YES

Problem 1: 

(VAR v_NonEmpty:S x:S y:S)
(RULES
rev(++(x:S,x:S)) -> rev(x:S)
rev(++(x:S,y:S)) -> ++(rev(y:S),rev(x:S))
rev(a) -> a
rev(b) -> b
)

Problem 1: 

Dependency Pairs Processor:
-> Pairs:
 REV(++(x:S,x:S)) -> REV(x:S)
 REV(++(x:S,y:S)) -> REV(x:S)
 REV(++(x:S,y:S)) -> REV(y:S)
-> Rules:
 rev(++(x:S,x:S)) -> rev(x:S)
 rev(++(x:S,y:S)) -> ++(rev(y:S),rev(x:S))
 rev(a) -> a
 rev(b) -> b

Problem 1: 

SCC Processor:
-> Pairs:
 REV(++(x:S,x:S)) -> REV(x:S)
 REV(++(x:S,y:S)) -> REV(x:S)
 REV(++(x:S,y:S)) -> REV(y:S)
-> Rules:
 rev(++(x:S,x:S)) -> rev(x:S)
 rev(++(x:S,y:S)) -> ++(rev(y:S),rev(x:S))
 rev(a) -> a
 rev(b) -> b
->Strongly Connected Components:
->->Cycle:
->->-> Pairs:
 REV(++(x:S,x:S)) -> REV(x:S)
 REV(++(x:S,y:S)) -> REV(x:S)
 REV(++(x:S,y:S)) -> REV(y:S)
->->-> Rules:
 rev(++(x:S,x:S)) -> rev(x:S)
 rev(++(x:S,y:S)) -> ++(rev(y:S),rev(x:S))
 rev(a) -> a
 rev(b) -> b

Problem 1: 

Subterm Processor:
-> Pairs:
 REV(++(x:S,x:S)) -> REV(x:S)
 REV(++(x:S,y:S)) -> REV(x:S)
 REV(++(x:S,y:S)) -> REV(y:S)
-> Rules:
 rev(++(x:S,x:S)) -> rev(x:S)
 rev(++(x:S,y:S)) -> ++(rev(y:S),rev(x:S))
 rev(a) -> a
 rev(b) -> b
->Projection:
 pi(REV) = 1

Problem 1: 

SCC Processor:
-> Pairs:
 Empty
-> Rules:
 rev(++(x:S,x:S)) -> rev(x:S)
 rev(++(x:S,y:S)) -> ++(rev(y:S),rev(x:S))
 rev(a) -> a
 rev(b) -> b
->Strongly Connected Components:
 There is no strongly connected component

The problem is finite.