From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id ECB48D2F32D for ; Tue, 13 Jan 2026 23:18:05 +0000 (UTC) Subject: Re: [PATCH] llvm: enable LLVMgold.so build by adding binutils dependency To: openembedded-core@lists.openembedded.org From: "mark.yang" X-Originating-Location: Nowon-gu, Seoul, KR (27.122.242.71) X-Originating-Platform: Windows Firefox 146 User-Agent: GROUPS.IO Web Poster MIME-Version: 1.0 Date: Tue, 13 Jan 2026 15:17:57 -0800 References: <20260113225424.1208879-1-mark.yang@lge.com> In-Reply-To: <20260113225424.1208879-1-mark.yang@lge.com> Message-ID: <939.1768346277734118893@lists.openembedded.org> Content-Type: multipart/alternative; boundary="xHFKdjjuG92zsq1OuejE" List-Id: X-Webhook-Received: from 45-33-107-173.ip.linodeusercontent.com [45.33.107.173] by aws-us-west-2-korg-lkml-1.web.codeaurora.org with HTTPS for ; Tue, 13 Jan 2026 23:18:05 -0000 X-Groupsio-URL: https://lists.openembedded.org/g/openembedded-core/message/229293 --xHFKdjjuG92zsq1OuejE Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable This patch is intended for recipes that use the bfd linker instead of the l= ld linker when using LTO in a clang environment. In Yocto scarthgap, this option was enabled, allowing LTO to be used even w= hen using clang + LTO + bfd linker. While the lld linker does not require a plugin, the following plugins are r= equired when using the bfd linker. LLVMgold.so, libLTO.so We can reproduce the build by adding the following options to your local.co= nf: PREFERRED_TOOLCHAIN_TARGET =3D "clang" DISTRO_FEATURES:append =3D " ld-is-lld" require conf/distro/include/lto.inc DISTRO_FEATURES:append =3D " lto" # The settings below were taken from meta-clang. LTO:toolchain-clang:class-target =3D "${@bb.utils.contains('DISTRO_FEATURES= ', 'thin-lto', '-flto=3Dthin', '-flto -fuse-ld=3Dlld', d)}" LTO:toolchain-clang:class-nativesdk =3D "${@bb.utils.contains('DISTRO_FEATU= RES', 'thin-lto', '-flto=3Dthin', '-flto -fuse-ld=3Dlld', d)}" For example, components such as zlib force the use of the bfd linker. ( htt= ps://github.com/openembedded/openembedded-core/commit/be5856616aee1d2134e6a= edefc5fe664ad5e2a7d ) In this case, it causes the following error when building zlib: ( https://e= rrors.yoctoproject.org/Errors/Details/895736/ ) usr/bin/aarch64-oe-linux/../lib/LLVMgold.so: cannot open shared object file= : No such file or directory `/usr/bin/lib/LLVMgold.so` is a very strange path, but this is an issue to = be investigated further later. (This occurs because the clang binary is loc= ated in `/usr/bin/aarch64-oe-linux`, and the plugin searches for it using a= relative path from clang's current location.) In fact, LLVMgold.so does not exist in the sysroot. bitbake/bitbake-builds/oe-nodistro-master-nodistro-machine_qemuarm64/build/= tmp/sysroots-components $ find ./ -name "*LLVMgold*" # nothing bitbake/bitbake-builds/oe-nodistro-master-nodistro-machine_qemuarm64/build/= tmp/sysroots-components $ find ./ -name "*libLTO*" # nothing To produce this, the following configuration is required in the llvm recipe= . DEPENDS +=3D "binutils" EXTRA_OECMAKE +=3D "-DLLVM_BINUTILS_INCDIR=3D ${STAGING_INCDIR} " It existed in the clang recipe for scarthgap, but was omitted in commit htt= ps://github.com/openembedded/openembedded-core/commit/d76dc362c8e18779cc4dd= c6a778fb423c0e66a65. It seems this was missed during the process of streamlining the clang build= and separating the clang and llvm recipes. However, the following configuration already exists in llvm_git.bb. 70: PACKAGECONFIG:remove:class-native =3D "lto thin-lto" 81: PACKAGECONFIG[lto] =3D "-DLLVM_ENABLE_LTO=3DFull -DLLVM_BINUTILS_INCDIR= =3D ${STAGING_INCDIR} ,,binutils," 82: PACKAGECONFIG[thin-lto] =3D "-DLLVM_ENABLE_LTO=3DThin -DLLVM_BINUTILS_I= NCDIR=3D ${STAGING_INCDIR} ,,binutils," The `lto` and `thin-lto` settings in `PACKAGECONFIG` determine whether LTO = (Link Time Optimization) will be applied to LLVM itself. Furthermore, for `llvm-native`, `lto` or `thin-lto` settings in `PACKAGECON= FIG` are never applied because they are explicitly removed. PACKAGECONFIG:remove:class-native =3D "lto thin-lto" was added in https://g= ithub.com/openembedded/openembedded-core/commit/d76dc362c8e18779cc4ddc6a778= fb423c0e66a65. It seems that the use of LTO for LLVM/Clang itself is being avoided to redu= ce the increase in build time, which is a known disadvantage of LTO. Even if LLVM/Clang itself does not use LTO, I want to enable LTO for compon= ents that are built using LLVM/Clang. Therefore, providing the necessary tools (LLVMgold.so, libLTO.so) in the sy= sroot seems appropriate. Building with this configuration will provide the following files in the sy= sroot: bitbake/bitbake-builds/oe-nodistro-master-nodistro-machine_qemuarm64/build/= tmp/sysroots-components $ find . -name "*LLVMgold*" ./x86_64/llvm-native/usr/lib/LLVMgold.so bitbake/bitbake-builds/oe-nodistro-master-nodistro-machine_qemuarm64/build/= tmp/sysroots-components $ find . -name "*libLTO*" ./x86_64/llvm-native/usr/lib/libLTO.so.21.1 ./x86_64/llvm-native/usr/lib/libLTO.so Even after this patch, zlib will still fail with an error as it cannot find= the path to LLVMgold.so. However, this should be addressed in a future patch. As mentioned above, because the clang binary is copied to the usr/bin/aarch= 64-oe-linux/ location and provided to the sysroot, the relative path used t= o locate the plugin is incorrect. --xHFKdjjuG92zsq1OuejE Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable
This patch is intended for recipes that use the bfd linker instead of = the lld linker when using LTO in a clang environment.

In Yocto scarthgap, this option was enabled, allowing LTO to be used e= ven when using clang + LTO + bfd linker.
While the lld linker does not= require a plugin, the following plugins are required when using the bfd li= nker.
LLVMgold.so, libLTO.so
We can reproduce the build by adding the following options to you= r local.conf:
PREFERRED_TOOLCHAIN_TARGET =3D "clang"
DISTRO_FEATURES:append =3D=
 " ld-is-lld"
require conf/distro/include/lto.inc
DISTRO_FEATURES=
:append =3D " lto"
# The settings below were taken from meta-clang.LTO:toolchain-clang:class-target =3D "${@bb.utils.contains('DISTRO_FEATU=
RES', 'thin-lto', '-flto=3Dthin', '-flto -fuse-ld=3Dlld', d)}"
LTO:too=
lchain-clang:class-nativesdk =3D "${@bb.utils.contains('DISTRO_FEATURES', '=
thin-lto', '-flto=3Dthin', '-flto -fuse-ld=3Dlld', d)}"

For example, components such as zlib force the use of the bfd li= nker. (https://github.com/openembedded/openembedded-core/commit/be5856616aee1d21= 34e6aedefc5fe664ad5e2a7d)
In this case, it causes the following er= ror when building zlib: (https://errors.yoctopro= ject.org/Errors/Details/895736/)
usr/bin/aarch64-oe-linux/../lib/LLVMgold.so: cannot open shared object=
 file: No such file or directory
`/usr/bin/lib/LLVMgold.so`= is a very strange path, but this is an issue to be investigated fur= ther later. (This occurs because the clang binary is located in `/usr/bin/a= arch64-oe-linux`, and the plugin searches for it using a relative path from= clang's current location.)

