[Bug c++/84132] [8 Regression] tree-data-ref.c:3938: poor coding ?

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84132

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
So the difference is that before this rev. 

  difference = chrec_fold_minus (type, chrec_a, chrec_b);

for

(gdb) p debug_generic_expr (chrec_a)
(signed int) {{(unsigned int) h_10(D), +, 1}_1, +, 6}_2
(gdb) p debug_generic_expr (chrec_b)
(signed int) {{(unsigned int) h_10(D) + 1, +, 1}_1, +, 6}_2

computed scev_not_known while now we compute -1.  So there's already the
case before where chrec_a/b are _not_
evolution_function_is_affine_multivariate_p
as the comment before the gcd_of_steps_may_divide_p call suggests.  And
later calls in the else if () cases suggest we indeed need to check that.