Enable clang build timing analysis

I didn't enable this by default for clang due to making the build time
10% worse or so. Unfortunate, but tbh devs for whom 10% of build time is
not *that* bad should probably simply enable this.

Change-Id: I8d1e5b6f3f76c649a4e2f115f534f7f97cee46e6
This commit is contained in:
Jade Lovelace 2024-03-18 23:03:48 -07:00 committed by jade
parent 50c6feeb77
commit 412a9c9f67
7 changed files with 80 additions and 0 deletions

3
.gitignore vendored
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@ -154,3 +154,6 @@ result-*
# Mac OS
.DS_Store
# ClangBuildAnalyzer output, see maintainers/buildtime_report.sh
buildtime.bin

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@ -0,0 +1,15 @@
---
synopsis: Clang build timing analysis
cls: 587
---
We now have Clang build profiling available, which generates Chrome
tracing files for each compilation unit. To enable it, run `meson configure
build -Dprofile-build=enabled` then rerun the compilation.
If you want to make the build go faster, do a clang build with meson, then run
`maintainers/buildtime_report.sh build`, then contemplate how to improve the
build time.
You can also look at individual object files' traces in
<https://ui.perfetto.dev>.

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@ -152,6 +152,7 @@
build-release-notes =
final.buildPackages.callPackage ./maintainers/build-release-notes.nix { };
clangbuildanalyzer = final.buildPackages.callPackage ./misc/clangbuildanalyzer.nix { };
boehmgc-nix = (final.boehmgc.override {
enableLargeConfig = true;
}).overrideAttrs (o: {
@ -360,6 +361,8 @@
# FIXME(Qyriad): remove once the migration to Meson is complete.
pkgs.buildPackages.meson
pkgs.buildPackages.ninja
pkgs.buildPackages.clangbuildanalyzer
];
src = null;

20
maintainers/buildtime_report.sh Executable file
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@ -0,0 +1,20 @@
#!/bin/sh
# Generates a report of build time based on a meson build using -ftime-trace in
# Clang.
if [ $# -lt 1 ]; then
echo "usage: $0 BUILD-DIR [filename]" >&2
exit 1
fi
scriptdir=$(cd "$(dirname -- "$0")" || exit ; pwd -P)
filename=${2:-$scriptdir/../buildtime.bin}
if [ "$(meson introspect "$1" --buildoptions | jq -r '.[] | select(.name == "profile-build") | .value')" != enabled ]; then
echo 'This build was not done with profile-build enabled, so cannot generate a report' >&2
# shellcheck disable=SC2016
echo 'Run `meson configure build -Dprofile-build=enabled` then rebuild, first' >&2
exit 1
fi
ClangBuildAnalyzer --all "$1" "$filename" && ClangBuildAnalyzer --analyze "$filename"

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@ -307,6 +307,14 @@ if cxx.get_linker_id() in ['ld.bfd', 'ld.gold']
add_project_link_arguments('-Wl,--no-copy-dt-needed-entries', language : 'cpp')
endif
# Generate Chromium tracing files for each compiled file, which enables
# maintainers/buildtime_report.sh BUILD-DIR to simply work in clang builds.
#
# They can also be manually viewed at https://ui.perfetto.dev
if get_option('profile-build').require(meson.get_compiler('cpp').get_id() == 'clang').enabled()
add_project_arguments('-ftime-trace', language: 'cpp')
endif
subdir('src')
if enable_tests
subdir('tests/unit')

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@ -31,6 +31,10 @@ option('tests-brief', type : 'boolean', value : false,
description : 'set to true for shorter tests output',
)
option('profile-build', type : 'feature', value: 'disabled',
description : 'whether to enable -ftime-trace in clang builds, allowing for speeding up the build.'
)
option('store-dir', type : 'string', value : '/nix/store',
description : 'path of the Nix store',
)

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@ -0,0 +1,27 @@
# Upstreaming here, can be deleted once it's upstreamed:
# https://github.com/NixOS/nixpkgs/pull/297102
{ stdenv, lib, cmake, fetchFromGitHub }:
stdenv.mkDerivation (finalAttrs: {
pname = "clangbuildanalyzer";
version = "1.5.0";
src = fetchFromGitHub {
owner = "aras-p";
repo = "ClangBuildAnalyzer";
rev = "v${finalAttrs.version}";
sha256 = "sha256-kmgdk634zM0W0OoRoP/RzepArSipa5bNqdVgdZO9gxo=";
};
nativeBuildInputs = [
cmake
];
meta = {
description = "Tool for analyzing Clang's -ftrace-time files";
homepage = "https://github.com/aras-p/ClangBuildAnalyzer";
maintainers = with lib.maintainers; [ lf- ];
license = lib.licenses.unlicense;
platforms = lib.platforms.unix;
mainProgram = "ClangBuildAnalyzer";
};
})