[mlir][vector] Add new lowering mode to vector.contractionOp

Add lowering for cases where the reduction dimension is fully unrolled.
It is common to unroll the reduction dimension, therefore we would want
to lower the contractions to an elementwise vector op in this case.

Differential Revision: https://reviews.llvm.org/D126120

1 files changed, 174 insertions, 41 deletions

diff --git a/mlir/lib/Dialect/Vector/Transforms/VectorTransforms.cpp b/mlir/lib/Dialect/Vector/Transforms/VectorTransforms.cpp
index f84fc2da08f2..e1f4cffb9355 100644
--- a/mlir/lib/Dialect/Vector/Transforms/VectorTransforms.cpp
+++ b/mlir/lib/Dialect/Vector/Transforms/VectorTransforms.cpp
@@ -144,6 +144,59 @@ static SmallVector<IntType, 4> extractVector(ArrayAttr arrayAttr) {
       [](IntegerAttr attr) { return static_cast<IntType>(attr.getInt()); }));
 }
 
+/// Helper to create arithmetic operation associated with a kind of contraction.
+static Optional<Value> createContractArithOp(Location loc, Value x, Value y,
+                                             Value acc,
+                                             vector::CombiningKind kind,
+                                             PatternRewriter &rewriter,
+                                             bool isInt) {
+  using vector::CombiningKind;
+  Value mul;
+  if (isInt) {
+    if (kind == CombiningKind::MINF || kind == CombiningKind::MAXF)
+      // Only valid for floating point types.
+      return Optional<Value>();
+    mul = rewriter.create<arith::MulIOp>(loc, x, y);
+  } else {
+    // Float case.
+    if (kind == CombiningKind::AND || kind == CombiningKind::MINUI ||
+        kind == CombiningKind::MINSI || kind == CombiningKind::MAXUI ||
+        kind == CombiningKind::MAXSI || kind == CombiningKind::OR ||
+        kind == CombiningKind::XOR)
+      // Only valid for integer types.
+      return Optional<Value>();
+    // Special case for fused multiply-add.
+    if (acc && acc.getType().isa<VectorType>() && kind == CombiningKind::ADD) {
+      return Optional<Value>(rewriter.create<vector::FMAOp>(loc, x, y, acc));
+    }
+    mul = rewriter.create<arith::MulFOp>(loc, x, y);
+  }
+  if (!acc)
+    return Optional<Value>(mul);
+  return makeArithReduction(rewriter, loc, kind, mul, acc);
+}
+
+/// Return the positions of the reductions in the given map.
+static SmallVector<int64_t> getReductionIndex(AffineMap map,
+                                              ArrayAttr iteratorTypes) {
+  SmallVector<int64_t> dimsIdx;
+  for (unsigned i = 0, e = map.getNumResults(); i < e; i++) {
+    if (isReductionIterator(iteratorTypes[map.getDimPosition(i)]))
+      dimsIdx.push_back(i);
+  }
+  return dimsIdx;
+}
+
+/// Look for a given dimension in an affine map and return its position. Return
+/// llvm::None if the dimension is not in the map results.
+static llvm::Optional<unsigned> getDimPosition(AffineMap map, unsigned dim) {
+  for (unsigned i = 0, e = map.getNumResults(); i < e; i++) {
+    if (map.getDimPosition(i) == dim)
+      return i;
+  }
+  return llvm::None;
+}
+
 namespace {
 
 /// ShapeCastOpFolder folds cancelling ShapeCastOps away.
@@ -498,9 +551,8 @@ public:
     if (!rhsType) {
       // Special case: AXPY operation.
       Value b = rewriter.create<vector::BroadcastOp>(loc, lhsType, op.getRhs());
-      Optional<Value> mult =
-          isInt ? genMultI(loc, op.getLhs(), b, acc, kind, rewriter)
-                : genMultF(loc, op.getLhs(), b, acc, kind, rewriter);
+      Optional<Value> mult = createContractArithOp(loc, op.getLhs(), b, acc,
+                                                   kind, rewriter, isInt);
       if (!mult.hasValue())
         return failure();
       rewriter.replaceOp(op, mult.getValue());
@@ -518,8 +570,7 @@ public:
       if (acc)
         r = rewriter.create<vector::ExtractOp>(loc, rhsType, acc, pos);
       Optional<Value> m =
-          isInt ? genMultI(loc, a, op.getRhs(), r, kind, rewriter)
-                : genMultF(loc, a, op.getRhs(), r, kind, rewriter);
+          createContractArithOp(loc, a, op.getRhs(), r, kind, rewriter, isInt);
       if (!m.hasValue())
         return failure();
       result = rewriter.create<vector::InsertOp>(loc, resType, m.getValue(),
@@ -528,48 +579,127 @@ public:
     rewriter.replaceOp(op, result);
     return success();
   }
+};
 
