Implement getSubRegIndex as a linear search on the SubRegTable instead of using a big switch.
Implement getSubRegIndex as a linear search on the SubRegTable instead of using a big switch.

- The search bounds are constant, in the worst case (ARM target) it will scan over 30 uint16_ts.
- This method isn't very hot, I had problems finding a testcase where it's called more than a dozen of times (no perf impact).

git-svn-id: a4a6f32337ebd29ad4763b423022f00f68d1c7b7@151773 91177308-0d34-0410-b5e6-96231b3b80d8

lodyagin/bare_cxx,lodyagin/bare_cxx,lodyagin/bare_cxx,lodyagin/bare_cxx,lodyagin/bare_cxx