Add numpy.get_slice op and wire it up to the tracer.

include/npcomp/Dialect/Basicpy/BasicpyDialect.h

@@ -72,6 +72,12 @@ public:
   StringAttr getClassName();
   unsigned getSlotCount();
   ArrayRef<Type> getSlotTypes();
+
+  // Shorthand to check whether the SlotObject is of a given className and
+  // arity.
+  bool isOfClassArity(StringRef className, int arity) {
+    return getClassName().getValue() == className && getSlotCount() == arity;
+  }
 };
 
 #include "npcomp/Dialect/Basicpy/BasicpyOpsDialect.h.inc"

include/npcomp/Dialect/Basicpy/BasicpyDialect.td

@@ -73,4 +73,19 @@ def Basicpy_SingletonType : AnyTypeOf<[
   Basicpy_EllipsisType
 ]>;
 
+// A predicate to determine whether a Type is a SlotObject of a given
+// className and arity. Does no checking of slot types.
+class Basicpy_SlotObjectOfClassArity<string className, int arity> :
+  And<[
+    Basicpy_SlotObjectType.predicate,
+    CPred<
+      "$_self.cast<::mlir::NPCOMP::Basicpy::SlotObjectType>().isOfClassArity(\""
+      # className # "\", " # arity # ")">
+  ]>;
+
+// Type representing a 'slice' object, which mirrors the Python built-in
+// slice class.
+def Basicpy_SliceSlotObjectType : 
+  Type<Basicpy_SlotObjectOfClassArity<"slice", 3>>;
+
 #endif // NPCOMP_DIALECT_BASICPY_BASICPY_DIALECT

include/npcomp/Dialect/Numpy/NumpyDialect.td

@@ -10,6 +10,7 @@
 #define NPCOMP_DIALECT_NUMPY_NUMPY_DIALECT
 
 include "mlir/IR/OpBase.td"
+include "npcomp/Dialect/Basicpy/BasicpyDialect.td"
 
 //===----------------------------------------------------------------------===//
 // Dialect definition
@@ -50,6 +51,25 @@ def Numpy_AnyDtype : DialectType<Numpy_Dialect,
 // Type predicates
 //===----------------------------------------------------------------------===//
 
+// Any type, at any stage of analysis that can represent a numpy array.
 def Numpy_AnyArray : TensorOf<[AnyType]>;
 
+def Numpy_SliceTupleElement : AnyTypeOf<[
+  // Supports both "Index Arrays" and "Boolean mask index arrays".
+  Numpy_AnyArray,
+  
+  // Indicates that an axis should be added (np.newaxis == None).
+  Basicpy_NoneType,
+
+  // Indicates that intervening axes should be preserved.
+  Basicpy_EllipsisType,
+
+  // A discrete numeric index (represented as IndexType so that a proper
+  // width can be target dependent).
+  Index,
+
+  // A generalized slice object.
+  Basicpy_SliceSlotObjectType,
+], "types that are legal elements of a __getitem__ tuple operating on arrays">;
+
 #endif // NPCOMP_DIALECT_NUMPY_NUMPY_DIALECT

include/npcomp/Dialect/Numpy/NumpyOps.td

@@ -150,4 +150,39 @@ def Numpy_TransposeOp : Numpy_Op<"transpose", []> {
   }];  
 }
 
+//----------------------------------------------------------------------------//
+// Slicing
+// See: https://docs.scipy.org/doc/numpy/user/basics.indexing.html
+//----------------------------------------------------------------------------//
+
+def Numpy_GetSlice : Numpy_Op<"get_slice", []> {
+  let summary = "Gets a slice of an array";
+  let description = [{
+    This op encapsulates all forms of indexing into an array by taking a
+    variable number of `slice` arguments, each of which represents a single
+    entry in a generalized indexing-tuple. Once full type inference has
+    been performed, there should be sufficient static information to determine
+    the exact slice semantics solely by the signature of types of the `slice`
+    arguments.
+
+    Note that there is a more general form of this op that is generally
+    needed for AST extraction that takes a variable length `tuple` instead
+    of a static list of arguments. It is expected that during type refinement
+    most such uses should degenerate to this static variant.
+
+    Per numpy semantics, many forms of slice return a view instead of a copy,
+    and determining the exact form requires additional analysis.
+  }];
+  let arguments = (ins
+    Numpy_AnyArray:$a,
+    Variadic<Numpy_SliceTupleElement>:$slice_elements
+  );
+  let results = (outs
+    Numpy_AnyArray:$result
+  );
+  let assemblyFormat = [{
+    operands attr-dict `:` functional-type(operands, $result)
+  }];  
+}
+
 #endif // NPCOMP_DIALECT_NUMPY_NUMPY_OPS

