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UsmanNadeemUsmanNadeem
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[DFAJumpThreading] Handle select unfolding when user phi is not a direct successor
Previously the code assumed that the select instruction is defined in a block that is a direct predecessor of the block where the PHINode uses it. So, we were hitting an assertion when we tried to access the def block as an incoming block for the user phi node. This patch handles that case by using the correct end block and creating a new phi node that aggregates both the values of the select in that end block, and then using that new unfolded phi to overwrite the original user phi node. Fixes #106083 Change-Id: Ie471994cca232318f74a6e6438efa21e561c2dc0
1 parent 0cab475 commit 9f0d042

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2 files changed

+263
-17
lines changed

2 files changed

+263
-17
lines changed

‎llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp‎

Lines changed: 29 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -194,14 +194,14 @@ void unfold(DomTreeUpdater *DTU, LoopInfo *LI, SelectInstToUnfold SIToUnfold,
194194
SelectInst *SI = SIToUnfold.getInst();
195195
PHINode *SIUse = SIToUnfold.getUse();
196196
BasicBlock *StartBlock = SI->getParent();
197-
BasicBlock *EndBlock = SIUse->getParent();
198197
BranchInst *StartBlockTerm =
199198
dyn_cast<BranchInst>(StartBlock->getTerminator());
200199

201200
assert(StartBlockTerm);
202201
assert(SI->hasOneUse());
203202

204203
if (StartBlockTerm->isUnconditional()) {
204+
BasicBlock *EndBlock = StartBlock->getUniqueSuccessor();
205205
// Arbitrarily choose the 'false' side for a new input value to the PHI.
206206
BasicBlock *NewBlock = BasicBlock::Create(
207207
SI->getContext(), Twine(SI->getName(), ".si.unfold.false"),
@@ -223,32 +223,44 @@ void unfold(DomTreeUpdater *DTU, LoopInfo *LI, SelectInstToUnfold SIToUnfold,
223223
NewBlock->getFirstInsertionPt());
224224
NewPhi->addIncoming(SIOp2, StartBlock);
225225

226-
if (auto *OpSi = dyn_cast<SelectInst>(SIOp1))
227-
NewSIsToUnfold->push_back(SelectInstToUnfold(OpSi, SIUse));
228-
if (auto *OpSi = dyn_cast<SelectInst>(SIOp2))
229-
NewSIsToUnfold->push_back(SelectInstToUnfold(OpSi, NewPhi));
230-
231-
// Update the phi node of SI.
232-
for (unsigned Idx = 0; Idx < SIUse->getNumIncomingValues(); ++Idx) {
233-
if (SIUse->getIncomingBlock(Idx) == StartBlock)
234-
SIUse->setIncomingValue(Idx, SIOp1);
226+
// Update any other PHI nodes in EndBlock.
227+
for (PHINode &Phi : EndBlock->phis()) {
228+
if (SIUse == &Phi)
229+
continue;
230+
Phi.addIncoming(Phi.getIncomingValueForBlock(StartBlock), NewBlock);
235231
}
236-
SIUse->addIncoming(NewPhi, NewBlock);
237232

238-
// Update any other PHI nodes in EndBlock.
239-
for (auto II = EndBlock->begin(); PHINode *Phi = dyn_cast<PHINode>(II);
240-
++II) {
241-
if (Phi != SIUse)
242-
Phi->addIncoming(Phi->getIncomingValueForBlock(StartBlock), NewBlock);
233+
// Update the phi node of SI, which is its only use.
234+
if (EndBlock == SIUse->getParent()) {
235+
SIUse->addIncoming(NewPhi, NewBlock);
236+
SIUse->replaceUsesOfWith(SI, SIOp1);
237+
} else {
238+
PHINode *EndPhi = PHINode::Create(SIUse->getType(), pred_size(EndBlock),
239+
Twine(SI->getName(), ".si.unfold.phi"),
240+
EndBlock->getFirstInsertionPt());
241+
for (BasicBlock *Pred : predecessors(EndBlock)) {
242+
if (Pred != StartBlock && Pred != NewBlock)
243+
EndPhi->addIncoming(EndPhi, Pred);
244+
}
245+
246+
EndPhi->addIncoming(SIOp1, StartBlock);
247+
EndPhi->addIncoming(NewPhi, NewBlock);
248+
SIUse->replaceUsesOfWith(SI, EndPhi);
249+
SIUse = EndPhi;
243250
}
244251

