[DAGCombiner] Add special case fast paths for udiv x,1 and udiv x,-1

udiv x,-1 was going down the (slow) BuildUDIV route resulting in unnecessary shifts.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@336701 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed