[wrs]

The most obvious general case (to me) is reading an uninitialized local variable in a loop. If uninitialized has to be the same value every time, you’d have to allocate a register or stack space to ensure the value was the same on every iteration. Instead, you’d don’t have to allocate anything, just use whatever value is in any register that’s handy. (By this logic you can also start pruning code, by picking the “most optimal” value for the uninitialized variable.)