12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455 |
- 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 "$@"
|