[Mlir-commits] [mlir] [mlir][tosa] Fold PadOp to tensor operations (PR #132700)

Georgios Pinitas llvmlistbot at llvm.org
Mon Mar 24 02:48:12 PDT 2025


https://github.com/GeorgeARM created https://github.com/llvm/llvm-project/pull/132700

Add a canonicalizer to enable folding of explicit padding operations to implicit padding attributes of tensor operations.
This enables folding to the following operations:
 - Conv2d
 - DepthwiseConv2d
 - AvgPool2d
 - MaxPool2d

>From ac25641fa3a51fb8b25da028c7c8e4ca3971c11b Mon Sep 17 00:00:00 2001
From: Georgios Pinitas <georgios.pinitas at arm.com>
Date: Sat, 22 Mar 2025 05:41:48 +0000
Subject: [PATCH] [mlir][tosa] Fold PadOp to tensor operations

Add a canonicalizer to enable folding of explicit padding operations to
implicit padding attributes of tensor operations.
This enables folding to the following operations:
 - Conv2d
 - DepthwiseConv2d
 - AvgPool2d
 - MaxPool2d

Signed-off-by: Georgios Pinitas <georgios.pinitas at arm.com>
Co-authored-by: Rob-Hughes-Arm <robert.hughes at arm.com>
---
 mlir/include/mlir/Dialect/Tosa/IR/TosaOps.td  |   5 +
 .../Dialect/Tosa/IR/TosaCanonicalizations.cpp | 204 +++++++++++++++---
 mlir/test/Dialect/Tosa/canonicalize.mlir      |  79 +++++++
 3 files changed, 253 insertions(+), 35 deletions(-)

diff --git a/mlir/include/mlir/Dialect/Tosa/IR/TosaOps.td b/mlir/include/mlir/Dialect/Tosa/IR/TosaOps.td
index 14e15173de7bc..49ee478e1dea9 100644
--- a/mlir/include/mlir/Dialect/Tosa/IR/TosaOps.td
+++ b/mlir/include/mlir/Dialect/Tosa/IR/TosaOps.td
@@ -107,6 +107,7 @@ def Tosa_AvgPool2dOp : Tosa_InferShapedTypeOp<"avg_pool2d"> {
     LogicalResult verifyOutputZeroPoint(int64_t zp);
   }];
 
+  let hasCanonicalizer = 1;
   let hasVerifier = 1;
 }
 
@@ -153,6 +154,8 @@ def Tosa_Conv2DOp : Tosa_ConvOp<"conv2d"> {
   }];
 
   let builders = [Tosa_ConvOpQuantInfoBuilder];
+
+  let hasCanonicalizer = 1;
   let hasVerifier = 1;
 }
 
@@ -244,6 +247,8 @@ def Tosa_DepthwiseConv2DOp : Tosa_ConvOp<"depthwise_conv2d"> {
   }];
 
   let builders = [Tosa_ConvOpQuantInfoBuilder];
+
+  let hasCanonicalizer = 1;
   let hasVerifier = 1;
 }
 
diff --git a/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp b/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp
index 09d2c5d35263c..6a36b7a0cd57d 100644
--- a/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp
+++ b/mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp
@@ -39,6 +39,175 @@ using namespace mlir::tosa;
 // Operator Canonicalizers.
 //===----------------------------------------------------------------------===//
 
