From 43502b83135b5a368972e6c5f57f945d002e7c50 Mon Sep 17 00:00:00 2001 From: Jeff Law Date: Sun, 19 Nov 2017 13:15:45 -0700 Subject: [PATCH] tree-ssa-dom.c (record_equivalences_from_phis): Fix handling of degenerates resulting from ignoring an edge. * tree-ssa-dom.c (record_equivalences_from_phis): Fix handling of degenerates resulting from ignoring an edge. From-SVN: r254938 --- gcc/ChangeLog | 5 +++++ gcc/tree-ssa-dom.c | 21 ++++++++++++++++----- 2 files changed, 21 insertions(+), 5 deletions(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index ae05dacf791..5ce981d0871 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2017-11-19 Jeff Law + + * tree-ssa-dom.c (record_equivalences_from_phis): Fix handling + of degenerates resulting from ignoring an edge. + 2017-11-19 Jan Hubicka PR ipa/81360 diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c index eb85b4a09ad..916d66134c3 100644 --- a/gcc/tree-ssa-dom.c +++ b/gcc/tree-ssa-dom.c @@ -1011,6 +1011,7 @@ record_equivalences_from_phis (basic_block bb) tree rhs = NULL; size_t i; + bool ignored_phi_arg = false; for (i = 0; i < gimple_phi_num_args (phi); i++) { tree t = gimple_phi_arg_def (phi, i); @@ -1021,10 +1022,14 @@ record_equivalences_from_phis (basic_block bb) if (lhs == t) continue; - /* If the associated edge is not marked as executable, then it - can be ignored. */ + /* We want to track if we ignored any PHI arguments because + their associated edges were not executable. This impacts + whether or not we can use any equivalence we might discover. */ if ((gimple_phi_arg_edge (phi, i)->flags & EDGE_EXECUTABLE) == 0) - continue; + { + ignored_phi_arg = true; + continue; + } t = dom_valueize (t); @@ -1049,9 +1054,15 @@ record_equivalences_from_phis (basic_block bb) a useful equivalence. We do not need to record unwind data for this, since this is a true assignment and not an equivalence inferred from a comparison. All uses of this ssa name are dominated - by this assignment, so unwinding just costs time and space. */ + by this assignment, so unwinding just costs time and space. + + Note that if we ignored a PHI argument and the resulting equivalence + is SSA_NAME = SSA_NAME. Then we can not use the equivalence as the + uses of the LHS SSA_NAME are not necessarily dominated by the + assignment of the RHS SSA_NAME. */ if (i == gimple_phi_num_args (phi) - && may_propagate_copy (lhs, rhs)) + && may_propagate_copy (lhs, rhs) + && (!ignored_phi_arg || TREE_CODE (rhs) != SSA_NAME)) set_ssa_name_value (lhs, rhs); } }