C ++ (Embedded Assembly) 07 from the perspective of Assembly

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Embedded Assembly is a useful supplement to pure assembly files. The following situations are usually used in assembly: (1) Improve Code For example, MMX commands; (2) perform some special operations on the hardware, such as disconnection, this is common in kernel-level code. However, we will discuss some of the basics of Embedded Assembly with you. We recommend that you do experiments with me and prove everything with facts. (1) Register protection when using Embedded Assembly [CPP] View plaincopy

2. IntProcess ()
4. {
6. _ ASM
8. {
10. PUSH AX
12. Push BX
14. Push CX
16. Pop CX
18. Pop BX
20. Pop ax
22. }
24. Return1;
26. }

(2) When calling a function, you can directly use call. The returned values are transmitted using eax. Pay attention to the stack balance.[CPP]View plaincopy

2. IntAdd (IntA,IntB)
4. {
6. ReturnA + B;
8. }
12. IntProcess ()
14. {
16. IntValue = 0;
18. _ ASM
20. {
22. Push eax
24. Push 2
26. Push 3
28. Call add
30. Add ESP, 8
32. MoV value, eax
34. Pop eax
36. }
38. Return1;
40. }

(3) Pay attention to the difference between pointer and value during calculation.[CPP]View plaincopy

2. VoidProcess ()
4. {
6. IntValue = 0;
8. Int* Address = & value;
10. _ ASM
12. {
14. Push EBX
16. MoV value, 1
18. MoV EBX, address
20. MoV [EBX], 2
22. Pop EBX
24. }
28. Assert (value = 2 );
30. Return;
32. }

(4) access to global data[CPP]View plaincopy

2. Static IntGlobal = 10;
6. VoidProcess ()
8. {
10. _ ASM
12. {
14. Push eax
16. MoV eax, global
18. Add eax, 1
20. MoV global, eax
22. Pop eax
24. }
28. Assert (Global = 11 );
30. Return;
32. }

(5) loop jump[CPP]View plaincopy

2. VoidProcess ()
4. {
6. IntValue = 0;
8. _ ASM
10. {
12. Push eax
14. Start:
16. MoV eax, Value
18. Add eax, 1
20. MoV value, eax
22. CMP value, 10
24. JNE start
26. Pop eax
28. }
32. Assert (value = 10 );
34. Return;
36. }

(6) commands for Guanzhong disconnection cannot be executed in VC, and exceptions may occur.[CPP]View plaincopy

1. void process ()
2. {
3. _ ASM {
4. CLI
5. }
7. return ;
8. }

(7) vc6.0 supports MMX instruction sets, however, vs2005 supports MMX and SSE instruction sets (8) if the project exists *. ASM Assembly file, you need to follow the steps below A) select [project]-> [setting] B) click project on the left and select *. in the ASM file, two options are displayed in the tab on the right, namely general and custom build C.) enter the corresponding compilation command in commands, so the MASM or NASM type is as follows, see the corresponding Compilation Manual.