https://github.com/usx95 updated
https://github.com/llvm/llvm-project/pull/147315
>From 1ebcbdfa5dae7a9970634e8316f4b8e344312a0e Mon Sep 17 00:00:00 2001
From: Utkarsh Saxena <u...@google.com>
Date: Mon, 7 Jul 2025 15:13:00 +0000
Subject: [PATCH] [LifetimeSafety] Add script performance benchmarking
---
clang/lib/Analysis/LifetimeSafety.cpp | 7 +-
.../Analysis/LifetimeSafety/CMakeLists.txt | 49 +++
.../test/Analysis/LifetimeSafety/benchmark.py | 307 ++++++++++++++++++
.../Analysis/LifetimeSafety/requirements.txt | 2 +
clang/test/CMakeLists.txt | 2 +
5 files changed, 366 insertions(+), 1 deletion(-)
create mode 100644 clang/test/Analysis/LifetimeSafety/CMakeLists.txt
create mode 100644 clang/test/Analysis/LifetimeSafety/benchmark.py
create mode 100644 clang/test/Analysis/LifetimeSafety/requirements.txt
diff --git a/clang/lib/Analysis/LifetimeSafety.cpp
b/clang/lib/Analysis/LifetimeSafety.cpp
index e881e592ef59f..1c83b5051bad1 100644
--- a/clang/lib/Analysis/LifetimeSafety.cpp
+++ b/clang/lib/Analysis/LifetimeSafety.cpp
@@ -151,7 +151,12 @@ class OriginManager {
OriginID get(const ValueDecl &D) {
auto It = DeclToOriginID.find(&D);
- assert(It != DeclToOriginID.end());
+ // TODO: This should be an assert(It != ExprToOriginID.end()). The current
+ // implementation falls back to getOrCreate to avoid crashing on
+ // yet-unhandled pointer expressions, creating an empty origin for them.
+ if (It == DeclToOriginID.end())
+ return getOrCreate(D);
+
return It->second;
}
diff --git a/clang/test/Analysis/LifetimeSafety/CMakeLists.txt
b/clang/test/Analysis/LifetimeSafety/CMakeLists.txt
new file mode 100644
index 0000000000000..ce37a29655668
--- /dev/null
+++ b/clang/test/Analysis/LifetimeSafety/CMakeLists.txt
@@ -0,0 +1,49 @@
+#
=================================================================================
+# Lifetime Analysis Benchmarking Target
+#
=================================================================================
+# This target allows running performance benchmarks for the clang lifetime
analysis
+# using a Python script (with managed dependencies).
+
+find_package(Python3 COMPONENTS Interpreter REQUIRED)
+
+# Define paths for the virtual environment and requirements file.
+set(LIFETIME_BENCHMARK_SCRIPT
+ "${CMAKE_CURRENT_SOURCE_DIR}/benchmark.py")
+set(LIFETIME_BENCHMARK_VENV_DIR "${CMAKE_CURRENT_BINARY_DIR}/benchmark-venv")
+set(LIFETIME_BENCHMARK_REQUIREMENTS
+ "${CMAKE_CURRENT_SOURCE_DIR}/requirements.txt")
+set(LIFETIME_BENCHMARK_OUTPUT_DIR
+ "${CMAKE_CURRENT_BINARY_DIR}/benchmark_results")
+
+
+if(EXISTS ${LIFETIME_BENCHMARK_SCRIPT} AND EXISTS
${LIFETIME_BENCHMARK_REQUIREMENTS})
+
+ # Set up the virtual environment and install packages
+ add_custom_command(
+ OUTPUT ${LIFETIME_BENCHMARK_VENV_DIR}/pyvenv.cfg
+ COMMAND ${Python3_EXECUTABLE} -m venv ${LIFETIME_BENCHMARK_VENV_DIR}
+ COMMAND ${LIFETIME_BENCHMARK_VENV_DIR}/bin/python -m pip install -r
${LIFETIME_BENCHMARK_REQUIREMENTS}
+ DEPENDS ${LIFETIME_BENCHMARK_REQUIREMENTS}
+ COMMENT "Creating Python virtual environment and installing dependencies
for benchmark..."
