Index: lib/Transforms/Coroutines/Coroutines.cpp =================================================================== --- lib/Transforms/Coroutines/Coroutines.cpp +++ lib/Transforms/Coroutines/Coroutines.cpp @@ -218,6 +218,8 @@ size_t FinalSuspendIndex = 0; clear(*this); SmallVector CoroFrames; + SmallVector UnusedCoroSaves; + for (Instruction &I : instructions(F)) { if (auto II = dyn_cast(&I)) { switch (II->getIntrinsicID()) { @@ -229,6 +231,12 @@ case Intrinsic::coro_frame: CoroFrames.push_back(cast(II)); break; + case Intrinsic::coro_save: + // After optimizations, coro_suspends using this coro_save might have + // been removed, remember orphaned coro_saves to remove them later. + if (II->use_empty()) + UnusedCoroSaves.push_back(cast(II)); + break; case Intrinsic::coro_suspend: CoroSuspends.push_back(cast(II)); if (CoroSuspends.back()->isFinal()) { @@ -311,4 +319,8 @@ if (HasFinalSuspend && FinalSuspendIndex != CoroSuspends.size() - 1) std::swap(CoroSuspends[FinalSuspendIndex], CoroSuspends.back()); + + // Remove orphaned coro.saves. + for (CoroSaveInst *CoroSave : UnusedCoroSaves) + CoroSave->eraseFromParent(); } Index: test/Transforms/Coroutines/coro-split-02.ll =================================================================== --- test/Transforms/Coroutines/coro-split-02.ll +++ test/Transforms/Coroutines/coro-split-02.ll @@ -1,5 +1,6 @@ ; Tests that coro-split can handle the case when a code after coro.suspend uses ; a value produces between coro.save and coro.suspend (%Result.i19) +; and checks whether stray coro.saves are properly removed ; RUN: opt < %s -coro-split -S | FileCheck %s %"struct.std::coroutine_handle" = type { i8* } @@ -24,9 +25,10 @@ i8 1, label %exit ] await.ready: + %StrayCoroSave = call token @llvm.coro.save(i8* null) %val = load i32, i32* %Result.i19 call void @print(i32 %val) - br label %exit + br label %exit exit: call i1 @llvm.coro.end(i8* null, i1 false) ret void @@ -35,6 +37,7 @@ ; CHECK-LABEL: @a.resume( ; CHECK: getelementptr inbounds %a.Frame ; CHECK-NEXT: getelementptr inbounds %"struct.lean_future::Awaiter" +; CHECK-NOT: call token @llvm.coro.save(i8* null) ; CHECK-NEXT: %val = load i32, i32* %Result ; CHECK-NEXT: call void @print(i32 %val) ; CHECK-NEXT: ret void