[mlir][mesh] Refactoring code organization, tests and docs

* Split out `MeshDialect.h` form `MeshOps.h` that defines the dialect class.
Reduces include clutter if you care only about the dialect and not the ops.

* Expose functions `getMesh` and `collectiveProcessGroupSize`.
There functions are useful for outside users of the dialect.

* Remove unused code.

* Remove examples and tests of mesh.shard attribute in tensor encoding.
Per the decision that Spmdization would be performed on sharding annotations
and there will be no tensors with sharding specified in the type.
For more info see this RFC comment:
https://discourse.llvm.org/t/rfc-sharding-framework-design-for-device-mesh/73533/81

Author: sogartar

mlir/include/mlir/Dialect/Mesh/IR/CMakeLists.txt

@@ -2,11 +2,11 @@ add_mlir_dialect(MeshOps mesh)
 add_mlir_doc(MeshOps MeshOps Dialects/ -gen-dialect-doc -dialect=mesh)
 
 set(LLVM_TARGET_DEFINITIONS MeshBase.td)
-mlir_tablegen(MeshOpsAttributes.h.inc -gen-attrdef-decls)
-mlir_tablegen(MeshOpsAttributes.cpp.inc -gen-attrdef-defs)
-add_public_tablegen_target(MLIRMeshOpsAttrIncGen)
+mlir_tablegen(MeshAttributes.h.inc -gen-attrdef-decls)
+mlir_tablegen(MeshAttributes.cpp.inc -gen-attrdef-defs)
+add_public_tablegen_target(MLIRMeshAttrIncGen)
 
 set(LLVM_TARGET_DEFINITIONS MeshBase.td)
-mlir_tablegen(MeshOpsEnums.h.inc -gen-enum-decls)
-mlir_tablegen(MeshOpsEnums.cpp.inc -gen-enum-defs)
-add_public_tablegen_target(MLIRMeshOpsEnumsIncGen)
+mlir_tablegen(MeshEnums.h.inc -gen-enum-decls)
+mlir_tablegen(MeshEnums.cpp.inc -gen-enum-defs)
+add_public_tablegen_target(MLIRMeshEnumsIncGen)

mlir/include/mlir/Dialect/Mesh/IR/MeshBase.td

@@ -123,18 +123,18 @@ def MeshSharding : AttrDef<Mesh_Dialect, "MeshSharding"> {
     // The tensor is fully replicated on @mesh0.
     // Currently, there must be at least one sub-array present in axes, even
     // if it's empty. Otherwise, a parsing error will occur.
-    tensor<4x8xf32, #mesh.shard<@mesh0, [[]]>>
+    #mesh.shard<@mesh0, [[]]>
 
     // The tensor is sharded on the first dimension along axis 0 of @mesh0
-    tensor<4x8xf32, #mesh.shard<@mesh0, [[0]]>
+    #mesh.shard<@mesh0, [[0]]>
 
     // The tensor is sharded on the first dimension along axis 0 of @mesh0 and
     // it is also a partial_sum along mesh axis 1.
-    tensor<4x8xf32, #mesh.shard<@mesh0, [[0], []], partial = sum[1]>
+    #mesh.shard<@mesh0, [[0], []], partial = sum[1]>
 
     // The tensor is sharded on the first dimension along axis 0 of @mesh0 and
     // it is also a partial_max along mesh axis 1.
-    tensor<4x8xf32, #mesh.shard<@mesh0, [[0]], partial = max[1]>
+    #mesh.shard<@mesh0, [[0]], partial = max[1]>
 
