[MLIR] Add LocationAttr to the Python API

[youngar]

Summary

This is a follow up to D142182, to expose LocationAttrs through Python.

[ftynse]

mlir/lib/Bindings/Python/IRCore.cpp

2561–2566

Any reason why this is not a property?

[youngar]

• Change get_attr to a property attr
• Use the actual c-api functions, s/Attr/Attribute

[youngar]

mlir/lib/Bindings/Python/IRCore.cpp

2561–2566

Updated this to be a property named "attr". I was not sure if I should name it "attribute" or "attr", but the closest I see that NamedAttribute has "attr".

mlir/lib/Bindings/Python/IRCore.cpp

py::class_<PyLocation>(m, "Location", py::module_local())
                 context->getRef(),
                 mlirLocationNameGet(
                     context->get(), toMlirStringRef(name),
                     childLoc ? childLoc->get()
                              : mlirLocationUnknownGet(context->get())));
           },
           py::arg("name"), py::arg("childLoc") = py::none(),
           py::arg("context") = py::none(), kContextGetNameLocationDocString)
+      .def_static(
+          "from_attr",
+          [](PyAttribute &attribute, DefaultingPyMlirContext context) {
+            return PyLocation(context->getRef(),
+                              mlirLocationFromAttribute(attribute));
+          },
+          py::arg("attribute"), py::arg("context") = py::none(),
+          "Gets a Location from a LocationAttr")
       .def_property_readonly(
           "context",
           [](PyLocation &self) { return self.getContext().getObject(); },
           "Context that owns the Location")
+      .def_property_readonly(
+          "attr",
+          [](PyLocation &self) {
+            return PyAttribute(self.getContext(),
+                               mlirLocationGetAttribute(self));
+          },
+          "Get the underlying LocationAttr")
       .def(
           "emit_error",
           [](PyLocation &self, std::string message) {
             mlirEmitError(self, message.c_str());
           },
           py::arg("message"), "Emits an error at this location")
       .def("__repr__", [](PyLocation &self) {
         PyPrintAccumulator printAccum;

mlir/test/python/ir/location.py

def testUnknown():
   # CHECK: unknown str: loc(unknown)
   print("unknown str:", str(loc))
   # CHECK: unknown repr: loc(unknown)
   print("unknown repr:", repr(loc))
 
 run(testUnknown)
 
 
+# CHECK-LABEL: TEST: testLocationAttr
+def testLocationAttr():
+  with Context() as ctxt:
+    loc = Location.unknown()
+    attr = loc.get_attr()
+    clone = Location.from_attr(attr)
+  gc.collect()
+  # CHECK: loc: loc(unknown)
+  print("loc:", str(loc))
+  # CHECK: clone: loc(unknown)
+  print("clone:", str(clone))
+  assert loc == clone
+
+run(testLocationAttr)
+
 # CHECK-LABEL: TEST: testFileLineCol
 def testFileLineCol():
   with Context() as ctx:
     loc = Location.file("foo.txt", 123, 56)
   ctx = None
   gc.collect()
   # CHECK: file str: loc("foo.txt":123:56)
   print("file str:", str(loc))