LLVM Passes issue: unknown pass name

[Quuxplusone]

Bugzilla Link	PR49725
Status	NEW
Importance	P normal
Reported by	Rui Reis (rui@deniable.org)
Reported on	2021-03-25 12:51:22 -0700
Last modified on	2021-08-11 22:12:27 -0700
Version	trunk
Hardware	PC Linux
CC	darcangelo.matthew@gmail.com, llvm-bugs@lists.llvm.org
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I didn't root cause the issue. However, the current 'main' branch Passes seems broken.

To reproduce, git clone current main branch. Build it, and create any sample C program. Like:

int foo() { return 0; }

int main() { foo(); return 0; }

and then run:

$ ./bin/clang -c -emit-llvm sample.c
$ ./bin/opt -load ./lib/LLVMHello.so -hello < sample.bc

./bin/opt: unknown pass name 'hello'

This will happen for any Pass we create too, and that's how I noticed it.

This works fine, if instead of the main branch, we download and build for example the latest release candidate llvm-project-llvmorg-12.0.0-rc3.tar.gz source.

The expected behavior would be:

$ ./bin/opt -load ./lib/LLVMHello.so -hello < sample.bc

Hello: foo
Hello: main

Thank you.

[Quuxplusone]

New here, but from what I found the hello pass uses the old pass manager.
Providing

   -enable-new-pm=0

along with what you have should get you what you want.

$ ./bin/clang -emit-llvm sample.c -c -o sample.bc
$ ./bin/opt -load lib/LLVMHello.so -hello -enable-new-pm=0 < sample.bc >
/dev/null
Hello: foo
Hello: main

It may be worth it to update the
https://llvm.org/docs/WritingAnLLVMPass.html#running-a-pass-with-opt section
with this flag, or add an additional banner aside from the one at the top of
the page. Not sure what the process is but I'd be happy to do this.

~ Matt