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1 ========================
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2 Advice on Packaging LLVM
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3 ========================
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4
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5 .. contents::
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6 :local:
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7
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8 Overview
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9 ========
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10
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11 LLVM sets certain default configure options to make sure our developers don't
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12 break things for constrained platforms. These settings are not optimal for most
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13 desktop systems, and we hope that packagers (e.g., Redhat, Debian, MacPorts,
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14 etc.) will tweak them. This document lists settings we suggest you tweak.
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15
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16 LLVM's API changes with each release, so users are likely to want, for example,
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17 both LLVM-2.6 and LLVM-2.7 installed at the same time to support apps developed
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18 against each.
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19
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20 Compile Flags
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21 =============
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22
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23 LLVM runs much more quickly when it's optimized and assertions are removed.
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24 However, such a build is currently incompatible with users who build without
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25 defining ``NDEBUG``, and the lack of assertions makes it hard to debug problems
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26 in user code. We recommend allowing users to install both optimized and debug
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27 versions of LLVM in parallel. The following configure flags are relevant:
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28
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29 ``--disable-assertions``
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30 Builds LLVM with ``NDEBUG`` defined. Changes the LLVM ABI. Also available
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31 by setting ``DISABLE_ASSERTIONS=0|1`` in ``make``'s environment. This
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32 defaults to enabled regardless of the optimization setting, but it slows
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33 things down.
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34
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35 ``--enable-debug-symbols``
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36 Builds LLVM with ``-g``. Also available by setting ``DEBUG_SYMBOLS=0|1`` in
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37 ``make``'s environment. This defaults to disabled when optimizing, so you
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38 should turn it back on to let users debug their programs.
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39
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40 ``--enable-optimized``
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41 (For git checkouts) Builds LLVM with ``-O2`` and, by default, turns off
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42 debug symbols. Also available by setting ``ENABLE_OPTIMIZED=0|1`` in
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43 ``make``'s environment. This defaults to enabled when not in a
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44 checkout.
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45
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46 C++ Features
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47 ============
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48
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49 RTTI
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50 LLVM disables RTTI by default. Add ``REQUIRES_RTTI=1`` to your environment
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51 while running ``make`` to re-enable it. This will allow users to build with
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52 RTTI enabled and still inherit from LLVM classes.
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53
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54 Shared Library
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55 ==============
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56
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57 Configure with ``--enable-shared`` to build
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58 ``libLLVM-<major>.<minor>.(so|dylib)`` and link the tools against it. This
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59 saves lots of binary size at the cost of some startup time.
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60
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61 Dependencies
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62 ============
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63
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64 ``--enable-libffi``
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65 Depend on `libffi <http://sources.redhat.com/libffi/>`_ to allow the LLVM
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66 interpreter to call external functions.
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67
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68 ``--with-oprofile``
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69
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70 Depend on `libopagent
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71 <http://oprofile.sourceforge.net/doc/devel/index.html>`_ (>=version 0.9.4)
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72 to let the LLVM JIT tell oprofile about function addresses and line
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73 numbers.
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