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[DFAJumpThreading] Unfold select to the incoming block of phi user #160987

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Merged
merged 4 commits into from
Oct 1, 2025
Merged

[DFAJumpThreading] Unfold select to the incoming block of phi user #160987

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82ec2a7
[DFAJumpThreading] Unfold select to the incoming block of phi user
XChy Sep 27, 2025
3429823
update tests
XChy Sep 27, 2025
5559c09
resolve comment
XChy Oct 1, 2025
f88ce98
Merge branch 'main' into fix-dfa-jump-threading-indirect-select
XChy Oct 1, 2025
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10 changes: 6 additions & 4 deletions llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -190,12 +190,12 @@ void unfold(DomTreeUpdater *DTU, LoopInfo *LI, SelectInstToUnfold SIToUnfold,
std::vector<BasicBlock *> *NewBBs) {
SelectInst *SI = SIToUnfold.getInst();
PHINode *SIUse = SIToUnfold.getUse();
BasicBlock *StartBlock = SI->getParent();
assert(SI->hasOneUse());
// The select may come indirectly, instead of from where it is defined.
BasicBlock *StartBlock = SIUse->getIncomingBlock(*SI->use_begin());
BranchInst *StartBlockTerm =
dyn_cast<BranchInst>(StartBlock->getTerminator());

assert(StartBlockTerm);
assert(SI->hasOneUse());

if (StartBlockTerm->isUnconditional()) {
BasicBlock *EndBlock = StartBlock->getUniqueSuccessor();
Expand Down Expand Up @@ -332,7 +332,7 @@ void unfold(DomTreeUpdater *DTU, LoopInfo *LI, SelectInstToUnfold SIToUnfold,
}

// Preserve loop info
if (Loop *L = LI->getLoopFor(SI->getParent())) {
if (Loop *L = LI->getLoopFor(StartBlock)) {
for (BasicBlock *NewBB : *NewBBs)
L->addBasicBlockToLoop(NewBB, *LI);
}
Expand Down Expand Up @@ -533,6 +533,8 @@ struct MainSwitch {
return false;