+//===----------------------------------------------------------------------===//
+// Tensor Data Engine Operators.
+//===----------------------------------------------------------------------===//
+
+namespace {
+template <typename OpTy>
+struct PoolPadFoldAdaptor;
+
+template <>
+struct PoolPadFoldAdaptor<tosa::AvgPool2dOp> {
+  static void replaceOpWithNewPad(PatternRewriter &rewriter,
+                                  tosa::AvgPool2dOp op, Value padInput,
+                                  ArrayRef<int64_t> newPad) {
+    rewriter.replaceOpWithNewOp<tosa::AvgPool2dOp>(
+        op, op.getType(), padInput, op.getInputZp(), op.getOutputZp(),
+        op.getKernel(), op.getStride(), rewriter.getDenseI64ArrayAttr(newPad),
+        op.getAccType());
+  }
+};
+
+template <>
+struct PoolPadFoldAdaptor<tosa::MaxPool2dOp> {
+  static void replaceOpWithNewPad(PatternRewriter &rewriter,
+                                  tosa::MaxPool2dOp op, Value padInput,
+                                  ArrayRef<int64_t> newPad) {
+    rewriter.replaceOpWithNewOp<tosa::MaxPool2dOp>(
+        op, op.getType(), padInput, op.getKernel(), op.getStride(),
+        rewriter.getDenseI64ArrayAttr(newPad), op.getNanMode());
+  }
+};
+
+template <typename OpTy>
+struct ConvPadFoldAdaptor {
+  static void replaceOpWithNewPad(PatternRewriter &rewriter, OpTy op,
+                                  Value padInput, ArrayRef<int64_t> newPad) {
+    rewriter.replaceOpWithNewOp<OpTy>(
+        op, op.getResult().getType(), padInput, op.getWeight(), op.getBias(),
+        op.getInputZp(), op.getWeightZp(), newPad, op.getStrideAttr(),
+        op.getDilationAttr(), op.getAccType(), op.getLocalBound());
+  }
+};
+
+// Pattern attempts to fold a `tosa.pad` operator to a following tensor
+// operation like `tosa.conv2d` by merging the padding associated with the
+// pad operator directly to the implicit padding of the tensor operation.
+// This helps eliminate the explicit padding operator if unused.
+template <typename OpTy, typename AdaptorTy>
+struct FoldPadToTensorOp : public OpRewritePattern<OpTy> {
+  using OpRewritePattern<OpTy>::OpRewritePattern;
+
+  LogicalResult matchAndRewrite(OpTy tensorOp,
+                                PatternRewriter &rewriter) const override {
+    // Check producer is a tosa::PadOp
+    auto padOp = tensorOp.getInput().template getDefiningOp<tosa::PadOp>();
+    if (!padOp)
+      return rewriter.notifyMatchFailure(tensorOp,
+                                         "Producer must be a tosa::PadOp.");
+
+    // Validate that tensor operation has sane padding
+    const std::vector<int64_t> &tensorOpPad = tensorOp.getPad().vec();
+    if (tensorOpPad.size() != 4) // pad_top, pad_bottom, pad_left, pad_right
+      return rewriter.notifyMatchFailure(
+          tensorOp, "Tensor operation padding shall have 4 elements.");
+
+    // Validate tosa::PadOp padding
+    DenseIntElementsAttr padOpPadding;
+    if (!matchPattern(padOp.getPadding(), m_Constant(&padOpPadding))) {
+      return rewriter.notifyMatchFailure(
+          tensorOp,
+          "The `padding` input specified on the tosa::PadOp must be constant.");
+    }
+    // N_before, N_after, H_before, H_after, W_before, W_after, C_before,
+    // C_after
+    if (padOpPadding.size() != 8)
+      return rewriter.notifyMatchFailure(tensorOp,
+                                         "Pad padding should have 8 elements.");
+    int64_t padNBefore = (*(padOpPadding.begin() + 0)).getLimitedValue();
+    int64_t padNAfter = (*(padOpPadding.begin() + 1)).getLimitedValue();
+    int64_t padHBefore = (*(padOpPadding.begin() + 2)).getLimitedValue();
+    int64_t padHAfter = (*(padOpPadding.begin() + 3)).getLimitedValue();
+    int64_t padWBefore = (*(padOpPadding.begin() + 4)).getLimitedValue();
+    int64_t padWAfter = (*(padOpPadding.begin() + 5)).getLimitedValue();
+    int64_t padCBefore = (*(padOpPadding.begin() + 6)).getLimitedValue();
+    int64_t padCAfter = (*(padOpPadding.begin() + 7)).getLimitedValue();
+
+    if (padNBefore != 0 || padNAfter != 0 || padCBefore != 0 || padCAfter != 0)
+      return rewriter.notifyMatchFailure(
+          tensorOp, "Folding padding in N or C dimensions is not supported.");
+
+    // Fold padding from Pad into the tensor operation
+    // 4 elements - pad_top, pad_bottom, pad_left, pad_right
+    SmallVector<int64_t> foldedPad(tensorOpPad.size());
+    foldedPad[0] = padHBefore + tensorOpPad[0];
+    foldedPad[1] = padHAfter + tensorOpPad[1];
+    foldedPad[2] = padWBefore + tensorOpPad[2];
+    foldedPad[3] = padWAfter + tensorOpPad[3];
+
+    // Replace operator
+    AdaptorTy::replaceOpWithNewPad(rewriter, tensorOp, padOp.getInput1(),
+                                   foldedPad);
+
+    return success();
+  }
+};
+} // namespace
+
+void AvgPool2dOp::getCanonicalizationPatterns(RewritePatternSet &results,
+                                              MLIRContext *context) {
+  results.add<FoldPadToTensorOp<tosa::AvgPool2dOp,
+                                PoolPadFoldAdaptor<tosa::AvgPool2dOp>>>(
+      context);
+}
+
+void Conv2DOp::getCanonicalizationPatterns(RewritePatternSet &results,
+                                           MLIRContext *context) {
+  results.add<
+      FoldPadToTensorOp<tosa::Conv2DOp, ConvPadFoldAdaptor<tosa::Conv2DOp>>>(
+      context);
+}
+
+void DepthwiseConv2DOp::getCanonicalizationPatterns(RewritePatternSet &results,
+                                                    MLIRContext *context) {
+  results.add<FoldPadToTensorOp<tosa::DepthwiseConv2DOp,
+                                ConvPadFoldAdaptor<tosa::DepthwiseConv2DOp>>>(
+      context);
+}
+
+struct MaxPool2dIsNoOp : public OpRewritePattern<tosa::MaxPool2dOp> {
+  using OpRewritePattern::OpRewritePattern;
+
+  LogicalResult matchAndRewrite(tosa::MaxPool2dOp op,
+                                PatternRewriter &rewriter) const override {
+    Value input = op.getInput();
+    Value output = op.getOutput();
+    ShapedType inputType = llvm::cast<ShapedType>(input.getType());
+    ShapedType outputType = llvm::cast<ShapedType>(output.getType());
+
+    if (!inputType.hasStaticShape() || !outputType.hasStaticShape()) {
+      return failure();
+    }
+
+    // If the output and input shapes are 1x1, then this is a no op.
+    ArrayRef<int64_t> outputShape = outputType.getShape();
+    if (outputShape[1] != 1 || outputShape[2] != 1) {
+      return failure();
+    }
+
+    ArrayRef<int64_t> inputShape = inputType.getShape();
+    if (inputShape[1] != 1 || inputShape[2] != 1) {
+      return failure();
+    }
+
+    rewriter.replaceOp(op, input);
+    return success();
+  }
+};
+
+void MaxPool2dOp::getCanonicalizationPatterns(RewritePatternSet &results,
+                                              MLIRContext *context) {
+  results.add<MaxPool2dIsNoOp,
+              FoldPadToTensorOp<tosa::MaxPool2dOp,
+                                PoolPadFoldAdaptor<tosa::MaxPool2dOp>>>(
+      context);
+}
+
+//===----------------------------------------------------------------------===//
+// Data Layout / Memory Reinterpretation.
+//===----------------------------------------------------------------------===//
+
 struct ConcatOptimization : public OpRewritePattern<tosa::ConcatOp> {
   using OpRewritePattern<tosa::ConcatOp>::OpRewritePattern;
 
