aboutsummaryrefslogtreecommitdiffstats
path: root/lib/hipe/regalloc/hipe_regalloc_prepass.erl
blob: 75f377fcce1466fd19019eba78fc2ecd323edcee (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
%% -*- erlang-indent-level: 2 -*-
%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2016. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%%     http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% %CopyrightEnd%
%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%@doc
%%	       PREPASS FOR ITERATED REGISTER ALLOCATORS
%%
%% Implements a trivial partial but optimal fast register allocator to be used
%% as the first pass of the register allocation loop.
%%
%% The idea is to drastically reduce the number of temporaries, so as to speed
%% up the real register allocators.
%%
%%  * Spills trivially unallocatable temps
%%    This relies on the fact that calls intentionally clobber all registers.
%%    Since this is the case, any temp that is alive over a call can't possibly
%%    be allocated to anything but a spill slot.
%%
%%  * Partitions the program at points where no pseudos that were not spiled are
%%    live, and then do register allocation on these partitions independently.
%%    These program points are commonly, but not exclusively, the call
%%    instructions.
%%
%% TODO
%%  * This module seems very successful at finding every single spill; register
%%    allocation performance should be improved if we short-circuit the first
%%    hipe_regalloc_loop iteration, skipping directly to rewrite without ever
%%    calling RegAllocMod.
-module(hipe_regalloc_prepass).
-export([regalloc/7, regalloc_initial/7]).

-ifndef(DEBUG).
-compile(inline).
-endif.

%%-define(DO_ASSERT, 1).
-include("../main/hipe.hrl").

%%% TUNABLES

%% Partitions with fewer than ?TUNE_TOO_FEW_BBS basic block halves are merged
%% together before register allocation.
-define(TUNE_TOO_FEW_BBS, 256).

%% Ignore the ra_partitioned option (and do whole function RA instead) when
%% there are fewer than ?TUNE_MIN_SPLIT_BBS basic blocks.
-define(TUNE_MIN_SPLIT_BBS, 384).

%% We present a "pseudo-target" to the register allocator we wrap.
%% Note: all arities are +1 as we're currently using the parameterised module
%% facility to store context data.
-export([analyze/2,
	 all_precoloured/1,
	 allocatable/1,
	 args/2,
	 bb/3,
	 def_use/2,
	 defines/2,
	 is_fixed/2,	% used by hipe_graph_coloring_regalloc
	 is_global/2,
	 is_move/2,
	 is_precoloured/2,
	 labels/2,
	 livein/3,
	 liveout/3,
	 non_alloc/2,
	 number_of_temporaries/2,
	 physical_name/2,
	 postorder/2,
	 reg_nr/2,
	 uses/2,
	 var_range/2,
	 reverse_postorder/2]).

%% Eww, parameterised module. Can we fix it without having to touch all the
%% register allocators?
-record(?MODULE,
	{target   :: module()
	,sub      :: sub_map() % Translates temp numbers found in CFG and understood by
			       % Target to temp numbers passed to RegAllocMod.
	,inv      :: inv_map() % Translates temp numbers passed to RegAllocMod
			       % to temp numbers found in CFG and understood by
			       % Target
	,max_phys :: temp()    % Exclusive upper bound on physical registers
	}).

-record(cfg,
	{cfg        :: target_cfg()
	,bbs        :: transformed_bbs()
	,max_reg    :: temp()    % Exclusive upper bound on temp numbers
	,rpostorder :: undefined % Only precomputed with partitioned cfg
		     | [label()]
	}).

-type bb()      :: hipe_bb:bb(). % containing instr()
-type liveset() :: ordsets:ordset(temp()).
-record(transformed_bb,
	{bb      :: bb()
	,livein  :: liveset()
	,liveout :: liveset()
	}).
-type transformed_bb() :: #transformed_bb{}.
-type transformed_bbs() :: #{label() => transformed_bb()}.

-record(instr,
	{defuse    :: {[temp()], [temp()]}
	,is_move   :: boolean()
	}).
-type instr() :: #instr{}.

-type target_cfg() :: any().
-type target_instr() :: any().
-type target_temp() :: any().
-type target_reg() :: non_neg_integer().
-type target_liveness() :: any().
-type target_liveset() :: ordsets:ordset(target_reg()).
-type spillno() :: non_neg_integer().
-type temp() :: non_neg_integer().
-type label() :: non_neg_integer().

-spec regalloc(module(), target_cfg(), target_liveness(), spillno(), spillno(),
	       module(), proplists:proplist())
	      -> {hipe_map(), spillno()}.
regalloc(RegAllocMod, CFG, Liveness, SpillIndex0, SpillLimit, Target,
	 Options) ->
  {Coloring, SpillIndex, same} =
    regalloc_1(RegAllocMod, CFG, SpillIndex0, SpillLimit, Target, Options,
	       Liveness),
  {Coloring, SpillIndex}.

%% regalloc_initial/7 is allowed to introduce new temporaries, unlike
%% regalloc/7.
%% In order for regalloc/7 to never introduce temporaries, regalloc/7 must never
%% choose to do split allocation unless regalloc_initial/7 does. This is the
%% reason that the splitting heuristic is solely based on the number of basic
%% blocks, which does not change during the register allocation loop.
-spec regalloc_initial(module(), target_cfg(), target_liveness(), spillno(),
		       spillno(), module(), proplists:proplist())
		      -> {hipe_map(), spillno(), target_cfg(),
			  target_liveness()}.
regalloc_initial(RegAllocMod, CFG0, Liveness0, SpillIndex0, SpillLimit, Target,
		 Options) ->
  {Coloring, SpillIndex, NewCFG} =
    regalloc_1(RegAllocMod, CFG0, SpillIndex0, SpillLimit, Target, Options,
	       Liveness0),
  {CFG, Liveness} =
    case NewCFG of
      same -> {CFG0, Liveness0};
      {rewritten, CFG1} -> {CFG1, Target:analyze(CFG1)}
    end,
  {Coloring, SpillIndex, CFG, Liveness}.

