NIR: Phi nodes, ALU instructions, and BCSELs... oh my!
Roughly speaking, this series applies a pair of code transformations that operate similarly to opt_peel_loop_initial_if
. In my testing, this allows loop unrolling of SPIR-V shaders to occur with the additional BCSEL optimizations introduced in commit 8fb8ebfb.
I'm especially hoping to get feedback from @jekstrand and @tarceri.