From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Petazzoni Date: Fri, 16 Sep 2016 18:26:50 +0200 Subject: [Buildroot] [PATCH] configs: nitrogen*: enable NEON support In-Reply-To: References: <20160916130902.23091-1-gary.bisson@boundarydevices.com> <20160916161344.54fed11e@free-electrons.com> Message-ID: <20160916182650.055f49d3@free-electrons.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: buildroot@busybox.net Hello, On Fri, 16 Sep 2016 16:20:42 +0200, Gary Bisson wrote: > Because the first two configurations are for i.MX6 (ARM Cortex-A9) > whereas the last one is i.MX7 (ARM Cortex-A7). > > So relying on Config.in.arm, the Cortex-A9 doesn't have VFPv4: > https://git.buildroot.net/buildroot/tree/arch/Config.in.arm#n125 > https://git.buildroot.net/buildroot/tree/arch/Config.in.arm#n141 OK, then you should be using the VFPv3 instead of the NEON for FPU. Indeed: """ If the selected floating-point hardware includes the NEON extension (e.g. '-mfpu'='neon'), note that floating-point operations are not generated by GCC's auto-vectorization pass unless '-funsafe-math-optimizations' is also specified. This is because NEON hardware does not fully implement the IEEE 754 standard for floating-point arithmetic (in particular denormal values are treated as zero), so the use of NEON instructions may lead to a loss of precision. """ Thomas -- Thomas Petazzoni, CTO, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com