regalloc_1(RegAllocMod, CFG0, SpillIndex0, SpillLimit, Target, Options,
	   Liveness) ->
  {ScanBBs, Seen, SpillMap, SpillIndex1} =
    scan_cfg(CFG0, Liveness, SpillIndex0, Target),

  {PartColoring, SpillIndex, NewCFG} =
    case proplists:get_bool(ra_partitioned, Options)
      andalso length(Target:labels(CFG0)) > ?TUNE_MIN_SPLIT_BBS
    of
      true ->
	regalloc_partitioned(SpillMap, SpillIndex1, SpillLimit, ScanBBs,
			     CFG0, Target, RegAllocMod, Options);
      _ ->
	regalloc_whole(Seen, SpillMap, SpillIndex1, SpillLimit, ScanBBs,
		       CFG0, Target, RegAllocMod, Options)
    end,

  SpillColors = [{T, {spill, S}} || {T, S} <- maps:to_list(SpillMap)],
  Coloring = SpillColors ++ PartColoring,

  ?ASSERT(begin
	    AllPrecoloured = Target:all_precoloured(),
	    MaxPhys = lists:max(AllPrecoloured) + 1,
	    Unused = unused(live_pseudos(Seen, SpillMap, MaxPhys),
			    SpillMap, CFG0, Target),
	    unused_unused(Unused, CFG0, Target)
	  end),
  ?ASSERT(begin
	    CFG =
	      case NewCFG of
		same -> CFG0;
		{rewritten, CFG1} -> CFG1
	      end,
	    check_coloring(Coloring, CFG, Target)
	  end), % Sanity-check
  ?ASSERT(just_as_good_as(RegAllocMod, CFG, Liveness, SpillIndex0, SpillLimit,
			  Target, Options, SpillMap, Coloring, Unused)),
  {Coloring, SpillIndex, NewCFG}.

regalloc_whole(Seen, SpillMap, SpillIndex0, SpillLimit, ScanBBs,
	       CFG, Target, RegAllocMod, Options) ->
  AllPrecoloured = Target:all_precoloured(),
  MaxPhys = lists:max(AllPrecoloured) + 1,
  LivePseudos = live_pseudos(Seen, SpillMap, MaxPhys),
  {SubMap, InvMap, MaxPhys, MaxR, SubSpillLimit} =
    number_and_map(AllPrecoloured, LivePseudos, SpillLimit),
  BBs = transform_whole_cfg(ScanBBs, SubMap),
  SubMod = #cfg{cfg=CFG, bbs=BBs, max_reg=MaxR},
  SubTarget = #?MODULE{target=Target, max_phys=MaxPhys, inv=InvMap, sub=SubMap},
  {SubColoring, SpillIndex} =
    RegAllocMod:regalloc(SubMod, SubMod, SpillIndex0, SubSpillLimit, SubTarget,
			 Options),
  ?ASSERT(check_coloring(SubColoring, SubMod, SubTarget)),
  {translate_coloring(SubColoring, InvMap), SpillIndex, same}.

regalloc_partitioned(SpillMap, SpillIndex0, SpillLimit, ScanBBs,
		     CFG, Target, RegAllocMod, Options) ->
  AllPrecoloured = Target:all_precoloured(),
  MaxPhys = lists:max(AllPrecoloured) + 1,

  DSets0 = initial_dsets(CFG, Target),
  PartBBList = part_cfg(ScanBBs, SpillMap, MaxPhys),
  DSets1 = join_whole_blocks(PartBBList, DSets0),
  {PartBBsRLList, DSets2} = merge_small_parts(DSets1),
  {PartBBs, DSets3} = merge_pointless_splits(PartBBList, ScanBBs, DSets2),
  SeenMap = collect_seenmap(PartBBsRLList, PartBBs),
  {RPostMap, _DSets4} = part_order(Target:reverse_postorder(CFG), DSets3),

  {Allocations, SpillIndex} =
    lists:mapfoldl(
      fun({Root, Elems}, SpillIndex1) ->
	  #{Root := Seen} = SeenMap,
	  #{Root := RPost} = RPostMap,
	  LivePseudos = live_pseudos(Seen, SpillMap, MaxPhys),
	  {SubMap, InvMap, MaxPhys, MaxR, SubSpillLimit} =
	    number_and_map(AllPrecoloured, LivePseudos, SpillLimit),
	  BBs = transform_cfg(Elems, PartBBs, SubMap),
	  SubMod = #cfg{cfg=CFG, bbs=BBs, max_reg=MaxR, rpostorder=RPost},
	  SubTarget = #?MODULE{target=Target, max_phys=MaxPhys, inv=InvMap,
			       sub=SubMap},
	  {SubColoring, SpillIndex2} =
	    RegAllocMod:regalloc(SubMod, SubMod, SpillIndex1, SubSpillLimit,
				 SubTarget, Options),
	  ?ASSERT(check_coloring(SubColoring, SubMod, SubTarget)),
	  {{translate_coloring(SubColoring, InvMap), Elems}, SpillIndex2}
      end, SpillIndex0, PartBBsRLList),
  {Coloring, NewCFG} =
    combine_allocations(Allocations, MaxPhys, PartBBs, Target, CFG),
  {Coloring, SpillIndex, NewCFG}.

-spec number_and_map([target_reg()], target_liveset(), target_reg())
		    -> {sub_map(), inv_map(), temp(), temp(), temp()}.
number_and_map(Phys, Pseud, SpillLimit) ->
  MaxPhys = lists:max(Phys) + 1,
  ?ASSERT(Pseud =:= [] orelse lists:min(Pseud) >= MaxPhys),
  NrPseuds = length(Pseud),
  MaxR = MaxPhys+NrPseuds,
  PseudNrs = lists:zip(Pseud, lists:seq(MaxPhys, MaxR-1)),
  MapList = lists:zip(Phys, Phys) % Physicals are identity-mapped
    ++ PseudNrs,
  ?ASSERT(MapList =:= lists:ukeysort(1, MapList)),
  SubMap = {s,maps:from_list(MapList)},
  InvMap = {i,maps:from_list([{Fake, Real} || {Real, Fake} <- MapList])},
  SubSpillLimit = translate_spill_limit(MapList, SpillLimit),
  {SubMap, InvMap, MaxPhys, MaxR, SubSpillLimit}.

