Index: clang/lib/AST/Interp/ByteCodeExprGen.cpp
===================================================================
--- clang/lib/AST/Interp/ByteCodeExprGen.cpp
+++ clang/lib/AST/Interp/ByteCodeExprGen.cpp
@@ -1484,7 +1484,7 @@
   assert(FD);
   const Function *Func = P.getFunction(FD);
   bool IsBeingCompiled = Func && !Func->isFullyCompiled();
-  bool WasNotDefined = Func && !Func->hasBody();
+  bool WasNotDefined = Func && !Func->isConstexpr() && !Func->hasBody();
 
   if (IsBeingCompiled)
     return Func;
Index: clang/lib/AST/Interp/Function.h
===================================================================
--- clang/lib/AST/Interp/Function.h
+++ clang/lib/AST/Interp/Function.h
@@ -157,7 +157,7 @@
     SrcMap = std::move(NewSrcMap);
     Scopes = std::move(NewScopes);
     IsValid = true;
-    HasBody = true;
+    HasBody = NewCode.size() > 0;
   }
 
   void setIsFullyCompiled(bool FC) { IsFullyCompiled = FC; }
Index: clang/test/AST/Interp/functions.cpp
===================================================================
--- clang/test/AST/Interp/functions.cpp
+++ clang/test/AST/Interp/functions.cpp
@@ -154,3 +154,12 @@
 }
 
 }
+
+struct F {
+  constexpr bool ok() const {
+    return okRecurse();
+  }
+  constexpr bool okRecurse() const {
+    return true;
+  }
+};