Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

clang-17 llvm::MachineFunctionPass::runOnFunction crash on invalid input #63422

Open
arndb opened this issue Jun 21, 2023 · 6 comments
Open

clang-17 llvm::MachineFunctionPass::runOnFunction crash on invalid input #63422

arndb opened this issue Jun 21, 2023 · 6 comments
Labels
backend:X86 crash Prefer [crash-on-valid] or [crash-on-invalid] release:fixed-in-main
Milestone
LLVM 17.0.X Release

Comments

@arndb
Copy link

arndb commented Jun 21, 2023 •
edited by VoltrexKeyva
Loading

I came across this internal error while debugging a problem in my project:

0.	Program arguments: /usr/lib/llvm-17/bin/clang -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name delay.c -function-alignment 4 -falign-loops=1 -mrelocation-model static -fno-delete-null-pointer-checks -fwarn-stack-size=2048 -mframe-pointer=none -relaxed-aliasing -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -mcmodel=kernel -target-cpu nocona -target-feature -sse -target-feature -mmx -target-feature -sse2 -target-feature -3dnow -target-feature -avx -target-feature -x87 -disable-red-zone -mskip-rax-setup -debugger-tuning=gdb -fcoverage-compilation-dir=/home/arnd/arm-soc/build/tmp86 -nostdsysteminc -nobuiltininc -D __KERNEL__ -D KBUILD_EXTRA_WARN1 -D KCONFIG_SEED=0x1110D234 -D CC_USING_NOP_MCOUNT -D CC_USING_FENTRY -D KCONFIG_SEED=0x1110D234 -D KBUILD_MODFILE=\"arch/x86/lib/delay\" -D KBUILD_BASENAME=\"delay\" -D KBUILD_MODNAME=\"delay\" -D __KBUILD_MODNAME=kmod_delay -fmacro-prefix-map=/home/arnd/arm-soc/= -Os -Werror=unknown-warning-option -Werror=ignored-optimization-argument -Werror=option-ignored -Werror=unused-command-line-argument -Wundef -Werror -Wno-sign-compare -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs -Werror=implicit-function-declaration -Werror=implicit-int -Werror=return-type -Wframe-larger-than=2048 -Wno-gnu -Wno-unused-but-set-variable -Wno-unused-const-variable -Wdeclaration-after-statement -Wvla -Wno-pointer-sign -Wcast-function-type -Werror=date-time -Werror=incompatible-pointer-types -Wextra -Wunused -Wno-unused-parameter -Wold-style-definition -Wmissing-include-dirs -Wmissing-prototypes -Wmissing-format-attribute -Wmissing-prototypes -Wno-missing-field-initializers -Wno-type-limits -Wno-unused-but-set-variable -Wno-unused-but-set-parameter -Wno-unused-const-variable -Wno-void-pointer-to-enum-cast -Wno-address-of-packed-member -Wno-frame-address -Wno-format-security -Wno-format -Wno-initializer-overrides -Wno-sign-compare -Wimplicit-fallthrough -Werror -std=gnu11 -fdebug-compilation-dir=/home/arnd/arm-soc/build/tmp86 -ferror-limit 19 -fzero-call-used-regs=used-gpr -fwrapv -fstrict-flex-arrays=3 -stack-protector 1 -mstack-alignment=8 -fcf-protection=none -fno-signed-char -fwchar-type=short -fno-signed-wchar -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -faddrsig -x c delay-aca5b8.c
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module 'delay-aca5b8.c'.
4.	Running pass 'Prologue/Epilogue Insertion & Frame Finalization' on function '@__delay'
 #0 0x0000ffff6da81568 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xcb1568)
 #1 0x0000ffff6da7f830 llvm::sys::RunSignalHandlers() (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xcaf830)
 #2 0x0000ffff6da81c4c (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xcb1c4c)
 #3 0x0000ffff776e07fc (linux-vdso.so.1+0x7fc)
 #4 0x0000ffff6defdc60 (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0x112dc60)
 #5 0x0000ffff6ddf7d2c llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0x1027d2c)
 #6 0x0000ffff6dbb8b2c llvm::FPPassManager::runOnFunction(llvm::Function&) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xde8b2c)
 #7 0x0000ffff6dbbe1ec llvm::FPPassManager::runOnModule(llvm::Module&) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xdee1ec)
 #8 0x0000ffff6dbb90a0 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xde90a0)
 #9 0x0000ffff75678160 clang::EmitBackendOutput(clang::DiagnosticsEngine&, clang::HeaderSearchOptions const&, clang::CodeGenOptions const&, clang::TargetOptions const&, clang::LangOptions const&, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream>>) (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x1918160)
#10 0x0000ffff75955690 (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x1bf5690)
#11 0x0000ffff747617d8 clang::ParseAST(clang::Sema&, bool, bool) (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0xa017d8)
#12 0x0000ffff7628b990 clang::FrontendAction::Execute() (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x252b990)
#13 0x0000ffff7621d7b4 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x24bd7b4)
#14 0x0000ffff7630163c clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x25a163c)
#15 0x0000aaab83df29d4 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/usr/lib/llvm-17/bin/clang+0x129d4)
#16 0x0000aaab83df0000 (/usr/lib/llvm-17/bin/clang+0x10000)
#17 0x0000aaab83def084 clang_main(int, char**, llvm::ToolContext const&) (/usr/lib/llvm-17/bin/clang+0xf084)
#18 0x0000aaab83dfb028 main (/usr/lib/llvm-17/bin/clang+0x1b028)
#19 0x0000ffff6c8e7780 __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#20 0x0000ffff6c8e7858 call_init ./csu/../csu/libc-start.c:128:20
#21 0x0000ffff6c8e7858 __libc_start_main ./csu/../csu/libc-start.c:368:5
#22 0x0000aaab83deccb0 _start (/usr/lib/llvm-17/bin/clang+0xccb0)
@arndb
Copy link
Author

