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Re: [PATCH, AArch64] Disable reg offset in quad-word store for Falkor.
- From: Jim Wilson <jim dot wilson at linaro dot org>
- To: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
- Cc: Jim Wilson <jim dot wilson at linaro dot org>, Jim Wilson <wilson at tuliptree dot org>
- Date: Fri, 22 Sep 2017 08:59:31 -0700
- Subject: Re: [PATCH, AArch64] Disable reg offset in quad-word store for Falkor.
- Authentication-results: sourceware.org; auth=none
- References: <1506095357-3334-1-git-send-email-jim.wilson@linaro.org>
On Fri, Sep 22, 2017 at 8:49 AM, Jim Wilson <jim.wilson@linaro.org> wrote:
> On Falkor, because of an idiosyncracy of how the pipelines are designed, a
> quad-word store using a reg+reg addressing mode is almost twice as slow as an
> add followed by a quad-word store with a single reg addressing mode. So we
> get better performance if we disallow addressing modes using register offsets
> with quad-word stores.
This was tested with a bootstrap and make check of course. Also,
gcc.c-torture/compile/20021212-1.c compiled with -O3 -mcpu=falkor
makes a nice testcase to demonstrate that the patch works.
OK?
Jim