The whole point of my struggles with path64 installation was to see if it made JAGS any faster. So I ran the “Classic BUGS” examples under two different versions of JAGS, one compiled with path64 (with -O3 optimisation) and the other compiled with gcc 4.2.4. Both versions use the same shared libraries. The graph below compares the run times of the two versions on a for a 2.66GHz Intel Core2 Quad CPU. Note that both axes are on a log scale.
The results are bit disappointing. The path64 version has consistently longer run times. The relative time difference is minimal for the longest and most computationally demanding examples (top right hand corner).
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Have you tried using the llvm backend (and associated optimizers) to gcc? Might be worth a try…