Clarify comments

Author: fpasserby

clang/lib/CodeGen/CGCoroutine.cpp

@@ -452,16 +452,14 @@ CodeGenFunction::generateAwaitSuspendWrapper(Twine const &CoroName,
 
   StartFunction(GlobalDecl(), ReturnTy, Fn, FI, args);
 
+  // FIXME: add TBAA metadata to the loads
   llvm::Value *AwaiterPtr = Builder.CreateLoad(GetAddrOfLocalVar(&AwaiterDecl));
   auto AwaiterLValue =
       MakeNaturalAlignAddrLValue(AwaiterPtr, AwaiterDecl.getType());
 
   CurAwaitSuspendWrapper.FramePtr =
       Builder.CreateLoad(GetAddrOfLocalVar(&FrameDecl));
 
-  // FIXME: mark as aliasing with frame?
-  // FIXME: TBAA?
-  // FIXME: emit in a better way (maybe egenerate AST in SemaCoroutine)?
   auto AwaiterBinder = CodeGenFunction::OpaqueValueMappingData::bind(
       *this, S.getOpaqueValue(), AwaiterLValue);
 

llvm/lib/Transforms/Coroutines/CoroInstr.h

@@ -79,6 +79,9 @@ class LLVM_LIBRARY_VISIBILITY CoroAllocInst : public IntrinsicInst {
 };
 
 /// This represents the llvm.coro.await.suspend instruction.
+// FIXME: add callback metadata
+// FIXME: make a proper IntrinisicInst. Currently this is not possible,
+// because llvm.coro.await.suspend can be invoked.
 class LLVM_LIBRARY_VISIBILITY CoroAwaitSuspendInst : public CallBase {
   enum { AwaiterArg, FrameArg, WrapperArg };
 

llvm/lib/Transforms/Coroutines/CoroSplit.cpp

@@ -179,6 +179,12 @@ static void lowerAwaitSuspend(IRBuilder<> &Builder, CoroAwaitSuspendInst *CB) {
   Builder.SetInsertPoint(CB);
 
   CallBase *NewCall = nullptr;
+  // await_suspend has only 2 parameters, awaiter and handle.
+  // Copy parameter attributes from the intrinsic call, but remove the last,
+  // because the last parameter now becomes the function that is being called.
+  AttributeList NewAttributes =
+      CB->getAttributes().removeParamAttributes(CB->getContext(), 2);
+
   if (auto Invoke = dyn_cast<InvokeInst>(CB)) {
     auto WrapperInvoke =
         Builder.CreateInvoke(Wrapper, Invoke->getNormalDest(),
@@ -187,16 +193,12 @@ static void lowerAwaitSuspend(IRBuilder<> &Builder, CoroAwaitSuspendInst *CB) {
     WrapperInvoke->setCallingConv(Invoke->getCallingConv());
     std::copy(Invoke->bundle_op_info_begin(), Invoke->bundle_op_info_end(),
               WrapperInvoke->bundle_op_info_begin());
-    AttributeList NewAttributes =
-        Invoke->getAttributes().removeParamAttributes(Invoke->getContext(), 2);
     WrapperInvoke->setAttributes(NewAttributes);
     WrapperInvoke->setDebugLoc(Invoke->getDebugLoc());
     NewCall = WrapperInvoke;
   } else if (auto Call = dyn_cast<CallInst>(CB)) {
     auto WrapperCall = Builder.CreateCall(Wrapper, {Awaiter, FramePtr});
 
-    AttributeList NewAttributes =
-        Call->getAttributes().removeParamAttributes(Call->getContext(), 2);
     WrapperCall->setAttributes(NewAttributes);
     WrapperCall->setDebugLoc(Call->getDebugLoc());
     NewCall = WrapperCall;