| Bin Meng | 7557405 | 2016-02-05 19:30:11 -0800 | [diff] [blame] | 1 | The biggest problem when trying to compile U-Boot with clang is that |
| Jeroen Hofstee | 2e571e9 | 2014-09-10 20:08:52 +0200 | [diff] [blame] | 2 | almost all archs rely on storing gd in a global register and clang user |
| 3 | manual states: "clang does not support global register variables; this |
| 4 | is unlikely to be implemented soon because it requires additional LLVM |
| 5 | backend support." |
| 6 | |
| 7 | Since version 3.4 the ARM backend can be instructed to leave r9 alone. |
| 8 | Global registers themselves are not supported so some inline assembly is |
| 9 | used to get its value. This does lead to larger code then strictly |
| 10 | necessary, but at least works. |
| 11 | |
| 12 | NOTE: target compilation only work for _some_ ARM boards at the moment. |
| Tom Rini | da62bb9 | 2018-04-22 19:15:03 -0400 | [diff] [blame] | 13 | Also AArch64 is not supported currently due to a lack of private libgcc |
| 14 | support. Boards which reassign gd in c will also fail to compile, but there is |
| 15 | in no strict reason to do so in the ARM world, since crt0.S takes care of this. |
| 16 | These assignments can be avoided by changing the init calls but this is not in |
| 17 | mainline yet. |
| Jeroen Hofstee | 2e571e9 | 2014-09-10 20:08:52 +0200 | [diff] [blame] | 18 | |
| 19 | Debian (based) |
| 20 | -------------- |
| 21 | Binary packages can be installed as usual, e.g.: |
| 22 | sudo apt-get install clang |
| 23 | |
| Tom Rini | 1088ec1 | 2016-03-16 19:55:55 -0400 | [diff] [blame] | 24 | Note that we still use binutils for some tools so we must continue to set |
| 25 | CROSS_COMPILE. To compile U-Boot with clang on linux without IAS use e.g.: |
| 26 | make HOSTCC=clang rpi_2_defconfig |
| Tom Rini | da62bb9 | 2018-04-22 19:15:03 -0400 | [diff] [blame] | 27 | make HOSTCC=clang CROSS_COMPILE=arm-linux-gnueabi- \ |
| 28 | CC="clang -target arm-linux-gnueabi" -j8 |
| Jeroen Hofstee | 2e571e9 | 2014-09-10 20:08:52 +0200 | [diff] [blame] | 29 | |
| Tom Rini | 689de5f | 2016-03-16 20:40:20 -0400 | [diff] [blame] | 30 | It can also be used to compile sandbox: |
| 31 | make HOSTCC=clang sandbox_defconfig |
| 32 | make HOSTCC=clang CC=clang -j8 |
| 33 | |
| Jeroen Hofstee | 2e571e9 | 2014-09-10 20:08:52 +0200 | [diff] [blame] | 34 | FreeBSD 11 (Current): |
| 35 | -------------------- |
| 36 | Since llvm 3.4 is currently in the base system, the integrated as is |
| Jeroen Hofstee | 432710c | 2014-09-21 10:20:22 +0200 | [diff] [blame] | 37 | incapable of building U-Boot. Therefore gas from devel/arm-gnueabi-binutils |
| Jeroen Hofstee | 2e571e9 | 2014-09-10 20:08:52 +0200 | [diff] [blame] | 38 | is used instead. It needs a symlinks to be picked up correctly though: |
| 39 | |
| Jeroen Hofstee | 432710c | 2014-09-21 10:20:22 +0200 | [diff] [blame] | 40 | ln -s /usr/local/bin/arm-gnueabi-freebsd-as /usr/bin/arm-freebsd-eabi-as |
| Jeroen Hofstee | 2e571e9 | 2014-09-10 20:08:52 +0200 | [diff] [blame] | 41 | |
| 42 | # The following commands compile U-Boot using the clang xdev toolchain. |
| 43 | # NOTE: CROSS_COMPILE and target differ on purpose! |
| Jeroen Hofstee | 432710c | 2014-09-21 10:20:22 +0200 | [diff] [blame] | 44 | export CROSS_COMPILE=arm-gnueabi-freebsd- |
| Tom Rini | 1088ec1 | 2016-03-16 19:55:55 -0400 | [diff] [blame] | 45 | gmake rpi_2_defconfig |
| 46 | gmake CC="clang -target arm-freebsd-eabi --sysroot /usr/arm-freebsd" -j8 |
| Jeroen Hofstee | 2e571e9 | 2014-09-10 20:08:52 +0200 | [diff] [blame] | 47 | |
| Bin Meng | 7557405 | 2016-02-05 19:30:11 -0800 | [diff] [blame] | 48 | Given that U-Boot will default to gcc, above commands can be |
| Jeroen Hofstee | 2e571e9 | 2014-09-10 20:08:52 +0200 | [diff] [blame] | 49 | simplified with a simple wrapper script, listed below. |
| 50 | |
| Jeroen Hofstee | 432710c | 2014-09-21 10:20:22 +0200 | [diff] [blame] | 51 | /usr/local/bin/arm-gnueabi-freebsd-gcc |
| Jeroen Hofstee | 2e571e9 | 2014-09-10 20:08:52 +0200 | [diff] [blame] | 52 | --- |
| 53 | #!/bin/sh |
| 54 | |
| Tom Rini | 1088ec1 | 2016-03-16 19:55:55 -0400 | [diff] [blame] | 55 | exec clang -target arm-freebsd-eabi --sysroot /usr/arm-freebsd "$@" |