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Merge pull request #8087 from dcbaker/submit/lto-extensions 

Add option for thinLTO
This commit is contained in:
Jussi Pakkanen 2021-02-02 22:17:13 +00:00 committed by GitHub
parent 65b3d67c7e 6f532b72c8
commit cd94cf8995
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GPG Key ID: 4AEE18F83AFDEB23
7 changed files with 140 additions and 26 deletions
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46
docs/markdown/Builtin-options.md
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@ -119,30 +119,36 @@ no options.
The following options are available. Note that they may not be
available on all platforms or with all compilers:
| Option | Default value | Possible values | Description |
| ----------- | ------------- | --------------- | ----------- |
| b_asneeded | true | true, false | Use -Wl,--as-needed when linking |
| b_bitcode | false | true, false | Embed Apple bitcode, see below |
| b_colorout | always | auto, always, never | Use colored output |
| b_coverage | false | true, false | Enable coverage tracking |
| b_lundef | true | true, false | Don't allow undefined symbols when linking |
| b_lto | false | true, false | Use link time optimization |
| b_ndebug | false | true, false, if-release | Disable asserts |
| b_pch | true | true, false | Use precompiled headers |
| b_pgo | off | off, generate, use | Use profile guided optimization |
| b_sanitize | none | see below | Code sanitizer to use |
| b_staticpic | true | true, false | Build static libraries as position independent |
| b_pie | false | true, false | Build position-independent executables (since 0.49.0)|
| b_vscrt | from_buildtype| none, md, mdd, mt, mtd, from_buildtype, static_from_buildtype | VS runtime library to use (since 0.48.0) (static_from_buildtype since 0.56.0) |
| Option | Default value | Possible values | Description |
|---------------|----------------|------------------------------------------------------------------|-------------------------------------------------------------------------------|
| b_asneeded | true | true, false | Use -Wl,--as-needed when linking |
| b_bitcode | false | true, false | Embed Apple bitcode, see below |
| b_colorout | always | auto, always, never | Use colored output |
| b_coverage | false | true, false | Enable coverage tracking |
| b_lundef | true | true, false | Don't allow undefined symbols when linking |
| b_lto | false | true, false | Use link time optimization |
| b_lto_threads | 0 | Any integer* | Use multiple threads for lto. *(Added in 0.57.0)* |
| b_lto_mode | default | default, thin | Select between lto modes, thin and default. *(Added in 0.57.0)* |
| b_ndebug | false | true, false, if-release | Disable asserts |
| b_pch | true | true, false | Use precompiled headers |
| b_pgo | off | off, generate, use | Use profile guided optimization |
| b_sanitize | none | see below | Code sanitizer to use |
| b_staticpic | true | true, false | Build static libraries as position independent |
| b_pie | false | true, false | Build position-independent executables (since 0.49.0) |
| b_vscrt | from_buildtype | none, md, mdd, mt, mtd, from_buildtype, static_from_buildtype | VS runtime library to use (since 0.48.0) (static_from_buildtype since 0.56.0) |
The value of `b_sanitize` can be one of: `none`, `address`, `thread`,
`undefined`, `memory`, `address,undefined`.
<a name="b_vscrt-from_buildtype"></a> The default value of `b_vscrt`
is `from_buildtype`. The following table is used internally to pick
the CRT compiler arguments for `from_buildtype` or
`static_from_buildtype` *(since 0.56)* based on the value of the
`buildtype` option:
* < 0 means disable, == 0 means automatic selection, > 0 sets a specific number to use
LLVM supports `thin` lto, for more discussion see [LLVM's documentation](https://clang.llvm.org/docs/ThinLTO.html)
<a name="b_vscrt-from_buildtype"></a>
The default value of `b_vscrt` is `from_buildtype`. The following table is
used internally to pick the CRT compiler arguments for `from_buildtype` or
`static_from_buildtype` *(since 0.56)* based on the value of the `buildtype`
option:
| buildtype | from_buildtype | static_from_buildtype |
| -------- | -------------- | --------------------- |

5
docs/markdown/snippets/lto_mode.md Normal file
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@ -0,0 +1,5 @@
## Support added for LLVM's thinLTO
A new `b_lto_mode` option has been added, which may be set to `default` or
`thin`. Thin only works for clang, and only with gnu gold, lld variants, or
ld64.

