[MLIR][Linalg] Add max named op to linalg

I've been trying to come up with a simple and clean implementation for
ReLU. TOSA uses `clamp` which is probably the goal, but that means
table-gen to make it efficient (attributes, only lower `min` or `max`).

For now, `max` is a reasonable named op despite ReLU, so we can start
using it for tiling and fusion, and upon success, we create a more
complete op `clamp` that doesn't need a whole tensor filled with zeroes
or ones to implement the different activation functions.

As with other named ops, we start "requiring" type casts and broadcasts,
and zero filled constant tensors to a more complex pattern-matcher, and
can slowly simplify with attributes or structured matchers (ex. PDL) in
the future.

Differential Revision: https://reviews.llvm.org/D154703

mlir/include/mlir/Dialect/Linalg/IR/LinalgNamedStructuredOps.yaml

@@ -613,6 +613,55 @@ structured_op: !LinalgStructuredOpConfig
         - !ScalarExpression
           scalar_arg: rhs
 --- !LinalgOpConfig
+metadata: !LinalgOpMetadata
+  name: max
+  cpp_class_name: MaxOp
+  doc: |-
+    Takes the max (signed) between the input and a constant.
+
+    The shapes and element types must be identical. The appropriate casts,
+    broadcasts and reductions should be done previously to calling this op.
+
+    This means reduction/broadcast/element cast semantics is explicit. Further
+    passes can take that into account when lowering this code. For example,
+    a `linalg.broadcast` + `linalg.div` sequence can be lowered to a
+    `linalg.generic` with different affine maps for the two operands.
+structured_op: !LinalgStructuredOpConfig
+  args:
+  - !LinalgOperandDefConfig
+    name: lhs
+    kind: input_tensor
+    type_var: T
+    shape_map: affine_map<() -> ()>
+  - !LinalgOperandDefConfig
+    name: rhs
+    kind: input_tensor
+    type_var: T
+    shape_map: affine_map<() -> ()>
+  - !LinalgOperandDefConfig
+    name: out
+    kind: output_tensor
+    type_var: T
+    shape_map: affine_map<() -> ()>
+  indexing_maps: !LinalgIndexingMapsConfig
+    static_indexing_maps:
+    - affine_map<() -> ()>
+    - affine_map<() -> ()>
+    - affine_map<() -> ()>
+  iterator_types: []
+  assignments:
+  - !ScalarAssign
+    arg: out
+    value: !ScalarExpression
+      scalar_fn:
+        kind: binary
+        fn_name: max_signed
+        operands:
+        - !ScalarExpression
+          scalar_arg: lhs
+        - !ScalarExpression
+          scalar_arg: rhs
+--- !LinalgOpConfig
 metadata: !LinalgOpMetadata
   name: matmul
   cpp_class_name: MatmulOp

mlir/python/mlir/dialects/linalg/opdsl/ops/core_named_ops.py

@@ -219,6 +219,25 @@ def div_unsigned(
     O[None] = lhs[None] / rhs[None]
 
 
+@linalg_structured_op
+def max(
+    lhs=TensorDef(T1),
+    rhs=TensorDef(T1),
+    O=TensorDef(T1, output=True),
+):
+    """Takes the max (signed) between two inputs, elementwise.
+
+    The shapes and element types must be identical. The appropriate casts,
+    broadcasts and reductions should be done previously to calling this op.
+
+    This means reduction/broadcast/element cast semantics is explicit. Further
+    passes can take that into account when lowering this code. For example,
+    a `linalg.broadcast` + `linalg.div` sequence can be lowered to a
+    `linalg.generic` with different affine maps for the two operands.
+    """
+    O[None] = BinaryFn.max_signed(lhs[None], rhs[None])
+
+
 @linalg_structured_op
 def matmul(
     A=TensorDef(T1, S.M, S.K),

mlir/test/Dialect/Linalg/generalize-named-ops.mlir

@@ -537,3 +537,28 @@ func.func @generalize_negf(%arg: memref<7x14x21xf32>, %out: memref<7x14x21xf32>)
 // CHECK:         ^{{.+}}(%[[BBARG0:.+]]: f32, %[[BBARG1:.+]]: f32)
 // CHECK-NEXT:      %[[negf:.+]] = arith.negf %[[BBARG0]] : f32
 // CHECK-NEXT:      linalg.yield %[[negf]] : f32
+
+// -----
+
+func.func @generalize_max(%lhs: memref<7x14x21xf32>, %rhs: memref<7x14x21xf32>,
+                          %out: memref<7x14x21xf32>) {
+  linalg.max ins(%lhs, %rhs : memref<7x14x21xf32>, memref<7x14x21xf32>)
+             outs(%out : memref<7x14x21xf32>)
+  return
+}
+
+// CHECK: #[[MAP:.+]] = affine_map<(d0, d1, d2) -> (d0, d1, d2)>
+
+// CHECK: func @generalize_max
+// CHECK-SAME: (%[[LHS:.+]]: memref<7x14x21xf32>, %[[RHS:.+]]: memref<7x14x21xf32>,
+// CHECK-SAME:  %[[OUT:.+]]: memref<7x14x21xf32>)
+
+// CHECK: linalg.generic
+// CHECK-SAME: indexing_maps = [#[[MAP]], #[[MAP]], #[[MAP]]]
+// CHECK-SAME: iterator_types = ["parallel", "parallel", "parallel"]}
+// CHECK-SAME:  ins(%[[LHS]], %[[RHS]] : memref<7x14x21xf32>, memref<7x14x21xf32>)
+// CHECK-SAME: outs(%[[OUT]] : memref<7x14x21xf32>)
+
+// CHECK:         ^{{.+}}(%[[BBARG0:.+]]: f32, %[[BBARG1:.+]]: f32, %[[BBARG2:.+]]: f32)
+// CHECK-NEXT:      %[[max:.+]] = arith.maxf %[[BBARG0]], %[[BBARG1]] : f32
+// CHECK-NEXT:      linalg.yield %[[max]] : f32

mlir/test/Dialect/Linalg/named-ops-fail.mlir

@@ -173,3 +173,19 @@ func.func @negf_broadcast(%arg: memref<8x16xf32>, %out: memref<4x8x16xf32>) {
   linalg.negf ins(%arg : memref<8x16xf32>) outs(%out: memref<4x8x16xf32>)
   return
 }
+
+// -----
+
+func.func @max_type_cast(%arg0: memref<4x8x16xf32>, %arg1: memref<4x8x16xf16>, %arg2: memref<4x8x16xf32>) {
+  // CHECK: op requires the same type for all operands and results
+  linalg.max ins(%arg0, %arg1 : memref<4x8x16xf32>, memref<4x8x16xf16>) outs(%arg2: memref<4x8x16xf32>)
+  return
+}
+
+// -----
+
+func.func @max_broadcast(%arg0: memref<8x16xf32>, %arg1: memref<4x8x16xf32>, %arg2: memref<4x8x16xf32>) {
+  // CHECK: op expected operand rank (2) to match the result rank of indexing_map #0 (3)
+  linalg.max ins(%arg0, %arg1 : memref<8x16xf32>, memref<4x8x16xf32>) outs(%arg2: memref<4x8x16xf32>)
+  return
+}

mlir/test/Dialect/Linalg/named-ops.mlir

@@ -1540,3 +1540,37 @@ func.func @negf_tensor(%arg0: tensor<4x8x16xf32>) -> tensor<4x8x16xf32> {
   %1 = linalg.negf ins(%arg0 : tensor<4x8x16xf32>) outs(%0: tensor<4x8x16xf32>) -> tensor<4x8x16xf32>
   return %1 : tensor<4x8x16xf32>
 }
+
+// -----
+
+// CHECK-LABEL: func @max_dynamic
+func.func @max_dynamic(%arg0: memref<?x?x?xf32>, %arg1: memref<?x?x?xf32>, %arg2: memref<?x?x?xf32>) {
+  // CHECK: linalg.max
+  // CHECK-SAME: ins(%{{.+}}, %{{.+}} : memref<?x?x?xf32>, memref<?x?x?xf32>)
+  // CHECK-SAME: outs(%{{.+}} : memref<?x?x?xf32>)
+  linalg.max ins(%arg0, %arg1 : memref<?x?x?xf32>, memref<?x?x?xf32>) outs(%arg2: memref<?x?x?xf32>)
+  return
+}
+
+// -----
+
+// CHECK-LABEL: func @max_static
+func.func @max_static(%arg0: memref<4x8x16xf32>, %arg1: memref<4x8x16xf32>, %arg2: memref<4x8x16xf32>) {
+  // CHECK: linalg.max
+  // CHECK-SAME: ins(%{{.+}}, %{{.+}} : memref<4x8x16xf32>, memref<4x8x16xf32>)
+  // CHECK-SAME: outs(%{{.+}} : memref<4x8x16xf32>)
+  linalg.max ins(%arg0, %arg1 : memref<4x8x16xf32>, memref<4x8x16xf32>) outs(%arg2: memref<4x8x16xf32>)
+  return
+}
+
+// -----
+
+// CHECK-LABEL: func @max_tensor
+func.func @max_tensor(%arg0: tensor<4x8x16xf32>, %arg1: tensor<4x8x16xf32>) -> tensor<4x8x16xf32> {
+  %0 = tensor.empty() : tensor<4x8x16xf32>
+  // CHECK: linalg.max
+  // CHECK-SAME: ins(%{{.+}}, %{{.+}} : tensor<4x8x16xf32>, tensor<4x8x16xf32>)
+  // CHECK-SAME: outs(%{{.+}} : tensor<4x8x16xf32>)
+  %1 = linalg.max ins(%arg0, %arg1 : tensor<4x8x16xf32>, tensor<4x8x16xf32>) outs(%0: tensor<4x8x16xf32>) -> tensor<4x8x16xf32>
+  return %1 : tensor<4x8x16xf32>
+}