Editing Register allocation (section)

=== Components of register allocation ===
Register allocation consists therefore of choosing where to store the variables at runtime, i.e. inside or outside registers. If the variable is to be stored in registers, then the allocator needs to determine in which register(s) this variable will be stored. Eventually, another challenge is to determine the duration for which a variable should stay at the same location.

A register allocator, disregarding the chosen allocation strategy, can rely on a set of core actions to address these challenges. These actions can be gathered in several different categories:{{sfn|Koes|Goldstein|2009|p=21}}
;Move insertion: This action consists of increasing the number of move instructions between registers, i.e. make a variable live in different registers during its lifetime, instead of one. This occurs in the split live range approach. 
;Spilling: This action consists of storing a variable into memory instead of registers.{{sfn|Bouchez|Darte|Rastello|2007b|p=103}}
;Assignment: This action consists of assigning a register to a variable.{{sfn|Colombet|Brandner|Darte|2011|p=26}}
;Coalescing: This action consists of limiting the number of moves between registers, thus limiting the total number of instructions. For instance, by identifying a variable live across different methods, and storing it into one register during its whole lifetime.{{sfn|Bouchez|Darte|Rastello|2007b|p=103}}
Many register allocation approaches optimize for one or more specific categories of actions.
[[File:Registers CPU i386.png|thumb|300px|Intel 386 registers]]