All of lore.kernel.org
 help / color / mirror / Atom feed
* [Buildroot] [git commit branch/2022.05.x] Revert "configs/olimex_a20_olinuxino_lime: use NEON+VFPv4 as FPU strategy"
@ 2022-09-16 21:44 Peter Korsgaard
  0 siblings, 0 replies; only message in thread
From: Peter Korsgaard @ 2022-09-16 21:44 UTC (permalink / raw)
  To: buildroot

commit: https://git.buildroot.net/buildroot/commit/?id=c50df50138874aafc0ecd8104dc0aa69ee14b56e
branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/2022.05.x

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 115ee0521430d89db8be1a79457b0721ceafc484.

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
(cherry picked from commit d5c1e67d3adf4d5c32e94ad7eac7a940fb17f9f0)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
---
 configs/olimex_a20_olinuxino_lime_defconfig | 1 -
 1 file changed, 1 deletion(-)

diff --git a/configs/olimex_a20_olinuxino_lime_defconfig b/configs/olimex_a20_olinuxino_lime_defconfig
index e24857e0c1..8403566a67 100644
--- a/configs/olimex_a20_olinuxino_lime_defconfig
+++ b/configs/olimex_a20_olinuxino_lime_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
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot

^ permalink raw reply related	[flat|nested] only message in thread

only message in thread, other threads:[~2022-09-16 21:59 UTC | newest]

Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-09-16 21:44 [Buildroot] [git commit branch/2022.05.x] Revert "configs/olimex_a20_olinuxino_lime: use NEON+VFPv4 as FPU strategy" Peter Korsgaard

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.