-spec translate_spill_limit([{target_reg(), temp()}], target_reg()) -> temp().
translate_spill_limit([{Real,Fake}], SpillLimit) when Real < SpillLimit ->
  Fake + 1;
translate_spill_limit([{Real,_}|Ps], SpillLimit) when Real < SpillLimit ->
  translate_spill_limit(Ps, SpillLimit);
translate_spill_limit([{Real,Fake}|_], SpillLimit) when Real >= SpillLimit ->
  Fake.

-spec live_pseudos(seen(), spill_map(), target_reg()) -> target_liveset().
live_pseudos(Seen, SpillMap, MaxPhys) ->
  %% When SpillMap is much larger than Seen (which is typical in the partitioned
  %% case), it is much more efficient doing it like this than making an ordset
  %% of the spills and subtracting.
  ordsets:from_list(
    lists:filter(fun(R) -> R >= MaxPhys andalso not maps:is_key(R, SpillMap)
		 end, maps:keys(Seen))).

-spec translate_coloring(hipe_map(), inv_map()) -> hipe_map().
translate_coloring(SubColoring, InvMap) ->
  lists:map(fun({T, P}) -> {imap_get(T, InvMap), P} end, SubColoring).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% First pass
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Spill trivially unallocatable temps, create internal target-independent
%% program representation, and collect a set of all used temps.
-record(spill_state,
	{map :: spill_map()
	,ix  :: spillno()
	}).
-type spill_state() :: #spill_state{}.
-type spill_map()   :: #{target_reg() => spillno()}.

-spec scan_cfg(target_cfg(), target_liveness(), spillno(), module())
	      -> {scan_bbs()
		 ,seen()
		 ,spill_map()
		 ,spillno()
		 }.
scan_cfg(CFG, Liveness, SpillIndex0, Target) ->
  State0 = #spill_state{map=#{}, ix=SpillIndex0},
  {BBs, Seen, #spill_state{map=Spill, ix=SpillIndex}} =
    scan_bbs(Target:labels(CFG), CFG, Liveness, #{}, State0, #{}, Target),
  {BBs, Seen, Spill, SpillIndex}.

-type seen() :: #{target_reg() => []}. % set
-type scan_bb() :: {[instr()], target_liveset(), target_liveset()}.
-type scan_bbs() :: #{label() => scan_bb()}.

-spec scan_bbs([label()], target_cfg(), target_liveness(), seen(),
	       spill_state(), scan_bbs(), module())
	      -> {scan_bbs(), seen(), spill_state()}.
scan_bbs([], _CFG, _Liveness, Seen, State, BBs, _Target) ->
  {BBs, Seen, State};
scan_bbs([L|Ls], CFG, Liveness, Seen0, State0, BBs, Target) ->
  Liveout = t_liveout(Liveness, L, Target),
  {Code, Livein, Seen, State} =
    scan_bb(lists:reverse(hipe_bb:code(Target:bb(CFG, L))), Liveout, Seen0,
	    State0, [], Target),
  BB = {Code, Livein, Liveout},
  scan_bbs(Ls, CFG, Liveness, Seen, State, BBs#{L=>BB}, Target).

-spec scan_bb([target_instr()], target_liveset(), seen(), spill_state(),
	      [instr()], module())
	     -> {[instr()]
		,target_liveset()
		,seen()
		,spill_state()
		}.
scan_bb([], Live, Seen, State, IAcc, _Target) ->
  {IAcc, Live, Seen, State};
scan_bb([I|Is], Live0, Seen0, State0, IAcc0, Target) ->
  {TDef, TUse} = Target:def_use(I),
  ?ASSERT(TDef =:= Target:defines(I)),
  ?ASSERT(TUse =:= Target:uses(I)),
  Def = ordsets:from_list(reg_names(TDef, Target)),
  Use = ordsets:from_list(reg_names(TUse, Target)),
  Live = ordsets:union(Use, ToSpill = ordsets:subtract(Live0, Def)),
  Seen = add_seen(Def, add_seen(Use, Seen0)),
  NewI = #instr{defuse={Def, Use}, is_move=Target:is_move(I)},
  IAcc = [NewI|IAcc0],
  State =
    case Target:defines_all_alloc(I) of
      false -> State0;
      true -> spill_all(ToSpill, Target, State0)
    end,
  %% We can drop "no-ops" here; where (if anywhere) is it worth it?
  scan_bb(Is, Live, Seen, State, IAcc, Target).

-spec t_liveout(target_liveness(), label(), module()) -> target_liveset().
t_liveout(Liveness, L, Target) ->
  %% FIXME: unnecessary sort; liveout is sorted, reg_names(...) should be sorted
  %% or consist of a few sorted subsequences (per type)
  ordsets:from_list(reg_names(Target:liveout(Liveness, L), Target)).

-spec reg_names([target_temp()], module()) -> [target_reg()].
reg_names(Regs, Target) ->
  [Target:reg_nr(X) || X <- Regs].

-spec add_seen([target_reg()], seen()) -> seen().
add_seen([], Seen) -> Seen;
add_seen([R|Rs], Seen) -> add_seen(Rs, Seen#{R=>[]}).

-spec spill_all([target_reg()], module(), spill_state()) -> spill_state().
spill_all([], _Target, State) -> State;
spill_all([R|Rs], Target, State=#spill_state{map=Map, ix=Ix}) ->
  case Target:is_precoloured(R) or maps:is_key(R, Map) of
    true -> spill_all(Rs, Target, State);
    false -> spill_all(Rs, Target, State#spill_state{map=Map#{R=>Ix}, ix=Ix+1})
  end.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Second pass (without split)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Rewrite CFG to the new temp names.
-spec transform_whole_cfg(scan_bbs(), sub_map()) -> transformed_bbs().
transform_whole_cfg(BBs0, SubMap) ->
  maps:map(fun(_, BB) -> transform_whole_bb(BB, SubMap) end, BBs0).

