The phi construction algorithm used for interval reconstruction is complicated by

The phi construction algorithm used for interval reconstruction is complicated by
two address instructions.  We need to keep track of things we've processed AS USES
independetly of whether we've processed them as defs.

This fixes all known miscompilations when reconstruction is turned on.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61802 91177308-0d34-0410-b5e6-96231b3b80d8