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[MLIR] fix shape.broadcast canonicalize with all empty shape operands #118941

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merged 2 commits into from
Dec 20, 2024

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YellowHCH
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Example: all the operands of shape.broadcast are empty tensors.

func.func @all_empty(%arg0: tensor<f32>) -> tensor<0xindex> {
  %1 = shape.shape_of %arg0 : tensor<f32> -> tensor<0xindex>
  %2 = shape.const_shape [] : tensor<0xindex>
  %3 = shape.broadcast %1, %2, %1 : tensor<0xindex>, tensor<0xindex>, tensor<0xindex> -> tensor<0xindex>
  return %3 : tensor<0xindex>
}

One can reproduce crash when canonicalize with down-top order, cmd like this:
mlir-opt -split-input-file -allow-unregistered-dialect -canonicalize="test-convergence top-down=0" %s

The root cause is when all operands are empty tensor, RemoveEmptyShapeOperandsPattern would filter out all operands.

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llvmbot commented Dec 6, 2024

@llvm/pr-subscribers-mlir

Author: Chenhui Huang (YellowHCH)

Changes

Example: all the operands of shape.broadcast are empty tensors.

func.func @<!-- -->all_empty(%arg0: tensor&lt;f32&gt;) -&gt; tensor&lt;0xindex&gt; {
  %1 = shape.shape_of %arg0 : tensor&lt;f32&gt; -&gt; tensor&lt;0xindex&gt;
  %2 = shape.const_shape [] : tensor&lt;0xindex&gt;
  %3 = shape.broadcast %1, %2, %1 : tensor&lt;0xindex&gt;, tensor&lt;0xindex&gt;, tensor&lt;0xindex&gt; -&gt; tensor&lt;0xindex&gt;
  return %3 : tensor&lt;0xindex&gt;
}

One can reproduce crash when canonicalize with down-top order, cmd like this:
mlir-opt -split-input-file -allow-unregistered-dialect -canonicalize="test-convergence top-down=0" %s

The root cause is when all operands are empty tensor, RemoveEmptyShapeOperandsPattern would filter out all operands.


Full diff: https://github.com/llvm/llvm-project/pull/118941.diff

2 Files Affected:

  • (modified) mlir/lib/Dialect/Shape/IR/Shape.cpp (+6)
  • (modified) mlir/test/Dialect/Shape/canonicalize.mlir (+16)
diff --git a/mlir/lib/Dialect/Shape/IR/Shape.cpp b/mlir/lib/Dialect/Shape/IR/Shape.cpp
index bebfaa8c1ea822..8779fe837c7ae7 100644
--- a/mlir/lib/Dialect/Shape/IR/Shape.cpp
+++ b/mlir/lib/Dialect/Shape/IR/Shape.cpp
@@ -699,6 +699,12 @@ struct RemoveEmptyShapeOperandsPattern : public OpRewritePattern<OpTy> {
                                                  isPotentiallyNonEmptyShape);
 
     // Reduce op to equivalent without empty shape operands.
+    if (newOperands.empty()) {
+      rewriter.replaceOpWithNewOp<ConstShapeOp>(
+          op, op->getResultTypes().front(), rewriter.getIndexTensorAttr({}));
+      return success();
+    }
+
     if (newOperands.size() < op.getNumOperands()) {
       rewriter.replaceOpWithNewOp<OpTy>(op, op->getResultTypes(), newOperands,
                                         op->getAttrs());
diff --git a/mlir/test/Dialect/Shape/canonicalize.mlir b/mlir/test/Dialect/Shape/canonicalize.mlir
index 5b98a7790debf2..d55e0d8291cfef 100644
--- a/mlir/test/Dialect/Shape/canonicalize.mlir
+++ b/mlir/test/Dialect/Shape/canonicalize.mlir
@@ -1,4 +1,5 @@
 // RUN: mlir-opt -split-input-file -allow-unregistered-dialect -canonicalize="test-convergence" %s | FileCheck %s
+// RUN: mlir-opt -split-input-file -allow-unregistered-dialect -canonicalize="test-convergence top-down=1" %s | FileCheck %s
 
 // CHECK-LABEL: func @f
 func.func @f(%arg0: tensor<2x3x4xf32>) -> tensor<3xindex> {
@@ -134,6 +135,21 @@ func.func @all_but_one_empty(%arg0 : !shape.shape) -> !shape.shape {
 
 // -----
 
+// All operands are known empty shapes.
+// CHECK-LABEL: @all_empty
+// CHECK-SAME:  (%[[ARG_0:.*]]: tensor<f32>, %[[ARG_1:.*]]: tensor<i1>)
+func.func @all_empty(%arg0: tensor<f32>, %arg1: tensor<i1>) -> tensor<0xindex> {
+  // CHECK: %[[CST:.*]] = shape.const_shape [] : tensor<0xindex>
+  // CHECK: return %[[CST]] : tensor<0xindex>
+  %1 = shape.shape_of %arg0 : tensor<f32> -> tensor<0xindex>
+  %2 = shape.shape_of %arg1 : tensor<i1> -> tensor<0xindex>
+  %3 = shape.const_shape [] : tensor<0xindex>
+  %4 = shape.broadcast %1, %2, %3 : tensor<0xindex>, tensor<0xindex>, tensor<0xindex> -> tensor<0xindex>
+  return %4 : tensor<0xindex>
+}
+
+// -----
+
 // Partial folding.
 // CHECK-LABEL: @partial_folding
 // CHECK-SAME:  (%[[ARG:.*]]: !shape.shape)

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llvmbot commented Dec 6, 2024

@llvm/pr-subscribers-mlir-shape

Author: Chenhui Huang (YellowHCH)

