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[MLIR][Conversion] Vector to LLVM: Remove unneeded vector shuffle #162946

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Merged
merged 4 commits into from
Oct 15, 2025
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Merged

[MLIR][Conversion] Vector to LLVM: Remove unneeded vector shuffle #162946

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[MLIR][Conversion] Vector to LLVM: Remove unneeded vectorshuffle
silee2 Oct 11, 2025
f75fe90
Update comment.
silee2 Oct 13, 2025
b0d476e
Update test.
silee2 Oct 13, 2025
a33e198
Add op fold pattern for llvm.shufflevector and use it for optimizing …
silee2 Oct 14, 2025
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6 changes: 5 additions & 1 deletion mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1723,12 +1723,16 @@ struct VectorBroadcastScalarToLowRankLowering
return success();
}

// For 1-d vector, we additionally do a `vectorshuffle`.
// For 1-d vector, we additionally do a `vectorshuffle` if vector width > 1.
auto v =
LLVM::InsertElementOp::create(rewriter, broadcast.getLoc(), vectorType,
poison, adaptor.getSource(), zero);

int64_t width = cast<VectorType>(broadcast.getType()).getDimSize(0);
if (width == 1) {
rewriter.replaceOp(broadcast, v);
return success();
}
SmallVector<int32_t> zeroValues(width, 0);

// Shuffle the value across the desired number of elements.
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11 changes: 11 additions & 0 deletions mlir/test/Conversion/VectorToLLVM/vector-to-llvm.mlir
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Expand Up @@ -76,6 +76,17 @@ func.func @broadcast_vec1d_from_f32(%arg0: f32) -> vector<2xf32> {

// -----

func.func @broadcast_single_elem_vec1d_from_f32(%arg0: f32) -> vector<1xf32> {
%0 = vector.broadcast %arg0 : f32 to vector<1xf32>
return %0 : vector<1xf32>
}
// CHECK-LABEL: @broadcast_single_elem_vec1d_from_f32
// CHECK-SAME: %[[A:.*]]: f32)
// CHECK: %[[T0:.*]] = llvm.insertelement %[[A]]
// CHECK: return %[[T0]] : vector<1xf32>

// -----

func.func @broadcast_vec1d_from_f32_scalable(%arg0: f32) -> vector<[2]xf32> {
%0 = vector.broadcast %arg0 : f32 to vector<[2]xf32>
return %0 : vector<[2]xf32>
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