http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55555
--- Comment #6 from Jan Hubicka <hubicka at ucw dot cz> 2012-12-02 11:03:53 UTC
---
> I'm pretty sure there are no out-of-bounds. In particular coef_x is easy to
> check, it is only used as coef_x(:,lxp) where lxp is the loop bound 0..lp
> consistent with its def. Of course maybe the FE does something inconsistent ?
>
> Also this runs fine:
>
> fortran -O0 -fsanitize=address PR55555.f90 ; ./a.out
Hmm, I saw similar weird cases generated by the frontend. coef_x is array of 8
elements
real(kind=8) coef_x[8];
in loop analyzis we do:
Induction variable (integer(kind=8)) 4 + 4 * iteration does not wrap in
statement pretmp_516 = coef_x[pretmp_515];
in loop 4.
Statement pretmp_516 = coef_x[pretmp_515];
is executed at most 0 (bounded by 0) + 1 times in loop 4.
This is true, pretmp_512 would be 8 at the second iteration of the loop.
later we conclude
Loop 4 iterates 1 times.
Loop 4 iterates at most 1 times.
BB: 9, after_exit: 0
size: 0 # DEBUG lxp => lxp_4
size: 0 _137 = (integer(kind=8)) lxp_4;
size: 1 _140 = _137 + pretmp_508;
size: 1 _142 = *pol_x_141(D)[_140];
size: 1 _143 = _137 * 4;
size: 1 _144 = _143 + -1;
BB: 10, after_exit: 0
size: 1 _146 = S.25_279 + _144;
size: 1 _150 = _142 * prephitmp_520;
size: 1 _151 = _150 + prephitmp_517;
size: 1 coef_x[_146] = _151;
size: 1 S.25_153 = S.25_279 + 1;
size: 1 ivtmp_162 = ivtmp_91 - 1;
size: 2 if (ivtmp_162 == 0)
goto bb12 or bb11
BB: 11, after_exit: 0
size: 1 pretmp_515 = _144 + S.25_153;
size: 1 pretmp_516 = coef_x[pretmp_515];
size: 1 pretmp_518 = S.25_153 + -1;
size: 1 pretmp_519 = s[pretmp_518];
BB: 12, after_exit: 0
size: 0 # DEBUG lxp => lxp_4 + 1
size: 1 ivtmp_109 = ivtmp_163 - 1;
size: 2 if (ivtmp_109 == 0)
goto bb 13 or exit
BB: 13, after_exit: 1
size: 1 lxp_154 = lxp_4 + 1;
size: 0 pretmp_506 = (integer(kind=8)) lxp_154;
size: 1 pretmp_509 = pretmp_506 * 4;
size: 1 pretmp_510 = pretmp_509 + -1;
size: 1 pretmp_512 = pretmp_510 + 1;
size: 1 pretmp_513 = coef_x[pretmp_512];
Unrolled loop 4 completely (duplicated 1 times).
Exit condition of peeled iterations was eliminated.
Last iteration exit edge was proved true.
So the curious statements are in bb11. Adding unreachable calls makes CSE to
eventually
turn condition in the second copy of BB10 to always just to BB 12 that seem all
right
to me.
Perhaps cascaded unrolling confuse some of the exits...
Honza
