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Documentation update.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51753 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Mikhail Glushenkov
parent
5fe8475e3a
commit
270cae3bf8
@ -1,3 +1,4 @@
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===================================
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Customizing LLVMC: Reference Manual
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===================================
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@ -15,8 +16,12 @@ purposes - for example, as a build tool for game resources.
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Because LLVMC employs TableGen [1]_ as its configuration language, you
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need to be familiar with it to customize LLVMC.
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.. contents::
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Compiling with LLVMC
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--------------------
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====================
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LLVMC tries hard to be as compatible with ``gcc`` as possible,
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although there are some small differences. Most of the time, however,
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@ -50,9 +55,30 @@ impossible for LLVMC to choose the right linker in that case::
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$ ./a.out
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hello
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Predefined options
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==================
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LLVMC has some built-in options that can't be overridden in the
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configuration files:
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* ``-o FILE`` - Output file name.
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* ``-x LANGUAGE`` - Specify the language of the following input files
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until the next -x option.
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* ``-v`` - Enable verbose mode, i.e. print out all executed commands.
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* ``--view-graph`` - Show a graphical representation of the compilation
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graph. Requires that you have ``dot`` and ``gv`` commands
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installed. Hidden option, useful for debugging.
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* ``--write-graph`` - Write a ``compilation-graph.dot`` file in the
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current directory with the compilation graph description in the
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Graphviz format. Hidden option, useful for debugging.
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Customizing LLVMC: the compilation graph
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----------------------------------------
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========================================
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At the time of writing LLVMC does not support on-the-fly reloading of
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configuration, so to customize LLVMC you'll have to recompile the
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@ -125,65 +151,8 @@ debugging), run ``llvmc2 --view-graph``. You will need ``dot`` and
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``gsview`` installed for this to work properly.
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The 'case' expression
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---------------------
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The 'case' construct can be used to calculate weights of the optional
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edges and to choose between several alternative command line strings
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in the ``cmd_line`` tool property. It is designed after the
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similarly-named construct in functional languages and takes the form
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``(case (test_1), statement_1, (test_2), statement_2, ... (test_N),
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statement_N)``. The statements are evaluated only if the corresponding
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tests evaluate to true.
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Examples::
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// Increases edge weight by 5 if "-A" is provided on the
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// command-line, and by 5 more if "-B" is also provided.
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(case
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(switch_on "A"), (inc_weight 5),
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(switch_on "B"), (inc_weight 5))
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// Evaluates to "cmdline1" if option "-A" is provided on the
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// command line, otherwise to "cmdline2"
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(case
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(switch_on "A"), ("cmdline1"),
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(default), ("cmdline2"))
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* Possible tests are:
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- ``switch_on`` - Returns true if a given command-line option is
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provided by the user. Example: ``(switch_on "opt")``. Note that
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you have to define all possible command-line options separately in
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the tool descriptions. See the next section for the discussion of
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different kinds of command-line options.
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- ``parameter_equals`` - Returns true if a command-line parameter equals
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a given value. Example: ``(parameter_equals "W", "all")``.
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- ``element_in_list`` - Returns true if a command-line parameter list
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includes a given value. Example: ``(parameter_in_list "l", "pthread")``.
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- ``input_languages_contain`` - Returns true if a given language
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belongs to the current input language set. Example:
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```(input_languages_contain "c++")``.
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- ``default`` - Always evaluates to true. Should always be the last
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test in the ``case`` expression.
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- ``and`` - A standard logical combinator that returns true iff all
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of its arguments return true. Used like this: ``(and (test1),
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(test2), ... (testN))``. Nesting of ``and`` and ``or`` is allowed,
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but not encouraged.
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- ``or`` - Another logical combinator that returns true only if any
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one of its arguments returns true. Example: ``(or (test1),
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(test2), ... (testN))``.
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Writing a tool description
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--------------------------
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==========================
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As was said earlier, nodes in the compilation graph represent tools,
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which are described separately. A tool definition looks like this
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@ -285,8 +254,8 @@ currently implemented option types and properties are described below:
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- ``required`` - this option is obligatory.
