diff options
Diffstat (limited to 'tools/llvmc/doc/LLVMC-Reference.rst')
| -rw-r--r-- | tools/llvmc/doc/LLVMC-Reference.rst | 747 |
1 files changed, 0 insertions, 747 deletions
diff --git a/tools/llvmc/doc/LLVMC-Reference.rst b/tools/llvmc/doc/LLVMC-Reference.rst deleted file mode 100644 index 041aedf9e1..0000000000 --- a/tools/llvmc/doc/LLVMC-Reference.rst +++ /dev/null @@ -1,747 +0,0 @@ -=================================== -Customizing LLVMC: Reference Manual -=================================== -.. - This file was automatically generated by rst2html. - Please do not edit directly! - The ReST source lives in the directory 'tools/llvmc/doc'. - -.. contents:: - -.. raw:: html - - <div class="doc_author"> - <p>Written by <a href="mailto:foldr@codedgers.com">Mikhail Glushenkov</a></p> - </div> - -Introduction -============ - -LLVMC is a generic compiler driver, designed to be customizable and -extensible. It plays the same role for LLVM as the ``gcc`` program does for -GCC - LLVMC's job is essentially to transform a set of input files into a set of -targets depending on configuration rules and user options. What makes LLVMC -different is that these transformation rules are completely customizable - in -fact, LLVMC knows nothing about the specifics of transformation (even the -command-line options are mostly not hard-coded) and regards the transformation -structure as an abstract graph. The structure of this graph is described in -high-level TableGen code, from which an efficient C++ representation is -automatically derived. This makes it possible to adapt LLVMC for other -purposes - for example, as a build tool for game resources. - -Because LLVMC employs TableGen_ as its configuration language, you -need to be familiar with it to customize LLVMC. - -.. _TableGen: http://llvm.org/docs/TableGenFundamentals.html - - -Compiling with ``llvmc`` -======================== - -LLVMC tries hard to be as compatible with ``gcc`` as possible, -although there are some small differences. Most of the time, however, -you shouldn't be able to notice them:: - - $ # This works as expected: - $ llvmc -O3 -Wall hello.cpp - $ ./a.out - hello - -One nice feature of LLVMC is that one doesn't have to distinguish between -different compilers for different languages (think ``g++`` vs. ``gcc``) - the -right toolchain is chosen automatically based on input language names (which -are, in turn, determined from file extensions). If you want to force files -ending with ".c" to compile as C++, use the ``-x`` option, just like you would -do it with ``gcc``:: - - $ # hello.c is really a C++ file - $ llvmc -x c++ hello.c - $ ./a.out - hello - -On the other hand, when using LLVMC as a linker to combine several C++ -object files you should provide the ``--linker`` option since it's -impossible for LLVMC to choose the right linker in that case:: - - $ llvmc -c hello.cpp - $ llvmc hello.o - [A lot of link-time errors skipped] - $ llvmc --linker=c++ hello.o - $ ./a.out - hello - -By default, LLVMC uses ``llvm-gcc`` to compile the source code. It is also -possible to choose the ``clang`` compiler with the ``-clang`` option. - - -Predefined options -================== - -LLVMC has some built-in options that can't be overridden in the TableGen code: - -* ``-o FILE`` - Output file name. - -* ``-x LANGUAGE`` - Specify the language of the following input files - until the next -x option. - -* ``-v`` - Enable verbose mode, i.e. print out all executed commands. - -* ``--save-temps`` - Write temporary files to the current directory and do not - delete them on exit. This option can also take an argument: the - ``--save-temps=obj`` switch will write files into the directory specified with - the ``-o`` option. The ``--save-temps=cwd`` and ``--save-temps`` switches are - both synonyms for the default behaviour. - -* ``--temp-dir DIRECTORY`` - Store temporary files in the given directory. This - directory is deleted on exit unless ``--save-temps`` is specified. If - ``--save-temps=obj`` is also specified, ``--temp-dir`` is given the - precedence. - -* ``--check-graph`` - Check the compilation for common errors like mismatched - output/input language names, multiple default edges and cycles. Exit