-spec transform_whole_bb(scan_bb(), sub_map()) -> transformed_bb().
transform_whole_bb({Code, Livein, Liveout}, SubMap) ->
  #transformed_bb{
     bb=hipe_bb:mk_bb([I#instr{defuse={smap_get_all_partial(Def, SubMap),
				       smap_get_all_partial(Use, SubMap)}}
		       || I = #instr{defuse={Def,Use}} <- Code])
     %% Assume mapping preserves monotonicity
    ,livein=smap_get_all_partial(Livein, SubMap)
    ,liveout=smap_get_all_partial(Liveout, SubMap)
    }.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Second pass (with split)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Discover program partitioning
%% Regretfully, this needs to be a separate pass, as having the global live set
%% is crucial to get a useful partitioning.

%% Single-block parts are merged if there are multiple in a single block, as it
%% is judged to not be beneficial to make them too small.

-type part_bb_part() :: {[instr()], target_liveset(), target_liveset()}.
-type part_bb()  :: {single, part_bb_part()}
		  | {split, part_bb_part(), part_bb_part()}.
-type part_bb_list() :: [{label(), part_bb()}].
-type part_bbs() :: #{label() => part_bb()}.
-type part_bb_sofar() :: single
		       | {split, [instr()], target_liveset()}. % , target_liveset()

-spec part_cfg(scan_bbs(), spill_map(), target_reg()) -> part_bb_list().
part_cfg(ScanBBs, SpillMap, MaxPhys) ->
  Liveset = mk_part_liveset(SpillMap, MaxPhys),
  lists:map(fun(BB) -> part_bb(BB, Liveset) end, maps:to_list(ScanBBs)).

-spec part_bb({label(), scan_bb()}, part_liveset()) -> {label(), part_bb()}.
part_bb({L, BB0={Code0, Livein, Liveout}}, Liveset) ->
  {Sofar, NewCode} = part_bb_1(lists:reverse(Code0), Liveset, Liveout, []),
  BB = case Sofar of
	 single ->
	   ?ASSERT(Code0 =:= NewCode),
	   {single, BB0};
	 {split, ExitCode, ExitLivein = EntryLiveout} ->
	   {split, {NewCode, Livein, EntryLiveout},
	    {ExitCode, ExitLivein, Liveout}}
       end,
  {L, BB}.

-spec part_bb_1([instr()], part_liveset(), target_liveset(), [instr()])
	     -> {part_bb_sofar(), [instr()]}.
part_bb_1([], _Liveset, _Livein, IAcc) -> {single, IAcc};
part_bb_1([I=#instr{defuse={Def,Use}}|Is], Liveset, Live0, IAcc0) ->
  Live = ordsets:union(Use, ordsets:subtract(Live0, Def)),
  IAcc = [I|IAcc0],
  case part_none_live(Live, Liveset) of
    false -> part_bb_1(Is, Liveset, Live, IAcc);
    %% One split point will suffice
    true -> {{split, IAcc, Live}, lists:reverse(Is)}
  end.

-spec part_none_live(target_liveset(), part_liveset()) -> boolean().
part_none_live(Live, Liveset) ->
  not lists:any(fun(R) -> part_liveset_is_live(R, Liveset) end, Live).

-type part_liveset() :: {spill_map(), target_reg()}.

-spec mk_part_liveset(spill_map(), target_reg()) -> part_liveset().
mk_part_liveset(SpillMap, MaxPhys) -> {SpillMap, MaxPhys}.

-spec part_liveset_is_live(target_reg(), part_liveset()) -> boolean().
part_liveset_is_live(R, {SpillMap, MaxPhys}) when is_integer(R) ->
  R >= MaxPhys andalso not maps:is_key(R, SpillMap).

%% @doc Merges split blocks where entry and exit belong to the same DSet.
%% Does not change DSets
-spec merge_pointless_splits(part_bb_list(), scan_bbs(), bb_dsets())
			   -> {part_bbs(), bb_dsets()}.
merge_pointless_splits(PartBBList0, ScanBBs, DSets0) ->
  {PartBBList, DSets} =
    merge_pointless_splits_1(PartBBList0, ScanBBs, DSets0, []),
  {maps:from_list(PartBBList), DSets}.

-spec merge_pointless_splits_1(
	part_bb_list(), scan_bbs(), bb_dsets(), part_bb_list())
			      -> {part_bb_list(), bb_dsets()}.
merge_pointless_splits_1([], _ScanBBs, DSets, Acc) -> {Acc, DSets};
merge_pointless_splits_1([P={_,{single,_}}|Ps], ScanBBs, DSets, Acc) ->
  merge_pointless_splits_1(Ps, ScanBBs, DSets, [P|Acc]);
merge_pointless_splits_1([P0={L,{split,_,_}}|Ps], ScanBBs, DSets0, Acc) ->
  {EntryRoot, DSets1} = dsets_find({entry,L}, DSets0),
  {ExitRoot,  DSets}  = dsets_find({exit,L},  DSets1),
  case EntryRoot =:= ExitRoot of
    false -> merge_pointless_splits_1(Ps, ScanBBs, DSets, [P0|Acc]);
    true ->
      %% Reuse the code list from ScanBBs rather than concatenating the split
      %% parts
      #{L := BB} = ScanBBs,
      ?ASSERT(begin
		{L,{split,{_EntryCode,_,_},{_ExitCode,_,_}}}=P0, % [_|
		{_Code,_,_}=BB,
		_Code =:= (_EntryCode ++ _ExitCode)
	      end),
      merge_pointless_splits_1(Ps, ScanBBs, DSets, [{L,{single, BB}}|Acc])
  end.

-spec merge_small_parts(bb_dsets()) -> {bb_dsets_rllist(), bb_dsets()}.
merge_small_parts(DSets0) ->
  {RLList, DSets1} = dsets_to_rllist(DSets0),
  RLLList = [{R, length(Elems), Elems} || {R, Elems} <- RLList],
  merge_small_parts_1(RLLList, DSets1, []).

