Stages a live range passes through during greedy register allocation.
Declared in <llvm/CodeGen/RegAllocEvictionAdvisor.h>
enum LiveRangeStage;Live ranges pass through a number of stages as we try to allocate them. Some of the stages may also create new live ranges:
Region splitting.
Per-block splitting.
Local splitting.
Spilling.
Ranges produced by one of the stages skip the previous stages when they are dequeued. This improves performance because we can skip interference checks that are unlikely to give any results. It also guarantees that the live range splitting algorithm terminates, something that is otherwise hard to ensure.
| Name | Description |
|---|---|
RS_New | Newly created live range that has never been queued. |
RS_Assign | Only attempt assignment and eviction. Then requeue as RS_Split. |
RS_Split | Attempt live range splitting if assignment is impossible. |
RS_Split2 | Attempt more aggressive live range splitting that is guaranteed to make progress. This is used for split products that may not be making progress. |
RS_Spill | Live range will be spilled. No more splitting will be attempted. |
RS_Done | There is nothing more we can do to this live range. Abort compilation if it can't be assigned. |