Some x86 instructions are designed to leave the content of the operands (registers) as they are and just set/unset specific internal CPU flags like the zero-flag (ZF). You can think at the ZF as a true/false boolean flag that resides inside the CPU. in this particular case, TEST instruction performs a bitwise logical AND, discards the actual result and sets/unsets the ZF according to the result of the logical and: if the result is zero it sets ZF = 1, otherwise it sets ZF = 0. Conditional jump instructions like JE are designed to look at the ZF for jumping/notjumping so using TEST and JE together is equivalent to perform a conditional jump based on the value of a specific register: example:

TEST EAX,EAX
JE some_address

当且仅当ZF = 1时，CPU将跳转到“some_address”，换句话说，当且仅当and (EAX,EAX) = 0，当且仅当EAX == 0时，它才会发生 等价的C代码是:

if(eax == 0)
{
    goto some_address
}

Some x86 instructions are designed to leave the content of the operands (registers) as they are and just set/unset specific internal CPU flags like the zero-flag (ZF). You can think at the ZF as a true/false boolean flag that resides inside the CPU. in this particular case, TEST instruction performs a bitwise logical AND, discards the actual result and sets/unsets the ZF according to the result of the logical and: if the result is zero it sets ZF = 1, otherwise it sets ZF = 0. Conditional jump instructions like JE are designed to look at the ZF for jumping/notjumping so using TEST and JE together is equivalent to perform a conditional jump based on the value of a specific register: example:

TEST EAX,EAX
JE some_address

当且仅当ZF = 1时，CPU将跳转到“some_address”，换句话说，当且仅当and (EAX,EAX) = 0，当且仅当EAX == 0时，它才会发生 等价的C代码是:

if(eax == 0)
{
    goto some_address
}

Test是非破坏性的，它不返回操作的结果，但它相应地设置标志寄存器。要了解它真正测试的是什么，您需要检查以下说明。out通常用于检查寄存器是否为0，可能与jz条件跳转相结合。

你是对的，测试and是两个操作数。但是结果被丢弃了，唯一留下来的，也是最重要的部分，是标志。它们被设置了，这就是为什么测试指令被使用(并且存在)的原因。

JE在相等时不跳(当之前的指令是比较时它有意义)，它真正做的是，当设置ZF标志时它跳。由于它是test设置的标志之一，这个指令序列(test x,x;Je…)的意思是当x为0时，它会被跳转。

对于这样的问题(以及更多细节)，我可以推荐一本关于x86指令的书，例如，即使它真的很大，英特尔的文档也非常好和精确。

CMP减去操作数并设置标志。也就是说，如果差值为零(操作数相等)，则设置零标志。

当AND操作的结果为零时，TEST设置零标志ZF。如果两个操作数相等，当它们都为零时，它们的位与为零。TEST还设置符号标志SF(当结果中设置最高有效位时)和奇偶标志PF(当设置位的数量为偶数时)。

JE[等于则跳]测试零标志，如果设置了标志则跳。JE是JZ [Jump if Zero]的别名，因此反汇编程序不能基于操作码选择一个。JE之所以如此命名，是因为如果CMP的参数相等，则设置零标志。

So,

TEST %eax, %eax
JE   400e77 <phase_1+0x23>

如果%eax为零则跳跃。

这将检查EAX是否为零。指令测试在参数之间按位进行AND运算，如果EAX包含零，则结果设置ZF或ZeroFlag。