Revert r254592 (virtual dtor in SCEVPredicate).

Clang has better diagnostics in this case.  It is not necessary therefore
to change the destructor to avoid what is effectively an invalid warning
in gcc.  Instead, better handle the warning flags given to the compiler.

llvm-svn: 255905

cmake/modules/HandleLLVMOptions.cmake

@@ -391,7 +391,10 @@ elseif( LLVM_COMPILER_IS_GCC_COMPATIBLE )
     # Check if -Wnon-virtual-dtor warns even though the class is marked final.
     # If it does, don't add it. So it won't be added on clang 3.4 and older.
     # This also catches cases when -Wnon-virtual-dtor isn't supported by
-    # the compiler at all.
+    # the compiler at all.  This flag is not activated for gcc since it will
+    # incorrectly identify a protected non-virtual base when there is a friend
+    # declaration.
+    if (NOT CMAKE_COMPILER_IS_GNUCXX)
       set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
       set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++11 -Werror=non-virtual-dtor")
       CHECK_CXX_SOURCE_COMPILES("class base {public: virtual void anchor();protected: ~base();};
@@ -401,6 +404,10 @@ elseif( LLVM_COMPILER_IS_GCC_COMPATIBLE )
       set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
       append_if(CXX_WONT_WARN_ON_FINAL_NONVIRTUALDTOR
                 "-Wnon-virtual-dtor" CMAKE_CXX_FLAGS)
+    endif()
+
+    # Enable -Wdelete-non-virtual-dtor if available.
+    add_flag_if_supported("-Wdelete-non-virtual-dtor" DELETE_NON_VIRTUAL_DTOR_FLAG)
 
     # Check if -Wcomment is OK with an // comment ending with '\' if the next
     # line is also a // comment.

include/llvm/Analysis/ScalarEvolution.h

@@ -183,7 +183,7 @@ namespace llvm {
 
   protected:
     SCEVPredicateKind Kind;
-    virtual ~SCEVPredicate();
+    ~SCEVPredicate() = default;
     SCEVPredicate(const SCEVPredicate&) = default;
     SCEVPredicate &operator=(const SCEVPredicate&) = default;
 

lib/Analysis/ScalarEvolution.cpp

@@ -9628,8 +9628,6 @@ SCEVPredicate::SCEVPredicate(const FoldingSetNodeIDRef ID,
                              SCEVPredicateKind Kind)
     : FastID(ID), Kind(Kind) {}
 
-SCEVPredicate::~SCEVPredicate() {}
-
 SCEVEqualPredicate::SCEVEqualPredicate(const FoldingSetNodeIDRef ID,
                                        const SCEVUnknown *LHS,
                                        const SCEVConstant *RHS)