@Alive vs. @Use Annotation

[D.Sturm]

What is the difference between these two? Does @Alive mean I can only write
the value to a @Def register if that value has already been certainly
overwritten by a @Use value? (or use it for things like comparisons where I
don't write to any register?)

This would explain why AMD64ControlFlow.CondMoveOp declares trueValue as
@Alive and falseValue as @Use,  but then AMD64ControlFlow.FloatCondMoveOp
defines both trueValue and falseValue as @Alive although the code is
otherwise identical to CondMoveOp.

Also this doesn't explain why x and y are @Use in AMD64Compare.CompareOp.


-Daniel