Fix #39

Background and solution identical to the previous patch.

README.md

@@ -440,7 +440,7 @@ to test **StaticCallCounter**:
 ```bash
 export LLVM_DIR=<installation/dir/of/llvm/12>
 # Generate an LLVM file to analyze
-$LLVM_DIR/bin/clang -O1 -emit-llvm -c <source_dir>/inputs/input_for_cc.c -o input_for_cc.bc
+$LLVM_DIR/bin/clang -emit-llvm -c <source_dir>/inputs/input_for_cc.c -o input_for_cc.bc
 # Run the pass through opt - Legacy PM
 $LLVM_DIR/bin/opt -load <build_dir>/lib/libStaticCallCounter.so -legacy-static-cc -analyze input_for_cc.bc
 ```

include/StaticCallCounter.h

@@ -29,6 +29,9 @@ struct StaticCallCounter : public llvm::AnalysisInfoMixin<StaticCallCounter> {
   using Result = ResultStaticCC;
   Result run(llvm::Module &M, llvm::ModuleAnalysisManager &);
   Result runOnModule(llvm::Module &M);
+  // Part of the official API:
+  //  https://llvm.org/docs/WritingAnLLVMNewPMPass.html#required-passes
+  static bool isRequired() { return true; }
 
 private:
   // A special type used by analysis passes to provide an address that
@@ -46,6 +49,9 @@ class StaticCallCounterPrinter
   explicit StaticCallCounterPrinter(llvm::raw_ostream &OutS) : OS(OutS) {}
   llvm::PreservedAnalyses run(llvm::Module &M,
                               llvm::ModuleAnalysisManager &MAM);
+  // Part of the official API:
+  //  https://llvm.org/docs/WritingAnLLVMNewPMPass.html#required-passes
+  static bool isRequired() { return true; }
 
 private:
   llvm::raw_ostream &OS;