// Only fold the select coming from directly where it is defined.
// TODO: We have dealt with the select coming indirectly now. This
// constraint can be relaxed.
PHINode *PHIUser = dyn_cast<PHINode>(SIUse);
if (PHIUser && PHIUser->getIncomingBlock(*SI->use_begin()) != SIBB)
return false;
Expand Down
63 changes: 42 additions & 21 deletions llvm/test/Transforms/DFAJumpThreading/dfa-jump-threading-transform.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -304,32 +304,43 @@ end:
define void @pr106083_invalidBBarg_fold(i1 %cmp1, i1 %cmp2, i1 %not, ptr %d) {
; CHECK-LABEL: @pr106083_invalidBBarg_fold(
; CHECK-NEXT: bb:
; CHECK-NEXT: br i1 [[CMP1:%.*]], label [[BB1:%.*]], label [[SEL_SI_UNFOLD_FALSE:%.*]]
; CHECK: sel.si.unfold.false:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI1:%.*]] = phi i32 [ 1, [[BB:%.*]] ]
; CHECK-NEXT: br label [[BB1]]
; CHECK-NEXT: br label [[BB1:%.*]]
; CHECK: BB1:
; CHECK-NEXT: [[I:%.*]] = phi i16 [ 0, [[BB1_BACKEDGE:%.*]] ], [ 0, [[BB]] ], [ 1, [[BB7:%.*]] ], [ 0, [[SEL_SI_UNFOLD_FALSE]] ], [ 1, [[BB7_JT0:%.*]] ]
; CHECK-NEXT: [[SEL_SI_UNFOLD_PHI:%.*]] = phi i32 [ [[SEL_SI_UNFOLD_PHI]], [[BB1_BACKEDGE]] ], [ [[SEL_SI_UNFOLD_PHI]], [[BB7]] ], [ 0, [[BB]] ], [ [[DOTSI_UNFOLD_PHI1]], [[SEL_SI_UNFOLD_FALSE]] ], [ [[SEL_SI_UNFOLD_PHI]], [[BB7_JT0]] ]
; CHECK-NEXT: [[I:%.*]] = phi i16 [ 0, [[BB1_BACKEDGE:%.*]] ], [ 0, [[BB:%.*]] ], [ 1, [[BB9:%.*]] ], [ 1, [[BB7_JT0:%.*]] ]
; CHECK-NEXT: br i1 [[NOT:%.*]], label [[BB7_JT0]], label [[BB2:%.*]]
; CHECK: BB2:
; CHECK-NEXT: store i16 0, ptr [[D:%.*]], align 2
; CHECK-NEXT: br i1 [[CMP2:%.*]], label [[BB7]], label [[SPEC_SELECT_SI_UNFOLD_FALSE_JT0:%.*]]
; CHECK-NEXT: br i1 [[CMP2:%.*]], label [[BB7:%.*]], label [[SPEC_SELECT_SI_UNFOLD_FALSE_JT0:%.*]]
; CHECK: spec.select.si.unfold.false:
; CHECK-NEXT: br label [[BB7]]
; CHECK-NEXT: br label [[BB9]]
; CHECK: spec.select.si.unfold.false.jt0:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI_JT0:%.*]] = phi i32 [ 0, [[BB2]] ]
; CHECK-NEXT: br label [[BB7_JT0]]
; CHECK: sel.si.unfold.true:
; CHECK-NEXT: br i1 [[CMP1:%.*]], label [[BB9]], label [[SEL_SI_UNFOLD_FALSE_JT1:%.*]]
; CHECK: sel.si.unfold.true.jt0:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI1:%.*]] = phi i32 [ 0, [[BB2]] ]
; CHECK-NEXT: br i1 [[CMP1]], label [[BB7_JT0]], label [[SEL_SI_UNFOLD_FALSE:%.*]]
; CHECK: sel.si.unfold.false:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI2:%.*]] = phi i32 [ 1, [[BB7]] ]
; CHECK-NEXT: br label [[BB9]]
; CHECK: sel.si.unfold.false.jt1:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI2_JT1:%.*]] = phi i32 [ 1, [[SEL_SI_UNFOLD_TRUE:%.*]] ]