     // Could be used in the attribute of mesh.shard op
     %0 = mesh.shard %arg0 to <@mesh0, [[0]]> : tensor<4x8xf32>

mlir/include/mlir/Dialect/Mesh/IR/MeshDialect.h

@@ -0,0 +1,16 @@
+//===- MeshOps.h - Mesh Dialect ---------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_DIALECT_MESH_IR_MESHDIALECT_H
+#define MLIR_DIALECT_MESH_IR_MESHDIALECT_H
+
+#include "mlir/IR/Dialect.h"
+
+#include "mlir/Dialect/Mesh/IR/MeshOpsDialect.h.inc"
+
+#endif // MLIR_DIALECT_MESH_IR_MESHDIALECT_H

mlir/include/mlir/Dialect/Mesh/IR/MeshOps.h

@@ -15,7 +15,6 @@
 #include "mlir/IR/SymbolTable.h"
 #include "mlir/Interfaces/InferTypeOpInterface.h"
 #include "mlir/Interfaces/SideEffectInterfaces.h"
-#include <algorithm>
 
 namespace mlir {
 namespace mesh {
@@ -26,12 +25,10 @@ using MeshAxesAttr = DenseI16ArrayAttr;
 } // namespace mesh
 } // namespace mlir
 
-#include "mlir/Dialect/Mesh/IR/MeshOpsDialect.h.inc"
-
-#include "mlir/Dialect/Mesh/IR/MeshOpsEnums.h.inc"
+#include "mlir/Dialect/Mesh/IR/MeshEnums.h.inc"
 
 #define GET_ATTRDEF_CLASSES
-#include "mlir/Dialect/Mesh/IR/MeshOpsAttributes.h.inc"
+#include "mlir/Dialect/Mesh/IR/MeshAttributes.h.inc"
 
 #define GET_OP_CLASSES
 #include "mlir/Dialect/Mesh/IR/MeshOps.h.inc"
@@ -51,6 +48,36 @@ void removeTrailingEmptySubArray(SmallVector<SmallVector<T>> &array) {
 
 Partial getPartialTypeFromReduction(IteratorType iType);
 
+inline mesh::MeshOp getMesh(Operation *op, FlatSymbolRefAttr meshSymbol,
+                            SymbolTableCollection &symbolTableCollection) {
+  return symbolTableCollection.lookupNearestSymbolFrom<mesh::MeshOp>(
+      op, meshSymbol);
+}
+
+// Get the corresponding mesh op using the standard attribute nomenclature.
+template <typename Op>
+mesh::MeshOp getMesh(Op op, SymbolTableCollection &symbolTableCollection) {
+  return getMesh(op.getOperation(), op.getMeshAttr(), symbolTableCollection);
+}
+
+// Get the number of processes that participate in each group
+// induced by `meshAxes`.
+template <typename MeshAxesRange, typename MeshShapeRange>
+int64_t collectiveProcessGroupSize(MeshAxesRange &&meshAxes,
+                                   MeshShapeRange &&meshShape) {
+  int64_t res = 1;
+
+  for (MeshAxis axis : meshAxes) {
+    auto axisSize = *(std::begin(meshShape) + axis);
+    if (ShapedType::isDynamic(axisSize)) {
+      return ShapedType::kDynamic;
+    }
+    res *= axisSize;
+  }
+
+  return res;
+}
+
 } // namespace mesh
 } // namespace mlir
 

mlir/include/mlir/Dialect/Mesh/IR/MeshOps.td

@@ -61,10 +61,6 @@ def Mesh_MeshOp : Mesh_Op<"mesh", [Symbol]> {
     // A device mesh with 2 axes, the number of devices along both axes
     // is unknown
     mesh.mesh @mesh3(shape = ?x?)
-
-    // Used in the mesh sharding attribute to extend the standard tensor to
-    // distributed
-    tensor<4x8xf32, #mesh.shard<@mesh0, [[0]]>>
     ```
   }];
   let arguments = (ins

