mirror of
https://github.com/smaeul/u-boot.git
synced 2025-11-03 21:48:15 +00:00
3b6407b8ed
As of clang-5.0, things have changed a bit. First, we cannot automatically guess -target values as if we do not pass one with CC then cc-option will fail. Second, to disable movt/movw relocations the argument has become -mno-movt. Related to the target part, we cannot use arm-none-eabi as that ends up being too generic of an ARM target for things like say rpi_3_32b to work. Signed-off-by: Tom Rini <trini@konsulko.com>
56 lines
2.2 KiB
Plaintext
56 lines
2.2 KiB
Plaintext
The biggest problem when trying to compile U-Boot with clang is that
|
|
almost all archs rely on storing gd in a global register and clang user
|
|
manual states: "clang does not support global register variables; this
|
|
is unlikely to be implemented soon because it requires additional LLVM
|
|
backend support."
|
|
|
|
Since version 3.4 the ARM backend can be instructed to leave r9 alone.
|
|
Global registers themselves are not supported so some inline assembly is
|
|
used to get its value. This does lead to larger code then strictly
|
|
necessary, but at least works.
|
|
|
|
NOTE: target compilation only work for _some_ ARM boards at the moment.
|
|
Also AArch64 is not supported currently due to a lack of private libgcc
|
|
support. Boards which reassign gd in c will also fail to compile, but there is
|
|
in no strict reason to do so in the ARM world, since crt0.S takes care of this.
|
|
These assignments can be avoided by changing the init calls but this is not in
|
|
mainline yet.
|
|
|
|
Debian (based)
|
|
--------------
|
|
Binary packages can be installed as usual, e.g.:
|
|
sudo apt-get install clang
|
|
|
|
Note that we still use binutils for some tools so we must continue to set
|
|
CROSS_COMPILE. To compile U-Boot with clang on linux without IAS use e.g.:
|
|
make HOSTCC=clang rpi_2_defconfig
|
|
make HOSTCC=clang CROSS_COMPILE=arm-linux-gnueabi- \
|
|
CC="clang -target arm-linux-gnueabi" -j8
|
|
|
|
It can also be used to compile sandbox:
|
|
make HOSTCC=clang sandbox_defconfig
|
|
make HOSTCC=clang CC=clang -j8
|
|
|
|
FreeBSD 11 (Current):
|
|
--------------------
|
|
Since llvm 3.4 is currently in the base system, the integrated as is
|
|
incapable of building U-Boot. Therefore gas from devel/arm-gnueabi-binutils
|
|
is used instead. It needs a symlinks to be picked up correctly though:
|
|
|
|
ln -s /usr/local/bin/arm-gnueabi-freebsd-as /usr/bin/arm-freebsd-eabi-as
|
|
|
|
# The following commands compile U-Boot using the clang xdev toolchain.
|
|
# NOTE: CROSS_COMPILE and target differ on purpose!
|
|
export CROSS_COMPILE=arm-gnueabi-freebsd-
|
|
gmake rpi_2_defconfig
|
|
gmake CC="clang -target arm-freebsd-eabi --sysroot /usr/arm-freebsd" -j8
|
|
|
|
Given that U-Boot will default to gcc, above commands can be
|
|
simplified with a simple wrapper script, listed below.
|
|
|
|
/usr/local/bin/arm-gnueabi-freebsd-gcc
|
|
---
|
|
#!/bin/sh
|
|
|
|
exec clang -target arm-freebsd-eabi --sysroot /usr/arm-freebsd "$@"
|