[AIE2P] Optimize G_PHI regbankselect for fifo/acc #314
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andcarminati
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abhinay-anubola,
abnikant,
F-Stuckmann,
gbossu,
katerynamuts,
khallouh,
konstantinschwarz,
martien-de-jong,
niwinanto,
SagarMaheshwari99 and
stephenneuendorffer
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| # Test 3: The instruction %19:_(p0) = G_PHI %0(p0), %bb.0, %27(p0), %bb.1 | ||
| # should not be mapped to accregbank. The result of the PHI node is used by an instruction | ||
| # that is considered an `accululator-use instruction` but the considered result is just a scalar |
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Oh, did I really write this? Good catch!
andcarminati
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| bb.2: | ||
| PseudoRET implicit $lr | ||
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Nit: Maybe add a test where a PHI is used both as a PHI and an ACC. I think we will favour the FIFO mapping at this point.
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Do you mean by both FIFO and ACC? Yes, we should favor the FIFO because we check it first. I hope we will not face this situation, according to the benchmarks I saw, what do you think?
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| @@ -966,6 +976,36 @@ AIE2PRegisterBankInfo::getInstrMapping(const MachineInstr &MI) const { | |||
| } | |||
| return AIEBaseRegisterBankInfo::getInstrMapping(MI); | |||
| } | |||
| case TargetOpcode::G_PHI: { | |||
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This is a really special-case to handle. If we map to vector reg bank, we may block optimal SWP scheduling's after. This is also a special case because one single PHI node may contain inputs mapped to fifo, accumulator and vector bank at the same time. The way it is mapped is also different, we handle only the output and inputs are related the inputs.
Observation: this PR should include more tests after merging more fifo intrinsics.