[Attributor] Add missing operators for ChangeStatus

[kuter]

Summary

This patch adds the missing &= and |= operatos for ChangeStatus.

[jdoerfert]

can we use them right away in some places?

[kuter]

This feature was added by another patch.

llvm/include/llvm/Transforms/IPO/Attributor.h

 ///
 ///{
 enum class ChangeStatus {
   CHANGED,
   UNCHANGED,
 };
 
 ChangeStatus operator|(ChangeStatus l, ChangeStatus r);
+void operator|=(ChangeStatus &l, ChangeStatus r);
 ChangeStatus operator&(ChangeStatus l, ChangeStatus r);
+void operator&=(ChangeStatus &l, ChangeStatus r);
 
 enum class DepClassTy {
   REQUIRED,
   OPTIONAL,
 };
 ///}
 
 /// The data structure for the nodes of a dependency graph

llvm/lib/Transforms/IPO/Attributor.cpp

static cl::opt<bool> PrintDependencies("attributor-print-dep", cl::Hidden,
                                        cl::init(false));
 
 /// Logic operators for the change status enum class.
 ///
 ///{
 ChangeStatus llvm::operator|(ChangeStatus l, ChangeStatus r) {
   return l == ChangeStatus::CHANGED ? l : r;
 }
+
+void llvm::operator|=(ChangeStatus &l, ChangeStatus r) { l = l | r; }
+
 ChangeStatus llvm::operator&(ChangeStatus l, ChangeStatus r) {
   return l == ChangeStatus::UNCHANGED ? l : r;
 }
+
+void llvm::operator&=(ChangeStatus &l, ChangeStatus r) { l = l & r; }
+
 ///}
 
 /// Return true if \p New is equal or worse than \p Old.
 static bool isEqualOrWorse(const Attribute &New, const Attribute &Old) {
   if (!Old.isIntAttribute())
     return true;
 
   return Old.getValueAsInt() >= New.getValueAsInt();