USER-DPD: performance optimizations to ssa_update() in fix_shardlow Overall improvements range from 2% to 18% on our benchmarks 1) Newton has to be turned on for SSA, so remove those conditionals 2) Rework the math in ssa_update() to eliminate many ops and temporaries 3) Split ssa_update() into two versions, based on DPD vs. DPDE 4) Reorder code in ssa_update_*() to reduce register pressure