Modular Codegen: Add/use a bit in serialized function definitions to track whether they are the subject of modular codegen

Some decls are created not where they are written, but in other module
files/users (implicit special members and function template implicit
specializations). To correctly identify them, use a bit next to the definition
to track the modular codegen property.

Discussed whether the module file bit could be omitted in favor of
reconstituting from the modular codegen decls list - best guess today is that
the efficiency improvement of not having to deserialize the whole list whenever
any function is queried by a module user is worth it for the small size
increase of this redundant (list + bit-on-def) representation.

Reviewers: rsmith

Differential Revision: https://reviews.llvm.org/D29901

llvm-svn: 299982

2 files changed, 34 insertions, 0 deletions

diff --git a/clang/test/Modules/Inputs/codegen/foo.h b/clang/test/Modules/Inputs/codegen/foo.h
index 3fcab718573..e77e8d1824e 100644
--- a/clang/test/Modules/Inputs/codegen/foo.h
+++ b/clang/test/Modules/Inputs/codegen/foo.h
@@ -2,3 +2,29 @@ inline void f1(const char* fmt, ...) {
   __builtin_va_list args;
   __builtin_va_start(args, fmt);
 }
+
+struct non_trivial_dtor {
+  ~non_trivial_dtor();
+};
+
+struct implicit_dtor {
+  non_trivial_dtor d;
+};
+
+struct uninst_implicit_dtor {
+  non_trivial_dtor d;
+};
+
+inline void use_implicit_dtor() {
+  implicit_dtor d;
+}
+
+template <typename T>
+void inst() {
+}
+
+inline void inst_decl() {
+  // cause inst<int>'s declaration to be instantiated, without a definition.
+  (void)sizeof(&inst<int>);
+  inst<float>();
+}
diff --git a/clang/test/Modules/Inputs/codegen/use.cpp b/clang/test/Modules/Inputs/codegen/use.cpp
new file mode 100644
index 00000000000..cd1a4a642d0
--- /dev/null
+++ b/clang/test/Modules/Inputs/codegen/use.cpp
@@ -0,0 +1,8 @@
+#include "foo.h"
+void non_modular_use_of_implicit_dtor() {
+  implicit_dtor d1;
+  uninst_implicit_dtor d2;
+}
+void use_of_instantiated_declaration_without_definition() {
+  inst<int>();
+}