is going to be, so that if 'b1' ends with
495 -- 'goto b2', the goto can be omitted.
497 fold_layout f z g@(LGraph eid _) = fold (postorder_dfs g) z
498 where fold blocks z =
499 case blocks of [] -> z
501 b1 : b2 : bs -> fold (b2 : bs) (f b1 (nextlabel b2) z)
502 nextlabel (Block id _) =
503 if id == eid then panic "entry as successor"
506 -- | The rest of the traversals are straightforward
508 map_nodes idm middle last (LGraph eid blocks) = LGraph (idm eid) (mapUFM block blocks)
509 where block (Block id t) = Block (idm id) (tail t)
510 tail (ZTail m t) = ZTail (middle m) (tail t)
511 tail (ZLast LastExit) = ZLast LastExit
512 tail (ZLast (LastOther l)) = ZLast (LastOther (last l))
514 fold_blocks f z (LGraph _ blocks) = foldUFM f z blocks
516 of_block_list e blocks = LGraph e $ foldr insertBlock emptyBlockEnv blocks
517 to_block_list (LGraph _ blocks) = eltsUFM blocks
522 -- We want to be able to scrutinize a single-entry, single-exit 'LGraph' for
523 -- splicing purposes. There are two useful cases: the 'LGraph' is a single block
524 -- or it isn't. We use continuation-passing style.
526 prepare_for_splicing ::
527 LGraph m l -> (ZTail m l -> a) -> (ZTail m l -> ZHead m -> BlockEnv (Block m l) -> a)
529 prepare_for_splicing g single multi =
530 let FGraph _ gentry gblocks = entry g
531 ZBlock _ etail = gentry
532 in if isNullUFM gblocks then
534 LastExit -> single etail
535 _ -> panic "bad single block"
537 case splitp_blocks is_exit gblocks of
538 Nothing -> panic "Can't find an exit block"
539 Just (gexit, gblocks) ->
540 let (gh, gl) = goto_end $ unzip gexit in
541 case gl of LastExit -> multi etail gh gblocks
542 _ -> panic "exit is not exit?!"
544 prepare_for_splicing' ::
545 Graph m l -> (ZTail m l -> a) -> (ZTail m l -> ZHead m -> BlockEnv (Block m l) -> a)
547 prepare_for_splicing' (Graph etail gblocks) single multi =
548 if isNullUFM gblocks then
549 case lastTail etail of
550 LastExit -> single etail
551 _ -> panic "bad single block"
553 case splitp_blocks is_exit gblocks of
554 Nothing -> panic "Can't find an exit block"
555 Just (gexit, gblocks) ->
556 let (gh, gl) = goto_end $ unzip gexit in
557 case gl of LastExit -> multi etail gh gblocks
558 _ -> panic "exit is not exit?!"
560 is_exit :: Block m l -> Bool
561 is_exit b = case last (unzip b) of { LastExit -> True; _ -> False }
564 ASSERT (single_exit g) prepare_for_splicing g splice_one_block splice_many_blocks
565 where eid = head_id head
566 splice_one_block tail' =
567 case ht_to_last head tail' of
568 (head, LastExit) -> (LGraph eid emptyBlockEnv, head)
569 _ -> panic "spliced LGraph without exit"
570 splice_many_blocks entry exit others =
571 (LGraph eid (insertBlock (zipht head entry) others), exit)
573 splice_head' head g =
574 ASSERT (single_exitg g) prepare_for_splicing' g splice_one_block splice_many_blocks
575 where splice_one_block tail' =
576 case ht_to_last head tail' of
577 (head, LastExit) -> (emptyBlockEnv, head)
578 _ -> panic "spliced LGraph without exit"
579 splice_many_blocks entry exit others =
580 (insertBlock (zipht head entry) others, exit)
582 -- splice_tail :: Graph m l -> ZTail m l -> Graph m l
584 ASSERT (single_exitg g) prepare_for_splicing' g splice_one_block splice_many_blocks
585 where splice_one_block tail' = Graph (tail' `append_tails` tail) emptyBlockEnv
586 append_tails (ZLast LastExit) tail = tail
587 append_tails (ZLast _) _ = panic "spliced single block without LastExit"
588 append_tails (ZTail m t) tail = ZTail m (append_tails t tail)
589 splice_many_blocks entry exit others =
590 Graph entry (insertBlock (zipht exit tail) others)
594 AS SERT (single_exit g) prepare_for_splicing g splice_one_block splice_many_blocks
595 where splice_one_block tail' = -- return tail' .. tail
596 case ht_to_last (ZFirst (lg_entry g)) tail' of
598 case ht_to_block head' tail of
599 Block id t | id == lg_entry g -> (t, LGraph id emptyBlockEnv)
600 _ -> panic "entry in; garbage out"
601 _ -> panic "spliced single block without Exit"
602 splice_many_blocks entry exit others =
603 (entry, LGraph (lg_entry g) (insertBlock (zipht exit tail) others))
606 splice_head_only head g =
607 let FGraph eid gentry gblocks = entry g
609 ZBlock (ZFirst _) tail -> LGraph eid (insertBlock (zipht head tail) gblocks)
610 _ -> panic "entry not at start of block?!"
