come up vs pile up

come up and pile up both are verbs.

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

As verbs, pile up is a hypernym of come up; that is, pile up is a word with a broader meaning than come up:

Other hypernyms of come up include accumulate, amass, collect, compile, hoard, roll up.

come up (verb)	pile up (verb)
result or issue	increase in amount by collecting or gathering
start running, functioning, or operating	arrange into piles or stacks
gather or bring together	get or gather 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