There is no suitable basic block to sink instructions in loops without
exits. The only way an instruction in a loop without exits can be used
is as an incoming value to a PHI. In such cases, the incoming block for
the corresponding value is unreachable.
This fixes PR24013.
Differential Revision: http://reviews.llvm.org/D10903
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241987 91177308-0d34-0410-b5e6-96231b3b80d8
