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[MLIR][Vector]: Generalize conversion of vector.insert to LLVM in line with vector.extract #128915

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merged 3 commits into from
Feb 26, 2025
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[MLIR][Vector]: Generalize conversion of vector.insert to LLVM in line with vector.extract #128915

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like-117731-but-for-insert
bjacob Feb 26, 2025
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bjacob Feb 26, 2025
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118 changes: 69 additions & 49 deletions mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -35,13 +35,6 @@
using namespace mlir;
using namespace mlir::vector;

// Helper to reduce vector type by *all* but one rank at back.
static VectorType reducedVectorTypeBack(VectorType tp) {
assert((tp.getRank() > 1) && "unlowerable vector type");
return VectorType::get(tp.getShape().take_back(), tp.getElementType(),
tp.getScalableDims().take_back());
}

// Helper that picks the proper sequence for inserting.
static Value insertOne(ConversionPatternRewriter &rewriter,
const LLVMTypeConverter &typeConverter, Location loc,
Expand Down Expand Up @@ -1223,7 +1216,6 @@ class VectorInsertOpConversion
matchAndRewrite(vector::InsertOp insertOp, OpAdaptor adaptor,
ConversionPatternRewriter &rewriter) const override {
auto loc = insertOp->getLoc();
auto sourceType = insertOp.getSourceType();
auto destVectorType = insertOp.getDestVectorType();
auto llvmResultType = typeConverter->convertType(destVectorType);
// Bail if result type cannot be lowered.
Expand All @@ -1233,53 +1225,81 @@ class VectorInsertOpConversion
SmallVector<OpFoldResult> positionVec = getMixedValues(
adaptor.getStaticPosition(), adaptor.getDynamicPosition(), rewriter);

// Overwrite entire vector with value. Should be handled by folder, but
// just to be safe.
ArrayRef<OpFoldResult> position(positionVec);
if (position.empty()) {
rewriter.replaceOp(insertOp, adaptor.getSource());
return success();
}

// One-shot insertion of a vector into an array (only requires insertvalue).
if (isa<VectorType>(sourceType)) {
if (insertOp.hasDynamicPosition())
return failure();

Value inserted = rewriter.create<LLVM::InsertValueOp>(
loc, adaptor.getDest(), adaptor.getSource(), getAsIntegers(position));
rewriter.replaceOp(insertOp, inserted);
return success();
// The logic in this pattern mirrors VectorExtractOpConversion. Refer to
// its explanatory comment about how N-D vectors are converted as nested
// aggregates (llvm.array's) of 1D vectors.
//
// The innermost dimension of the destination vector, when converted to a
// nested aggregate form, will always be a 1D vector.
//
// * If the insertion is happening into the innermost dimension of the
// destination vector:
// - If the destination is a nested aggregate, extract a 1D vector out of
// the aggregate. This can be done using llvm.extractvalue. The
// destination is now guaranteed to be a 1D vector, to which we are
// inserting.
// - Do the insertion into the 1D destination vector, and make the result
// the new source nested aggregate. This can be done using
// llvm.insertelement.
// * Insert the source nested aggregate into the destination nested
// aggregate.

// Determine if we need to extract/insert a 1D vector out of the aggregate.
bool isNestedAggregate = isa<LLVM::LLVMArrayType>(llvmResultType);
// Determine if we need to insert a scalar into the 1D vector.
bool insertIntoInnermostDim =
static_cast<int64_t>(positionVec.size()) == destVectorType.getRank();

ArrayRef<OpFoldResult> positionOf1DVectorWithinAggregate(
positionVec.begin(),
insertIntoInnermostDim ? positionVec.size() - 1 : positionVec.size());
OpFoldResult positionOfScalarWithin1DVector;
if (destVectorType.getRank() == 0) {
// Since the LLVM type converter converts 0D vectors to 1D vectors, we
// need to create a 0 here as the position into the 1D vector.
Type idxType = typeConverter->convertType(rewriter.getIndexType());
positionOfScalarWithin1DVector = rewriter.getZeroAttr(idxType);
} else if (insertIntoInnermostDim) {
positionOfScalarWithin1DVector = positionVec.back();
}

// Potential extraction of 1-D vector from array.
Value extracted = adaptor.getDest();
auto oneDVectorType = destVectorType;
if (position.size() > 1) {
if (insertOp.hasDynamicPosition())
return failure();

