How to get SAMPLER2D() binding index?

[lemoon]

bgfx::UniformInfo doesn't contain sampler's binding index(stage).
bgfx::setTexture needs to set stage patameter.

if i have dynamic sampler nums in shader depend on shader define, i have to get binding index parameter so that i can set right stage value to shader.

#if defined(BUMP)
SAMPLER2D(u_bumpTexture,0);
#endif

#if defined(DIFFUSE)
SAMPLER2D(u_diffuseTexture,1);
#endif

#if defined(SPECULAR)
SAMPLER2D(u_specularTexture,2);
#endif

How can i get sampler's binding index form shader if i want to set sampler uniforms automatic?