lib/Dialect/Numpy/NumpyOps.cpp

@@ -10,6 +10,7 @@
 #include "mlir/IR/Builders.h"
 #include "mlir/IR/FunctionImplementation.h"
 #include "mlir/IR/OpImplementation.h"
+#include "npcomp/Dialect/Basicpy/BasicpyDialect.h"
 #include "npcomp/Dialect/Numpy/NumpyDialect.h"
 
 namespace mlir {

python/npcomp/dialect/Numpy.py

@@ -49,24 +49,30 @@ class DialectHelper(Basicpy.DialectHelper):
     tensor<*xf32>
     >>> t.function_type([t.i32_type], [t.f32_type])
     (i32) -> f32
+    >>> t.unknown_array_type
+    tensor<*x!numpy.any_dtype>
 
   """
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self.numpy_any_dtype = self.context.parse_type("!numpy.any_dtype")
+        self.unknown_array_type = self.tensor_type(self.numpy_any_dtype)
 
     def numpy_ufunc_call_op(self, callee_symbol, result_type, *args):
         """Creates a numpy.ufunc_call op."""
         c = self.context
-    attrs = c.dictionary_attr({
+        attrs = c.dictionary_attr(
-      "ufunc_ref": c.flat_symbol_ref_attr(callee_symbol)
+            {"ufunc_ref": c.flat_symbol_ref_attr(callee_symbol)})
-    })
         return self.op("numpy.ufunc_call", [result_type], args, attrs)
 
     def numpy_narrow_op(self, result_type, operand):
         """Creates a numpy.narrow op."""
         return self.op("numpy.narrow", [result_type], [operand])
 
+    def numpy_get_slice_op(self, result_type, array, *slice_elements):
+        return self.op("numpy.get_slice", [result_type],
+                       [array] + list(slice_elements))
+
 
 def load_builtin_module(context=None):
     """Loads a module populated with numpy built-ins.
@@ -79,7 +85,7 @@ def load_builtin_module(context=None):
     >>> op.is_registered
     True
     >>> op.name
-    'numpy.generic_ufunc'
+    'numpy.builtin_ufunc'
 
   Args:
     context: The MLIRContext to use (None to create a new one).

python/npcomp/tracing/context.py

@@ -58,6 +58,10 @@ class TraceContext:
     self._next_id = 1
     self.active = False
 
+  def _handle_array_getitem(self, array, key):
+    """Handles a call to __getitem__ on a traced array."""
+    raise NotImplementedError("Array slicing not implemented")
+
   def _handle_ufunc(self, ufunc, method, inputs, kwargs):
     """Handles a ufunc invocation involving at least one TracedArray."""
     return NotImplemented
@@ -144,6 +148,11 @@ class TracedArray(np.lib.mixins.NDArrayOperatorsMixin):
   def __repr__(self):
     return "<TracedArray %d>" % self._uid
 
+  def __getitem__(self, key):
+    tc = self._tc
+    _assert_active(tc)
+    return tc._handle_array_getitem(self, key)
+
   def __array_ufunc__(self, ufunc, method, *inputs, **kwargs):
     tc = self._tc
     _assert_active(tc)

python/npcomp/tracing/mlir_trace.py

@@ -95,8 +95,6 @@ class FunctionTracer(TraceContext):
     return_operands = []
     for py_result, mlir_result_type in zip(py_results, self._f_types):
       mlir_result = self.get_traced_array_value(py_result)
-      if mlir_result is None:
-        raise TracingError("Unregistered traced array: %r", (py_result,))
       # narrow to declared result type.
       return_operands.extend(
           h.numpy_narrow_op(mlir_result_type, mlir_result).results)
@@ -108,7 +106,10 @@ class FunctionTracer(TraceContext):
     self._traced_arrays[traced_array] = value
 
