[AIE2P] Allow spilling vector/accumulator registers to registers instead of memory #688
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Ideally, we should extend with SWP metrics.
F-Stuckmann
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| return {{AIE2P::VST_dmx_sts_x_spill, AIE2P::sub_bfp16_x}, | ||
| {AIE2P::VST_E_SPILL, AIE2P::sub_bfp16_e}}; | ||
| case AIE2P::VLDA_512_COMPOSED_REG_SPILL: | ||
| return {}; |
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This says 'nothing to expand' All other cases return something, so I'm wondering whether this should fall under
if (!MI.isPseudo()) in the top of the function
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| // // Ignore Reg Pressure Set ID | ||
| const unsigned PSID = i; | ||
| if (std::find(IgnorePressureSetIDs.begin(), IgnorePressureSetIDs.end(), |
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Discussed offline, maybe we should try a single target hook, to which we pass the ID. All IDs a given by an enum, so it should be easy for the target to handle them.
| Opcode = AIE2P::ST_R_SPILL; | ||
| SrcReg = ScratchReg; | ||
| IsKill = true; | ||
| } else if (&AIE2P::spill_vec512_to_compositeRegClass == RC) { |
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I'm wondering why we don't use regClassMatches() here.
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Creating a combined register class for vector and accumulator registers changes the machine scheduling behavior because the combined register class is now used for register pressure calculation in the machine scheduler.
Therefore, vector and accumulator registers are considered as a single register pressure class and thus the machine scheduler ever so slightly changes the scheduling. This scheduling change changes register liveliness and causes spilling (sometimes even in the innermost loop).
To mitigate this:
Things to update in this PR:
P.S. For my sanity I continue #678 here