<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - i965/fs: copy propagate should propagate bitwise not into logic operations" href="https://bugs.freedesktop.org/show_bug.cgi?id=89970#c4">Comment # 4</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - i965/fs: copy propagate should propagate bitwise not into logic operations" href="https://bugs.freedesktop.org/show_bug.cgi?id=89970">bug 89970</a> from <a class="email" href="mailto:idr@freedesktop.org" title="Ian Romanick <idr@freedesktop.org>"> Ian Romanick</a> <pre>At the time, we generated intBitsToFloat(b & floatBitsToInt(1.0)) to do b2f conversions. Since b could only be 0 or -1, ~b & 0x38f00000 produces the same possible values as -b & 0x37f00000. However, we now emit float(-b) instead, so I don't think this can occur anymore. Maybe generating ~b & 0x3f800000 (BDW+) or -b & 0x38f00000 (SNB - HSW) for float(!b) is better? Right now there's a late optimization in nir_opt_algebraic that does this: (('b2f(is_used_more_than_once)', ('inot', a)), ('bcsel', a, 0.0, 1.0)), (('fneg(is_used_more_than_once)', ('b2f', ('inot', a))), ('bcsel', a, -0.0, -1.0)), In at least some cases, this results in some extra load-immediate instructions mov(16) g16<1>D 1065353216D { align1 1H }; mov.nz.f0(16) null<1>D g8<8,8,1>D { align1 1H }; (-f0) sel(16) g126<1>UD g16<8,8,1>UD 0x00000000UD { align1 1H }; Which also seems dumb. This should be mov.z.f0(16) null<1>D g8<8,8,1>D (-f0) sel(16) g126<1>F g8<8,8,1>F 1.0F</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the QA Contact for the bug.</li> </ul> </body> </html>