   def get_traced_array_value(self, traced_array):
-    return self._traced_arrays.get(traced_array)
+    traced_value = self._traced_arrays.get(traced_array)
+    if traced_value is None:
+      raise TracingError("Unregistered traced array: %r", (traced_array,))
+    return traced_value
 
   def _validate(self):
     if not all(
@@ -150,9 +151,6 @@ class FunctionTracer(TraceContext):
       assert tv.type == TraceValueType.NDARRAY, (
           "Unsupported TraceValueType: %r" % tv.type)
       ssa_value = self.get_traced_array_value(tv.value)
-      if ssa_value is None:
-        raise TracingError(
-            "Required a traced python NDARRAY but not found: %r" % (tv,))
       ssa_values.append(ssa_value)
     return ssa_values
 
@@ -196,6 +194,48 @@ class FunctionTracer(TraceContext):
     invocation = TraceInvocation(inputs, kwargs, Protocol.ARRAY_FUNC)
     return self._emit_invocation(emitter, invocation)
 
+  def _emit_slice_value(self, slice_element):
+    h = self._helper
+    if slice_element == None:
+      return h.basicpy_singleton_op(h.basicpy_NoneType).result
+    elif slice_element == Ellipsis:
+      return h.basicpy_singleton_op(h.basicpy_EllipsisType).result
+    elif isinstance(slice_element, int):
+      return h.constant_op(h.index_type,
+                           h.context.index_attr(slice_element)).result
+    elif isinstance(slice_element, slice):
+      return self._emit_slice_object(slice_element)
+    else:
+      # Assume array convertible.
+      raise NotImplementedError(
+          "TODO: Slicing with generic arrays not yet implemented")
+
+  def _emit_slice_object(self, slice_object: slice):
+    h = self._helper
+    def emit_index(index):
+      if index is None:
+        return h.basicpy_singleton_op(h.basicpy_NoneType).result
+      else:
+        return h.constant_op(h.index_type,
+                            h.context.index_attr(int(index))).result
+    start = emit_index(slice_object.start)
+    stop = emit_index(slice_object.stop)
+    step = emit_index(slice_object.step)
+    return h.basicpy_slot_object_make_op("slice", start, stop, step).result
+
+  def _handle_array_getitem(self, array, key):
+    h = self._helper
+    array_value = self.get_traced_array_value(array)
+    # Array slicing is always based on a tuple.
+    slice_tuple = key if isinstance(key, tuple) else (key,)
+    # Resolve and emit each slice element.
+    slice_values = [self._emit_slice_value(elt) for elt in slice_tuple]
+    result_value = h.numpy_get_slice_op(
+      h.unknown_array_type, array_value, *slice_values).result
+    result_array = TracedArray(self)
+    self.set_traced_array(result_array, result_value)
+    return result_array
+
 
 if __name__ == "__main__":
   import doctest

python/samples/slice.py

@@ -0,0 +1,18 @@
+#  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
+
+import numpy as np
+import npcomp as npc
+from npcomp.types import *
+
+def slice_array1(a: np.ndarray) -> np.ndarray:
+  return a[1, 2:10:2, 3:4, ..., :, 0]
+
+# TODO: Implement subclassing and deriving constraints by run
+exp = npc.Exporter()
+exp.slice_array1 = slice_array1
+
+mb = npc.tracing.ModuleBuilder()
+mb.trace(exp.slice_array1)
+print(mb.module.to_asm())

python_native/MlirIr.cpp

@@ -195,60 +195,71 @@ void PyDialectHelper::bind(py::module m) {
                                             pyOperands.end());
              return PyOperationRef(opBuilder.create<ReturnOp>(loc, operands));
            })
+      .def("constant_op",
+           [](PyDialectHelper &self, PyType type, PyAttribute value) {
+             OpBuilder &opBuilder = self.pyOpBuilder.getBuilder(true);
+             Location loc = UnknownLoc::get(opBuilder.getContext());
+             return PyOperationRef(
+                 opBuilder.create<ConstantOp>(loc, type.type, value.attr));
+           })
 
