How to tell if Mono actually uses LLVM? - mono

Question

Starting from version 5.14, Mono apparently enables use of LLVM by default (that's what mono --version tells me).
I also have installed the package llvm and I would like to know if there is a way to tell if Mono actually uses LLVM instead of its builtin JIT.
Actually I was thinking of two ways to detect this:
Using something in command line.
Using some code directly from a Mono application.
Edit 2018-10-12: Fun fact, starting from version 5.16, LLVM is not supported anymore.

Answer 1

I came to a solution. However it seems that currently Mono is very unstable on LLVM, so the C# code below is theoric (I could only check it without LLVM).
The idea
Thanks to arnt who gave me the idea to check mapped libraries.
The LLVM is loaded if the mono runtime opens a library named libmono-llvm.so.
From this, we can deduce a bash way and a C# to detect whether we're using LLVM or not.
Caution: this works only on Linux (because it uses the procfs)
Using bash
Given mono pid as $1 parameter, the following command returns 1 if LLVM is used, 0 otherwise.
find /proc/$1/map_files/ -maxdepth 1 -type l -ls | grep libmono-llvm.so | head -1 | wc -l
At runtime in C#
using System.Diagnostics;
using System.IO;
using Mono.Unix;
public static class LlvmInformation
{
private static bool? _isLlvmEnabled;
/// <summary>
/// Gets a value indicating whether Mono uses LLVM.
/// </summary>
/// <value>
/// <c>true</c> if this instance is LLVM enabled; otherwise, <c>false</c>.
/// </value>
public static bool IsLlvmEnabled
{
get
{
if (!_isLlvmEnabled.HasValue)
_isLlvmEnabled = LoadLlvmEnabled();
return _isLlvmEnabled.Value;
}
}
private static bool LoadLlvmEnabled()
{
var pid = Process.GetCurrentProcess().Id;
var mapFilesDirectory = $"/proc/{pid}/map_files";
var mapFiles = Directory.EnumerateFiles(mapFilesDirectory);
foreach (var mapFile in mapFiles)
{
var symbolicLinkInfo = new UnixSymbolicLinkInfo(mapFile);
if (symbolicLinkInfo.FileType == FileTypes.SymbolicLink
&& symbolicLinkInfo.GetContents().Name.Contains("libmono-llvm.so"))
return true;
}
return false;
}
}
Good luck with this!