arndb commented Jun 21, 2023

reproducer:
delay-aca5b8.c.txt
delay-aca5b8.sh.txt

@EugeneZelenko EugeneZelenko added llvm:optimizations crash Prefer [crash-on-valid] or [crash-on-invalid] and removed new issue labels Jun 21, 2023
@shafik shafik added the needs-reduction Large reproducer that should be reduced into a simpler form label Jun 21, 2023
@arndb
Copy link
Author

arndb commented Jun 27, 2023 •
edited
Loading

It looks like I can now reproduce the issue with correct source code as well, this is a reduced test case:

$ cat delay-5d0288.c
void (*delay_fn)(int);
void __delay(void) { delay_fn(1); }

$ clang-17 -c --target=x86_64-unknown-linux-gnu -O2 -x c delay-5d0288.c -fzero-call-used-regs=used-gpr
1.	<eof> parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module 'delay-5d0288.c'.
4.	Running pass 'Prologue/Epilogue Insertion & Frame Finalization' on function '@__delay'
 #0 0x0000ffff8d7f1b68 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xcb1b68)
 #1 0x0000ffff8d7efe30 llvm::sys::RunSignalHandlers() (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xcafe30)
 #2 0x0000ffff8d7482b8 (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xc082b8)
 #3 0x0000ffff974507fc (linux-vdso.so.1+0x7fc)
 #4 0x0000ffff8dc6eebc (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0x112eebc)
 #5 0x0000ffff8db68db8 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0x1028db8)
 #6 0x0000ffff8d929810 llvm::FPPassManager::runOnFunction(llvm::Function&) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xde9810)
 #7 0x0000ffff8d92eed0 llvm::FPPassManager::runOnModule(llvm::Module&) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xdeeed0)
 #8 0x0000ffff8d929d84 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xde9d84)
 #9 0x0000ffff953e9ef4 clang::EmitBackendOutput(clang::DiagnosticsEngine&, clang::HeaderSearchOptions const&, clang::CodeGenOptions const&, clang::TargetOptions const&, clang::LangOptions const&, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream> >) (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x1919ef4)
#10 0x0000ffff956ccc64 (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x1bfcc64)
#11 0x0000ffff944d2b6c clang::ParseAST(clang::Sema&, bool, bool) (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0xa02b6c)
#12 0x0000ffff96002478 clang::FrontendAction::Execute() (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x2532478)
#13 0x0000ffff95f9417c clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x24c417c)
#14 0x0000ffff96078144 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x25a8144)
#15 0x0000aaaade4f29d4 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/usr/lib/llvm-17/bin/clang+0x129d4)
#16 0x0000aaaade4f0000 (/usr/lib/llvm-17/bin/clang+0x10000)
#17 0x0000ffff95cb8838 (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x21e8838)
#18 0x0000ffff8d74802c llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xc0802c)
#19 0x0000ffff95cb7ff0 clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef> >, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*, bool*) const (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x21e7ff0)
#20 0x0000ffff95c87eec clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x21b7eec)
#21 0x0000ffff95c880f4 clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*> >&, bool) const (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x21b80f4)
#22 0x0000ffff95c9f77c clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*> >&) (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x21cf77c)
#23 0x0000aaaade4ef700 clang_main(int, char**, llvm::ToolContext const&) (/usr/lib/llvm-17/bin/clang+0xf700)
#24 0x0000aaaade4fb028 main (/usr/lib/llvm-17/bin/clang+0x1b028)
#25 0x0000ffff8c657780 __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#26 0x0000ffff8c657858 call_init ./csu/../csu/libc-start.c:128:20
#27 0x0000ffff8c657858 __libc_start_main ./csu/../csu/libc-start.c:368:5
#28 0x0000aaaade4eccb0 _start (/usr/lib/llvm-17/bin/clang+0xccb0)
clang-17: error: clang frontend command failed with exit code 139 (use -v to see invocation)
Debian clang version 17.0.0 (++20230624112259+eaaacc3c651e-1~exp1~20230624112316.43)

