[LAD] Denormals / subnormals (again)

Hi all, I have been looking into ye olde denormal problem a little, lately. Particularly with respect to Ardour and plugins. I've assembled what I believe to be a coherent statement of what is going on, but I'd very much appreciate any corrections and clarifications that anyone can offer. Here's how it seems to me: If you compile your code (e.g. a plugin) without -msse and -mfpmath=sse on the GCC command line you get *no* protection from denormals from the CPU. If they occur in your code, they will be very much slower than normal floating point numbers (~49 times slower on my Core 2 Duo, ~7 times slower on a Core i3). As far as I can see, it does not matter that Ardour has been built with those flags: if a plugin has not, you have no protection. If you compile your code with -msse and -mfpmath=sse, you have Ardour's protection from denormals. If the user's CPU supports it, you get there is no significant slowdown with denormals using this mode. However CPU support is "some later processors with SSE2", according to Intel. The problem, I guess, is that we cannot really distribute plugins with SSE instructions, otherwise we do not support people with older CPUs. In this case, I think the plugin code must avoid denormals, otherwise there will be a significant performance hit if they arise. I've been testing behaviour using a very dumb program which you can get from http://carlh.net/software/denormals.tar.gz I've also been testing plugins using a primitive torture tester that you can get from http://carlh.net/software/ or on github via git@github.com:cth103/plugin-torture.git Any comments? Best Carl