57 lines
1.0 KiB
Plaintext
57 lines
1.0 KiB
Plaintext
.equ STDOUT, 1
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.equ SVC_WRITE, 64
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.equ SVC_EXIT, 93
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.text
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.global _start
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_start:
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stp x29, x30, [sp, -16]!
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ldr x0, =str1
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mov x29, sp
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bl str_empty // str_empty("");
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ldr x0, =str2
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bl str_empty // str_empty("non-empty");
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ldp x29, x30, [sp], 16
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mov x0, #0
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b _exit
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str1: .asciz ""
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str2: .asciz "non-empty"
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.align 4
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// void str_empty(const char *s) - print "String is empty" if s is empty, "String is not empty" otherwise
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str_empty:
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mov x5, #0
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ldrb w5, [x0]
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ldr x1, =msg_empty
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ldr x3, =msg_not_empty
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mov x2, #16
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mov x4, #20
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cmp x5, #0
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csel x1, x1, x3, eq // msg = s[0] == 0 ? msg_empty : msg_not_empty;
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csel x2, x2, x4, eq // len = s[0] == 0 ? 16 : 20;
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mov x0, #STDOUT
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b _write // write(stdout, msg, len);
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msg_empty:
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.ascii "String is empty\n"
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msg_not_empty:
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.ascii "String is not empty\n"
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.align 4
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//////////////// system call wrappers
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// ssize_t _write(int fd, void *buf, size_t count)
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_write:
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stp x29, x30, [sp, -16]!
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mov x8, #SVC_WRITE
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mov x29, sp
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svc #0
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ldp x29, x30, [sp], 16
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ret
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// void _exit(int retval)
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_exit:
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mov x8, #SVC_EXIT
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svc #0
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