[llvm-dev] How can I use llvm::LoopInfo in the runOnModule method?

[David Greene via llvm-dev]

Interesting that we're getting a relative flood of these recently.

See here:

http://lists.llvm.org/pipermail/llvm-dev/2019-March/131346.html

I don't think one can reliably get a Function analysis pass from within
a ModulePass using the legacy pass manager.  You have to manually
construct the pass yourself.

                    -David

Jonathan Smith via llvm-dev <llvm-dev at lists.llvm.org> writes:

> It should be `LoopInfoWrapperPass` instead of just `LoopInfo`, but you
> can also get the same information if you manually construct a
> dominator tree and target info first and pass those to the LoopInfo
> constructor.
>
> On Tue, Apr 2, 2019 at 2:48 AM J Skye via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>>
>> Hi all,
>>
>>
>> I tried to have a LoopInfo object in a function pass, and add addRequired in getAnalysisUsage, and then use getAnalysis in runOnFunction(). It worked OK.
>> Now I want to have a module pass to traverse the functions, and similarly, I want to have to loop information of the functions.
>> When I did the above in runOnModule, and build the module pass, the following error popped out, and the compile did not succeed:
>>
>> [ 50%] Building CXX object src/CMakeFiles/SkeletonPass.dir/Skeleton.cpp.o
>> /home/**/Desktop/skeleton/src/Skeleton.cpp: In member function ‘virtual bool llvm::SkeletonPass::runOnModule(llvm::Module&)’:
>> /home/**/Desktop/skeleton/src/Skeleton.cpp:47:43: error: no matching function for call to ‘llvm::SkeletonPass::getAnalysis(llvm::Function*&)’
>>      LoopInfo &LI = getAnalysis<LoopInfo>(F);
>>
>> ...
>> home/**/Work/llvm-6.0.1.src/include/llvm/PassAnalysisSupport.h: In instantiation of ‘llvm::AnalysisUsage& llvm::AnalysisUsage::addRequired() [with PassClass = llvm::LoopInfo]’:
>> /home/**/Desktop/skeleton/src/Skeleton.cpp:24:38:   required from here
>> /home/**/Work/llvm-6.0.1.src/include/llvm/PassAnalysisSupport.h:67:39: error: ‘ID’ is not a member of ‘llvm::LoopInfo’
>>      return addRequiredID(PassClass::ID);
>>                                        ^
>>
>> Here is my source code:
>>
>> #include "llvm/Pass.h"
>> #include "llvm/IR/Function.h"
>> #include "llvm/IR/Module.h"
>> #include "llvm/Support/raw_ostream.h"
>> #include "llvm/IR/Dominators.h"
>> #include "llvm/Analysis/LoopInfo.h"
>>
>> namespace llvm
>> {
>>     class SkeletonPass : public ModulePass
>>     {
>>     public:
>>         static char ID;
>>         SkeletonPass() : ModulePass(ID) {}
>>         bool runOnModule(Module &M) override;
>>         virtual StringRef getPassName() const override
>>         {
>>             return "Skeleton";
>>         }
>>         virtual void getAnalysisUsage(AnalysisUsage &AU) const override {
>>             errs() << "get analysis usage method.\n";
>>             AU.addRequired<LoopInfo>();
>>         }
>>     };
>>
>>     Pass *createSkeletonPass()
>>     {
>>         return new SkeletonPass();
>>     }
>>
>>     char SkeletonPass::ID = 0;
>>     Pass *createSkeletonPass();
>>     void initializeSkeletonPass(PassRegistry &Registry);
>>
>>
>> } // namespace llvm
>>
>> using namespace llvm;
>> using namespace std;
>>
>>
>> bool SkeletonPass::runOnModule(llvm::Module &M){
>>     errs() << "=============start=============\n";
>>     auto F = M.getFunction("main");
>>     LoopInfo &LI = getAnalysis<LoopInfo>(F);
>>
>>     LI.print(errs());
>>     errs() << "==========================\n";
>> }
>>
>> static RegisterPass<SkeletonPass> X("run", "Hello world pass", false, false);
>>
>> The version of LLVM is 6.0.1, can anyone tell me the correct way to handle this in a module pass? Thanks a lot!
>>
>> Best,
>> Liu
>>
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>> llvm-dev at lists.llvm.org
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