Loops: yes, but this is supposed to be enforced at the shader compilation point, and it seems that SPIR-V does not prevent describing a shader which is an infinite loop. I did ask codex about this, which output I will not paste here, instead referring readers to 2.11.3 of https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.htm... (warning: very complicated)