On Wed, Aug 10, 2016 at 07:51:08AM +1000, kugan wrote:
> On 10/08/16 07:46, Jakub Jelinek wrote:
> >On Wed, Aug 10, 2016 at 07:42:25AM +1000, kugan wrote:
> >>There was no new regression while testing. I also moved the testcase from
> >>gcc.dg/torture/pr72835.c to gcc.dg/tree-ssa/pr72835.c. Is this OK for trunk?
> >
> >This looks strange. The tree-ssa-reassoc.c code has been trying to never
> >reuse SSA_NAMEs if they would hold a different value.
> >So there should be no resetting of flow sensitive info needed.
>
> We are not reusing but, if you see the example change in reassoc:
>
> - _5 = -_4;
> - _6 = _2 * _5;
> + _5 = _4;
> + _6 = _5 * _2;
>
> _5 and _6 will now have different value ranges because they compute
> different values. Therefore I think we should reset (?).
No. We should not have reused _5 and _6 for the different values.
It is not harmful just for the value ranges, but also for debug info.
Jakub
