Most of the problems inherent in establishing HAL's state of being stem from a lack of understanding of the definitions themselves. Is there a real difference between "artificial intelligence" and biological intelligence? Is Intelligence less so, because it is "artificial"? Are emotions anything more than learned or instinctive mental tools used as survival traits? Does intelligence automatically qualify as sentience, or does self-awareness define sentience? And does intelligence, emotion and sentience in combination determine a "soul," or is there something else needed for that?
If intelligence is intelligence, whether naturally evolved or constructed by a second party... If emotions are applied by the intelligence to improve its interaction with others, and its survival... if self-awareness defines sentience... then by those measures, HAL is a much a sentient being as the astronauts, and his end just as tragic, because it is preordained... he is literally preprogrammed to fail. If anything, it is harder to tell, because HAL does not respond the way we do, does not demonstrate emotion the way we do, so we have no reference with which to qualify his sentience, his emotions, his soul.
However, if "artificial intelligence," by definition, doesn't count as real intelligence... if emotions and sentience can only be part of a mind with a soul... then HAL was a toaster that was unplugged.
Kubrick understood this. His film portrayal of Poole and Bowman as nearly emotionless, mirrored HAL's interactions with the astronauts. Frank's anger at HAL trying to kill him was mirrored by HAL's desperation to stop Frank from shutting him down. The deaths of the sleeping crewmen were treated as abstracts, killing men that already looked dead. Dave was literally swatted away by HAL, and when Frank could not return with the body, he was unceremoniously discarded.
There was no discernable difference between the intelligence, sentience, emotion, or soul of the astronauts, and of HAL. Kubrick did this deliberately, to blur the line between human and computer "sentience" and force the viewer to consider those definitions against machines, and against themselves.