7
docs/markdown/snippets/lto_threads.md Normal file
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@ -0,0 +1,7 @@
## Knob to control LTO thread
Both the gnu linker and lld support using threads for speading up LTO, meson
now provides a knob for this: `-Db_lto_threads`. Currently this is only
supported for clang and gcc. Any positive integer is supported, `0` means
`auto`. If the compiler or linker implemnets it's on `auto` we use that,
otherwise the number of threads on the machine is used.

24
mesonbuild/compilers/compilers.py
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@ -268,6 +268,11 @@ clike_debug_args = {False: [],
base_options: 'KeyedOptionDictType' = {
OptionKey('b_pch'): coredata.UserBooleanOption('Use precompiled headers', True),
OptionKey('b_lto'): coredata.UserBooleanOption('Use link time optimization', False),
OptionKey('b_lto'): coredata.UserBooleanOption('Use link time optimization', False),
OptionKey('b_lto_threads'): coredata.UserIntegerOption('Use multiple threads for Link Time Optimization', (None, None,0)),
OptionKey('b_lto_mode'): coredata.UserComboOption('Select between different LTO modes.',
['default', 'thin'],
'default'),
OptionKey('b_sanitize'): coredata.UserComboOption('Code sanitizer to use',
['none', 'address', 'thread', 'undefined', 'memory', 'address,undefined'],
'none'),
@ -300,11 +305,26 @@ def option_enabled(boptions: T.Set[OptionKey], options: 'KeyedOptionDictType',
except KeyError:
return False
def get_option_value(options: 'KeyedOptionDictType', opt: OptionKey, fallback: '_T') -> '_T':
"""Get the value of an option, or the fallback value."""
try:
v: '_T' = options[opt].value
except KeyError:
return fallback
assert isinstance(v, type(fallback)), f'Should have {type(fallback)!r} but was {type(v)!r}'
# Mypy doesn't understand that the above assert ensures that v is type _T
return v
def get_base_compile_args(options: 'KeyedOptionDictType', compiler: 'Compiler') -> T.List[str]:
args = [] # type T.List[str]
try:
if options[OptionKey('b_lto')].value:
args.extend(compiler.get_lto_compile_args())
args.extend(compiler.get_lto_compile_args(
threads=get_option_value(options, OptionKey('b_lto_threads'), 0),
mode=get_option_value(options, OptionKey('b_lto_mode'), 'default')))
except KeyError:
pass
try:
@ -926,7 +946,7 @@ class Compiler(metaclass=abc.ABCMeta):
ret.append(arg)
return ret
def get_lto_compile_args(self) -> T.List[str]:
def get_lto_compile_args(self, *, threads: int = 0, mode: str = 'default') -> T.List[str]:
return []
def get_lto_link_args(self) -> T.List[str]:

21
mesonbuild/compilers/mixins/clang.py
View File

@ -19,7 +19,7 @@ import shutil
import typing as T
from ... import mesonlib
from ...linkers import AppleDynamicLinker
from ...linkers import AppleDynamicLinker, ClangClDynamicLinker, LLVMDynamicLinker, GnuGoldDynamicLinker
from ...mesonlib import OptionKey
from ..compilers import CompileCheckMode
from .gnu import GnuLikeCompiler
@ -49,7 +49,9 @@ class ClangCompiler(GnuLikeCompiler):
super().__init__()
self.id = 'clang'
self.defines = defines or {}
self.base_options.add(OptionKey('b_colorout'))
self.base_options.update(
{OptionKey('b_colorout'), OptionKey('b_lto_threads'), OptionKey('b_lto_mode')})
# TODO: this really should be part of the linker base_options, but
# linkers don't have base_options.
if isinstance(self.linker, AppleDynamicLinker):
@ -135,3 +137,18 @@ class ClangCompiler(GnuLikeCompiler):
def get_coverage_link_args(self) -> T.List[str]:
return ['--coverage']
def get_lto_compile_args(self, *, threads: int = 0, mode: str = 'default') -> T.List[str]:
args: T.List[str] = []
if mode == 'thin':
# Thin LTO requires the use of gold, lld, ld64, or lld-link
if not isinstance(self.linker, (AppleDynamicLinker, ClangClDynamicLinker, LLVMDynamicLinker, GnuGoldDynamicLinker)):
raise mesonlib.MesonException(f"LLVM's thinLTO only works with gnu gold, lld, lld-link, and ld64, not {self.linker.id}")
args.append(f'-flto={mode}')
else:
assert mode == 'default', 'someone forgot to wire something up'
args.extend(super().get_lto_compile_args(threads=threads))
# In clang -flto=0 means auto
if threads >= 0:
args.append(f'-flto-jobs={threads}')
return args

