DragonEgg is the unique LLVM-powered plug-in for GCC that allows LLVM optimizers and code generators to cooperate with GCC. It's quite interesting but is often overshadowed by LLVM itself and its own C/Objective-C/C++ Clang compiler. DragonEgg isn't widely used at this point but viewed by many as just an interesting experiment. By default DragonEgg will replace the GCC optimizers with those from LLVM, but there's a compiler option to use both the GCC and LLVM optimizers for "ultimate performance."
DragonEgg takes the optimizers and code generators from LLVM and plugs it into GCC, particularly the 4.5 release or newer where the plug-in architecture is available. DragonEgg is what succeeded LLVM-GCC. The goal of DragonEgg is to eventually support all of GCC's languages, but for now it's namely for C, C++, Fortran, and ADA. The compiler front-end of GCC is still used so it's easier to introduce support for new languages here than writing it up with Clang. There's partial support for Google Go, Java, Objective-C, and Objective-C++ languages with GCC. DragonEgg also works for Darwin, FreeBSD, Debian GNU/kFreeBSD, Linux, and OpenBSD platforms. The code generators work for x86, x86_64, and now ARM.
With DragonEgg 3.1, which was released at the same time as LLVM 3.1 and Clang 3.1 earlier this month, there is now:
- Partial support for GCC 4.7. While DragonEgg is just a GCC plug-in, the interfaces aren't stable and require changes from release-to-release it seems. The DragonEgg ADA support here is said to be poor but other languages should work "fairly well." GCC 4.5 and 4.6 series should still work well with this new version of DragonEgg.
- With DragonEgg 3.1 the code generators now work for ARM processors too, rather than just x86/x86_64.
- Better Fortran optimizations.
- Better optimizations for all languages by passing information about type aliasing and type ranges to LLVM optimizers.
- There's finally a regression test suite.
Additional information and download links are available from dragonegg.llvm.org. Now if you didn't look at them already, check out the 11-way compiler comparison benchmarks for the latest Intel hardware.