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[SimplifyCFG] Remove all incoming values from OtherDest if OtherDest is unreachable #162677

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Merged
merged 1 commit into from
Oct 9, 2025
+28 −1
Merged

[SimplifyCFG] Remove all incoming values from OtherDest if OtherDest is unreachable #162677

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6 changes: 5 additions & 1 deletion llvm/lib/Transforms/Utils/SimplifyCFG.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5959,7 +5959,11 @@ bool SimplifyCFGOpt::turnSwitchRangeIntoICmp(SwitchInst *SI,
unsigned PreviousEdges = OtherCases->size();
if (OtherDest == SI->getDefaultDest())
++PreviousEdges;
for (unsigned I = 0, E = PreviousEdges - 1; I != E; ++I)
unsigned E = PreviousEdges - 1;
// Remove all incoming values from OtherDest if OtherDest is unreachable.
if (NewBI->isUnconditional())
++E;
for (unsigned I = 0; I != E; ++I)
cast<PHINode>(BBI)->removeIncomingValue(SI->getParent());
}

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23 changes: 23 additions & 0 deletions llvm/test/Transforms/SimplifyCFG/switch-range-to-icmp.ll
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Expand Up @@ -401,4 +401,27 @@ b:
ret i32 %1
}

define i32 @else_will_be_unreachable(i1 %arg) {
; CHECK-LABEL: @else_will_be_unreachable(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[I:%.*]] = select i1 [[ARG:%.*]], i32 0, i32 1
; CHECK-NEXT: ret i32 [[I]]
;
entry:
switch i1 %arg, label %else [
i1 false, label %if
i1 true, label %if
]

if:
br i1 %arg, label %else, label %bb

bb:
br label %else

else:
%i = phi i32 [ 0, %entry ], [ 0, %if ], [ 1, %bb ]
ret i32 %i
}

declare void @bar(ptr nonnull dereferenceable(4))