+ )
+ add_custom_target(benchmark_venv_setup
+ DEPENDS ${LIFETIME_BENCHMARK_VENV_DIR}/pyvenv.cfg
+ )
+
+ # Main benchmark target
+ add_custom_target(benchmark_lifetime_safety_analysis
+ COMMAND ${LIFETIME_BENCHMARK_VENV_DIR}/bin/python
${LIFETIME_BENCHMARK_SCRIPT}
+ --clang-binary ${LLVM_BINARY_DIR}/bin/clang
+ --output-dir ${LIFETIME_BENCHMARK_OUTPUT_DIR}
+
+ DEPENDS clang benchmark_venv_setup
+
+ # Display the output directly in the console.
+ USES_TERMINAL
+
+ COMMENT "Running Lifetime Analysis performance benchmarks..."
+ )
+
+ set_target_properties(benchmark_lifetime_safety_analysis
+ PROPERTIES FOLDER "Clang/Benchmarks")
+endif()
diff --git a/clang/test/Analysis/LifetimeSafety/benchmark.py
b/clang/test/Analysis/LifetimeSafety/benchmark.py
new file mode 100644
index 0000000000000..9d5f36c51b9ee
--- /dev/null
+++ b/clang/test/Analysis/LifetimeSafety/benchmark.py
@@ -0,0 +1,307 @@
+import sys
+import argparse
+import subprocess
+import tempfile
+import json
+import os
+from datetime import datetime
+import numpy as np
+from scipy.optimize import curve_fit
+from scipy.stats import t
+
+
+def generate_cpp_cycle_test(n: int) -> str:
+ """
+ Generates a C++ code snippet with a specified number of pointers in a
cycle.
+ Creates a while loop that rotates N pointers.
+ This pattern tests the convergence speed of the dataflow analysis when
+ reaching its fixed point.
+
+ Example:
+ struct MyObj { int id; ~MyObj() {} };
+
+ void long_cycle_4(bool condition) {
+ MyObj v1{1};
+ MyObj v2{1};
+ MyObj v3{1};
+ MyObj v4{1};
+
+ MyObj* p1 = &v1;
+ MyObj* p2 = &v2;
+ MyObj* p3 = &v3;
+ MyObj* p4 = &v4;
+
+ while (condition) {
+ MyObj* temp = p1;
+ p1 = p2;
+ p2 = p3;
+ p3 = p4;
+ p4 = temp;
+ }
+ }
+ """
+ if n <= 0:
+ return "// Number of variables must be positive."
+
+ cpp_code = "struct MyObj { int id; ~MyObj() {} };\n\n"
+ cpp_code += f"void long_cycle_{n}(bool condition) {{\n"
+ for i in range(1, n + 1):
+ cpp_code += f" MyObj v{i}{{1}};\n"
+ cpp_code += "\n"
+ for i in range(1, n + 1):
+ cpp_code += f" MyObj* p{i} = &v{i};\n"
+
+ cpp_code += "\n while (condition) {\n"
+ if n > 0:
+ cpp_code += f" MyObj* temp = p1;\n"
+ for i in range(1, n):
+ cpp_code += f" p{i} = p{i+1};\n"
+ cpp_code += f" p{n} = temp;\n"
+ cpp_code += " }\n}\n"
+ cpp_code += f"\nint main() {{ long_cycle_{n}(false); return 0; }}\n"
+ return cpp_code
+
+
+def generate_cpp_merge_test(n: int) -> str:
+ """
+ Creates N independent if statements that merge at a single point.
+ This pattern specifically stresses the performance of the
+ 'LifetimeLattice::join' operation.
+
+ Example:
+ struct MyObj { int id; ~MyObj() {} };
+
+ void conditional_merges_4(bool condition) {
+ MyObj v1, v2, v3, v4;
+ MyObj *p1 = nullptr, *p2 = nullptr, *p3 = nullptr, *p4 = nullptr;
+
+ if(condition) { p1 = &v1; }
+ if(condition) { p2 = &v2; }
+ if(condition) { p3 = &v3; }
+ if(condition) { p4 = &v4; }
+ }
+ """
+ if n <= 0:
+ return "// Number of variables must be positive."
