Lesson 10--Register Allocation Flashcards
True or False: Register allocation is a must for CISC
False. All operands are in memory and there are long instructions to retrieve and use them.
True or False: Register allocation is a must for RISC
True
True or False: Register allocation is a must for VLIW
True
True or False: Register allocation saves energy on embedded processors
True. It reduces memory accesses, which are energy hogs.
Register allocation
Determines which of the values should be in registers at each execution point
Register assignment
Determines which register should be used by each allocated value
Goal of register allocation
To minimize the traffic between the CPU and the memory hierarchy
Three parameters that are positively impacted by better register allocation
Speed
Code size
energy efficiency
gen
variable is newly defined
kill
old value is no longer accessible
def
on the left hand side
use
on the right hand side
live
variable will be used again
dead
variable will never be used again
web
The live range for each value