Nested "generate" statements

Hi,

I'm trying to write something like:

gen1: FOR J IN 5 DOWNTO 0 GENERATE
gen2: FOR I IN 7 DOWNTO 0 GENERATE
gen3: IF ( I = J + 2 ) GENERATE
...

If I use the above, not a single component is instantiated. If I replace the last line by
gen3: IF ( I = 7 ) GENERATE

then it does work. In fact, as soon as I add a line comparing both of the two variables of the outer generate statements, things go wrong. I did find examples on the net where it is done this way.

Does anyone know why everything gets synthetised away?

Thanks,
W

wjsimons