翻译的比较烂 个人文笔和英语都不太好 欢迎大家指点；）
Lesson 1
第一课
The first little example gets us started. It is a simple function in Pascal with multiplies an integer with the constant 2.
第一课从一个小例子开始，一个用PASCAL写的乘2函数
function MulInt2(I : Integer) : Integer;
begin
Result := I * 2;
end;
Lets steal the BASM from the CPU view. I compiled with optimizations turned on.
让我们在CPU 观察窗口中查看BASM代码 我的编译最优化已经开启
function MulInt2_BASM(I : Integer) : Integer;
begin
Result := I * 2;
{
add eax,eax
ret
}
end;
From this we see that I am transferred to the function in eax and that the result is transferred back to the caller in eax too. This is the convention for the register calling convention, which is the default in Delphi. The actual code is very simple, the times 2 multiplication is obtained by adding I to itself, I+I = 2I. The ret instruction returns execution to the line after the one which called the function.
从这里我们可以看到 函数调用在eax和他的结果调用也在eax 这是为规定来自delphi默认的Register调用规定。实际代码非常简单,乘两次2就是自身增加两次 比如I+I=2I
Lets code the function as a pure asm function.
function MulInt2_BASM2(I : Integer) : Integer;
asm
//Result := I * 2;
add eax,eax
//ret
end;
Observe that the ret function is supplied by the inline assembler.
观察这个函数的内联汇编代码
Let us take a look at the calling code.
让我们调用一下代码
This is the Pascal code
调用的PASCAL代码如下
procedure TForm1.Button1Click(Sender: TObject);
var
I, J : Integer;
begin
I := StrToInt(IEdit.Text);
J := MulInt2_BASM2(I);
JEdit.Text := IntToStr(J);
end;
The important line is
重要的一行如下
J := MulInt2_BASM2(I);
From the cpu view
在CPU中看到如下
call StrToInt
call MulInt2_BASM2
mov esi,eax
After the call to StrToInt from the line before the one, which calls our function, I am in eax. (StrToInt is also following the register calling convention). MulInt2_BASM2 is called and returns the result in eax, which is copied, to esi in the next line.
在调用STRTOINT后的调用了我们MuInt2_BASM2的函数,我在eax MulInt2_Basm2调用并返回结果到EAX中，拷贝到ESI