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Ginta
Apprentice
Joined: 17 Feb 2006
Posts: 152
Location: Spain
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 Posted: Mon Jul 23, 2018 3:01 am Post subject: Playing with LLVM, gold linker and CLANG |
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I installed a fresh stage3 on a chroot to play and test with LLVM, gold linker and CLANG, with the goal of testing to compile as much as possible with clang instead of gcc.
Once installed llvm and clang, I set the default compiler as clang in /etc/portage/make.conf as follows:
| Code: |
CC="clang"
CXX="clang++"
AR="llvm-ar"
NM="llvm-nm"
RANLIB="llvm-ranlib"
|
Of course, I also enabled gold linker by setting the following to binutils' environment:
| Code: | | EXTRA_ECONF="--enable-gold=default" |
Then I thought, like gcc that compiles with itself... may it be possible to compile LLVM and CLANG with CLANG? Then I ran a using | Code: | | clang[default-compiler-rt default-libcxx static-analyzer xml] |
and found some things:
a) With sys-libs/libcxxabi[libunwind] + sys-libs/libcxx[libunwind] combination makes LLVM fail compilation with undefined references.
b) With sys-libs/libcxxabi[-libunwind] + sys-libs/libcxx[-libunwind] combination LLVM compiles fine, but then clang is unusable because of: | Code: | | clang: symbol lookup error: clang: undefined symbol: _ZN4llvm3sys2fs17getMainExecutableB5cxx11EPKcPv |
I played with disabled as-needed, with using bfd linker instead of gold linker to link itself, and the result is the same, LLVM compiled ok, its executables seem to run properly, but clang is broken.
So I thought, ok, maybe I can rebuild clang with gcc and then rebuild with itself as a second stage? Then I ran
| Code: |
CC="gcc" CXX="g++" AR="ar" NM="nm" RANLIB="ranlib" LDFLAGS="${LDFLAGS} -fuse-ld=bfd" emerge -1 clang
|
And then it failed to compile with:
| Code: |
[28/1289] : && /usr/bin/g++ -march=native -O2 -pipe -fPIC -fvisibility-inlines-hidden -Werror=date-time -std=c++11 -Wall -W -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -Wdelete-non-virtual-dtor -Wno-comment -ffunction-sections -fdata-sections -fno-common -Woverloaded-virtual -fno-strict-aliasing -pedantic -Wno-long-long -fuse-ld=bfd -Wl,-O3 -Wl,--gc-sections utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangASTNodesEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangAttrEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangCommentCommandInfoEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangCommentHTMLNamedCharacterReferenceEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangCommentHTMLTagsEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangDataCollectorsEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangDiagnosticsEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangOptionDocEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangSACheckersEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/NeonEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/TableGen.cpp.o -o bin/clang-tblgen -L/usr/lib64/llvm/6/lib64 -Wl,-rpath,"\$ORIGIN/../lib64:/usr/lib64/llvm/6/lib64" /usr/lib/llvm/6/lib64/libLLVMSupport.so.6.0.1 /usr/lib/llvm/6/lib64/libLLVMTableGen.so.6.0.1 -lpthread && :
FAILED: bin/clang-tblgen
: && /usr/bin/g++ -march=native -O2 -pipe -fPIC -fvisibility-inlines-hidden -Werror=date-time -std=c++11 -Wall -W -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -Wdelete-non-virtual-dtor -Wno-comment -ffunction-sections -fdata-sections -fno-common -Woverloaded-virtual -fno-strict-aliasing -pedantic -Wno-long-long -fuse-ld=bfd -Wl,-O3 -Wl,--gc-sections utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangASTNodesEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangAttrEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangCommentCommandInfoEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangCommentHTMLNamedCharacterReferenceEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangCommentHTMLTagsEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangDataCollectorsEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangDiagnosticsEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangOptionDocEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangSACheckersEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/NeonEmitter.cpp.o utils/TableGen/CMakeFiles/clang-tblgen.dir/TableGen.cpp.o -o bin/clang-tblgen -L/usr/lib64/llvm/6/lib64 -Wl,-rpath,"\$ORIGIN/../lib64:/usr/lib64/llvm/6/lib64" /usr/lib/llvm/6/lib64/libLLVMSupport.so.6.0.1 /usr/lib/llvm/6/lib64/libLLVMTableGen.so.6.0.1 -lpthread && :
utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangAttrEmitter.cpp.o: In function `(anonymous namespace)::PragmaClangAttributeSupport::generateParsingHelpers(llvm::raw_ostream&)':
ClangAttrEmitter.cpp:(.text._ZN12_GLOBAL__N_127PragmaClangAttributeSupport22generateParsingHelpersERN4llvm11raw_ostreamE+0x997): undefined reference to `llvm::Twine::str[abi:cxx11]() const'
utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangAttrEmitter.cpp.o: In function `clang::CalculateDiagnostic(llvm::Record const&)':
ClangAttrEmitter.cpp:(.text._ZN5clangL19CalculateDiagnosticERKN4llvm6RecordE+0x7b8): undefined reference to `llvm::Twine::str[abi:cxx11]() const'
utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangDiagnosticsEmitter.cpp.o: In function `groupDiagnostics(std::vector<llvm::Record*, std::allocator<llvm::Record*> > const&, std::vector<llvm::Record*, std::allocator<llvm::Record*> > const&, std::map<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, (anonymous namespace)::GroupInfo, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, (anonymous namespace)::GroupInfo> > >&) [clone .constprop.521]':
ClangDiagnosticsEmitter.cpp:(.text._ZL16groupDiagnosticsRKSt6vectorIPN4llvm6RecordESaIS2_EES6_RSt3mapINSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEN12_GLOBAL__N_19GroupInfoESt4lessISD_ESaISt4pairIKSD_SF_EEE.constprop.521+0xf19): undefined reference to `llvm::Twine::str[abi:cxx11]() const'
utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangDiagnosticsEmitter.cpp.o: In function `clang::EmitClangDiagsDefs(llvm::RecordKeeper&, llvm::raw_ostream&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
ClangDiagnosticsEmitter.cpp:(.text._ZN5clang18EmitClangDiagsDefsERN4llvm12RecordKeeperERNS0_11raw_ostreamERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE+0x61): undefined reference to `llvm::StringRef::upper[abi:cxx11]() const'
utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangDiagnosticsEmitter.cpp.o: In function `clang::EmitClangDiagDocs(llvm::RecordKeeper&, llvm::raw_ostream&)':
ClangDiagnosticsEmitter.cpp:(.text._ZN5clang17EmitClangDiagDocsERN4llvm12RecordKeeperERNS0_11raw_ostreamE+0xcd6): undefined reference to `llvm::Twine::str[abi:cxx11]() const'
utils/TableGen/CMakeFiles/clang-tblgen.dir/NeonEmitter.cpp.o: In function `(anonymous namespace)::Intrinsic::DagEmitter::emitDag(llvm::DagInit*)':
NeonEmitter.cpp:(.text._ZN12_GLOBAL__N_19Intrinsic10DagEmitter7emitDagEPN4llvm7DagInitE+0xfda): undefined reference to `llvm::SetTheory::addOperator(llvm::StringRef, std::unique_ptr<llvm::SetTheory::Operator, std::default_delete<llvm::SetTheory::Operator> >)'
NeonEmitter.cpp:(.text._ZN12_GLOBAL__N_19Intrinsic10DagEmitter7emitDagEPN4llvm7DagInitE+0x101c): undefined reference to `llvm::SetTheory::addOperator(llvm::StringRef, std::unique_ptr<llvm::SetTheory::Operator, std::default_delete<llvm::SetTheory::Operator> >)'
NeonEmitter.cpp:(.text._ZN12_GLOBAL__N_19Intrinsic10DagEmitter7emitDagEPN4llvm7DagInitE+0x106a): undefined reference to `llvm::SetTheory::addOperator(llvm::StringRef, std::unique_ptr<llvm::SetTheory::Operator, std::default_delete<llvm::SetTheory::Operator> >)'
NeonEmitter.cpp:(.text._ZN12_GLOBAL__N_19Intrinsic10DagEmitter7emitDagEPN4llvm7DagInitE+0x10c3): undefined reference to `llvm::SetTheory::addExpander(llvm::StringRef, std::unique_ptr<llvm::SetTheory::Expander, std::default_delete<llvm::SetTheory::Expander> >)'
