120 lines · python
1#!/usr/bin/env python32#3# Determines which clang-tidy checks are "fast enough" to run in clangd.4# This runs clangd --check --check-tidy-time and parses the output.5# This program outputs a header fragment specifying which checks are fast:6# FAST(bugprone-argument-comment, 5)7# SLOW(misc-const-correctness, 200)8# If given the old header fragment as input, we lean to preserve its choices.9#10# This is not deterministic or hermetic, but should be run occasionally to11# update the list of allowed checks. From llvm-project:12# clang-tools-extra/clangd/TidyFastChecks.py --clangd=build-opt/bin/clangd13# Be sure to use an optimized, no-asserts, tidy-enabled build of clangd!14 15import argparse16import os17import re18import subprocess19import sys20 21# Checks faster than FAST_THRESHOLD are fast, slower than SLOW_THRESHOLD slow.22# If a check is in between, we stick with our previous decision. This avoids23# enabling/disabling checks between releases due to random measurement jitter.24FAST_THRESHOLD = 8 # percent25SLOW_THRESHOLD = 1526 27parser = argparse.ArgumentParser()28parser.add_argument(29 "--target",30 help="X-macro output file. "31 "If it exists, existing contents will be used for hysteresis",32 default="clang-tools-extra/clangd/TidyFastChecks.inc",33)34parser.add_argument(35 "--source",36 help="Source file to benchmark tidy checks",37 default="clang/lib/Sema/Sema.cpp",38)39parser.add_argument(40 "--clangd", help="clangd binary to invoke", default="build/bin/clangd"41)42parser.add_argument("--checks", help="check glob to run", default="*")43parser.add_argument("--verbose", help="log clangd output", action="store_true")44args = parser.parse_args()45 46# Use the preprocessor to extract the list of previously-fast checks.47def read_old_fast(path):48 text = subprocess.check_output(49 [50 "cpp",51 "-P", # Omit GNU line markers52 "-nostdinc", # Don't include stdc-predef.h53 "-DFAST(C,T)=C", # Print fast checks only54 path,55 ]56 )57 for line in text.splitlines():58 if line.strip():59 yield line.strip().decode("utf-8")60 61 62old_fast = list(read_old_fast(args.target)) if os.path.exists(args.target) else []63print(f"Old fast checks: {old_fast}", file=sys.stderr)64 65# Runs clangd --check --check-tidy-time.66# Yields (check, percent-overhead) pairs.67def measure():68 process = subprocess.Popen(69 [70 args.clangd,71 "--check=" + args.source,72 "--check-locations=0", # Skip useless slow steps.73 "--check-tidy-time=" + args.checks,74 ],75 stderr=subprocess.PIPE,76 )77 recording = False78 for line in iter(process.stderr.readline, b""):79 if args.verbose:80 print("clangd> ", line, file=sys.stderr)81 if not recording:82 if b"Timing AST build with individual clang-tidy checks" in line:83 recording = True84 continue85 if b"Finished individual clang-tidy checks" in line:86 return87 match = re.search(rb"(\S+) = (\S+)%", line)88 if match:89 yield (match.group(1).decode("utf-8"), float(match.group(2)))90 91 92with open(args.target, "w", buffering=1) as target:93 # Produce an includable X-macros fragment with our decisions.94 print(95 f"""// This file is generated, do not edit it directly!96// Deltas are percentage regression in parsing {args.source}97#ifndef FAST98#define FAST(CHECK, DELTA)99#endif100#ifndef SLOW101#define SLOW(CHECK, DELTA)102#endif103""",104 file=target,105 )106 107 for check, time in measure():108 threshold = SLOW_THRESHOLD if check in old_fast else FAST_THRESHOLD109 decision = "FAST" if time <= threshold else "SLOW"110 print(f"{decision} {check} {time}% <= {threshold}%", file=sys.stderr)111 print(f"{decision}({check}, {time})", file=target)112 113 print(114 """115#undef FAST116#undef SLOW117""",118 file=target,119 )120