Add implicit constant capture.

We want more sophisticated capture later, but this allows basics to function.

python/npcomp/tracing/mlir_trace.py

@@ -51,6 +51,7 @@ class FunctionTracer(TraceContext):
       "_python_args",
       "_result_array_params",
       "_traced_arrays",
+      "_external_arrays",
   ]
 
   def __init__(self, module_builder: ModuleBuilder, epf: ExportPyFunction):
@@ -58,6 +59,7 @@ class FunctionTracer(TraceContext):
     self.module_builder = module_builder
     self.epf = epf
     self._traced_arrays = {}  # Mapping of TracedArray to current consumer value
+    self._external_arrays = {}  # Mapping of id to (ndarray, ir.Value)
     self._validate()
 
     # Alias some parent members for convenience.
@@ -106,11 +108,29 @@ class FunctionTracer(TraceContext):
     self._traced_arrays[traced_array] = value
 
   def get_traced_array_value(self, traced_array):
+    if not isinstance(traced_array, TracedArray):
+      # Generic import of external value. For now, we just treat these as
+      # local consts.
+      return self._get_external_array_value(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 _get_external_array_value(self, external_array):
+    h = self._helper
+    if not isinstance(external_array, np.ndarray):
+      raise TracingError("Expected ndarray but got: %r" % (external_array,))
+    found_it = self._external_arrays.get(id(external_array))
+    if found_it:
+      return found_it[1]
+    # Import it.
+    dense_attr = h.context.dense_elements_attr(external_array)
+    const_value = h.constant_op(dense_attr.type, dense_attr).result
+    self._external_arrays[id(external_array)] = (external_array, const_value)
+    return const_value
+
   def _validate(self):
     if not all(
         arg.type_class == TypeClass.NdArray for arg in self.epf.sig.args):
@@ -212,12 +232,14 @@ class FunctionTracer(TraceContext):
 
   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
+                             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)
@@ -230,8 +252,8 @@ class FunctionTracer(TraceContext):
     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_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

python/samples/const.py

@@ -0,0 +1,21 @@
+#  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 *
+
+weights = np.random.uniform(size=(16, 4)).astype(np.float32)
+bias = np.random.uniform(size=(4,)).astype(np.float32)
+
+def constants(a: np.ndarray) -> np.ndarray:
+  return np.dot(a, weights) + bias
+
+# TODO: Implement subclassing and deriving constraints by run
+exp = npc.Exporter()
+exp.constants = constants
+
+mb = npc.tracing.ModuleBuilder()
+mb.trace(exp.constants)
+print(mb.module.to_asm())

python_native/MlirIr.cpp

@@ -767,6 +767,9 @@ void PyValue::bind(py::module m) {
 
 void PyAttribute::bind(py::module m) {
   py::class_<PyAttribute>(m, "Attribute")
+      .def_property_readonly("type", [](PyAttribute &self) -> PyType {
+        return self.attr.getType();
+      })
       .def("__repr__", [](PyAttribute &self) {
         std::string res;
         llvm::raw_string_ostream os(res);