245-
StartBlockTerm->eraseFromParent();
252+
if (auto *OpSi = dyn_cast<SelectInst>(SIOp1))
253+
NewSIsToUnfold->push_back(SelectInstToUnfold(OpSi, SIUse));
254+
if (auto *OpSi = dyn_cast<SelectInst>(SIOp2))
255+
NewSIsToUnfold->push_back(SelectInstToUnfold(OpSi, NewPhi));
246256

247257
// Insert the real conditional branch based on the original condition.
258+
StartBlockTerm->eraseFromParent();
248259
BranchInst::Create(EndBlock, NewBlock, SI->getCondition(), StartBlock);
249260
DTU->applyUpdates({{DominatorTree::Insert, StartBlock, EndBlock},
250261
{DominatorTree::Insert, StartBlock, NewBlock}});
251262
} else {
263+
BasicBlock *EndBlock = SIUse->getParent();
252264
BasicBlock *NewBlockT = BasicBlock::Create(
253265
SI->getContext(), Twine(SI->getName(), ".si.unfold.true"),
254266
EndBlock->getParent(), EndBlock);

‎llvm/test/Transforms/DFAJumpThreading/dfa-jump-threading-transform.ll‎

Lines changed: 234 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -300,3 +300,237 @@ define void @self-reference() {
300300
end:
301301
ret void
302302
}
303+
304+
@a = external dso_local global ptr, align 8
305+
@b = external dso_local global i32, align 4
306+
@c = external dso_local global i64, align 8
307+
@d = external dso_local global i16, align 2
308+
@e = external dso_local global i64, align 8
309+
@f = external dso_local global i32, align 4
310+
@g = external dso_local global i64, align 8
311+
@h = external dso_local global i32, align 4
312+
@i = external dso_local global ptr, align 8
313+
314+
define void @pr106083_invalidBBarg_fold() {
315+
; CHECK-LABEL: @pr106083_invalidBBarg_fold(
316+
; CHECK-NEXT: [[TMP1:%.*]] = load i32, ptr @h, align 4
317+
; CHECK-NEXT: [[DOTNOT2:%.*]] = icmp eq i32 [[TMP1]], 0
318+
; CHECK-NEXT: [[D_PROMOTED3:%.*]] = load i16, ptr @d, align 1
319+
; CHECK-NEXT: br i1 [[DOTNOT2]], label [[BB0:%.*]], label [[DOT_SI_UNFOLD_FALSE:%.*]]
320+
; CHECK: BB0.loopexit:
321+
; CHECK-NEXT: [[D_PROMOTED41:%.*]] = phi i16 [ [[D_PROMOTED4_JT2:%.*]], [[BB7_JT2:%.*]] ], [ [[D_PROMOTED4:%.*]], [[BB7:%.*]] ]
322+
; CHECK-NEXT: br label [[BB0]]
323+
; CHECK: ..si.unfold.false:
324+
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI:%.*]] = phi i32 [ 6, [[TMP0:%.*]] ]
325+
; CHECK-NEXT: br label [[BB0]]
326+
; CHECK: BB0:
327+
; CHECK-NEXT: [[D_PROMOTED6:%.*]] = phi i16 [ [[D_PROMOTED3]], [[TMP0]] ], [ [[D_PROMOTED41]], [[BB0_LOOPEXIT:%.*]] ], [ [[D_PROMOTED3]], [[DOT_SI_UNFOLD_FALSE]] ]
328+
