c - 汇编成 C 代码

Question

此汇编代码:

cmp [Variable1], 10
jae AlternateBlock
call SomeFunction
jmp AfterIfBlock
cmp [Variable1], 345
jne AfterIfBlock
call SomeOtherFunction

等于此 C 代码？:

if (variable1 >= 10)
{
    goto AlternateBlock;
    SomeFunction();
    goto AfterIfBlock;
}
else if (Variable1 != 345)
{
    goto AfterIfBlock;
    SomeOtherFunction();
}

Answer 1

更简洁:

if( variable1 < 10 ) {
  SomeFunction();
} else if( variable1 == 345 ) {
  SomeOtherFunction()
}

解释:

cmp [Variable1], 10
jae AlternateBlock     ; if variable1 is >= 10 then go to alternate block
call SomeFunction      ; else fall through and call SomeFunction(). ie. when variable1 < 10
jmp AfterIfBlock       ; prevent falling through to next conditional
cmp [Variable1], 345
jne AfterIfBlock       ; if variable1 is not equal to 345 then jump to afterifblock
call SomeOtherFunction ; else fall through to call SomeOtherFunction

如果您花一些时间来理解它，您应该会发现它在语义上等同于 C 代码。也许这有帮助。

cmp [Variable1], 10
jb @f
call SomeFunction
jmp end
  @@:
cmp [Variable1], 345
jnz end
call SomeOtherFunction
  end: