On Mon, Feb 5, 2018 at 5:40 AM, Iago Toral Quiroga <ito...@igalia.com> wrote: > Otherwise loop unrolling will fail to see the actual cost of > the unrolling operations when the loop body contains 64-bit integer > instructions, and very specially when the divmod64 lowering applies, > since its lowering is quite expensive. > > Without this change, some in-development CTS tests for int64 > get stuck forever trying to register allocate a shader with > over 50K SSA values. The large number of SSA values is the result > of NIR first unrolling multiple seemingly simple loops that involve > int64 instructions, only to then lower these instructions to produce > a massive pile of code (due to the divmod64 lowering in the unrolled > instructions). > > With this change, loop unrolling will see the loops with the int64 > code already lowered and will realize that it is too expensive to > unroll. > > v2: Run nir_algebraic first so we can hopefully get rid of some of > the int64 instructions before we even attempt to lower them. > --- > > For reference, I captured execution times for the CTS tests that > raised the problem. This is with debug builds of Mesa and CTS so > they are not ideal, but I think they are sufficient to see the > imapact of the patch. > > With this patch: 52s > With this v1: 56s > With master: 1m:38s (*) > > (*) This is actually a significant improvement that has happened in > master since we sent the original patch. Originally, the tests would > just hang forever trying to compile.
Seems like a step in the right direction. Reviewed-by: Matt Turner <matts...@gmail.com> _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
