(Assembly) Basic instruction of x86 assembly based on VS

environment

visual studio select x86 to run

sample code

/**
| 32位 | 16位 | 高8位 | 低8位 |
| ---- | ---- | ----- | ----- |
| EAX  | AX   | AH    | AL    |
 */
#include <iostream>

int main() {
    
    
    int32_t x = 1;
    int32_t y = 2;

    // 简单加法示例
    __asm {
    
    
        mov eax, x;
        mov ebx, y;
        add eax, ebx;
        mov x, eax;
    };

    ::std::printf("x = %d y = %d\n", x, y);
    
    return 0;
}

Assembly basics

flag bit

# visual studio 中的标志位
# OV UP EI PL ZR AC PE CY

• OV overflow
  • Out of range means overflow 1, otherwise 0
• UP increment
  • 1: Process data strings in descending order; 0: Process data strings in ascending order
• EI enable interrupt
  • CPU enables interrupt 1, otherwise 0
• PL Positive
  • The operation result is 1 if it is regular, otherwise 0
• ZR líng
  • 1 if the result of the operation is 0, otherwise 0
• AC auxiliary carry
  • Carry 1 from the lower 4 bits to the higher bit, otherwise 0
• PE parity
  • The number of 1 in the lowest 16 bits is an even number is 1, otherwise 0
• CY carry
  • The highest bit carries 1, otherwise 0

common command

Here we introduce the common basic instructions of assembly, without too much expansion, only record the basic meaning

instruction	effect	e.g
add	addition	add eax, ebx;
and	bitwise AND operation	and eax, ebx;
call	The address of the next instruction is pushed onto the stack and jumps to the target for instruction execution	call address;
cmp	Operand 1-(sign extension) operand 2 is not saved, observe the flag bit	cmp eax, ebx;
dec	Decrement	dec eax;
div	Division result, remainder (different parameters)	various bx;
low	Multiplication (different parameters)	imul eax, ebx, ecx;
inc	self-increment	inc eax;
jmp	jump	This is a series of instructions
lea	load address	lea eax, address;
mov		mov eax, 114514;
movsd	double-precision assignment to register
movss	But assignment of precision numbers to floating-point registers
movsx/movsxd	sign extension transmission
movs series	bulk memory transfer
movzx	0 extended transmission
neg	Reversal (±)	neg eax;
not	bitwise inversion	not eax;
or	bitwise or	or eax, ebx;
pop and related	pop out	pop eax;
push and related	stack	push eax;
rcl	Circularly shift the highest bit to cf, and cf to the lowest bit	rcl eax, times;
rcr	Circular right shift cf to fill in the highest bit and the lowest bit to fill in cf	rcr eax, times;
ret	Restore address from stack	ret ;
role	Circularly shift the highest bit to cf and the lowest bit, the original value of cf is discarded	rol eax, number of times;
ror	Circularly shift the lowest bit to the right and fill in the highest sum cf	ror eax, times
sar	Arithmetic right shift sign bit preserved	sar eax, value;
shr	Logical right shift high bit complement 0	shr eax, times
sub	subtraction	sub eax, ebx;
test	Bitwise and do not save, observe the flag bit	cmp eax, ebx;
xor	bitwise XOR	xor eax, ebx;

vs configuration

register

After entering debug mode, debug at the top -> window -> register

disassembly

In the editing interface, right click -> go to disassembly

After entering, right click and select to display specific information

detection variable

Note that the settings do not enable optimization

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