Do more addrspacecast transforms that happen for bitcast.

Makes addrspacecast (gep) do addrspacecast (gep) instead.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201376 91177308-0d34-0410-b5e6-96231b3b80d8
[X86] Don't mark movabsq as cheap-as-move - it isn't that cheap.

A simple register copy on X86 is just 3 bytes, whereas movabsq is a 10 byte
instruction. Marking movabsq as not beeing cheap will allow LICM to move it
out of the loop and it also prevents unnecessary rematerializations if the
value is needed in more than one register.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201377 91177308-0d34-0410-b5e6-96231b3b80d8