Parse LLVM IR Code

Question

I'm following the link Parsing and Modifying LLVM IR code to read in IR file and trying to parse it. But I found no matter what input file I wrote in argument(.ll or .bc), it just won't parse file and save it into the variable.

Here's my code,

#include <iostream>
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/Function.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/IRReader.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/raw_ostream.h"

using namespace llvm;

int main(int argc, char** argv)
{
    if (argc < 2) {
        errs() << "Expected an argument - IR file name\n";
        exit(1);
    }

    LLVMContext &Context = getGlobalContext();
    SMDiagnostic Err;
    Module *Mod = ParseIRFile(argv[1], Err, Context);

    if (Mod) {
        std::cout << "Mod is not null" << std::endl;
    }
    else {
        std::cout << "Mod is null" << std::endl;
    }
    return 0;
}

By running this code with either ll or bc file it always shows Mod is null.

Can someone give me some hints on how to reslove this issue?

Here is my IR code

; ModuleID = 'bubble.bc'
target datalayout = "e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.9.0"

@Sort = global [8 x i32] [i32 1, i32 4, i32 2, i32 5, i32 7, i32 3, i32 6, i32 3],  align 16
@.str = private unnamed_addr constant [4 x i8] c"%d \00", align 1
@.str1 = private unnamed_addr constant [2 x i8] c"\0A\00", align 1

; Function Attrs: nounwind ssp uwtable
define void @bubble() #0 {
  %tmp = alloca i32, align 4
  %i = alloca i32, align 4
  %j = alloca i32, align 4
  store i32 0, i32* %i, align 4
  br label %1

; <label>:1                                       ; preds = %41, %0
  %2 = load i32* %i, align 4
  %3 = icmp slt i32 %2, 8
  br i1 %3, label %4, label %44

; <label>:4                                       ; preds = %1
  %5 = load i32* %i, align 4
  %6 = add nsw i32 %5, 1
  store i32 %6, i32* %j, align 4
  br label %7

; <label>:7                                       ; preds = %37, %4
  %8 = load i32* %j, align 4
  %9 = icmp slt i32 %8, 8
  br i1 %9, label %10, label %40

; <label>:10                                      ; preds = %7
  %11 = load i32* %i, align 4
  %12 = sext i32 %11 to i64
  %13 = getelementptr inbounds [8 x i32]* @Sort, i32 0, i64 %12
  %14 = load i32* %13, align 4
  %15 = load i32* %j, align 4
  %16 = sext i32 %15 to i64
  %17 = getelementptr inbounds [8 x i32]* @Sort, i32 0, i64 %16
  %18 = load i32* %17, align 4
  %19 = icmp sge i32 %14, %18
  br i1 %19, label %20, label %36

//some similar stuff

!0 = metadata !{metadata !"Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)"}

Error meg is ./IRparser: /home/mingaoIrparser/testcase/bubble.ll:10:23: error: expected '{' in function body define void @bubble() #0 { ^

One more thing is that this IR is compiled from LLVM3.4 the library I'm using is 2.9 for now. Will it matter?

Answer 1

This repository has a bunch of up-to-date samples of using LLVM and Clang as libraries. For example, this sample has what you need (as well as other samples):

int main(int argc, char **argv) {
  if (argc < 2) {
    errs() << "Usage: " << argv[0] << " <IR file>\n";
    return 1;
  }

  // Parse the input LLVM IR file into a module.
  SMDiagnostic Err;
  Module *Mod = ParseIRFile(argv[1], Err, getGlobalContext());
  if (!Mod) {
    Err.print(argv[0], errs());
    return 1;
  }

  // ... use module
}