with code - zero if no errors were found, and return the number of found errors - otherwise. Hidden option, useful for debugging. - -* ``--view-graph`` - Show a graphical representation of the compilation graph - and exit. Requires that you have ``dot`` and ``gv`` programs installed. Hidden - option, useful for debugging. - -* ``--write-graph`` - Write a ``compilation-graph.dot`` file in the current - directory with the compilation graph description in Graphviz format (identical - to the file used by the ``--view-graph`` option). The ``-o`` option can be - used to set the output file name. Hidden option, useful for debugging. - -* ``--help``, ``--help-hidden``, ``--version`` - These options have - their standard meaning. - -Compiling LLVMC-based drivers -============================= - -It's easiest to start working on your own LLVMC driver by copying the skeleton -project which lives under ``$LLVMC_DIR/examples/Skeleton``:: - - $ cd $LLVMC_DIR/examples - $ cp -r Skeleton MyDriver - $ cd MyDriver - $ ls - AutoGenerated.td Hooks.cpp Main.cpp Makefile - -As you can see, our basic driver consists of only three files (not counting the -build script). ``AutoGenerated.td`` contains TableGen description of the -compilation graph; its format is documented in the following -sections. ``Hooks.cpp`` is an empty file that should be used for hook -definitions (see `below`__). ``Main.cpp`` is just a helper used to compile the -auto-generated C++ code produced from TableGen source. - -__ hooks_ - -The first thing that you should do is to change the ``LLVMC_BASED_DRIVER`` -variable in the ``Makefile``:: - - LLVMC_BASED_DRIVER=MyDriver - -It can also be a good idea to put your TableGen code into a file with a less -generic name:: - - $ touch MyDriver.td - $ vim AutoGenerated.td - [...] - include "MyDriver.td" - -If you have more than one TableGen source file, they all should be included from -``AutoGenerated.td``, since this file is used by the build system to generate -C++ code. - -To build your driver, just ``cd`` to its source directory and run ``make``. The -resulting executable will be put into ``$LLVM_OBJ_DIR/$(BuildMode)/bin``. - -If you're compiling LLVM with different source and object directories, then you -must perform the following additional steps before running ``make``:: - - # LLVMC_SRC_DIR = $LLVM_SRC_DIR/tools/llvmc/ - # LLVMC_OBJ_DIR = $LLVM_OBJ_DIR/tools/llvmc/ - $ mkdir $LLVMC_OBJ_DIR/examples/MyDriver/ - $ cp $LLVMC_SRC_DIR/examples/MyDriver/Makefile \ - $LLVMC_OBJ_DIR/examples/MyDriver/ - $ cd $LLVMC_OBJ_DIR/examples/MyDriver - $ make - - -Customizing LLVMC: the compilation graph -======================================== - -Each TableGen configuration file should include the common definitions:: - - include "llvm/CompilerDriver/Common.td" - -Internally, LLVMC stores information about possible source transformations in -form of a graph. Nodes in this graph represent tools, and edges between two -nodes represent a transformation path. A special "root" node is used to mark -entry points for the transformations. LLVMC also assigns a weight to each edge -(more on this later) to choose between several alternative edges. - -The definition of the compilation graph (see file ``llvmc/src/Base.td`` for an -example) is just a list of edges:: - - def CompilationGraph : CompilationGraph<[ - Edge<"root", "llvm_gcc_c">, - Edge<"root", "llvm_gcc_assembler">, - ... - - Edge<"llvm_gcc_c", "llc">, - Edge<"llvm_gcc_cpp", "llc">, - ... - - OptionalEdge<"llvm_gcc_c", "opt", (case (switch_on "opt"), - (inc_weight))>, - OptionalEdge<"llvm_gcc_cpp", "opt", (case (switch_on "opt"), - (inc_weight))>, - ... - - OptionalEdge<"llvm_gcc_assembler", "llvm_gcc_cpp_linker", - (case (input_languages_contain "c++"), (inc_weight), - (or (parameter_equals "linker", "g++"), - (parameter_equals "linker", "c++")), (inc_weight))>, - ... - - ]>; - -As you can see, the edges can be either default or optional, where optional -edges are differentiated by an additional ``case`` expression used to calculate -the weight of this edge. Notice also that we refer to tools via their names (as -strings). This makes it possible to add edges to an existing compilation graph -without having