@@ -175,41 +344,6 @@ void TransposeOp::getCanonicalizationPatterns(RewritePatternSet &results,
   results.add<ConsolidateTransposeOptimization, TransposeIsReshape>(context);
 }
 
-struct MaxPool2dIsNoOp : public OpRewritePattern<tosa::MaxPool2dOp> {
-  using OpRewritePattern::OpRewritePattern;
-
-  LogicalResult matchAndRewrite(tosa::MaxPool2dOp op,
-                                PatternRewriter &rewriter) const override {
-    Value input = op.getInput();
-    Value output = op.getOutput();
-    ShapedType inputType = llvm::cast<ShapedType>(input.getType());
-    ShapedType outputType = llvm::cast<ShapedType>(output.getType());
-
-    if (!inputType.hasStaticShape() || !outputType.hasStaticShape()) {
-      return failure();
-    }
-
-    // If the output and input shapes are 1x1, then this is a no op.
-    ArrayRef<int64_t> outputShape = outputType.getShape();
-    if (outputShape[1] != 1 || outputShape[2] != 1) {
-      return failure();
-    }
-
-    ArrayRef<int64_t> inputShape = inputType.getShape();
-    if (inputShape[1] != 1 || inputShape[2] != 1) {
-      return failure();
-    }
-
-    rewriter.replaceOp(op, input);
-    return success();
-  }
-};
-
-void MaxPool2dOp::getCanonicalizationPatterns(RewritePatternSet &results,
-                                              MLIRContext *context) {
-  results.add<MaxPool2dIsNoOp>(context);
-}
-
 struct ClampIsNoOp : public OpRewritePattern<tosa::ClampOp> {
   using OpRewritePattern::OpRewritePattern;
 
diff --git a/mlir/test/Dialect/Tosa/canonicalize.mlir b/mlir/test/Dialect/Tosa/canonicalize.mlir
index 077a6cee0a1bb..84bc86384ce85 100644
--- a/mlir/test/Dialect/Tosa/canonicalize.mlir
+++ b/mlir/test/Dialect/Tosa/canonicalize.mlir
@@ -9,6 +9,85 @@ func.func @argmax_nofold(%arg0: tensor<?x1xf32>) -> tensor<1xi32> {
 
