[mlir][tosa] tosa.resize canonicalizer for trivial noop

[rsuderman]

Summary

If the scaling factor is by 1 with no offset or border, then the
resize is a no-op.

[rsuderman]

git-clang-format

[dcaballe]

Thanks, Robert! A couple of minor comments. LGTM once you address them.

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

850

Perhaps add some doc about the cases that are being folded?

mlir/test/Dialect/Tosa/canonicalize.mlir

416

Missing CHECK? Same below?

[rsuderman]

fixed for comments

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

let arguments = (ins
     Tosa_IntArrayAttr2:$offset,
     Tosa_IntArrayAttr2:$border,
     Tosa_ResizeTypeAttr:$mode
   );
 
   let results = (outs
     Tosa_Tensor4D:$output
   );
+
+  let hasFolder = 1;
 }
 
 //===----------------------------------------------------------------------===//
 // TOSA Spec Section 2.12
 // Operator Class: Type Conversion.
 //===----------------------------------------------------------------------===//
 
 //===----------------------------------------------------------------------===//

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

 //===- TosaCanonicalizations.cpp - Canonicalization patterns & folders ----===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
 // \file
 // TOSA canonicalization patterns and folders.
 //
 //===----------------------------------------------------------------------===//
 
 #include "mlir/Dialect/Quant/QuantOps.h"
 #include "mlir/Dialect/Tensor/IR/Tensor.h"
 #include "mlir/Dialect/Tosa/IR/TosaOps.h"
+#include "mlir/Dialect/Tosa/Utils/CoversionUtils.h"
 #include "mlir/Dialect/Tosa/Utils/QuantUtils.h"
 #include "mlir/Dialect/Tosa/Utils/ShapeUtils.h"
 #include "mlir/IR/BuiltinTypes.h"
 #include "mlir/IR/DialectImplementation.h"
 #include "mlir/IR/Matchers.h"
 #include "mlir/IR/PatternMatch.h"
 #include "mlir/Transforms/FoldUtils.h"
 #include "mlir/Transforms/InliningUtils.h"
if (operands[1]) {
     if (densePad.isSplat() && densePad.getSplatValue<APInt>().isZero()) {
       return getInput1();
     }
   }
 
   return {};
 }
 
+// Fold away cases where a tosa.resize operation returns a copy
+// of the input image.
+OpFoldResult ResizeOp::fold(ArrayRef<Attribute> operands) {
+  SmallVector<int32_t> scale, offset, border;
+  getValuesFromIntArrayAttribute(getScale(), scale);
+  getValuesFromIntArrayAttribute(getOffset(), offset);
+  getValuesFromIntArrayAttribute(getBorder(), border);
+
+  // Check unit scaling.
+  if (scale[0] != scale[1] || scale[2] != scale[3]) {
+    return {};
+  }
+
+  // There should be no offset.
+  if (offset[0] != 0 || offset[1] != 0) {
+    return {};
+  }
+
+  // There should be no border.
+  if (border[0] != 0 || border[1] != 0) {
+    return {};
+  }
+
+  auto input = getInput();
+  auto inputTy = input.getType().cast<RankedTensorType>();
+  auto resultTy = getType().cast<RankedTensorType>();
+  if (inputTy != resultTy)
+    return {};
+
+  return input;
+}
+
 OpFoldResult ReverseOp::fold(ArrayRef<Attribute> operands) {
   auto operand = getInput();
   auto operandTy = operand.getType().cast<ShapedType>();
   auto axis = getAxis();
   auto operandAttr = operands[0].dyn_cast_or_null<SplatElementsAttr>();
   if (operandAttr)
     return operandAttr;
 

mlir/test/Dialect/Tosa/canonicalize.mlir

 // CHECK-LABEL: @single_bit_reshape
 // https://github.com/llvm/llvm-project/issues/55440
 func.func @single_bit_reshape() -> tensor<1xi1> {
   // CHECK: "tosa.const"() {value = dense<true> : tensor<1xi1>}
   %0 = arith.constant dense<true> : tensor<1x1xi1>
   %1 = "tosa.reshape"(%0) {new_shape = [1]} : (tensor<1x1xi1>) -> tensor<1xi1>
   return %1 : tensor<1xi1>
 }
+
+// -----
+
+// CHECK-LABEL: @fold_resize_nearest
+func.func @fold_resize_nearest(%arg0 : tensor<1x15x13x1xi8>) -> tensor<1x15x13x1xi8> {
+  // CHECK: return %arg0
+  %resize = "tosa.resize"(%arg0) {mode = "NEAREST_NEIGHBOR", scale = [2, 2, 1, 1], offset = [0, 0], border = [0, 0]} : (tensor<1x15x13x1xi8>) -> tensor<1x15x13x1xi8>
+  return %resize : tensor<1x15x13x1xi8>
+}
+
+// -----
+
+// CHECK-LABEL: @fold_resize_bilinear
+func.func @fold_resize_bilinear(%arg0 : tensor<1x15x13x1xi8>) -> tensor<1x15x13x1xi8> {
+  // CHECK: return %arg0
+  %resize = "tosa.resize"(%arg0) {mode = "BILINEAR", scale = [2, 2, 1, 1], offset = [0, 0], border = [0, 0]} : (tensor<1x15x13x1xi8>) -> tensor<1x15x13x1xi8>
+  return %resize : tensor<1x15x13x1xi8>
+}