Use ld.gold in dev shells #1868

TeofilC · 2023-02-28T09:30:39Z

Previously we built GHC with ld.gold for aarch32, and forced use of ld.gold in the component builder for non-android linux. Though this meant that ld.gold wasn't used in dev shells on non-android linux as that uses a different code-path.

This patch unifies all of this logic in one place: in the GHC build script.
If GHC is fed LD as being ld.gold then it will write that into its settings and try to use that at runtime.

So, we also build GHC with ld.gold on non-android linux, meaning that it uses that both in component builds and dev shells.

Unfortunately this will lead to mass rebuilds. I experimented with just duplicating the component logic in the ghcWrapper used in dev shells, but this led to mass rebuilds anyway, so, I think we might as well do the more principled thing.

Resolves #1866

michaelpj · 2023-02-28T11:15:54Z

Did you manage to build a shell with this? Do you get the link-time speedups we'd expect?

TeofilC · 2023-02-28T11:24:06Z

@michaelpj I've tested with GHC-9.2.6 on x86_64-linux and as far as I can tell it's using ld.gold. I'll try to test with a hadrian built GHC as well just to be safe

TeofilC · 2023-02-28T14:03:21Z

I tested the difference by changing the Main module for a large exe and running stack build.
It took 30s to recompile/link with gold and 45s with standard ld.

michaelpj · 2023-02-28T14:25:11Z

Great stuff.

TeofilC · 2023-02-28T15:25:22Z

Checked that 9.4.4 also has the ,("C compiler link flags","-fuse-ld=gold ") line in ghc --info

TeofilC · 2023-02-28T15:57:49Z

So, we are definitely passing -fuse-ld=gold to gcc but I'm a bit worried that the other calls to the linker might be still going via ld.bfd.

I've found this comment: https://gitlab.haskell.org/ghc/ghc/-/issues/22550#note_466656
So I'll add a commit that also adds that to the configure flags.

TeofilC · 2023-03-01T13:50:42Z

That built overnight and now I also have this line in ghc --info ,("Merge objects command","ld.gold")

builder/comp-builder.nix

angerman · 2023-03-06T03:08:58Z

@TeofilC is this ready to be merged? We do squash merge; let me know if you have any concerns with that.

TeofilC · 2023-03-06T10:04:55Z

Thanks for checking @angerman . Yeah I think this is ready. Squash merge sounds great

angerman · 2023-03-10T03:06:15Z

compiler/ghc/default.nix

+    (stdenv.targetPlatform.isLinux && !stdenv.targetPlatform.isAndroid && !stdenv.targetPlatform.isMusl) 
+    || stdenv.targetPlatform.isAarch32


After looking closer at this, I believe this is wrong. We do not unconditionally enable this in aarch32.
I believe the || stdenv.targetPlatform.isAarch32 should go.

thomasjm · 2023-03-22T02:39:21Z

Hi, this commit has actually broken my static builds with musl. This is on x64 Linux, so the isAarch32 issue isn't relevant. I now get linker errors like the following:

       > Preprocessing executable 'codedown-editor' for codedown-editor-0.1.0.0..
       > Building executable 'codedown-editor' for codedown-editor-0.1.0.0..
       > [1 of 2] Compiling Main             ( main/Main.hs, dist/build/codedown-editor/codedown-editor-tmp/Main.o, dist/build/codedown-editor/codedown-editor-tmp/Main.dyn_o )
       > [2 of 2] Compiling Paths_codedown_editor ( dist/build/codedown-editor/autogen/Paths_codedown_editor.hs, dist/build/codedown-editor/codedown-editor-tmp/Paths_codedown_editor.o, dist/build/codedown-editor/codedown-editor-tmp/Paths_codedown_editor.dyn_o )
       > Linking dist/build/codedown-editor/codedown-editor ...
       > /nix/store/bz5jhvvyxkhngylsipv4c7v2arb4hmpi-binutils-x86_64-unknown-linux-musl-2.39/bin/ld: attempted static link of dynamic object `/nix/store/mg2frc8mybn9ga75w4mry7pmi6v6phmw-gcc-x86_64-unknown-linux-musl-11.3.0-lib/lib/libstdc++.so'
       > /nix/store/bz5jhvvyxkhngylsipv4c7v2arb4hmpi-binutils-x86_64-unknown-linux-musl-2.39/bin/ld: attempted static link of dynamic object `/nix/store/ilfgsdvk8srxfh73w8yg45b9bcscsvhj-musl-x86_64-unknown-linux-musl-1.2.3/lib/libc.so'
       > /nix/store/bz5jhvvyxkhngylsipv4c7v2arb4hmpi-binutils-x86_64-unknown-linux-musl-2.39/bin/ld: attempted static link of dynamic object `/nix/store/ilfgsdvk8srxfh73w8yg45b9bcscsvhj-musl-x86_64-unknown-linux-musl-1.2.3/lib/libc.so'
       > collect2: error: ld returned 1 exit status
       > `g++' failed in phase `Linker'. (Exit code: 1)

thomasjm · 2023-03-22T02:53:37Z

It appears that my static executable build was using ld.gold prior to this commit, as I see arguments like this in the GHC configure flags:

--with-ld=x86_64-unknown-linux-musl-ld.gold --ghc-option=-optl-fuse-ld=gold --ld-option=-fuse-ld=gold

I'm confused why this PR disables ld.gold for musl when the linked Bugzilla issue says it was fixed in 2017?

