From: Giulio Benetti <giulio.benetti@benettiengineering.com>
To: buildroot@buildroot.org
Cc: Giulio Benetti <giulio.benetti@benettiengineering.com>,
Luca Ceresoli <luca.ceresoli@bootlin.com>,
Jagan Teki <jagan@amarulasolutions.com>,
"Yann E . MORIN" <yann.morin.1998@free.fr>
Subject: [Buildroot] [PATCH 2/4] Revert "configs/olimex_a20_olinuxino_lime2: use NEON+VFPv4 as FPU strategy"
Date: Mon, 15 Aug 2022 17:48:52 +0200 [thread overview]
Message-ID: <20220815154854.17628-3-giulio.benetti@benettiengineering.com> (raw)
In-Reply-To: <20220815154854.17628-1-giulio.benetti@benettiengineering.com>
The gcc man page states that specifying Neon as part of the fpu setting
has no effect, unless the -funsafe-math-optimizations is also specified,
because Neon is not compliant with IEEE 754:
```
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.
```
-funsafe-math-optimizations must be explictly specified per package to
really use NEON as FPU, but it's something that is left to the user as
well as setting BR2_ARM_FPU_NEON_VFPV4. This way the default
BR2_ARM_FPU_VFPV4D16 is used as previously. So let's revert the
offending patch.
This reverts commit f8528acdfda278ea9f2f9bc8a47eb77ace0c050f.
Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
---
configs/olimex_a20_olinuxino_lime2_defconfig | 1 -
1 file changed, 1 deletion(-)
diff --git a/configs/olimex_a20_olinuxino_lime2_defconfig b/configs/olimex_a20_olinuxino_lime2_defconfig
index a032eb922f..e325184e9e 100644
--- a/configs/olimex_a20_olinuxino_lime2_defconfig
+++ b/configs/olimex_a20_olinuxino_lime2_defconfig
@@ -2,7 +2,6 @@
BR2_arm=y
BR2_cortex_a7=y
BR2_ARM_EABIHF=y
-BR2_ARM_FPU_NEON_VFPV4=y
# Linux headers same as kernel, a 5.15 LTS series
BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_5_15=y
--
2.34.1
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next prev parent reply other threads:[~2022-08-15 15:49 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-15 15:48 [Buildroot] [PATCH 0/4] Revert wrong NEON/VFPV4 FPU strategy Giulio Benetti
2022-08-15 15:48 ` [Buildroot] [PATCH 1/4] Revert "configs/olimex_a33_olinuxino: use NEON+VFPv4 as FPU strategy" Giulio Benetti
2022-08-16 20:46 ` Arnout Vandecappelle
2022-08-18 23:20 ` Giulio Benetti
2022-09-16 21:46 ` Peter Korsgaard
2022-08-15 15:48 ` Giulio Benetti [this message]
2022-09-16 21:46 ` [Buildroot] [PATCH 2/4] Revert "configs/olimex_a20_olinuxino_lime2: " Peter Korsgaard
2022-08-15 15:48 ` [Buildroot] [PATCH 3/4] Revert "configs/olimex_a20_olinuxino_lime: " Giulio Benetti
2022-09-16 21:46 ` Peter Korsgaard
2022-08-15 15:48 ` [Buildroot] [PATCH 4/4] Revert "configs/bananapi_m1: " Giulio Benetti
2022-09-16 21:47 ` Peter Korsgaard
2022-08-15 19:05 ` [Buildroot] [PATCH 0/4] Revert wrong NEON/VFPV4 FPU strategy Yann E. MORIN
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