MOB_MD_ASM

const1.s

	.text
	.align	2
	.global	const1
const1:


aa_check:
	ldrb	r1,	[r0]	@ ielasa tekošo simbolu

	cmp		r1,	#0		@ aizmet uz beigam, jo vārds beidzies. nav nederīgu simbolu
	beq		success

	cmp		r1,	#'a		@ simbols nav a. met uz nākošo pārbaudes punktu
	bne		b_check

@ // otra a simbola pārbaude
	add		r0,	r0,	#1
	ldrb	r1,	[r0]	@ ielasa tekošo simbolu
	cmp		r1,	#'a		@ a pārbaude
	bne		fail
	add		r0,	r0,	#1

	b		aa_check

b_check:
	ldrb	r1,	[r0]	@ ielasa tekošo simbolu

	cmp		r1,	#0		@ aizmet uz beigam, jo vārds beidzies. nav nederīgu simbolu
	beq		success

	cmp		r1,	#'b		@ simbols nav b. rezultats nederigs
	bne		fail

	add		r0,	r0,	#1
	b		b_check

error:
	mov		r0, #2
	b		end

success:
	mov		r0,	#1
	b		end

fail:
	mov		r0, #0

end:
	bx	lr
	.size	const1, .-const1

const1_main.c

#include <stdio.h>
#include <stdlib.h>

int const1(char[]);

void check(char value[]) {

	if(const1(value)) {
		printf("yes\n");
	}	
	else {
		printf("no\n");
	}
}

int main (int argc, char **argv)
{

	// (aa)*b*

	check(""); // yes
	check("a"); // no
	check("aa"); // yes
	check("aaa"); // no
	check("aab"); // yes
	check("b"); // yes
	check("bb"); // yes
	check("bba"); // no
	return 0;
}

Makefile

# Sample Makefile

TARGET := const1

OBJ := $(TARGET)_main.o $(TARGET).o

ASFLAGS = -mcpu=xscale -alh=$*.lis -L
CFLAGS = -mcpu=xscale -O0 -Wall
LDFLAGS =

CC := arm-linux-gnueabi-gcc
AS := arm-linux-gnueabi-as

.PHONY: test all clean distclean

test:	all
	qemu-arm $(TARGET) 

all:	$(TARGET)

clean:
	$(RM) $(TARGET) *.o

distclean:	clean
	$(RM) *.lis *~

allhfiles := $(wildcard *.h)

$(TARGET):	$(OBJ)
	$(CC) $(LDFLAGS) -o $@ $^

%.o:	%.s
	$(AS) -g $(ASFLAGS) -o $@ $<

%.o:	%.c $(allhfiles)
	$(CC) -g $(CFLAGS) -o $@ -c $<

%.s:	%.c $(allhfiles)
	$(CC) $(CFLAGS) -fomit-frame-pointer -o $@ -S $<