On 05/12/2017 05:28 AM, Bin Cheng wrote: > Hi, > Aggressive precom could result in larger number loop carried variables, > causes high > register pressure and spilling. One example is the hot loop of > 436.cactusADM, in > which >25 loop carried variables are introduced for the vectorized version > loop, > depending on the vector factor. This patch computes loop register pressure > on tree > ssa using previously introduced interface. It uses the information to prune > chains > with simple heuristic. For example, combined and zero-length chains are > always > allowed; other chains are allowed under register cost; and loop unrolling is > forced > off if register pressure is high. With this patch, the benchmark can be > obvious > improved on AArch64. > > Bootstrap and test on x86_64 and AArch64, is it OK? > > Thanks, > bin > 2017-05-10 Bin Cheng <bin.ch...@arm.com> > > * tree-predcom.c (stor-layout.h, tree-ssa-regpressure.h): New header > files. > (prune_chains): New function. > (tree_predictive_commoning_loop): Call compute_loop_reg_pressure to > compute reg pressure. Prune chains based on reg pressure. Force > to not unroll if reg pressure is high. > SO obviously this will be dependent on the whole set of earlier patches and may need some tweaking if those change. The most concerning part is exposing register classes to this code. If we could avoid that it would be good.
BUt I'm on board with the idea of using an estimated register pressure to tune this stuff a bit. jeff