@ambasta ambasta mentioned this issue Sep 28, 2023
Closed
@MaskRay
Copy link
Member

MaskRay commented Sep 28, 2023

Fixed in main branch by [PEI] Don't zero out noreg operands.

/cherry-pick f800c1f

@MaskRay MaskRay added release:fixed-in-main backend:X86 and removed needs-reduction Large reproducer that should be reduced into a simpler form llvm:optimizations labels Sep 28, 2023
@MaskRay MaskRay added this to the LLVM 17.0.X Release milestone Sep 28, 2023
@github-project-automation github-project-automation bot moved this to Needs Triage in LLVM Release Status Sep 28, 2023
@llvmbot
Copy link
Member

llvmbot commented Sep 28, 2023

@llvm/issue-subscribers-backend-x86

I came across this internal error while debugging a problem in my project: 
0.	Program arguments: /usr/lib/llvm-17/bin/clang -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name delay.c -function-alignment 4 -falign-loops=1 -mrelocation-model static -fno-delete-null-pointer-checks -fwarn-stack-size=2048 -mframe-pointer=none -relaxed-aliasing -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -mcmodel=kernel -target-cpu nocona -target-feature -sse -target-feature -mmx -target-feature -sse2 -target-feature -3dnow -target-feature -avx -target-feature -x87 -disable-red-zone -mskip-rax-setup -debugger-tuning=gdb -fcoverage-compilation-dir=/home/arnd/arm-soc/build/tmp86 -nostdsysteminc -nobuiltininc -D __KERNEL__ -D KBUILD_EXTRA_WARN1 -D KCONFIG_SEED=0x1110D234 -D CC_USING_NOP_MCOUNT -D CC_USING_FENTRY -D KCONFIG_SEED=0x1110D234 -D KBUILD_MODFILE=\"arch/x86/lib/delay\" -D KBUILD_BASENAME=\"delay\" -D KBUILD_MODNAME=\"delay\" -D __KBUILD_MODNAME=kmod_delay -fmacro-prefix-map=/home/arnd/arm-soc/= -Os -Werror=unknown-warning-option -Werror=ignored-optimization-argument -Werror=option-ignored -Werror=unused-command-line-argument -Wundef -Werror -Wno-sign-compare -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs -Werror=implicit-function-declaration -Werror=implicit-int -Werror=return-type -Wframe-larger-than=2048 -Wno-gnu -Wno-unused-but-set-variable -Wno-unused-const-variable -Wdeclaration-after-statement -Wvla -Wno-pointer-sign -Wcast-function-type -Werror=date-time -Werror=incompatible-pointer-types -Wextra -Wunused -Wno-unused-parameter -Wold-style-definition -Wmissing-include-dirs -Wmissing-prototypes -Wmissing-format-attribute -Wmissing-prototypes -Wno-missing-field-initializers -Wno-type-limits -Wno-unused-but-set-variable -Wno-unused-but-set-parameter -Wno-unused-const-variable -Wno-void-pointer-to-enum-cast -Wno-address-of-packed-member -Wno-frame-address -Wno-format-security -Wno-format -Wno-initializer-overrides -Wno-sign-compare -Wimplicit-fallthrough -Werror -std=gnu11 -fdebug-compilation-dir=/home/arnd/arm-soc/build/tmp86 -ferror-limit 19 -fzero-call-used-regs=used-gpr -fwrapv -fstrict-flex-arrays=3 -stack-protector 1 -mstack-alignment=8 -fcf-protection=none -fno-signed-char -fwchar-type=short -fno-signed-wchar -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -faddrsig -x c delay-aca5b8.c
1.	&lt;eof&gt; parser at end of file
2.	Code generation
3.	Running pass 'Function Pass Manager' on module 'delay-aca5b8.c'.
4.	Running pass 'Prologue/Epilogue Insertion &amp; Frame Finalization' on function '@<!-- -->__delay'
 #<!-- -->0 0x0000ffff6da81568 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xcb1568)
 #<!-- -->1 0x0000ffff6da7f830 llvm::sys::RunSignalHandlers() (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xcaf830)