 // -----
 
+// CHECK-LABEL: @pad_wh_avg_pool2d_fold
+func.func @pad_wh_avg_pool2d_fold(%input: tensor<1x10x8x3xf32>) -> tensor<1x6x5x3xf32> {
+  // CHECK-NOT: tosa.pad
+  // CHECK: tosa.avg_pool2d
+  // CHECK-SAME: pad = array<i64: 1, 1, 1, 1>
+  %pad_shape = tosa.const_shape { values = dense<[0, 0, 1, 0, 1, 0, 0, 0]> : tensor<8xindex>} : () -> !tosa.shape<8>
+  %pad_const = "tosa.const"() <{values = dense<0.0> : tensor<1xf32>}> : ()-> tensor<1xf32>
+  %input_zp = "tosa.const"() <{values = dense<0.0> : tensor<1xf32>}> : ()-> tensor<1xf32>
+  %output_zp = "tosa.const"() <{values = dense<0.0> : tensor<1xf32>}> : ()-> tensor<1xf32>
+  %padded = tosa.pad %input, %pad_shape, %pad_const : (tensor<1x10x8x3xf32>, !tosa.shape<8>, tensor<1xf32>) -> tensor<1x11x9x3xf32>
+  %pool = tosa.avg_pool2d %padded, %input_zp, %output_zp {acc_type = f32, kernel = array<i64: 2, 2>, pad = array<i64: 0, 1, 0, 1>, stride = array<i64: 2, 2>} : (tensor<1x11x9x3xf32>, tensor<1xf32>, tensor<1xf32>) -> tensor<1x6x5x3xf32>
+  return %pool : tensor<1x6x5x3xf32>
+}
+
+// -----
+
+// CHECK-LABEL: @pad_wh_conv2d_fold
+func.func @pad_wh_conv2d_fold(%input: tensor<1x8x4x3xf32>, %weight: tensor<1x3x3x3xf32>, %bias: tensor<1xf32>) -> tensor<1x10x8x1xf32> {
+  // CHECK-NOT: tosa.pad
+  // CHECK: tosa.conv2d
+  // CHECK-SAME: pad = array<i64: 2, 2, 3, 3>
+  %pad_shape = tosa.const_shape { values = dense<[0, 0, 1, 1, 2, 2, 0, 0]> : tensor<8xindex>} : () -> !tosa.shape<8>
+  %pad_const = "tosa.const"() <{values = dense<0.0> : tensor<1xf32>}> : ()-> tensor<1xf32>
+  %input_zp = "tosa.const"() <{values = dense<0.0> : tensor<1xf32>}> : ()-> tensor<1xf32>
+  %weight_zp = "tosa.const"() <{values = dense<0.0> : tensor<1xf32>}> : ()-> tensor<1xf32>
+  %padded = tosa.pad %input, %pad_shape, %pad_const : (tensor<1x8x4x3xf32>, !tosa.shape<8>, tensor<1xf32>) -> tensor<1x10x8x3xf32>
+  %conv = tosa.conv2d %padded, %weight, %bias, %input_zp, %weight_zp {acc_type = f32, pad = array<i64: 1, 1, 1, 1>, stride = array<i64: 1, 1>, dilation = array<i64: 1, 1>} : (tensor<1x10x8x3xf32>, tensor<1x3x3x3xf32>, tensor<1xf32>, tensor<1xf32>, tensor<1xf32>) -> tensor<1x10x8x1xf32>
+  return %conv : tensor<1x10x8x1xf32>
+}
+
+// -----
+
+// CHECK-LABEL: @pad_bwh_conv2d_nofold
+func.func @pad_bwh_conv2d_nofold(%input: tensor<1x8x4x3xf32>, %weight: tensor<1x3x3x3xf32>, %bias: tensor<1xf32>) -> tensor<3x10x8x1xf32> {
+  // CHECK: tosa.pad
+  // CHECK: tosa.conv2d
+  // CHECK-SAME: pad = array<i64: 1, 1, 1, 1>
+  %pad_shape = tosa.const_shape { values = dense<[1, 1, 1, 1, 2, 2, 0, 0]> : tensor<8xindex>} : () -> !tosa.shape<8>
+  %pad_const = "tosa.const"() <{values = dense<0.0> : tensor<1xf32>}> : ()-> tensor<1xf32>
+  %input_zp = "tosa.const"() <{values = dense<0.0> : tensor<1xf32>}> : ()-> tensor<1xf32>
