Ingenic, a Chinese SoC CPU vendor, worked with ImgTec to add MXU (their MIPS32 SIMD extension) to MPlayer in an open source fork. However, they seem to insist that you reverse engineer their quirky instruction encodings from a confusing awk script. The only alternative is to actually run all of your source files through the awk script during builds...

I started adding them to the LLVM but lost interest. The instructions are available on the Creator CI20 and the GCW Zero, as well as some new Chinese market tablets from Philips.