Bitcasts between FP and INT values using direct moves

Bitcasts between FP and INT values using direct moves

This patch corresponds to review:
http://reviews.llvm.org/D15286

This patch was meant to land in revision 255246, but I accidentally uploaded
the patch that corresponds to http://reviews.llvm.org/D15372 in that revision
accidentally.

Thereby, this patch is the actual Bitcasts using direct moves patch, whereas
http://reviews.llvm.org/rL255246 actually corresponds to
http://reviews.llvm.org/D15372.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@255649 91177308-0d34-0410-b5e6-96231b3b80d8