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authorTom Rini2018-04-22 19:15:03 -0400
committerTom Rini2018-04-27 14:54:49 -0400
commit3b6407b8ed95594de6ee4fddd3239e8841b4d2d6 (patch)
tree1d63fdae996ec5b9b230e65674a086de3794a10d /doc/README.clang
parent4760fe26c72563d284cd620421dc8196006ce5e3 (diff)
clang: Update documentation
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>
Diffstat (limited to 'doc/README.clang')
-rw-r--r--doc/README.clang18
1 files changed, 7 insertions, 11 deletions
diff --git a/doc/README.clang b/doc/README.clang
index e0491b2d7e6..475bb1e2ed8 100644
--- a/doc/README.clang
+++ b/doc/README.clang
@@ -10,16 +10,11 @@ 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: Most notably boards which aren't using
-the generic board will fail to compile, but since those are expected
-to be converted this will solve itself. 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.
-
-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.
+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)
--------------
@@ -29,7 +24,8 @@ 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 -j8
+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