-spec merge_small_parts_1(
	[{bb_dset_key(), non_neg_integer(), [bb_dset_key()]}],
	bb_dsets(), bb_dsets_rllist()
       ) -> {bb_dsets_rllist(), bb_dsets()}.
merge_small_parts_1([], DSets, Acc) -> {Acc, DSets};
merge_small_parts_1([{R, _, Es}], DSets, Acc) -> {[{R, Es}|Acc], DSets};
merge_small_parts_1([{R, L, Es}|Ps], DSets, Acc) when L >= ?TUNE_TOO_FEW_BBS ->
  merge_small_parts_1(Ps, DSets, [{R,Es}|Acc]);
merge_small_parts_1([Fst,{R, L, Es}|Ps], DSets, Acc)
  when L >= ?TUNE_TOO_FEW_BBS ->
  merge_small_parts_1([Fst|Ps], DSets, [{R,Es}|Acc]);
merge_small_parts_1([{R1,L1,Es1},{R2,L2,Es2}|Ps], DSets0, Acc) ->
  ?ASSERT(L1 < ?TUNE_TOO_FEW_BBS andalso L2 < ?TUNE_TOO_FEW_BBS),
  DSets1 = dsets_union(R1, R2, DSets0),
  {R, DSets} = dsets_find(R1, DSets1),
  merge_small_parts_1([{R,L2+L1,Es2++Es1}|Ps], DSets, Acc).

%% @doc Partition an ordering over BBs into subsequences for the dsets that
%% contain them.
%% Does not change dsets.
-spec part_order([label()], bb_dsets())
		-> {#{bb_dset_key() => [label()]}, bb_dsets()}.
part_order(Lbs, DSets) -> part_order(Lbs, DSets, #{}).

part_order([], DSets, Acc) -> {Acc, DSets};
part_order([L|Ls], DSets0, Acc0) ->
  {EntryRoot, DSets1} = dsets_find({entry,L}, DSets0),
  {ExitRoot,  DSets2} = dsets_find({exit,L},  DSets1),
  Acc1 = map_append(EntryRoot, L, Acc0),
  %% Only include the label once if both entry and exit is in same partition
  Acc2 = case EntryRoot =:= ExitRoot of
	   true -> Acc1;
	   false -> map_append(ExitRoot, L, Acc1)
	 end,
  part_order(Ls, DSets2, Acc2).

map_append(Key, Elem, Map) ->
  case Map of
    #{Key := List} -> Map#{Key := [Elem|List]};
    #{} -> Map#{Key => [Elem]}
  end.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Interference graph partitioning
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% We partition the program

%% The algorithm considers two kinds of components; those that are local to a
%% basic block, and those that are not. The key is that any basic block belongs
%% to at most two non-local components; one from the beginning to the first
%% split point, and one from the end to the last split point.

-type bb_dset_key() :: {entry | exit, label()}.
-type bb_dsets() :: dsets(bb_dset_key()).
-type bb_dsets_rllist() :: [{bb_dset_key(), [bb_dset_key()]}].

-spec initial_dsets(target_cfg(), module()) -> bb_dsets().
initial_dsets(CFG, Target) ->
  Labels = Target:labels(CFG),
  DSets0 = dsets_new(lists:append([[{entry,L},{exit,L}] || L <- Labels])),
  Edges = lists:append([[{L, S} || S <- hipe_gen_cfg:succ(CFG, L)]
			|| L <- Labels]),
  lists:foldl(fun({X, Y}, DS) -> dsets_union({exit,X}, {entry,Y}, DS) end,
	      DSets0, Edges).

-spec join_whole_blocks(part_bb_list(), bb_dsets()) -> bb_dsets().
join_whole_blocks(PartBBList, DSets0) ->
  lists:foldl(fun({L, {single, _}}, DS) -> dsets_union({entry,L}, {exit,L}, DS);
		 ({_, {split, _, _}}, DS) -> DS
	      end, DSets0, PartBBList).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% The disjoint set forests data structure, for elements of arbitrary types.
%% Note that the find operation mutates the set.
%%
%% We could do this more efficiently if we restricted the elements to integers,
%% and used the (mutable) hipe arrays. For arbitrary terms ETS could be used,
%% for a persistent interface (which isn't that nice when even accessors return
%% modified copies), the array module could be used.
-type dsets(X) :: #{X => {node, X} | {root, non_neg_integer()}}.

-spec dsets_new([E]) -> dsets(E).
dsets_new(Elems) -> maps:from_list([{E,{root,0}} || E <- Elems]).

-spec dsets_find(E, dsets(E)) -> {E, dsets(E)}.
dsets_find(E, DS0) ->
  case DS0 of
    #{E := {root,_}} -> {E, DS0};
    #{E := {node,N}} ->
      case dsets_find(N, DS0) of
	{N, _}=T -> T;
	{R, DS1} -> {R, DS1#{E := {node,R}}}
      end
   ;_ -> error(badarg, [E, DS0])
  end.

-spec dsets_union(E, E, dsets(E)) -> dsets(E).
dsets_union(X, Y, DS0) ->
  {XRoot, DS1} = dsets_find(X, DS0),
  case dsets_find(Y, DS1) of
    {XRoot, DS2} -> DS2;
    {YRoot, DS2} ->
      #{XRoot := {root,XRR}, YRoot := {root,YRR}} = DS2,
      if XRR < YRR -> DS2#{XRoot := {node,YRoot}};
	 XRR > YRR -> DS2#{YRoot := {node,XRoot}};
	 true -> DS2#{YRoot := {node,XRoot}, XRoot := {root,XRR+1}}
      end
  end.

-spec dsets_to_rllist(dsets(E)) -> {[{Root::E, Elems::[E]}], dsets(E)}.
dsets_to_rllist(DS0) ->
  {Lists, DS} = dsets_to_rllist(maps:keys(DS0), #{}, DS0),
  {maps:to_list(Lists), DS}.

dsets_to_rllist([], Acc, DS) -> {Acc, DS};
dsets_to_rllist([E|Es], Acc, DS0) ->
  {ERoot, DS} = dsets_find(E, DS0),
  dsets_to_rllist(Es, map_append(ERoot, E, Acc), DS).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Third pass
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Collect all referenced temps in each partition.

