not safe in general because the immediate could be an arbitrary
value that does not fit in a 32-bit pcrel displacement.
Conservatively fall back to loading the value into a register
and calling through it.
We still do the optzn on X86-32.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@67142 91177308-0d34-0410-b5e6-96231b3b80d8