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[mlir] Extract RHS rows once when lowering vector.contract to dot #130130

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Merged
merged 5 commits into from
Mar 12, 2025
Merged

[mlir] Extract RHS rows once when lowering vector.contract to dot #130130

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8e4544f
Extract RHS rows once when lowering vector.contract to dot
abulavin Mar 5, 2025
ce9c720
fixup: Refactor variable names in vector contract to dot transform test
abulavin Mar 6, 2025
4018f23
fixup: refer to columns instead of rows in reuse comment
abulavin Mar 6, 2025
4c74d73
fixup: Rephrase comment and rename column/row variables
abulavin Mar 11, 2025
86853bf
fixup: remove trailing whitespace
abulavin Mar 11, 2025
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25 changes: 17 additions & 8 deletions mlir/lib/Dialect/Vector/Transforms/LowerVectorContract.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -758,19 +758,28 @@ FailureOr<Value> ContractionOpToDotLowering::matchAndRewriteMaskableOp(
Value res = rewriter.create<arith::ConstantOp>(loc, dstType,
rewriter.getZeroAttr(dstType));
bool isInt = isa<IntegerType>(dstType.getElementType());
llvm::SmallVector<Value> extractedCols;
extractedCols.reserve(dstColumns);
for (unsigned r = 0; r < dstRows; ++r) {
Value a = rewriter.create<vector::ExtractOp>(op.getLoc(), lhs, r);
Value rowLhs = rewriter.create<vector::ExtractOp>(op.getLoc(), lhs, r);
for (unsigned c = 0; c < dstColumns; ++c) {
Value b = rank == 1
? rhs
: rewriter.create<vector::ExtractOp>(op.getLoc(), rhs, c);
Value m = createMul(op.getLoc(), a, b, isInt, rewriter);
Value reduced = rewriter.create<vector::ReductionOp>(
op.getLoc(), vector::CombiningKind::ADD, m);
// Extract each respective row and column of the LHS and RHS once to
// avoid having duplicate SSA values pointing to the same rows/columns.
if (r == 0) {
Value colRhs =
rank == 1 ? rhs
: rewriter.create<vector::ExtractOp>(op.getLoc(), rhs, c);
extractedCols.push_back(colRhs);
}
Value extractedColRhs = extractedCols[c];
Value product =
createMul(op.getLoc(), rowLhs, extractedColRhs, isInt, rewriter);
Value sum = rewriter.create<vector::ReductionOp>(
op.getLoc(), vector::CombiningKind::ADD, product);

SmallVector<int64_t, 2> pos = rank == 1 ? SmallVector<int64_t, 2>{r}
: SmallVector<int64_t, 2>{r, c};
res = rewriter.create<vector::InsertOp>(op.getLoc(), reduced, res, pos);
res = rewriter.create<vector::InsertOp>(op.getLoc(), sum, res, pos);
}
}
if (auto acc = op.getAcc())
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75 changes: 44 additions & 31 deletions mlir/test/Dialect/Vector/vector-contract-to-dot-transforms.mlir
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Original file line number Diff line number Diff line change
Expand Up @@ -151,43 +151,56 @@ func.func @extract_contract3(%arg0: vector<3xf32>,
iterator_types = ["parallel", "parallel", "reduction"]
}

