ExitSSA: don't exclude PHINodes with non-phi Users

Before this commit, the code never put in the same group two PHINodes if
one of them had a non-phi User. This condition was wrong and was
unnecessarily preventing valig PHINodes to be put in the same group.
This caused the generation of a lot more local variables than necessary.

lib/Canonicalize/ExitSSAPass.cpp

@@ -122,12 +122,6 @@ static std::vector<SetVector<PHINode *>> getPHIEquivalenceClasses(Function &F) {
         if (PHISameVariableClasses.isEquivalent(&PHI, PHIUser))
           continue;
 
-        // If the PHI has a user that is not another PHI, it cannot be put in
-        // the same equivalence class as the PHIUser, so we bail out.
-        if (llvm::any_of(PHI.users(),
-                         [](const User *U) { return not isa<PHINode>(U); }))
-          continue;
-
         PHINode *PHILeader = PHISameVariableClasses.getLeaderValue(&PHI);
         PHINode *UserLeader = PHISameVariableClasses.getLeaderValue(PHIUser);