utils/TableGen/CMakeFiles/clang-tblgen.dir/NeonEmitter.cpp.o: In function `(anonymous namespace)::Intrinsic::DagEmitter::emitDagCall(llvm::DagInit*)':
NeonEmitter.cpp:(.text._ZN12_GLOBAL__N_19Intrinsic10DagEmitter11emitDagCallEPN4llvm7DagInitE+0x3a1): undefined reference to `llvm::Twine::str[abi:cxx11]() const'
utils/TableGen/CMakeFiles/clang-tblgen.dir/TableGen.cpp.o: In function `llvm::cl::opt<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, false, llvm::cl::parser<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >::~opt()':
TableGen.cpp:(.text._ZN4llvm2cl3optINSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEELb0ENS0_6parserIS7_EEED2Ev[_ZN4llvm2cl3optINSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEELb0ENS0_6parserIS7_EEED5Ev]+0x3): undefined reference to `vtable for llvm::cl::opt<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, false, llvm::cl::parser<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >'
utils/TableGen/CMakeFiles/clang-tblgen.dir/TableGen.cpp.o: In function `__static_initialization_and_destruction_0(int, int) [clone .constprop.52]':
TableGen.cpp:(.text.startup._Z41__static_initialization_and_destruction_0ii.constprop.52+0xc4e): undefined reference to `vtable for llvm::cl::OptionValue<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >'
TableGen.cpp:(.text.startup._Z41__static_initialization_and_destruction_0ii.constprop.52+0xc7d): undefined reference to `vtable for llvm::cl::opt<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, false, llvm::cl::parser<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >'
TableGen.cpp:(.text.startup._Z41__static_initialization_and_destruction_0ii.constprop.52+0xca5): undefined reference to `vtable for llvm::cl::parser<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >'
utils/TableGen/CMakeFiles/clang-tblgen.dir/TableGen.cpp.o: In function `llvm::cl::opt<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, false, llvm::cl::parser<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >::~opt()':
TableGen.cpp:(.text._ZN4llvm2cl3optINSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEELb0ENS0_6parserIS7_EEED0Ev[_ZN4llvm2cl3optINSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEELb0ENS0_6parserIS7_EEED5Ev]+0x3): undefined reference to `vtable for llvm::cl::opt<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, false, llvm::cl::parser<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >'
utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangOptionDocEmitter.cpp.o: In function `clang::docs::(anonymous namespace)::emitOptionName(llvm::StringRef, llvm::Record const*, llvm::raw_ostream&)':
ClangOptionDocEmitter.cpp:(.text._ZN5clang4docs12_GLOBAL__N_114emitOptionNameEN4llvm9StringRefEPKNS2_6RecordERNS2_11raw_ostreamE+0x266): undefined reference to `llvm::Twine::str[abi:cxx11]() const'
utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangOptionDocEmitter.cpp.o: In function `clang::docs::(anonymous namespace)::emitDocumentation(int, clang::docs::(anonymous namespace)::Documentation const&, llvm::Record const*, llvm::raw_ostream&)':
ClangOptionDocEmitter.cpp:(.text._ZN5clang4docs12_GLOBAL__N_117emitDocumentationEiRKNS1_13DocumentationEPKN4llvm6RecordERNS5_11raw_ostreamE+0x1f9): undefined reference to `llvm::Twine::str[abi:cxx11]() const'
ClangOptionDocEmitter.cpp:(.text._ZN5clang4docs12_GLOBAL__N_117emitDocumentationEiRKNS1_13DocumentationEPKN4llvm6RecordERNS5_11raw_ostreamE+0x40e): undefined reference to `llvm::Twine::str[abi:cxx11]() const'
collect2: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.
|
So yes, this is unsupported probably, and it is just a test playground for learning, but, since it is already out of my knowledge, any hint for successfully building clang and llvm with clang and its libc++, or is it simply not prepared for doing so (a thing I can't believe)?
Many thanks for the hints!
