It seems the hardware behavior for this is as per-spec and we are
supposed to identify as active entire quads. Particularly, there
are some derivative tests with dynamic control flow that use
subgroup ballot and require this.
However, we still need to exclude terminted lanes (OpTerminate). For
that, we keep track of the sample mask at the start of a fagment
shader start and compare it with the current sample mask.
Fixes: ('broadcom/compiler: support subgroup reduction operations from fragment shaders')
Fixes: dEQP-VK.glsl.derivate.dynamic_loop.*
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27409>
Iago Toral Quiroga
cc7934a89b