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

1 files changed, 52 insertions, 0 deletions

diff --git a/mlir/test/Analysis/test-callgraph.mlir b/mlir/test/Analysis/test-callgraph.mlir
new file mode 100644
index 00000000000..39e4fb8ba27
--- /dev/null
+++ b/mlir/test/Analysis/test-callgraph.mlir
@@ -0,0 +1,52 @@
+// RUN: mlir-opt %s -test-print-callgraph 2>&1 | FileCheck %s --dump-input-on-failure
+
+// CHECK-LABEL: Testing : "simple"
+module attributes {test.name = "simple"} {
+
+  // CHECK: Node{{.*}}func_a
+  func @func_a() {
+    return
+  }
+
+  func @func_b()
+
+  // CHECK: Node{{.*}}func_c
+  // CHECK-NEXT: Call-Edge{{.*}}External-Node
+  func @func_c() {
+    call @func_b() : () -> ()
+    return
+  }
+
+  // CHECK: Node{{.*}}func_d
+  // CHECK-NEXT: Call-Edge{{.*}}func_c
+  func @func_d() {
+    call @func_c() : () -> ()
+    return
+  }
+
+  // CHECK: Node{{.*}}func_e
+  // CHECK-DAG: Call-Edge{{.*}}func_c
+  // CHECK-DAG: Call-Edge{{.*}}func_d
+  // CHECK-DAG: Call-Edge{{.*}}func_e
+  func @func_e() {
+    call @func_c() : () -> ()
+    call @func_d() : () -> ()
+    call @func_e() : () -> ()
+    return
+  }
+
+  // CHECK: Node{{.*}}func_f
+  // CHECK: Child-Edge{{.*}}test.functional_region_op
+  // CHECK: Call-Edge{{.*}}test.functional_region_op
+  func @func_f() {
+    // CHECK: Node{{.*}}test.functional_region_op
+    // CHECK: Call-Edge{{.*}}func_f
+    %fn = "test.functional_region_op"() ({
+      call @func_f() : () -> ()
+      "test.return"() : () -> ()
+    }) : () -> (() -> ())
+
+    call_indirect %fn() : () -> ()
+    return
+  }
+}