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From: "crazylht at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/105216] New: [12 regression] 8% regression for m-queens compared to gcc11 O2 Date: Mon, 11 Apr 2022 07:57:34 +0000 [thread overview] Message-ID: <bug-105216-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105216 Bug ID: 105216 Summary: [12 regression] 8% regression for m-queens compared to gcc11 O2 Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: crazylht at gmail dot com Target Milestone: --- Created attachment 52778 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52778&action=edit g++ -O2 main.c;./a.out Regression happens in pass_pre while (posib != UINT_FAST32_MAX) { // The standard trick for getting the rightmost bit in the mask uint_fast32_t bit = ~posib & (posib + 1); posib ^= bit; // Eliminate the tried possibility. uint_fast32_t new_diagl = (bit << 1) | diagl_shifted; uint_fast32_t new_diagr = (bit >> 1) | diagr_shifted; bit |= cols[d]; uint_fast32_t new_posib = (bit | new_diagl | new_diagr); if (new_posib != UINT_FAST32_MAX) { uint_fast32_t lookahead1 = (bit | (new_diagl << (LOOKAHEAD - 2)) | (new_diagr >> (LOOKAHEAD - 2))); uint_fast32_t lookahead2 = (bit | (new_diagl << (LOOKAHEAD - 1)) | (new_diagr >> (LOOKAHEAD - 1))); uint_fast32_t allowed2 = l_rest > (int8_t)0; if(allowed2 && ((lookahead2 == UINT_FAST32_MAX) || (lookahead1 == UINT_FAST32_MAX))) { continue; } if(l_rest == (STORE_LEVEL + 1)) { start_level4[level4_cnt][0] = bit; // cols start_level4[level4_cnt][1] = new_diagl; // diagl start_level4[level4_cnt][2] = new_diagr; // diagr level4_cnt++; continue; } l_rest--; // The next two lines save stack depth + backtrack operations // when we passed the last possibility in a row. // Go lower in the stack, avoid branching by writing above the current // position posibs[d] = posib; d += posib != UINT_FAST32_MAX; // avoid branching with this trick posib = new_posib; // make values current cols[d] = bit; diagl[d] = new_diagl; diagr[d] = new_diagr; rest[d] = l_rest; diagl_shifted = new_diagl << 1; diagr_shifted = new_diagr >> 1; } } d--; posib = posibs[d]; // backtrack ... } For bit |= cols[d]; cols[d] is loop invariant if loop latch from *continue*, GCC11 catches it, GCC12 not.
next reply other threads:[~2022-04-11 7:57 UTC|newest] Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-04-11 7:57 crazylht at gmail dot com [this message] 2022-04-11 8:12 ` [Bug tree-optimization/105216] " pinskia at gcc dot gnu.org 2022-04-11 8:18 ` rguenth at gcc dot gnu.org 2022-04-11 8:35 ` crazylht at gmail dot com 2022-04-11 8:38 ` rguenth at gcc dot gnu.org 2022-04-11 10:08 ` [Bug tree-optimization/105216] [12 regression] 8% regression for m-queens compared to gcc11 O2 on CLX crazylht at gmail dot com 2022-04-11 10:14 ` crazylht at gmail dot com 2022-04-11 10:24 ` rguenther at suse dot de 2022-04-11 12:07 ` crazylht at gmail dot com 2022-04-11 12:13 ` crazylht at gmail dot com 2022-04-12 3:11 ` crazylht at gmail dot com 2022-04-12 6:15 ` crazylht at gmail dot com 2022-04-26 15:08 ` [Bug tree-optimization/105216] [12 regression] 8% regression for m-queens compared to gcc11 O2 on CLX. since r12-3876-g4a960d548b7d7d94 marxin at gcc dot gnu.org 2022-05-06 8:33 ` [Bug tree-optimization/105216] [12/13 " jakub at gcc dot gnu.org 2022-07-26 12:34 ` rguenth at gcc dot gnu.org 2022-12-31 4:30 ` pinskia at gcc dot gnu.org 2023-01-03 1:01 ` crazylht at gmail dot com 2023-05-08 12:24 ` [Bug tree-optimization/105216] [12/13/14 " rguenth at gcc dot gnu.org
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