DaZombieKiller / JitInspector

JIT codegen inspector for Unity

JIT Inspector

A tool for inspecting Mono JIT code in Unity.

Usage

Open the tool from the Window -> JIT Inspector View menu option.

JIT Configuration

You can configure the JIT using the following class:

#if ENABLE_MONO
using System.Text;
using System.Runtime.InteropServices;

internal static unsafe class MonoJitConfig
{
    private const string Optimizations = "-float32";

    [DllImport("__Internal")]
    private static extern void mono_jit_parse_options(int argc, byte** argv);

#if UNITY_EDITOR
    [UnityEditor.InitializeOnLoadMethod]
#else
    [UnityEngine.RuntimeInitializeOnLoadMethod(UnityEngine.RuntimeInitializeLoadType.SubsystemRegistration)]
#endif
    private static void ParseOptions()
    {
        fixed (byte* arg = Encoding.UTF8.GetBytes("-O=" + Optimizations + "\0"))
        {
            mono_jit_parse_options(1, &arg);
        }
    }
}
#endif

The Optimizations string is a comma-separated (without spaces) list of optimization passes for the JIT to perform. Prefixing an optimization with a minus (-) will disable it.

You may use all to enable all optimizations and -all to disable all optimizations.

Entries later in the list will override entries before them, meaning -branch,branch will result in branch being enabled. -all,branch will result in only branch being enabled.

Available optimization passes are:

Name	Description	Enabled By Default
peephole	Peephole postpass	Yes
branch	Branch optimizations	Yes
inline	Inline method calls	Yes
cfold	Constant folding	Yes
consprop	Constant propagation	Yes
copyprop	Copy propagation	Yes
deadce	Dead code elimination	Yes
linears	Linear scan global reg allocation	Yes
cmov	Conditional moves	Yes
shared	Emit per-domain code	No1
sched	Instruction scheduling	No
intrins	Intrinsic method implementations	Yes
tailc	Tail recursion and tailcalls	No
loop	Loop related optimizations	Yes
fcmov	Fast x86 FP compares	No
leaf	Leaf procedures and optimizations	No
aot	Usage of Ahead Of Time compiled code	Yes
precomp	Precompile all methods before executing	No1
abcrem	Array bound checks removal	No
ssapre	SSA based Partial Redundancy	No
exception	Optimize exception catch blocks	Yes
ssa	Use plain SSA form	No
float32	Use 32 bit float arithmetic if possible	No2
sse2	SSE2 instructions on x86	No
gsharedvt	Generic sharing for valuetypes	No1
gshared	Generic Sharing	Yes
simd	Simd intrinsics	Yes
unsafe	Remove bound checks and perform other dangerous changes	No1
alias-analysis	Alias analysis of locals	Yes
aggressive-inlining	Aggressive Inlining	No

¹ These optimizations are not enabled by all and must be specified manually.

² Enabled by default in Mono, disabled by default in Unity.