; CHECK-NEXT: [[DOT_SI_UNFOLD_PHI:%.*]] = phi i32 [ [[DOT_SI_UNFOLD_PHI]], [[BB0_LOOPEXIT]] ], [ 0, [[TMP0]] ], [ [[DOTSI_UNFOLD_PHI]], [[DOT_SI_UNFOLD_FALSE]] ]
329+
; CHECK-NEXT: br label [[BB1_JT2:%.*]]
330+
; CHECK: BB1:
331+
; CHECK-NEXT: [[D_PROMOTED5:%.*]] = phi i16 [ [[D_PROMOTED4]], [[BB1_BACKEDGE:%.*]] ]
332+
; CHECK-NEXT: [[TMP2:%.*]] = phi i16 [ [[TMP10:%.*]], [[BB1_BACKEDGE]] ]
333+
; CHECK-NEXT: [[DOT1:%.*]] = phi i32 [ [[DOT3:%.*]], [[BB1_BACKEDGE]] ]
334+
; CHECK-NEXT: [[TMP3:%.*]] = load volatile i32, ptr @f, align 4
335+
; CHECK-NEXT: [[DOTNOT:%.*]] = icmp eq i32 [[TMP3]], 0
336+
; CHECK-NEXT: br i1 [[DOTNOT]], label [[BB7]], label [[BB2:%.*]]
337+
; CHECK: BB1.jt2:
338+
; CHECK-NEXT: [[D_PROMOTED5_JT2:%.*]] = phi i16 [ [[D_PROMOTED6]], [[BB0]] ]
339+
; CHECK-NEXT: [[TMP4:%.*]] = phi i16 [ [[D_PROMOTED6]], [[BB0]] ]
340+
; CHECK-NEXT: [[DOT1_JT2:%.*]] = phi i32 [ 2, [[BB0]] ]
341+
; CHECK-NEXT: [[TMP5:%.*]] = load volatile i32, ptr @f, align 4
342+
; CHECK-NEXT: [[DOTNOT_JT2:%.*]] = icmp eq i32 [[TMP5]], 0
343+
; CHECK-NEXT: br i1 [[DOTNOT_JT2]], label [[BB7_JT2]], label [[BB2_JT2:%.*]]
344+
; CHECK: BB2:
345+
; CHECK-NEXT: [[TMP6:%.*]] = add i16 [[TMP2]], 1
346+
; CHECK-NEXT: store i16 [[TMP6]], ptr @d, align 2
347+
; CHECK-NEXT: [[TMP7:%.*]] = load volatile i64, ptr @g, align 8
348+
; CHECK-NEXT: [[DOTNOT1:%.*]] = icmp eq i64 [[TMP7]], 0
349+
; CHECK-NEXT: br i1 [[DOTNOT1]], label [[BB7]], label [[SPEC_SELECT_SI_UNFOLD_FALSE:%.*]]
350+
; CHECK: BB2.jt2:
351+
; CHECK-NEXT: [[TMP8:%.*]] = add i16 [[TMP4]], 1
352+
; CHECK-NEXT: store i16 [[TMP8]], ptr @d, align 2
353+
; CHECK-NEXT: [[TMP9:%.*]] = load volatile i64, ptr @g, align 8
354+
; CHECK-NEXT: [[DOTNOT1_JT2:%.*]] = icmp eq i64 [[TMP9]], 0
355+
; CHECK-NEXT: br i1 [[DOTNOT1_JT2]], label [[BB7]], label [[SPEC_SELECT_SI_UNFOLD_FALSE_JT2:%.*]]
356+
; CHECK: spec.select.si.unfold.false:
357+
; CHECK-NEXT: [[DOT1_SI_UNFOLD_PHI:%.*]] = phi i32 [ [[DOT1]], [[BB2]] ]
358+
; CHECK-NEXT: br label [[BB7]]
359+
; CHECK: spec.select.si.unfold.false.jt2:
360+
; CHECK-NEXT: [[DOT1_SI_UNFOLD_PHI_JT2:%.*]] = phi i32 [ [[DOT1_JT2]], [[BB2_JT2]] ]
361+
; CHECK-NEXT: br label [[BB7_JT2]]
362+
; CHECK: BB7:
363+
; CHECK-NEXT: [[D_PROMOTED4]] = phi i16 [ [[D_PROMOTED5]], [[BB1:%.*]] ], [ [[TMP6]], [[BB2]] ], [ [[TMP6]], [[SPEC_SELECT_SI_UNFOLD_FALSE]] ], [ [[TMP8]], [[BB2_JT2]] ]
364+
; CHECK-NEXT: [[TMP10]] = phi i16 [ [[TMP2]], [[BB1]] ], [ [[TMP6]], [[BB2]] ], [ [[TMP6]], [[SPEC_SELECT_SI_UNFOLD_FALSE]] ], [ [[TMP8]], [[BB2_JT2]] ]
365+
