【ARM】ARM汇编程序设计(四) 选择结构

00. 目录

文章目录

• 00. 目录
• 01. if 结构一
• 02. if 结构二
• 03. if 结构三
• 04. if 结构四
• 05. if 结构五
• 06. switch结构
• 07. 附录

01. if 结构一

.section .rodata
.align 2
.LC0:
.string "i > 10\n"

.LC1:
.string "i <= 10\n"

.section .text
.align 2
.global main
main:
push {lr}

mov r2, #1
cmp r2, #10
ldrgt r0, =.LC0
ldrle r0, =.LC1

bl printf

mov r0, #0
pop {pc}

02. if 结构二

.section .rodata
.align 2
.LC0:
.string "i > 10\n"

.LC1:
.string "i <= 10\n"

.section .text
.align 2
.global main
main:
push {lr}

mov r2, #1
cmp r2, #10
bgt do1
b do2

do1:
ldr r0, =.LC0
bl printf
b out

do2:
ldr r0, =.LC1
bl printf

out:

mov r0, #0
pop {pc}

03. if 结构三

.section .rodata
.align 2
.LC0:
.string "i > 10\n"

.LC1:
.string "i < 10\n"

.LC2:
.string "i == 10\n"

.section .text
.align 2
.global main
main:
push {lr}

mov r2, #1
cmp r2, #10
bgt do1
blt do2
b do3

do1:
ldr r0, =.LC0
bl printf
b out

do2:
ldr r0, =.LC1
bl printf
b out

do3:
ldr r0, =.LC2
bl printf

out:

mov r0, #0
pop {pc}

04. if 结构四

if(i > 10)
...
else if(i + j > 10)
...
else if(j < 10)
...

.section .rodata
.align 2
.LC0:
.string "i > 10\n"

.LC1:
.string "i + j > 10\n"

.LC2:
.string "j < 10\n"

.section .text
.align 2
.global main
main:
push {lr}

mov r2, #100
mov r3, #2

cmp r2, #10
bgt do1

add r1, r2, r3
cmp r1, #10
bgt  do2

cmp r3, #10
blt do3

b out

do1:
ldr r0, =.LC0
bl printf
b out

do2:
ldr r0, =.LC1
bl printf
b out

do3:
ldr r0, =.LC2
bl printf

out:

mov r0, #0
pop {pc}

05. if 结构五

.section .rodata
.align 2
.LC0:
.string "i > 10 && i < 20\n"

.section .text
.align 2
.global main
main:
push {lr}

mov r2, #15

cmp r2, #10
ble out

cmp r2, #20
blt do1
b out

do1:
ldr r0, =.LC0
bl printf

out:

mov r0, #0
pop {pc}

06. switch结构

C语言代码

#include <stdio.h>

int main(void)
{
int i = 10;
char ch = 'a';

switch(i)
{
case 1:
printf("val = %d \n", i);
break;
case 345:
printf("val = %d \n", i);
break;
case 23:
printf("val = %d \n", i);
break;
case 7:
printf("val = %d \n", i);
break;
case 1234:
printf("val = %d \n", i);
break;
case 17:
printf("val = %d \n", i);
break;
case 10:
printf("val = %d \n", i);
break;
}

return 0;
}

汇编语言代码

.section	.rodata
.align	2
.LC0:
.ascii	"val = %d \012\000"

.text
.align	2
.global	main
main:
stmfd	sp!, {fp, lr}
add	fp, sp, #4
sub	sp, sp, #8
mov	r3, #10
str	r3, [fp, #-8]
mov	r3, #97
strb	r3, [fp, #-9]
ldr	r3, [fp, #-8]
cmp	r3, #17
beq	.L6
cmp	r3, #17
bgt	.L10
cmp	r3, #7
beq	.L4
cmp	r3, #10
beq	.L5
cmp	r3, #1
beq	.L3
b	.L2
.L10:
ldr	r2, .L11
cmp	r3, r2
beq	.L8
ldr	r2, .L11+4
cmp	r3, r2
beq	.L9
cmp	r3, #23
beq	.L7
b	.L2
.L3:
ldr	r3, .L11+8
mov	r0, r3
ldr	r1, [fp, #-8]
bl	printf
b	.L2
.L8:
ldr	r3, .L11+8
mov	r0, r3
ldr	r1, [fp, #-8]
bl	printf
b	.L2
.L7:
ldr	r3, .L11+8
mov	r0, r3
ldr	r1, [fp, #-8]
bl	printf
b	.L2
.L4:
ldr	r3, .L11+8
mov	r0, r3
ldr	r1, [fp, #-8]
bl	printf
b	.L2
.L9:
ldr	r3, .L11+8
mov	r0, r3
ldr	r1, [fp, #-8]
bl	printf
b	.L2
.L6:
ldr	r3, .L11+8
mov	r0, r3
ldr	r1, [fp, #-8]
bl	printf
b	.L2
.L5:
ldr	r3, .L11+8
mov	r0, r3
ldr	r1, [fp, #-8]
bl	printf
mov	r0, r0	@ nop
.L2:
mov	r3, #0
mov	r0, r3
sub	sp, fp, #4
ldmfd	sp!, {fp, pc}
.L12:
.align	2
.L11:
.word	345
.word	1234
.word	.LC0
.size	main, .-main
.ident	"GCC: (ctng-1.8.1-FA) 4.5.1"
.section	.note.GNU-stack,"",%progbits

07. 附录