to know about all tool definitions used in the graph. - -The default edges are assigned a weight of 1, and optional edges get a weight of -0 + 2*N where N is the number of tests that evaluated to true in the ``case`` -expression. It is also possible to provide an integer parameter to -``inc_weight`` and ``dec_weight`` - in this case, the weight is increased (or -decreased) by the provided value instead of the default 2. Default weight of an -optional edge can be changed by using the ``default`` clause of the ``case`` -construct. - -When passing an input file through the graph, LLVMC picks the edge with the -maximum weight. To avoid ambiguity, there should be only one default edge -between two nodes (with the exception of the root node, which gets a special -treatment - there you are allowed to specify one default edge *per language*). - -When multiple compilation graphs are defined, they are merged together. Multiple -edges with the same end nodes are not allowed (i.e. the graph is not a -multigraph), and will lead to a compile-time error. - -To get a visual representation of the compilation graph (useful for debugging), -run ``llvmc --view-graph``. You will need ``dot`` and ``gsview`` installed for -this to work properly. - -Describing options -================== - -Command-line options supported by the driver are defined by using an -``OptionList``:: - - def Options : OptionList<[ - (switch_option "E", (help "Help string")), - (alias_option "quiet", "q") - ... - ]>; - -As you can see, the option list is just a list of DAGs, where each DAG is an -option description consisting of the option name and some properties. More than -one option list can be defined (they are all merged together in the end), which -can be handy if one wants to separate option groups syntactically. - -* Possible option types: - - - ``switch_option`` - a simple boolean switch without arguments, for example - ``-O2`` or ``-time``. At most one occurrence is allowed by default. - - - ``parameter_option`` - option that takes one argument, for example - ``-std=c99``. It is also allowed to use spaces instead of the equality - sign: ``-std c99``. At most one occurrence is allowed. - - - ``parameter_list_option`` - same as the above, but more than one option - occurrence is allowed. - - - ``prefix_option`` - same as the parameter_option, but the option name and - argument do not have to be separated. Example: ``-ofile``. This can be also - specified as ``-o file``; however, ``-o=file`` will be parsed incorrectly - (``=file`` will be interpreted as option value). At most one occurrence is - allowed. - - - ``prefix_list_option`` - same as the above, but more than one occurrence of - the option is allowed; example: ``-lm -lpthread``. - - - ``alias_option`` - a special option type for creating aliases. Unlike other - option types, aliases are not allowed to have any properties besides the - aliased option name. - Usage example: ``(alias_option "preprocess", "E")`` - - - ``switch_list_option`` - like ``switch_option`` with the ``zero_or_more`` - property, but remembers how many times the switch was turned on. Useful - mostly for forwarding. Example: when ``-foo`` is a switch option (with the - ``zero_or_more`` property), the command ``driver -foo -foo`` is forwarded - as ``some-tool -foo``, but when ``-foo`` is a switch list, the same command - is forwarded as ``some-tool -foo -foo``. - - -* Possible option properties: - - - ``help`` - help string associated with this option. Used for ``--help`` - output. - - - ``required`` - this option must be specified exactly once (or, in case of - the list options without the ``multi_val`` property, at least - once). Incompatible with ``optional`` and ``one_or_more``. - - - ``optional`` - the option can be specified either zero times or exactly - once. The default for switch options. Useful only for list options in - conjunction with ``multi_val``. Incompatible with ``required``, - ``zero_or_more`` and ``one_or_more``. - - - ``one_or_more`` - the option must be specified at least once. Can be useful - to allow switch options be both obligatory and be specified multiple - times. For list options is useful only in conjunction with ``multi_val``; - for ordinary it is synonymous with ``required``. Incompatible with - ``required``, ``optional`` and ``zero_or_more``. - - - ``zero_or_more`` - the option can be specified zero or more times. Useful - to allow a single switch option to be specified more than - once. Incompatible with ``required``, ``optional`` and ``one_or_more``. - - - ``hidden`` - the description of this option will not appear in - the ``--help`` output (but will appear in the ``--help-hidden`` - output). - - - ``really_hidden`` - the option will not be mentioned in any help - output. - - - ``comma_separated`` - Indicates that any commas specified for an option's - value should be used to split the value up into multiple values for the - option. This property is valid only for list options. In conjunction with - ``forward_value`` can be used to implement option forwarding in style of - gcc's ``-Wa,``. - - - ``multi_val n`` - this option takes *n* arguments (can be useful in some - special cases). Usage example: ``(parameter_list_option "foo", (multi_val - 3))``; the command-line syntax is '-foo a b c'. Only list options can have - this attribute; you can, however, use the ``one_or_more``, ``optional`` - and ``required`` properties. - - - ``init`` - this option has a default value, either a string (if it is a - parameter), or a boolean (if it is a switch; as in C++, boolean constants - are called ``true`` and ``false``). List options can't have ``init`` - attribute. - Usage examples: ``(switch_option "foo", (init true))``; ``(prefix_option - "bar", (init "baz"))``. - -.. _case: - -Conditional evaluation -====================== - -The 'case' construct is the main means by which programmability is achieved in -LLVMC. It can be used to calculate edge weights, program actions and modify the -shell commands to be executed. The 'case' expression is designed after the -similarly-named construct in functional languages and takes the form ``(case -(test_1), statement_1, (test_2), statement_2, ... (test_N), statement_N)``. The -statements are evaluated only if the corresponding tests evaluate to true. - -Examples:: - - // Edge weight calculation - - // Increases edge weight by 5 if "-A" is provided on the - // command-line, and by 5 more if "-B" is also provided. - (case - (switch_on "A"), (inc_weight 5), - (switch_on "B"), (inc_weight 5)) - - - // Tool command line specification - - // Evaluates to "cmdline1" if the option "-A" is provided on the - // command line; to "cmdline2" if "-B" is provided; - // otherwise to "cmdline3". - - (case - (switch_on "A"), "cmdline1", - (switch_on "B"), "cmdline2", - (default), "cmdline3") - -Note the slight difference in 'case' expression handling in contexts of edge -weights and command line specification - in the second example the value of the -``"B"`` switch is never checked when switch ``"A"`` is enabled, and the whole -expression always evaluates to ``"cmdline1"`` in that case. - -Case expressions can also be nested, i.e. the following is legal:: - - (case (switch_on "E"), (case (switch_on "o"), ..., (default), ...) - (default), ...) - -You should, however, try to avoid doing that because it hurts readability. It is -usually better to split tool descriptions and/or use TableGen inheritance -instead. - -* Possible tests are: - - - ``switch_on`` - Returns true if a given command-line switch is provided by - the user. Can be given multiple arguments, in that case ``(switch_on "foo", - "bar", "baz")`` is equivalent to ``(and (switch_on "foo"), (switch_on - "bar"), (switch_on "baz"))``. - Example: ``(switch_on "opt")``. - - - ``any_switch_on`` - Given a number of switch options, returns true if any of - the switches is turned on. - Example: ``(any_switch_on "foo", "bar", "baz")`` is equivalent to ``(or - (switch_on "foo"), (switch_on "bar"), (switch_on "baz"))``. - - - ``parameter_equals`` - Returns true if a command-line parameter (first - argument) equals a given value (second argument). - Example: ``(parameter_equals "W", "all")``. - - - ``element_in_list`` - Returns true if a command-line parameter list (first - argument) contains a given value (second argument). - Example: ``(element_in_list "l", "pthread")``. - - - ``input_languages_contain`` - Returns