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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/108552] Linux i386 kernel 5.14 memory corruption for pre_compound_page() when gcov is enabled Date: Fri, 27 Jan 2023 15:13:26 +0000 [thread overview] Message-ID: <bug-108552-4-cdC6wGvENq@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-108552-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108552 --- Comment #26 from Richard Biener <rguenth at gcc dot gnu.org> --- And yes, to IV optimization the gcov counter for the loop body is just another IV candidate that can be used, and in this case it allows to elide the otherwise unused original IV. Now, in principle we should have applied store-motion and not only PRE which would have avoided the issue, not tricking the RA into reloading the value from where we store it in the loop, but the kernel uses -fno-tree-loop-im, preventing that. If you enable that you'd get <bb 7> [local count: 105119324]: __gcov0.prep_compound_page_I_lsm.1755_4 = __gcov0.prep_compound_page[7]; _92 = (long unsigned int) page_12(D); _57 = _92 + 1; _119 = page_12(D) + 40; ivtmp.1762_136 = (unsigned int) _119; <bb 8> [local count: 955630225]: # i_66 = PHI <i_17(8), 1(7)> # ivtmp.1762_6 = PHI <ivtmp.1762_46(8), ivtmp.1762_136(7)> p_15 = (struct page *) ivtmp.1762_6; MEM <struct address_space *> [(union *)p_15 + 12B] = 1024B; MEM[(volatile long unsigned int *)p_15 + 4B] ={v} _57; i_17 = i_66 + 1; ivtmp.1762_46 = ivtmp.1762_6 + 40; if (nr_pages_11 != i_17) goto <bb 8>; [89.00%] else goto <bb 9>; [11.00%] <bb 9> [local count: 105119324]: _73 = (unsigned int) nr_pages_11; _163 = _73 + 4294967294; _159 = (long long int) _163; _1 = __gcov0.prep_compound_page_I_lsm.1755_4 + 1; PROF_edge_counter_74 = _1 + _159; __gcov0.prep_compound_page[7] = PROF_edge_counter_74; which is the desired optimization, handling the counter in the loop like an induction variable instead of going through memory.
next prev parent reply other threads:[~2023-01-27 15:13 UTC|newest] Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-01-26 8:00 [Bug c/108552] New: " feng.tang at intel dot com 2023-01-26 8:01 ` [Bug c/108552] " feng.tang at intel dot com 2023-01-26 8:02 ` [Bug target/108552] " pinskia at gcc dot gnu.org 2023-01-26 8:05 ` pinskia at gcc dot gnu.org 2023-01-26 8:13 ` feng.tang at intel dot com 2023-01-26 8:19 ` pinskia at gcc dot gnu.org 2023-01-26 11:35 ` feng.tang at intel dot com 2023-01-26 11:37 ` feng.tang at intel dot com 2023-01-26 11:39 ` feng.tang at intel dot com 2023-01-26 16:03 ` feng.tang at intel dot com 2023-01-26 16:07 ` feng.tang at intel dot com 2023-01-26 19:06 ` pinskia at gcc dot gnu.org 2023-01-26 19:22 ` torvalds@linux-foundation.org 2023-01-27 9:52 ` ubizjak at gmail dot com 2023-01-27 10:47 ` ubizjak at gmail dot com 2023-01-27 10:56 ` ubizjak at gmail dot com 2023-01-27 12:23 ` ubizjak at gmail dot com 2023-01-27 12:29 ` ubizjak at gmail dot com 2023-01-27 12:31 ` [Bug tree-optimization/108552] " ubizjak at gmail dot com 2023-01-27 12:51 ` ubizjak at gmail dot com 2023-01-27 12:52 ` ubizjak at gmail dot com 2023-01-27 13:17 ` jakub at gcc dot gnu.org 2023-01-27 13:40 ` ubizjak at gmail dot com 2023-01-27 14:14 ` jakub at gcc dot gnu.org 2023-01-27 14:59 ` rguenth at gcc dot gnu.org 2023-01-27 15:01 ` rguenth at gcc dot gnu.org 2023-01-27 15:13 ` rguenth at gcc dot gnu.org [this message] 2023-01-27 15:15 ` jakub at gcc dot gnu.org 2023-01-27 15:18 ` rguenth at gcc dot gnu.org 2023-01-27 15:20 ` jakub at gcc dot gnu.org 2023-01-27 17:00 ` torvalds@linux-foundation.org 2023-01-27 17:05 ` torvalds@linux-foundation.org 2023-01-27 17:15 ` torvalds@linux-foundation.org 2023-01-27 17:19 ` jakub at gcc dot gnu.org 2023-01-27 17:29 ` jakub at gcc dot gnu.org 2023-01-27 22:30 ` vmakarov at gcc dot gnu.org 2023-01-28 14:20 ` feng.tang at intel dot com 2023-01-28 14:27 ` feng.tang at intel dot com 2023-01-28 14:29 ` feng.tang at intel dot com 2023-01-28 23:40 ` hubicka at ucw dot cz 2023-01-29 10:08 ` jakub at gcc dot gnu.org 2023-01-30 7:05 ` rguenth at gcc dot gnu.org 2023-01-30 7:09 ` rguenth at gcc dot gnu.org 2023-01-30 8:06 ` torvalds@linux-foundation.org 2023-01-30 8:30 ` jakub at gcc dot gnu.org 2023-01-30 8:44 ` rguenth at gcc dot gnu.org 2023-01-30 8:46 ` rguenther at suse dot de 2023-01-30 18:54 ` torvalds@linux-foundation.org
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