[llvm] [mlgo] Support composite AOT-ed models (PR #96276)

[Simon Pilgrim via llvm-commits]

================
@@ -129,6 +192,56 @@ TEST(ReleaseModeRunner, ExtraFeaturesOutOfOrder) {
   EXPECT_EQ(*Evaluator->getTensor<int64_t>(2), -3);
 }
 
+// We expect an error to be reported early if the user tried to specify a model
+// selector, but the model in fact doesn't support that.
+TEST(ReleaseModelRunner, ModelSelectorNoInputFeaturePresent) {
+  LLVMContext Ctx;
+  std::vector<TensorSpec> Inputs{TensorSpec::createSpec<int64_t>("a", {1}),
+                                 TensorSpec::createSpec<int64_t>("b", {1})};
+  EXPECT_DEATH(std::make_unique<ReleaseModeModelRunner<AdditionAOTModel>>(
+                   Ctx, Inputs, "", makeOptions().setModelSelector(M2Selector)),
+               "A model selector was specified but the underlying model does "
+               "not expose a _model_selector input");
+}
+
+TEST(ReleaseModelRunner, ModelSelectorNoSelectorGiven) {
+  LLVMContext Ctx;
+  std::vector<TensorSpec> Inputs{TensorSpec::createSpec<int64_t>("a", {1}),
+                                 TensorSpec::createSpec<int64_t>("b", {1})};
+  EXPECT_DEATH(
+      std::make_unique<ReleaseModeModelRunner<ComposedAOTModel>>(
+          Ctx, Inputs, "", makeOptions()),
+      "A model selector was not specified but the underlying model requires "
+      "selecting one because it exposes a _model_selector input");
----------------
RKSimon wrote:

@mtrofin I'm getting build warnings on MSVC due to these EXPECT_DEATH with make_unique calls - anyway that you can refactor to avoid them please?
```
E:\llvm\llvm-project\llvm\unittests\Analysis\MLModelRunnerTest.cpp(201): warning C4858: discarding return value: This function constructs an object wrapped by a smart pointer and has no other effects; it is not useful to call this function and discard the return value. 
```

https://github.com/llvm/llvm-project/pull/96276