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SCons: Refactor LTO options with `lto=<none|thin|full>` 

Adds support for LTO on macOS and Android. We don't have much experience
with LTO on these platforms so for now we keep it disabled by default
even when `production=yes` is set.

Similarly for iOS where we ship object files for the user to link in
Xcode so LTO makes builds extremely slow to link.

`production=yes` defaults to full LTO.
ThinLTO is much faster for LLVM-based compilers but seems to produce
bigger binaries (at least for the Web platform).
This commit is contained in:
Rémi Verschelde 2022-07-21 15:15:54 +02:00
parent 69233093d7
commit c2c659db32
7 changed files with 94 additions and 60 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

62
SConstruct
View File

@ -170,7 +170,7 @@ opts.Add(EnumVariable("arch", "CPU architecture", "auto", ["auto"] + architectur
opts.Add(EnumVariable("float", "Floating-point precision", "32", ("32", "64")))
opts.Add(EnumVariable("optimize", "Optimization type", "speed", ("speed", "size", "none")))
opts.Add(BoolVariable("production", "Set defaults to build Godot for use in production", False))
opts.Add(BoolVariable("use_lto", "Use link-time optimization", False))
opts.Add(EnumVariable("lto", "Link-time optimization (for production buids)", "none", ("none", "thin", "full")))
# Components
opts.Add(BoolVariable("deprecated", "Enable compatibility code for deprecated and removed features", True))
@ -438,35 +438,6 @@ if selected_platform in platform_list:
)
env.SetOption("num_jobs", safer_cpu_count)
# 'dev' and 'production' are aliases to set default options if they haven't been set
# manually by the user.
if env["dev"]:
env["verbose"] = methods.get_cmdline_bool("verbose", True)
env["warnings"] = ARGUMENTS.get("warnings", "extra")
env["werror"] = methods.get_cmdline_bool("werror", True)
if env["tools"]:
env["tests"] = methods.get_cmdline_bool("tests", True)
if env["production"]:
env["use_static_cpp"] = methods.get_cmdline_bool("use_static_cpp", True)
env["use_lto"] = methods.get_cmdline_bool("use_lto", True)
env["debug_symbols"] = methods.get_cmdline_bool("debug_symbols", False)
if not env["tools"] and env["target"] == "debug":
print(
"WARNING: Requested `production` build with `tools=no target=debug`, "
"this will give you a full debug template (use `target=release_debug` "
"for an optimized template with debug features)."
)
if env.msvc:
print(
"WARNING: For `production` Windows builds, you should use MinGW with GCC "
"or Clang instead of Visual Studio, as they can better optimize the "
"GDScript VM in a very significant way. MSVC LTO also doesn't work "
"reliably for our use case."
"If you want to use MSVC nevertheless for production builds, set "
"`debug_symbols=no use_lto=no` instead of the `production=yes` option."
)
Exit(255)
env.extra_suffix = ""
if env["extra_suffix"] != "":
@ -517,6 +488,37 @@ if selected_platform in platform_list:
# We apply it to CCFLAGS (both C and C++ code) in case it impacts C features.
env.Prepend(CCFLAGS=["/std:c++17"])
# 'dev' and 'production' are aliases to set default options if they haven't been set
# manually by the user.
if env["dev"]:
env["verbose"] = methods.get_cmdline_bool("verbose", True)
env["warnings"] = ARGUMENTS.get("warnings", "extra")
env["werror"] = methods.get_cmdline_bool("werror", True)
if env["tools"]:
env["tests"] = methods.get_cmdline_bool("tests", True)
if env["production"]:
env["use_static_cpp"] = methods.get_cmdline_bool("use_static_cpp", True)
env["lto"] = ARGUMENTS.get("lto", "full")
env["debug_symbols"] = methods.get_cmdline_bool("debug_symbols", False)
if not env["tools"] and env["target"] == "debug":
print(
"WARNING: Requested `production` build with `tools=no target=debug`, "
"this will give you a full debug template (use `target=release_debug` "
"for an optimized template with debug features)."
)
if env.msvc:
print(
"WARNING: For `production` Windows builds, you should use MinGW with GCC "
"or Clang instead of Visual Studio, as they can better optimize the "
"GDScript VM in a very significant way. MSVC LTO also doesn't work "
"reliably for our use case."
"If you want to use MSVC nevertheless for production builds, set "
"`debug_symbols=no lto=none` instead of the `production=yes` option."
)
Exit(255)
if env["lto"] != "none":
print("Using LTO: " + env["lto"])
# Enforce our minimal compiler version requirements
cc_version = methods.get_compiler_version(env) or {
"major": None,