mlir/include/mlir/InitAllDialects.h

@@ -54,7 +54,7 @@
 #include "mlir/Dialect/MemRef/IR/ValueBoundsOpInterfaceImpl.h"
 #include "mlir/Dialect/MemRef/Transforms/AllocationOpInterfaceImpl.h"
 #include "mlir/Dialect/MemRef/Transforms/RuntimeOpVerification.h"
-#include "mlir/Dialect/Mesh/IR/MeshOps.h"
+#include "mlir/Dialect/Mesh/IR/MeshDialect.h"
 #include "mlir/Dialect/NVGPU/IR/NVGPUDialect.h"
 #include "mlir/Dialect/OpenACC/OpenACC.h"
 #include "mlir/Dialect/OpenMP/OpenMPDialect.h"

mlir/lib/Dialect/Mesh/IR/CMakeLists.txt

@@ -5,8 +5,8 @@ add_mlir_dialect_library(MLIRMeshDialect
   ${MLIR_MAIN_INCLUDE_DIR}/mlir/Dialect/Mesh
 
   DEPENDS
-  MLIRMeshOpsAttrIncGen
-  MLIRMeshOpsEnumsIncGen
+  MLIRMeshAttrIncGen
+  MLIRMeshEnumsIncGen
   MLIRMeshOpsIncGen
 
   LINK_LIBS PUBLIC

mlir/lib/Dialect/Mesh/IR/MeshOps.cpp

@@ -7,6 +7,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "mlir/Dialect/Mesh/IR/MeshOps.h"
+#include "mlir/Dialect/Mesh/IR/MeshDialect.h"
+
 #include "mlir/Dialect/Arith/IR/Arith.h"
 #include "mlir/Dialect/Utils/StaticValueUtils.h"
 #include "mlir/IR/Attributes.h"
@@ -43,24 +45,6 @@ using namespace mlir::mesh;
 
 #include "mlir/Dialect/Mesh/IR/MeshOpsDialect.cpp.inc"
 
-template <typename It>
-static It canonicalizeSetAsArray(It begin, It end) {
-  llvm::sort(begin, end);
-  return std::unique(begin, end);
-}
-
-template <typename R>
-static auto canonicalizeSetAsArray(R &&range) {
-  return canonicalizeSetAsArray(adl_begin(range), adl_end(range));
-}
-
-template <typename T>
-static SmallVector<T> &canonicalizeSetAsVector(SmallVector<T> &vec) {
-  auto newEnd = canonicalizeSetAsArray(vec);
-  vec.resize(newEnd - vec.begin());
-  return vec;
-}
-
 namespace {
 
 struct DimensionSize {
@@ -114,10 +98,10 @@ Operation *MeshDialect::materializeConstant(OpBuilder &builder, Attribute value,
 // Mesh utilities
 //===----------------------------------------------------------------------===//
 
-static FailureOr<MeshOp> getMesh(Operation *op, FlatSymbolRefAttr meshSymbol,
-                                 SymbolTableCollection &symbolTable) {
-  mesh::MeshOp mesh =
-      symbolTable.lookupNearestSymbolFrom<mesh::MeshOp>(op, meshSymbol);
+static FailureOr<MeshOp> getMeshAndVerify(Operation *op,
+                                          FlatSymbolRefAttr meshSymbol,
+                                          SymbolTableCollection &symbolTable) {
+  mesh::MeshOp mesh = getMesh(op, meshSymbol, symbolTable);
   if (!mesh) {
     return op->emitError() << "Undefined required mesh symbol \""
                            << meshSymbol.getValue() << "\".";
@@ -201,10 +185,6 @@ LogicalResult MeshOp::verify() {
   if (rank <= 0)
     return emitOpError("rank of mesh is expected to be a positive integer");
 
-  if (getShape().size() > size_t(rank))
-    return emitOpError(
-        "rank of shape is not expected to be larger than rank of mesh");
-
   for (int64_t dimSize : getShape()) {
     if (dimSize < 0 && !ShapedType::isDynamic(dimSize))
       return emitOpError("dimension size of a mesh is expected to be "
@@ -220,7 +200,7 @@ LogicalResult MeshOp::verify() {
 
