[fzltrp]

> Sure, building an IR from scratch is fun. But making it truly cross-platform and ready for many usages is really hard.

It's not that hard, as long it remains as close as possible to the source language (ie. GLSL). Iow, as the OP is advocating for, an AST of the shaders. This removes the cost of parsing the source code (but requires on the other hand to validate the AST, so this isn't exactly a complete gain, but definitely an progress compilation wise). However, I suppose that what motivated the choice of using GLSL source directly is the simplicity of the approach: no need to build the GLSL scripts separately. When working with interactive tools, it's a non negligible comfort, imho. Another interesting aspect is the ability to build the scripts dynamically, like people do with SQL. I wonder if this approach is used by professional game studios.