5 replies to this topic

[your_rock]

Hi,

I've got an assignment where I have to turn C code into machine and assembly code, but I'm having a problem with understanding beq, bne, blt, and bnl commands. I have to do a simple while loop (while i >= 0), and I'm guessing I have to use bnl command but I have no idea how to use it. Anyone can provide me a link to learn about branching or can tell me about will be much appreciated. Also I have to use AT&T syntax, not Intel one.

Thanks in advance.

[RhetoricalRuvim]

For the following C code,

while (variable1 < variable2){ 

  variable2 += variable3; 

} 

I would usually do something like this:

lp1: 

  mov eax, dword [variable1] 

  cmp eax, dword [variable2] 

  jnl lp1s 

  

  mov eax, dword [variable3] 

  add dword [variable2], eax 

  

  jmp lp1 

lp1s: 

I don't know AT&T syntax, though; this is just my two cents.

[mebob]

Are you using MIPS, x86, or what? I'm not sure whether beq, bne, blt, or bnl exists on x86, and that is why I ask.

[RhetoricalRuvim]

I think the 'b' - in beq, bne, blt, and bnl - stands for "branch" (verb).

[dargueta]

Yeah, beq, bne, blt, and bnl are MIPS instructions. What did your assignment say?

[RhetoricalRuvim]

You would still use very similar instructions on MIPS, as you would on x86. Like instead of using the 'jz' instruction, you would use the 'beq' instruction, etc.