Revert r111031. The way LLVM defines loop invariance, the property of an

Revert r111031. The way LLVM defines loop invariance, the property of an
expression being loop invariant is not equivalent to the property of
properly dominating the loop header.

Other optimizations have also made this optimization less important.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111160 91177308-0d34-0410-b5e6-96231b3b80d8