612 splice_head_only' head (Graph tail gblocks) =
613 let eblock = zipht head tail in
614 LGraph (blockId eblock) (insertBlock eblock gblocks)
619 translate txm txl (LGraph eid blocks) =
620 do blocks' <- foldUFM txblock (return emptyBlockEnv) blocks
621 return $ LGraph eid blocks'
624 -- Block m l -> UniqSM (BlockEnv (Block m' l')) -> UniqSM (BlockEnv (Block m' l'))
625 txblock (Block id t) expanded =
626 do blocks' <- expanded
627 txtail (ZFirst id) t blocks'
628 -- txtail :: ZHead m' -> ZTail m l -> BlockEnv (Block m' l') ->
629 -- UniqSM (BlockEnv (Block m' l'))
630 txtail h (ZTail m t) blocks' =
632 let (g, h') = splice_head h m'
633 txtail h' t (plusUFM (lg_blocks g) blocks')
634 txtail h (ZLast (LastOther l)) blocks' =
636 return $ plusUFM (lg_blocks (splice_head_only h l')) blocks'
637 txtail h (ZLast LastExit) blocks' =
638 return $ insertBlock (zipht h (ZLast LastExit)) blocks'
640 ----------------------------------------------------------------
641 --- Block Ids, their environments, and their sets
643 {- Note [Unique BlockId]
644 ~~~~~~~~~~~~~~~~~~~~~~~~
645 Although a 'BlockId' is a local label, for reasons of implementation,
646 'BlockId's must be unique within an entire compilation unit. The reason
647 is that each local label is mapped to an assembly-language label, and in
648 most assembly languages allow, a label is visible throughout the enitre
649 compilation unit in which it appears.
652 newtype BlockId = BlockId Unique
655 instance Uniquable BlockId where
656 getUnique (BlockId u) = u
658 instance Show BlockId where
659 show (BlockId u) = show u
661 instance Outputable BlockId where
662 ppr = ppr . getUnique
665 type BlockEnv a = UniqFM {- BlockId -} a
666 emptyBlockEnv :: BlockEnv a
667 emptyBlockEnv = emptyUFM
668 lookupBlockEnv :: BlockEnv a -> BlockId -> Maybe a
669 lookupBlockEnv = lookupUFM
670 extendBlockEnv :: BlockEnv a -> BlockId -> a -> BlockEnv a
671 extendBlockEnv = addToUFM
672 mkBlockEnv :: [(BlockId,a)] -> BlockEnv a
673 mkBlockEnv = listToUFM
675 type BlockSet = UniqSet BlockId
676 emptyBlockSet :: BlockSet
677 emptyBlockSet = emptyUniqSet
678 elemBlockSet :: BlockId -> BlockSet -> Bool
679 elemBlockSet = elementOfUniqSet
680 extendBlockSet :: BlockSet -> BlockId -> BlockSet
681 extendBlockSet = addOneToUniqSet
682 mkBlockSet :: [BlockId] -> BlockSet
683 mkBlockSet = mkUniqSet
685 ----------------------------------------------------------------
687 ----------------------------------------------------------------
689 -- putting this code in PprCmmZ leads to circular imports :-(
691 instance (Outputable m, Outputable l) => Outputable (ZTail m l) where
694 pprTail :: (Outputable m, Outputable l) => ZTail m l -> SDoc
695 pprTail (ZTail m t) = ppr m $$ ppr t
696 pprTail (ZLast LastExit) = text "<exit>"
697 pprTail (ZLast (LastOther l)) = ppr l
699 pprLgraph :: (Outputable m, Outputable l, LastNode l) => LGraph m l -> SDoc
700 pprLgraph g = text "{" $$ nest 2 (vcat $ map pprBlock blocks) $$ text "}"
701 where pprBlock (Block id tail) = ppr id <> colon $$ ppr tail
702 blocks = postorder_dfs g
704 pprGraph :: (Outputable m, Outputable l, LastNode l) => Graph m l -> SDoc
705 pprGraph (Graph tail blockenv) =
706 text "{" $$ nest 2 (ppr tail $$ (vcat $ map pprBlock blocks)) $$ text "}"
707 where pprBlock (Block id tail) = ppr id <> colon $$ ppr tail
708 blocks = postorder_dfs_from blockenv tail
710 _unused :: FS.FastString