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

This reverts r374268 (git commit c34385d07c7d59447bf836b740f032235391d121)

I think I reverted this by mistake, so I'm relanding it. While my bisect
found this revision, I think the crashes I'm seeing locally must be
environmental. Maybe the version of clang I'm using miscompiles tot
clang.

llvm-svn: 374269

2 files changed, 12 insertions, 10 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();
diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index a76a840f26e..b05ed75e879 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -352,21 +352,13 @@ Sema::getCurrentMangleNumberContext(const DeclContext *DC,
     //  -- the initializers of inline variables
   case VariableTemplate:
     //  -- the initializers of templated variables
-    return &ExprEvalContexts.back().getMangleNumberingContext(Context);
+    return &Context.getManglingNumberContext(ASTContext::NeedExtraManglingDecl,
+                                             ManglingContextDecl);
   }
 
   llvm_unreachable("unexpected context");
 }
 
-MangleNumberingContext &
-Sema::ExpressionEvaluationContextRecord::getMangleNumberingContext(
-    ASTContext &Ctx) {
-  assert(ManglingContextDecl && "Need to have a context declaration");
-  if (!MangleNumbering)
-    MangleNumbering = Ctx.createMangleNumberingContext();
-  return *MangleNumbering;
-}
-
 CXXMethodDecl *Sema::startLambdaDefinition(
     CXXRecordDecl *Class, SourceRange IntroducerRange,
     TypeSourceInfo *MethodTypeInfo, SourceLocation EndLoc,