Which of the following statement about live variable analysis is correct?
1
If value of variable x is at point p could be used along some path in the flow graph starting at p then x is dead at p.
2
It helps in register allocation for basic blocks.
3
After a value is computed in a register, then it is necessary to store that value if it is dead at the end of the block.
4
If all registers are full, then we should use a register with a live value since that value need to be stored.