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virtguru
Tux's lil' helper
Joined: 14 Aug 2010
Posts: 148
Location: The Greatest Country in the World
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| Posted: Mon Jul 23, 2018 1:09 pm Post subject: |
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| Code: | | llvm::Twine::str[abi:cxx11]() const |
maybe an ABI issue , so you may have to build llvm with same compiler ? |
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Ginta
Apprentice
Joined: 17 Feb 2006
Posts: 152
Location: Spain
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| Posted: Mon Jul 23, 2018 4:01 pm Post subject: |
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I followed up with the tests, indeed, it seems a problem with libcxx:
I recompiled clang with -default-libcxx and -default-compiler-rt so it uses gcc's C++ libraries, and then I could build both, LLVM and clang with clang.
So now I am curious, because I have a kind of academic question:
If clang provides a libc++ replacement for libstdc++ why it can't be used to bootstrap itself?
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virtguru
Tux's lil' helper
Joined: 14 Aug 2010
Posts: 148
Location: The Greatest Country in the World
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| Posted: Tue Jul 24, 2018 10:06 pm Post subject: |
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I'd be interested to know the answer to that as well I don't know clang / llvm that well.
Cheers |
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Ginta
Apprentice
Joined: 17 Feb 2006
Posts: 152
Location: Spain
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| Posted: Wed Jul 25, 2018 9:28 pm Post subject: |
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I've been digging, reading and thinking.
Of course it makes sense that compiling LLVM with libc++ instead of libstdc++ will cause clang not to be buildable with gcc and libstdc++, and I am suspecting this is the cause.
I made up to this thinking, because when recompiling LLVM, then clang got unusable and I had to recompile with gcc (even I was using libstdc++), so I just thought that some other way to bootstrap it would be neccesary.
And then I found up this: https://libcxx.llvm.org/docs/UsingLibcxx.html#using-libc-with-gcc
So what I am going to try next (when I have time) is to rebuild clang with default libc++ and bootstrap it with:
| Code: |
CFLAGS="${CFLAGS} -nostdinc++ -I<libcxx-install-prefix>/include/c++/v1"
CXXFLAGS="${CFLAGS} -nostdinc++ -I<libcxx-install-prefix>/include/c++/v1"
LDFLAGS="${LDFLAGS} -nodefaultlibs -lc++ -lc++abi -lm -lc -lgcc_s -lgcc"
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And then having a clang bootstraped with gcc, hopefully I could rebuild clang with itself..
Will tell the results of the tests asap I can do them 
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Dr.Willy
Guru
Joined: 15 Jul 2007
Posts: 547
Location: NRW, Germany
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| Posted: Thu Jul 26, 2018 8:46 am Post subject: |
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I remember there being a topic about LLVM/Clang here on the forums, where people ran into similar issues.
IIRC the solution was to build llvm:5 and clang:5 using gcc and then use llvm:5 and clang:5 to build llvm:6 and clang:6 or something along those lines. |
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Ginta
Apprentice
Joined: 17 Feb 2006
Posts: 152
Location: Spain
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| Posted: Thu Jul 26, 2018 10:47 am Post subject: |
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| Dr.Willy wrote: | I remember there being a topic about LLVM/Clang here on the forums, where people ran into similar issues.
IIRC the solution was to build llvm:5 and clang:5 using gcc and then use llvm:5 and clang:5 to build llvm:6 and clang:6 or something along those lines. |
Thanks for the hint, I am currently trying what I said in my previous post, since this is about learning more than other thing, will keep you all updated, and if fails, will try what you say
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Perfect Gentleman
Veteran
Joined: 18 May 2014
Posts: 1249
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| Posted: Thu Jul 26, 2018 1:23 pm Post subject: |
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| i've to build llvm/clang with clang when i'd build llvm/clang statically. but the downfall is no possibility to build mesa with use=llvm |
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Ginta
Apprentice
Joined: 17 Feb 2006
Posts: 152
Location: Spain
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| Posted: Mon Aug 06, 2018 1:38 pm Post subject: |
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| Perfect Gentleman wrote: | | i've to build llvm/clang with clang when i'd build llvm/clang statically. but the downfall is no possibility to build mesa with use=llvm |
There is no need to build them statically, but they need to be correctly bootstrapped.
I finally made them work and compile clang with clang
Following these steps:
- Compile LLVM and CLANG with gcc like normal, paying attention to enable default-compiler-rt default-libcxx USE flags
- Backup packages in case of fire
| Code: |
quickpkg llvm clang sys-libs/libomp sys-libs/libunwind sys-libs/libcxxabi sys-libs/netbsd-csu sys-libs/libcxx sys-libs/compiler-rt sys-devel/clang-common sys-libs/compiler-rt-sanitizers sys-devel/clang-runtime # in case we need it urgently
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Prepare make.conf to make use of CLANG as system's compiler
| Code: |
CC="clang"
CXX="clang++"
AR="llvm-ar"
NM="llvm-nm"
RANLIB="llvm-ranlib"
FCFLAGS="-march=native -O2 -pipe"
CFLAGS_BASE="-march=native -O2 -pipe"
CFLAGS_LTO="-flto=thin"
CFLAGS="${CFLAGS_BASE} ${CFLAGS_LTO}"
CXXFLAGS="${CFLAGS}"
CHOST="x86_64-pc-linux-gnu"
LDFLAGS_BASE="${LDFLAGS} -march=native -Wl,--sort-common -Wl,-O3"
LDFLAGS_STRIP="-Wl,-S"
LDFLAGS_BFD="-fuse-ld=bfd"
LDFLAGS_GOLD="-fuse-ld=gold"
LDFLAGS="${LDFLAGS_BASE} ${LDFLAGS_GOLD} ${LDFLAGS_STRIP}"
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Compile LLVM with CLANG
| Code: | | emerge -1 llvm clang |
And ignore the error, because once LLVM is installed being compiled with CLang, then Clang will be broken, we'll fix this in the next step.
If LLVM fails, recompile clang's libraries without libunwind support (it will use gcc_s then, but it causes problems with some packages) and retry LLVM compilation
Recompile Clang again with GCC, but using libc++ instead of libstdc++ from glibc:
| Code: | | CC="gcc" CXX="g++" CFLAGS="-march=native -O2 -pipe -nostdinc++ -I/usr/include/c++/v1" CXXFLAGS="-march=native -O2 -pipe -nostdinc++ -I/usr/include/c++/v1" LDFLAGS="-lc++ -lc++abi -lm -lc" emerge -1 clang |
This will compile a working version of clang using the newly compiled llvm with libc++ support.
If it succedes, we can now compile clang with itself as normal:
Be aware that there are some packages failing to compile with clang (I made some patches/reports about some of them), I am still trying to recompile the whole world with clang
I will post an entry in my blog soon with a better redaction, but I hope this can help somebody while I do so.
| Quote: | | Please notice that this bootstrap process is needed whenever a new major version of LLVM and Clang is released |
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5UrNkC27BJ
n00b
Joined: 27 Mar 2022
Posts: 28
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| Posted: Thu May 12, 2022 5:11 am Post subject: |
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bumping..
I am following the clang wiki, halfway through the gcc clang build, but i am seeing multiple conversations like this one and not much recent (2020+) summary.
is there a recent/unified stage4 clang recipe thread?
| Ginta wrote: | | Perfect Gentleman wrote: | | i've to build llvm/clang with clang when i'd build llvm/clang statically. but the downfall is no possibility to build mesa with use=llvm |
There is no need to build them statically, but they need to be correctly bootstrapped.
I finally made them work and compile clang with clang
Following these steps:
- Compile LLVM and CLANG with gcc like normal, paying attention to enable default-compiler-rt default-libcxx USE flags
- Backup packages in case of fire
| Code: |
quickpkg llvm clang sys-libs/libomp sys-libs/libunwind sys-libs/libcxxabi sys-libs/netbsd-csu sys-libs/libcxx sys-libs/compiler-rt sys-devel/clang-common sys-libs/compiler-rt-sanitizers sys-devel/clang-runtime # in case we need it urgently
|
Prepare make.conf to make use of CLANG as system's compiler
| Code: |
CC="clang"
CXX="clang++"
AR="llvm-ar"
NM="llvm-nm"
RANLIB="llvm-ranlib"
FCFLAGS="-march=native -O2 -pipe"
CFLAGS_BASE="-march=native -O2 -pipe"
CFLAGS_LTO="-flto=thin"
CFLAGS="${CFLAGS_BASE} ${CFLAGS_LTO}"
CXXFLAGS="${CFLAGS}"
CHOST="x86_64-pc-linux-gnu"
LDFLAGS_BASE="${LDFLAGS} -march=native -Wl,--sort-common -Wl,-O3"
LDFLAGS_STRIP="-Wl,-S"
LDFLAGS_BFD="-fuse-ld=bfd"
LDFLAGS_GOLD="-fuse-ld=gold"
LDFLAGS="${LDFLAGS_BASE} ${LDFLAGS_GOLD} ${LDFLAGS_STRIP}"
|
Compile LLVM with CLANG
| Code: | | emerge -1 llvm clang |
And ignore the error, because once LLVM is installed being compiled with CLang, then Clang will be broken, we'll fix this in the next step.
If LLVM fails, recompile clang's libraries without libunwind support (it will use gcc_s then, but it causes problems with some packages) and retry LLVM compilation
Recompile Clang again with GCC, but using libc++ instead of libstdc++ from glibc:
| Code: | | CC="gcc" CXX="g++" CFLAGS="-march=native -O2 -pipe -nostdinc++ -I/usr/include/c++/v1" CXXFLAGS="-march=native -O2 -pipe -nostdinc++ -I/usr/include/c++/v1" LDFLAGS="-lc++ -lc++abi -lm -lc" emerge -1 clang |
This will compile a working version of clang using the newly compiled llvm with libc++ support.
If it succedes, we can now compile clang with itself as normal:
Be aware that there are some packages failing to compile with clang (I made some patches/reports about some of them), I am still trying to recompile the whole world with clang
I will post an entry in my blog soon with a better redaction, but I hope this can help somebody while I do so.
| Quote: | | Please notice that this bootstrap process is needed whenever a new major version of LLVM and Clang is released |
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Blademasterz
n00b
Joined: 08 Oct 2021
Posts: 5
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| Posted: Fri May 20, 2022 5:03 am Post subject: |
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| 5UrNkC27BJ wrote: | bumping..
I am following the clang wiki, halfway through the gcc clang build, but i am seeing multiple conversations like this one and not much recent (2020+) summary.
is there a recent/unified stage4 clang recipe thread?
| Ginta wrote: | | Perfect Gentleman wrote: | | i've to build llvm/clang with clang when i'd build llvm/clang statically. but the downfall is no possibility to build mesa with use=llvm |
There is no need to build them statically, but they need to be correctly bootstrapped.
I finally made them work and compile clang with clang
Following these steps:
- Compile LLVM and CLANG with gcc like normal, paying attention to enable default-compiler-rt default-libcxx USE flags
- Backup packages in case of fire
| Code: |
quickpkg llvm clang sys-libs/libomp sys-libs/libunwind sys-libs/libcxxabi sys-libs/netbsd-csu sys-libs/libcxx sys-libs/compiler-rt sys-devel/clang-common sys-libs/compiler-rt-sanitizers sys-devel/clang-runtime # in case we need it urgently
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Prepare make.conf to make use of CLANG as system's compiler
| Code: |
CC="clang"
CXX="clang++"
AR="llvm-ar"
NM="llvm-nm"
RANLIB="llvm-ranlib"
FCFLAGS="-march=native -O2 -pipe"
CFLAGS_BASE="-march=native -O2 -pipe"
CFLAGS_LTO="-flto=thin"
CFLAGS="${CFLAGS_BASE} ${CFLAGS_LTO}"
CXXFLAGS="${CFLAGS}"
CHOST="x86_64-pc-linux-gnu"
LDFLAGS_BASE="${LDFLAGS} -march=native -Wl,--sort-common -Wl,-O3"
LDFLAGS_STRIP="-Wl,-S"
LDFLAGS_BFD="-fuse-ld=bfd"
LDFLAGS_GOLD="-fuse-ld=gold"
LDFLAGS="${LDFLAGS_BASE} ${LDFLAGS_GOLD} ${LDFLAGS_STRIP}"
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Compile LLVM with CLANG
| Code: | | emerge -1 llvm clang |
And ignore the error, because once LLVM is installed being compiled with CLang, then Clang will be broken, we'll fix this in the next step.
If LLVM fails, recompile clang's libraries without libunwind support (it will use gcc_s then, but it causes problems with some packages) and retry LLVM compilation
Recompile Clang again with GCC, but using libc++ instead of libstdc++ from glibc:
| Code: | | CC="gcc" CXX="g++" CFLAGS="-march=native -O2 -pipe -nostdinc++ -I/usr/include/c++/v1" CXXFLAGS="-march=native -O2 -pipe -nostdinc++ -I/usr/include/c++/v1" LDFLAGS="-lc++ -lc++abi -lm -lc" emerge -1 clang |
This will compile a working version of clang using the newly compiled llvm with libc++ support.
If it succedes, we can now compile clang with itself as normal:
Be aware that there are some packages failing to compile with clang (I made some patches/reports about some of them), I am still trying to recompile the whole world with clang
I will post an entry in my blog soon with a better redaction, but I hope this can help somebody while I do so.
| Quote: | | Please notice that this bootstrap process is needed whenever a new major version of LLVM and Clang is released |
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Hello, there is clang + musl experimental overlay available,
https://github.com/clang-musl-overlay/clang-musl-overlay
You might want to look into it, thank you  |
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Ginta
Apprentice
Joined: 17 Feb 2006
Posts: 152
Location: Spain
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| Posted: Wed Jun 14, 2023 12:37 pm Post subject: |
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| 5UrNkC27BJ wrote: | bumping..
I am following the clang wiki, halfway through the gcc clang build, but i am seeing multiple conversations like this one and not much recent (2020+) summary.
is there a recent/unified stage4 clang recipe thread?
| Ginta wrote: | | Perfect Gentleman wrote: | | i've to build llvm/clang with clang when i'd build llvm/clang statically. but the downfall is no possibility to build mesa with use=llvm |
There is no need to build them statically, but they need to be correctly bootstrapped.
I finally made them work and compile clang with clang
Following these steps:
- Compile LLVM and CLANG with gcc like normal, paying attention to enable default-compiler-rt default-libcxx USE flags
- Backup packages in case of fire
| Code: |
quickpkg llvm clang sys-libs/libomp sys-libs/libunwind sys-libs/libcxxabi sys-libs/netbsd-csu sys-libs/libcxx sys-libs/compiler-rt sys-devel/clang-common sys-libs/compiler-rt-sanitizers sys-devel/clang-runtime # in case we need it urgently
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Prepare make.conf to make use of CLANG as system's compiler
| Code: |
CC="clang"
CXX="clang++"
AR="llvm-ar"
NM="llvm-nm"
RANLIB="llvm-ranlib"
FCFLAGS="-march=native -O2 -pipe"
CFLAGS_BASE="-march=native -O2 -pipe"
CFLAGS_LTO="-flto=thin"
CFLAGS="${CFLAGS_BASE} ${CFLAGS_LTO}"
CXXFLAGS="${CFLAGS}"
CHOST="x86_64-pc-linux-gnu"
LDFLAGS_BASE="${LDFLAGS} -march=native -Wl,--sort-common -Wl,-O3"
LDFLAGS_STRIP="-Wl,-S"
LDFLAGS_BFD="-fuse-ld=bfd"
LDFLAGS_GOLD="-fuse-ld=gold"
LDFLAGS="${LDFLAGS_BASE} ${LDFLAGS_GOLD} ${LDFLAGS_STRIP}"
|
Compile LLVM with CLANG
| Code: | | emerge -1 llvm clang |
And ignore the error, because once LLVM is installed being compiled with CLang, then Clang will be broken, we'll fix this in the next step.
If LLVM fails, recompile clang's libraries without libunwind support (it will use gcc_s then, but it causes problems with some packages) and retry LLVM compilation
Recompile Clang again with GCC, but using libc++ instead of libstdc++ from glibc:
| Code: | | CC="gcc" CXX="g++" CFLAGS="-march=native -O2 -pipe -nostdinc++ -I/usr/include/c++/v1" CXXFLAGS="-march=native -O2 -pipe -nostdinc++ -I/usr/include/c++/v1" LDFLAGS="-lc++ -lc++abi -lm -lc" emerge -1 clang |
This will compile a working version of clang using the newly compiled llvm with libc++ support.