; CHECK-NEXT: [[DOT3]] = phi i32 [ [[DOT1]], [[BB1]] ], [ [[DOT_SI_UNFOLD_PHI]], [[BB2]] ], [ [[DOT1_SI_UNFOLD_PHI]], [[SPEC_SELECT_SI_UNFOLD_FALSE]] ], [ [[DOT_SI_UNFOLD_PHI]], [[BB2_JT2]] ]
366+
; CHECK-NEXT: switch i32 [[DOT3]], label [[BB9:%.*]] [
367+
; CHECK-NEXT: i32 0, label [[BB1_BACKEDGE]]
368+
; CHECK-NEXT: i32 7, label [[BB1_BACKEDGE]]
369+
; CHECK-NEXT: i32 6, label [[BB8:%.*]]
370+
; CHECK-NEXT: i32 2, label [[BB0_LOOPEXIT]]
371+
; CHECK-NEXT: ]
372+
; CHECK: BB7.jt2:
373+
; CHECK-NEXT: [[D_PROMOTED4_JT2]] = phi i16 [ [[D_PROMOTED5_JT2]], [[BB1_JT2]] ], [ [[TMP8]], [[SPEC_SELECT_SI_UNFOLD_FALSE_JT2]] ]
374+
; CHECK-NEXT: [[TMP11:%.*]] = phi i16 [ [[TMP4]], [[BB1_JT2]] ], [ [[TMP8]], [[SPEC_SELECT_SI_UNFOLD_FALSE_JT2]] ]
375+
; CHECK-NEXT: [[DOT3_JT2:%.*]] = phi i32 [ [[DOT1_JT2]], [[BB1_JT2]] ], [ [[DOT1_SI_UNFOLD_PHI_JT2]], [[SPEC_SELECT_SI_UNFOLD_FALSE_JT2]] ]
376+
; CHECK-NEXT: br label [[BB0_LOOPEXIT]]
377+
; CHECK: BB1.backedge:
378+
; CHECK-NEXT: br label [[BB1]]
379+
; CHECK: BB8:
380+
; CHECK-NEXT: ret void
381+
; CHECK: BB9:
382+
; CHECK-NEXT: unreachable
383+
;
384+
%1 = load i32, ptr @h, align 4
385+
%.not2 = icmp eq i32 %1, 0
386+
%. = select i1 %.not2, i32 0, i32 6
387+
%d.promoted3 = load i16, ptr @d, align 1
388+
br label %BB0
389+
390+
BB0.loopexit: ; preds = %BB7
391+
br label %BB0
392+
393+
BB0: ; preds = %BB0.loopexit, %0
394+
%d.promoted6 = phi i16 [ %d.promoted3, %0 ], [ %d.promoted4, %BB0.loopexit ]
395+
br label %BB1
396+
397+
BB1: ; preds = %BB1.backedge, %BB0
398+
%d.promoted5 = phi i16 [ %d.promoted6, %BB0 ], [ %d.promoted4, %BB1.backedge ]
399+
%2 = phi i16 [ %d.promoted6, %BB0 ], [ %6, %BB1.backedge ]
400+
%.1 = phi i32 [ 2, %BB0 ], [ %.3, %BB1.backedge ]
401+
%3 = load volatile i32, ptr @f, align 4
402+
%.not = icmp eq i32 %3, 0
403+
br i1 %.not, label %BB7, label %BB2
404+
405+
BB2: ; preds = %BB1
406+
%4 = add i16 %2, 1
407+
store i16 %4, ptr @d, align 2
408+
%5 = load volatile i64, ptr @g, align 8
409+
%.not1 = icmp eq i64 %5, 0
410+
%spec.select = select i1 %.not1, i32 %., i32 %.1
411+
br label %BB7
412+
413+
BB7: ; preds = %BB2, %BB1
414+
%d.promoted4 = phi i16 [ %d.promoted5, %BB1 ], [ %4, %BB2 ]
415+
%6 = phi i16 [ %2, %BB1 ], [ %4, %BB2 ]
416+
%.3 = phi i32 [ %.1, %BB1 ], [ %spec.select, %BB2 ]
417+
switch i32 %.3, label %BB9 [
418+
i32 0, label %BB1.backedge
419+
i32 7, label %BB1.backedge
420+
i32 6, label %BB8
421+
i32 2, label %BB0.loopexit
422+
]
423+
424+
BB1.backedge: ; preds = %BB7, %BB7
425+
br label %BB1
426+
427+
BB8: ; preds = %BB7
