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这是一些示例代码，可以对照上面的笔记，分析这些代码到底做了什么，将下面这12个练习
.global _start
_start:
@practice1
mov r0,#2
lsl r0,#2
ldr r1,=0x5
sub r0,r0,r1
ldr r1,=0x12345678
add r0,r0,r1
@parctice2
ldr r1,=0x3
ldr r2,=0x5
mul r3,r2,r1
ldr r4,=0x19
sub r0,r4,r3
add r0,#6
@practice3
ldr r2,=0xffff
ldr r3,=0x12345678
and r1,r2,r3
bic r0,r3,r2
lsr r0,#16
add r0,r1
@practice4
ldr r0,=0xabcd
ldr r1,=0x4
bic r0,r0,r1
ldr r1,=0xb
orr r0,r0,r1
ldr r1,=0xf07f
and r0,r0,r1
@parctice5
ldr r0,=0x5 @a
ldr r1,=0x6 @b
ldr r2,=0xa @c
cmp r0,r1
addgt r1,r1,#1
cmp r0,r2
addle r2,r2,#1
@parctice6
start1:
mov r0,#0
mov r1,#1
loop:
add r0,r0,r1
add r1,r1,#1
cmp r1,#100
ble loop
@ bgt stop
@partice7
ldr r0,=0x40000000
ldr r1,=0x12345678
str r1,[r0]
ldr r2,[r0]
@partice8 @0x40000000,0x4000ffff
mov r0,#0x40000000
mov r1,#1
loop1:
str r1,[r0],#4
add r1,r1,#1
cmp r1,#10
ble loop1
ldr r2,=0x40000000
ldr r3,[r2]
ldr r4,=0x40000100
str r3,[r4]
@parctice9
ldr r0,=0x40000000
ldr r1,=0x1234
str r1,[r0],#4
ldr r1,=0xabcd
str r1,[r0]
ldr r2,[r0],#-4
add r3,r3,r2
ldr r2,[r0]
add r3,r3,r2
@parctice10
mov r0,#0x40000000
mov r1,#0x11
mov r2,#0x22
mov r3,#0x33
stmia r0!,{r1-r3}
stmdb r0!,{r4-r6}
@practice11
ldr sp,=0x4000fff0
mov r1,#0x11
mov r2,#0x22
mov r3,#0x33
stmfd sp!,{r1-r3}
mov r1,#0
mov r2,#0
mov r3,#0
ldmfd sp!,{r1-r3}^
@practice12
mrs r0,cpsr
mov r1,#1
bic r0,r0,r1,lsl #7
msr cpsr,r0
mrs r0,cpsr
mov r1,#1
orr r0,r0,r1,lsl #7
msr cpsr,r0
stop:
b stop
汇编和C语言的相互调用
(1)汇编调用 C
mov r0,#2
mov r1,#3
ldr sp,=0x4000fff0
bl add
(2) C 内嵌汇编格式
int add(int a,int b)
{
int c;
/*
asm
(
"add r0,%1,%2\n"
"mov %0,r0\n"
:"=r"(c) //arm ---> C
:"r"(a),"r"(b) // C ---> arm
:"r0" //xiu gai guo de ji cun qi
);
*/
c=a + b;
return c;
}