Mesa's GLSL Compiler Improved Significantly Over The Past Year

Matt Turner, an Intel OTC developer and long-time open-source graphics contributor, presented at XDC2014 Bordeaux about progress made with their GLSL compiler. Connor Abbott, fresh out of high school who was an Intel intern this summer, presented his work on the new "NIR" intermediate representation.

Matt Turner highlighted the GLSL compiler improvements made including OpenGL Geometrey Shader support, going from GLSL 1.40 to GLSL 3.30 compliance, a lot of other new GLSL extensions were added, and a ton of optimizations were made over the past year -- especially to Intel's i965 driver back-end.

Optimizations over the past year on their shader test cache show SIMD16 programs increasing from 88.6% to 97.8%, 43k shader samples improved, about a 10% reduction in the number of loops in programs, around 16% cut in the number of basic blocks, and around 92% less CFG calculations. On top of that, many new Steam on Linux games are beginning to just work fine.

Intel developers focusing on the GLSL code are now working on continued optimizations, IR improvements, and other work. Related to that was Connor Abbot's work on the NIR intermediate representation he prototyped over the summer while interning at Intel.

For those wanting to learn about all the low-level details of the talks, you can find Matt's and Connor's slides available in PDF form here and here, respectively.