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Re: [PATCH,rs6000] Fine-tune vec_construct direct move cost
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: Bill Schmidt <wschmidt at linux dot vnet dot ibm dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Fri, 21 Jul 2017 17:25:27 -0500
- Subject: Re: [PATCH,rs6000] Fine-tune vec_construct direct move cost
- Authentication-results: sourceware.org; auth=none
- References: <11780563-05d5-07a5-73cc-93ffe8264c2d@linux.vnet.ibm.com>
Hi Bill,
On Fri, Jul 21, 2017 at 10:40:43AM -0500, Bill Schmidt wrote:
> In https://gcc.gnu.org/ml/gcc-patches/2017-05/msg00924.html, I raised the
> vectorization cost for a vec_construct operation that requires direct
> moves between GPRs and VSRs. The cost equation I substituted has since
> proven to be slightly more conservative than attended, and we're seeing
> some cases of SLP vectorization being avoided that should not be. This
> patch adjusts the equation to reduce the cost somewhat.
>
> I've tested this to ensure the cases previously seen are now being
> vectorized again, and done some benchmark testing that shows no measurable
> result, positive or negative. So this is just minor fine-tuning, but
> still important to get right.
>
> Bootstrapped and tested on powerpc64le-unknown-linux-gnu with no regressions.
> Is this ok for trunk?
Sure, thanks!
Segher