[Bug tree-optimization/92130] Missed vectorization for iteration dependent loads and simple multiplicative accumulators

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92130

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2019-10-17
                 CC|                            |rguenth at gcc dot gnu.org
             Blocks|                            |53947
     Ever confirmed|0                           |1

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
You can try -fno-tree-pre because for the original issue you mention the issue
is that PRE figures the first iteration computed values at compile-time which
then effectively rotates the loop which the vectorizer is not happy with.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations