翻譯的比較爛 個人文筆和英語都不太好 歡迎大家指點；）
Lesson 1
第一課
The first little example gets us started. It is a simple function in Pascal with multiplies an integer with the constant 2.
第一課從一個小例子開始，一個用PASCAL寫的乘2函數
function MulInt2(I : Integer) : Integer;
begin
Result := I * 2;
end;
Lets steal the BASM from the CPU view. I compiled with optimizations turned on.
讓我們在CPU 觀察窗口中查看BASM代碼 我的編譯最優化已經開啓
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.
從這裏我們可以看到 函數調用在eax和他的結果調用也在eax 這是爲規定來自delphi默認的Register調用規定。實際代碼非常簡單,乘兩次2就是自身增加兩次 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.
觀察這個函數的內聯彙編代碼
Let us take a look at the calling code.
讓我們調用一下代碼
This is the Pascal code
調用的PASCAL代碼如下
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.
在調用STRTOINT後的調用了我們MuInt2_BASM2的函數,我在eax MulInt2_Basm2調用並返回結果到EAX中，拷貝到ESI