12
platform/android/detect.py
View File

@ -47,6 +47,9 @@ def get_flags():
return [
("arch", "arm64"), # Default for convenience.
("tools", False),
# Benefits of LTO for Android (size, performance) haven't been clearly established yet.
# So for now we override the default value which may be set when using `production=yes`.
("lto", "none"),
]
@ -132,6 +135,15 @@ def configure(env):
env.Append(CPPDEFINES=["_DEBUG"])
env.Append(CPPFLAGS=["-UNDEBUG"])
# LTO
if env["lto"] != "none":
if env["lto"] == "thin":
env.Append(CCFLAGS=["-flto=thin"])
env.Append(LINKFLAGS=["-flto=thin"])
else:
env.Append(CCFLAGS=["-flto"])
env.Append(LINKFLAGS=["-flto"])
# Compiler configuration
env["SHLIBSUFFIX"] = ".so"

14
platform/ios/detect.py
View File

@ -39,6 +39,9 @@ def get_flags():
("arch", "arm64"), # Default for convenience.
("tools", False),
("use_volk", False),
# Disable by default even if production is set, as it makes linking in Xcode
# on exports very slow and that's not what most users expect.
("lto", "none"),
]
@ -70,9 +73,14 @@ def configure(env):
env.Append(CCFLAGS=["-gdwarf-2", "-O0"])
env.Append(CPPDEFINES=["_DEBUG", ("DEBUG", 1)])
if env["use_lto"]:
env.Append(CCFLAGS=["-flto"])
env.Append(LINKFLAGS=["-flto"])
# LTO
if env["lto"] != "none":
if env["lto"] == "thin":
env.Append(CCFLAGS=["-flto=thin"])
env.Append(LINKFLAGS=["-flto=thin"])
else:
env.Append(CCFLAGS=["-flto"])
env.Append(LINKFLAGS=["-flto"])
## Compiler configuration

16
platform/linuxbsd/detect.py
View File

@ -31,7 +31,6 @@ def get_opts():
return [
EnumVariable("linker", "Linker program", "default", ("default", "bfd", "gold", "lld", "mold")),
BoolVariable("use_llvm", "Use the LLVM compiler", False),
BoolVariable("use_thinlto", "Use ThinLTO (LLVM only, requires linker=lld, implies use_lto=yes)", False),
BoolVariable("use_static_cpp", "Link libgcc and libstdc++ statically for better portability", True),
BoolVariable("use_coverage", "Test Godot coverage", False),
BoolVariable("use_ubsan", "Use LLVM/GCC compiler undefined behavior sanitizer (UBSAN)", False),
@ -129,13 +128,6 @@ def configure(env):
else:
env.Append(LINKFLAGS=["-fuse-ld=%s" % env["linker"]])
if env["use_thinlto"]:
if not env["use_llvm"] or env["linker"] != "lld":
print("ThinLTO is only compatible with LLVM and the LLD linker, use `use_llvm=yes linker=lld`.")
sys.exit(255)
else:
env["use_lto"] = True # ThinLTO implies LTO
if env["use_coverage"]:
env.Append(CCFLAGS=["-ftest-coverage", "-fprofile-arcs"])
env.Append(LINKFLAGS=["-ftest-coverage", "-fprofile-arcs"])
@ -178,8 +170,12 @@ def configure(env):
env.Append(CCFLAGS=["-fsanitize-recover=memory"])
env.Append(LINKFLAGS=["-fsanitize=memory"])
if env["use_lto"]:
if env["use_thinlto"]:
# LTO
if env["lto"] != "none":
if env["lto"] == "thin":
if not env["use_llvm"]:
print("ThinLTO is only compatible with LLVM, use `use_llvm=yes` or `lto=full`.")
sys.exit(255)
env.Append(CCFLAGS=["-flto=thin"])
env.Append(LINKFLAGS=["-flto=thin"])
elif not env["use_llvm"] and env.GetOption("num_jobs") > 1:

