Opt: unknown pass name 'hello'

Beginners
1

Hi. I am studying the contents of https://llvm.org/docs/WritingAnLLVMPass.html. When I enter ‘gmake’ in a build folder and then input

opt -load lib/LLVMHello.so -p=hello <hello.bc> /dev/null

an error occurs stating

opt: unknown pass name 'hello'

I don’t understand what ‘legacy’ means, but I saw an answer suggesting to remove the load option, which I did, but the same problem still occurs. When I enter

opt -load -p=helloworld <hello.bc> /dev/null

the output ‘main’ appears, but I have never created a pass called ‘helloworld’; I want to use a pass called ‘hello’. I am curious about what the problem is and how it can be solved.

2

Hi @gihyeonjeon ,

The legacy pass manager is no longer supported for the optimization pipeline (that’s what you are trying to use). Instead, you should use the new pass manager:

opt -load-pass-plugin lib/LLVMHello.so  -passes=hello-world <hello.bc>

Please make sure that your version of opt is consistent with clang that you used to generate your input file (i.e. same version of LLVM).

I’ll try to update the docs if I manage to find some spare cycles.

Hope this helps,
-Andrzej

3

Really Thanks!
But the command you provided does not work properly. The following warning message appears.

bash: syntax error near unexpected token `newline'

I suspect that the problem occurs because of the <>. After modifying the command as follows and entering it, a bug occurred. The output sentence is as follows.

Failed to load passes from 'lib/LLVMHello.so'. Request ignored.
Expected<T> must be checked before access or destruction.
Unchecked Expected<T> contained error:
Plugin entry point not found in 'lib/LLVMHello.so'. Is this a legacy plugin?PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: opt -load-pass-plugin lib/LLVMHello.so -passes=hello hello.bc
 #0 0x00006443107a83f6 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/lib/Support/Unix/Signals.inc:602:22
 #1 0x00006443107a87d5 PrintStackTraceSignalHandler(void*) /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/lib/Support/Unix/Signals.inc:675:1
 #2 0x00006443107a5e99 llvm::sys::RunSignalHandlers() /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/lib/Support/Signals.cpp:104:20
 #3 0x00006443107a7d0e SignalHandler(int) /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/lib/Support/Unix/Signals.inc:413:1
 #4 0x0000769d87042520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #5 0x0000769d870969fc __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
 #6 0x0000769d870969fc __pthread_kill_internal ./nptl/pthread_kill.c:78:10
 #7 0x0000769d870969fc pthread_kill ./nptl/pthread_kill.c:89:10
 #8 0x0000769d87042476 gsignal ./signal/../sysdeps/posix/raise.c:27:6
 #9 0x0000769d870287f3 abort ./stdlib/abort.c:81:7
#10 0x000064430cabe5f4 llvm::SmallVectorTemplateBase<llvm::PassPlugin, false>::mallocForGrow(unsigned long, unsigned long&) /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/include/llvm/ADT/SmallVector.h:444:4
#11 0x000064430cab93f7 llvm::Expected<llvm::PassPlugin>::assertIsChecked() const /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/include/llvm/Support/Error.h:714:3
#12 0x000064430cab3280 llvm::Expected<llvm::PassPlugin>::~Expected() /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/include/llvm/Support/Error.h:550:10
#13 0x000064430caa50e0 main::'lambda'(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&)::operator()(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&) const /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/tools/opt/opt.cpp:469:3
#14 0x000064430caa827d void std::__invoke_impl<void, main::'lambda'(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&)&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&>(std::__invoke_other, main::'lambda'(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&)&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&) /usr/include/c++/11/bits/invoke.h:61:67
#15 0x000064430caa7fa1 std::enable_if<is_invocable_r_v<void, main::'lambda'(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&)&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&>, void>::type std::__invoke_r<void, main::'lambda'(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&)&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&>(main::'lambda'(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&)&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&) /usr/include/c++/11/bits/invoke.h:117:5
#16 0x000064430caa7cb9 std::_Function_handler<void (std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&), main::'lambda'(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&)>::_M_invoke(std::_Any_data const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&) /usr/include/c++/11/bits/std_function.h:291:44
#17 0x000064430cab9f99 std::function<void (std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&)>::operator()(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> const&) const /usr/include/c++/11/bits/std_function.h:590:66
#18 0x000064430cac6130 llvm::cl::list<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>, bool, llvm::cl::parser<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>>>::handleOccurrence(unsigned int, llvm::StringRef, llvm::StringRef) /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/include/llvm/Support/CommandLine.h:1670:12
#19 0x00006443106b0ed2 llvm::cl::Option::addOccurrence(unsigned int, llvm::StringRef, llvm::StringRef, bool) /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/lib/Support/CommandLine.cpp:1854:1
#20 0x00006443106aa0d6 CommaSeparateAndAddOccurrence(llvm::cl::Option*, unsigned int, llvm::StringRef, llvm::StringRef, bool) /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/lib/Support/CommandLine.cpp:643:32
#21 0x00006443106aa4b4 ProvideOption(llvm::cl::Option*, llvm::StringRef, llvm::StringRef, int, char const* const*, int&) /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/lib/Support/CommandLine.cpp:683:41
#22 0x00006443106b0343 (anonymous namespace)::CommandLineParser::ParseCommandLineOptions(int, char const* const*, llvm::StringRef, llvm::raw_ostream*, bool) /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/lib/Support/CommandLine.cpp:1713:36
#23 0x00006443106aee2a llvm::cl::ParseCommandLineOptions(int, char const* const*, llvm::StringRef, llvm::raw_ostream*, char const*, bool) /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/lib/Support/CommandLine.cpp:1469:47
#24 0x000064430caa54a1 main /home/ghjeon/llvm-project-llvmorg-17.0.6/llvm/tools/opt/opt.cpp:474:30
#25 0x0000769d87029d90 __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#26 0x0000769d87029e40 call_init ./csu/../csu/libc-start.c:128:20
#27 0x0000769d87029e40 __libc_start_main ./csu/../csu/libc-start.c:379:5
#28 0x000064430ca74ee5 _start (/usr/local/bin/opt+0xa33ee5)
Aborted (core dumped)

I am still using the LLVM documentation from the previous question. I am following all the steps identically, but only modifying the final ‘opt’ command. Also, I have confirmed that both the LLVM version and the Clang version are 17.0.6.
I entered ‘gmake’ in the build directory when compiling the pass, and I am wondering if there is any problem with this process as well.

Thanks for your help!