16:10 <HdkR> https://community.arm.com/developer/tools-software/graphics/b/blog/posts/killing-pixels---a-new-optimization-for-shading-on-arm-mali-gpus

16:10 <HdkR> Today I just learned about this forward pixel kill feature of Mali. I wonder how that works

16:13 <alyssa> HdkR: I think that blog explains it, no?

16:14 <alyssa> "Calculations already in flight can be terminated at any time if we spot that a later thread will write opaque data to the same pixel location... . By adding a simple FIFO buffer to the start of the pipeline, we can extend the forward pixel kill zone, making it more likely to spot overdraw, and at the same time giving the pipeline the chance to kill threads before they are even started."

16:15 <HdkR> What does it mean to "spot that a later thread will write opaque data" though?

16:16 <HdkR> Is the fifo just a store queue to the tile and it always takes the latest result at some indeterminate commit step?

16:17 <HdkR> Which would mean it is completely a hardware construct and nothing to do on the compiler side?

16:44 <alyssa> 100% hardware

16:44 <alyssa> Software just gets (on Bifrost) a "can kill?" and "can be killed?" bits (like early-z some bits)

16:45 <alyssa> (e.g. a fragment shader that has SSBO writes cannot be killed, but it can still kill)

17:02 <HdkR> That's pretty cute

18:40 <cphealy> Would it be possible to have a method for disabling this like we have for disabling AFBC? The use case would be for various testing purposes.

21:59 <alyssa> cphealy: Yes on Bifrost.

21:59 <alyssa> Unclear on midgard.

22:51 <alyssa> bbrezillon: Rebasing the XML MR now

22:51 <alyssa> I think this is really close to landable, just needs to be passed over the finish line. I'm on it :)

23:04 <alyssa> The C changes look good anyway. So just some bug in the XML I guess

23:16 <alyssa> Hm

23:30 <alyssa> note to self: cleanup Texture Descriptor Is 64b

23:44 <alyssa> ok, that explains v5 being horribly broken

23:45 <alyssa> I guess really I should just audit all 4 XMLs

23:45 <alyssa> instead of trying to play cute games with the diffs