[𝘀𝗽𝗿] initial version

Created using spr 1.3.6-beta.1

Author: pcc

lld/utils/run_benchmark.py

@@ -0,0 +1,131 @@
+#!/usr/bin/env python3
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+# ==------------------------------------------------------------------------==#
+
+import argparse
+import os
+import shutil
+import subprocess
+import tempfile
+
+# The purpose of this script is to measure the performance effect
+# of an lld change in a statistically sound way, automating all the
+# tedious parts of doing so. It copies the test case into /tmp as well as
+# running the test binaries from /tmp to reduce the influence on the test
+# machine's storage medium on the results. It accounts for measurement
+# bias caused by binary layout (using the --randomize-section-padding
+# flag to link the test binaries) and by environment variable size
+# (implemented by hyperfine [1]). Runs of the base and test case are
+# interleaved to account for environmental factors which may influence
+# the result due to the passage of time. The results of running hyperfine
+# are collected into a results.csv file in the output directory and may
+# be analyzed by the user with a tool such as ministat.
+#
+# Requirements: Linux host, hyperfine [2] in $PATH, run from a build directory
+# configured to use ninja and a recent version of lld that supports
+# --randomize-section-padding, /tmp is tmpfs.
+#
+# [1] https://github.com/sharkdp/hyperfine/blob/3cedcc38d0c430cbf38b4364b441c43a938d2bf3/src/util/randomized_environment_offset.rs#L1
+# [2] https://github.com/sharkdp/hyperfine
+#
+# Example invocation for comparing the performance of the current commit
+# against the previous commit which is treated as the baseline, without
+# linking debug info:
+#
+# lld/utils/run_benchmark.py \
+#   --base-commit HEAD^ \
+#   --test-commit HEAD \
+#   --test-case lld/utils/speed-test-reproducers/result/firefox-x64/response.txt \
+#   --num-iterations 512 \
+#   --num-binary-variants 16 \
+#   --output-dir outdir \
+#   --ldflags=-S
+#
+# Then this bash command will compare the real time of the base and test cases.
+#
+# ministat -A \
+#   <(grep lld-base outdir/results.csv | cut -d, -f2) \
+#   <(grep lld-test outdir/results.csv | cut -d, -f2)
+
+# We don't want to copy stat() information when we copy the reproducer
+# to the temporary directory. Files in the Nix store are read-only so this will
+# cause trouble when the linker writes the output file and when we want to clean
+# up the temporary directory. Python doesn't provide a way to disable copying
+# stat() information in shutil.copytree so we just monkeypatch shutil.copystat
+# to do nothing.
+shutil.copystat = lambda *args, **kwargs: 0
+
+parser = argparse.ArgumentParser(prog = 'benchmark_change.py')
+parser.add_argument('--base-commit', required=True)
+parser.add_argument('--test-commit', required=True)
+parser.add_argument('--test-case', required=True)
+parser.add_argument('--num-iterations', type=int, required=True)
+parser.add_argument('--num-binary-variants', type=int, required=True)
+parser.add_argument('--output-dir', required=True)
+parser.add_argument('--ldflags', required=False)
+args = parser.parse_args()
+
+test_dir = tempfile.mkdtemp()
+print(f'Using {test_dir} as temporary directory')
+
+os.makedirs(args.output_dir)
+print(f'Using {args.output_dir} as output directory')
+
+def extract_link_command(target):
+  # We assume that the last command printed by "ninja -t commands" containing a
+  # "-o" flag is the link command (we need to check for -o because subsequent
+  # commands create symlinks for ld.lld and so on). This is true for CMake and
+  # gn.
+  link_command = None
+  for line in subprocess.Popen(['ninja', '-t', 'commands', target],
+                               stdout=subprocess.PIPE).stdout.readlines():
+    commands = line.decode('utf-8').split('&&')
+    for command in commands:
+      if ' -o ' in command:
+        link_command = command.strip()
+  return link_command
+
+def generate_binary_variants(case_name):
+  subprocess.run(['ninja', 'lld'])
+  link_command = extract_link_command('lld')
+
+  for i in range(0, args.num_binary_variants):
+    print(f'Generating binary variant {i} for {case_name} case')
+    command = f'{link_command} -o {test_dir}/lld-{case_name}{i} -Wl,--randomize-section-padding={i}'
+    subprocess.run(command, check=True, shell=True)
+
+# Make sure that there are no local changes.
+subprocess.run(['git', 'diff', '--exit-code', 'HEAD'], check=True)
+
+# Resolve the base and test commit, since if they are relative to HEAD we will
+# check out the wrong commit below.
+resolved_base_commit = subprocess.check_output(['git', 'rev-parse', args.base_commit]).strip()
+resolved_test_commit = subprocess.check_output(['git', 'rev-parse', args.test_commit]).strip()
+
+test_case_dir = os.path.dirname(args.test_case)
+test_case_respfile = os.path.basename(args.test_case)
+
+test_dir_test_case_dir = f'{test_dir}/testcase'
+shutil.copytree(test_case_dir, test_dir_test_case_dir)
+
+subprocess.run(['git', 'checkout', resolved_base_commit], check=True)
+generate_binary_variants('base')
+
+subprocess.run(['git', 'checkout', resolved_test_commit], check=True)
+generate_binary_variants('test')
+
+def hyperfine_link_command(case_name):
+  return f'../lld-{case_name}$(({{iter}}%{args.num_binary_variants})) -flavor ld.lld @{test_case_respfile} {args.ldflags or ""}'
+
+results_csv = f'{args.output_dir}/results.csv'
+subprocess.run(['hyperfine', '--export-csv', os.path.abspath(results_csv),
+                '-P', 'iter', '0', str(args.num_iterations - 1),
+                hyperfine_link_command('base'),
+                hyperfine_link_command('test')],
+               check=True, cwd=test_dir_test_case_dir)
+
+shutil.rmtree(test_dir)