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[WebAssembly] Avoid crash in LateEHPrepare with empty cleanup pads #200322

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Merged
dschuff merged 1 commit into from
May 29, 2026
Merged

[WebAssembly] Avoid crash in LateEHPrepare with empty cleanup pads #200322

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3 changes: 2 additions & 1 deletion llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -311,7 +311,8 @@ bool WebAssemblyLateEHPrepare::addCatchRefsAndThrowRefs(MachineFunction &MF) {
// caught exception is rethrown. And convert RETHROWs to THROW_REFs.
for (auto &[EHPad, Rethrows] : EHPadToRethrows) {
auto *Catch = WebAssembly::findCatch(EHPad);
auto *InsertPos = Catch->getIterator()->getNextNode();
assert(Catch && "CATCH not found in EHPad");
auto InsertPos = std::next(Catch->getIterator());
auto ExnReg = MRI.createVirtualRegister(&WebAssembly::EXNREFRegClass);
if (Catch->getOpcode() == WebAssembly::CATCH) {
MachineInstrBuilder MIB = BuildMI(*EHPad, InsertPos, Catch->getDebugLoc(),
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27 changes: 27 additions & 0 deletions llvm/test/CodeGen/WebAssembly/exception.ll
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Expand Up @@ -672,5 +672,32 @@ attributes #0 = { nounwind }
attributes #1 = { noreturn }
attributes #2 = { noreturn nounwind }

; CHECK-LABEL: empty_cleanup_pad:
; CHECK: try_table (catch_all_ref 0)
; CHECK: throw_ref
define void @empty_cleanup_pad(i32 %arg) personality ptr @__gxx_wasm_personality_v0 {
entry:
br label %loop

loop:
invoke void @foo()
to label %loop unwind label %cleanup

cleanup:
%exn = cleanuppad within none []
br label %dispatch

dispatch: ; preds = %cleanup, %dispatch
%cond = icmp eq i32 %arg, 0
br i1 %cond, label %ret, label %dispatch

ret: ; preds = %dispatch
cleanupret from %exn unwind label %cleanup2

cleanup2: ; preds = %ret
%exn2 = cleanuppad within none []
ret void
}

;; The exception tag should not be defined locally
; CHECK-NOT: __cpp_exception: