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Sat, 25 Jul 2020 09:55:55 +0200 (CEST) Authentication-Results: phobos.denx.de; dmarc=none (p=none dis=none) header.from=gmx.de Authentication-Results: phobos.denx.de; spf=pass smtp.mailfrom=xypron.glpk@gmx.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1595663753; bh=HZE2xnDdx5gpiDbXHYq8lDLQi6HCpSloxif8CrJ/HNE=; h=X-UI-Sender-Class:From:To:Cc:Subject:Date; b=OJrpsT1hdfhaQEZVxylIgvrZxw3oCcPneg31Tjy03aN+QS1vYawN28zpSeOIo/dM9 n9f6pL1XI6DmkWq5Pd61H+GTerr3nNyrz6T3qFWTUHM5+rMPHbhPJJoAN8ek0rsPz7 xLTICjMCwwBeLEEsTndlruqZcRK/gklcly/3ZBy4= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from workstation5.fritz.box ([178.202.41.107]) by mail.gmx.com (mrgmx105 [212.227.17.174]) with ESMTPSA (Nemesis) id 1MBm1U-1k6uXt2d2a-00CEfS; Sat, 25 Jul 2020 09:55:53 +0200 From: Heinrich Schuchardt To: Tom Rini Cc: Bin Meng , u-boot@lists.denx.de, Heinrich Schuchardt Subject: [PATCH 1/1] doc: move Clang documentation to HTML Date: Sat, 25 Jul 2020 09:55:46 +0200 Message-Id: <20200725075546.37849-1-xypron.glpk@gmx.de> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 X-Provags-ID: V03:K1:NqorBMof5BPh96icBPdxWMUyoU1jWjHC6hiTsDVYCpKj5S0wBMS OLwZf/9l3sjvbchg3a5O8f7fshG1V6zloW2u4rTXEmCwiEej6kx9LlD7J6r7l/L3fMzwuGy WFBP49C6wqMEpXsRk2e0AkCC33DPtD3SwxZMN8Pxxf20Oew3V8kv73aPpN1g8J4iawx8Ggm P6lUbHEX59jglhLzSOngg== X-UI-Out-Filterresults: notjunk:1;V03:K0:9CJYZ4CebTk=:fyUffrI8x6KXHyv49ghjpB 8X1EFOTLyLsziFgJNcTKWowK8OpMf5MROysMLg3GKKeXrMrbwatdh8PrsaNPz5F8O0Pm1HbrZ MTXuUIlVCSned3DRn57Ld1r94qAk3JLKFTHCZbga6WU2N+oO6tCy8tq6dP5jzAOyHYP2pWkOl w7j9KLXt8dbtK1Vfp4K/msDKNEI25B6wsaMukeo+imnFEgLUA/t60fvsS3/Bvq11DVbr47r6N UToSiR4w+mV6jjSO7EZgS+FG02ZNp5aWQdumXlXbX7HmuF7dXqQbTxpUsTTx4uhAFpBALPnpy Tkt4alS7t4e9B7ZNo2ZI87NXOy7QS62zkNUTz0cgjGJ8sO+1wOYO6dxu4L838lZ+oHDDZmczg 7gt1Ao+jYrF78BVCKRKYYfRUSoRcOSlX/yJC/quBef+RERHgUplvpNIQJ2CsSdhPpZQ3SH2WV IRVYEvASpRYvhu8VL2RwVu/OdT6X3vyJZUChHoll+e7jszVvBpCAwYKUskGpsxY+4DbKEnD0W lr7vw9nMKhwan+Pp07l05s8IxLmjm6UWTi8l2jgjSUVOdNJzIxEscB6gGyruozyaSz/w28P1y mR5HkNn7f9p7dtKkm5ROWY22XAbUDQCMLVj8LJ7nuM4TrxL5YWF3O3RYmXT+GwHslr+nmlKqS /qAx6PD6RzRV4tbqRnj6AwkZ25GWLUbrdR6mZFZTu/mAcsg84HNYaWjqBJt52ZMTSCk7tsA0Q i/yvy6JvovBb8gZlEsNyi+UJSore53bNIprtD4PDzrU/tQ4hZBFohzcv7j8DF8Wf2w2NhcCcB esLz4tPlAxfZbIBHZ1m9rKxHRxGmv/xOOWK1n1SGCOVMGRiyZwHKIitlXzV44C4xZgDI16Ex5 ZKaS5atsU0eKNzj3+tArvUoomLBrrGZpY5wA956IEIG67cV830Mf40rHfn67S6YJO8huhUaT6 tSH3fuk4lVLd7etZmbI0YPhcnE8DZAjhyomGnap0BS1Qn/j2UqkW0XCIcYc7YOxYkrHMSDRBx R1utyjxMQVWR2U5WZC500rfinodX06ZbnM/YiKJoXEWWB6p/dUZfHdPD0hkVotHqn6UHfEjvI LMLDxPikxhGoYxWK1d+baF6LfkGJGowuKyBlING/8sWu8wgglfNVwczsmPyp2ZfkH/yHyhEZt 5lvQ27a32aVa7YNGwlc/5e63z4bsUYfPw1nxyPTbMUHggrUAoWCBS7QOjHjj40cnqRoP7kOPt JElSrTSanL4vqwBZ7r0G3ddMs38rKB0/gzfDWMg== X-BeenThere: u-boot@lists.denx.de X-Mailman-Version: 2.1.34 Precedence: list List-Id: U-Boot discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: u-boot-bounces@lists.denx.de Sender: "U-Boot" X-Virus-Scanned: clamav-milter 0.102.3 at phobos.denx.de X-Virus-Status: Clean * Move README.clang to doc/build/clang.rst and reformat as reStructeredText. * Indicate that -ffixed-r9 and -ffixed-x18 are used to reserve registers for gd. * Minor editing. Signed-off-by: Heinrich Schuchardt --- doc/README.clang | 55 -------------------------------- doc/build/clang.rst | 76 +++++++++++++++++++++++++++++++++++++++++++++ doc/build/index.rst | 1 + 3 files changed, 77 insertions(+), 55 deletions(-) delete mode 100644 doc/README.clang create mode 100644 doc/build/clang.rst -- 2.26.2 diff --git a/doc/README.clang b/doc/README.clang deleted file mode 100644 index 475bb1e2ed..0000000000 --- a/doc/README.clang +++ /dev/null @@ -1,55 +0,0 @@ -The biggest problem when trying to compile U-Boot with clang is that -almost all archs rely on storing gd in a global register and clang user -manual states: "clang does not support global register variables; this -is unlikely to be