Burst infinite loop

I was trying to hide some unsafe code using a handle struct and have run into an infinite loop seemingly caused by burst compiling (1.5.4) as it runs fine when is burst is off or if I remove the handle struct and use the pointer directly.

The code

Code (CSharp):

1. public unsafe struct Scorers<T>
2.     where T : unmanaged, IContext<T>
3. {
4.     private Scorer<T>* scorer;
5.  
6.     internal Scorers(Scorer<T>* scorer)
7.     {
8.         this.scorer = scorer;
9.     }
10.  
11.     public short ScorerType => this.scorer->ScorerType;
12.  
13.     [MethodImpl(MethodImplOptions.AggressiveInlining)]
14.     public float Score<TS>(ref T context)
15.         where TS : unmanaged, IScorer<T>
16.     {
17.         return ((TS*)this.scorer)->Score(ref context); // Infinite loops in burst, fine in mono
18.         return (*(TS*)this.scorer).Score(ref context); // Infinite loops in burst, fine in mono
19.         return UnsafeUtility.AsRef<TS>(this.scorer).Score(ref context); // Works fine in burst and mono
20.     }
21. }

Which is called from here

Code (CSharp):

1. float IContext<AIContext>.CustomScorers(Scorers<AIContext> scorer, ref AIContext context)
2. {
3.     return scorer.ScorerType switch
4.     {
5.         1 => scorer.Score<HasEntityInMemory>(ref context),
6.         _ => 0,
7.     };
8. }

However if I replace it with the original code before I tried to hide the pointers with a handle, it works totally fine.

Code (CSharp):

1. float IContext<AIContext>.CustomScorers(Scorer<AIContext>* scorer, ref AIContext context)
2. {
3.     return scorer->ScorerType switch
4.     {
5.         1 => ((HasEntityInMemory*)scorer)->Score(ref context),
6.         _ => 0,
7.     };
8. }

So as mentioned in comments, UnsafeUtility.AsRef also seems to work fine inside the handle struct instead.

Looking at the assembly for these 3 cases,

Code (CSharp):

1. return ((TS*)this.scorer)->Score(ref context); // Infinite loops in burst, fine in mono
2. return (*(TS*)this.scorer).Score(ref context); // Infinite loops in burst, fine in mono
3. return UnsafeUtility.AsRef<TS>(this.scorer).Score(ref context); // Works fine in burst and mono

the first two cases generate odd assembly while the third one generates the assembly I'd expect similar to the original ((HasEntityInMemory*)scorer)->Score(ref context) implementation.

I can provide burst generated code or the full standalone library privately if desired. Just in case it matters, the memory it points to is allocated using UnsafeUtility.Malloc with Allocator.Persistent.

I seem to have a workaround using UnsafeUtility.AsRef so it's not a huge deal for me, just something I thought you might want to investigate.

 

Sent you the burst generated code in a conversation, hope it helps.