On Mon, Aug 13, 2012 at 10:49 AM, Richard Guenther <richard.guent...@gmail.com> wrote: > On Sun, Aug 12, 2012 at 11:49 PM, Steven Bosscher <stevenb....@gmail.com> > wrote: >> Hello, >> >> This patch tried to use non-clearing memory allocation where possible. >> This is especially important for very large functions, when arrays of >> size in the order of n_basic_blocks or num_ssa_names are allocated to >> hold sparse data sets. For such cases the overhead of memset becomes >> measurable (and even dominant for the time spent in a pass in some >> cases, such as the one I recently fixed in ifcvt.c). >> >> This cuts off ~20% of the compile time for the test case of PR54146 at >> -O1. Not bad for a patch that basically only removes a bunch of >> memsets. >> >> I got another 5% for the changes in tree-ssa-loop-manip.c. A loop over >> an array with num_ssa_names there is expensive and unnecessary, and it >> helps to stuff all bitmaps together on a single obstack if you intend >> to blow them all away at the end (this could be done in a number of >> other places in the compiler). Clearing livein at the end of >> add_exit_phis_var also reduces peak memory with ~250MB at that point >> in the passes pipeline (only to blow up from ~1.5GB peak memory in the >> GIMPLE optimizers to ~3.6 GB in expand, and to ~8.6GB in IRA, but hey, >> who's counting? :-) >> >> Actually, the worst cases are not fixed with this patch. That'd be IRA >> (which consumes ~5GB on the test case, out of 8GB total), and >> tree-PRE. >> >> The IRA case looks like it may be hard to fix: Allocating multiple >> arrays of size O(max_regno) for every loop in init_loop_tree_node. >> >> The tree-PRE case is one where the avail arrays are allocated and >> cleared for every PRE candidate. This looks like a place where a >> pointer_map should be used instead. I'll tackle that later, when I've >> addressed more pressing problems in the compilation of the PR54146 >> test case. > > Hmm, or eaiser, use a vector of size (num_bb_preds) and index it by > edge index.
I have a patch for this. Richard. >> This patch was bootstrapped&tested on powerpc64-unknown-linux-gnu. OK for >> trunk? > > Ok with adjusting the PRE comments according to the above. > > Thanks, > Richard. > >> Kudos to the compile farm people, without them I couldn't even hope to >> get any of this work done! > >> Ciao! >> Steven
