Folks may remember from XDS 2008 that I was working on a rewrite of Mesa's GLSL compiler. To make a long story short, let's just say that effort fell over and sank into the swamp.

Last December, I started building another one. I had called the working directory of the first compiler glsl, so this one, being take 2, was called glsl2. After I had been working on it for a couple months, Eric Anholt and Ken Graunke (who has since joined our group at Intel) started working on it with me. We've come a long way.

I expect we'll take some flak for working in semi-secret. I'll take the blame for that one. The first attempt at rewriting the compiler was widely publicized and turned into a disaster. In spite of it being widely publicized, I don't think anyone ever pulled the tree. I decided that I wanted to just keep my head down and work on this one. The announcements can come when there's actually something to announce. I think we're close enough to having something to announce to make it worth the effort.

At this point, the front-end (parsing, semantic checking, generation of the initial high-level IR) is mostly complete. We support all of GLSL 1.20 and most of GLSL 1.30. We've temporarily punted on switch-statements, the float (vs. vec4) variants of the shadow sampler functions, and the "offset" versions of all the texture look-up functions. Each of those is going to require a bit more thought to implement correctly.

Carl Worth has written a preprocessor for us, but it hasn't been integrated into the tree yet. As was mentioned on the Mesa mailing list, without the preprocessor we're passing over 90% of the piglit tests.

There's still a lot left to do.

• Linker: The single biggest thing remaining is the linker. The compiler and the IR are structured such that we can actually have a real linker (instead of just concatenating multiple sources and recompiling), but that means we have to write a real linker.
• More optimizations: Our primary target is i915-class hardware. In order to get GLSL to run on hardware that doesn't have branches, there are a bunch of optimizations, like loop-unrolling, that you have to do. We still need to do some of those.
• Preprocessor: We still have to integrate Carl's preprocessor. I believe that is being done this will still.
• Memory management: Any objects that are no longer needed get dropped on the floor. We leak like a screendoor on a submarine. This was an intentional design decision. I had planned to eventually write some sort of slab allocator. At the end of compilation, the entire slab would be deleted. Eric and Carl have since convinced me to just use talloc.
• Codegen: Eric is writing a back-end that will generate Mesa's existing low-level IR from our IR. I believe this is getting close to being done enough.
• Mesa: Once all that stuff is done, we need to get our stand-alone compiler in the Mesa tree. We're expecting it to live in a branch for a few months while things stabilize. It should make for interesting times.

The primary repo is my GIT tree. Eric, Ken, and Carl all have their own trees, and I pull from them when their stuff is ready.

git://anongit.freedesktop.org/~idr/glsl2

For those interested in help things along, the biggest thing we need are more test cases. We're especially interested in shaders from real applications that are known to work correctly on other drivers. We have a bunch from gstreamer and other projects, but more is better. If you have some shaders and don't mind releasing them under a piglit compatible license, please send them our way.