https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65855
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |spop at gcc dot gnu.org
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Looks like SCEV analysis is broken for this case.
<bb 3>:
# t_11 = PHI <0(5), t_5(7)>
# i_13 = PHI <1(5), i_6(7)>
t_5 = t_11 + i_13;
i_6 = i_13 + 1;
if (i_6 <= _10)
goto <bb 7>;
else
goto <bb 8>;
<bb 7>:
goto <bb 3>;
<bb 8>:
# t_2 = PHI <t_5(3)>
t_11 = { 0, +, i_13 }_1 (ok)
i_13 = {1, +, 1}_1 (ok)
(instantiate_scev
(instantiate_below = 5)
(evolution_loop = 1)
(chrec = {0, +, i_13}_1)
(analyze_scalar_evolution
(loop_nb = 1)
(scalar = i_13)
(get_scalar_evolution
(scalar = i_13)
(scalar_evolution = {1, +, 1}_1))
(set_scalar_evolution
instantiated_below = 5
(scalar = i_13)
(scalar_evolution = {1, +, 1}_1))
)
(res = {0, +, {1, +, 1}_1}_1))
(instantiate_scev
(instantiate_below = 5)
(evolution_loop = 1)
(chrec = {1, +, 1}_1)
(res = {1, +, 1}_1))
(set_scalar_evolution
instantiated_below = 5
(scalar = t_5)
(scalar_evolution = {1, +, {2, +, 1}_1}_1))
not sure where the latter result comes from. It comes from
#10 0x0000000000eac871 in scev_const_prop ()
at /space/rguenther/src/svn/trunk/gcc/tree-scalar-evolution.c:3456
3456 NULL);
(gdb) l
3451 if (!POINTER_TYPE_P (type)
3452 && !INTEGRAL_TYPE_P (type))
3453 continue;
3454
3455 ev = resolve_mixers (loop, analyze_scalar_evolution (loop,
name),
3456 NULL);
analyzing the evolution of t_2.
So we end up looking at t_5 = t_11 + i_13 which is {0, +, {1,+, 1}_1}_1 +
{1,+,1}_1 but that isn't {1, +, {2, +, 1}_1 }_1 as chrec_fold_plus_poly_poly
maintains?
But maybe this kind of CHREC is just ill-formed in the first place?
Sebastian, any ideas here?
