从 wllvm 编出的 binary 获得（重新编译）未优化的 LLVM bitcode

build_unopt_bc.sh

#!/bin/bash

#
# 声明
#
# 本脚本主要来自 https://blog.xiexun.tech/linux-bc-custom-opt.html，
# 这里只是收藏一下（并做了一点点小修改）。
#
# 用法
#
# 有些代码使用 LLVM 编译的时候不允许修改优化级别（比如 Linux kernel），
# 但我们往往需要在未优化的 bitcode 上进行静态分析，下面的脚本可以自动提取
# wllvm 编译出的 binary 中包含的 bitcode，然后重新不带优化地编译所有文件，
# 再链接成一个 bitcode 文件：
#
#     make CC=wllvm # 比如产生 abc.ko
#     ./build_unopt_bc.sh abc.ko # 会重新编译得到 abc.unopt.bc
#

llvm_linker=llvm-link

function get_cmd
{
    path="$2"

    # change output file name
    awk_cmd='{
    s = "";
    ofile = 0;
    for (i = 3; i <= NF; i++)
    {
      if (ofile == 1)
      {
        s = s "'"$path"'" " ";
        ofile = 0;
      }
      else
      {
        if ($i == "-o")
           ofile = 1;
        s = s $i " ";
      }
    }
    print s }'
    cmd_line=`head -n 1 $1 | awk "$awk_cmd"`

    # output LLVM IR
    cmd_line="${cmd_line} -emit-llvm"
    # disable opt
    cmd_line="${cmd_line} -mllvm -disable-llvm-optzns"
    echo $cmd_line
    return
}

function compile_opt
{
    cmd_path="$1"
    basepath="$2"
    tmp_path="${basepath}.tmp.bc"
    output_path="${basepath}.unopt.bc"
    cmd=`get_cmd "$cmd_path" "$tmp_path"`
    cd /lib/modules/`uname -r`/build # change dir to kernel source
    eval "$cmd" #2> /dev/null
    cd -
    cmd_result=$?
    if [ ! -e "$tmp_path" ] || [ $cmd_result -ne 0 ]
    then
        exit 1
    fi
    # opt -always-inline -inline -mem2reg -simplifycfg -instcombine "$tmp_path" -o "$output_path"
    opt -mem2reg -simplifycfg "$tmp_path" -o "$output_path"
    cmd_result=$?
    if [ ! -e "$output_path" ] || [ $cmd_result -ne 0 ]
    then
        exit 1
    fi
}

while getopts ":l:" opt; do
    case $opt in
        l) llvm_linker=$OPTARG
           ;;
        \?) echo "Usage: -l <llvm-link>" 1>&2
            exit 1
            ;;
    esac
done
shift $((OPTIND-1))
from_file=$1
if [ -z "$from_file" ]
then
    echo "no input file" 1>&2
    exit 1
fi

extract-bc -l false -m $from_file
manifest="${from_file}.llvm.manifest"
if [ ! -r "$manifest" ]
then
    echo "no manifest file" 1>&2
    exit 1
fi

tmpmanifest="${from_file}.tmp.manifest"
echo -n "" > "$tmpmanifest"

cat "$manifest" |
    while read o_bc_name;
    do
        basename=`basename "${o_bc_name%.o.bc}"`
        # basename="${basename#.}"
        dir="${o_bc_name%/*}"
        basepath="${dir}/${basename}"
        if [ -z "$dir" ] && [ -z "$basename" ]
        then
            continue
        fi

        cmd_path="${basepath}.o.cmd"
        if [ ! -r "${cmd_path}" ]
        then
            echo "${cmd_path} not found"
            continue
        fi

        while [ `jobs | wc -l` -ge 8 ]
        do
            sleep 0.1
        done
        output_path="${basepath}.unopt.bc"
        compile_opt "$cmd_path" "$basepath"
        echo "$output_path"
        echo "$output_path" >> "${tmpmanifest}"
    done

while [ `jobs | wc -l` -ne 0 ]
do
    sleep 1
done

outputfile="${from_file}.unopt.bc"
$llvm_linker -o "$outputfile" `cat "${tmpmanifest}"`