428+
ret void
429+
430+
BB9: ; preds = %BB7
431+
unreachable
432+
}
433+
434+
435+
define void @pr106083_select_dead_uses() {
436+
; CHECK-LABEL: @pr106083_select_dead_uses(
437+
; CHECK-NEXT: [[TMP1:%.*]] = load ptr, ptr @a, align 8
438+
; CHECK-NEXT: [[TMP2:%.*]] = load ptr, ptr @i, align 8
439+
; CHECK-NEXT: [[TMP3:%.*]] = load i64, ptr @c, align 8
440+
; CHECK-NEXT: [[DOTNOT3:%.*]] = icmp eq i64 [[TMP3]], 0
441+
; CHECK-NEXT: br i1 [[DOTNOT3]], label [[DOTLOOPEXIT6:%.*]], label [[SPEC_SELECT_SI_UNFOLD_FALSE:%.*]]
442+
; CHECK: .loopexit6.loopexit:
443+
; CHECK-NEXT: br label [[DOTLOOPEXIT6]]
444+
; CHECK: spec.select.si.unfold.false:
445+
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI:%.*]] = phi i32 [ 2, [[TMP0:%.*]] ]
446+
; CHECK-NEXT: br label [[DOTLOOPEXIT6]]
447+
; CHECK: .loopexit6:
448+
; CHECK-NEXT: [[SPEC_SELECT_SI_UNFOLD_PHI:%.*]] = phi i32 [ [[SPEC_SELECT_SI_UNFOLD_PHI]], [[DOTLOOPEXIT6_LOOPEXIT:%.*]] ], [ 0, [[TMP0]] ], [ [[DOTSI_UNFOLD_PHI]], [[SPEC_SELECT_SI_UNFOLD_FALSE]] ]
449+
; CHECK-NEXT: br label [[TMP6:%.*]]
450+
; CHECK: 4:
451+
; CHECK-NEXT: [[DOT1:%.*]] = phi i32 [ [[DOT21:%.*]], [[DOTBACKEDGE:%.*]] ]
452+
; CHECK-NEXT: [[TMP5:%.*]] = load i32, ptr [[TMP1]], align 4
453+
; CHECK-NEXT: [[DOTNOT:%.*]] = icmp eq i32 [[TMP5]], 0
454+
; CHECK-NEXT: br i1 [[DOTNOT]], label [[SELECT_UNFOLD_JT0:%.*]], label [[TMP8:%.*]]
455+
; CHECK: 6:
456+
; CHECK-NEXT: [[DOT1_JT2:%.*]] = phi i32 [ 2, [[DOTLOOPEXIT6]] ]
457+
; CHECK-NEXT: [[TMP7:%.*]] = load i32, ptr [[TMP1]], align 4
458+
; CHECK-NEXT: [[DOTNOT_JT2:%.*]] = icmp eq i32 [[TMP7]], 0
459+
; CHECK-NEXT: br i1 [[DOTNOT_JT2]], label [[SELECT_UNFOLD_JT0]], label [[TMP10:%.*]]
460+
; CHECK: 8:
461+
; CHECK-NEXT: [[TMP9:%.*]] = load i32, ptr [[TMP2]], align 4
462+
; CHECK-NEXT: [[DOTNOT2:%.*]] = icmp eq i32 [[TMP9]], 0
463+
; CHECK-NEXT: br i1 [[DOTNOT2]], label [[SELECT_UNFOLD:%.*]], label [[SPEC_SELECT7_SI_UNFOLD_FALSE:%.*]]
464+
; CHECK: 10:
465+
; CHECK-NEXT: [[TMP11:%.*]] = load i32, ptr [[TMP2]], align 4
466+
; CHECK-NEXT: [[DOTNOT2_JT2:%.*]] = icmp eq i32 [[TMP11]], 0
467+
; CHECK-NEXT: br i1 [[DOTNOT2_JT2]], label [[SELECT_UNFOLD]], label [[SPEC_SELECT7_SI_UNFOLD_FALSE_JT2:%.*]]
468+
; CHECK: spec.select7.si.unfold.false:
469+
; CHECK-NEXT: [[DOT1_SI_UNFOLD_PHI:%.*]] = phi i32 [ [[DOT1]], [[TMP8]] ]
470+
; CHECK-NEXT: br label [[SELECT_UNFOLD]]
471+
; CHECK: spec.select7.si.unfold.false.jt2:
472+
; CHECK-NEXT: [[DOT1_SI_UNFOLD_PHI_JT2:%.*]] = phi i32 [ [[DOT1_JT2]], [[TMP10]] ]
473+
