On Wednesday 06 January 2010 14:56:35 Igor Oliveira wrote: > Hi, > > the patches add support to double opcodes in gallium/tgsi. > It just implement some opcodes i like to know if someone has > suggestion about the patches.
Hi Igor, first of all this should probably go into a feature branch because it'll be a bit of work before it's usable. The patches that you've proposed are unlikely what we'll want for double's. Keith, Michal and I discussed this on the phone a few days back and the biggest issue with doubles is that unlike the switch between the integers and floats they actually need bigger registers to accomodate them. Given that the registers in TGSI are untyped and its up to instructions to define the type it becomes hard for drivers to figure out the size of the registers beforehand. The solution that I personally like and what seems to becoming the facto standard when dealing with double support is having double precision values represented by a pair of registers. Outputs are either the pair yx or to the pair wz, where the msb is stored in y/w. For example: Idata 3.0 => (0x4008000000000000) in register r looks like: r.w = 0x40080000 ;high dword r.z = 0x00000000 ;low dword Or: r.y = 0x40080000 ;high dword r.x = 0x00000000 ;low dword All source double inputs must be in xy (after swizzle operations). For example: d_add r1.xy, r2.xy, r2.xy Or d_add r1.zw, r2.xy, r2.xy Each computes twice the value in r2.xy, and places the result in either xy or zw. This assures that the register size stays constant. Of course the instruction semantics are different to the typical 4-component wide TGSI instructions, but that, I think, is a lot less of an issue. z ------------------------------------------------------------------------------ This SF.Net email is sponsored by the Verizon Developer Community Take advantage of Verizon's best-in-class app development support A streamlined, 14 day to market process makes app distribution fast and easy Join now and get one step closer to millions of Verizon customers http://p.sf.net/sfu/verizon-dev2dev _______________________________________________ Mesa3d-dev mailing list Mesa3d-dev@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mesa3d-dev
