feat(aten::__range_length): Adding range length evaluator

Signed-off-by: Naren Dasan <[email protected]>
Signed-off-by: Naren Dasan <[email protected]>

Author: narendasan

Diff for: core/conversion/evaluators/aten.cpp

@@ -718,7 +718,25 @@ auto aten_registrations TORCHTRT_UNUSED =
                       torch::jit::pop(stack, output);
                       return output;
                     },
-                    EvalOptions().validSchemas({"aten::format(str self, ...) -> (str)"})});
+                    EvalOptions().validSchemas({"aten::format(str self, ...) -> (str)"})})
+        .evaluator({c10::Symbol::fromQualString("aten::__range_length"),
+                    [](const torch::jit::Node* n, kwargs& args) -> c10::optional<torch::jit::IValue> {
+                      auto lo = args.at(n->input(0)).unwrapToInt();
+                      auto hi = args.at(n->input(1)).unwrapToInt();
+                      auto step = args.at(n->input(2)).unwrapToInt();
+
+                      if (step == 0) {
+                        TORCHTRT_THROW_ERROR("aten::__range_length() arg 3 must not be zero");
+                      }
+                      if (step > 0 && lo < hi) {
+                        return 1 + (hi - 1 - lo) / step;
+                      } else if (step < 0 && lo > hi) {
+                        return 1 + (lo - 1 - hi) / (0 - step);
+                      } else {
+                        return 0;
+                      }
+                    },
+                    EvalOptions().validSchemas({"aten::__range_length(int lo, int hi, int step) -> int"})});
 } // namespace
 } // namespace evaluators
 } // namespace conversion

Diff for: tests/core/conversion/evaluators/test_aten_evaluators.cpp

@@ -665,4 +665,40 @@ TEST(Evaluators, AtenFormatRaiseExceptionEvaluatesCorrectly) {
   } else {
     ASSERT_TRUE(false);
   }
+}
+
+TEST(Evaluators, RangeLengthEvaluatesCorrectly) {
+  const auto graph = R"IR(
+      graph():
+        %1 : int = prim::Constant[value=1]()
+        %2 : int = prim::Constant[value=10]()
+        %3 : int = prim::Constant[value=2]()
+        %4 : int = aten::__range_length(%1, %2, %3)
+        return (%3))IR";
+
+  auto g = std::make_shared<torch::jit::Graph>();
+  torch::jit::parseIR(graph, g.get());
+
+  auto jit_results = torch_tensorrt::tests::util::EvaluateGraphJIT(g, {});
+  auto trt_results = torch_tensorrt::tests::util::EvaluateGraph(g->block(), {});
+
+  ASSERT_TRUE(jit_results[0] == trt_results[0]);
+}
+
+TEST(Evaluators, RangeLengthNegEvaluatesCorrectly) {
+  const auto graph = R"IR(
+      graph():
+        %1 : int = prim::Constant[value=10]()
+        %2 : int = prim::Constant[value=1]()
+        %3 : int = prim::Constant[value=-2]()
+        %4 : int = aten::__range_length(%1, %2, %3)
+        return (%3))IR";
+
+  auto g = std::make_shared<torch::jit::Graph>();
+  torch::jit::parseIR(graph, g.get());
+
+  auto jit_results = torch_tensorrt::tests::util::EvaluateGraphJIT(g, {});
+  auto trt_results = torch_tensorrt::tests::util::EvaluateGraph(g->block(), {});
+
+  ASSERT_TRUE(jit_results[0] == trt_results[0]);
 }