Fix a bad case in gzip where we put lots of things in registers across the

Fix a bad case in gzip where we put lots of things in registers across the
loop, because a IV-dependent value was used outside of the loop and didn't
have immediate-folding capability

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@22798 91177308-0d34-0410-b5e6-96231b3b80d8