 LogicalResult
 MeshShapeOp::verifySymbolUses(SymbolTableCollection &symbolTable) {
-  auto mesh = ::getMesh(getOperation(), getMeshAttr(), symbolTable);
+  auto mesh = ::getMeshAndVerify(getOperation(), getMeshAttr(), symbolTable);
   if (failed(mesh)) {
     return failure();
   }
@@ -322,7 +302,7 @@ bool MeshShardingAttr::operator==(MeshShardingAttr rhs) const {
 
 LogicalResult
 ProcessMultiIndexOp::verifySymbolUses(SymbolTableCollection &symbolTable) {
-  auto mesh = ::getMesh(getOperation(), getMeshAttr(), symbolTable);
+  auto mesh = ::getMeshAndVerify(getOperation(), getMeshAttr(), symbolTable);
   if (failed(mesh)) {
     return failure();
   }
@@ -360,7 +340,7 @@ void ProcessMultiIndexOp::build(OpBuilder &odsBuilder, OperationState &odsState,
 
 LogicalResult
 ProcessLinearIndexOp::verifySymbolUses(SymbolTableCollection &symbolTable) {
-  auto mesh = ::getMesh(getOperation(), getMeshAttr(), symbolTable);
+  auto mesh = ::getMeshAndVerify(getOperation(), getMeshAttr(), symbolTable);
   if (failed(mesh)) {
     return failure();
   }
@@ -428,7 +408,8 @@ static LogicalResult verifyInGroupDevice(Location loc, StringRef deviceName,
 template <typename Op>
 static FailureOr<MeshOp>
 getMeshAndVerifyAxes(Op op, SymbolTableCollection &symbolTable) {
-  auto mesh = ::getMesh(op.getOperation(), op.getMeshAttr(), symbolTable);
+  auto mesh =
+      ::getMeshAndVerify(op.getOperation(), op.getMeshAttr(), symbolTable);
   if (failed(mesh)) {
     return failure();
   }
@@ -450,21 +431,6 @@ static auto product(R &&range) {
   return product(adl_begin(range), adl_end(range));
 }
 
-static int64_t collectiveDeviceGroupSize(ArrayRef<MeshAxis> meshAxes,
-                                         ArrayRef<int64_t> meshShape) {
-  int64_t res = 1;
-
-  for (MeshAxis axis : meshAxes) {
-    if (ShapedType::isDynamic(meshShape[axis])) {
-      return ShapedType::kDynamic;
-    }
-    assert(size_t(axis) < meshShape.size());
-    res *= meshShape[axis];
-  }
-
-  return res;
-}
-
 static LogicalResult verifyDimensionCompatibility(Location loc,
                                                   int64_t expectedDimSize,
                                                   int64_t resultDimSize,
@@ -495,7 +461,7 @@ static LogicalResult verifyGatherOperandAndResultShape(
   ShapedType operandType = operand.getType().cast<ShapedType>();
   ShapedType resultType = result.getType().cast<ShapedType>();
   auto deviceGroupSize =
-      DimensionSize(collectiveDeviceGroupSize(meshAxes, meshShape));
+      DimensionSize(collectiveProcessGroupSize(meshAxes, meshShape));
   for (int64_t axis = 0; axis < operandType.getRank(); ++axis) {
     auto operandDimSize = DimensionSize(operandType.getDimSize(axis));
     auto resultDimSize = DimensionSize(resultType.getDimSize(axis));
@@ -529,7 +495,7 @@ static LogicalResult verifyAllToAllOperandAndResultShape(
   }
 
   auto deviceGroupSize =
-      DimensionSize(collectiveDeviceGroupSize(meshAxes, meshShape));
+      DimensionSize(collectiveProcessGroupSize(meshAxes, meshShape));
   auto operandConcatDimSize = DimensionSize(operandType.getDimSize(concatAxis));
   auto operandSplitDimSize = DimensionSize(operandType.getDimSize(splitAxis));
   DimensionSize expectedResultConcatDimSize =
@@ -570,7 +536,7 @@ static LogicalResult verifyScatterOperandAndResultShape(
   }
 
