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tree-ssa-dom.c (record_equivalences_from_phis): Fix handling of degenerates resulting from ignoring an edge.

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* tree-ssa-dom.c (record_equivalences_from_phis): Fix handling
        of degenerates resulting from ignoring an edge.

From-SVN: r254938
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Jeff Law 2017-11-19 13:15:45 -07:00 committed by Jeff Law
parent 8a4a6d2e84
commit 43502b8313
2 changed files with 21 additions and 5 deletions
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gcc/ChangeLog
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@ -1,3 +1,8 @@
2017-11-19 Jeff Law <law@redhat.com>
* tree-ssa-dom.c (record_equivalences_from_phis): Fix handling
of degenerates resulting from ignoring an edge.
2017-11-19 Jan Hubicka <hubicka@ucw.cz>
PR ipa/81360

19
gcc/tree-ssa-dom.c
View File

@ -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)
{
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);
}
}