through an invoke instruction.
The original patch for this was written by Mark Seaborn, but I've
reworked his test case into the existing returns_twice test case and
implemented the fix by the prior refactoring to actually run the cost
analysis over invoke instructions, and then here fixing our detection of
the returns_twice attribute to work for both calls and invokes. We never
noticed because we never saw an invoke. =[
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197216 91177308-0d34-0410-b5e6-96231b3b80d8
