Optimized implementation of __clzdi2 and __clzsi2 for ARM. Written in
collaboration with Matt Thomas.

Differential Revision: http://llvm-reviews.chandlerc.com/D2630


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@200394 91177308-0d34-0410-b5e6-96231b3b80d8