------- Comment #4 from hubicka at ucw dot cz 2009-07-23 16:15 -------
Subject: Re: [4.5 Regression] segfault in useless_type_conversion_p
Hi,
the problem here is in removing virtual PHI. We replace uses of the
virtual PHI results by the corresponding VAR_DECL and send symbol for
renaming. However the replacement is done only for live statements and
we send for renaming only if any live statements are found.
The problem here is that virutal PHI defines vop used by dead statement.
The dead statement however define vop used by live statement. At the
time we are removing the dead statement, live statement gets former PHI
result, now dead in its vuse.
The following patch solves it by simply updating all uses, dead or
alive. It woudl be possible to keep this check and add check into code
deleting dead_statements to update when result of dead PHI is propagated
through.
I am bootsrapping/regtesting this version.
Index: tree-ssa-dce.c
===================================================================
--- tree-ssa-dce.c (revision 150009)
+++ tree-ssa-dce.c (working copy)
@@ -828,9 +828,6 @@ mark_virtual_phi_result_for_renaming (gi
}
FOR_EACH_IMM_USE_STMT (stmt, iter, gimple_phi_result (phi))
{
- if (gimple_code (stmt) != GIMPLE_PHI
- && !gimple_plf (stmt, STMT_NECESSARY))
- continue;
FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
SET_USE (use_p, SSA_NAME_VAR (gimple_phi_result (phi)));
update_stmt (stmt);
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40759
