I've got a 947-line MXML file that seems to require over a
minute of CPU time to "Open in Compare Editor".
Specifically, I'm using Flex Builder 3 as an Eclipse 3.3.2
plug-in with Subclipse 1.2.4. If I synchronize with repository that
runs in a few seconds. If I then try to view the diff for the file
in question (main.mxml), the CPU goes to 100% and eclipse.exe piles
up about 1:19 of CPU time.
I tried a few experiments with chopping out parts of the
file. Here are times to Open in Compare Editor single-line diffs
with only the first N lines of the file in question: