Working on this.
Created attachment 30054 [details] work in progress
Created attachment 30070 [details] patch for perf testing
Created attachment 30071 [details] Perf testing results Appears to be about 0.8% speedup overall, but possible significant slowdown on bitwise-and and spectral-norm. Then again those two are so fast it may be noise.
In addition to possible slowdowns, nbody takes a 1.5% hit.
Created attachment 30075 [details] patch
http://trac.webkit.org/changeset/43358