2012-06-21 14:09:37 +08:00
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Advice on Packaging LLVM
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========================
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.. contents::
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:local:
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Overview
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========
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LLVM sets certain default configure options to make sure our developers don't
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break things for constrained platforms. These settings are not optimal for most
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desktop systems, and we hope that packagers (e.g., Redhat, Debian, MacPorts,
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etc.) will tweak them. This document lists settings we suggest you tweak.
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LLVM's API changes with each release, so users are likely to want, for example,
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both LLVM-2.6 and LLVM-2.7 installed at the same time to support apps developed
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against each.
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Compile Flags
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=============
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LLVM runs much more quickly when it's optimized and assertions are removed.
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However, such a build is currently incompatible with users who build without
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defining ``NDEBUG``, and the lack of assertions makes it hard to debug problems
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in user code. We recommend allowing users to install both optimized and debug
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versions of LLVM in parallel. The following configure flags are relevant:
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``--disable-assertions``
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Builds LLVM with ``NDEBUG`` defined. Changes the LLVM ABI. Also available
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by setting ``DISABLE_ASSERTIONS=0|1`` in ``make``'s environment. This
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defaults to enabled regardless of the optimization setting, but it slows
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things down.
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``--enable-debug-symbols``
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Builds LLVM with ``-g``. Also available by setting ``DEBUG_SYMBOLS=0|1`` in
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``make``'s environment. This defaults to disabled when optimizing, so you
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should turn it back on to let users debug their programs.
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``--enable-optimized``
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2020-03-23 05:31:18 +08:00
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(For git checkouts) Builds LLVM with ``-O2`` and, by default, turns off
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2012-06-21 14:09:37 +08:00
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debug symbols. Also available by setting ``ENABLE_OPTIMIZED=0|1`` in
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``make``'s environment. This defaults to enabled when not in a
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checkout.
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C++ Features
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============
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RTTI
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LLVM disables RTTI by default. Add ``REQUIRES_RTTI=1`` to your environment
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while running ``make`` to re-enable it. This will allow users to build with
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RTTI enabled and still inherit from LLVM classes.
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Shared Library
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==============
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Configure with ``--enable-shared`` to build
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``libLLVM-<major>.<minor>.(so|dylib)`` and link the tools against it. This
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saves lots of binary size at the cost of some startup time.
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Dependencies
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============
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``--enable-libffi``
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Depend on `libffi <http://sources.redhat.com/libffi/>`_ to allow the LLVM
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interpreter to call external functions.
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``--with-oprofile``
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Depend on `libopagent
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<http://oprofile.sourceforge.net/doc/devel/index.html>`_ (>=version 0.9.4)
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to let the LLVM JIT tell oprofile about function addresses and line
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numbers.
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