Shape Inference now succeeds for unimplemented ops (#2200)

Signed-off-by: Alexandre Eichenberger <[email protected]>

src/Dialect/ONNX/ONNXDimAnalysis.cpp

@@ -96,7 +96,8 @@ bool exploreSameInputDims(const onnx_mlir::DimAnalysis::DimT &dim,
   // Get its shape interface.
   onnx_mlir::ONNXOpShapeHelper *shapeHelper =
       shape_op.getShapeHelper(op, {}, nullptr, nullptr);
-  if (!shapeHelper)
+  // If no shape helper, or unimplemented, just abort.
+  if (!shapeHelper || !shapeHelper->isImplemented())
     return false;
 
   // Compute shape.

src/Dialect/ONNX/ONNXOps.cpp

@@ -24,21 +24,12 @@
 // Unsupported Operations
 //===---------------------------------------------------------------------===//
 
-// Operations for which shape inference has not been implemented yet
-// If you add the implementation for one op, move it out of this section
-// Also please add test case in test/mlir/onnx/onnx_shape_inference.mlir
-// Followed by the implementation of lowering to Krnl and
-// Enable the corresponding node test in check-onnx-backend
-
+// Operations for which shape inference has not been implemented.
 #define UNSUPPORTED_OPS(OP_TYPE)                                               \
   /* shape inference interface method */                                       \
   mlir::LogicalResult mlir::OP_TYPE::inferShapes(                              \
       std::function<void(mlir::Region &)> doShapeInference) {                  \
-    return emitOpError(                                                        \
-        "op is not supported at this time. Please open an issue on "           \
-        "https://github.com/onnx/onnx-mlir and/or consider contributing "      \
-        "code. "                                                               \
-        "Error encountered in shape inference.");                              \
+    return mlir::success();                                                    \
   }
 
 #include "src/Dialect/ONNX/ONNXUnsupportedOps.hpp"

src/Dialect/ONNX/ONNXOps/ShapeHelper.hpp

@@ -75,7 +75,8 @@ struct ONNXUnimplementedOpShapeHelper : public ONNXOpShapeHelper {
       : ONNXOpShapeHelper(op, operands, ieBuilder, scope) {}
   virtual ~ONNXUnimplementedOpShapeHelper() {}
 
-  mlir::LogicalResult computeShape() final { return mlir::failure(); }
+  bool isImplemented() override { return false; }
+  mlir::LogicalResult computeShape() final { return mlir::success(); }
 };
 
 // Classes for unsupported ops, including shape inference and shape helpers.

src/Interface/ShapeHelperOpInterface.hpp

@@ -85,9 +85,18 @@ struct ONNXOpShapeHelper {
       IndexExprScope *scope);      /* Install local scope if null. */
   virtual ~ONNXOpShapeHelper();
 
+  // Return true if implemented.
+  virtual bool isImplemented() { return true; }
+
   // Every leaf class is expected to create a computeShape with the following
   // signature. This method is responsible to compute at a minimum the output
   // dims.
+  // Unimplemented operations return success, as these operations may be
+  // transformed later in a sequence of operations with implemented shape
+  // inference. To ensure an implementation, check the `isImplemented` function.
+  // This is used, for example, in dynamic analysis, where unimplemented shape
+  // inferences are simply ignored (and conservatively assume no knowledge about
+  // that operation's transfer function).
   virtual mlir::LogicalResult computeShape() = 0;
 
   // Compute shape and assert on failure.
@@ -105,8 +114,17 @@ struct ONNXOpShapeHelper {
       mlir::ArrayRef<mlir::Attribute> encodingList = {});
 
   // Get output dims for the N-th output dimension as Index Expressions.
-  // Scalar may have a DimsExpr that is empty.
-  DimsExpr &getOutputDims(int n = 0) { return privateOutputsDims[n]; }
+  // Scalar may have a DimsExpr that is empty. Requires an implementation.
+  DimsExpr &getOutputDims(int n = 0) {
+    if (!isImplemented()) {
+      llvm::errs() << "Implementation of shape helper for op " << op->getName()
+                   << "is not currently available; please open an issue on "
+                   << "\"https://github.com/onnx/onnx-mlir/\" and/or consider "
+                   << "contributing code if this op is required.\n";
+      llvm_unreachable("missing implementation for shape inference");
+    }
+    return privateOutputsDims[n];
+  }
   // Set output dims, merging the dims associated with the current type with
   // inferred dims provided here, as appropriate.
   void setOutputDims(

src/Interface/ShapeHelperOpInterface.td

@@ -30,8 +30,11 @@ def ShapeHelperOpInterface : OpInterface<"ShapeHelperOpInterface"> {
 
     For operations that do not support shape helpers at this stage, a
     `ONNXUnimplementedOpShapeHelper` object is returned. This object does not
-    compute shapes, and simply return failure when `computeShape` is called
-    on it.
+    compute shapes, and simply return success when `computeShape` is called
+    on it. Users may verify if an operation has an actual implementation by
+    calling `isImplemented()` on the shape helper object. An implementation
+    is required when attempting to read the outputs of a shape helper object
+    via the `getOutputDims` method.
 
     The new object is allocated on the heap and it is the responsability
     of the object user to free the memory after last use.

test/mlir/onnx/onnx_shape_inference.mlir

@@ -3547,3 +3547,25 @@ module {
 // CHECK:         }
   }
 }
+
+// -----
+
+// Check that ClipV6 operation shape inference goes through shape inference smoothly.
+// ClipV6 has no shape inference as it is supposed to be first updated to the latest ClipOp.
+// Using the latest shape inference, the default is to let unimplemented ops go through shape
+// inference without asserts/failures. Asserts only occurs when the results of the shape
+// inference is used.
+// The output shoudl be the same as the input, as no shape inference is expected to be performed.
+
+func.func @test_clipv6(%arg0: tensor<*xf32>) {
+  %0 = "onnx.ClipV6"(%arg0) {max = 6.000000e+00 : f32, min = 0.000000e+00 : f32} : (tensor<*xf32>) -> tensor<*xf32>
+  return
+
+// mlir2FileCheck.py
+// CHECK-LABEL:  func.func @test_clipv6
+// CHECK-SAME:   ([[PARAM_0_:%.+]]: tensor<*xf32>) {
+// CHECK:           [[VAR_0_:%.+]] = "onnx.ClipV6"([[PARAM_0_]]) {max = 6.000000e+00 : f32, min = 0.000000e+00 : f32} : (tensor<*xf32>) -> tensor<*xf32>
+// CHECK:           return
+// CHECK:         }
+}
+