swift234

SIL: Add a switch_int instruction.

This will help represent cleanup blocks in the grown-up Clang way instead of the childish SILGen way, e.g.:

  retain %x
  retain %y
  ...
break_branch:
  %1 = int_literal 1 : $Builtin.Int64
  br cleanup(%1)
return_branch:
  %2 = int_literal 2 : $Builtin.Int64
  br cleanup(%2)
cleanup(%dest : $Builtin.Int64):
  release %z
  release %y
  switch %dest, case 1: break_dest, case 2: return_dest

Swift SVN r6753