arm编译程序示例.docVIP

一。if语句实例1 /* *if(a 50) * puts(a 50); r0 r1 r2 r3 *else if(b a) * puts(b a); *else if(b 20) * puts(b 20); * */ .section .rodata .align 2 .LC0: .string a 50 .LC1: .string b a .LC2: .string b 20 .text .align 2 .global main main: push {lr} @上一个函数的返回地址压到栈中; @ mov r0, #60 mov r0, #10 mov r1, #30 cmp r0, #50 bgt do1 cmp r1, r0 blt do2 cmp r1, #20 blt do3 b out do1: ldr r0, .L0 bl puts b out do2: ldr r0, .L0+4 bl puts b out do3: ldr r0, .L0+8 bl puts out: pop {pc} @从栈中取出lr存到pc中; .L0: .word .LC0 .word .LC1 .word .LC2 if语句实例2, 运算 /* *if (a 10 　20) * puts(a 10 a 20); */ .section .rodata .align 2 .LC0: .string a 10 a 20 .text .align 2 .global main main: push {lr} @上一个函数的返回地址压到栈中; mov r0, #15 @if( (a10) (a20) ) @ puts(a 10 a 20); cmp r0, #10 ble out cmp r0, #20 ldrlt r0, .L0 bllt printf out: pop {pc} @从栈中取出lr存到pc中; .L0: .word .LC0 if语句实例3, ||运算 .section .rodata .align 2 .LC0: .string a 10 || a 20 .text .align 2 .global main main: push {lr} @上一个函数的返回地址压到栈中; mov r0, #15 @if( (a10) || (a20) ) @ puts(a 10 || a 20); cmp r0, #10 blt do cmp r0, #20 ble out do: ldr r0, .L0 bl puts out: pop {pc} @从栈中取出lr存到pc中; .L0: .word .LC0 二，switch语句的实现1 /* *char ch = A; * *switch (ch) *{ * case x: * break; * ... *} * */ .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, #16 mov r3, #65 @ch = A; strb r3, [fp, #-5] ldrb r3, [fp, #-5] @ zero_extendqisi2 str r3, [fp, #-16] @int -- switch ldr r3, [fp, #-16] cmp r3, #45 @二分查找; beq .L5 ldr r3, [fp, #-16] cmp r3, #45 bgt .L9 ldr r3, [fp, #-16] cmp r3, #2 beq .L3 ldr r3, [fp, #-16] cmp r3, #9 beq .L4 b .L11 .L9: ldr r3, [fp, #-16] cmp r3, #97 beq .L7 ldr r3, [fp, #-16] cmp r3, #99 beq .L8 ldr r3, [fp, #-16] cmp r3, #65 beq .L6 b .L11 .L7: ldrb r3, [fp, #-5] @ zero_extendqisi2 ldr r0