On Tue, Sep 1, 2015 at 7:56 PM, Ajit Kumar Agarwal <ajit.kumar.agar...@xilinx.com> wrote: > All: > > The Live ranges info on tree SSA representation is important step towards the > SSA based code motion optimizations. > As the code motion optimization based on the SSA representation effects the > register pressure and reasons for performance > Bottleneck. > > I am proposing the Live range Analysis based on the SSA representation. The > Live range analysis traverses the dominator > Tree. The SSA and phi variables are represented based on dominance frontier > info and the SSA representation reflects > The dominance info. Based on such dominance info Live range Overlapping > Analysis can be derived. > > Variable V intersects W if Vdef dominates the Wdef. The variable v intersects > at point p if Vdef dominates P and Wdef > Dominates the P. If Vdef dominates Wdef and Wdef dominates Udef , then the > Vdef dominates Udef and thus Live range > Of V intersect W and live range W intersect U, thus the live range V > intersects the U. Such dominance info can be used to > Represent the Overlapping Live range Analysis and the register pressure is > derived from Overlapping Live ranges based > On the dominator info inherited from the SSA representation. The SSA > representation is derived based on dominance > Frontier and the traversal of dominator tree based on SSA can derive the > Overlapping Live ranges. > > The above Overlapping Live range info can be used to derive the register > pressure and the optimization based out of tree > Representation can use the above overlapping live ranges to take register > pressure into account.
See tree-ssa-live.c (which computes a conflict graph for SSA coalescing). Richard. > Thanks & Regards > Ajit