If it succedes, we can now compile clang with itself as normal:
Be aware that there are some packages failing to compile with clang (I made some patches/reports about some of them), I am still trying to recompile the whole world with clang
I will post an entry in my blog soon with a better redaction, but I hope this can help somebody while I do so.
| Quote: | | Please notice that this bootstrap process is needed whenever a new major version of LLVM and Clang is released |
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Finally I've made a repository with CLang+LLVM profiles (based and extending Gentoo's ones) and also playing with Intel CET, you can make your own stage* with LLVM enabled with it.
https://github.com/StormBytePP/StormByte.Repository and I have also a little repository for some patches https://github.com/StormBytePP/StormByte.Repository.Patches
In order to enable it, follow these steps:
- Start with a vanilla stage3 for your arch (only x86/amd64)
- Update GCC with graphite enabled
- Emerge Clang (with gcc)
- Select your desired Clang enabled profile
- Update world
- emerge -e world
Hints:
- There are some packages with custom-cflags enabled (like gcc) and this is because currently gcc fails to compile with Intel CET + -march=native both enabled and this will "fix" it.
- Review <repo_dir>/profile, specially make.defaults to adapt CFLAGS to your machine (specially gcc-tricks where native flags are unrolled)
- If CMake gives you undefined references once libc++ is used (instead of libstdc++), unmerge jsoncpp and cmake and reemerge cmake (this way a new bootstrap will be started)
Feel free to test and contribute, since I do this with in my free time and it is not perfect
EDIT: If someone is going to test CET beware with https://bugs.gentoo.org/908523 if using -march=native on some CPUs!
_________________
Some people should use emerge brain on theirselves...
Last edited by Ginta on Thu Jun 15, 2023 7:11 am; edited 1 time in total |
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Juippisi
Developer
Joined: 30 Sep 2005
Posts: 724
Location: /home
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| Posted: Thu Jun 15, 2023 5:33 am Post subject: |
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^ I see you've worked hard and congratulations for that! I want to point out we have "official" llvm-only stages available,
https://www.gentoo.org/downloads/
Check the "amd64 – Advanced choices" section and "LLVM-based stage archives" or "Musl stage archives" (which has llvm-musl stage).
There's also default/linux/amd64/17.1/*clang or default/linux/amd64/17.0/musl/clang profle available with many overriding default settings. |
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Ginta
Apprentice
Joined: 17 Feb 2006
Posts: 152
Location: Spain
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| Posted: Thu Jun 15, 2023 5:34 am Post subject: |
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| Juippisi wrote: | ^ I see you've worked hard and congratulations for that! I want to point out we have "official" llvm-only stages available,
https://www.gentoo.org/downloads/
Check the "amd64 – Advanced choices" section and "LLVM-based stage archives" or "Musl stage archives" (which has llvm-musl stage).
There's also default/linux/amd64/17.1/*clang or default/linux/amd64/17.0/musl/clang profle available with many overriding default settings. |
Jep, but for this playground (and learning) I mixed no-multilib+llvm+intel CET, like this tree (based on 17.1):
| Code: |
[36] StormByte:StormByte (stable)
[37] StormByte:StormByte/intel-cet (stable)
[38] StormByte:StormByte/intel-cet/clang (stable)
[39] StormByte:StormByte/desktop/intel-cet (stable)
[40] StormByte:StormByte/desktop/intel-cet/clang (stable)
[41] StormByte:StormByte/no-multilib (stable)
[42] StormByte:StormByte/no-multilib/intel-cet (stable)
[43] StormByte:StormByte/no-multilib/intel-cet/clang (stable)
[44] StormByte:StormByte/no-multilib/desktop/intel-cet (stable)
[45] StormByte:StormByte/no-multilib/desktop/intel-cet/clang (stable)
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I done on testing up to stage5 (with Desktop functional) with profile 45, with only 2 packages built with gcc (besides gcc itself and glibc of course).
Next step is to try musl and also try to patch them to make compile with clang only (cdrtools and app-crypt/efitools)
_________________
Some people should use emerge brain on theirselves... |
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