On Mon, 9 Mar 2020, Jakub Jelinek wrote: > Hi! > > As mentioned in the PR, on a largish C++ testcase the compile time > on i686-linux is about 16 minutes on a fast box, mostly spent in > find_base_term recursive calls dealing with very deep chains of preserved > VALUEs during var-tracking. > > The following patch punts after we process many VALUEs (we already have code > to punt if we run into a VALUE cycle). > > I've gathered statistics on when we punt this way (with BITS_PER_WORD, TU, > function columns piped through sort | uniq -c | sort -n): > 36 32 ../../gcc/asan.c _Z29initialize_sanitizer_builtinsv.part.0 > 108 32 _first_test.go reflect_test.reflect_test..import > 1005 32 /home/jakub/src/gcc/gcc/testsuite/gcc.dg/pr85180.c foo > 1005 32 /home/jakub/src/gcc/gcc/testsuite/gcc.dg/pr87985.c foo > 1005 64 /home/jakub/src/gcc/gcc/testsuite/gcc.dg/pr85180.c foo > 1005 64 /home/jakub/src/gcc/gcc/testsuite/gcc.dg/pr87985.c foo > 2534 32 /home/jakub/src/gcc/gcc/testsuite/gcc.dg/stack-check-9.c f3 > 6346 32 ../../gcc/brig/brig-lang.c brig_define_builtins > 6398 32 ../../gcc/d/d-builtins.cc d_define_builtins > 8816 32 ../../gcc/c-family/c-common.c c_common_nodes_and_builtins > 8824 32 ../../gcc/lto/lto-lang.c lto_define_builtins > 41413 32 /home/jakub/src/gcc/gcc/testsuite/gcc.dg/pr43058.c test > Additionally, for most of these (for the builtins definitions tested just > one) I've verified with a different alias.c change which didn't punt but > in the toplevel find_base_term recorded if visited_vals reached the limit > whether the return value was NULL_RTX or something different, and in all > these cases the end result was NULL_RTX, so at least in these cases it > should just shorten the time until it returns NULL. > > Bootstrapped/regtested on x86_64-linux and i686-linux.
OK. Thanks, Richard. > 2020-03-09 Jakub Jelinek <ja...@redhat.com> > > PR rtl-optimization/94045 > * params.opt (-param=max-find-base-term-values=): New option. > * alias.c (find_base_term): Add cut-off for number of visited VALUEs > in a single toplevel find_base_term call. > > --- gcc/params.opt.jj 2020-02-18 08:54:22.560195942 +0100 > +++ gcc/params.opt 2020-03-06 12:56:28.607705143 +0100 > @@ -662,6 +662,10 @@ Max. size of loc list for which reverse > Common Joined UInteger Var(param_max_vartrack_size) Init(50000000) Param > Optimization > Max. size of var tracking hash tables. > > +-param=max-find-base-term-values= > +Common Joined UInteger Var(param_max_find_base_term_values) Init(2000) Param > Optimization > +Maximum number of VALUEs handled during a single find_base_term call. > + > -param=max-vrp-switch-assertions= > Common Joined UInteger Var(param_max_vrp_switch_assertions) Init(10) Param > Optimization > Maximum number of assertions to add along the default edge of a switch > statement during VRP. > --- gcc/alias.c.jj 2020-03-05 15:13:14.391513145 +0100 > +++ gcc/alias.c 2020-03-06 12:59:25.388101668 +0100 > @@ -2005,6 +2005,9 @@ find_base_term (rtx x, vec<std::pair<cse > if (cselib_sp_based_value_p (val)) > return static_reg_base_value[STACK_POINTER_REGNUM]; > > + if (visited_vals.length () > (unsigned) > param_max_find_base_term_values) > + return ret; > + > f = val->locs; > /* Reset val->locs to avoid infinite recursion. */ > if (f) > > Jakub > > -- Richard Biener <rguent...@suse.de> SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
