Q10Compiler Design
Question
Define Register Allocation.
Answer
Register Allocation is the compiler phase that maps program variables (and temporaries) in intermediate code to a limited number of machine registers, minimizing costly memory accesses.
Register allocation is the process of assigning machine registers to the variables and temporaries used in a program's intermediate representation. Since machine registers are limited and much faster than memory, keeping frequently used values in registers significantly improves execution speed.
The key challenge is that the number of live variables at any point may exceed the number of available registers. When a variable must be stored in memory due to insufficient registers, it is 'spilled' to the stack. Register allocation is typically formulated as a graph coloring problem: build an interference graph where nodes represent variables and edges connect live-range-overlapping variables; then color the graph with k colors (k = number of registers) such that no two adjacent nodes share the same color.