; CHECK-NEXT: br label [[SELECT_UNFOLD_JT2:%.*]]
474+
; CHECK: select.unfold:
475+
; CHECK-NEXT: [[DOT2:%.*]] = phi i32 [ [[SPEC_SELECT_SI_UNFOLD_PHI]], [[TMP8]] ], [ [[DOT1_SI_UNFOLD_PHI]], [[SPEC_SELECT7_SI_UNFOLD_FALSE]] ], [ [[SPEC_SELECT_SI_UNFOLD_PHI]], [[TMP10]] ]
476+
; CHECK-NEXT: switch i32 [[DOT2]], label [[TMP12:%.*]] [
477+
; CHECK-NEXT: i32 0, label [[DOTPREHEADER_PREHEADER:%.*]]
478+
; CHECK-NEXT: i32 2, label [[DOTLOOPEXIT6_LOOPEXIT]]
479+
; CHECK-NEXT: ]
480+
; CHECK: select.unfold.jt2:
481+
; CHECK-NEXT: [[DOT2_JT2:%.*]] = phi i32 [ [[DOT1_SI_UNFOLD_PHI_JT2]], [[SPEC_SELECT7_SI_UNFOLD_FALSE_JT2]] ]
482+
; CHECK-NEXT: br label [[DOTLOOPEXIT6_LOOPEXIT]]
483+
; CHECK: select.unfold.jt0:
484+
; CHECK-NEXT: [[DOT2_JT0:%.*]] = phi i32 [ 0, [[TMP4:%.*]] ], [ 0, [[TMP6]] ]
485+
; CHECK-NEXT: br label [[DOTPREHEADER_PREHEADER]]
486+
; CHECK: .preheader.preheader:
487+
; CHECK-NEXT: [[DOT21]] = phi i32 [ [[DOT2_JT0]], [[SELECT_UNFOLD_JT0]] ], [ [[DOT2]], [[SELECT_UNFOLD]] ]
488+
; CHECK-NEXT: store i32 0, ptr @b, align 4
489+
; CHECK-NEXT: br label [[DOTBACKEDGE]]
490+
; CHECK: .backedge:
491+
; CHECK-NEXT: br label [[TMP4]]
492+
; CHECK: 12:
493+
; CHECK-NEXT: unreachable
494+
;
495+
%1 = load ptr, ptr @a, align 8
496+
%2 = load ptr, ptr @i, align 8
497+
%3 = load i64, ptr @c, align 8
498+
%.not3 = icmp eq i64 %3, 0
499+
%spec.select = select i1 %.not3, i32 0, i32 2
500+
br label %.loopexit6
501+
502+
.loopexit6.loopexit: ; preds = %select.unfold
503+
br label %.loopexit6
504+
505+
.loopexit6: ; preds = %.loopexit6.loopexit, %0
506+
br label %4
507+
508+
4: ; preds = %.backedge, %.loopexit6
509+
%.1 = phi i32 [ 2, %.loopexit6 ], [ %.2, %.backedge ]
510+
%5 = load i32, ptr %1, align 4
511+
%.not = icmp eq i32 %5, 0
512+
br i1 %.not, label %select.unfold, label %6
513+
514+
6: ; preds = %4
515+
%7 = load i32, ptr %2, align 4
516+
%.not2 = icmp eq i32 %7, 0
517+
%spec.select7 = select i1 %.not2, i32 %spec.select, i32 %.1
518+
br label %select.unfold
519+
520+
select.unfold: ; preds = %6, %4
521+
%.2 = phi i32 [ 0, %4 ], [ %spec.select7, %6 ]
522+
switch i32 %.2, label %8 [
523+
i32 0, label %.preheader.preheader
524+
i32 2, label %.loopexit6.loopexit
525+
]
526+
527+
.preheader.preheader: ; preds = %select.unfold
528+
store i32 0, ptr @b, align 4
529+
br label %.backedge
530+
531+
.backedge: ; preds = %.preheader.preheader
532+
br label %4
533+
534+
8: ; preds = %select.unfold
535+
unreachable
536+
}

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