Add a faster binary search.
Add a faster binary search.

Even with the hash table cache, binary search was still pretty
hot. This can be made even faster with prefetching.

Idea from http://cglab.ca/~morin/misc/arraylayout-v2/

I will suggest moving this to llvm.

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@284594 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld