From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2136) id 98E47385842D; Sat, 6 Nov 2021 15:36:13 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 98E47385842D MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Aldy Hernandez To: gcc-cvs@gcc.gnu.org Subject: [gcc r12-4971] path oracle: Do not look at root oracle for killed defs. X-Act-Checkin: gcc X-Git-Author: Aldy Hernandez X-Git-Refname: refs/heads/master X-Git-Oldrev: b3a38d18351788004121e469a8b25504e4a98763 X-Git-Newrev: 4856699eeb2809c50930bafe341a96470877195d Message-Id: <20211106153613.98E47385842D@sourceware.org> Date: Sat, 6 Nov 2021 15:36:13 +0000 (GMT) X-BeenThere: gcc-cvs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 06 Nov 2021 15:36:13 -0000 https://gcc.gnu.org/g:4856699eeb2809c50930bafe341a96470877195d commit r12-4971-g4856699eeb2809c50930bafe341a96470877195d Author: Aldy Hernandez Date: Fri Nov 5 22:25:19 2021 +0100 path oracle: Do not look at root oracle for killed defs. The problem here is that we are incorrectly threading 41->20->21 here: [local count: 56063504182]: _134 = M.10_120 + 1; if (_71 <= _134) goto ; [11.00%] else goto ; [89.00%] ... ... ... [local count: 49896518755]: [local count: 56063503181]: # lb_75 = PHI <_134(41), 1(18)> _117 = mstep_49 + lb_75; _118 = _117 + -1; _119 = mstep_49 + _118; M.10_120 = MIN_EXPR <_119, _71>; if (lb_75 > M.10_120) goto ; [11.00%] else goto ; [89.00%] First, lb_17 == _134 because of the PHI. Second, _134 > M.10_120 because of _134 = M.10_120 + 1. We then assume that lb_75 > M.10_120, but this is incorrect because M.10_120 was killed along the path. This incorrect thread causes the miscompilation in 527.cam4_r. Tested on x86-64 and ppc64le Linux. gcc/ChangeLog: PR tree-optimization/103061 * value-relation.cc (path_oracle::path_oracle): Initialize m_killed_defs. (path_oracle::killing_def): Set m_killed_defs. (path_oracle::query_relation): Do not look at the root oracle for killed defs. * value-relation.h (class path_oracle): Add m_killed_defs. Diff: --- gcc/value-relation.cc | 9 +++++++++ gcc/value-relation.h | 1 + 2 files changed, 10 insertions(+) diff --git a/gcc/value-relation.cc b/gcc/value-relation.cc index f1e46d38de1..a0105481466 100644 --- a/gcc/value-relation.cc +++ b/gcc/value-relation.cc @@ -1235,6 +1235,7 @@ path_oracle::path_oracle (relation_oracle *oracle) m_equiv.m_next = NULL; m_relations.m_names = BITMAP_ALLOC (&m_bitmaps); m_relations.m_head = NULL; + m_killed_defs = BITMAP_ALLOC (&m_bitmaps); } path_oracle::~path_oracle () @@ -1305,6 +1306,8 @@ path_oracle::killing_def (tree ssa) unsigned v = SSA_NAME_VERSION (ssa); + bitmap_set_bit (m_killed_defs, v); + // Walk the equivalency list and remove SSA from any equivalencies. if (bitmap_bit_p (m_equiv.m_names, v)) { @@ -1389,6 +1392,12 @@ path_oracle::query_relation (basic_block bb, const_bitmap b1, const_bitmap b2) relation_kind k = m_relations.find_relation (b1, b2); + // Do not look at the root oracle for names that have been killed + // along the path. + if (bitmap_intersect_p (m_killed_defs, b1) + || bitmap_intersect_p (m_killed_defs, b2)) + return k; + if (k == VREL_NONE && m_root) k = m_root->query_relation (bb, b1, b2); diff --git a/gcc/value-relation.h b/gcc/value-relation.h index 97be3251144..8086f5552b5 100644 --- a/gcc/value-relation.h +++ b/gcc/value-relation.h @@ -233,6 +233,7 @@ private: equiv_chain m_equiv; relation_chain_head m_relations; relation_oracle *m_root; + bitmap m_killed_defs; bitmap_obstack m_bitmaps; struct obstack m_chain_obstack;