long long初始化和8字节平台

Question

I am suprised to discover that under MSVS2012 with x64 plateform as target under debug mode with optimization turn off, a long long initialization can't be done in one instruction :

; long long l1 = 1;

    mov DWORD PTR _l1$[ebp], 1
    mov DWORD PTR _l1$[ebp+4], 0

As register are 8 bytes, I expected a instruction capable of doing it... is there one ?

Answer 1

Trying this in a quick console mode project that targets x64 and looking in the Disassembly window:

    long long l1 = 1;
000000013F151035  mov         qword ptr [rsp],1

Same code when targeting x86:

    long long l1 = 1;
010213EE  mov         dword ptr [l1],1  
010213F5  mov         dword ptr [ebp-8],0  

Slam dunk, you are not actually looking at the x64 build of your program. Use Build + Configuration Manager to fix this.