In fact, LLVMgold.so does not exist = in the sysroot.
bitbake/b=
itbake-builds/oe-nodistro-master-nodistro-machine_qemuarm64/build/tmp/sysro=
ots-components $ find ./ -name "*LLVMgold*"
# nothing
bitbake/bitbake-builds/oe-nodistro-master-nodis=
tro-machine_qemuarm64/build/tmp/sysroots-components $ find ./ -name "*libLTO*"
# nothing

To produce this, the following configuration is required in the llvm = recipe.
DEPENDS +=
=3D "binutils"
EXTRA_OECMAKE +=3D =
"-DLLVM_BINUTILS_INCDIR=3D${STAGING_INCDIR}"

It existed in the clang recipe for scarthgap, but was omitted in comm= it https://github.com/o= penembedded/openembedded-core/commit/d76dc362c8e18779cc4ddc6a778fb423c0e66a= 65.
It seems this was missed during the process of streamlining the clang = build and separating the clang and llvm recipes.
 
However, the following configuration already exists in llvm_git.bb. 
70: PACKAGECONFIG:remove:class-native =3D "lto thin-lto"
81: PACKAGECONFIG[lto] =3D "-DLLVM_ENABLE_LTO=3DFull -DLLVM_BINUTILS_INCDIR=3D${STAGING_INCDIR},,binutils,"
82: PACKAGECONFIG[thin-lto] =3D "-DLLVM_ENABLE_LTO=3DThin -DLLVM_BINUTILS_INCDIR=3D${STAGING_INCDIR},,binutils,"

The `lto` and `thin-lto` settings in `PACKAGECONFIG` determine whethe= r LTO (Link Time Optimization) will be applied to LLVM itself.
Further= more, for `llvm-native`, `lto` or `thin-lto` settings in `PACKAGECONFIG` ar= e never applied because they are explicitly removed.
PACKAGECONFIG:rem= ove:class-native =3D "lto thin-lto" was added in https://github.com/openembedded/openembedded-core= /commit/d76dc362c8e18779cc4ddc6a778fb423c0e66a65.
It seems that th= e use of LTO for LLVM/Clang itself is being avoided to reduce the increase = in build time, which is a known disadvantage of LTO.

Even if LLVM/Clang itself does not use LTO, I want to enable LTO for c= omponents that are built using LLVM/Clang.
Therefore, providing the ne= cessary tools (LLVMgold.so, libLTO.so) in the sysroot seems appropriate.
 
Building with this configuration will provide the following files in t= he sysroot:
bitbake/bitbake-builds/oe-nodistro-master-nodistro-machi=
ne_qemuarm64/build/tmp/sysroots-components $ find . -name "*LLVMgold*"
./x86_64/llvm-native/usr/lib/LLVMgold.so
bitbake/bitbake-builds/oe-nodistro-master-nodis=
tro-machine_qemuarm64/build/tmp/sysroots-components $ find . -name "*libLTO*"
./x86_64/llvm-native/usr/lib/libLTO.so.21.1
./x86_64/llvm-native/usr/lib/libLTO.so
Even after this patch, zlib will still fail with an error as it cannot= find the path to LLVMgold.so.
However, this should be addressed in a = future patch.
As mentioned above, because the clang binary is copied t= o the usr/bin/aarch64-oe-linux/= location and provided to the sysroot, the relative path used to loc= ate the plugin is incorrect.


--xHFKdjjuG92zsq1OuejE--