GHC 8.0.2: use -split-sections #21589
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@domenkozar, thanks for your PR! By analyzing the history of the files in this pull request, we identified @peti, @LnL7 and @cstrahan to be potential reviewers. |
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| # For GHC 8.0.2 we use split-sections instead | ||
| # Unsupported for Darwin/Clang, see http://hackage.haskell.org/trac/ghc/ticket/4013 | ||
| , enableSplitObjs ? (!stdenv.isDarwin && (stdenv.lib.versionAtLeast "8.0.1" ghc.version)) | ||
| , enableSplitSections ? (!stdenv.isDarwin && (stdenv.lib.versionOlder "8.0.1" ghc.version)) |
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Do we really need a new argument enableSplitSections for this change? It seems to me like "split objects" and "split sections" are two different implementations of the same concept, and IMHO it seems fine to control both with one option.
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There is also dead_strip for OSX, but it doesn't work all the time.
I was thinking of joining these, but based on different situations you might need to turn on/off different implementations of them.
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We could enable all of these with a single argument and disable those situations that don't work (for -dead_strip). If somone wants a different strategy, they can just disable and pass some --ghc-option flags. Thoughts?
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Yes, that sounds like a good compromise. We can also abstract the issue somewhat by adding an appropriate haskell.lib.dontDeadStrip function that hides the implementation. If it turns out that we need to control those flags in dozens of packages, then I'm all for (a) adding an appropriate option to the generic builder and (b) teaching cabal2nix to generate them when necessary.
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@peti sounds good. I think we should rename the option though, since objsplit would then imply section split for GHC 8.0.2 and we're overloading the term. Can we error out if enableSplitObjs is set and use general term such as enableDeadCodeElimination?
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Yes, I think that's a good solution. I like the name, too.
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Will you pick up this PR? It's a really nice feature and I'd love to have it in before we're forking off a new release branch. |
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Yes will do. Planning to clean this up very soon. |
-split-sections replaced -split-objs with following upsides: 1) -split-objs adds considerable overhead to compile time 2) combined with stripping, it causes issues when cross-compiling For upstream see https://ghc.haskell.org/trac/ghc/ticket/8405 This is supported only for Linux/Windows using ld linker. GHC master also turns on -split-sections by default. Example using stack: Without splitting $ du /nix/store/5paayhibayr73zqfaj458g4k4mv108jn-stack-1.3.2 4 /nix/store/5paayhibayr73zqfaj458g4k4mv108jn-stack-1.3.2/share/bash-completion/completions 4 /nix/store/5paayhibayr73zqfaj458g4k4mv108jn-stack-1.3.2/share/bash-completion 4 /nix/store/5paayhibayr73zqfaj458g4k4mv108jn-stack-1.3.2/share 23416 /nix/store/5paayhibayr73zqfaj458g4k4mv108jn-stack-1.3.2/bin 23420 /nix/store/5paayhibayr73zqfaj458g4k4mv108jn-stack-1.3.2 With -split-objs $ du /nix/store/fypymm529adpx71gdzm0851xz42wdbz0-stack-1.3.2 20632 /nix/store/fypymm529adpx71gdzm0851xz42wdbz0-stack-1.3.2/bin 4 /nix/store/fypymm529adpx71gdzm0851xz42wdbz0-stack-1.3.2/share/bash-completion/completions 4 /nix/store/fypymm529adpx71gdzm0851xz42wdbz0-stack-1.3.2/share/bash-completion 4 /nix/store/fypymm529adpx71gdzm0851xz42wdbz0-stack-1.3.2/share 20636 /nix/store/fypymm529adpx71gdzm0851xz42wdbz0-stack-1.3.2 With -split-sections $ du /nix/store/40l6krinx1zx41lr87c4m12hxj4ldf3x-stack-1.3.2 4 /nix/store/40l6krinx1zx41lr87c4m12hxj4ldf3x-stack-1.3.2/share/bash-completion/completions 4 /nix/store/40l6krinx1zx41lr87c4m12hxj4ldf3x-stack-1.3.2/share/bash-completion 4 /nix/store/40l6krinx1zx41lr87c4m12hxj4ldf3x-stack-1.3.2/share 20672 /nix/store/40l6krinx1zx41lr87c4m12hxj4ldf3x-stack-1.3.2/bin 20676 /nix/store/40l6krinx1zx41lr87c4m12hxj4ldf3x-stack-1.3.2 Note: you currently need following overrides to build stack on 802: vector-algorithms = dontCheck super.vector-algorithms; path-io = doJailbreak super.path-io; stack = doJailbreak super.stack; Note: Should also work on GHC 8.0.1, but I'm being careful here. We could backport later on.
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cc @peti ready for review :) |
See the commit for more information.
cc @peti, I haven't tested much (built stack and darcs) but upstream did quite some testing.