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70 lines
2.9 KiB
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70 lines
2.9 KiB
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===================================================================
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How To Build On ARM
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===================================================================
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Introduction
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============
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This document contains information about building/testing LLVM and
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Clang on an ARM machine.
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This document is *NOT* tailored to help you cross-compile LLVM/Clang
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to ARM on another architecture, for example an x86_64 machine. To find
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out more about cross-compiling, please check :doc:`HowToCrossCompileLLVM`.
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Notes On Building LLVM/Clang on ARM
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=====================================
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Here are some notes on building/testing LLVM/Clang on ARM. Note that
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ARM encompasses a wide variety of CPUs; this advice is primarily based
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on the ARMv6 and ARMv7 architectures and may be inapplicable to older chips.
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#. If you are building LLVM/Clang on an ARM board with 1G of memory or less,
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please use ``gold`` rather then GNU ``ld``.
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Building LLVM/Clang with ``--enable-optimized``
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is preferred since it consumes less memory. Otherwise, the building
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process will very likely fail due to insufficient memory. In any
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case it is probably a good idea to set up a swap partition.
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#. If you want to run ``make check-all`` after building LLVM/Clang, to avoid
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false alarms (e.g., ARCMT failure) please use at least the following
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configuration:
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.. code-block:: bash
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$ ../$LLVM_SRC_DIR/configure --with-abi=aapcs-vfp
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#. The most popular Linaro/Ubuntu OS's for ARM boards, e.g., the
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Pandaboard, have become hard-float platforms. The following set
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of configuration options appears to be a good choice for this
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platform:
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.. code-block:: bash
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../$LLVM_SRC_DIR/configure --build=armv7l-unknown-linux-gnueabihf \
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--host=armv7l-unknown-linux-gnueabihf \
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--target=armv7l-unknown-linux-gnueabihf --with-cpu=cortex-a9 \
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--with-float=hard --with-abi=aapcs-vfp --with-fpu=neon \
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--enable-targets=arm --enable-optimized --enable-assertions
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#. ARM development boards can be unstable and you may experience that cores
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are disappearing, caches being flushed on every big.LITTLE switch, and
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other similar issues. To help ease the effect of this, set the Linux
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scheduler to "performance" on **all** cores using this little script:
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.. code-block:: bash
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# The code below requires the package 'cpufrequtils' to be installed.
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for ((cpu=0; cpu<`grep -c proc /proc/cpuinfo`; cpu++)); do
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sudo cpufreq-set -c $cpu -g performance
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done
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#. Running the build on SD cards is ok, but they are more prone to failures
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than good quality USB sticks, and those are more prone to failures than
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external hard-drives (those are also a lot faster). So, at least, you
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should consider to buy a fast USB stick. On systems with a fast eMMC,
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that's a good option too.
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#. Make sure you have a decent power supply (dozens of dollars worth) that can
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provide *at least* 4 amperes, this is especially important if you use USB
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devices with your board.
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