I have opened a large HDL or constraints file in Code Editor. Most edits can be performed as expected. However, if I attempt one of the actions listed below, the editor performance is very slow (taking tens of seconds) and it appears to have hung.
This issue is fixed in Vivado IDE 2013.1.
In prior versions, the suggested work-around is to use an external (third-party) text editor when extensive use of the outlined operations is required.
Also, using smaller text files where possible is helpful. For example, constraints files can be broken up into timing and physical constraints files, and further broken up by regions of the device or hierarchy of the design in order to obtain smaller file sizes. Note that all required constraint files should be added to the active constraint set in order to be used.