Certainly, but not pointing to Quake code but minigl.
I remember some mesa/gl PPC (or was old AmigaOS 4-minigl / Morphos-tiny-gl ?) code that have altivec related to matrix stuff. Basically find that old mesa stuff (nowadays there's no ppc support from mesa) & try to adapt it to existing old minigl.
But before going Altivec route I would have a C PPC backend that fully supports all float registers from G3/G4 in classic Amiga, so a lot of stuff related to keeping the pipeline happy (as Surgeon did in matrix.c) could be updated to "newer" G3/4.
Another hacky way could be tinker the output asm and move around stuff to be Altivec compliant. Maybe using output code from AmigaOS 4 ->minigl / Morphos stuff and compare with old minigl warpos output.
Sometimes I do stuff like that: Gears demo being a 10% faster using "frsqrte" instead of sqrt/divisions in the loop of "v_GenTexCoords/draw.c". But not of this is used in Quake (anyway gentexcoords is slow)