// CHECK-LABEL: func @extract_contract4
// CHECK-SAME: %[[A:.*0]]: vector<2x2xf32>,
// CHECK-SAME: %[[B:.*1]]: vector<2x2xf32>,
// CHECK-SAME: %[[C:.*2]]: vector<2x2xf32>
// CHECK: %[[R:.*]] = arith.constant dense<0.000000e+00> : vector<2x2xf32>
// CHECK: %[[Bt:.*]] = vector.transpose %arg1, [1, 0] : vector<2x2xf32> to vector<2x2xf32>
// CHECK: %[[T0:.*]] = vector.extract %[[A]][0] : vector<2xf32> from vector<2x2xf32>
// CHECK: %[[T2:.*]] = vector.extract %[[Bt]][0] : vector<2xf32> from vector<2x2xf32>
// CHECK: %[[T9:.*]] = arith.mulf %[[T0]], %[[T2]] : vector<2xf32>
// CHECK: %[[T10:.*]] = vector.reduction <add>, %[[T9]] : vector<2xf32> into f32
// CHECK: %[[T11:.*]] = vector.insert %[[T10]], %[[R]] [0, 0] : f32 into vector<2x2xf32>
// CHECK-LABEL: func @contract_to_dot_matmat
// CHECK-SAME: %[[LHS:.*0]]: vector<2x2xf32>,
// CHECK-SAME: %[[RHS:.*1]]: vector<2x2xf32>,
// CHECK-SAME: %[[OUT:.*2]]: vector<2x2xf32>
//
// CHECK: %[[T12:.*]] = vector.extract %[[Bt]][1] : vector<2xf32> from vector<2x2xf32>
// CHECK: %[[T19:.*]] = arith.mulf %[[T0]], %[[T12]] : vector<2xf32>
// CHECK: %[[T20:.*]] = vector.reduction <add>, %[[T19]] : vector<2xf32> into f32
// CHECK: %[[T21:.*]] = vector.insert %[[T20]], %[[T11]] [0, 1] : f32 into vector<2x2xf32>
// The `vector.contract` to dot lowering will 'unroll' a matrix-matrix
// multiplication into individual dot products betweem rows of the LHS with columns
// of the RHS. In the following test we expect 4 extract-dotproduct-insert sequences of
// ops that correspond to the 4 dot products resulting from unrolling a matmul between
// two matrices of size (2, 2).
//
// CHECK: %[[T23:.*]] = vector.extract %[[A]][1] : vector<2xf32> from vector<2x2xf32>
// CHECK: %[[T24:.*]] = vector.extract %[[Bt]][0] : vector<2xf32> from vector<2x2xf32>
// CHECK: %[[T32:.*]] = arith.mulf %[[T23]], %[[T24]] : vector<2xf32>
// CHECK: %[[T33:.*]] = vector.reduction <add>, %[[T32]] : vector<2xf32> into f32
// CHECK: %[[T34:.*]] = vector.insert %[[T33]], %[[T21]] [1, 0] : f32 into vector<2x2xf32>
// CHECK: %[[INIT:.*]] = arith.constant dense<0.000000e+00> : vector<2x2xf32>
//
// CHECK: %[[T40:.*]] = vector.extract %[[Bt]][1] : vector<2xf32> from vector<2x2xf32>
// CHECK: %[[T41:.*]] = arith.mulf %[[T23]], %[[T40]] : vector<2xf32>
// CHECK: %[[T42:.*]] = vector.reduction <add>, %[[T41]] : vector<2xf32> into f32
// CHECK: %[[T43:.*]] = vector.insert %[[T42]], %[[T34]] [1, 1] : f32 into vector<2x2xf32>
// First, The RHS will be transposed to make it easier to extract individual columns
// using vector.extract.
//
// CHECK: %[[T52:.*]] = arith.addf %[[T43]], %[[C]] : vector<2x2xf32>
// CHECK: return %[[T52]] : vector<2x2xf32>
// CHECK: %[[RHS_T:.*]] = vector.transpose %[[RHS]], [1, 0] : vector<2x2xf32> to vector<2x2xf32>
//
// Next, we expect 4 sequences of extracting rows of the RHS, LHS, performing a dot
// product and then inserting it into the result.
//
// CHECK: %[[LHS0:.*]] = vector.extract %[[LHS]][0] : vector<2xf32> from vector<2x2xf32>
// CHECK: %[[RHS_T0:.*]] = vector.extract %[[RHS_T]][0] : vector<2xf32> from vector<2x2xf32>
// CHECK: %[[PROD0:.*]] = arith.mulf %[[LHS0]], %[[RHS_T0]] : vector<2xf32>
// CHECK: %[[SUM0:.*]] = vector.reduction <add>, %[[PROD0]] : vector<2xf32> into f32
// CHECK: %[[RES0:.*]] = vector.insert %[[SUM0]], %[[INIT]] [0, 0] : f32 into vector<2x2xf32>
//
// CHECK: %[[RHS_T1:.*]] = vector.extract %[[RHS_T]][1] : vector<2xf32> from vector<2x2xf32>
// CHECK: %[[PROD1:.*]] = arith.mulf %[[LHS0]], %[[RHS_T1]] : vector<2xf32>
// CHECK: %[[SUM1:.*]] = vector.reduction <add>, %[[PROD1]] : vector<2xf32> into f32
// CHECK: %[[RES1:.*]] = vector.insert %[[SUM1]], %[[RES0]] [0, 1] : f32 into vector<2x2xf32>
//
// CHECK: %[[LHS1:.*]] = vector.extract %[[LHS]][1] : vector<2xf32> from vector<2x2xf32>
// CHECK: %[[PROD2:.*]] = arith.mulf %[[LHS1]], %[[RHS_T0]] : vector<2xf32>
// CHECK: %[[SUM2:.*]] = vector.reduction <add>, %[[PROD2]] : vector<2xf32> into f32
// CHECK: %[[RES2:.*]] = vector.insert %[[SUM2]], %[[RES1]] [1, 0] : f32 into vector<2x2xf32>
//
// CHECK: %[[PROD3:.*]] = arith.mulf %[[LHS1]], %[[RHS_T1]] : vector<2xf32>
// CHECK: %[[SUM3:.*]] = vector.reduction <add>, %[[PROD3]] : vector<2xf32> into f32
// CHECK: %[[RES3:.*]] = vector.insert %[[SUM3]], %[[RES2]] [1, 1] : f32 into vector<2x2xf32>
//
// CHECK: %[[RES:.*]] = arith.addf %[[RES3]], %[[OUT]] : vector<2x2xf32>
// CHECK: return %[[RES]] : vector<2x2xf32>

func.func @extract_contract4(%arg0: vector<2x2xf32>,
%arg1: vector<2x2xf32>,
%arg2: vector<2x2xf32>) -> vector<2x2xf32> {
%0 = vector.contract #matmat_trait %arg0, %arg1, %arg2
func.func @contract_to_dot_matmat(%lhs: vector<2x2xf32>,
%rhs: vector<2x2xf32>,
%init: vector<2x2xf32>) -> vector<2x2xf32> {
%res = vector.contract #matmat_trait %lhs, %rhs, %init
: vector<2x2xf32>, vector<2x2xf32> into vector<2x2xf32>
return %0 : vector<2x2xf32>
return %res : vector<2x2xf32>
}


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