Dib views GIR as an annoyance at best, and certainly doesn't seem to see him as a threat to planet Earth; on a regular basis, he simply ignores the robot in favor of defeating Zim. At times, he takes advantage of GIR's inherently friendly nature to gain access to Zim's base, or to leave some spy equipment inside. Dib has also used GIR to contact the Tallest in "The Frycook What Came from All That Space".
Unlike Zim, GIR doesn't seem to be a hindrance to Dib. In fact, he often winds up aiding Dib on occasion, either by hindering Zim, or simply outright assisting Dib out of good will. In "Zim Eats Waffles", GIR happily puts spy cameras in Zim's house for Dib to spy on him without question.
In Issue 3 of the Invader Zim comics, when Zim askes GIR to guard Dib in the art hater's closet, Dib eventually convinces him to guard a pen instead. GIR complies, letting Dib go free to stop Zim from summoning the Star Donkey.
Sometimes, Dib overestimates GIR's ability, such as in "Battle of the Planets"; GIR was sent to distract Dib, and after button mashing on Mercury, Dib simply asked GIR to go away, more out of exasperation than legitimately thinking it would work.
He was mildly surprised when the robot did as he was told. What Dib failed to realize, at the time, was that GIR took his camera along with him, which held all his evidence.
GIR refers to Dib mainly as a "Big-Head Boy", though he does have various other nicknames for him. He treats Dib like he treats everyone else - with trust, overwhelming kindness, and a good dose of blissful insanity. He openly claims in "Planet Jackers", as well as the unaired episode "Return of Keef", that he thinks Dib is nice.
However, in the unfinished episode "Mopiness of Doom" when GIR desperately tried to get Dib to chase Zim again, it was made apparent that neither Dib nor GIR seemed to know each other's names. Dib simply referred to GIR as "Zim's evil robot-dog-thingy," a similar name to what he would later call GIR in Enter the Florpus, while GIR was seemingly content with calling Dib "Mary". Though adversely, GIR previously showed knowledge of Dib's name in "Planet Jackers". In "Mysterious Mysteries", GIR also appeared as a surprise guest, and said he was upset that Dib was so mean to Zim.
Unlike Zim, GIR likes Dib.. But then again, GIR likes just about everyone. He didn't mind at all when Dib wanted to watch him contact the Almighty Tallest, even dancing with him after the robot had conveyed his message.
Although Zim is his master, and GIR is occasionally shown to recognize that, he also has no qualms with helping Dib in his plans to stop Zim.
Presumably this is only because GIR is remarkably friendly to everyone he meets, and doesn't understand that helping Dib is only making life hard for Zim. GIR also thinks Dib's head "smells like a puppy", something he referred to while he was clinging to it in "Tak: The Hideous New Girl".