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所以，我有以下函数来读取 EXTENDED（扩展双精度，80 位精度双精度）并作为普通 INT 输出

int read_ld( int addr )
{
    int result;
    asm volatile
    (
        "mov eax, %[addr];"
        "fld qword ptr [eax];"
        "fistp dword ptr %[result]"
        : [addr] "=m" (addr)
        : [result] "m" (result)
    );
 return result;
}

Wich 由另一个函数（任何函数）调用，但我将在此处放置出现错误的实际代码

extern "C" __declspec(dllexport) void funca()
{
    if( key(VK_PRIOR) ) //Fast
            fps_control( 0 );
    else if( key(VK_NEXT) ) //Slow
        fps_control( fps * 2 );
    else
        fps_control( fps ); //Normal
    char a[255];
    if( key(VK_HOME) )
    {
        int k = read_ld( 0x5080EC ); //This is just for testing <<
    }
}

这个用 mingw 编译的 EXACT 代码，没有特殊标志，在 funca() 处为我提供了以下程序集

  SUB     ESP, 2C
  MOV     DWORD PTR SS:[ESP], 21
  CALL    nakaeru.6FF01540           << Notice these are calls to key(), normal
  TEST    EAX, EAX
  JE L017
  MOV     DWORD PTR SS:[ESP], 0
  CALL    nakaeru.6FF014E0           << Notice these are calls to key(), normal
L007:
  MOV     DWORD PTR SS:[ESP], 24
  CALL    nakaeru.6FF01540           << Notice these are calls to key(), normal
  TEST    EAX, EAX
  JE L014
  MOV     EAX, DWORD PTR SS:[ESP+18] <<| This is my code and it is not a call
  FLD     QWORD PTR DS:[EAX]           |
  FISTP   DWORD PTR SS:[ESP+1C]        |
L014:
  ADD     ESP, 2C
  RETN
  LEA     ESI, DWORD PTR DS:[ESI]
L017:
  MOV     DWORD PTR SS:[ESP], 22
  CALL    nakaeru.6FF01540           
  TEST    EAX, EAX
  MOV     EAX, DWORD PTR DS:[6FF08000]
  JE L026
  ADD     EAX, EAX
  MOV     DWORD PTR SS:[ESP], EAX
  CALL    nakaeru.6FF014E0          
  JMP L007
L026:
  MOV     DWORD PTR SS:[ESP], EAX
  CALL    nakaeru.6FF014E0           
  JMP L007

我想知道为什么编译器会这样做...可能是某种优化或我可能缺少的某些选项吗？

提前致谢

4

0 回答 0