Poor code quality for Interlocked.{Compare}Exchange(nint) #47266
Description
C#:
using System;
using System.Runtime.CompilerServices;
using System.Threading;
static class Program
{
[MethodImpl(MethodImplOptions.AggressiveInlining |
MethodImplOptions.AggressiveOptimization)]
static void PtrAtomic(nint x)
{
Interlocked.Exchange(ref x, x);
Interlocked.CompareExchange(ref x, x, x);
}
[MethodImpl(MethodImplOptions.AggressiveInlining |
MethodImplOptions.AggressiveOptimization)]
static void IntAtomic(int x)
{
Interlocked.Exchange(ref x, x);
Interlocked.CompareExchange(ref x, x, x);
}
[MethodImpl(MethodImplOptions.AggressiveInlining |
MethodImplOptions.AggressiveOptimization)]
static void LongAtomic(long x)
{
Interlocked.Exchange(ref x, x);
Interlocked.CompareExchange(ref x, x, x);
}
}Result on .NET 5 (x64):
Program.PtrAtomic(IntPtr)
L0000: sub rsp, 0x28
L0004: mov [rsp+0x30], rcx
L0009: lea rcx, [rsp+0x30]
L000e: mov rdx, [rsp+0x30]
L0013: call 0x00007ff973089af0
L0018: lea rcx, [rsp+0x30]
L001d: mov rdx, [rsp+0x30]
L0022: mov r8, [rsp+0x30]
L0027: call 0x00007ff9730920f0
L002c: nop
L002d: add rsp, 0x28
L0031: ret
Program.IntAtomic(Int32)
L0000: mov [rsp+8], ecx
L0004: lea rax, [rsp+8]
L0009: mov edx, [rsp+8]
L000d: xchg [rax], edx
L000f: lea rdx, [rsp+8]
L0014: mov ecx, [rsp+8]
L0018: mov eax, [rsp+8]
L001c: lock cmpxchg [rdx], ecx
L0020: ret
Program.LongAtomic(Int64)
L0000: mov [rsp+8], rcx
L0005: lea rax, [rsp+8]
L000a: mov rdx, [rsp+8]
L000f: xchg [rax], rdx
L0012: lea rdx, [rsp+8]
L0017: mov rcx, [rsp+8]
L001c: mov rax, [rsp+8]
L0021: lock cmpxchg [rdx], rcx
L0026: retI would expect the JIT to expand the nint methods to the exact same code as either the int or long methods.