[Bug tree-optimization/33113] Failing to represent the stride (with array) of a dataref when it is not a constant

["dorit at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #2 from dorit at gcc dot gnu dot org  2007-08-20 05:55 -------
> Making us return symbolic stride would not be hard.  The problem is that data
> dependence analysis would fail anyway, 

sometimes (not in this testcases) there won't be a need for dependence testing
- e.g. a reduction computation where there are no stores, or initialization
with a constant (i.e. a store and no loads), so there's already a value in
doing this.

> since we cannot tell whether n is zero.

can we do the data-dependence analysis conditioned on a maybe_zero (like the
number-of-iterations analysis)? (by the way, I was told that ifort vectorizes
this. I think we'd need loop reversal to vectorize the inner-loop though. on
top of overcoming the unknown-stride issue in the DR and DDR analysis)


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33113