Look at a lot of post process effect in chain :
Depth Of Field->Bloom->MotionBlur->FXAA
Now, add a tone map in it.Since tone map is the only one who need a RGBA32 input texture, does it right to make it first to avoid all other post process to be RGBA32 ? Does it can be done before Bloom to avoid bloom output a RGBA32 texture ?
What is the good way to handle all that without loose perf too much perf ?
DOF, Boom and Motion blur all look much more realistic if they are done before tone-mapping (e.g. an out-of-focus bright point turns into a large disc, or a fast moving bright particle turns into a bright line), but yes, you get much better performance if they are done after tone-mapping.
Personally, if I was making a PC game, I would support both approaches and give the user the option of "HDR Post Processing: Yes/No", etc...
FXAA should always be done after tone-mapping.
In the last game I worked on, we did do most of the post-processing after tone-mapping, for performance reasons. For the bloom, we used the HDR image as an input, but copied it to an RGBA8888 texture with something like output=(HDR*scale)-bias, which acts as a traditional "threshold" pass.