+
+ cpp_code = "struct MyObj { int id; ~MyObj() {} };\n\n"
+ cpp_code += f"void conditional_merges_{n}(bool condition) {{\n"
+ decls = [f"v{i}" for i in range(1, n + 1)]
+ cpp_code += f" MyObj {', '.join(decls)};\n"
+ ptr_decls = [f"*p{i} = nullptr" for i in range(1, n + 1)]
+ cpp_code += f" MyObj {', '.join(ptr_decls)};\n\n"
+
+ for i in range(1, n + 1):
+ cpp_code += f" if(condition) {{ p{i} = &v{i}; }}\n"
+
+ cpp_code += "}\n"
+ cpp_code += f"\nint main() {{ conditional_merges_{n}(false); return 0;
}}\n"
+ return cpp_code
+
+
+def analyze_trace_file(trace_path: str) -> tuple[float, float]:
+ """
+ Parses the -ftime-trace JSON output to find durations.
+
+ Returns:
+ A tuple of (lifetime_analysis_duration_us, total_clang_duration_us).
+ """
+ lifetime_duration = 0.0
+ total_duration = 0.0
+ try:
+ with open(trace_path, "r") as f:
+ trace_data = json.load(f)
+ for event in trace_data.get("traceEvents", []):
+ if event.get("name") == "LifetimeSafetyAnalysis":
+ lifetime_duration += float(event.get("dur", 0))
+ if event.get("name") == "ExecuteCompiler":
+ total_duration += float(event.get("dur", 0))
+
+ except (IOError, json.JSONDecodeError) as e:
+ print(f"Error reading or parsing trace file {trace_path}: {e}",
file=sys.stderr)
+ return 0.0, 0.0
+ return lifetime_duration, total_duration
+
+
+def power_law(n, c, k):
+ """Represents the power law function: y = c * n^k"""
+ return c * np.power(n, k)
+
+
+def human_readable_time(ms: float) -> str:
+ """Converts milliseconds to a human-readable string (ms or s)."""
+ if ms >= 1000:
+ return f"{ms / 1000:.2f} s"
+ return f"{ms:.2f} ms"
+
+
+def generate_markdown_report(results: dict) -> str:
+ """Generates a Markdown-formatted report from the benchmark results."""
+ report = []
+ timestamp = datetime.now().strftime("%Y-%m-%d %H:%M:%S %Z")
+ report.append(f"# Lifetime Analysis Performance Report")
+ report.append(f"> Generated on: {timestamp}")
+ report.append("\n---\n")
+
+ for test_name, data in results.items():
+ title = data["title"]
+ report.append(f"## Test Case: {title}")
+ report.append("")
+
+ # Table header
+ report.append("| N | Analysis Time | Total Clang Time |")
+ report.append("|:----|--------------:|-----------------:|")
+
+ # Table rows
+ n_data = np.array(data["n"])
+ analysis_data = np.array(data["lifetime_ms"])
+ total_data = np.array(data["total_ms"])
+ for i in range(len(n_data)):
+ analysis_str = human_readable_time(analysis_data[i])
+ total_str = human_readable_time(total_data[i])
+ report.append(f"| {n_data[i]:<3} | {analysis_str:>13} |
{total_str:>16} |")
+
+ report.append("")
+
+ # Complexity analysis
+ report.append(f"**Complexity Analysis:**")
+ try:
+ # Curve fitting requires at least 3 points
+ if len(n_data) < 3:
+ raise ValueError("Not enough data points to perform curve
fitting.")
+
+ popt, pcov = curve_fit(
+ power_law, n_data, analysis_data, p0=[0, 2], maxfev=5000
+ )
+ _, k = popt
+
+ # Confidence Interval for k
+ alpha = 0.05 # 95% confidence
+ dof = max(0, len(n_data) - len(popt)) # degrees of freedom
+ t_val = t.ppf(1.0 - alpha / 2.0, dof)
+ # Standard error of the parameters
+ perr = np.sqrt(np.diag(pcov))
+ k_stderr = perr[1]
+ k_ci_lower = k - t_val * k_stderr
+ k_ci_upper = k + t_val * k_stderr
+
+ report.append(
+ f"- The performance for this case scales approx. as
**O(n<sup>{k:.2f}</sup>)**."
+ )
+ report.append(
+ f"- **95% Confidence interval for exponent:**
`[{k_ci_lower:.2f}, {k_ci_upper:.2f}]`."
+ )
+
+ except (RuntimeError, ValueError) as e:
+ report.append(f"- Could not determine a best-fit curve for the
data: {e}")
+
+ report.append("\n---\n")
+
+ return "\n".join(report)
+
+
+def run_single_test(
+ clang_binary: str, output_dir: str, test_name: str, generator_func, n: int
+) -> tuple[float, float]:
+ """Generates, compiles, and benchmarks a single test case."""