12
platform/macos/detect.py
View File

@ -40,6 +40,9 @@ def get_flags():
return [
("arch", detect_arch()),
("use_volk", False),
# Benefits of LTO for macOS (size, performance) haven't been clearly established yet.
# So for now we override the default value which may be set when using `production=yes`.
("lto", "none"),
]
@ -166,6 +169,15 @@ def configure(env):
env["RANLIB"] = basecmd + "ranlib"
env["AS"] = basecmd + "as"
# LTO
if env["lto"] != "none":
if env["lto"] == "thin":
env.Append(CCFLAGS=["-flto=thin"])
env.Append(LINKFLAGS=["-flto=thin"])
else:
env.Append(CCFLAGS=["-flto"])
env.Append(LINKFLAGS=["-flto"])
if env["use_ubsan"] or env["use_asan"] or env["use_tsan"]:
env.extra_suffix += ".san"
env.Append(CCFLAGS=["-DSANITIZERS_ENABLED"])

14
platform/web/detect.py
View File

@ -31,7 +31,6 @@ def get_opts():
return [
("initial_memory", "Initial WASM memory (in MiB)", 32),
BoolVariable("use_assertions", "Use Emscripten runtime assertions", False),
BoolVariable("use_thinlto", "Use ThinLTO", False),
BoolVariable("use_ubsan", "Use Emscripten undefined behavior sanitizer (UBSAN)", False),
BoolVariable("use_asan", "Use Emscripten address sanitizer (ASAN)", False),
BoolVariable("use_lsan", "Use Emscripten leak sanitizer (LSAN)", False),
@ -110,12 +109,13 @@ def configure(env):
env["ENV"] = os.environ
# LTO
if env["use_thinlto"]:
env.Append(CCFLAGS=["-flto=thin"])
env.Append(LINKFLAGS=["-flto=thin"])
elif env["use_lto"]:
env.Append(CCFLAGS=["-flto=full"])
env.Append(LINKFLAGS=["-flto=full"])
if env["lto"] != "none":
if env["lto"] == "thin":
env.Append(CCFLAGS=["-flto=thin"])
env.Append(LINKFLAGS=["-flto=thin"])
else:
env.Append(CCFLAGS=["-flto"])
env.Append(LINKFLAGS=["-flto"])
# Sanitizers
if env["use_ubsan"]:

24
platform/windows/detect.py
View File

@ -191,7 +191,6 @@ def get_opts():
),
BoolVariable("use_mingw", "Use the Mingw compiler, even if MSVC is installed.", False),
BoolVariable("use_llvm", "Use the LLVM compiler", False),
BoolVariable("use_thinlto", "Use ThinLTO", False),
BoolVariable("use_static_cpp", "Link MinGW/MSVC C++ runtime libraries statically", True),
BoolVariable("use_asan", "Use address sanitizer (ASAN)", False),
]
@ -449,7 +448,10 @@ def configure_msvc(env, vcvars_msvc_config):
## LTO
if env["use_lto"]:
if env["lto"] != "none":
if env["lto"] == "thin":
print("ThinLTO is only compatible with LLVM, use `use_llvm=yes` or `lto=full`.")
sys.exit(255)
env.AppendUnique(CCFLAGS=["/GL"])
env.AppendUnique(ARFLAGS=["/LTCG"])
if env["progress"]:
@ -562,17 +564,19 @@ def configure_mingw(env):
if try_cmd("gcc-ranlib --version", env["mingw_prefix"], env["arch"]):
env["RANLIB"] = mingw_bin_prefix + "gcc-ranlib"
if env["use_lto"]:
if not env["use_llvm"] and env.GetOption("num_jobs") > 1:
if env["lto"] != "none":
if env["lto"] == "thin":
if not env["use_llvm"]:
print("ThinLTO is only compatible with LLVM, use `use_llvm=yes` or `lto=full`.")
sys.exit(255)
env.Append(CCFLAGS=["-flto=thin"])
env.Append(LINKFLAGS=["-flto=thin"])
elif not env["use_llvm"] and env.GetOption("num_jobs") > 1:
env.Append(CCFLAGS=["-flto"])
env.Append(LINKFLAGS=["-flto=" + str(env.GetOption("num_jobs"))])
else:
if env["use_thinlto"]:
env.Append(CCFLAGS=["-flto=thin"])
env.Append(LINKFLAGS=["-flto=thin"])
else:
env.Append(CCFLAGS=["-flto"])
env.Append(LINKFLAGS=["-flto"])
env.Append(CCFLAGS=["-flto"])
env.Append(LINKFLAGS=["-flto"])
env.Append(LINKFLAGS=["-Wl,--stack," + str(STACK_SIZE)])