-private:
-  static Optional<Value> genMultI(Location loc, Value x, Value y, Value acc,
-                                  vector::CombiningKind kind,
-                                  PatternRewriter &rewriter) {
-    using vector::CombiningKind;
-
-    auto mul = rewriter.create<arith::MulIOp>(loc, x, y);
-    if (!acc)
-      return Optional<Value>(mul);
-
-    if (kind == CombiningKind::MINF || kind == CombiningKind::MAXF)
-      // Only valid for floating point types.
-      return Optional<Value>();
-
-    return makeArithReduction(rewriter, loc, kind, mul, acc);
+/// Lower vector.contract with all size one reduction dimensions to
+/// elementwise ops when possible.
+struct ContractOpToElementwise
+    : public OpRewritePattern<vector::ContractionOp> {
+  using OpRewritePattern::OpRewritePattern;
+  using FilterConstraintType =
+      std::function<LogicalResult(vector::ContractionOp op)>;
+  static LogicalResult defaultFilter(vector::ContractionOp op) {
+    return success();
   }
+  ContractOpToElementwise(
+      vector::VectorTransformsOptions vectorTransformOptions,
+      MLIRContext *context,
+      const FilterConstraintType &constraint = defaultFilter)
+      : OpRewritePattern<vector::ContractionOp>(context),
+        vectorTransformOptions(vectorTransformOptions), filter(defaultFilter) {}
 
-  static Optional<Value> genMultF(Location loc, Value x, Value y, Value acc,
-                                  vector::CombiningKind kind,
-                                  PatternRewriter &rewriter) {
-    using vector::CombiningKind;
-
-    // Special case for fused multiply-add.
-    if (acc && kind == CombiningKind::ADD) {
-      return Optional<Value>(rewriter.create<vector::FMAOp>(loc, x, y, acc));
-    }
-
-    auto mul = rewriter.create<arith::MulFOp>(loc, x, y);
-
-    if (!acc)
-      return Optional<Value>(mul);
+  LogicalResult matchAndRewrite(vector::ContractionOp contractOp,
+                                PatternRewriter &rewriter) const override {
+    // TODO: implement masks
+    if (llvm::size(contractOp.getMasks()) != 0)
+      return failure();
 
-    if (kind == CombiningKind::ADD || kind == CombiningKind::AND ||
-        kind == CombiningKind::MINUI || kind == CombiningKind::MINSI ||
-        kind == CombiningKind::MAXUI || kind == CombiningKind::MAXSI ||
-        kind == CombiningKind::OR || kind == CombiningKind::XOR)
-      // Already handled or only valid for integer types.
-      return Optional<Value>();
+    if (failed(filter(contractOp)))
+      return failure();
 
