llvm dev - Jan 2014 - [LLVMdev] Do all user-written passes have to be run through a PassManager object (called from outside the LLVM infrastructure)?

I have written several passes that have no pre-requisites for any 
previous LLVM native passes prior to my own. For those passes, I have verified
that at
least the following two approaches are equivalent in terms of executing
those self-written passes and getting the correct results:

                        #if METHOD_1
                             PassManager PM;
                             PM.add(new Analyzeind(F));
                             PM.run(*M);
                        #else //METHOD_2
                             AnalyzeKind *abk = new AnalyzeKind(F);
                             abk->runOnFunction(*F);
                        #endif

However, I found that if my own pass has requirements, e.g.   

                         AU.addRequired<DominatorTree>();
                         AU.addPreserved<DominatorTree>();

Then, only method 1 can work; The following error msg was what 
I got from using method 2:

LLVM/llvm-3.3.src/include/llvm/PassAnalysisSupport.h:200: AnalysisType&
llvm::Pass::getAnalysis() const [with AnalysisType = llvm::DominatorTree]:
Assertion `Resolver && "Pass has not been inserted into a
PassManager object!"' failed.

Note: I have added
"initializeDominatorTreePass(*PassRegistry::getPassRegistry());"
      to the constructor of my own pass;

On 1/16/14 11:44 AM, Gai, Jiading wrote:
> I have written several passes that have no pre-requisites for any
> previous LLVM native passes prior to my own. For those passes, I have
verified that at
> least the following two approaches are equivalent in terms of executing
> those self-written passes and getting the correct results:
I don't know if you *must* run all passes via a PassManager, but I think 
you should.  That's how passes are designed to work, and running them 
through a PassManager provides some future-proofing benefits (e.g., if 
you add a prerequisite analysis pass to one of your passes, it will 
"just work").

-- John T.

Thanks John. Out of curiosity,  I wonder if it's possible to summarize 
the LLVMpass-specific design patterns. I.e., the software engineering 
techniques that were used to design/implement the LLVM Pass 
Infrastructure. Equivalently, this may also answer the question "Why is 
the code this way". This visibility can improve understanding and that 
is likely to improve quality as more developers are better informed.

Thanks John. Out of curiosity,  I wonder if it's possible to summarize the
LLVMpass-specific design patterns. I.e., the software engineering techniques
that were used to design/implement the LLVM Pass Infrastructure. Equivalently,
this may also answer the question "Why is the code this way". This
visibility can improve understanding and that is likely to improve quality as
more developers are better informed.
________________________________________
From: Criswell, John T
Sent: Thursday, January 16, 2014 1:29 PM
To: Gai, Jiading; llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] Do all user-written passes have to be run through a
PassManager object (called from outside the LLVM infrastructure)?

On 1/16/14 11:44 AM, Gai, Jiading wrote:
> I have written several passes that have no pre-requisites for any
> previous LLVM native passes prior to my own. For those passes, I have
verified that at
> least the following two approaches are equivalent in terms of executing
> those self-written passes and getting the correct results:
I don't know if you *must* run all passes via a PassManager, but I think
you should.  That's how passes are designed to work, and running them
through a PassManager provides some future-proofing benefits (e.g., if
you add a prerequisite analysis pass to one of your passes, it will
"just work").

-- John T.