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From: Ruifeng Wang <Ruifeng.Wang@arm.com>
To: "thomas@monjalon.net" <thomas@monjalon.net>,
	Juraj Linkeš <juraj.linkes@pantheon.tech>
Cc: "bruce.richardson@intel.com" <bruce.richardson@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	"jerinj@marvell.com" <jerinj@marvell.com>,
	Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	nd <nd@arm.com>
Subject: Re: [dpdk-dev] [PATCH] build: add -moutline-atomics to default Arm build
Date: Fri, 9 Oct 2020 05:29:44 +0000
Message-ID: <VI1PR0802MB2351477F94F0BBF79092156E9E080@VI1PR0802MB2351.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <6308231.oPsEYrQ9EY@thomas>


> -----Original Message-----
> From: Thomas Monjalon <thomas@monjalon.net>
> Sent: Wednesday, October 7, 2020 4:14 AM
> To: Juraj Linkeš <juraj.linkes@pantheon.tech>
> Cc: bruce.richardson@intel.com; dev@dpdk.org; jerinj@marvell.com;
> Ruifeng Wang <Ruifeng.Wang@arm.com>; Honnappa Nagarahalli
> <Honnappa.Nagarahalli@arm.com>
> Subject: Re: [dpdk-dev] [PATCH] build: add -moutline-atomics to default Arm
> build
> 
> 01/10/2020 08:19, Juraj Linkeš:
> > -moutline-atomics allows LSE instructions to be used if available when
> > compiling for ARMv8.0 instruction set. It's enabled by default on
> > newer compilers, such as gcc-10.1. Enable the option so that earlier
> > compiler versions that support it but don't enable it by default build with it.
> >
> > Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> > ---
> >  machine_args_generic = [
> > -	['default', ['-march=armv8-a+crc']],
> > +	['default', ['-march=armv8-a+crc', '-moutline-atomics']],
> >  	['native', ['-march=native']],
> >  	['0xd03', ['-mcpu=cortex-a53']],
> >  	['0xd04', ['-mcpu=cortex-a35']],
> 
> Why is it added only to the target "default"?
> 
Because 'default' target generates Armv8.0 instruction set which doesn't include LSE extension. 
The flag enables LSE instructions when code runs on platforms that implements LSE extension.

For other targets, machine specific 'mcpu' or 'march' flags are used. LSE extension availability can be inferred from the given flags.
So there is not need to add '-moutline-atomics' to them. 

  reply	other threads:[~2020-10-09  5:30 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-01  6:19 Juraj Linkeš
2020-10-06 20:14 ` Thomas Monjalon
2020-10-09  5:29   ` Ruifeng Wang [this message]
2020-10-09  6:52     ` Thomas Monjalon
2020-10-09  7:07       ` Ruifeng Wang
2020-10-09  9:50 ` [dpdk-dev] [PATCH v2] " Juraj Linkeš
2020-10-13 13:16   ` Thomas Monjalon

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