Add initial callgraph support.

Using the two call interfaces, CallOpInterface and CallableOpInterface, this change adds support for an initial multi-level CallGraph. This call graph builds a set of nodes for each callable region, and connects them via edges. An edge may be any of the following types:
* Abstract
  - An edge not produced by a call operation, used for connecting to internal nodes from external nodes.
* Call
  - A call edge is an edge defined via a call-like operation.
* Child
  - This is an artificial edge connecting nested callgraph nodes.

This callgraph will be used, and improved upon, to begin supporting more interesting interprocedural analyses and transformation. In a followup, this callgraph will be used to support more complex inlining support.

PiperOrigin-RevId: 270724968

2 files changed, 40 insertions, 0 deletions

diff --git a/mlir/test/lib/Transforms/CMakeLists.txt b/mlir/test/lib/Transforms/CMakeLists.txt
index 275283b2c18..a475526978b 100644
--- a/mlir/test/lib/Transforms/CMakeLists.txt
+++ b/mlir/test/lib/Transforms/CMakeLists.txt
@@ -1,4 +1,5 @@
 add_llvm_library(MLIRTestTransforms
+  TestCallGraph.cpp
   TestConstantFold.cpp
   TestLoopFusion.cpp
   TestInlining.cpp
diff --git a/mlir/test/lib/Transforms/TestCallGraph.cpp b/mlir/test/lib/Transforms/TestCallGraph.cpp
new file mode 100644
index 00000000000..debf5e77645
--- /dev/null
+++ b/mlir/test/lib/Transforms/TestCallGraph.cpp
@@ -0,0 +1,39 @@
+//===- TestCallGraph.cpp - Test callgraph construction and iteration ------===//
+//
+// Copyright 2019 The MLIR Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// =============================================================================
+//
+// This file contains test passes for constructing and iterating over a
+// callgraph.
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Analysis/CallGraph.h"
+#include "mlir/Pass/Pass.h"
+
+using namespace mlir;
+
+namespace {
+struct TestCallGraphPass : public ModulePass<TestCallGraphPass> {
+  void runOnModule() {
+    llvm::errs() << "Testing : " << getModule().getAttr("test.name") << "\n";
+    getAnalysis<CallGraph>().print(llvm::errs());
+  }
+};
+} // end anonymous namespace
+
+static PassRegistration<TestCallGraphPass>
+    pass("test-print-callgraph",
+         "Print the contents of a constructed callgraph.");