%% Note: The temps could be collected during the partition pass for each
%% half-bb, and then combined here. Would that be beneficial?

collect_seenmap(PartBBsRLList, PartBBs) ->
  collect_seenmap(PartBBsRLList, #{}, PartBBs).

collect_seenmap([], Acc, _PartBBs) -> Acc;
collect_seenmap([{R,Elems}|Ps], Acc, PartBBs) ->
  Seen = collect_seen_part(Elems, #{}, PartBBs),
  collect_seenmap(Ps, Acc#{R => Seen}, PartBBs).

collect_seen_part([], Acc, _PartBBs) -> Acc;
collect_seen_part([{Half,L}|Es], Acc0, PartBBs) ->
  BB = maps:get(L, PartBBs),
  Code = case {Half, BB} of
	   {entry, {single, {C,_,_}}} -> C;
	   {entry, {split, {C,_,_}, _}} -> C;
	   {exit,  {split, _, {C,_,_}}} -> C;
	   {exit,  {single, _}} -> [] % Ignore; was collected by its entry half
	 end,
  Acc = collect_seen_code(Code, Acc0),
  collect_seen_part(Es, Acc, PartBBs).

collect_seen_code([], Acc) -> Acc;
collect_seen_code([#instr{defuse={Def,Use}}|Is], Acc) ->
  collect_seen_code(Is, add_seen(Def, add_seen(Use, Acc))).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Fourth pass
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Rewrite CFG to the new temp names.
-spec transform_cfg([bb_dset_key()], part_bbs(), sub_map()) -> transformed_bbs().

transform_cfg(Elems, PartBBs, SubMap) ->
  transform_cfg(Elems, PartBBs, SubMap, #{}).

transform_cfg([], _PartBBs, _SubMap, Acc) -> Acc;
transform_cfg([{Half,L}|Es], PartBBs, SubMap, Acc0) ->
  #{L := PBB} = PartBBs,
  Acc = case {Half, PBB} of
	  {entry, {single,BB}}  -> Acc0#{L=>transform_bb(BB, SubMap)};
	  {entry, {split,BB,_}} -> Acc0#{L=>transform_bb(BB, SubMap)};
	  {exit,  {split,_,BB}} -> Acc0#{L=>transform_bb(BB, SubMap)};
	  {exit,  {single, _}}  -> Acc0 % Was included by the entry half
	end,
  transform_cfg(Es, PartBBs, SubMap, Acc).

-spec transform_bb(part_bb_part(), sub_map()) -> transformed_bb().
transform_bb(BB, SubMap) ->
  %% For now, part_bb_part() and split_bb() share representation
  transform_whole_bb(BB, SubMap).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Fifth pass
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Combine colorings and substitute temps in actual cfg if there were
%% collisions.

%% A temp can sometimes appear in more than one partition. For example, defining
%% an unused value. If these are found by combine_allocations, we have to
%% rename this temp in one of the partitions on the real cfg.
%%
%% We optimistically assume that there will be no such collisions, and when
%% there are, we fix them up as they're found.

-spec combine_allocations([{hipe_map(), [bb_dset_key()]}], target_reg(),
			  part_bbs(), module(), target_cfg())
			 -> {hipe_map(), same | {rewritten, target_cfg()}}.
combine_allocations([{A,_}|As], MaxPhys, PartBBs, Target, CFG) ->
  {Phys, Pseuds} = lists:partition(fun({R,_}) -> R < MaxPhys end, A),
  {Seen, _, []} = partition_by_seen(Pseuds, #{}, [], []),
  combine_allocations(As, MaxPhys, PartBBs, Target, Phys, Seen, Pseuds,
		      {same, CFG}).

-spec combine_allocations([{hipe_map(), [bb_dset_key()]}], target_reg(),
			  part_bbs(), module(), hipe_map(), seen(), hipe_map(),
			  {same|rewritten, target_cfg()})
			 -> {hipe_map(), same | {rewritten, target_cfg()}}.
combine_allocations([], _MaxPhys, _PartBBs, _Target, Phys, _Seen, Pseuds,
		    CFGT) ->
  {Phys ++ Pseuds, case CFGT of
		     {same, _} -> same;
		     {rewritten, _} -> CFGT
		   end};
combine_allocations([{A,PartElems}|As], MaxPhys, PartBBs, Target, Phys, Seen0,
		    Acc, CFGT={_,CFG0}) ->
  {Phys, Pseuds0} = lists:partition(fun({R,_}) -> R < MaxPhys end, A),
  {Seen, Pseuds, Collisions} = partition_by_seen(Pseuds0, Seen0, [], []),
  case Collisions of
    [] -> combine_allocations(As, MaxPhys, PartBBs, Target, Phys, Seen,
			      Pseuds++Acc, CFGT);
    _ ->
      %% There were collisions; rename all the temp numbers in Collisions
      {CFG, Renamed} = rename(Collisions, PartElems, PartBBs, Target, CFG0),
      combine_allocations(As, MaxPhys, PartBBs, Target, Phys, Seen,
			  Pseuds++Renamed++Acc, {rewritten,CFG})
  end.

%% @doc Partitions a coloring on whether the registers are in the Seen set,
%% adding any new registers to the set.
-spec partition_by_seen(hipe_map(), seen(), hipe_map(), hipe_map())
		       -> {seen(), hipe_map(), hipe_map()}.
partition_by_seen([], Seen, Acc, Collisions) -> {Seen, Acc, Collisions};
partition_by_seen([C={R,_}|Cs], Seen, Acc, Colls) ->
  case Seen of
    #{R := _} -> partition_by_seen(Cs, Seen, Acc, [C|Colls]);
    #{}       -> partition_by_seen(Cs, Seen#{R => []}, [C|Acc], Colls)
  end.

