[coroutines] PR33271: Remove stray coro.save intrinsics during CoroSplit

Summary:
Optimization passes may remove llvm.coro.suspend intrinsic while leaving matching llvm.coro.save intrinsic orphaned.
Make sure we clean up orphaned coro.saves.  The bug manifested with a crash similar to this:

```
    llvm_unreachable("Unknown type!");
    llvm::MVT::getVT (Ty=0x489518, HandleUnknown=false)
    llvm::EVT::getEVT
    llvm::TargetLoweringBase::getValueType
    llvm::ComputeValueVTs
    llvm::SelectionDAGBuilder::visitTargetIntrinsic
```

Reviewers: GorNishanov

Subscribers: EricWF, llvm-commits

Differential Revision: https://reviews.llvm.org/D33817

llvm-svn: 304518

1 files changed, 12 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Coroutines/Coroutines.cpp b/llvm/lib/Transforms/Coroutines/Coroutines.cpp
index ea48043f938..44e1f9b404e 100644
--- a/llvm/lib/Transforms/Coroutines/Coroutines.cpp
+++ b/llvm/lib/Transforms/Coroutines/Coroutines.cpp
@@ -218,6 +218,8 @@ void coro::Shape::buildFrom(Function &F) {
   size_t FinalSuspendIndex = 0;
   clear(*this);
   SmallVector<CoroFrameInst *, 8> CoroFrames;
+  SmallVector<CoroSaveInst *, 2> UnusedCoroSaves;
+
   for (Instruction &I : instructions(F)) {
     if (auto II = dyn_cast<IntrinsicInst>(&I)) {
       switch (II->getIntrinsicID()) {
@@ -229,6 +231,12 @@ void coro::Shape::buildFrom(Function &F) {
       case Intrinsic::coro_frame:
         CoroFrames.push_back(cast<CoroFrameInst>(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<CoroSaveInst>(II));
+        break;
       case Intrinsic::coro_suspend:
         CoroSuspends.push_back(cast<CoroSuspendInst>(II));
         if (CoroSuspends.back()->isFinal()) {
@@ -311,4 +319,8 @@ void coro::Shape::buildFrom(Function &F) {
   if (HasFinalSuspend &&
       FinalSuspendIndex != CoroSuspends.size() - 1)
     std::swap(CoroSuspends[FinalSuspendIndex], CoroSuspends.back());
+
+  // Remove orphaned coro.saves.
+  for (CoroSaveInst *CoroSave : UnusedCoroSaves)
+    CoroSave->eraseFromParent();
 }