Fixup patch for revision rL316070.

Added check that type of CmpConst and source type of trunc are equal
for correct matching of the case when we can set widened C constant
equal to CmpConstant.

  %cond = cmp iN %x, CmpConst
  %tr = trunc iN %x to iK
  %narrowsel = select i1 %cond, iK %t, iK C

Patch by: Gainullin, Artur <artur.gainullin@intel.com>

llvm-svn: 316082