| Message ID | 20190402073317.56529-1-ndesaulniers@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v4] Makefile: lld: tell clang to use lld | expand |
On Tue, Apr 02, 2019 at 12:33:17AM -0700, Nick Desaulniers wrote: > This is needed because clang doesn't select which linker to use based on > $LD but rather -fuse-ld={bfd,gold,lld,<absolute path to linker>}. This > is problematic especially for cc-ldoption, which checks for linker flag > support via invoking the compiler, rather than the linker. > > Select the linker via absolute path from $PATH via `which`. This allows > you to build with: > > $ make LD=ld.lld > $ make LD=ld.lld-8 > $ make LD=/path/to/ld.lld > > Add -Qunused-arguments to KBUILD_CPPFLAGS sooner, as otherwise > Clang likes to complain about -fuse-lld= being unused when compiling but > not linking (-c) such as when cc-option is used. There's no need to > guard with cc-option. > > Link: https://github.com/ClangBuiltLinux/linux/issues/342 > Link: https://github.com/ClangBuiltLinux/linux/issues/366 > Link: https://github.com/ClangBuiltLinux/linux/issues/357 > Suggested-by: Nathan Chancellor <natechancellor@gmail.com> > Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Tested-by: Nathan Chancellor <natechancellor@gmail.com> > --- > Changes V3->V4: > * Unconditionally add -Qunused-arguments sooners, as per Nathan. > * Slight modification to commit message for that point. > Changes V2->V3: > * Use absolute path based on `which $LD` as per Masahiro. > * Add -Qunused-arguments. > * Drop tested-by/reviewed-by tags, since this patched has changed enough > to warrant re-testing/re-review, IMO. > * Add more info to the commit message. > Changes V1->V2: > * add reviewed and tested by tags. > * move this addition up 2 statments so that it's properly added to > KBUILD_*FLAGS as per Nathan. > > Makefile | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/Makefile b/Makefile > index 026fbc450906..b290e76e1ca5 100644 > --- a/Makefile > +++ b/Makefile > @@ -514,6 +514,10 @@ ifneq ($(GCC_TOOLCHAIN),) > CLANG_FLAGS += --gcc-toolchain=$(GCC_TOOLCHAIN) > endif > CLANG_FLAGS += -no-integrated-as > +ifneq ($(shell $(LD) --version 2>&1 | head -n 1 | grep LLD),) > +CLANG_FLAGS += -fuse-ld=$(shell which $(LD)) > +endif > +KBUILD_CPPFLAGS += -Qunused-arguments > KBUILD_CFLAGS += $(CLANG_FLAGS) > KBUILD_AFLAGS += $(CLANG_FLAGS) > export CLANG_FLAGS > @@ -716,7 +720,6 @@ stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG) := -fstack-protector-strong > KBUILD_CFLAGS += $(stackp-flags-y) > > ifdef CONFIG_CC_IS_CLANG > -KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,) > KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier) > KBUILD_CFLAGS += $(call cc-disable-warning, gnu) > KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) > -- > 2.21.0.392.gf8f6787159e-goog >
diff --git a/Makefile b/Makefile index 026fbc450906..b290e76e1ca5 100644 --- a/Makefile +++ b/Makefile @@ -514,6 +514,10 @@ ifneq ($(GCC_TOOLCHAIN),) CLANG_FLAGS += --gcc-toolchain=$(GCC_TOOLCHAIN) endif CLANG_FLAGS += -no-integrated-as +ifneq ($(shell $(LD) --version 2>&1 | head -n 1 | grep LLD),) +CLANG_FLAGS += -fuse-ld=$(shell which $(LD)) +endif +KBUILD_CPPFLAGS += -Qunused-arguments KBUILD_CFLAGS += $(CLANG_FLAGS) KBUILD_AFLAGS += $(CLANG_FLAGS) export CLANG_FLAGS @@ -716,7 +720,6 @@ stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG) := -fstack-protector-strong KBUILD_CFLAGS += $(stackp-flags-y) ifdef CONFIG_CC_IS_CLANG -KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,) KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier) KBUILD_CFLAGS += $(call cc-disable-warning, gnu) KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
This is needed because clang doesn't select which linker to use based on $LD but rather -fuse-ld={bfd,gold,lld,<absolute path to linker>}. This is problematic especially for cc-ldoption, which checks for linker flag support via invoking the compiler, rather than the linker. Select the linker via absolute path from $PATH via `which`. This allows you to build with: $ make LD=ld.lld $ make LD=ld.lld-8 $ make LD=/path/to/ld.lld Add -Qunused-arguments to KBUILD_CPPFLAGS sooner, as otherwise Clang likes to complain about -fuse-lld= being unused when compiling but not linking (-c) such as when cc-option is used. There's no need to guard with cc-option. Link: https://github.com/ClangBuiltLinux/linux/issues/342 Link: https://github.com/ClangBuiltLinux/linux/issues/366 Link: https://github.com/ClangBuiltLinux/linux/issues/357 Suggested-by: Nathan Chancellor <natechancellor@gmail.com> Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> --- Changes V3->V4: * Unconditionally add -Qunused-arguments sooners, as per Nathan. * Slight modification to commit message for that point. Changes V2->V3: * Use absolute path based on `which $LD` as per Masahiro. * Add -Qunused-arguments. * Drop tested-by/reviewed-by tags, since this patched has changed enough to warrant re-testing/re-review, IMO. * Add more info to the commit message. Changes V1->V2: * add reviewed and tested by tags. * move this addition up 2 statments so that it's properly added to KBUILD_*FLAGS as per Nathan. Makefile | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) -- 2.21.0.392.gf8f6787159e-goog