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

[Jonathan Smith via llvm-dev]

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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