[X86][SelectionDAG] Fix the Gather's base and index by modifying the Scale value #137813
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… Node. Using the approach to update the Scale if SHL Opcode and followed by truncate.
… Node. Using the approach to update the Scale if SHL Opcode and followed by truncate.
…7/llvm-project into gatherMultipleOccurrence
…7/llvm-project into gatherMultipleOccurrence
…7/llvm-project into gatherMultipleOccurrence
…7/llvm-project into gatherMultipleOccurrence
…7/llvm-project into gatherMultipleOccurrence
…007/llvm-project into gatherMultipleOccurrence
… identify Signed bits.
…7/llvm-project into gatherMultipleOccurrence
RKSimon
reviewed
May 2, 2025
| DCI.AddToWorklist(N); | ||
| return SDValue(N, 0); | ||
| } | ||
| uint64_t ScaleAmt = Scale->getAsZExtVal(); |
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move this up and reuse in Log2_32 check - we should probably assert that ScaleAmt is a power of 2 as well
| } | ||
| uint64_t ScaleAmt = Scale->getAsZExtVal(); | ||
| if (auto MinShAmt = DAG.getValidMinimumShiftAmount(Index)) { | ||
| if (*MinShAmt >= 1 && (*MinShAmt + Log2_64(ScaleAmt)) < 4 && |
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merge Log2_64 call with the existing Log2_32 call
| // if (TLI.SimplifyDemandedBits(Index, DemandedBits, DCI)) { | ||
| // return SDValue(N, 0); | ||
| // } | ||
| // } |
| unsigned IndexWidth = Index.getScalarValueSizeInBits(); | ||
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| // Shrink indices if they are larger than 32-bits. | ||
| // Only do this before legalize types since v2i64 could become v2i32. | ||
| // FIXME: We could check that the type is legal if we're after legalize | ||
| // types, but then we would need to construct test cases where that happens. | ||
| if (IndexWidth > 32 && DAG.ComputeNumSignBits(Index) > (IndexWidth - 32)) { | ||
| unsigned ComputeNumSignBits = DAG.ComputeNumSignBits(Index); | ||
| if (Index.getOpcode() == ISD::SHL) { |
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All this code needs moving inside the IndexWidth > 32 check - needs commenting as well
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✅ With the latest revision this PR passed the C/C++ code formatter. |
RKSimon
approved these changes
May 6, 2025
| // Shrink indices if they are larger than 32-bits. | ||
| // Only do this before legalize types since v2i64 could become v2i32. | ||
| // FIXME: We could check that the type is legal if we're after legalize | ||
| // types, but then we would need to construct test cases where that happens. | ||
| if (IndexWidth > 32 && DAG.ComputeNumSignBits(Index) > (IndexWidth - 32)) { | ||
| // \ComputeNumSignBits value is recomputed for the shift Index | ||
| if (IndexWidth > 32 && ComputeNumSignBits > (IndexWidth - 32)) { |
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Probably better if you can move everything inside if (IndexWidth > 32)
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@RKSimon, Done. Moved the code inside the if (IndexWidth > 32)
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@RKSimon Can you please merge my changes? Thanks |
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Fix the Gather's base and index for one use or multiple uses of Index Node. Using the approach to update the Scale if SHL Opcode and followed by truncate.
PR closed : #134979