Add benchmarking support for pointer nullability analysis.

This change includes somewhat arbitrary functions as benchmarks. Most are synthetic, with two derived from a real example. We need to grow these into a more principled sets of benchmark functions.

PiperOrigin-RevId: 579872437
Change-Id: Iffc02c0dc2805015d11d847ebc9eb422eea2139e
diff --git a/nullability/BUILD b/nullability/BUILD
index 316833b..5c62ecf 100644
--- a/nullability/BUILD
+++ b/nullability/BUILD
@@ -186,3 +186,21 @@
         "@llvm-project//third-party/unittest:gmock",
     ],
 )
+
+cc_test(
+    name = "pointer_nullability_analysis_benchmark",
+    srcs = ["pointer_nullability_analysis_benchmark.cc"],
+    tags = ["benchmark"],
+    deps = [
+        ":pointer_nullability_analysis",
+        ":pointer_nullability_diagnosis",
+        "@absl//absl/log:check",
+        "@absl//absl/strings",
+        "@absl//absl/strings:string_view",
+        "@com_google_googletest//:gtest_main",
+        "@llvm-project//clang:analysis",
+        "@llvm-project//clang:ast",
+        "@llvm-project//clang:basic",
+        "@llvm-project//clang:testing",
+    ],
+)