[RFC][RISCV] Set enableSpillageCopyElimination #132035
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…y EnableSpillageCopyElimination
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Glancing at the code, I see no obvious reason we can't turn this on. As noted, we'd need to check compile time, and perf impact, but I don't see any blockers beyond that. It's a slightly weird pattern to see in code, but if we're seeing it, and you seem to be saying we are, why not? |
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This is an additional optimisation in MachineCopyPropagation that is currently only enabled for PPC. After spotting it looking at something else with MCP and trying it out, I see it does indeed clear at least some instances of register value shuffling in llvm-test-suite. The test case I pulled out isn't necessarily the best one, and may or may not make more sense as .mir - I just grabbed something to demonstrate the impact for discussion.
Posting as RFC in case anyone else has looked at this. We would want to check any compile time impact is manageable. It's worth noting the optimisation relies on checking TII.isCopyInstr quite a lot, so it's not impossible there is further impact from fleshing out isCopyInstrImpl as started in #132002.