pile up vs come up

pile up and come up both are verbs.

Word	Noun	Adjective	Verb	Adverb
pile up	No	No	Yes	No
come up	No	No	Yes	No

As verbs, come up is a hyponym of pile up; that is, come up is a word with a more specific, narrower meaning than pile up:

Other hyponyms of pile up include run up, corral, collect, pull in, scrape, scrape up, scratch, chunk, lump, bale, catch, fund, fund.

pile up (verb)	come up (verb)
increase in amount by collecting or gathering	result or issue
arrange into piles or stacks	start running, functioning, or operating
get or gather together	gather or bring together
	gather (money or other resources) together over time
	bring forth, usually something desirable
	come up, of celestial bodies
	come to the surface
	move toward, travel toward something or somebody or approach something or somebody
	move upward
	get something or somebody for a specific purpose
	originate or come into being
	be mentioned