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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/106280] New: dom_oracle::register_transitives is expensive for deep dominator trees Date: Wed, 13 Jul 2022 08:29:42 +0000 [thread overview] Message-ID: <bug-106280-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106280 Bug ID: 106280 Summary: dom_oracle::register_transitives is expensive for deep dominator trees Product: gcc Version: 13.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: rguenth at gcc dot gnu.org Target Milestone: --- For testcases like extern int foo (int); int bar(int flag) { int res = 0; #define A \ for (int i = 0; i < 1024; ++i) if (flag) res ^= foo(i); #define B A A A A A A A A A A #define C B B B B B B B B B B #define D C C C C C C C C C C D D D D return res; } the function shows high up in the profiles even at -O1 (via the DOM pass I guess which also has its own share of issues with this). The for (bb = root_bb; bb; bb = get_immediate_dominator (CDI_DOMINATORS, bb)) { ... } walk visits a lot of blocks and I suppose it does that for each block in the dominator chain when that ends in something useful. Another testcase might be of the CFG structure if (a) if (b) if (c) if (d) ... where for each if () we'd walk up the dominator tree. I suggest to limit the walking depth to a constant depth (there is for example --param max-hoist-depth with similar limiting, but for children). There might be similar walks elsewhere in the relation/ranger code.
next reply other threads:[~2022-07-13 8:29 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-07-13 8:29 rguenth at gcc dot gnu.org [this message] 2022-07-14 17:03 ` [Bug tree-optimization/106280] " amacleod at redhat dot com 2022-07-18 20:01 ` cvs-commit at gcc dot gnu.org
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