; CHECK-NEXT: br label [[BB7_JT1:%.*]]
; CHECK: BB7:
; CHECK-NEXT: [[D_PROMOTED4:%.*]] = phi i16 [ 1, [[BB2]] ], [ 1, [[SPEC_SELECT_SI_UNFOLD_FALSE:%.*]] ]
; CHECK-NEXT: [[_3:%.*]] = phi i32 [ [[SEL_SI_UNFOLD_PHI]], [[BB2]] ], [ poison, [[SPEC_SELECT_SI_UNFOLD_FALSE]] ]
; CHECK-NEXT: [[D_PROMOTED4:%.*]] = phi i16 [ 1, [[SPEC_SELECT_SI_UNFOLD_FALSE:%.*]] ], [ 1, [[SEL_SI_UNFOLD_TRUE]] ], [ 1, [[SEL_SI_UNFOLD_FALSE]] ]
; CHECK-NEXT: [[_3:%.*]] = phi i32 [ poison, [[SPEC_SELECT_SI_UNFOLD_FALSE]] ], [ poison, [[SEL_SI_UNFOLD_TRUE]] ], [ [[DOTSI_UNFOLD_PHI2]], [[SEL_SI_UNFOLD_FALSE]] ]
; CHECK-NEXT: switch i32 [[_3]], label [[BB1_BACKEDGE]] [
; CHECK-NEXT: i32 0, label [[BB1]]
; CHECK-NEXT: i32 1, label [[BB8:%.*]]
; CHECK-NEXT: ]
; CHECK: BB7.jt1:
; CHECK-NEXT: [[D_PROMOTED4_JT1:%.*]] = phi i16 [ 1, [[SEL_SI_UNFOLD_FALSE_JT1]] ]
; CHECK-NEXT: [[_3_JT1:%.*]] = phi i32 [ [[DOTSI_UNFOLD_PHI2_JT1]], [[SEL_SI_UNFOLD_FALSE_JT1]] ]
; CHECK-NEXT: br label [[BB8]]
; CHECK: BB7.jt0:
; CHECK-NEXT: [[D_PROMOTED4_JT0:%.*]] = phi i16 [ 0, [[BB1]] ], [ 1, [[SPEC_SELECT_SI_UNFOLD_FALSE_JT0]] ]
; CHECK-NEXT: [[_3_JT0:%.*]] = phi i32 [ 0, [[BB1]] ], [ [[DOTSI_UNFOLD_PHI_JT0]], [[SPEC_SELECT_SI_UNFOLD_FALSE_JT0]] ]
; CHECK-NEXT: [[D_PROMOTED4_JT0:%.*]] = phi i16 [ 0, [[BB1]] ], [ 1, [[SPEC_SELECT_SI_UNFOLD_FALSE_JT0]] ], [ 1, [[BB7]] ]
; CHECK-NEXT: [[_3_JT0:%.*]] = phi i32 [ 0, [[BB1]] ], [ [[DOTSI_UNFOLD_PHI_JT0]], [[SPEC_SELECT_SI_UNFOLD_FALSE_JT0]] ], [ [[DOTSI_UNFOLD_PHI1]], [[BB7]] ]
; CHECK-NEXT: br label [[BB1]]
; CHECK: BB1.backedge:
; CHECK-NEXT: br label [[BB1]]
Expand Down Expand Up @@ -367,30 +378,40 @@ BB8: ; preds = %BB7
define void @pr106083_select_dead_uses(i1 %cmp1, i1 %not, ptr %p) {
; CHECK-LABEL: @pr106083_select_dead_uses(
; CHECK-NEXT: bb:
; CHECK-NEXT: br i1 [[CMP1:%.*]], label [[DOTLOOPEXIT6:%.*]], label [[SPEC_SELECT_SI_UNFOLD_FALSE:%.*]]
; CHECK: spec.select.si.unfold.false:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI1:%.*]] = phi i32 [ 1, [[BB:%.*]] ]
; CHECK-NEXT: br label [[DOTLOOPEXIT6]]
; CHECK-NEXT: br label [[DOTLOOPEXIT6:%.*]]
; CHECK: .loopexit6:
; CHECK-NEXT: [[SPEC_SELECT_SI_UNFOLD_PHI:%.*]] = phi i32 [ [[SPEC_SELECT_SI_UNFOLD_PHI]], [[SELECT_UNFOLD:%.*]] ], [ 0, [[BB]] ], [ [[DOTSI_UNFOLD_PHI1]], [[SPEC_SELECT_SI_UNFOLD_FALSE]] ]
; CHECK-NEXT: br i1 [[NOT:%.*]], label [[SELECT_UNFOLD_JT0:%.*]], label [[BB1:%.*]]
; CHECK: bb1:
; CHECK-NEXT: [[I:%.*]] = load i32, ptr [[P:%.*]], align 4
; CHECK-NEXT: [[NOT2:%.*]] = icmp eq i32 0, 0