oneDVectorType = reducedVectorTypeBack(destVectorType);
extracted = rewriter.create<LLVM::ExtractValueOp>(
loc, extracted, getAsIntegers(position.drop_back()));
// We are going to mutate this 1D vector until it is either the final
// result (in the non-aggregate case) or the value that needs to be
// inserted into the aggregate result.
Value sourceAggregate = adaptor.getSource();
if (insertIntoInnermostDim) {
// Scalar-into-1D-vector case, so we know we will have to create a
// InsertElementOp. The question is into what destination.
if (isNestedAggregate) {
// Aggregate case: the destination for the InsertElementOp needs to be
// extracted from the aggregate.
if (!llvm::all_of(positionOf1DVectorWithinAggregate,
llvm::IsaPred<Attribute>)) {
// llvm.extractvalue does not support dynamic dimensions.
return failure();
}
sourceAggregate = rewriter.create<LLVM::ExtractValueOp>(
loc, adaptor.getDest(),
getAsIntegers(positionOf1DVectorWithinAggregate));
} else {
// No-aggregate case. The destination for the InsertElementOp is just
// the insertOp's destination.
sourceAggregate = adaptor.getDest();
}
// Insert the scalar into the 1D vector.
sourceAggregate = rewriter.create<LLVM::InsertElementOp>(
loc, sourceAggregate.getType(), sourceAggregate, adaptor.getSource(),
getAsLLVMValue(rewriter, loc, positionOfScalarWithin1DVector));
}

// Insertion of an element into a 1-D LLVM vector.
Value inserted = rewriter.create<LLVM::InsertElementOp>(
loc, typeConverter->convertType(oneDVectorType), extracted,
adaptor.getSource(), getAsLLVMValue(rewriter, loc, position.back()));

// Potential insertion of resulting 1-D vector into array.
if (position.size() > 1) {
if (insertOp.hasDynamicPosition())
return failure();

inserted = rewriter.create<LLVM::InsertValueOp>(
loc, adaptor.getDest(), inserted,
getAsIntegers(position.drop_back()));
Value result = sourceAggregate;
if (isNestedAggregate) {
result = rewriter.create<LLVM::InsertValueOp>(
loc, adaptor.getDest(), sourceAggregate,
getAsIntegers(positionOf1DVectorWithinAggregate));
}

rewriter.replaceOp(insertOp, inserted);
rewriter.replaceOp(insertOp, result);
return success();
}
};
Expand Down
38 changes: 32 additions & 6 deletions mlir/test/Conversion/VectorToLLVM/vector-to-llvm-interface.mlir
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Original file line number Diff line number Diff line change
Expand Up @@ -628,6 +628,16 @@ func.func @insertelement_into_vec_1d_f32_scalable_idx_as_index_scalable(%arg0: f
// vector.insert
//===----------------------------------------------------------------------===//

func.func @insert_scalar_into_vec_0d(%src: f32, %dst: vector<f32>) -> vector<f32> {
%0 = vector.insert %src, %dst[] : f32 into vector<f32>
return %0 : vector<f32>
}

// CHECK-LABEL: @insert_scalar_into_vec_0d
// CHECK: llvm.insertelement {{.*}} : vector<1xf32>

// -----

func.func @insert_scalar_into_vec_1d_f32(%arg0: f32, %arg1: vector<4xf32>) -> vector<4xf32> {
%0 = vector.insert %arg0, %arg1[3] : f32 into vector<4xf32>
return %0 : vector<4xf32>
Expand Down Expand Up @@ -780,10 +790,10 @@ func.func @insert_scalar_into_vec_2d_f32_dynamic_idx(%arg0: vector<1x16xf32>, %a
return %0 : vector<1x16xf32>
}

// Multi-dim vectors are not supported but this test shouldn't crash.

// CHECK-LABEL: @insert_scalar_into_vec_2d_f32_dynamic_idx(
// CHECK: vector.insert
// CHECK: llvm.extractvalue {{.*}} : !llvm.array<1 x vector<16xf32>>
// CHECK: llvm.insertelement {{.*}} : vector<16xf32>
// CHECK: llvm.insertvalue {{.*}} : !llvm.array<1 x vector<16xf32>>

// -----

Expand All @@ -793,10 +803,26 @@ func.func @insert_scalar_into_vec_2d_f32_dynamic_idx_scalable(%arg0: vector<1x[1
return %0 : vector<1x[16]xf32>
}

// Multi-dim vectors are not supported but this test shouldn't crash.

// CHECK-LABEL: @insert_scalar_into_vec_2d_f32_dynamic_idx_scalable(
// CHECK: vector.insert
// CHECK: llvm.extractvalue {{.*}} : !llvm.array<1 x vector<[16]xf32>>
// CHECK: llvm.insertelement {{.*}} : vector<[16]xf32>
// CHECK: llvm.insertvalue {{.*}} : !llvm.array<1 x vector<[16]xf32>>
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Can we have a negative test for when dynamic indices fail?

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Added.



// -----

func.func @insert_scalar_into_vec_2d_f32_dynamic_idx_fail(%arg0: vector<2x16xf32>, %arg1: f32, %idx: index)
-> vector<2x16xf32> {
%0 = vector.insert %arg1, %arg0[%idx, 0]: f32 into vector<2x16xf32>
return %0 : vector<2x16xf32>
}

// Currently fails to convert because of the dynamic index in non-innermost
// dimension that converts to a llvm.array, as llvm.extractvalue does not
// support dynamic dimensions

// CHECK-LABEL: @insert_scalar_into_vec_2d_f32_dynamic_idx_fail
// CHECK: vector.insert

// -----

Expand Down