From 3b6407b8ed95594de6ee4fddd3239e8841b4d2d6 Mon Sep 17 00:00:00 2001 From: Tom Rini Date: Sun, 22 Apr 2018 19:15:03 -0400 Subject: [PATCH] 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 --- arch/arm/config.mk | 5 ++--- doc/README.clang | 18 +++++++----------- 2 files changed, 9 insertions(+), 14 deletions(-) diff --git a/arch/arm/config.mk b/arch/arm/config.mk index 9c213b897c..b448ed0b3e 100644 --- a/arch/arm/config.mk +++ b/arch/arm/config.mk @@ -23,9 +23,8 @@ PLATFORM_RELFLAGS += $(call cc-option, -msoft-float) \ $(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,)) # LLVM support -LLVMS_RELFLAGS := $(call cc-option,-mllvm,) \ - $(call cc-option,-target arm-none-eabi,) \ - $(call cc-option,-arm-use-movt=0,) +LLVM_RELFLAGS := $(call cc-option,-mllvm,) \ + $(call cc-option,-mno-movt,) PLATFORM_RELFLAGS += $(LLVM_RELFLAGS) PLATFORM_CPPFLAGS += -D__ARM__ diff --git a/doc/README.clang b/doc/README.clang index e0491b2d7e..475bb1e2ed 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 -- 2.25.1