How to define and read CLI arguments for an LLVM Pass with the new Pass Manager? - plugins

Question

I'm wondering if there is a way to define, and read the value of, CLI arguments in an LLVM pass plugin? I'm basing my plugin off of banach-space/llvm-tutor, specifically InjectFuncCall. Let's say I want to pass in an argument -func=foo to say only inject into functions called foo. How exactly do I define this command-line argument?
I tried using the CommandLine 2.0 Library. And saw this Answer, but I can't get opt to recognize my argument.

Answer 1

I have found out that you can use the arguments with the new pass manager if you use opt -load yourLib.so.
In this case the command will look like this:
opt -load ./build/libHelloWorld.so -load-pass-plugin=./build/libHelloWorld.so \
-passes="hello-world" -disable-output -lists MYARG1 -lists MYARG2 ./input_for_hello.ll
Below is the full reproducible example.
HelloWorld.cpp:
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/Passes/PassBuilder.h"
#include "llvm/Passes/PassPlugin.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/CommandLine.h"
using namespace llvm;
namespace {
// Here we register the pass arguments
cl::list<std::string> Lists("lists", cl::desc("Specify names"), cl::OneOrMore);
// This method implements what the pass does
void visitor(Function &F) {
// using the pass arguments
for(auto arg: Lists) {
errs() << "arg: " << arg << "\n";
}
errs() << "(llvm-tutor) Hello from: "<< F.getName() << "\n";
errs() << "(llvm-tutor) number of arguments: " << F.arg_size() << "\n";
}
// New PM implementation
struct HelloWorld : PassInfoMixin<HelloWorld> {
// Main entry point, takes IR unit to run the pass on (&F) and the
// corresponding pass manager (to be queried if need be)
PreservedAnalyses run(Function &F, FunctionAnalysisManager &) {
visitor(F);
return PreservedAnalyses::all();
}
};
} // namespace
//-----------------------------------------------------------------------------
// New PM Registration
//-----------------------------------------------------------------------------
llvm::PassPluginLibraryInfo getHelloWorldPluginInfo() {
return {LLVM_PLUGIN_API_VERSION, "HelloWorld", LLVM_VERSION_STRING,
[](PassBuilder &PB) {
PB.registerPipelineParsingCallback(
[](StringRef Name, FunctionPassManager &FPM,
ArrayRef<PassBuilder::PipelineElement>) {
if (Name == "hello-world") {
FPM.addPass(HelloWorld());
return true;
}
return false;
});
}};
}
// This is the core interface for pass plugins. It guarantees that 'opt' will
// be able to recognize HelloWorld when added to the pass pipeline on the
// command line, i.e. via '-passes=hello-world'
extern "C" LLVM_ATTRIBUTE_WEAK ::llvm::PassPluginLibraryInfo
llvmGetPassPluginInfo() {
return getHelloWorldPluginInfo();
}
CMakeLists.txt:
cmake_minimum_required(VERSION 3.13.4)
project(llvm-tutor-hello-world)
#===============================================================================
# 1. LOAD LLVM CONFIGURATION
#===============================================================================
# Set this to a valid LLVM installation dir
set(LT_LLVM_INSTALL_DIR "" CACHE PATH "LLVM installation directory")
# Add the location of LLVMConfig.cmake to CMake search paths (so that
# find_package can locate it)
list(APPEND CMAKE_PREFIX_PATH "${LT_LLVM_INSTALL_DIR}/lib/cmake/llvm/")
# FIXME: This is a warkaround for #25. Remove once resolved and use
# find_package(LLVM 11.0.0 REQUIRED CONFIG) instead.
find_package(LLVM REQUIRED CONFIG)
# HelloWorld includes headers from LLVM - update the include paths accordingly
include_directories(SYSTEM ${LLVM_INCLUDE_DIRS})
#===============================================================================
# 2. LLVM-TUTOR BUILD CONFIGURATION
#===============================================================================
# Use the same C++ standard as LLVM does
set(CMAKE_CXX_STANDARD 14 CACHE STRING "")
# LLVM is normally built without RTTI. Be consistent with that.
if(NOT LLVM_ENABLE_RTTI)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-rtti")
endif()
#===============================================================================
# 3. ADD THE TARGET
#===============================================================================
add_library(HelloWorld SHARED HelloWorld.cpp)
# Allow undefined symbols in shared objects on Darwin (this is the default
# behaviour on Linux)
target_link_libraries(HelloWorld
"$<$<PLATFORM_ID:Darwin>:-undefined dynamic_lookup>")
input_for_hello.ll:
; ModuleID = '../inputs/input_for_hello.c'
source_filename = "../inputs/input_for_hello.c"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"
; Function Attrs: mustprogress nofree norecurse nosync nounwind readnone uwtable willreturn
define dso_local i32 #foo(i32 %0) local_unnamed_addr #0 {
%2 = shl nsw i32 %0, 1
ret i32 %2
}
; Function Attrs: mustprogress nofree norecurse nosync nounwind readnone uwtable willreturn
define dso_local i32 #bar(i32 %0, i32 %1) local_unnamed_addr #0 {
%3 = shl i32 %1, 2
%4 = add nsw i32 %3, %0
ret i32 %4
}
; Function Attrs: mustprogress nofree norecurse nosync nounwind readnone uwtable willreturn
define dso_local i32 #fez(i32 %0, i32 %1, i32 %2) local_unnamed_addr #0 {
%4 = shl i32 %1, 2
%5 = add nsw i32 %4, %0
%6 = shl nsw i32 %5, 1
%7 = mul nsw i32 %2, 3
%8 = add i32 %7, %0
%9 = add i32 %8, %6
ret i32 %9
}
; Function Attrs: mustprogress nofree norecurse nosync nounwind readnone uwtable willreturn
define dso_local i32 #main(i32 %0, i8** nocapture readnone %1) local_unnamed_addr #0 {
ret i32 12915
}
attributes #0 = { mustprogress nofree norecurse nosync nounwind readnone uwtable willreturn "frame-pointer"="none" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
!llvm.module.flags = !{!0, !1}
!llvm.ident = !{!2}
!0 = !{i32 1, !"wchar_size", i32 4}
!1 = !{i32 7, !"uwtable", i32 1}
!2 = !{!"Ubuntu clang version 13.0.1-++20220120110924+75e33f71c2da-1~exp1~20220120231001.58"}
Build steps:
rm -rf ./build
mkdir "build"
cd build || exit
cmake ..
cmake --build .
Run the pass:
opt -load ./build/libHelloWorld.so -load-pass-plugin=./build/libHelloWorld.so \
-passes="hello-world" -disable-output -lists MYARG1 -lists MYARG2 ./input_for_hello.ll
Output:
arg: MYARG1
arg: MYARG2
(llvm-tutor) Hello from: foo
(llvm-tutor) number of arguments: 1
arg: MYARG1
arg: MYARG2
(llvm-tutor) Hello from: bar
(llvm-tutor) number of arguments: 2
arg: MYARG1
arg: MYARG2
(llvm-tutor) Hello from: fez
(llvm-tutor) number of arguments: 3
arg: MYARG1
arg: MYARG2
(llvm-tutor) Hello from: main
(llvm-tutor) number of arguments: 2