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[97.120.209.236]) by smtp.gmail.com with ESMTPSA id m126sm349784oib.55.2021.07.01.18.05.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 01 Jul 2021 18:05:49 -0700 (PDT) Subject: Re: [PATCH] arm64: drop CROSS_COMPILE for LLVM=1 LLVM_IAS=1 To: Nick Desaulniers , Catalin Marinas , Will Deacon Cc: Masahiro Yamada , Arnd Bergmann , Fangrui Song , Nathan Chancellor , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com References: <20210701235505.1792711-1-ndesaulniers@google.com> From: Tom Stellard Message-ID: Date: Thu, 1 Jul 2021 18:05:47 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <20210701235505.1792711-1-ndesaulniers@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/1/21 4:55 PM, 'Nick Desaulniers' via Clang Built Linux wrote: > We get constant feedback that the command line invocation of make is too > long. CROSS_COMPILE is helpful when a toolchain has a prefix of the > target triple, or is an absolute path outside of $PATH, but it's mostly > redundant for a given ARCH. > > If CROSS_COMPILE is not set, simply set --target=aarch64-linux for > CLANG_FLAGS, KBUILD_CFLAGS, and KBUILD_AFLAGS. > > Previously, we'd cross compile via: > $ ARCH=arm64 CROSS_COMPILE=aarch64-linxu-gnu make LLVM=1 LLVM_IAS=1 > Now: > $ ARCH=arm64 make LLVM=1 LLVM_IAS=1 > > We can drop gnu from the triple, but dropping linux from the triple > produces different .config files for the above invocations for the > defconfig target. > > Link: https://github.com/ClangBuiltLinux/linux/issues/1399 > Suggested-by: Arnd Bergmann > Suggested-by: Fangrui Song > Signed-off-by: Nick Desaulniers > --- > arch/arm64/Makefile | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile > index 7bc37d0a1b68..016873fddcc3 100644 > --- a/arch/arm64/Makefile > +++ b/arch/arm64/Makefile Are there plans to do this for other architectures? -Tom > @@ -34,6 +34,17 @@ $(warning LSE atomics not supported by binutils) > endif > endif > > +ifneq ($(LLVM),) > +ifneq ($(LLVM_IAS),) > +ifeq ($(CROSS_COMPILE),) > +CLANG_TARGET :=--target=aarch64-linux > +CLANG_FLAGS += $(CLANG_TARGET) > +KBUILD_CFLAGS += $(CLANG_TARGET) > +KBUILD_AFLAGS += $(CLANG_TARGET) > +endif > +endif > +endif > + > cc_has_k_constraint := $(call try-run,echo \ > 'int main(void) { \ > asm volatile("and w0, w0, %w0" :: "K" (4294967295)); \ >