Huh? QCreator, Netbeans and Eclipse C/C++ IDEs are fully integrated with GCC, including both debugging and compilation.
What Xcode can do is integrate llvm with autocompletion. For example, if you do a switch statement on an enum-value, it autocompletes the possible enum constants after you type "case". After the first entry, it automatically removes the constants you already used from the list of possibilities.
Xcode also does perfect autocompletion (method names, parameter types, etc.) of types derived from C++ templates, which simply isn't possible without compiling the file. This even works as you change the same file those templates are declared in.
Other things include the analyzer, which tells you about issues that arise on certain input conditions. When you click on an issue, Xcode visually displays the flow through the program to arrive at the undesired end result using arrows.