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Hooks and environment variables
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-------------------------------
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Using hooks and environment variables in the ``cmd_line`` property
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==================================================================
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Normally, LLVMC executes programs from the system ``PATH``. Sometimes,
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this is not sufficient: for example, we may want to specify tool names
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@ -303,7 +272,7 @@ It is also possible to use environment variables in the same manner::
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(cmd_line "$ENV(VAR1)/path/to/file -o $ENV(VAR2)")
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To change the command line string based on user-provided options use
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the ``case`` expression (which we have already seen before)::
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the ``case`` expression (documented below)::
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(cmd_line
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(case
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@ -312,9 +281,89 @@ the ``case`` expression (which we have already seen before)::
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(default),
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"llvm-g++ -c -x c $INFILE -o $OUTFILE -emit-llvm"))
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Conditional evaluation: the ``case`` expression
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===============================================
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The 'case' construct can be used to calculate weights of the optional
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edges and to choose between several alternative command line strings
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in the ``cmd_line`` tool property. It is designed after the
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similarly-named construct in functional languages and takes the form
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``(case (test_1), statement_1, (test_2), statement_2, ... (test_N),
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statement_N)``. The statements are evaluated only if the corresponding
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tests evaluate to true.
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Examples::
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// Increases edge weight by 5 if "-A" is provided on the
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// command-line, and by 5 more if "-B" is also provided.
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(case
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(switch_on "A"), (inc_weight 5),
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(switch_on "B"), (inc_weight 5))
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// Evaluates to "cmdline1" if option "-A" is provided on the
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// command line, otherwise to "cmdline2"
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(case
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(switch_on "A"), "cmdline1",
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(switch_on "B"), "cmdline2",
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(default), "cmdline3")
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Note the slight difference in 'case' expression handling in contexts
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of edge weights and command line specification - in the second example
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the value of the ``"B"`` switch is never checked when switch ``"A"`` is
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enabled, and the whole expression always evaluates to ``"cmdline1"`` in
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that case.
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Case expressions can also be nested, i.e. the following is legal::
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(case (switch_on "E"), (case (switch_on "o"), ..., (default), ...)
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(default), ...)
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You should, however, try to avoid doing that because it hurts
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readability. It is usually better to split tool descriptions and/or
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use TableGen inheritance instead.
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* Possible tests are:
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- ``switch_on`` - Returns true if a given command-line option is
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provided by the user. Example: ``(switch_on "opt")``. Note that
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you have to define all possible command-line options separately in
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the tool descriptions. See the next section for the discussion of
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different kinds of command-line options.
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- ``parameter_equals`` - Returns true if a command-line parameter equals
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a given value. Example: ``(parameter_equals "W", "all")``.
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- ``element_in_list`` - Returns true if a command-line parameter list
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includes a given value. Example: ``(parameter_in_list "l", "pthread")``.
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- ``input_languages_contain`` - Returns true if a given language
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belongs to the current input language set. Example:
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```(input_languages_contain "c++")``.
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- ``in_language`` - Evaluates to true if the language of the input
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file equals to the argument. Valid only when using ``case``
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expression in a ``cmd_line`` tool property. Example:
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```(in_language "c++")``.
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- ``not_empty`` - Returns true if a given option (which should be
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either a parameter or a parameter list) is set by the
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user. Example: ```(not_empty "o")``.
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- ``default`` - Always evaluates to true. Should always be the last
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test in the ``case`` expression.
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- ``and`` - A standard logical combinator that returns true iff all
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of its arguments return true. Used like this: ``(and (test1),
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(test2), ... (testN))``. Nesting of ``and`` and ``or`` is allowed,
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but not encouraged.
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- ``or`` - Another logical combinator that returns true only if any
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one of its arguments returns true. Example: ``(or (test1),
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(test2), ... (testN))``.
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Language map
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------------
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============
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One last thing that you will need to modify when adding support for a
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new language to LLVMC is the language map, which defines mappings from
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@ -1,3 +1,4 @@
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======================
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Tutorial - Using LLVMC
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======================
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@ -6,8 +7,12 @@ as the ``gcc`` program does for GCC - the difference being that LLVMC
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is designed to be more adaptable and easier to customize. This
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tutorial describes the basic usage and configuration of LLVMC.
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.. contents::
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Compiling with LLVMC
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--------------------
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====================
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In general, LLVMC tries to be command-line compatible with ``gcc`` as
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much as possible, so most of the familiar options work::
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@ -20,7 +25,7 @@ For further help on command-line LLVMC usage, refer to the ``llvmc
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--help`` output.
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Using LLVMC to generate toolchain drivers
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-----------------------------------------
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=========================================
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At the time of writing LLVMC does not support on-the-fly reloading of
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configuration, so it will be necessary to recompile its source
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