-spec rename(hipe_map(), [bb_dset_key()], part_bbs(), module(), target_cfg())
	    -> {target_cfg(), hipe_map()}.
rename(CollisionList, PartElems, PartBBs, Target, CFG0) ->
  {Map, Renamed} = new_names(CollisionList, Target, #{}, []),
  Fun = fun(I) ->
	    Target:subst_temps(
	      fun(Temp) ->
		  N = Target:reg_nr(Temp),
		  case Map of
		    #{N := Subst} -> Target:update_reg_nr(Subst, Temp);
		    #{} -> Temp
		  end
	      end, I)
	end,
  {rename_1(PartElems, PartBBs, Target, Fun, CFG0), Renamed}.

-type rename_map() :: #{target_reg() => target_reg()}.
-type rename_fun() :: fun((target_instr()) -> target_instr()).

-spec new_names(hipe_map(), module(), rename_map(), hipe_map())
	       -> {rename_map(), hipe_map()}.
new_names([], _Target, Map, Renamed) -> {Map, Renamed};
new_names([{R,C}|As], Target, Map, Renamed) ->
  Subst = Target:new_reg_nr(),
  new_names(As, Target, Map#{R => Subst}, [{Subst, C} | Renamed]).

%% @doc Maps over all instructions in a partition on the original CFG.
-spec rename_1([bb_dset_key()], part_bbs(), module(), rename_fun(),
	       target_cfg()) -> target_cfg().
rename_1([], _PartBBs, _Target, _Fun, CFG) -> CFG;
rename_1([{Half,L}|Es], PartBBs, Target, Fun, CFG0) ->
  Code0 = hipe_bb:code(BB = Target:bb(CFG0, L)),
  Code = case {Half, maps:get(L, PartBBs)} of
	  {entry, {single,_}} -> lists:map(Fun, Code0);
	  {entry, {split,PBBP,_}} ->
	     map_start(Fun, part_bb_part_len(PBBP), Code0);
	  {exit, {split,_,PBBP}} ->
	     map_end(Fun, part_bb_part_len(PBBP), Code0);
	  {exit, {single, _}} -> Code0
	end,
  CFG = Target:update_bb(CFG0, L, hipe_bb:code_update(BB, Code)),
  rename_1(Es, PartBBs, Target, Fun, CFG).

-spec part_bb_part_len(part_bb_part()) -> non_neg_integer().
part_bb_part_len({Code, _Livein, _Liveout}) -> length(Code).

%% @doc Map the first N elements of a list
-spec map_start(fun((X) -> Y), non_neg_integer(), [X]) -> [X|Y].
map_start(_Fun, 0, List) -> List;
map_start(Fun, N, [E|Es]) ->
  [Fun(E)|map_start(Fun, N-1, Es)].

%% @doc Map the last N elements of a list
-spec map_end(fun((X) -> Y), non_neg_integer(), [X]) -> [X|Y].
map_end(Fun, N, List) ->
  map_end(Fun, N, length(List), List).

map_end(Fun, N, Len, [E|Es]) when Len > N -> [E|map_end(Fun, N, Len-1, Es)];
map_end(Fun, N, Len, List) when Len =:= N -> lists:map(Fun, List).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Temp map ADT
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-type sub_map() :: {s,#{target_reg() => temp()}}.
-type inv_map() :: {i,#{temp() => target_reg()}}.

-spec smap_get(target_reg(), sub_map()) -> temp().
smap_get(Temp, {s,Map}) when is_integer(Temp) -> maps:get(Temp, Map).

-spec imap_get(temp(), inv_map()) -> target_reg().
imap_get(Temp, {i,Map}) when is_integer(Temp) -> maps:get(Temp, Map).

-spec smap_get_all_partial([target_reg()], sub_map()) -> [temp()].
smap_get_all_partial([], _) -> [];
smap_get_all_partial([T|Ts], SMap={s,Map}) when is_integer(T) ->
  case Map of
    #{T := R} -> [R|smap_get_all_partial(Ts, SMap)];
    #{} -> smap_get_all_partial(Ts, SMap)
  end.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Validation
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-ifdef(DO_ASSERT).
%%%%%%%%%%%%%%%%%%%%
%% Check that the coloring is correct (if the IG is correct):
%%

%% Define these as 'ok' or 'report(X,Y)' depending on how much output you want.
-define(report0(X,Y), ?IF_DEBUG_LEVEL(0,?msg(X, Y),ok)).
-define(report(X,Y),  ?IF_DEBUG_LEVEL(1,?msg(X, Y),ok)). 
-define(report2(X,Y), ?IF_DEBUG_LEVEL(2,?msg(X, Y),ok)). 
-define(report3(X,Y), ?IF_DEBUG_LEVEL(3,?msg(X, Y),ok)).

check_coloring(Coloring, CFG, Target) ->
  ?report0("checking coloring ~p~n",[Coloring]),
  IG = hipe_ig:build(CFG, Target:analyze(CFG), Target),
  check_cols(hipe_vectors:list(hipe_ig:adj_list(IG)),
	     init_coloring(Coloring, Target)).

init_coloring(Xs, Target) ->
  hipe_temp_map:cols2tuple(Xs, Target).

check_color_of(X, Cols) ->
  case hipe_temp_map:find(X, Cols) of
    unknown ->
      uncolored;
    C ->
      C
  end.

check_cols([], _Cols) ->
  ?report("coloring valid~n",[]),
  true;
check_cols([{X,Neighbours}|Xs], Cols) ->
  Cs = [{N, check_color_of(N, Cols)} || N <- Neighbours],
  C = check_color_of(X, Cols),
  case valid_coloring(X, C, Cs) of
    yes ->
      check_cols(Xs, Cols);
    {no,Invalids} ->
      ?msg("node ~p has same color (~p) as ~p~n", [X,C,Invalids]),
      check_cols(Xs, Cols) andalso false
  end.

valid_coloring(_X, _C, []) ->
  yes;
valid_coloring(X, C, [{Y,C}|Ys]) ->
  case valid_coloring(X, C, Ys) of
    yes -> {no, [Y]};
    {no,Zs} -> {no, [Y|Zs]}
  end;
valid_coloring(X, C, [_|Ys]) ->
  valid_coloring(X, C, Ys).

unused_unused(Unused, CFG, Target) ->
  IG = hipe_ig:build(CFG, Target:analyze(CFG), Target),
  lists:all(fun(R) -> case hipe_ig:get_node_degree(R, IG) of
			0 -> true;
			Deg ->
			  ?msg("Temp ~w is in unused but has degree ~w~n",
			       [R, Deg]),
			  false
		      end end, Unused).

