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[SimplifyCFG] Fix crash when there is unreachable large index #88616

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Merged
merged 1 commit into from
Apr 15, 2024
Merged

[SimplifyCFG] Fix crash when there is unreachable large index #88616

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4 changes: 3 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 @@ -6783,9 +6783,11 @@ static bool SwitchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,
return SwitchLookupTable::WouldFitInRegister(
DL, UpperBound, KV.second /* ResultType */);
})) {
// There may be some case index larger than the UpperBound (unreachable
// case), so make sure the table size does not get smaller.
TableSize = std::max(UpperBound, TableSize);
// The default branch is unreachable after we enlarge the lookup table.
// Adjust DefaultIsReachable to reuse code path.
TableSize = UpperBound;
DefaultIsReachable = false;
}
}
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25 changes: 25 additions & 0 deletions llvm/test/Transforms/SimplifyCFG/switch_mask.ll
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Expand Up @@ -214,3 +214,28 @@ lor.end: ; preds = %default, %for.end,
%retval.0.i.i = phi i32 [ 1, %default ], [ 0, %for.end ], [ 0, %for.end ], [ 0, %for.end ]
ret void
}

define i1 @pr88607() {
; CHECK-LABEL: @pr88607(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[COND:%.*]] = select i1 false, i32 4, i32 1
; CHECK-NEXT: [[SPEC_SELECT:%.*]] = select i1 false, i32 2, i32 [[COND]]
; CHECK-NEXT: ret i1 false
;
entry:
%cond = select i1 false, i32 4, i32 1
%spec.select = select i1 false, i32 2, i32 %cond
switch i32 %spec.select, label %lor.rhs [
i32 0, label %exit
i32 5, label %exit ; unreachable large case index
i32 1, label %exit
]

lor.rhs: ; preds = %entry
br label %exit

exit: ; preds = %lor.rhs, %entry, %entry, %entry, %entry
%res.ph = phi i1 [ false, %entry ], [ false, %lor.rhs ], [ false, %entry ], [ false, %entry ]
ret i1 %res.ph
}