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Re: [PATCH, PR 49089] Don't split AVX256 unaligned loads by default on bdver1 and generic
- From: Richard Guenther <richard dot guenther at gmail dot com>
- To: "Fang, Changpeng" <Changpeng dot Fang at amd dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, "hjl dot tools at gmail dot com" <hjl dot tools at gmail dot com>
- Date: Tue, 14 Jun 2011 12:13:47 +0200
- Subject: Re: [PATCH, PR 49089] Don't split AVX256 unaligned loads by default on bdver1 and generic
- References: <D4C76825A6780047854A11E93CDE84D005980DC6E8@SAUSEXMBP01.amd.com>
On Tue, Jun 14, 2011 at 1:59 AM, Fang, Changpeng <Changpeng.Fang@amd.com> wrote:
> Hi,
>
> The patch ( http://gcc.gnu.org/ml/gcc-patches/2011-02/txt00059.txt ) which introduces splitting avx256 unaligned loads.
> However, we found that it causes significant regressions for cpu2006 ( http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49089 ).
>
> In this work, we introduce a tune option that sets splitting unaligned loads default only for such CPUs that such splitting
> is beneficial.
>
> The patch passed bootstrapping and regression tests on x86_64-unknown-linux-gnu system.
>
> Is it OK to commit?
It probably should go to the 4.6 branch as well. Note that I find the
X86_TUNE_AVX256_SPLIT_UNALIGNED_LOAD_OPTIMAL odd,
why not call it simply X86_TUNE_AVX256_SPLIT_UNALIGNED_LOAD?
I'll defer to x86 maintainers for approval.
Richard.
> Thanks,
>
> Changpeng