GLSL_EXT_ray_tracing: The restriction of executeCallableEXT

[ShenQZ]

The restriction of executeCallableEXT described by GLSL_EXT_ray_tracing.txt is different from the Ray Tracing chapter of the Vulkan specification:

GLSL_EXT_ray_tracing.txt:
    Syntax:

        void executeCallableEXT(uint sbtRecordIndex, int callable)

    This function is available only in ray generation, closest-hit, miss, and
    callable stage. Invokes the callable located at 'sbtRecordIndex' in the
    shader binding table. Refer to Ray Tracing chapter of Vulkan specification
    for details.

Vulkan specification:
https://docs.vulkan.org/spec/latest/chapters/raytracing.html
OpExecuteCallableKHR cannot directly call in callable stage by the table of Shader Call Instructions

So which spec we should follow?

[dgkoch]

Both are correct.

The "Shader Call Instructions" table (https://docs.vulkan.org/spec/latest/chapters/raytracing.html#ray-tracing-shader-call) is telling you which shader stages can be directly invoked by the system in response to that shader call instruction.
For example the OpTraceRayKHR instruction can result in Intersection, any-hit, closest hit or miss shaders being invoked, however that does NOT mean that a ray generation shader itself cannot also have an OpExecuteCallableKHR instruction (which results on the callable shader being invoked).