On Mon, Dec 28, 2009 at 08:48:22PM +0100, Aurelien Jarno wrote: > On Mon, Dec 28, 2009 at 11:06:20AM -0800, Richard Henderson wrote: > > On 12/24/2009 07:18 AM, Aurelien Jarno wrote: > >> My main concern about this patch is that I don't really understand why > >> the current fp exceptions, the current rounding mode or flush_to_zero > >> mode are stored in FP_STATUS. I think it would be better to have > >> dedicated variable(s) in the cpu state structure, as it is done in other > >> emulated architectures. > > > > The internal format for these features is quite different (in terms of > > bit ordering) than the native Alpha format. If I were to be forcing the > > bits back into the Alpha format after each operation, that would be far > > more shifting and masking than only doing the conversion to Alpha format > > when the FPCR register is read or written. At present I'm only saving a > > value and ORing it back in > > > > However, if you're convinced I should keep things in Alpha format all > > the time, I can rearrange the patch along those lines. > > > > If the format is too different, you should still use a dedicated > variable in the cpu state. Thinking more, there is no guarantee that > FP_STATUS is not overriden by another thread (or another CPU in system > mode), if it's value is set in one TB, and read back in another TB.
Forget that part, there is actually one FP_STATUS per CPU, so it should work. My grep didn't work due to the #define... > Also there is no need to save FP_STATUS and restore it. It should be set > to 0, and the result should be ORed with the dedicated variable. > > -- > Aurelien Jarno GPG: 1024D/F1BCDB73 > aurel...@aurel32.net http://www.aurel32.net -- Aurelien Jarno GPG: 1024D/F1BCDB73 aurel...@aurel32.net http://www.aurel32.net