-    return makeArithReduction(rewriter, loc, kind, mul, acc);
+    if (vectorTransformOptions.vectorContractLowering !=
+        vector::VectorContractLowering::ParallelArith)
+      return failure();
+    ArrayRef<int64_t> lhsShape = contractOp.getLhsType().getShape();
+    ArrayRef<int64_t> rhsShape = contractOp.getRhsType().getShape();
+    AffineMap lhsMap = contractOp.getIndexingMaps()[0];
+    AffineMap rhsMap = contractOp.getIndexingMaps()[1];
+    SmallVector<int64_t> lhsReductionDims =
+        getReductionIndex(lhsMap, contractOp.getIteratorTypes());
+    SmallVector<int64_t> rhsReductionDims =
+        getReductionIndex(rhsMap, contractOp.getIteratorTypes());
+    // All the reduction dimensions must be a size 1.
+    for (int64_t dim : lhsReductionDims) {
+      if (lhsShape[dim] != 1)
+        return failure();
+    }
+    for (int64_t dim : rhsReductionDims) {
+      if (rhsShape[dim] != 1)
+        return failure();
+    }
+    AffineMap accMap = contractOp.getIndexingMaps()[2];
+    unsigned numParallelDims = accMap.getNumResults();
+    unsigned numLhsDimToBroadcast =
+        numParallelDims - (lhsMap.getNumResults() - lhsReductionDims.size());
+    unsigned numRhsDimToBroadcast =
+        numParallelDims - (rhsMap.getNumResults() - rhsReductionDims.size());
+    SmallVector<int64_t> lhsDims;
+    SmallVector<int64_t> lhsTranspose;
+    SmallVector<int64_t> rhsDims;
+    SmallVector<int64_t> rhsTranspose;
+    for (int64_t dim : lhsReductionDims)
+      lhsTranspose.push_back(numLhsDimToBroadcast + dim);
+    for (int64_t dim : rhsReductionDims)
+      rhsTranspose.push_back(numRhsDimToBroadcast + dim);
+    // Loop through the parallel dimensions to calculate the dimensions to
+    // broadcast and to permute in order to extract only parallel dimensions.
+    for (unsigned i = 0; i < numParallelDims; i++) {
+      llvm::Optional<unsigned> lhsDim =
+          getDimPosition(lhsMap, accMap.getDimPosition(i));
+      if (lhsDim) {
+        lhsTranspose.push_back(numLhsDimToBroadcast + *lhsDim);
+      } else {
+        // If the parallel dimension doesn't exist we will have to broadcast it.
+        lhsDims.push_back(
+            contractOp.getResultType().cast<VectorType>().getDimSize(i));
+        lhsTranspose.push_back(lhsDims.size() - 1);
+      }
+      llvm::Optional<unsigned> rhsDim =
+          getDimPosition(rhsMap, accMap.getDimPosition(i));
+      if (rhsDim) {
+        rhsTranspose.push_back(numRhsDimToBroadcast + *rhsDim);
+      } else {
+        // If the parallel dimension doesn't exist we will have to broadcast it.
+        rhsDims.push_back(
+            contractOp.getResultType().cast<VectorType>().getDimSize(i));
+        rhsTranspose.push_back(rhsDims.size() - 1);
+      }
+    }
+    Value newLhs = contractOp.getLhs();
+    Value newRhs = contractOp.getRhs();
+    Location loc = contractOp.getLoc();
+    if (!lhsDims.empty()) {
+      lhsDims.append(lhsShape.begin(), lhsShape.end());
+      auto expandedType =
+          VectorType::get(lhsDims, contractOp.getLhsType().getElementType());
+      newLhs = rewriter.create<vector::BroadcastOp>(loc, expandedType, newLhs);
+    }
+    if (!rhsDims.empty()) {
+      rhsDims.append(rhsShape.begin(), rhsShape.end());
+      auto expandedType =
+          VectorType::get(rhsDims, contractOp.getRhsType().getElementType());
+      newRhs = rewriter.create<vector::BroadcastOp>(loc, expandedType, newRhs);
+    }
+    bool isInt = contractOp.getLhsType().getElementType().isIntOrIndex();
+    newLhs = rewriter.create<vector::TransposeOp>(loc, newLhs, lhsTranspose);
+    newRhs = rewriter.create<vector::TransposeOp>(loc, newRhs, rhsTranspose);
+    SmallVector<int64_t, 4> lhsOffsets(lhsReductionDims.size(), 0);
+    SmallVector<int64_t, 4> rhsOffsets(rhsReductionDims.size(), 0);
+    newLhs = rewriter.create<vector::ExtractOp>(
+        loc, newLhs, rewriter.getI64ArrayAttr(lhsOffsets));
+    newRhs = rewriter.create<vector::ExtractOp>(
+        loc, newRhs, rewriter.getI64ArrayAttr(rhsOffsets));
+    Optional<Value> result =
+        createContractArithOp(loc, newLhs, newRhs, contractOp.getAcc(),
+                              contractOp.getKind(), rewriter, isInt);
+    rewriter.replaceOp(contractOp, {*result});
+    return success();
   }
+
+private:
+  /// Options to control the vector patterns.
+  vector::VectorTransformsOptions vectorTransformOptions;
+  FilterConstraintType filter;
 };
 
 /// Progressive lowering of ConstantMaskOp.
@@ -1594,6 +1724,9 @@ ContractionOpLowering::matchAndRewrite(vector::ContractionOp op,
   ContractionOpToDotLowering pat3(vectorTransformOptions, ctx);
   if (succeeded(pat3.matchAndRewrite(op, rewriter)))
     return success();
+  ContractOpToElementwise pat4(vectorTransformOptions, ctx);
+  if (succeeded(pat4.matchAndRewrite(op, rewriter)))
+    return success();
 
   // Find first batch dimension in LHS/RHS, and lower when found.
   std::vector<std::pair<int64_t, int64_t>> batchDimMap = op.getBatchDimMap();