SPIR-V is used in both OpenCL and Vulkan. OpenCL allows the use of Kernel execution models and forbids the use of the shader execution modes and GLCompute. Vulkan does the opposite.
Basically, both OpenCL and Vulkan needed an intermediate language, and they had need for about 95% of the same constructs. But there were some things unique to each one. So they share the same language, but you cannot shove the same SPIR-V code at both.