two changes:

two changes:
1. Make instcombine always canonicalize trunc x to i1 into an icmp(x&1).  This
   exposes the AND to other instcombine xforms and is more of what the code
   generator expects.
2. Rewrite the remaining trunc pattern match to use 'match', which
   simplifies it a lot.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@67635 91177308-0d34-0410-b5e6-96231b3b80d8