[Bug tree-optimization/19224] [4.0 regression] Endless loop compiling simple file: Bug in tree-scalar-evolution.c (instantiate_parameters_1)?

["sebastian dot pop at cri dot ensmp dot fr" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From sebastian dot pop at cri dot ensmp dot fr  2005-01-02 21:46 -------
(In reply to comment #7)
> Subject: Re:  [4.0 regression] Endless loop compiling simple file: Bug in
tree-scalar-evolution.c (instantiate_parameters_1)?
> 
> not really (well, maybe in this particular case, but not in general).
> Your patch definitely helps (and you should submit it anyway), but
> yhe problem is that even with your patch it may happen that
> instantiate_parameters is called recursively several times for one
> ssa name if the expression contains it several times, and if this
> happens for several expressions in a row, you get the exponential
> complexity.  I am just testing the patch below that caches the results
> to avoid this problem.
> 

Richtig.  I'm just speeding the chrec_dont_know case, whereas your patch
solves the more general problem of huge expressions that have to be 
instantiated and that don't necessarily lead to unknown evolutions.

Thanks.

PS: I'll test my patch separately and will post it to gcc-patches.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19224