WIP [clang] Recursively instantiate constexpr template functions.

clang/lib/Sema/SemaExpr.cpp

@@ -18485,7 +18485,7 @@ void Sema::MarkFunctionReferenced(SourceLocation Loc, FunctionDecl *Func,
             // Do not defer instantiations of constexpr functions, to avoid the
             // expression evaluator needing to call back into Sema if it sees a
             // call to such a function.
-            InstantiateFunctionDefinition(PointOfInstantiation, Func);
+            InstantiateFunctionDefinition(PointOfInstantiation, Func, true);
           else {
             Func->setInstantiationIsPending(true);
             PendingInstantiations.push_back(

clang/test/SemaTemplate/instantiate-pure-virtual-function.cpp

@@ -43,18 +43,9 @@ namespace non_pure_virtual_function {
     constexpr void foo(const T &) { bar(1); }
 
     virtual constexpr void bar(unsigned int); // expected-warning {{inline function 'non_pure_virtual_function::B<int>::bar' is not defined}}
-    // expected-note@-1 {{forward declaration of template entity is here}}
-    // expected-note@-2 {{forward declaration of template entity is here}}
-    // expected-note@-3 {{forward declaration of template entity is here}}
   };
 
-  template <typename T> class D : public B<T> { // expected-warning {{instantiation of function 'non_pure_virtual_function::B<int>::bar' required here, but no definition is available}}
-// expected-warning@-1 {{instantiation of function 'non_pure_virtual_function::B<int>::bar' required here, but no definition is available}}
-// expected-warning@-2 {{instantiation of function 'non_pure_virtual_function::B<int>::bar' required here, but no definition is available}}
-// expected-note@-3 {{add an explicit instantiation declaration to suppress this warning if 'non_pure_virtual_function::B<int>::bar' is explicitly instantiated in another translation unit}}
-// expected-note@-4 {{add an explicit instantiation declaration to suppress this warning if 'non_pure_virtual_function::B<int>::bar' is explicitly instantiated in another translation unit}}
-// expected-note@-5 {{add an explicit instantiation declaration to suppress this warning if 'non_pure_virtual_function::B<int>::bar' is explicitly instantiated in another translation unit}}
-// expected-note@-6 {{used here}}
+  template <typename T> class D : public B<T> { // expected-note@ {{used here}}
 
   public:
     constexpr void bar(unsigned int) override { }

clang/unittests/Support/TimeProfilerTest.cpp

@@ -332,8 +332,8 @@ Frontend (test.cc)
 | | InstantiateFunction (fooA<int>, a.h:7)
 | | | InstantiateFunction (fooB<int>, b.h:8)
 | | | | DeferInstantiation (fooC<int>)
+| | | | InstantiateFunction (fooC<int>, b.h:3)
 | | | DeferInstantiation (fooMTA<int>)
-| | | InstantiateFunction (fooC<int>, b.h:3)
 | | | InstantiateFunction (fooMTA<int>, a.h:4)
 )",
             buildTraceGraph(Json));