LLVM run PassManager (non-legacy) - c++

Question

How do I run a non-legacy PassManager? I have tried doing the following but there is some exception thrown when trying to invalidate the analysis manager in the run function. Is there something else I should do for initialization?
llvm::AnalysisManager<Module> mm;
PassBuilder builder;
auto pm = builder.buildModuleOptimizationPipeline(PassBuilder::OptimizationLevel::O3);
pm.run(module, mm );

Answer 1

These snippets illustrate how to run and setup to run modern custom function and module pass on some .c/.cpp file... complete with a makefile. This works for LLVM 6 which is pretty recent (march 2018). It does not use the legacy pass manager.
HelloWorld.cpp:
#include <llvm/Pass.h>
#include <llvm/IR/Function.h>
#include <llvm/IR/Module.h>
#include <llvm/Support/raw_ostream.h>
namespace {
struct Hello : public llvm::FunctionPass {
static char ID;
Hello() : llvm::FunctionPass{ID} {}
bool runOnFunction(llvm::Function &F) override {
llvm::errs() << "Hello ";
llvm::errs().write_escaped(F.getName()) << "\n";
return false;
}
};
struct Hello2 : public llvm::ModulePass {
static char ID;
Hello2() : llvm::ModulePass{ID} {}
bool runOnModule(llvm::Module &M) override {
llvm::errs() << "Name of the module ", llvm::errs().write_escaped(M.getName()) << "\n";
for(auto iter = M.getFunctionList().begin(); iter != M.getFunctionList().end(); ++iter) {
llvm::errs() << "Function name:" << iter->getName() << "\n";
}
return false;
}
};
}
char Hello::ID = 0;
static llvm::RegisterPass<Hello> X("Hello",
"Hello World Pass",
false,
false
);
char Hello2::ID = 1;
static llvm::RegisterPass<Hello2> Y("Hello2",
"Hello World2 pass",
false,
false
);
Corresponding makefile:
LLVM_VERSION=
LLVM_INCLUDEDIR = `llvm-config-6.0 --includedir`
LLVM_FLAGS = `llvm-config-6.0 --cxxflags --ldflags --system-libs --libs all`
CXX = clang++-6.0
CXXFLAGS = -g -std=c++11 -O3 -I $(LLVM_INCLUDEDIR) -I $(LLVM_INCLUDEDIR)
Hello.so:
$(CXX) -fPIC $(CXXFLAGS) HelloWorld.cpp $(LLVM_FLAGS) -shared -o Hello.so
Hello: Hello.so
testfile:
clang++-6.0 -emit-llvm -c test.cpp -o test.bc
runFunctionPassOnTestFile: Hello testfile
opt-6.0 -load ./Hello.so -Hello < test.bc > /dev/null
runModulePassOnTestfile: Hello testfile
opt-6.0 -load ./Hello.so -Hello2 < test.bc > /dev/null
clean:
rm *.o *.so *.out *~
DBG:
#echo LLVM INCLUDE DIRS $(LLVM_INCLUDEDIR) $(test)
A simple file to test everything on, test.cpp:
#include <stdio.h>
#include <stdlib.h>
int a = 4;
int c = 5;
int d = 6;
int e = 7;
int bar() { int *a = (int*) malloc(4); e = 1; return 1;}
int foo() { return 2; }
int barfoo() { return 3; }
int main() {
printf("Testing testing\n");
return 0;
}