[Bug tree-optimization/69297] [6 Regression] Performance regression after r230020

[ysrumyan at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69297

--- Comment #4 from Yuri Rumyantsev <ysrumyan at gmail dot com> ---
Yes, this loop was added for avoiding dce phase.

Thanks.
Yuri.

2016-01-18 13:33 GMT+03:00 rguenth at gcc dot gnu.org
<gcc-bugzilla@gcc.gnu.org>:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69297
>
> --- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
> With a fix:
>
> t.c:76:10: note: Cost model analysis:
>   Vector inside of basic block cost: 376
>   Vector prologue cost: 0
>   Vector epilogue cost: 0
>   Scalar cost of basic block: 96
> t.c:76:10: note: not vectorized: vectorization is not profitable.
>
> Note the reduction loop is still vectorized:
>
> t.c:74:5: note: Cost model analysis:
>   Vector inside of loop cost: 3
>   Vector prologue cost: 1
>   Vector epilogue cost: 7
>   Scalar iteration cost: 3
>   Scalar outside cost: 0
>   Vector outside cost: 8
>   prologue iterations: 0
>   epilogue iterations: 0
>   Calculated minimum iters for profitability: 4
>
> but likely this isn't profitable either?
>
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