On Thu, Oct 4, 2012 at 8:57 AM, Steven Bosscher <stevenb....@gmail.com> wrote: > On Thu, Oct 4, 2012 at 5:30 AM, Vladimir Makarov <vmaka...@redhat.com> wrote: >> I was going to look at this code too but I was interesting in generation of >> less points and live ranges. It is strange that in my profiles, >> remove_some_program_points_and_update_live_ranges takes 0.6% of compiler >> time on these huge tests. So I was not interesting to speed up the >> function and may be therefore you have no visible change in compilation >> time. > > Right. The compression algorithm doesn't care much about the initial > number of program points, only about the number of live ranges before > and after compression. I had expected a bigger effect on the number of > live ranges before compression. > > 0.6% sounds really very different from my timings. How much time does > create_start_finish_chains take for you? > > >> I don't object the idea of the patch. I need some time to look at it (the >> different results on a function is a bit scary for me) and check simulator >> times on other tests. > > Understood.
BTW, it would be great if you can also look at this additional patch hunk: @@ -994,8 +1044,8 @@ lra_create_live_ranges (bool all_p) curr_point = 0; point_freq_vec = VEC_alloc (int, heap, get_max_uid () * 2); lra_point_freq = VEC_address (int, point_freq_vec); - FOR_EACH_BB (bb) - process_bb_lives (bb); + FOR_EACH_BB_REVERSE (bb) + process_bb_lives (bb, curr_point); lra_live_max_point = curr_point; create_start_finish_chains (); if (lra_dump_file != NULL) I think this should result in more live ranges being merged. Here's why I think so, based on my far worse understanding of this code than yours, so forgive me if I'm Completely Wrong :-) process_bb_lives walks insns in the basic block from last to first, so say you have a basic block chain 1->2->3, and each block has 4 insns, then AFAIU the program points in block 1 will be [4,3,2,1], in block 2 it will be [8,7,6,5], and in block 3 it will be [12,11,10,9]. Say a reg is used in block 3 at point 11, and set in block at point 3. Then this reg will have a live range chain [3-1],[8-5],[12-11]. If you visit the basic blocks in reverse order, the program points will be: 1:[12,11,10,9], 2:[8,7,6,5], 3:[4,3,2,1]. Now the same reg will be set at point 11 and used at point 3, and the live range chain will be just [11-3]. I'm experimenting with this extra hunk and report back here. Ciao! Steven
