-The biggest problem when trying to compile U-boot with clang is that
+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
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.
-NOTE: without the -mllvm -arm-use-movt=0 flags u-boot will compile
+NOTE: without the -mllvm -arm-use-movt=0 flags U-Boot will compile
fine, but llvm might hardcode addresses in movw / movt pairs, which
-cannot be relocated and u-boot will fail at runtime.
+cannot be relocated and U-Boot will fail at runtime.
Debian (based)
--------------
Binary packages can be installed as usual, e.g.:
sudo apt-get install clang
-To compile U-Boot with clang on linux without IAS use e.g.:
-export TRIPLET=arm-linux-gnueabi && export CROSS_COMPILE="$TRIPLET-"
-make HOSTCC=clang CC="clang -target $TRIPLET -mllvm -arm-use-movt=0 -no-integrated-as" rpi_b_defconfig
-make HOSTCC=clang CC="clang -target $TRIPLET -mllvm -arm-use-movt=0 -no-integrated-as" all V=1 -j8
+Note that we still use binutils for some tools so we must continue to set
+CROSS_COMPILE. To compile U-Boot with clang on linux without IAS use e.g.:
+make HOSTCC=clang rpi_2_defconfig
+make HOSTCC=clang CROSS_COMPILE=arm-linux-gnueabi- CC=clang -j8
+
+It can also be used to compile sandbox:
+make HOSTCC=clang sandbox_defconfig
+make HOSTCC=clang CC=clang -j8
FreeBSD 11 (Current):
--------------------
# The following commands compile U-Boot using the clang xdev toolchain.
# NOTE: CROSS_COMPILE and target differ on purpose!
export CROSS_COMPILE=arm-gnueabi-freebsd-
-gmake CC="clang -target arm-freebsd-eabi --sysroot /usr/arm-freebsd -no-integrated-as -mllvm -arm-use-movt=0" rpi_b_defconfig
-gmake CC="clang -target arm-freebsd-eabi --sysroot /usr/arm-freebsd -no-integrated-as -mllvm -arm-use-movt=0" -j8
+gmake rpi_2_defconfig
+gmake CC="clang -target arm-freebsd-eabi --sysroot /usr/arm-freebsd" -j8
-Given that u-boot will default to gcc, above commands can be
+Given that U-Boot will default to gcc, above commands can be
simplified with a simple wrapper script, listed below.
/usr/local/bin/arm-gnueabi-freebsd-gcc
---
#!/bin/sh
-exec clang -target arm-freebsd-eabi --sysroot /usr/arm-freebsd -no-integrated-as -mllvm -arm-use-movt=0 "$@"
-
+exec clang -target arm-freebsd-eabi --sysroot /usr/arm-freebsd "$@"