http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59934
--- Comment #8 from Jeffrey A. Law <law at redhat dot com> --- Setting TREE_NO_WARNING seems wrong to me. That would really seem better suited for cases where we have already warned on that expression and don't want to warn on it again. This case is pretty different. In effect threading isolates paths. Path isolation can/will expose out-of-bounds array indexing that is missed by the insanely lame code in tree-vrp.c.
