[ThinLTO] Handle optional args in assembly format for ConstVCalls

Summary:
The AsmWriter was only writing the Args for a ConstVCall if it was
non-empty, however, the LLParser was always expecting it. To aid
in making it optional, surround the ConstVCall VFuncId and Args in
parentheses when writing, then make the Args optional when reading.

Reviewers: pcc

Subscribers: mehdi_amini, inglorion, eraman, steven_wu, dexonsmith, llvm-commits

Differential Revision: https://reviews.llvm.org/D49960

llvm-svn: 339637

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index 99a25a723b4..e19c7c20a5d 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -2955,11 +2955,13 @@ void AssemblyWriter::printConstVCalls(
   FieldSeparator FS;
   for (auto &ConstVCall : VCallList) {
     Out << FS;
+    Out << "(";
     printVFuncId(ConstVCall.VFunc);
     if (!ConstVCall.Args.empty()) {
       Out << ", ";
       printArgs(ConstVCall.Args);
     }
+    Out << ")";
   }
   Out << ")";
 }