Revert "Fix PR24469 resulting from r245025 and re-enable dead store...

Revert "Fix PR24469 resulting from r245025 and re-enable dead store elimination across basicblocks."

This is causing bootstrap problems, e.g.: http://bb.pgr.jp/builders/clang-3stage-i686-linux/builds/2960

This reverts r245195.

llvm-svn: 245402