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Created by Sebastian Parborg@darkdefende

[AMDGPU][bisected] LLVM commit breaks shader compilation leading to severe performance issues in blender

System information

  • OS: Gentoo Linux
  • GPU: Radeon Pro WX 9100
  • Kernel version: 5.10.4-gentoo
  • Mesa version: Mesa 21.1.0-devel (git-68a785e6)
  • Xserver version (if applicable): 1.20.99.1
  • Desktop manager and compositor: SwayWM (Wayland)

Describe the issue

When opening Blender (tried versions 2.83, 2.9x, and git master) the following is printed to the terminal:

LLVM triggered Diagnostic Handler: Illegal instruction detected: VOP* instruction violates constant bus restriction
renamable $vgpr2 = V_CNDMASK_B32_e32 32768, killed $vgpr2, implicit killed $vcc, implicit $exec
LLVM failed to compile shader
radeonsi: can't compile a main shader part

Which sees like a quite bad error. However it is not yet clear that you are impeded by this until you add a Grease Pencil object to the scene.

  1. Open Blender
  2. Delete the default cube from the scene (press the Delete or X key)
  3. Add a GP object (shift + a -> Grease Pencil -> Monkey)
  4. Now as long as the added GP object is select the error message I posted before is spammed to the terminal and the performance is totally unusable. The selection outline is not rendered either.

Regression

I've bisected this down the the llvm commit: 0045786f146e78afee49eee053dc29ebc842fee1 ([AMDGPU] Select s_cselect)

Now I know this is not a Mesa issue specifically, but I didn't find where to file AMDGPU llvm issues. So I hope filing it here is fine.

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