Fix tail-merge pass for dead type-unsafe code

2014-11-19  Tom de Vries  <tom@codesourcery.com>

	Backport from mainline
	PR tree-optimization/62167
	* tree-ssa-tail-merge.c (stmt_local_def): Handle statements with vuse
	conservatively.
	(gimple_equal_p): Don't use vn_valueize to compare for lhs equality of
	assigns.

	* gcc.dg/pr51879-12.c: Add xfails.
	* gcc.dg/pr62167-run.c: New test.
	* gcc.dg/pr62167.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-4_8-branch@217764 138bc75d-0d04-0410-961f-82ee72b054a4