I’ve searched and searched, but I cannot find anything on the web that details the level of GLSL support across various hardware and drivers.
In particular, I’m interested in the bugs that are known to exist.
For example, I recently tried to implement a simple nested loop on my Mac powerbook and after a certain number of nested iterations it just stopped working.
I know of a single vendor-supplied document from nvidia which details some limitations of their G30 and G40 hardware (ie. noise() always returns 0s and some other restrictions).
Vendors are usually not very good at pointing out the limits of their hardware. Especially, if those are not obvious.
I don’t know of any such documents. As a rule of thumb, anything, that is not absolutely trivial, will make problems on some hardware with some drivers.