Is there a way for me to pass useLdGold=true manually in my stackProject call?

TeofilC · 2023-03-22T08:29:49Z

Hi sorry that this broke stuff for you @thomasjm ! I think I was overly cautious about not having ld.gold for musl. I'll make an MR to enable it.

Until then I think you can workaround it by using a module like:

let
  compiler-nix-name = "ghc927"
in {
  ghc.packages = pkgs.haskell-nix.compiler."${compiler-nix-name}".override { useLdGold = true};
}

I think there may be a more idiomatic way of doing this but I've done stuff similar to this in the past.

thomasjm · 2023-03-22T09:31:08Z

Thanks for the module option, I got it to accept the following:

ghc.package = pkgs.buildPackages.haskell-nix.compiler.ghc925.override { useLdGold = true; };

Unfortunately, this crashes with a scary looking segfault when trying to build GHC:

error: builder for '/nix/store/5aj8a7hrpcyvicfa9cmc32bvgwdz59xp-x86_64-unknown-linux-musl-ghc-9.2.5.drv' failed with exit code 139;                                                                                 
       last 10 log lines:                                                                                                                                                                                           
       > "inplace/bin/ghc-cabal" register libraries/ghci dist-install "/build/ghc-9.2.5/inplace/bin/ghc-stage1" "/build/ghc-9.2.5/utils/ghc-pkg/dist/build/tmp/ghc-pkg" "/nix/store/m79nmslgk5vk4zp0gi99wbh1ac24lz5w-x86_64-unknown-linux-musl-ghc-9.2.5/lib/x86_64-unknown-linux-musl-ghc-9.2.5" '' '/nix/store/m79nmslgk5vk4zp0gi99wbh1ac24lz5w-x86_64-unknown-linux-musl-ghc-9.2.5' '/nix/store/m79nmslgk5vk4zp0gi99wbh1ac24lz5w-x86_6
4-unknown-linux-musl-ghc-9.2.5/lib/x86_64-unknown-linux-musl-ghc-9.2.5' '/nix/store/hanp7rdwa6sgynaz71l5l3qf2kckrjc9-x86_64-unknown-linux-musl-ghc-9.2.5-doc/share/doc/x86_64-unknown-linux-musl-ghc/html/libraries' NO                                                                                                                                                                                                                  
       > Registering library for ghci-9.2.5..                                                                                                                                                                       
       > "inplace/bin/ghc-cabal" register libraries/libiserv dist-install "/build/ghc-9.2.5/inplace/bin/ghc-stage1" "/build/ghc-9.2.5/utils/ghc-pkg/dist/build/tmp/ghc-pkg" "/nix/store/m79nmslgk5vk4zp0gi99wbh1ac24lz5w-x86_64-unknown-linux-musl-ghc-9.2.5/lib/x86_64-unknown-linux-musl-ghc-9.2.5" '' '/nix/store/m79nmslgk5vk4zp0gi99wbh1ac24lz5w-x86_64-unknown-linux-musl-ghc-9.2.5' '/nix/store/m79nmslgk5vk4zp0gi99wbh1ac24lz5w-x
86_64-unknown-linux-musl-ghc-9.2.5/lib/x86_64-unknown-linux-musl-ghc-9.2.5' '/nix/store/hanp7rdwa6sgynaz71l5l3qf2kckrjc9-x86_64-unknown-linux-musl-ghc-9.2.5-doc/share/doc/x86_64-unknown-linux-musl-ghc/html/libraries' NO                                                                                                                                                                                                              
       > Registering library for libiserv-9.2.5..                                                                                                                                                                   
       > "inplace/bin/ghc-cabal" register compiler stage2 "/build/ghc-9.2.5/inplace/bin/ghc-stage1" "/build/ghc-9.2.5/utils/ghc-pkg/dist/build/tmp/ghc-pkg" "/nix/store/m79nmslgk5vk4zp0gi99wbh1ac24lz5w-x86_64-unknown-linux-musl-ghc-9.2.5/lib/x86_64-unknown-linux-musl-ghc-9.2.5" '' '/nix/store/m79nmslgk5vk4zp0gi99wbh1ac24lz5w-x86_64-unknown-linux-musl-ghc-9.2.5' '/nix/store/m79nmslgk5vk4zp0gi99wbh1ac24lz5w-x86_64-unknown-li
nux-musl-ghc-9.2.5/lib/x86_64-unknown-linux-musl-ghc-9.2.5' '/nix/store/hanp7rdwa6sgynaz71l5l3qf2kckrjc9-x86_64-unknown-linux-musl-ghc-9.2.5-doc/share/doc/x86_64-unknown-linux-musl-ghc/html/libraries' NO         
       > Registering library for ghc-9.2.5..                                                                                                                                                                        
       > for f in '/nix/store/m79nmslgk5vk4zp0gi99wbh1ac24lz5w-x86_64-unknown-linux-musl-ghc-9.2.5/lib/x86_64-unknown-linux-musl-ghc-9.2.5/package.conf.d'/*; do create () { touch "$1" && chmod 644 "$1" ; } && create "$f"; done                                                                                                                                                                                                       
       > "/build/ghc-9.2.5/utils/ghc-pkg/dist/build/tmp/ghc-pkg" --global-package-db "/nix/store/m79nmslgk5vk4zp0gi99wbh1ac24lz5w-x86_64-unknown-linux-musl-ghc-9.2.5/lib/x86_64-unknown-linux-musl-ghc-9.2.5/package.conf.d" recache                                                                                                                                                                                                    
       > /nix/store/a7gvj343m05j2s32xcnwr35v31ynlypr-coreutils-9.1/bin/install -c -m 755 -d "/nix/store/m79nmslgk5vk4zp0gi99wbh1ac24lz5w-x86_64-unknown-linux-musl-ghc-9.2.5/bin"                                   
       > /nix/store/kmfaajdpyyyg319vfqni5jm9wkxjmf73-stdenv-linux/setup: line 89: 492870 Segmentation fault      "$out/bin/x86_64-unknown-linux-musl-ghc-pkg" recache                                               
       For full logs, run 'nix log /nix/store/5aj8a7hrpcyvicfa9cmc32bvgwdz59xp-x86_64-unknown-linux-musl-ghc-9.2.5.drv'.

