[coroutines] Evaluate the operand of void `co_return` expressions.

Summary:
Previously Clang incorrectly ignored the expression of a void `co_return`. This patch addresses that bug.

I'm not quite sure if I got the code-gen right, but this patch is at least a start.

Reviewers: rsmith, GorNishanov

Reviewed By: rsmith, GorNishanov

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D36070

llvm-svn: 309545

1 files changed, 7 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGCoroutine.cpp b/clang/lib/CodeGen/CGCoroutine.cpp
index a65faa602b3..d23697a5309 100644
--- a/clang/lib/CodeGen/CGCoroutine.cpp
+++ b/clang/lib/CodeGen/CGCoroutine.cpp
@@ -234,6 +234,13 @@ RValue CodeGenFunction::EmitCoyieldExpr(const CoyieldExpr &E,
 
 void CodeGenFunction::EmitCoreturnStmt(CoreturnStmt const &S) {
   ++CurCoro.Data->CoreturnCount;
+  const Expr *RV = S.getOperand();
+  if (RV && RV->getType()->isVoidType()) {
+    // Make sure to evaluate the expression of a co_return with a void
+    // expression for side effects.
+    RunCleanupsScope cleanupScope(*this);
+    EmitIgnoredExpr(RV);
+  }
   EmitStmt(S.getPromiseCall());
   EmitBranchThroughCleanup(CurCoro.Data->FinalJD);
 }