Consider hand-written JIT helpers for more platforms or use portable version everywhere #67776
Description
There are some JIT helpers that are hand-written assembly but are only available on Windows-x64. The impact of these helpers can be profound, which means we might be missing benefits on non-Windows-x64 platforms.
JIT helpers as assembly with fallbacks into the VM (C++), Windows-x64 only.
| Method | Mean | Error | StdDev |
|---|---|---|---|
| CORINFO_HELP_NEWSFAST | 1.865 ns | 0.0356 ns | 0.0333 ns |
| CORINFO_HELP_BOX | 4.234 ns | 0.0396 ns | 0.0351 ns |
| CORINFO_HELP_NEWARR_1_VC | 17.932 ns | 0.0935 ns | 0.0781 ns |
| CORINFO_HELP_NEWARR_1_OBJ | 9.989 ns | 0.2062 ns | 0.1828 ns |
JIT helpers (portable) calling into the VM (C++), non-Windows platforms. Note there is no BOX portable version.
| Method | Mean | Error | StdDev |
|---|---|---|---|
| CORINFO_HELP_NEWSFAST | 2.136 ns | 0.0269 ns | 0.0238 ns |
| CORINFO_HELP_NEWARR_1_VC | 17.999 ns | 0.2288 ns | 0.2028 ns |
| CORINFO_HELP_NEWARR_1_OBJ | 10.001 ns | 0.1342 ns | 0.1190 ns |
JIT helpers in the VM (C++). Collected on Windows-x64 for relative performance impact.
| Method | Mean | Error | StdDev |
|---|---|---|---|
| CORINFO_HELP_NEWSFAST | 12.84 ns | 0.309 ns | 0.402 ns |
| CORINFO_HELP_BOX | 15.50 ns | 0.316 ns | 0.363 ns |
| CORINFO_HELP_NEWARR_1_VC | 30.37 ns | 0.243 ns | 0.190 ns |
| CORINFO_HELP_NEWARR_1_OBJ | 23.83 ns | 0.262 ns | 0.219 ns |
It could be possible to write the JIT helpers with new intrinsics as IL instead of assembly on all the platforms.
See the dynamic update for JIT helper:
runtime/src/coreclr/vm/jitinterfacegen.cpp
Lines 86 to 90 in ff6abfe
using System;
using System.Security.Cryptography;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
class Program
{
static void Main(string[] args)
{
var summary = BenchmarkRunner.Run<JITHelpers>(args: args);
}
}
public struct VC
{
public int A;
public float B;
public object C;
}
public class C
{
public int A;
}
public class JITHelpers
{
private VC _vc;
public JITHelpers()
{
_vc = new VC() { A = 10, B = .1f, C = this };
}
[Benchmark]
public C CORINFO_HELP_NEWSFAST() => new C();
[Benchmark]
public object CORINFO_HELP_BOX() => (object)_vc;
[Benchmark]
public VC[] CORINFO_HELP_NEWARR_1_VC() => new VC[32];
[Benchmark]
public C[] CORINFO_HELP_NEWARR_1_OBJ() => new C[32];
}/cc @davidwrighton