17
mesonbuild/compilers/mixins/gnu.py
View File

@ -17,6 +17,7 @@
import abc
import functools
import os
import multiprocessing
import pathlib
import re
import subprocess
@ -281,7 +282,9 @@ class GnuLikeCompiler(Compiler, metaclass=abc.ABCMeta):
return self._split_fetch_real_dirs(line.split('=', 1)[1])
return []
def get_lto_compile_args(self) -> T.List[str]:
def get_lto_compile_args(self, *, threads: int = 0, mode: str = 'default') -> T.List[str]:
# This provides a base for many compilers, GCC and Clang override this
# for their specific arguments
return ['-flto']
def sanitizer_compile_args(self, value: str) -> T.List[str]:
@ -330,7 +333,7 @@ class GnuCompiler(GnuLikeCompiler):
super().__init__()
self.id = 'gcc'
self.defines = defines or {}
self.base_options.add(OptionKey('b_colorout'))
self.base_options.update({OptionKey('b_colorout'), OptionKey('b_lto_threads')})
def get_colorout_args(self, colortype: str) -> T.List[str]:
if mesonlib.version_compare(self.version, '>=4.9.0'):
@ -383,3 +386,13 @@ class GnuCompiler(GnuLikeCompiler):
def get_prelink_args(self, prelink_name: str, obj_list: T.List[str]) -> T.List[str]:
return ['-r', '-o', prelink_name] + obj_list
def get_lto_compile_args(self, *, threads: int = 0, mode: str = 'default') -> T.List[str]:
if threads == 0:
if mesonlib.version_compare(self.version, '>= 10.0'):
return ['-flto=auto']
# This matches clang's behavior of using the number of cpus
return [f'-flto={multiprocessing.cpu_count()}']
elif threads > 0:
return [f'-flto={threads}']
return super().get_lto_compile_args(threads=threads)

46
run_unittests.py
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@ -2843,6 +2843,52 @@ class AllPlatformTests(BasePlatformTests):
self.build()
self.run_tests()
@skip_if_not_base_option('b_lto_threads')
def test_lto_threads(self):
testdir = os.path.join(self.common_test_dir, '6 linkshared')
env = get_fake_env(testdir, self.builddir, self.prefix)
cc = env.detect_c_compiler(MachineChoice.HOST)
if cc.get_id() == 'clang' and is_windows():
raise unittest.SkipTest('LTO not (yet) supported by windows clang')
self.init(testdir, extra_args=['-Db_lto=true', '-Db_lto_threads=8'])
self.build()
self.run_tests()
expected = set(cc.get_lto_compile_args(threads=8))
targets = self.introspect('--targets')
# This assumes all of the targets support lto
for t in targets:
for s in t['target_sources']:
for e in expected:
self.assertIn(e, s['parameters'])
@skip_if_not_base_option('b_lto_mode')
@skip_if_not_base_option('b_lto_threads')
def test_lto_mode(self):
testdir = os.path.join(self.common_test_dir, '6 linkshared')
env = get_fake_env(testdir, self.builddir, self.prefix)
cc = env.detect_c_compiler(MachineChoice.HOST)
if cc.get_id() != 'clang':
raise unittest.SkipTest('Only clang currently supports thinLTO')
if cc.linker.id not in {'ld.lld', 'ld.gold', 'ld64', 'lld-link'}:
raise unittest.SkipTest('thinLTO requires ld.lld, ld.gold, ld64, or lld-link')
elif is_windows():
raise unittest.SkipTest('LTO not (yet) supported by windows clang')
self.init(testdir, extra_args=['-Db_lto=true', '-Db_lto_mode=thin', '-Db_lto_threads=8'])
self.build()
self.run_tests()
expected = set(cc.get_lto_compile_args(threads=8, mode='thin'))
targets = self.introspect('--targets')
# This assumes all of the targets support lto
for t in targets:
for s in t['target_sources']:
assert expected.issubset(set(s['parameters'])), f'Incorrect values for {t["name"]}'
def test_dist_git(self):
if not shutil.which('git'):
raise unittest.SkipTest('Git not found')