[Experiment] Inline "is on heap?" checks for checked write barriers

[EgorBo]

Let's see if it works out

void Test(ref object dst, object src) => dst = src;

Current codegen:

; Method Benchmark:Test(byref,System.Object):this (FullOpts)
G_M9668_IG01:
            stp     fp, lr, [sp, #-0x10]!
            mov     fp, sp
G_M9668_IG02:
            mov     x14, x1
            mov     x15, x2
            bl      CORINFO_HELP_CHECKED_ASSIGN_REF
G_M9668_IG03:
            ldp     fp, lr, [sp], #0x10
            ret     lr
; Total bytes of code: 28

New codegen:

; Method Benchmark:Test(byref,System.Object):this (FullOpts)
G_M9668_IG01:
            stp     fp, lr, [sp, #-0x10]!
            mov     fp, sp
G_M9668_IG02:
            movz    x14, #0x5788
            movk    x14, #0xD979 LSL #16
            movk    x14, #0x7FFA LSL #32
            ldp     x15, x14, [x14]
            cmp     x1, x15
            ccmp    x1, x14, z, ge
            blt     G_M9668_IG05
G_M9668_IG03:
            str     x2, [x1]
G_M9668_IG04:
            ldp     fp, lr, [sp], #0x10
            ret     lr
G_M9668_IG05:
            mov     x14, x1
            mov     x15, x2
            bl      CORINFO_HELP_ASSIGN_REF
            b       G_M9668_IG04
; Total bytes of code: 64

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[EgorBo]

@EgorBot -arm -profiler

using System.Runtime.CompilerServices;
using BenchmarkDotNet.Attributes;

public class Benchmark
{
    [Benchmark]
    public void ReturnBufferWB() => _ = Test1(default, null);

    [Benchmark]
    public void ReturnBufferWB_batch() => _ = Test2(default);

    [Benchmark]
    public void CheckedWB()
    {
        object o = null;
        Test3(ref o, null);
    }

    [MethodImpl(MethodImplOptions.NoInlining)]
    static MyStruct Test1(MyStruct ms, object o)
    {
        ms.Fld2 = o;
        return ms;
    }

    [MethodImpl(MethodImplOptions.NoInlining)]
    static MyLargeStruct Test2(MyLargeStruct ms) => ms;

    [MethodImpl(MethodImplOptions.NoInlining)]
    static void Test3(ref object dst, object src) => dst = src;
}

public struct MyStruct
{
    public object Fld1;
    public object Fld2;
    public object Fld3;
}
public struct MyLargeStruct
{
    public object Fld1;
    public object Fld2;
    public object Fld3;
    public object Fld4;
    public object Fld5;
    public object Fld6;
    public object Fld7;
    public object Fld8;
}