; CHECK-NEXT: br i1 [[NOT2]], label [[SELECT_UNFOLD]], label [[SPEC_SELECT7_SI_UNFOLD_FALSE_JT0:%.*]]
; CHECK-NEXT: br i1 [[NOT2]], label [[SELECT_UNFOLD:%.*]], label [[SPEC_SELECT7_SI_UNFOLD_FALSE_JT0:%.*]]
; CHECK: spec.select7.si.unfold.false:
; CHECK-NEXT: br label [[SELECT_UNFOLD]]
; CHECK-NEXT: br label [[SELECT_UNFOLD1:%.*]]
; CHECK: spec.select7.si.unfold.false.jt0:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI_JT0:%.*]] = phi i32 [ 0, [[BB1]] ]
; CHECK-NEXT: br label [[SELECT_UNFOLD_JT0]]
; CHECK: spec.select.si.unfold.true:
; CHECK-NEXT: br i1 [[CMP1:%.*]], label [[SELECT_UNFOLD1]], label [[SPEC_SELECT_SI_UNFOLD_FALSE_JT1:%.*]]
; CHECK: spec.select.si.unfold.true.jt0:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI1:%.*]] = phi i32 [ 0, [[BB1]] ]
; CHECK-NEXT: br i1 [[CMP1]], label [[SELECT_UNFOLD_JT0]], label [[SPEC_SELECT_SI_UNFOLD_FALSE:%.*]]
; CHECK: spec.select.si.unfold.false:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI2:%.*]] = phi i32 [ 1, [[SELECT_UNFOLD]] ]
; CHECK-NEXT: br label [[SELECT_UNFOLD1]]
; CHECK: spec.select.si.unfold.false.jt1:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI2_JT1:%.*]] = phi i32 [ 1, [[SPEC_SELECT_SI_UNFOLD_TRUE:%.*]] ]
; CHECK-NEXT: br label [[SELECT_UNFOLD_JT1:%.*]]
; CHECK: select.unfold:
; CHECK-NEXT: [[_2:%.*]] = phi i32 [ [[SPEC_SELECT_SI_UNFOLD_PHI]], [[BB1]] ], [ poison, [[SPEC_SELECT7_SI_UNFOLD_FALSE:%.*]] ]
; CHECK-NEXT: [[_2:%.*]] = phi i32 [ poison, [[SPEC_SELECT7_SI_UNFOLD_FALSE:%.*]] ], [ poison, [[SPEC_SELECT_SI_UNFOLD_TRUE]] ], [ [[DOTSI_UNFOLD_PHI2]], [[SPEC_SELECT_SI_UNFOLD_FALSE]] ]
; CHECK-NEXT: switch i32 [[_2]], label [[BB2:%.*]] [
; CHECK-NEXT: i32 0, label [[DOTPREHEADER_PREHEADER:%.*]]
; CHECK-NEXT: i32 1, label [[DOTLOOPEXIT6]]
; CHECK-NEXT: ]
; CHECK: select.unfold.jt1:
; CHECK-NEXT: [[_2_JT1:%.*]] = phi i32 [ [[DOTSI_UNFOLD_PHI2_JT1]], [[SPEC_SELECT_SI_UNFOLD_FALSE_JT1]] ]
; CHECK-NEXT: br label [[DOTLOOPEXIT6]]
; CHECK: select.unfold.jt0:
; CHECK-NEXT: [[_2_JT0:%.*]] = phi i32 [ 0, [[DOTLOOPEXIT6]] ], [ [[DOTSI_UNFOLD_PHI_JT0]], [[SPEC_SELECT7_SI_UNFOLD_FALSE_JT0]] ]
; CHECK-NEXT: [[_2_JT0:%.*]] = phi i32 [ 0, [[DOTLOOPEXIT6]] ], [ [[DOTSI_UNFOLD_PHI_JT0]], [[SPEC_SELECT7_SI_UNFOLD_FALSE_JT0]] ], [ [[DOTSI_UNFOLD_PHI1]], [[SELECT_UNFOLD]] ]
; CHECK-NEXT: br label [[DOTPREHEADER_PREHEADER]]
; CHECK: .preheader.preheader:
; CHECK-NEXT: ret void
Expand Down
84 changes: 84 additions & 0 deletions llvm/test/Transforms/DFAJumpThreading/dfa-unfold-select.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -463,3 +463,87 @@ unreachable:
sw.bb: ; preds = %if.end
br label %while.cond
}