   auto deviceGroupSize =
-      DimensionSize(collectiveDeviceGroupSize(meshAxes, meshShape));
+      DimensionSize(collectiveProcessGroupSize(meshAxes, meshShape));
   auto operandScatterDimSize =
       DimensionSize(operandType.getDimSize(scatterAxis));
   if (!operandScatterDimSize.isDynamic() && !deviceGroupSize.isDynamic() &&

mlir/lib/Dialect/Mesh/Transforms/ShardingPropagation.cpp

@@ -9,6 +9,7 @@
 #include "mlir/Dialect/Mesh/Transforms/Passes.h"
 
 #include "mlir/Dialect/Func/IR/FuncOps.h"
+#include "mlir/Dialect/Mesh/IR/MeshDialect.h"
 #include "mlir/Dialect/Mesh/IR/MeshOps.h"
 #include "mlir/Dialect/Mesh/Interfaces/ShardingInterface.h"
 #include "mlir/Pass/Pass.h"

mlir/lib/Dialect/Mesh/Transforms/Spmdization.cpp

@@ -10,6 +10,7 @@
 #include "mlir/Dialect/Arith/IR/Arith.h"
 #include "mlir/Dialect/ControlFlow/IR/ControlFlow.h"
 #include "mlir/Dialect/ControlFlow/IR/ControlFlowOps.h"
+#include "mlir/Dialect/Mesh/IR/MeshDialect.h"
 #include "mlir/Dialect/Mesh/IR/MeshOps.h"
 #include "mlir/Dialect/Tensor/IR/Tensor.h"
 #include "mlir/Dialect/Utils/StaticValueUtils.h"
@@ -54,19 +55,6 @@ int64_t unshardDimension(int64_t dim, int64_t shardCount) {
   return dim * shardCount;
 }
 
-template <typename MeshShape, typename SplitAxes>
-int64_t shardCount(const MeshShape &meshShape, const SplitAxes &splitAxes) {
-  int64_t res = 1;
-  for (auto splitAxis : splitAxes) {
-    int64_t meshDimSize = meshShape[splitAxis];
-    if (ShapedType::isDynamic(meshDimSize)) {
-      return ShapedType::kDynamic;
-    }
-    res *= meshDimSize;
-  }
-  return res;
-}
-
 // Compute the shape for the tensor on each device in the mesh.
 // Example:
 // On a 2x4x? mesh with split axes = [[0], [1], [2]] the shape ?x5x1
@@ -78,9 +66,9 @@ static void shardShape(const InShape &inShape, const MeshShape &meshShape,
   std::copy(llvm::adl_begin(inShape), llvm::adl_end(inShape),
             llvm::adl_begin(outShape));
   for (auto [tensorAxis, innerSplitAxes] : llvm::enumerate(splitAxes)) {
-    outShape[tensorAxis] =
-        shardDimension(inShape[tensorAxis],
-                       shardCount(meshShape, innerSplitAxes.asArrayRef()));
+    outShape[tensorAxis] = shardDimension(
+        inShape[tensorAxis],
+        collectiveProcessGroupSize(innerSplitAxes.asArrayRef(), meshShape));
   }
 }
 

mlir/lib/Dialect/Mesh/Transforms/Transforms.cpp

@@ -8,6 +8,7 @@
 
 #include "mlir/Dialect/Mesh/Transforms/Transforms.h"
 #include "mlir/Dialect/Affine/IR/AffineOps.h"
+#include "mlir/Dialect/Mesh/IR/MeshDialect.h"
 #include "mlir/Dialect/Mesh/IR/MeshOps.h"
 #include "mlir/IR/BuiltinTypes.h"
 #include "mlir/IR/DialectRegistry.h"