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8896b815f1
The build logic in source/cmake/FindNeon.cmake caused the x265 build
system to always think that the CPU supports neon: it was looking in
/proc/cpuinfo, which of course is wrong when cross-compilation, but
then the sequence of grep was interacting badly with CMake, causing
the build system to always conclude that the CPU supports NEON.
This causes runtime issues on ARMv6.
Setting -DCROSS_COMPILE_ARM=1 fixes this, as it tells the x265 build
system we are cross-compiling and it skips its bogus NEON check. So
for ARMv6, we pass -DCROSS_COMPILE_ARM=1.
But then, we still want NEON for ARMv7 processors with NEON, so this
commit adds a patch that allows to explicitly specify whether the CPU
supports NEON, in the -DCROSS_COMPILE_ARM=1 case, and we use this
option when BR2_ARM_CPU_HAS_NEON.
For those wondering why -DCROSS_COMPILE_ARM=1 is not passed for all
ARM platforms: it's because from the perspective of x265, only ARM >=
v6 is ARM: it has assembly code that needs at least ARMv6. Earlier ARM
platforms are not detected as ARM by the x265 build logic, and
therefore fallback on generic code.
This has been build-tested on:
- ARMv5: generic code is used, no assembly
- ARMv6: assembly code is used, but not with NEON support
- ARMv7 with NEON: assembly code is used, with NEON support
Reported-by: David Barbion <davidb@230ruedubac.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 1fbd26f831)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Buildroot is a simple, efficient and easy-to-use tool to generate embedded Linux systems through cross-compilation. The documentation can be found in docs/manual. You can generate a text document with 'make manual-text' and read output/docs/manual/manual.text. Online documentation can be found at http://buildroot.org/docs.html To build and use the buildroot stuff, do the following: 1) run 'make menuconfig' 2) select the target architecture and the packages you wish to compile 3) run 'make' 4) wait while it compiles 5) find the kernel, bootloader, root filesystem, etc. in output/images You do not need to be root to build or run buildroot. Have fun! Buildroot comes with a basic configuration for a number of boards. Run 'make list-defconfigs' to view the list of provided configurations. Please feed suggestions, bug reports, insults, and bribes back to the buildroot mailing list: buildroot@buildroot.org You can also find us on #buildroot on OFTC IRC. If you would like to contribute patches, please read https://buildroot.org/manual.html#submitting-patches