[llvm-dev] How to debug passes

[Andrzej Warzynski via llvm-dev]

Hi Iulia,

This is really weird - the Hello pass from LLVM definitely works (I run
it occasionally for reference).

"Infinite loop" might mean that you're missing an argument - opt will
wait indefinitely until all positional argument are specified (i.e. the
*.ll file to process). I might be wrong here - that's just my experience
with opt.

Let's take a step back and focus on LLVMHello.so - could you send the
following:
1. Your input *.c (well, just copy and paste the contents here)
2. The command that you use to generate the *.ll file
3. The command that you use to run the Hello pass
4. The command that you used to build LLVM (in particular, LLVMHello.so)

Cheers,
Andrzej

On 30/09/2019 18:59, Iulia Stirb wrote:
> Hi Lorenzo,
>
> Sorry for the late answer.
>
> I am loading LLVMHello.so in the command, but, as I was explaining to
> Andrzej in the previous mail, I copy pasted in the mail another command,
> from the source article, which uses dummypass. I also registered the
> Hello pass. There is no error or warning when executing the opt load
> command, but it seems like it is doing some processing (maybe in
> infinite loop) because the command does not finish execution. It is
> strange though that the command is not displaying nothing, even though
> there is a print at the very beginning of the runOnModule function.
>
> This is the structure of my pass:
>
> classHello: publicModulePass{
> public:
> staticcharID;
> Hello() : ModulePass(ID) {
> }
>
> boolrunOnModule(Module &M) override;
>
> voidgetAnalysisUsage(AnalysisUsage &AU) constoverride{
> getAnalysisUsage(AU);
> }
>
> ...
>
> staticRegisterPass<Hello>X("hello", "Hello World Pass",
> false/* Only looks at CFG */,
> false/* Analysis Pass */);
>
> staticRegisterStandardPasses Y(
> PassManagerBuilder::EP_EarlyAsPossible,
> [](constPassManagerBuilder &Builder,
> legacy::PassManagerBase &PM) { PM.add(newHello()); });
>
> ...
>
> boolHello::runOnModule(Module &M) {
> errs() <<"Start pass: ";
>
>
> Could you please help with any ideas?
>
> Thank you.
> Kind regards,
> Iulia Stirb
>
>
>
> On Thursday, September 19, 2019, 12:32:06 AM GMT+3, Lorenzo Casalino
> <lorenzo.casalino93 at gmail.com> wrote:
>
>
>> opt -load lib­dum­my­pass.so -dum­my­pass hel­lo.ll
>>
>
> Looks like you are loading a shared library different from "LLVMHello.so".
>
> did you change the name of the compilation unit from "Hello.cpp" into
> "dummypass.cpp"?
>
>
> (As asked previously by Andrzej) did you register the dummy pass?
>
>  > RegisterPass<DummyPass> X("dummypass", "whatever");
>
>
> Is any error/warning triggered when loading the library, executing "opt" or
> during compilation?
>
>
> Could you attach the fragment containing the "DummyPass"?
>
>
> Lorenzo
>
>
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