Goal:
  
  G : t
  invG : invariants G
  acG : acyclic_no_loop G
  x : V.t
  y : V.t
  hx : VSet.In x (V G)
  hy : VSet.In y (V G)
  nxy : Z
  hxy : (lsp G x y <= Some nxy)%nbar
  nx : Z
  eqlspx : lsp G (s G) x = Some nx
  nxpos : 0 <= nx
  eqnx : Z.of_nat (to_label (lsp G (s G) x)) = nx
  cstr : 0 <= Z.of_nat (stdl x)
  cstr0 : 0 <= Z.of_nat (to_label (lsp G (s G) x))
  cstr1 : 0 <= Z.of_nat dxy
  ============================
   (Z.of_nat (stdl x) <= Z.of_nat (stdl x) + Z.of_nat dxy)


DEBUG:Going to execute:
constr:(false)