Add lto scons option #1601
Add lto scons option #1601
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…ne" in dev builds).
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Not sure why the windows builds are failing. I don't have this problem with any of my git runners. If this is related to the PR, we can default to no LTO on windows. Let me know what you think. |
| env.Append(CCFLAGS=["-flto=thin"]) | ||
| env.Append(LINKFLAGS=["-flto=thin"]) | ||
| elif env["lto"] == "full": | ||
| if env["use_llvm"]: | ||
| env.Append(CCFLAGS=["-flto"]) | ||
| env.Append(LINKFLAGS=["-flto"]) | ||
| else: | ||
| env.AppendUnique(CCFLAGS=["/GL"]) | ||
| env.AppendUnique(ARFLAGS=["/LTCG"]) | ||
| env.AppendUnique(LINKFLAGS=["/LTCG"]) |
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This mixes up parameter flags a bit, more importantly, use_llvm and is_msvc is not a real scenario.
if env.get("is_msvc", False), use_llvm is ignored, you might want to check use_clang_cl instead ("Use the clang driver instead of MSVC"), and use windows format for flags (/opt).
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This is what I thought as well, but I'm mirroring what Godot does: https://github.com/godotengine/godot/blob/master/platform/windows/detect.py#L620
(note it's the MSVC branch this is in)
If you think this is not a real scenario, maybe this is worth a PR into the main repository as well? Let me know if I should still change it according to your suggestion.
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Mmmhhh.. the - vs / flags upstream is suspicious, but I think more importantly there's a discrepancy between godot-cpp and godot where we use use_clang_cl instead of use_llvm in godot-cpp for the llvm msvc driver.
So currently, that scenario can never happen in godot-cpp, but I think we should unify the use_clang_cl flag with use_llvm and, like upstream godot does(?), use the llvm MSVC backend unless use_mingw is also specified.
But we should probably double check this with someone more into the windows part of the build system.
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I've opened #1602 to discuss that change specifically.
The behavior mimics almost the exact behavior (minus "progress" options) of Godot scons:
This is an active change (edit: not anymore, defaults to 'none' by default now): Once merged, all projects depending on godot-cpp (and updating the submodule) will gain LTO for release builds. I tested a similar setup in my own project, not the exact same though (because I don't have all combinations of windows, msvc, mingw and use_llvm available). However, since that it mimics what Godot does already, it should be good, given I did not make mistakes.
One important difference is that in my implementation (edit: not anymore, consistently 'none' by default now), "auto" is consistent across platforms ("full" in production, "none" in dev). I saw small, but consistent gains in all platforms, and don't see why LTO should be avoided in some platforms by default.