Spill metric
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A spill metric is a heuristic metric used by register allocators to decide which registers to spill. Popular spill metrics are:
- cost / degree - introduced in Chaitin's algorithm
- cost / degree2 - emphasizes the spill's effect on neighbours
- cost - emphasizes run time
- minimising number of spill operations
Where cost is the estimated cost of spilling a value from registers into memory.