how to get cfg

[6eanut]

I am new to llvm. I was recently trying to generate a cfg diagram of a c program using llvm. But there were some problems.
environment:
ubuntu@ubuntu:~/code$ uname -a Linux ubuntu 6.8.0-45-generic #45-Ubuntu SMP PREEMPT_DYNAMIC Fri Aug 30 12:26:41 UTC 2024 aarch64 aarch64 aarch64 GNU/Linux ubuntu@ubuntu:~/code$ cat /etc/os-release PRETTY_NAME="Ubuntu 24.04.1 LTS" NAME="Ubuntu" VERSION_ID="24.04" VERSION="24.04.1 LTS (Noble Numbat)" VERSION_CODENAME=noble ID=ubuntu ID_LIKE=debian HOME_URL="https://www.ubuntu.com/" SUPPORT_URL="https://help.ubuntu.com/" BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/" PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy" UBUNTU_CODENAME=noble LOGO=ubuntu-logo
test:
i wrote a c program
run the command "clang -S -emit-llvm test.c -o test.ll", and then got a test.ll successly
ubuntu@ubuntu:~/code$ opt -dot-cfg test.ll opt: Unknown command line argument '-dot-cfg'. Try: 'opt --help' opt: Did you mean '--dot-dom'?
or
ubuntu@ubuntu:~/code$ opt -passes=dot-cfg test.ll WARNING: You're attempting to print out a bitcode file. This is inadvisable as it may cause display problems. If you REALLY want to taste LLVM bitcode first-hand, you can force output with the -f' option.`

[marcauberer]

You can dump the callgraph with this command:

opt -passes=dot-callgraph -disable-output test.ll

[6eanut]

@marcauberer
Thank you for your help. My requirement is to get a cfg diagram of a c program instead of a callgraph

[6eanut]

I have solved the problem.
I installed them through apt install llvm clang graphivz.
Later, I retested it on an x86 machine and successfully generated the.dot file.

[Zhichenzzz]

I have solved the problem. I installed them through apt install llvm clang graphivz. Later, I retested it on an x86 machine and successfully generated the.dot file.

Hello! Could you please explain your command with more details? I also wanna get the Control Flow Graph. Thx!

[StevenYangCC]

How does llvm-project print the CFG for the machine code stage?

[dalvescb]

With the new passes manager you produce the CFG with
opt -passes=dot-cfg -disable-output test.ll

You can see all built-in passes here https://llvm.org/docs/Passes.html

The nature of this change has been poorly documented, commenting here for anyone else that searches for it @StevenYangCC @Zhichenzzz