define i16 @pr160250() {
; CHECK-LABEL: @pr160250(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_COND48:%.*]]
; CHECK: for.cond48:
; CHECK-NEXT: br i1 false, label [[CLEANUP87_JT0:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.else:
; CHECK-NEXT: br i1 false, label [[DOT6_SI_UNFOLD_TRUE:%.*]], label [[DOT5_SI_UNFOLD_TRUE:%.*]]
; CHECK: .5.si.unfold.true:
; CHECK-NEXT: br i1 false, label [[SPEC_SELECT1_SI_UNFOLD_TRUE1:%.*]], label [[DOT5_SI_UNFOLD_FALSE_JT0:%.*]]
; CHECK: .5.si.unfold.true.jt0:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI1:%.*]] = phi i32 [ 0, [[IF_ELSE]] ]
; CHECK-NEXT: br i1 false, label [[SPEC_SELECT1_SI_UNFOLD_TRUE:%.*]], label [[DOT5_SI_UNFOLD_FALSE:%.*]]
; CHECK: .5.si.unfold.false:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI2:%.*]] = phi i32 [ 0, [[DOT5_SI_UNFOLD_TRUE]] ]
; CHECK-NEXT: br label [[SPEC_SELECT1_SI_UNFOLD_TRUE1]]
; CHECK: .5.si.unfold.false.jt0:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI2_JT0:%.*]] = phi i32 [ 0, [[DOT5_SI_UNFOLD_TRUE1:%.*]] ]
; CHECK-NEXT: br label [[SPEC_SELECT1_SI_UNFOLD_TRUE]]
; CHECK: spec.select1.si.unfold.true:
; CHECK-NEXT: [[DOT5_SI_UNFOLD_PHI:%.*]] = phi i32 [ poison, [[DOT5_SI_UNFOLD_TRUE1]] ], [ [[DOTSI_UNFOLD_PHI2]], [[DOT5_SI_UNFOLD_FALSE]] ]
; CHECK-NEXT: br i1 false, label [[SPEC_SELECT_SI_UNFOLD_FALSE1:%.*]], label [[SPEC_SELECT1_SI_UNFOLD_FALSE_JT1:%.*]]
; CHECK: spec.select1.si.unfold.true.jt0:
; CHECK-NEXT: [[DOT5_SI_UNFOLD_PHI_JT0:%.*]] = phi i32 [ [[DOTSI_UNFOLD_PHI1]], [[DOT5_SI_UNFOLD_TRUE]] ], [ [[DOTSI_UNFOLD_PHI2_JT0]], [[DOT5_SI_UNFOLD_FALSE_JT0]] ]
; CHECK-NEXT: br i1 false, label [[SPEC_SELECT_SI_UNFOLD_FALSE:%.*]], label [[SPEC_SELECT1_SI_UNFOLD_FALSE_JT0:%.*]]
; CHECK: spec.select1.si.unfold.false:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI:%.*]] = phi i32 [ 0, [[SPEC_SELECT1_SI_UNFOLD_TRUE]] ]
; CHECK-NEXT: br label [[SPEC_SELECT_SI_UNFOLD_FALSE1]]
; CHECK: spec.select1.si.unfold.false.jt0:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI_JT0:%.*]] = phi i32 [ 0, [[SPEC_SELECT1_SI_UNFOLD_TRUE1]] ]
; CHECK-NEXT: br label [[SPEC_SELECT_SI_UNFOLD_FALSE]]
; CHECK: spec.select.si.unfold.false:
; CHECK-NEXT: [[SPEC_SELECT1_SI_UNFOLD_PHI:%.*]] = phi i32 [ [[DOT5_SI_UNFOLD_PHI]], [[SPEC_SELECT1_SI_UNFOLD_TRUE1]] ], [ [[DOTSI_UNFOLD_PHI]], [[SPEC_SELECT1_SI_UNFOLD_FALSE_JT0]] ]
; CHECK-NEXT: br label [[CLEANUP87:%.*]]
; CHECK: spec.select.si.unfold.false.jt0:
