CODEWITHSUNDEEP
assemblymipsmars-simulator
Luis Candeias
Luis Candeias

Reputation: 1

why blt instruction don't work? Mars mips assembly

I'm tryng to open a file with a list of contacts, and when i verify if are with the correctly format (name ',' number), i use a bgt and a blt instruction to see if the chars are bigger than z or lower than a, so rejected. but when i do this, my blt instruction doesn't work. when its executed jump do the label, and if before i have a beq with a value bigger than the blt, he jumps to. 

Maiuscula:
lb $t0,0($a0)       #carrega a0 em t0
#slt $t1, $zero,$t0 #carater de t0 com zero
beq $t0,$zero,END
nop #se t1=0 entao, t0 tem o carater nulo, logo END
li $t3,0x41     # A maiusculo em ascii
li $t4,0x5a     # Z maiusculo em ascii
slt $t5,$t0,$t4
bgt $t0,$t4,Erro    #tinha bgt
nop

blt $t0,$t3,zero    #here is the error
nop

j minuscula
nop

Upvotes: 0

Views: 2358

Answers (1)

gusbro
gusbro

Reputation: 22585

Remove the line slt $t5,$t0,$t4, as you are using pseudoinstruction bgt/blt which already uses slt + bne to accomplish the task. Aside from that, your code will:

  • Branch to Erro if the character is > 'A'
  • Branch to zero if the character is < 'Z'
  • Otherwise, it will branch to minuscula

So there seems to be some logic errors there...

For example, you should use bge instead of bgt and ble instead of blt because otherwise you will not check 'A' and 'Z' correctly.

Aside from that, I guess the logic is not doing what you meant it to do...

Upvotes: 1

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