1.1 編寫一個匯編程序mixop.s
– 實現(xiàn)函數(shù) y=mixop(x1,x2,x3)
– y=x1+x2*x3
– 調(diào)用c2.c中的multiply函數(shù)
1.2 C程序1：c1.c
– 實現(xiàn)函數(shù) void init();
– 作為啟動時的起始地址
– 在該函數(shù)內(nèi)要調(diào)用mixop函數(shù)完成6+40*50，結(jié)果存放在變量y中。
1.3 C程序2：c2.c
– 實現(xiàn)函數(shù)y=multiply(x1,x2)
– y=x1*x2
提示：init()函數(shù)結(jié)尾時，設(shè)置死循環(huán)。
1
/**//*
2
c1.c
3
*/
4
5extern unsigned int mixop( unsigned int x1, unsigned int x2, unsigned int x3 );
6
7void init() 
{
8 unsigned int y;
9 y = mixop( 6, 40, 50 );
10
for ( ; ; ) {
11
}
12}
13
14/**//*
15生成代碼：
16
170x00008000 mov ip, sp
180x00008004 stmdb sp!, {fp, ip, lr, pc}
190x00008008 sub fp, ip, #4
200x0000800c sub sp, sp, #4
210x00008010 mov r0, #6
220x00008014 mov r1, #40
230x00008018 mov r2, #50
240x0000801c bl 0x8058
250x00008020 mov r3, r0
260x00008024 str r3, [fp, -#16]
270x00008028 b 0x8028
28*/
29
1/**//*
2c2.c
3*/
4
5unsigned int multiply( unsigned int x1, unsigned int x2 ) {
6 return x1 * x2;
7}
8
9/**//*
10生成代碼：
11
12multiply :
130x0000802c mov ip, sp
140x00008030 stmdb sp!, {fp, ip, lr, pc}
150x00008034 sub fp, ip, #4
160x00008038 sub sp, sp, #8
170x0000803c str r0, [fp, -#16]
180x00008040 str r1, [fp, -#20]
190x00008044 ldr r3, [fp, -#20]
200x00008048 ldr r2, [fp, -#16]
210x0000804c mul r3, r2, r3
220x00008050 mov r0, r3
230x00008054 ldmdb fp, {fp, sp, pc}
24*/
25
1/**//*
2mixop.s
3*/
4
5.extern multiply
6
7/**//*
8unsigned int mixop( unsigned int x1, unsigned int x2, unsigned int x3 );
9*/
10.global mixop
11
12.text
13
14mixop:
15 mov ip, sp
16 stmdb sp!, {fp, ip, lr, pc}
17 sub fp, ip, #4
18
19 stmdb sp!, {r0-r2}
20 mov r0, r1
21 mov r1, r2
22 bl multiply
23 mov r3, r0
24 ldmia sp!, {r0-r2}
25 add r0, r0, r3
26
27 ldmdb fp, {fp, sp, pc}
28
29.end
30
31/**//*
32生成代碼：
33
34mixop :
350x00008058 mov ip, sp
360x0000805c stmdb sp!, {fp, ip, lr, pc}
370x00008060 sub fp, ip, #4
380x00008064 stmdb sp!, {r0, r1, r2}
390x00008068 mov r0, r1
400x0000806c mov r1, r2
410x00008070 bl 0x802c
420x00008074 mov r3, r0
430x00008078 ldmia sp!, {r0, r1, r2}
440x0000807c add r0, r0, r3
450x00008080 ldmdb fp, {fp, sp, pc}
46*/
47 存在的問題，SP寄存器沒有初始化，程序開始運(yùn)行時，SP 為零，數(shù)據(jù)壓棧后，SP 下溢出，但結(jié)果沒受影響。