-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 04/06/2011 08:51 PM, Matt Turner wrote: > On Thu, Apr 7, 2011 at 3:06 AM, Tom Stellard <tstel...@gmail.com> wrote: > > I don't know anything about this code, but I just want to verify that > T0 (tee zero) and TO (tee oh) are different things and are used in the > right places.
I think they're supposed to be the same. That is, we should s/TO/T0/. It has always seemed silly that o and 0 are so close on qwerty keyboards. >> +/** >> + * This pass replaces CMP T0, T1 T2 T0 with MOV TO, T2 when the CMP >> + * instruction is the first instruction to write to register T0. The are >> + * several lowering passes done in GLSL IR (e.g. branches and >> + * relative addressing) that create a large number of conditional >> assignments >> + * that ir_to_mesa converts to CMP instructions like the one mentioned >> above. >> + * >> + * Here is why this conversion is safe: >> + * CMP TO, T1 T2 T0 can be expanded to: >> + * if (T1 < 0.0) >> + * MOV T0, T2; >> + * else >> + * MOV T0, TO; >> + * >> + * If (T1 < 0.0) evaluates to true then our replacement MOV T0, T2 is the >> same >> + * as the original program. If (T1 < 0.0) evaluates to false, executing >> + * MOV T0, T0 will store a garbage value in T0 since T0 is uninitialized. >> + * Therefore, it doesn't matter that we are replacing MOV T0, T0 with MOV >> TO, T2 >> + * because any instruction that was going to read from T0 after this was >> going >> + * to read a garbage value anyway. > > I see "This pass replaces CMP T0, T1 T2 T0" but also "CMP TO, T1 T2 T0 > can be expanded to" where the first has T0 twice and the second has TO > and T0. And a few other seemingly strange occurrences of TO also. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org/ iEYEARECAAYFAk2eEVgACgkQX1gOwKyEAw/1PACdF9At3TGvBtpT0dlYi3+B+qSe qdkAn0QSe5LG0sig3SZJbQLc+GQJBXbQ =6Bll -----END PGP SIGNATURE----- _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