 #<!-- -->2 0x0000ffff6da81c4c (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xcb1c4c)
 #<!-- -->3 0x0000ffff776e07fc (linux-vdso.so.1+0x7fc)
 #<!-- -->4 0x0000ffff6defdc60 (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0x112dc60)
 #<!-- -->5 0x0000ffff6ddf7d2c llvm::MachineFunctionPass::runOnFunction(llvm::Function&amp;) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0x1027d2c)
 #<!-- -->6 0x0000ffff6dbb8b2c llvm::FPPassManager::runOnFunction(llvm::Function&amp;) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xde8b2c)
 #<!-- -->7 0x0000ffff6dbbe1ec llvm::FPPassManager::runOnModule(llvm::Module&amp;) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xdee1ec)
 #<!-- -->8 0x0000ffff6dbb90a0 llvm::legacy::PassManagerImpl::run(llvm::Module&amp;) (/usr/lib/llvm-17/bin/../lib/libLLVM-17.so.1+0xde90a0)
 #<!-- -->9 0x0000ffff75678160 clang::EmitBackendOutput(clang::DiagnosticsEngine&amp;, clang::HeaderSearchOptions const&amp;, clang::CodeGenOptions const&amp;, clang::TargetOptions const&amp;, clang::LangOptions const&amp;, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::IntrusiveRefCntPtr&lt;llvm::vfs::FileSystem&gt;, std::unique_ptr&lt;llvm::raw_pwrite_stream, std::default_delete&lt;llvm::raw_pwrite_stream&gt;&gt;) (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x1918160)
#<!-- -->10 0x0000ffff75955690 (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x1bf5690)
#<!-- -->11 0x0000ffff747617d8 clang::ParseAST(clang::Sema&amp;, bool, bool) (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0xa017d8)
#<!-- -->12 0x0000ffff7628b990 clang::FrontendAction::Execute() (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x252b990)
#<!-- -->13 0x0000ffff7621d7b4 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&amp;) (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x24bd7b4)
#<!-- -->14 0x0000ffff7630163c clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/usr/lib/llvm-17/bin/../lib/libclang-cpp.so.17+0x25a163c)
#<!-- -->15 0x0000aaab83df29d4 cc1_main(llvm::ArrayRef&lt;char const*&gt;, char const*, void*) (/usr/lib/llvm-17/bin/clang+0x129d4)
#<!-- -->16 0x0000aaab83df0000 (/usr/lib/llvm-17/bin/clang+0x10000)
#<!-- -->17 0x0000aaab83def084 clang_main(int, char**, llvm::ToolContext const&amp;) (/usr/lib/llvm-17/bin/clang+0xf084)
#<!-- -->18 0x0000aaab83dfb028 main (/usr/lib/llvm-17/bin/clang+0x1b028)
#<!-- -->19 0x0000ffff6c8e7780 __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#<!-- -->20 0x0000ffff6c8e7858 call_init ./csu/../csu/libc-start.c:128:20
#<!-- -->21 0x0000ffff6c8e7858 __libc_start_main ./csu/../csu/libc-start.c:368:5
#<!-- -->22 0x0000aaab83deccb0 _start (/usr/lib/llvm-17/bin/clang+0xccb0)

@llvmbot
Copy link
Member

llvmbot commented Sep 28, 2023

/branch llvm/llvm-project-release-prs/issue63422

@llvmbot llvmbot mentioned this issue Sep 28, 2023
Closed
@llvmbot
Copy link
Member

llvmbot commented Sep 28, 2023

/pull-request llvm/llvm-project-release-prs#712

@tru tru moved this from Needs Triage to Needs Review in LLVM Release Status Sep 29, 2023
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Assignees
No one assigned
Labels
backend:X86 crash Prefer [crash-on-valid] or [crash-on-invalid] release:fixed-in-main
Projects
None yet
Milestone
LLVM 17.0.X Release
Development

Successfully merging a pull request may close this issue.

PR for llvm/llvm-project#63422 llvm/llvm-project-release-prs
5 participants
@MaskRay @arndb @shafik @EugeneZelenko @llvmbot