c# - 为什么多个班级成员分配会产生冗余装配？

Question

在玩 C# 时，我遇到了这种“奇怪的行为”。

功能

public static Vec3 f() 
{
    var v = new Vec3();

    v.x = 0;
    v.y = 0;
    v.z = 0;

    v.x = 0;
    v.y = 0;
    v.z = 0;

    v.x = 0;
    v.y = 0;
    v.z = 0;

    return v;
}

当您使用class关键字 for时Vec3，asm输出会产生冗余代码：

public class Vec3
{
    public int x;
    public int y;
    public int z;
}

汇编

C.f()
    L0000: sub rsp, 0x28
    L0004: mov rcx, 0x7ff7aaa5d040
    L000e: call 0x00007ff801dba370
    L0013: xor edx, edx
    L0015: mov [rax+8], edx
    L0018: mov [rax+0xc], edx
    L001b: mov [rax+0x10], edx
    L001e: mov [rax+8], edx      ; isn't this redundant?
    L0021: mov [rax+0xc], edx    ; isn't this redundant?
    L0024: mov [rax+0x10], edx   ; isn't this redundant?
    L0027: mov [rax+8], edx      ; isn't this redundant?
    L002a: mov [rax+0xc], edx    ; isn't this redundant?
    L002d: mov [rax+0x10], edx   ; isn't this redundant?
    L0030: add rsp, 0x28
    L0034: ret

但是 whitstruct关键字我们得到以下输出：

public struct Vec3
{
    public int x;
    public int y;
    public int z;
}

汇编

C.f()
    L0000: xor eax, eax
    L0002: mov [rcx], eax
    L0004: mov [rcx+4], eax
    L0007: mov [rcx+8], eax
    L000a: mov rax, rcx
    L000d: ret

问题

那些装配线不是多余的吗？如果没有，你能解释一下为什么吗？

笔记

我知道class并且struct不一样。问题是关于多MOV条指令。

标签： c#assemblyx86-64disassembly