; CHECK-NEXT: [[SPEC_SELECT1_SI_UNFOLD_PHI_JT0:%.*]] = phi i32 [ [[DOT5_SI_UNFOLD_PHI_JT0]], [[SPEC_SELECT1_SI_UNFOLD_TRUE]] ], [ [[DOTSI_UNFOLD_PHI_JT0]], [[SPEC_SELECT1_SI_UNFOLD_FALSE_JT1]] ]
; CHECK-NEXT: br label [[CLEANUP87_JT0]]
; CHECK: .6.si.unfold.true:
; CHECK-NEXT: br i1 false, label [[CLEANUP87]], label [[DOT6_SI_UNFOLD_FALSE_JT0:%.*]]
; CHECK: .6.si.unfold.true.jt0:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI3:%.*]] = phi i32 [ 0, [[IF_ELSE]] ]
; CHECK-NEXT: br i1 false, label [[CLEANUP87_JT0]], label [[DOT6_SI_UNFOLD_FALSE:%.*]]
; CHECK: .6.si.unfold.false:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI4:%.*]] = phi i32 [ 0, [[DOT6_SI_UNFOLD_TRUE]] ]
; CHECK-NEXT: br label [[CLEANUP87]]
; CHECK: .6.si.unfold.false.jt0:
; CHECK-NEXT: [[DOTSI_UNFOLD_PHI4_JT0:%.*]] = phi i32 [ 0, [[DOT6_SI_UNFOLD_TRUE1:%.*]] ]
; CHECK-NEXT: br label [[CLEANUP87_JT0]]
; CHECK: cleanup87:
; CHECK-NEXT: [[CLEANUP_DEST_SLOT_3:%.*]] = phi i32 [ [[SPEC_SELECT1_SI_UNFOLD_PHI]], [[SPEC_SELECT_SI_UNFOLD_FALSE1]] ], [ poison, [[DOT6_SI_UNFOLD_TRUE1]] ], [ [[DOTSI_UNFOLD_PHI4]], [[DOT6_SI_UNFOLD_FALSE]] ]
; CHECK-NEXT: switch i32 [[CLEANUP_DEST_SLOT_3]], label [[FOR_COND48_BACKEDGE:%.*]] [
; CHECK-NEXT: i32 0, label [[FOR_COND48_BACKEDGE]]
; CHECK-NEXT: i32 1, label [[FOR_COND48_BACKEDGE]]
; CHECK-NEXT: ]
; CHECK: cleanup87.jt0:
; CHECK-NEXT: [[CLEANUP_DEST_SLOT_3_JT0:%.*]] = phi i32 [ 0, [[FOR_COND48]] ], [ [[SPEC_SELECT1_SI_UNFOLD_PHI_JT0]], [[SPEC_SELECT_SI_UNFOLD_FALSE]] ], [ [[DOTSI_UNFOLD_PHI3]], [[DOT6_SI_UNFOLD_TRUE]] ], [ [[DOTSI_UNFOLD_PHI4_JT0]], [[DOT6_SI_UNFOLD_FALSE_JT0]] ]
; CHECK-NEXT: br label [[FOR_COND48_BACKEDGE]]
; CHECK: for.cond48.backedge:
; CHECK-NEXT: br label [[FOR_COND48]]
;
entry:
%.5 = select i1 false, i32 0, i32 0
%.6 = select i1 false, i32 0, i32 0
br label %for.cond48

for.cond48: ; preds = %for.cond48.backedge, %entry
br i1 false, label %cleanup87, label %if.else

if.else: ; preds = %for.cond48
%spec.select1 = select i1 false, i32 %.5, i32 0
%spec.select = select i1 false, i32 %.6, i32 %spec.select1
br label %cleanup87

cleanup87: ; preds = %if.else, %for.cond48
%cleanup.dest.slot.3 = phi i32 [ 0, %for.cond48 ], [ %spec.select, %if.else ]
switch i32 %cleanup.dest.slot.3, label %for.cond48.backedge [
i32 0, label %for.cond48.backedge
i32 1, label %for.cond48.backedge
]

for.cond48.backedge: ; preds = %cleanup87, %cleanup87, %cleanup87
br label %for.cond48
}