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Re: [Patch AArch64 1/3] Enable CRC by default for armv8.1-a
- From: James Greenhalgh <james dot greenhalgh at arm dot com>
- To: Christophe Lyon <christophe dot lyon at linaro dot org>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, nd at arm dot com, Marcus Shawcroft <marcus dot shawcroft at arm dot com>, Richard Earnshaw <richard dot earnshaw at arm dot com>
- Date: Thu, 7 Apr 2016 17:51:48 +0100
- Subject: Re: [Patch AArch64 1/3] Enable CRC by default for armv8.1-a
- Authentication-results: sourceware.org; auth=none
- References: <1459937403-22657-1-git-send-email-james dot greenhalgh at arm dot com> <1459937403-22657-2-git-send-email-james dot greenhalgh at arm dot com> <CAKdteOawbrV5LCrqVO1=UnAkHpDgL2mAg2JaK7M8coX3SKxOVA at mail dot gmail dot com>
On Thu, Apr 07, 2016 at 05:23:59PM +0200, Christophe Lyon wrote:
> On 6 April 2016 at 12:10, James Greenhalgh <james.greenhalgh@arm.com> wrote:
> >
> > Hi,
> >
> > This change reflects binutils support for CRC, where it is always enabled
> > for armv8.1-a.
> >
>
> Does v8.1 always enable CRC?
Yes. -march=armv8.1-a should always enable CRC. Unfortunately some
binutils versions do not honour this, which is why in the next patch we
must always put +crc out.
> If not, then don't you want to change the binutils default instead?
No, this patch is the correct thing to do - regadless of what binutils does,
GCC should enable access to the CRC intrinsics with -march=armv8.1-a, so we
want this patch.
Thanks,
James
> > ---
> > 2016-04-06 James Greenhalgh <james.greenhalgh@arm.com>
> >
> > * config/aarch64/aarch64.h (AARCH64_FL_FOR_ARCH8_1): Also add
> > AARCH64_FL_CRC.
> >