+  %weight_zp = "tosa.const"() <{values = dense<0.0> : tensor<1xf32>}> : ()-> tensor<1xf32>
+  %padded = tosa.pad %input, %pad_shape, %pad_const : (tensor<1x8x4x3xf32>, !tosa.shape<8>, tensor<1xf32>) -> tensor<3x10x8x3xf32>
+  %conv = tosa.conv2d %padded, %weight, %bias, %input_zp, %weight_zp {acc_type = f32, pad = array<i64: 1, 1, 1, 1>, stride = array<i64: 1, 1>, dilation = array<i64: 1, 1>} : (tensor<3x10x8x3xf32>, tensor<1x3x3x3xf32>, tensor<1xf32>, tensor<1xf32>, tensor<1xf32>) -> tensor<3x10x8x1xf32>
+  return %conv : tensor<3x10x8x1xf32>
+}
+
+// -----
+
+// CHECK-LABEL: @pad_wh_depthwise_conv2d_fold
+func.func @pad_wh_depthwise_conv2d_fold(%input: tensor<1x8x4x3xf32>, %weight: tensor<3x3x3x1xf32>, %bias: tensor<3xf32>) -> tensor<1x10x8x3xf32> {
+  // CHECK-NOT: tosa.pad
+  // CHECK: tosa.depthwise_conv2d
+  // CHECK-SAME: pad = array<i64: 2, 2, 3, 3>
+  %pad_shape = tosa.const_shape { values = dense<[0, 0, 1, 1, 2, 2, 0, 0]> : tensor<8xindex>} : () -> !tosa.shape<8>
+  %pad_const = "tosa.const"() <{values = dense<0.0> : tensor<1xf32>}> : ()-> tensor<1xf32>
+  %input_zp = "tosa.const"() <{values = dense<0.0> : tensor<1xf32>}> : ()-> tensor<1xf32>
+  %weight_zp = "tosa.const"() <{values = dense<0.0> : tensor<1xf32>}> : ()-> tensor<1xf32>
+  %padded = tosa.pad %input, %pad_shape, %pad_const : (tensor<1x8x4x3xf32>, !tosa.shape<8>, tensor<1xf32>) -> tensor<1x10x8x3xf32>
+  %conv = tosa.depthwise_conv2d %padded, %weight, %bias, %input_zp, %weight_zp {acc_type = f32, pad = array<i64: 1, 1, 1, 1>, stride = array<i64: 1, 1>, dilation = array<i64: 1, 1>} : (tensor<1x10x8x3xf32>, tensor<3x3x3x1xf32>, tensor<3xf32>, tensor<1xf32>, tensor<1xf32>) -> tensor<1x10x8x3xf32>
+  return %conv : tensor<1x10x8x3xf32>
+}
+
+// -----
+
+
+// CHECK-LABEL: @pad_wh_max_pool2d_fold
+func.func @pad_wh_max_pool2d_fold(%input: tensor<1x10x8x3xf32>) -> tensor<1x6x5x3xf32> {
+  // CHECK-NOT: tosa.pad
+  // CHECK: tosa.max_pool2d
+  // CHECK-SAME: pad = array<i64: 1, 1, 1, 1>
+  %pad_shape = tosa.const_shape { values = dense<[0, 0, 1, 0, 1, 0, 0, 0]> : tensor<8xindex>} : () -> !tosa.shape<8>
+  %pad_const = "tosa.const"() <{values = dense<0.0> : tensor<1xf32>}> : ()-> tensor<1xf32>
+  %padded = tosa.pad %input, %pad_shape, %pad_const : (tensor<1x10x8x3xf32>, !tosa.shape<8>, tensor<1xf32>) -> tensor<1x11x9x3xf32>
+  %pool = tosa.max_pool2d %padded {kernel = array<i64: 2, 2>, pad = array<i64: 0, 1, 0, 1>, stride = array<i64: 2, 2>} : (tensor<1x11x9x3xf32>) -> tensor<1x6x5x3xf32>
+  return %pool : tensor<1x6x5x3xf32>
+}
+
+// -----
+
 // CHECK-LABEL: @add_bcast_zero_int
 func.func @add_bcast_zero_int(%arg0: tensor<4x2x3xi32>) -> tensor<4x2x3xi32> {
   // CHECK-NOT: tosa.add



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