Changes

Example: all the operands of shape.broadcast are empty tensors.

func.func @<!-- -->all_empty(%arg0: tensor&lt;f32&gt;) -&gt; tensor&lt;0xindex&gt; {
  %1 = shape.shape_of %arg0 : tensor&lt;f32&gt; -&gt; tensor&lt;0xindex&gt;
  %2 = shape.const_shape [] : tensor&lt;0xindex&gt;
  %3 = shape.broadcast %1, %2, %1 : tensor&lt;0xindex&gt;, tensor&lt;0xindex&gt;, tensor&lt;0xindex&gt; -&gt; tensor&lt;0xindex&gt;
  return %3 : tensor&lt;0xindex&gt;
}

One can reproduce crash when canonicalize with down-top order, cmd like this:
mlir-opt -split-input-file -allow-unregistered-dialect -canonicalize="test-convergence top-down=0" %s

The root cause is when all operands are empty tensor, RemoveEmptyShapeOperandsPattern would filter out all operands.


Full diff: https://github.com/llvm/llvm-project/pull/118941.diff

2 Files Affected:

  • (modified) mlir/lib/Dialect/Shape/IR/Shape.cpp (+6)
  • (modified) mlir/test/Dialect/Shape/canonicalize.mlir (+16)
diff --git a/mlir/lib/Dialect/Shape/IR/Shape.cpp b/mlir/lib/Dialect/Shape/IR/Shape.cpp
index bebfaa8c1ea822..8779fe837c7ae7 100644
--- a/mlir/lib/Dialect/Shape/IR/Shape.cpp
+++ b/mlir/lib/Dialect/Shape/IR/Shape.cpp
@@ -699,6 +699,12 @@ struct RemoveEmptyShapeOperandsPattern : public OpRewritePattern<OpTy> {
                                                  isPotentiallyNonEmptyShape);
 
     // Reduce op to equivalent without empty shape operands.
+    if (newOperands.empty()) {
+      rewriter.replaceOpWithNewOp<ConstShapeOp>(
+          op, op->getResultTypes().front(), rewriter.getIndexTensorAttr({}));
+      return success();
+    }
+
     if (newOperands.size() < op.getNumOperands()) {
       rewriter.replaceOpWithNewOp<OpTy>(op, op->getResultTypes(), newOperands,
                                         op->getAttrs());
diff --git a/mlir/test/Dialect/Shape/canonicalize.mlir b/mlir/test/Dialect/Shape/canonicalize.mlir
index 5b98a7790debf2..d55e0d8291cfef 100644
--- a/mlir/test/Dialect/Shape/canonicalize.mlir
+++ b/mlir/test/Dialect/Shape/canonicalize.mlir
@@ -1,4 +1,5 @@
 // RUN: mlir-opt -split-input-file -allow-unregistered-dialect -canonicalize="test-convergence" %s | FileCheck %s
+// RUN: mlir-opt -split-input-file -allow-unregistered-dialect -canonicalize="test-convergence top-down=1" %s | FileCheck %s
 
 // CHECK-LABEL: func @f
 func.func @f(%arg0: tensor<2x3x4xf32>) -> tensor<3xindex> {
@@ -134,6 +135,21 @@ func.func @all_but_one_empty(%arg0 : !shape.shape) -> !shape.shape {
 
 // -----
 
+// All operands are known empty shapes.
+// CHECK-LABEL: @all_empty
+// CHECK-SAME:  (%[[ARG_0:.*]]: tensor<f32>, %[[ARG_1:.*]]: tensor<i1>)
+func.func @all_empty(%arg0: tensor<f32>, %arg1: tensor<i1>) -> tensor<0xindex> {
+  // CHECK: %[[CST:.*]] = shape.const_shape [] : tensor<0xindex>
+  // CHECK: return %[[CST]] : tensor<0xindex>
+  %1 = shape.shape_of %arg0 : tensor<f32> -> tensor<0xindex>
+  %2 = shape.shape_of %arg1 : tensor<i1> -> tensor<0xindex>
+  %3 = shape.const_shape [] : tensor<0xindex>
+  %4 = shape.broadcast %1, %2, %3 : tensor<0xindex>, tensor<0xindex>, tensor<0xindex> -> tensor<0xindex>
+  return %4 : tensor<0xindex>
+}
+
+// -----
+
 // Partial folding.
 // CHECK-LABEL: @partial_folding
 // CHECK-SAME:  (%[[ARG:.*]]: !shape.shape)

@@ -699,6 +699,12 @@ struct RemoveEmptyShapeOperandsPattern : public OpRewritePattern<OpTy> {
isPotentiallyNonEmptyShape);

// Reduce op to equivalent without empty shape operands.
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I think this comment is more applicable to the next branch starting from L708?

The new code seems to replace the op with the empty shape operands. The comment can be something like this?

// Replace the op with empty shape constant if all operants are reduced to be empty. 

@@ -1,4 +1,5 @@
// RUN: mlir-opt -split-input-file -allow-unregistered-dialect -canonicalize="test-convergence" %s | FileCheck %s
// RUN: mlir-opt -split-input-file -allow-unregistered-dialect -canonicalize="test-convergence top-down=1" %s | FileCheck %s
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In the original issue, we use top-down=0 to reproduce the case. Is it okay to use top-down=1 instead?

#118941

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It should be top-down=0. Thanks for your reminder.

@YellowHCH YellowHCH force-pushed the fix_shape_canonicalize branch from e124e18 to 0375983 Compare December 13, 2024 02:32
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It looks good to me now. Thanks for updating!

@Lewuathe Lewuathe merged commit 1e18815 into llvm:main Dec 20, 2024
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