I'm having problems with my code, it just prints "Invalid direction", and the matrix information is correct, my entry was this one .word 3 1 1 1 0 5 2 2 0 1 6 4.
Below is an explanation of how the program should work.
Enemy ships are placed in a string called "ships" present in the area data (.data), which must be read by the insert_ships function at the beginning of the game. THE string ships has the following pattern. The number of ships is informed in the first line inserted. Each of the following lines has a ship. The lines that specify ships have 4 values, separated by a space, as follows: the first value is the ship's layout 0 for a horizontal ship and 1 for a vertical ship; the second value is the length of the ship; the third value is the ship's starting line and; the fourth value is the ship's starting column. Observe the Example: 3 1 5 1 1 0 5 2 2 0 1 6 4
The positioning of ships is above the result in the following positioning:
The function inserts vessels must verify the validity of the positioning of the ships,
generating an error message for the following situations:
-The ship's position is invalid. Example: 0 3 11 7
-The ship extrapolates according to the dimensions of the matrix. Example: 0 4 2 7
-The overlap occurs on ships. Example 0 4 2 2 and 1 3 0 3
Now the full code, what's wrong with it?
.data
campo: .space 400
.align 2
navios: .word 3 1 1 1 0 5 2 2 0 1 6 4
letras: .asciz "abcdefgh"
arrume_sobreposicao : .asciz "Arrange the Overlay\n"
erro_nav: .asciz "ship out of bounds\n"
erro_direcao: .asciz "Invalid direction\n"
.text
main:
la t4, letras
la t5, navios
lw t6, 0(t5) # n = *np
addi t5,t5,1
li t1,0
li t2,100
la t3, campo
li a0, '~'
for1:
beq t1,t2, endfor1
#sw a0,0(t3)
lbu a0,0(t3)
addi t3,t3,4
addi t1,t1,1
j for1
endfor1:
li t1,0
for2:
beq t1,t6, endfor2
lbu a0, 0(t5) # dir
addi t5,t5,4
lbu a1, 0(t5) # size
addi t5,t5,4
lbu a2, 0(t5) # x
addi t5,t5,4
lbu a3, 0(t5) # y
addi t5,t5,4
jal ra, insert_ships
addi t1,t1,1
j for2
endfor2:
li a7, 10 # sai sem codigo de retorno
ecall # fim do programa
insert_ships:
li t1,1
li t2, 10
bne a1, t1, endif0 # if dir == 1
bgt a2,t2, fracasso1
bgt a3, t2,fracasso1
add t1, a3, a1 # x + size
bge t1, t2, else1 # if not (y + size >= 10)
blt a3, zero, else1 # if not (y < 0)
blt a2, zero, else1 # if not (x < 0)
bge a2, t2, else1 # if not (x >= 10)
# letra em t3, i em t1, x em a2 e y em a3
li t1, 0
fracasso1:
la a0, arrume_sobreposicao
li a7, 4
ecall
#j
for3:
bge t1,a2, endfor3 # i < size
la t5, campo
add t5, t5, a2 # m + x
add t2, a3, t1 # y + i
slli t4, t2, 3 # 8 * (y + i)
slli t2, t2, 1 # 2 * (y + i)
add t5, t5, t4 # m + x + 8*(y + i)
add t5, t5, t2 # m + x + 10*(y + i)
lbu t2, 0(t5)
li t4, '~'
bne t2, t3, else7 # if (m[x][y + i] == '~') ...
sb t3, 0(t5) # m[x][y+i] = letra
j endif7
else7:
la a0, arrume_sobreposicao
li a7, 4
ecall
#j endfor1 # break
#j endfor3
endif7:
addi t1, t1, 1
j for3
endfor3:
#j endif1
j endfor3
else1:
la a0, erro_nav
li a7, 4
ecall
endif1:
endif0:
li t2, 10
bne a1, zero, endif2 # if dir == 0 caso horizontal
bgt a2,t2, fracasso1
bgt a3, t2,fracasso1
bge a2,t2, fracasso1 # if(x < 10 && y < 10)
bge a3, t2,fracasso1
add t1, a2, a1 # x + size
# li t2, 10
bge t1, t2, else3 # if not (x + size >= 10)
blt a2, zero, else3 # if not (x < 0)
blt a3, zero, else3 # if not (y < 0)
bge a3, t2, else3 # if not (y >= 10)
# letra em t3, i em t1, x em a2 e y em a3
li t1, 0 # i = 0
for4:
bge t1,a2, endfor4 # i < size
la t5, campo
add t5, t5, a2 # m + x
add t5, a5, t1 # m + x + i
slli t4, a3, 3 # 8 * y
slli t2, a3, 1 # 2 * y
add t5, t5, t4 # m + x + i + 8*y
add t5, t5, t2 # m + x + i + 10*y
lbu t2, 0(t5)
li t4, '~'
bne t2, t3, else8 # if (m[x+i][y] == '~') ...
sb t3, 0(t5) # m[x+i][y] = letra
j endif8
else8:
la a0, arrume_sobreposicao
li a7, 4
ecall
j endfor2 # break
endif8:
addi t1, t1, 1
j for4
endfor4:
j endif3
else3:
la a0, erro_nav
li a7, 4
ecall
endif3:
endif2:
li t1, 1
ble a0, t1, endif5 # if dir > 1 eh erro
la a0, erro_direcao
li a7, 4
ecall
endif5:
#j ra # fim
li a7, 10 # sai sem codigo de retorno
ecall # fim do programa
You need to observe the fundamental qualities of multi-byte data on a byte addressable machine. Words are 32 bits wide, which means they take 4 bytes of storage, each.
A pair of words starting at location X has the first word at address of X, and the second word at address of X+4, because we have to skip over all 4 of the bytes of the first word in order to reach the second word.
We also must use the proper processor instructions to access word data stored in memory.
lwwill access location X, X+1, X+2, and X+3 to load 4 bytes of data from memory.lbuwill access only one byte location, so will miss 3 of the bytes of the word.Be aware of your data types, and ensure consistency of usage. In your program you have word data and (word) pointers as well as byte data, (byte) pointers. Word data should always use
lw&sw, while word pointers should always use multiples of 4, whereas byte data useslbuand multiples of 1. Don't treat a word data as byte data or vice versa.Learn to single step the instructions of your code and verify that each instruction is doing exactly what you expect. Most instructions have exactly one effect: loading a register with a value, or computing a sum or product, maybe storing into memory.
Also check your data before running the program, to make sure things look as you expect, and the data must be used by the program properly.
Don't wait until you have a complete program in order to verify by single stepping. Write a small section of code, then run it to make sure it works by single stepping every instruction and verify that each does what you expect.
As you get further along in the program you can set a break point at new code instead of single stepping all the way there, then run to the break point and single step to verify the new code.