       // Types.
+      .def_property_readonly("index_type",
+                             [](PyDialectHelper &self) -> PyType {
+                               return IndexType::get(&self.context->context);
+                             })
       .def("integer_type",
-           [](PyDialectHelper &self, unsigned width) {
+           [](PyDialectHelper &self, unsigned width) -> PyType {
-             return PyType(IntegerType::get(width, &self.context->context));
+             return IntegerType::get(width, &self.context->context);
            },
            py::arg("width") = 32)
       .def_property_readonly("i1_type",
-                             [](PyDialectHelper &self) {
+                             [](PyDialectHelper &self) -> PyType {
-                               return PyType(
+                               return IntegerType::get(1,
-                                   IntegerType::get(1, &self.context->context));
+                                                       &self.context->context);
                              })
-      .def_property_readonly(
+      .def_property_readonly("i16_type",
-          "i16_type",
+                             [](PyDialectHelper &self) -> PyType {
-          [](PyDialectHelper &self) {
+                               return IntegerType::get(32,
-            return PyType(IntegerType::get(32, &self.context->context));
+                                                       &self.context->context);
                              })
-      .def_property_readonly(
+      .def_property_readonly("i32_type",
-          "i32_type",
+                             [](PyDialectHelper &self) -> PyType {
-          [](PyDialectHelper &self) {
+                               return IntegerType::get(32,
-            return PyType(IntegerType::get(32, &self.context->context));
+                                                       &self.context->context);
                              })
-      .def_property_readonly(
+      .def_property_readonly("i64_type",
-          "i64_type",
+                             [](PyDialectHelper &self) -> PyType {
-          [](PyDialectHelper &self) {
+                               return IntegerType::get(64,
-            return PyType(IntegerType::get(64, &self.context->context));
+                                                       &self.context->context);
                              })
       .def_property_readonly("f32_type",
-                             [](PyDialectHelper &self) {
+                             [](PyDialectHelper &self) -> PyType {
-                               return PyType(FloatType::get(
+                               return FloatType::get(StandardTypes::F32,
-                                   StandardTypes::F32, &self.context->context));
+                                                     &self.context->context);
                              })
       .def_property_readonly("f64_type",
-                             [](PyDialectHelper &self) {
+                             [](PyDialectHelper &self) -> PyType {
-                               return PyType(FloatType::get(
+                               return FloatType::get(StandardTypes::F64,
-                                   StandardTypes::F64, &self.context->context));
+                                                     &self.context->context);
                              })
       .def("tensor_type",
            [](PyDialectHelper &self, PyType elementType,
-              llvm::Optional<std::vector<int64_t>> shape) {
+              llvm::Optional<std::vector<int64_t>> shape) -> PyType {
              if (!elementType.type) {
                throw py::raiseValueError("Null element type");
              }
              if (shape) {
-               return PyType(RankedTensorType::get(*shape, elementType.type));
+               return RankedTensorType::get(*shape, elementType.type);
              } else {
-               return PyType(UnrankedTensorType::get(elementType.type));
+               return UnrankedTensorType::get(elementType.type);
              }
            },
            py::arg("element_type"),
            py::arg("shape") = llvm::Optional<std::vector<int64_t>>())
       .def("function_type",
            [](PyDialectHelper &self, std::vector<PyType> inputs,
-              std::vector<PyType> results) {
+              std::vector<PyType> results) -> PyType {
              llvm::SmallVector<Type, 4> inputTypes;
              llvm::SmallVector<Type, 1> resultTypes;
              for (auto input : inputs) {
@@ -257,8 +268,8 @@ void PyDialectHelper::bind(py::module m) {
              for (auto result : results) {
                resultTypes.push_back(result.type);
              }
-             return PyType(FunctionType::get(inputTypes, resultTypes,
+             return FunctionType::get(inputTypes, resultTypes,
-                                             &self.context->context));
+                                      &self.context->context);
            });
 }
 
@@ -326,6 +337,10 @@ void PyContext::bind(py::module m) {
              }
              return PyType(t);
            })
+      .def("index_attr",
+           [](PyContext &self, int64_t indexValue) -> PyAttribute {
+             return IntegerAttr::get(IndexType::get(&self.context), indexValue);
+           })
       .def("string_attr",
            [](PyContext &self, const std::string &s) -> PyAttribute {
              return StringAttr::get(s, &self.context);