On Thu, Dec 10, 2015 at 11:11 AM, Jason Ekstrand <ja...@jlekstrand.net> wrote: > > On Dec 10, 2015 6:58 AM, "Francisco Jerez" <curroje...@riseup.net> wrote: >> >> Jason Ekstrand <ja...@jlekstrand.net> writes: >> >> > We aren't using it anymore. >> >> It seems useful to me to be able to represent indirect access as part of >> any instruction source or destination register. >> >> The following: >> >> | mov_indirect g0, g1, a0 >> | foo g2, g0 >> >> and the converse case with indirect destination offset (which you don't >> seem to represent currently) can be implemented by the hardware more >> efficiently using a single instruction in certain cases. The current IR >> is able to represent what the hardware can do, but supporting the >> MOV_INDIRECT instruction only would force us to keep the indirection >> separate from the instruction that uses it, so it seems like a less >> expressive representation to me than the current approach, unless you're >> willing to add _INDIRECT variants of most hardware opcodes. > > Yes and, mostly, no. Yes, you can put an indirect on almost anything but it > has substantial restrictions: > > 1) Destination indirects must be uniform (I'm only 95% sure this is the > case)
Almost true. The Register Region Restrictions page gives an example: > // Example: > mov (16) r[a0.0]:f r10:f > // The above instruction behaves the same as the following two instructions: > mov (8) r[a0.0]:f r10:f > mov (8) r[a0.1]:f r11:f But that's all you get -- you still have to use 1x1 mode. And that behavior changes on BDW: > // Example: > mov (16) r[a0.0]:f r10:f > // The above instruction behaves the same as the following two instructions: > mov (8) r[a0.0]:f r10:f > mov (8) r[a0.0, 8*4]:f r11:f The BRW_VERTICAL_STRIDE_ONE_DIMENSIONAL (0xF) vertical stride is necessary for Vx1 or VxH, and the destination does not have vertical stride. It's also not usable in align16 mode or on src1. _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
