[mlir][tosa] Add verifier for ArgMax operator

Verifier ensures that operator is valid by checking:

* Output type is of integer type
* Axis is within the rank of the tensor

Signed-off-by: Georgios Pinitas <[email protected]>

Author: GeorgeARM

mlir/include/mlir/Dialect/Tosa/IR/TosaOps.td

@@ -48,6 +48,8 @@ def Tosa_ArgMaxOp : Tosa_InferShapedTypeOp<"argmax"> {
   let results = (outs
     Tosa_Tensor: $output
   );
+
+  let hasVerifier = 1;
 }
 
 //===----------------------------------------------------------------------===//

mlir/lib/Dialect/Tosa/IR/TosaOps.cpp

@@ -211,6 +211,21 @@ template <typename T> static LogicalResult verifyConvOp(T op) {
   return success();
 }
 
+LogicalResult tosa::ArgMaxOp::verify() {
+  // Ensure output is of 32-bit integer
+  const auto resultETy = llvm::cast<ShapedType>(getType()).getElementType();
+  if (!resultETy.isIntOrIndex())
+    return emitOpError("result tensor is not of integer type");
+
+  // Ensure axis is within the tensor rank
+  const auto inputType = llvm::cast<ShapedType>(getInput().getType());
+  const int64_t axis = getAxisAttr().getInt();
+  if (inputType.hasRank() && ((axis < 0) || axis >= inputType.getRank()))
+    return emitOpError("specified axis is outside the rank of the tensor");
+
+  return success();
+}
+
 LogicalResult tosa::AvgPool2dOp::verify() {
   auto inputType = llvm::cast<ShapedType>(getInput().getType());
   if (hasZeroDimension(inputType))

mlir/test/Dialect/Tosa/canonicalize.mlir

@@ -1,10 +1,10 @@
 // RUN: mlir-opt -canonicalize="test-convergence" %s | FileCheck %s
 
 // CHECK-LABEL: @argmax_nofold
-func.func @argmax_nofold(%arg0: tensor<?x1xf32>) -> tensor<?x1xf32> {
+func.func @argmax_nofold(%arg0: tensor<?x1xf32>) -> tensor<?x1xi32> {
   // CHECK: tosa.argmax
-  %0 = tosa.argmax %arg0 {axis = 0 : i32}: (tensor<?x1xf32>) -> tensor<?x1xf32>
-  return %0 : tensor<?x1xf32>
+  %0 = tosa.argmax %arg0 {axis = 0 : i32}: (tensor<?x1xf32>) -> tensor<?x1xi32>
+  return %0 : tensor<?x1xi32>
 }
 
 // CHECK-LABEL: @add_bcast_zero_int

mlir/test/Dialect/Tosa/constrained_shapes.mlir

@@ -6,6 +6,6 @@
 // Uses argmax as canonical example to validate constrained TOSA tensor shapes.
 // CHECK-LABEL: argmax
 func.func @test_argmax(%arg0: tensor<?xf32>) -> tensor<?xi32> {
-  %0 = "tosa.argmax"(%arg0) {axis = 1 : i32} : (tensor<?xf32>) -> tensor<?xi32>
+  %0 = "tosa.argmax"(%arg0) {axis = 0 : i32} : (tensor<?xf32>) -> tensor<?xi32>
   return %0 : tensor<?xi32>
 }

mlir/test/Dialect/Tosa/level_check.mlir

@@ -1,10 +1,10 @@
 // RUN: mlir-opt %s -split-input-file -verify-diagnostics --tosa-validate
 
 
-func.func @test_argmax(%arg0: tensor<1x1x1x1x29x29x4xf32>) -> tensor<1x1x1x1x29x4xf32> {
+func.func @test_argmax(%arg0: tensor<1x1x1x1x29x29x4xf32>) -> tensor<1x1x1x1x29x4xi32> {
   // expected-error@+1 {{'tosa.argmax' op failed level check: operand rank(shape) <= MAX_RANK}}
-  %0 = "tosa.argmax"(%arg0) {axis = 4 : i32} : (tensor<1x1x1x1x29x29x4xf32>) -> tensor<1x1x1x1x29x4xf32>
-  return %0 : tensor<1x1x1x1x29x4xf32>
+  %0 = "tosa.argmax"(%arg0) {axis = 4 : i32} : (tensor<1x1x1x1x29x29x4xf32>) -> tensor<1x1x1x1x29x4xi32>
+  return %0 : tensor<1x1x1x1x29x4xi32>
 }
 
 // -----