+ print(f"--- Running Test: {test_name.capitalize()} with N={n} ---")
+
+ generated_code = generator_func(n)
+
+ base_name = f"test_{test_name}_{n}"
+ source_file = os.path.join(output_dir, f"{base_name}.cpp")
+ trace_file = os.path.join(output_dir, f"{base_name}.json")
+
+ with open(source_file, "w") as f:
+ f.write(generated_code)
+
+ clang_command = [
+ clang_binary,
+ "-c",
+ "-o",
+ "/dev/null",
+ "-ftime-trace=" + trace_file,
+ "-Wexperimental-lifetime-safety",
+ "-std=c++17",
+ source_file,
+ ]
+
+ result = subprocess.run(clang_command, capture_output=True, text=True)
+
+ if result.returncode != 0:
+ print(f"Compilation failed for N={n}!", file=sys.stderr)
+ print(result.stderr, file=sys.stderr)
+ return 0.0, 0.0
+
+ lifetime_us, total_us = analyze_trace_file(trace_file)
+
+ return lifetime_us / 1000.0, total_us / 1000.0
+
+
+if __name__ == "__main__":
+ parser = argparse.ArgumentParser(
+ description="Generate, compile, and benchmark C++ test cases for
Clang's lifetime analysis."
+ )
+ parser.add_argument(
+ "--clang-binary", type=str, required=True, help="Path to the Clang
executable."
+ )
+ parser.add_argument(
+ "--output-dir",
+ type=str,
+ default="benchmark_results",
+ help="Directory to save persistent benchmark files. (Default:
./benchmark_results)",
+ )
+
+ args = parser.parse_args()
+
+ os.makedirs(args.output_dir, exist_ok=True)
+ print(f"Benchmark files will be saved in:
{os.path.abspath(args.output_dir)}\n")
+
+ test_configurations = [
+ {
+ "name": "cycle",
+ "title": "Pointer Cycle in Loop",
+ "generator_func": generate_cpp_cycle_test,
+ "n_values": [10, 25, 50, 75, 100, 150],
+ },
+ {
+ "name": "merge",
+ "title": "CFG Merges",
+ "generator_func": generate_cpp_merge_test,
+ "n_values": [10, 50, 100, 200, 400, 800],
+ },
+ ]
+
+ results = {}
+
+ print("Running performance benchmarks...")
+ for config in test_configurations:
+ test_name = config["name"]
+ results[test_name] = {
+ "title": config["title"],
+ "n": [],
+ "lifetime_ms": [],
+ "total_ms": [],
+ }
+ for n in config["n_values"]:
+ lifetime_ms, total_ms = run_single_test(
+ args.clang_binary,
+ args.output_dir,
+ test_name,
+ config["generator_func"],
+ n,
+ )
+ if total_ms > 0:
+ results[test_name]["n"].append(n)
+ results[test_name]["lifetime_ms"].append(lifetime_ms)
+ results[test_name]["total_ms"].append(total_ms)
+ print(
+ f" Total: {human_readable_time(total_ms)} | Analysis:
{human_readable_time(lifetime_ms)}"
+ )
+
+ print("\n\n" + "=" * 80)
+ print("Generating Markdown Report...")
+ print("=" * 80 + "\n")
+
+ markdown_report = generate_markdown_report(results)
+ print(markdown_report)
diff --git a/clang/test/Analysis/LifetimeSafety/requirements.txt
b/clang/test/Analysis/LifetimeSafety/requirements.txt
new file mode 100644
index 0000000000000..6bad10388ecb1
--- /dev/null
+++ b/clang/test/Analysis/LifetimeSafety/requirements.txt
@@ -0,0 +1,2 @@
+numpy
+scipy
diff --git a/clang/test/CMakeLists.txt b/clang/test/CMakeLists.txt
index 416af9ab4d0aa..286c9d40d2dab 100644
--- a/clang/test/CMakeLists.txt
+++ b/clang/test/CMakeLists.txt
@@ -234,3 +234,5 @@ if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/debuginfo-tests)
add_subdirectory(debuginfo-tests)
endif()
endif()
+
+add_subdirectory(Analysis/LifetimeSafety)
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