On Don, 2012-08-02 at 11:05 +0200, Christian König wrote: > On 02.08.2012 07:51, Michel Dänzer wrote: > > On Mit, 2012-08-01 at 23:28 +0200, Christian König wrote: > >> Using the writemask in the sampler results in packet > >> VGPRS. > > What does that mean? > > The instructions with a destination mask are packing their results, e.g. > when you sample RGBA you get: > R in VGPR0 > G in VGPR1 > B in VGPR2 > A in VGPR3 > > But when you for example mask G&B you get: > R in VGPR0 > G masked > B masked > A in VGPR1 > > So your image sample instruction is only writing 2 VGPRS then.
Ah, so that should be spelled 'packed' then. > > [SNIP] > > Couldn't this incorrectly clobber components of the destination which > > were supposed to be masked? > > No cause it is just an optimization of not fetching unwanted components, > and not masking anything. Hmm, but can't it happen that LLVM assigns destination GPRs containing previous values that need to be preserved according to the TGSI writemask? -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Debian, X and DRI developer _______________________________________________ mesa-dev mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/mesa-dev
