[Coroutines] Avoid assert splitting hidden coros

Summary:
When attempting to split a coroutine with 'hidden' visibility (for
example, a C++ coroutine that is inlined when compiled with the option
'-fvisibility-inlines-hidden'), LLVM would hit an assertion in
include/llvm/IR/GlobalValue.h:240: "local linkage requires default
visibility". The issue is that the visibility is copied from the source
of the function split in the `CloneFunctionInto` function, but the linkage
is not. To fix, create the new function first with external linkage,
then copy the linkage from the original function *after* `CloneFunctionInto`
is called.

Since `GlobalValue::setLinkage` in turn calls `maybeSetDsoLocal`, the
explicit call to `setDSOLocal` can be removed in CoroSplit.cpp.

Test Plan: check-llvm

Reviewers: GorNishanov, lewissbaker, EricWF, majnemer, rnk

Reviewed By: rnk

Subscribers: llvm-commits, eric_niebler

Differential Revision: https://reviews.llvm.org/D44185

llvm-svn: 329033

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Coroutines/CoroSplit.cpp b/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
index f122fe6f079..6ab56f25e8b 100644
--- a/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
+++ b/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
@@ -250,7 +250,7 @@ static Function *createClone(Function &F, Twine Suffix, coro::Shape &Shape,
   auto *FnTy = cast<FunctionType>(FnPtrTy->getElementType());
 
   Function *NewF =
-      Function::Create(FnTy, GlobalValue::LinkageTypes::InternalLinkage,
+      Function::Create(FnTy, GlobalValue::LinkageTypes::ExternalLinkage,
                        F.getName() + Suffix, M);
   NewF->addParamAttr(0, Attribute::NonNull);
   NewF->addParamAttr(0, Attribute::NoAlias);
@@ -265,7 +265,7 @@ static Function *createClone(Function &F, Twine Suffix, coro::Shape &Shape,
   SmallVector<ReturnInst *, 4> Returns;
 
   CloneFunctionInto(NewF, &F, VMap, /*ModuleLevelChanges=*/true, Returns);
-  NewF->setDSOLocal(true);
+  NewF->setLinkage(GlobalValue::LinkageTypes::InternalLinkage);
 
   // Remove old returns.
   for (ReturnInst *Return : Returns)