Three years ago a small team at Intel took on the task of rewriting the OpenGL Shading Language compiler in Mesa. One of the most fundamental design choices in any compiler is the intermediate representation (IR) used for programs. The IR is the internal data structure used for all program transformations including optimization and code generation. At the time the compiler was designed, a number of alternatives were investigated. In the end, a tree-like IR was selected. With hindsight being 20/20, this talk will present the tree-like IR that was chosen and the issues that have been found with that IR in the interim.