nir: add divergence analysis pass.

This pass expects the shader to be in LCSSA form.
The algorithm is based on 'The Simple Divergence Analysis' from
Diogo Sampaio, Rafael De Souza, Sylvain Collange, Fernando Magno Quintão Pereira.
Divergence Analysis. ACM Transactions on Programming Languages and Systems (TOPLAS)

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
17 jobs for !918 with divergence in 34 minutes and 29 seconds (queued for 21 minutes and 43 seconds)
detached
Status Name Job ID Coverage
  Containers Build
passed debian #518725

00:00:28

 
  Build+Test
passed meson-arm64 #518734

00:01:29

passed meson-armhf #518733

00:02:10

passed meson-clang #518727

00:07:11

passed meson-clover #518731

00:11:55

passed meson-i386 #518735

00:04:22

passed meson-main #518730

00:12:08

passed meson-swr-glvnd #518726

00:06:16

passed meson-vulkan #518732

00:02:15

passed scons-llvm #518737

00:05:26

passed scons-nollvm #518736

00:01:57

passed scons-swr #518728

00:09:14

passed scons-win64 #518729

00:07:50

 
  Test
passed test-llvmpipe-gles2 1/4 #518738

00:03:33

passed test-llvmpipe-gles2 2/4 #518739

00:06:00

passed test-llvmpipe-gles2 3/4 #518740

00:04:18

passed test-llvmpipe-gles2 4/4 #518741

00:04:09