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[LinalgExt] Fix gather->extract_slice to invert the dimension_map #24871

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[LinalgExt] Fix gather->extract_slice to invert the dimension_map #24871

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8 changes: 7 additions & 1 deletion compiler/src/iree/compiler/Dialect/LinalgExt/IR/LinalgExtOps.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -574,7 +574,13 @@ struct ConvertGatherToExtract : OpRewritePattern<IREE::LinalgExt::GatherOp> {
.getResult();
}

applyPermutationToVector(offsets, gatherOp.getDimensionMap());
// `dimension_map` maps each index component `i` to the source dimension it
// indexes: generateScalarImplementation sets `starts[dimensionMap[i]] =
// indexValue[i]`. Building the source offsets from the (in-order) index
// values is therefore the *inverse* permutation; applying `dimension_map`
// directly only happens to be correct when it is an involution.
applyPermutationToVector(
offsets, invertPermutationVector(gatherOp.getDimensionMap()));
int64_t sourceRank = gatherOp.getSourceType().getRank();
offsets.resize(sourceRank, rewriter.getIndexAttr(0));

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31 changes: 31 additions & 0 deletions compiler/src/iree/compiler/Dialect/LinalgExt/IR/test/canonicalize.mlir
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Expand Up @@ -79,6 +79,37 @@ func.func @gather_to_extract_slice_perm(%source : tensor<10x1024x128xi32>, %indi

// -----

// Non-involutive dimension_map: index component `i` sets the source offset at
// dimension `dimension_map[i]` (see GatherOp::generateScalarImplementation), so
// the extract_slice offsets are the *inverse* permutation of the loaded index
// values. For dimension_map = [1, 2, 0] the offsets in source-dim order are
// [idx2, idx0, idx1]; applying the map directly would (wrongly) give
// [idx1, idx2, idx0].
func.func @gather_to_extract_slice_perm3(%source : tensor<10x20x30x128xi32>, %indices : tensor<1x1x1x3xi32>) -> (tensor<1x1x1x128xi32>) {
%empty = tensor.empty() : tensor<1x1x1x128xi32>
%result = iree_linalg_ext.gather dimension_map = [1, 2, 0]
ins(%source, %indices : tensor<10x20x30x128xi32>, tensor<1x1x1x3xi32>)
outs(%empty: tensor<1x1x1x128xi32>) -> tensor<1x1x1x128xi32>
return %result : tensor<1x1x1x128xi32>
}
// CHECK-LABEL: @gather_to_extract_slice_perm3
// CHECK-SAME: %[[ARG0:[a-zA-Z0-9]+]]
// CHECK-SAME: %[[ARG1:[a-zA-Z0-9]+]]
// CHECK-DAG: %[[C0:.+]] = arith.constant 0 : index
// CHECK-DAG: %[[C1:.+]] = arith.constant 1 : index
// CHECK-DAG: %[[C2:.+]] = arith.constant 2 : index
// CHECK-DAG: %[[IDX0:.+]] = tensor.extract %[[ARG1]][%[[C0]], %[[C0]], %[[C0]], %[[C0]]]
// CHECK-DAG: %[[IDX1:.+]] = tensor.extract %[[ARG1]][%[[C0]], %[[C0]], %[[C0]], %[[C1]]]
// CHECK-DAG: %[[IDX2:.+]] = tensor.extract %[[ARG1]][%[[C0]], %[[C0]], %[[C0]], %[[C2]]]
// CHECK-DAG: %[[CAST0:.+]] = arith.index_cast %[[IDX0]]
// CHECK-DAG: %[[CAST1:.+]] = arith.index_cast %[[IDX1]]
// CHECK-DAG: %[[CAST2:.+]] = arith.index_cast %[[IDX2]]
// CHECK: %[[SLICE:.+]] = tensor.extract_slice %[[ARG0]]
// CHECK-SAME: [%[[CAST2]], %[[CAST0]], %[[CAST1]], 0] [1, 1, 1, 128] [1, 1, 1, 1]
// CHECK-SAME: tensor<10x20x30x128xi32> to tensor<1x1x1x128xi32>

// -----

func.func @gather_to_extract_slice_full_collapse(%source : tensor<2x2x1xi32>, %indices : tensor<2xi32>) -> (tensor<1xi32>) {
%empty = tensor.empty() : tensor<1xi32>
%result = iree_linalg_ext.gather dimension_map = [0, 1]
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