%%%%%%%%%%%%%%%%%%%%
%% Check that no register allocation opportunities were missed due to ?MODULE
%%
just_as_good_as(RegAllocMod, CFG, Liveness, SpillIndex0, SpillLimit, Target,
		Options, SpillMap, Coloring, Unused) ->
  {CheckColoring, _} = RegAllocMod:regalloc(CFG, Liveness, SpillIndex0,
					    SpillLimit, Target, Options),
  Now   = lists:sort([{R,Kind} || {R,{Kind,_}} <- Coloring,
				  not ordsets:is_element(R, Unused)]),
  Check = lists:sort([{R,Kind} || {R,{Kind,_}} <- CheckColoring,
				  not ordsets:is_element(R, Unused)]),
  CheckMap = maps:from_list(Check),
  SaneSpills = all_spills_sane_1(CheckColoring, SpillMap),
  case SaneSpills
    andalso lists:all(fun({R, spill}) -> maps:get(R, CheckMap) =:= spill;
			 ({_,reg}) -> true
		      end, Now)
  of
    true -> true;
    false ->
      {NowRegs, _} = _NowCount = count(Now),
      {CheckRegs, _} = _CheckCount = count(Check),
      {M,F,A} = element(2, element(3, CFG)),
      io:fwrite(standard_error, "Colorings differ (~w, ~w)!~n"
		"MFA: ~w:~w/~w~n"
		"Unused: ~w~n"
		"Now:~w~nCorrect:~w~n",
		[Target, RegAllocMod,
		 M,F,A,
		 Unused,
		 Now -- Check, Check -- Now]),
	SaneSpills andalso NowRegs >= CheckRegs
  end.

count(C) -> {length([[] || {_, reg} <- C]),
	     length([[] || {_, spill} <- C])}.

unused(LivePseudos, SpillMap, CFG, Target) ->
  {TMin, TMax} = Target:var_range(CFG),
  SpillOSet = ordsets:from_list(maps:keys(SpillMap)),
  PhysOSet = ordsets:from_list(Target:all_precoloured()),
  Used = ordsets:union(LivePseudos, ordsets:union(PhysOSet, SpillOSet)),
  ordsets:subtract(lists:seq(TMin, TMax), Used).

%% Check that no temp that we wrote off was actually allocatable.
all_spills_sane_1(_, Empty) when map_size(Empty) =:= 0 -> true;
all_spills_sane_1([], _Nonempty) -> false;
all_spills_sane_1([{T, {reg, _}}|Cs], SpillMap) ->
  not maps:is_key(T, SpillMap) andalso all_spills_sane_1(Cs, SpillMap);
all_spills_sane_1([{T, {spill, _}}|Cs], SpillMap) ->
  all_spills_sane_1(Cs, maps:remove(T, SpillMap)).

-endif. % DO_ASSERT

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Pseudo-target interface
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
analyze(Cfg, _ModRec) -> Cfg.
bb(Cfg=#cfg{bbs=BBs}, Ix, _ModRec) ->
  case BBs of
    #{Ix := #transformed_bb{bb=BB}} -> BB;
    _ -> error(badarg, [Cfg, Ix])
  end.
args(Arity, #?MODULE{target=Target, sub=SubM}) ->
  smap_get(Target:args(Arity), SubM).
labels(#cfg{bbs=BBs}, _ModRec) -> maps:keys(BBs).
livein(#cfg{bbs=BBs}, Lb, _SubMod) ->
  #{Lb := #transformed_bb{livein=Livein}} = BBs,
  Livein.
liveout(#cfg{bbs=BBs}, Lb, _SubMod) ->
  #{Lb := #transformed_bb{liveout=Liveout}} = BBs,
  Liveout.
uses(I, MR) -> element(2, def_use(I, MR)).
defines(I, MR) -> element(1, def_use(I, MR)).
def_use(#instr{defuse=DefUse}, _ModRec) -> DefUse.
is_move(#instr{is_move=IM}, _ModRec) -> IM.
is_fixed(Reg, #?MODULE{target=Target,inv=InvM}) ->
  Target:is_fixed(imap_get(Reg, InvM)). % XXX: Is this hot?
is_global(Reg, #?MODULE{target=Target,max_phys=MaxPhys}) when Reg < MaxPhys ->
  Target:is_global(Reg). % assume id-map
is_precoloured(Reg, #?MODULE{max_phys=MaxPhys}) -> Reg < MaxPhys.
reg_nr(Reg, _ModRec) -> Reg. % After mapping (naturally)
non_alloc(#cfg{cfg=CFG}, #?MODULE{target=Target,sub=SubM}) ->
  smap_get_all_partial(reg_names(Target:non_alloc(CFG), Target), SubM).
number_of_temporaries(#cfg{max_reg=MaxR}, _ModRec) -> MaxR.
allocatable(#?MODULE{target=Target}) -> Target:allocatable(). % assume id-map
physical_name(Reg, _ModRec) -> Reg.
all_precoloured(#?MODULE{target=Target}) -> Target:all_precoloured(). % dito
var_range(#cfg{cfg=_CFG, max_reg=MaxReg}, #?MODULE{target=_Target}) ->
  ?ASSERT(begin {TgtMin, _} = _Target:var_range(_CFG), TgtMin =:= 0 end),
  {0, MaxReg-1}.

postorder(#cfg{cfg=CFG,rpostorder=undefined}, #?MODULE{target=Target}) ->
  Target:postorder(CFG);
postorder(#cfg{rpostorder=Labels}, _ModRec) when is_list(Labels) ->
  lists:reverse(Labels).

reverse_postorder(#cfg{cfg=CFG,rpostorder=undefined}, #?MODULE{target=Target}) ->
  Target:reverse_postorder(CFG);
reverse_postorder(#cfg{rpostorder=Labels}, _ModRec) when is_list(Labels) ->
  Labels.