AFAICT musl support has been working fine and there's no reason to disable it, so a PR to bring back the old behavior seems like the right thing to me.

TeofilC · 2023-03-22T09:58:13Z

I've made a branch that removes the musl special casing here: https://github.com/tracsis/haskell.nix/tree/use-ld-gold-musl

I'll try to test this locally before opening an MR, and see if that fixes things

TeofilC · 2023-03-22T10:05:20Z

Are you going via pkgsMusl or pkgsStatic?

thomasjm · 2023-03-22T10:12:00Z

I use pkgsCross.musl64, I'm not familiar with the other ones.

TeofilC added 2 commits February 28, 2023 09:29

compiler/ghc: Add useLdGold option

4c42c23

comp-builder: Remove ld override

9dfebf5

TeofilC mentioned this pull request Feb 28, 2023

x86_64-linux executables with a postgresql dependency fail to link in devShell #1863

Closed

Set CONF_LD_LINKER_OPTS_STAGE2 to ensure gold gets used

ae1dc6f

TeofilC force-pushed the use-ld-gold branch from 4dc9d11 to d16b974 Compare February 28, 2023 16:07

Set LD even if not cross-compiling if we want gold

d9d344d

TeofilC force-pushed the use-ld-gold branch from d16b974 to d9d344d Compare February 28, 2023 16:09

TeofilC commented Mar 1, 2023

View reviewed changes

builder/comp-builder.nix Show resolved Hide resolved

TeofilC added 6 commits March 5, 2023 03:01

set full path of ld.gold

19693d2

ifdLevel 1

a28a541

Don't use ld.gold on musl

5029aef

link to musl ld.gold bug

ccc3e44

ifdLevel 2

5e7b89e

ifdLevel 3

95aa886

angerman merged commit 5240aeb into input-output-hk:master Mar 7, 2023

dhess mentioned this pull request Mar 7, 2023

chore(nix): Update dependencies. hackworthltd/primer#901

Merged

angerman reviewed Mar 10, 2023

View reviewed changes

angerman mentioned this pull request Mar 10, 2023

gold only on linux, !android, !musl #1875

Merged

TeofilC mentioned this pull request Mar 22, 2023

Use ld.gold on musl #1894

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Use ld.gold in dev shells #1868

Use ld.gold in dev shells #1868

TeofilC commented Feb 28, 2023

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thomasjm commented Mar 22, 2023

		(stdenv.targetPlatform.isLinux && !stdenv.targetPlatform.isAndroid && !stdenv.targetPlatform.isMusl)
		\|\| stdenv.targetPlatform.isAarch32

Use ld.gold in dev shells #1868

Use ld.gold in dev shells #1868

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