implemented soon because it requires additional LLVM -backend support." - -Since version 3.4 the ARM backend can be instructed to leave r9 alone. -Global registers themselves are not supported so some inline assembly is -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 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) --------------- -Binary packages can be installed as usual, e.g.: -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 -target arm-linux-gnueabi" -j8 - -It can also be used to compile sandbox: -make HOSTCC=clang sandbox_defconfig -make HOSTCC=clang CC=clang -j8 - -FreeBSD 11 (Current): --------------------- -Since llvm 3.4 is currently in the base system, the integrated as is -incapable of building U-Boot. Therefore gas from devel/arm-gnueabi-binutils -is used instead. It needs a symlinks to be picked up correctly though: - -ln -s /usr/local/bin/arm-gnueabi-freebsd-as /usr/bin/arm-freebsd-eabi-as - -# The following commands compile U-Boot using the clang xdev toolchain. -# NOTE: CROSS_COMPILE and target differ on purpose! -export CROSS_COMPILE=arm-gnueabi-freebsd- -gmake rpi_2_defconfig -gmake CC="clang -target arm-freebsd-eabi --sysroot /usr/arm-freebsd" -j8 - -Given that U-Boot will default to gcc, above commands can be -simplified with a simple wrapper script, listed below. - -/usr/local/bin/arm-gnueabi-freebsd-gcc ---- -#!/bin/sh - -exec clang -target arm-freebsd-eabi --sysroot /usr/arm-freebsd "$@" diff --git a/doc/build/clang.rst b/doc/build/clang.rst new file mode 100644 index 0000000000..1d35616eb5 --- /dev/null +++ b/doc/build/clang.rst @@ -0,0 +1,76 @@ +Building with Clang +=================== + +The biggest problem when trying to compile U-Boot with Clang is that almost all +archs rely on storing gd in a global register and the Clang 3.5 user manual +states: "Clang does not support global register variables; this is unlikely to +be implemented soon because it requires additional LLVM backend support." + +The ARM backend can be instructed not to use the r9 and x18 registers using +-ffixed-r9 or -ffixed-x18 respectively. As global registers themselves are not +supported inline assembly is needed to get and set the r9 or x18 value. This +leads 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 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 +------------ + +Required packages can be installed via apt, e.g. + +.. code-block:: bash + + 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. + +.. code-block:: bash + + make HOSTCC=clang rpi_2_defconfig + make HOSTCC=clang CROSS_COMPILE=arm-linux-gnueabi- \ + CC="clang -target arm-linux-gnueabi" -j8 + +It can also be used to compile sandbox: + +.. code-block:: bash + + make HOSTCC=clang sandbox_defconfig + make HOSTCC=clang CC=clang -j8 + + +FreeBSD 11 +---------- + +Since llvm 3.4 is currently in the base system, the integrated assembler as +is incapable of building U-Boot. Therefore gas from devel/arm-gnueabi-binutils +is used instead. It needs a symlink to be picked up correctly though: + +.. code-block:: bash + + ln -s /usr/local/bin/arm-gnueabi-freebsd-as /usr/bin/arm-freebsd-eabi-as + +The following commands compile U-Boot using the Clang xdev toolchain. + +**NOTE:** CROSS_COMPILE and target differ on purpose! + +.. code-block:: bash + + export CROSS_COMPILE=arm-gnueabi-freebsd- + gmake rpi_2_defconfig + gmake CC="clang -target arm-freebsd-eabi --sysroot /usr/arm-freebsd" -j8 + +Given that U-Boot will default to gcc, above commands can be +simplified with a simple wrapper script - saved as +/usr/local/bin/arm-gnueabi-freebsd-gcc - listed below: + +.. code-block:: bash + + #!/bin/sh + exec clang -target arm-freebsd-eabi --sysroot /usr/arm-freebsd "$@" diff --git a/doc/build/index.rst b/doc/build/index.rst index e4e34114af..e0072afb5e 100644 --- a/doc/build/index.rst +++ b/doc/build/index.rst @@ -6,4 +6,5 @@ Build U-Boot .. toctree:: :maxdepth: 2 + clang tools