[mangle] Fix mangling where an extra mangle context is required.

Summary:
- [Itanium C++ ABI][1], for certain contexts like default parameter and
  etc., mangling numbering will be local to the particular argument in
  which it appears.
- However, for these cases, the mangle numbering context is allocated per
  expression evaluation stack entry. That causes, for example, two
  lambdas defined/used understand the same default parameter are
  numbered as the same value and, in turn, one of them is not generated
  at all.
- In this patch, an extra mangle numbering context map is maintained in
  the AST context to map taht extra declaration context to its numbering
  context. So that, 2 different lambdas defined/used in the same default
  parameter are numbered differently.

[1]: https://itanium-cxx-abi.github.io/cxx-abi/abi.html

Reviewers: rsmith, eli.friedman

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D68715

llvm-svn: 374200

1 files changed, 10 insertions, 0 deletions

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index a41b64ffcc8..8dd57f2bd28 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -10261,6 +10261,16 @@ ASTContext::getManglingNumberContext(const DeclContext *DC) {
   return *MCtx;
 }
 
+MangleNumberingContext &
+ASTContext::getManglingNumberContext(NeedExtraManglingDecl_t, const Decl *D) {
+  assert(LangOpts.CPlusPlus); // We don't need mangling numbers for plain C.
+  std::unique_ptr<MangleNumberingContext> &MCtx =
+      ExtraMangleNumberingContexts[D];
+  if (!MCtx)
+    MCtx = createMangleNumberingContext();
+  return *MCtx;
+}
+
 std::unique_ptr<MangleNumberingContext>
 ASTContext::createMangleNumberingContext() const {
   return ABI->createMangleNumberingContext();