true if a given language - belongs to the current input language set. - Example: ``(input_languages_contain "c++")``. - - - ``in_language`` - Evaluates to true if the input file language is equal to - the argument. At the moment works only with ``command`` and ``actions`` (on - non-join nodes). - Example: ``(in_language "c++")``. - - - ``not_empty`` - Returns true if a given option (which should be either a - parameter or a parameter list) is set by the user. Like ``switch_on``, can - be also given multiple arguments. - Examples: ``(not_empty "o")``, ``(not_empty "o", "l")``. - - - ``any_not_empty`` - Returns true if ``not_empty`` returns true for any of - the provided options. - Example: ``(any_not_empty "foo", "bar", "baz")`` is equivalent to ``(or - (not_empty "foo"), (not_empty "bar"), (not_empty "baz"))``. - - - ``empty`` - The opposite of ``not_empty``. Equivalent to ``(not (not_empty - X))``. Can be given multiple arguments. - - - ``any_not_empty`` - Returns true if ``not_empty`` returns true for any of - the provided options. - Example: ``(any_empty "foo", "bar", "baz")`` is equivalent to ``(or - (not_empty "foo"), (not_empty "bar"), (not_empty "baz"))``. - - - ``single_input_file`` - Returns true if there was only one input file - provided on the command-line. Used without arguments: - ``(single_input_file)``. - - - ``multiple_input_files`` - Equivalent to ``(not (single_input_file))`` (the - case of zero input files is considered an error). - - - ``default`` - Always evaluates to true. Should always be the last - test in the ``case`` expression. - - - ``and`` - A standard logical combinator that returns true iff all of - its arguments return true. Used like this: ``(and (test1), (test2), - ... (testN))``. Nesting of ``and`` and ``or`` is allowed, but not - encouraged. - - - ``or`` - A logical combinator that returns true iff any of its arguments - return true. - Example: ``(or (test1), (test2), ... (testN))``. - - - ``not`` - Standard unary logical combinator that negates its - argument. - Example: ``(not (or (test1), (test2), ... (testN)))``. - - -Writing a tool description -========================== - -As was said earlier, nodes in the compilation graph represent tools, which are -described separately. A tool definition looks like this (taken from the -``llvmc/src/Base.td`` file):: - - def llvm_gcc_cpp : Tool<[ - (in_language "c++"), - (out_language "llvm-assembler"), - (output_suffix "bc"), - (command "llvm-g++ -c -emit-llvm"), - (sink) - ]>; - -This defines a new tool called ``llvm_gcc_cpp``, which is an alias for -``llvm-g++``. As you can see, a tool definition is just a list of properties; -most of them should be self-explanatory. The ``sink`` property means that this -tool should be passed all command-line options that aren't mentioned in the -option list. - -The complete list of all currently implemented tool properties follows. - -* Possible tool properties: - - - ``in_language`` - input language name. Can be given multiple arguments, in - case the tool supports multiple input languages. Used for typechecking and - mapping file extensions to tools. - - - ``out_language`` - output language name. Multiple output languages are - allowed. Used for typechecking the compilation graph. - - - ``output_suffix`` - output file suffix. Can also be changed dynamically, see - documentation on `actions`__. - -__ actions_ - - - ``command`` - the actual command used to run the tool. You can use output - redirection with ``>``, hook invocations (``$CALL``), environment variables - (via ``$ENV``) and the ``case`` construct. - - - ``join`` - this tool is a "join node" in the graph, i.e. it gets a list of - input files and joins them together. Used for linkers. - - - ``sink`` - all command-line options that are not handled by other tools are - passed to this tool. - - - ``actions`` - A single big ``case`` expression that specifies how this tool - reacts on command-line options (described in more detail `below`__). - -__ actions_ - - - ``out_file_option``, ``in_file_option`` - Options appended to the - ``command`` string to designate output and input files. Default values are - ``"-o"`` and ``""``, respectively. - -.. _actions: - -Actions -------- - -A tool often needs to react to command-line options, and this is precisely what -the ``actions`` property is for. The next example illustrates this feature:: - - def llvm_gcc_linker : Tool<[ - (in_language "object-code"), - (out_language "executable"), - (output_suffix "out"), - (command "llvm-gcc"), - (join), - (actions (case (not_empty "L"), (forward "L"), - (not_empty "l"), (forward "l"), - (not_empty "dummy"), - [(append_cmd "-dummy1"), (append_cmd "-dummy2")]) - ]>; - -The ``actions`` tool property is implemented on top of the omnipresent ``case`` -expression. It associates one or more different *actions* with given -conditions - in the example, the actions are ``forward``, which forwards a given -option unchanged, and ``append_cmd``, which appends a given string to the tool -execution command. Multiple actions can be associated with a single condition by -using a list of actions (used in the example to append some dummy options). The -same ``case`` construct can also be used in the ``cmd_line`` property to modify -the tool command line. - -The "join" property used in the example means that this tool behaves like a -linker. - -The list of all possible actions follows. - -* Possible actions: - - - ``append_cmd`` - Append a string to the tool invocation command. - Example: ``(case (switch_on "pthread"), (append_cmd "-lpthread"))``. - - - ``error`` - Exit with error. - Example: ``(error "Mixing -c and -S is not allowed!")``. - - - ``warning`` - Print a warning. - Example: ``(warning "Specifying both -O1 and -O2 is meaningless!")``. - - - ``forward`` - Forward the option unchanged. - Example: ``(forward "Wall")``. - - - ``forward_as`` - Change the option's name, but forward the argument - unchanged. - Example: ``(forward_as "O0", "--disable-optimization")``. - - - ``forward_value`` - Forward only option's value. Cannot be used with switch - options (since they don't have values), but works fine with lists. - Example: ``(forward_value "Wa,")``. - - - ``forward_transformed_value`` - As above, but applies a hook to the - option's value before forwarding (see `below`__). When - ``forward_transformed_value`` is applied to a list - option, the hook must have signature - ``std::string hooks::HookName (const std::vector<std::string>&)``. - Example: ``(forward_transformed_value "m", "ConvertToMAttr")``. - - __ hooks_ - - - ``output_suffix`` - Modify the output suffix of this tool. - Example: ``(output_suffix "i")``. - - - ``stop_compilation`` - Stop compilation after this tool processes its - input. Used without arguments. - Example: ``(stop_compilation)``. - - -Language map -============ - -If you are adding support for a new language to LLVMC, you'll need to modify the -language map, which defines mappings from file extensions to language names. It -is used to choose the proper toolchain(s) for a given input file set. Language -map definition looks like this:: - - def LanguageMap : LanguageMap< - [LangToSuffixes<"c++", ["cc", "cp", "cxx", "cpp", "CPP", "c++", "C"]>, - LangToSuffixes<"c", ["c"]>, - ... - ]>; - -For example, without those definitions the following command wouldn't work:: - - $ llvmc hello.cpp - llvmc: Unknown suffix: cpp - -The language map entries are needed only for the tools that are linked from the -root node. A tool can have multiple output languages. - -Option preprocessor -=================== - -It is sometimes useful to run error-checking code before processing the -compilation graph. For example, if optimization options "-O1" and "-O2" are -implemented as switches, we might want to output a warning if the user invokes -the driver with both of these options enabled. - -The ``OptionPreprocessor`` feature is reserved specially for these -occasions. Example (adapted from ``llvm/src/Base.td.in``):: - - - def Preprocess : OptionPreprocessor< - (case (not (any_switch_on "O0", "O1", "O2", "O3")), - (set_option "O2"), - (and (switch_on "O3"), (any_switch_on "O0", "O1", "O2")), - (unset_option "O0", "O1", "O2"), - (and (switch_on "O2"), (any_switch_on "O0", "O1")), - (unset_option "O0", "O1"), - (and (switch_on "O1"), (switch_on "O0")), - (unset_option "O0")) - >; - -Here, ``OptionPreprocessor`` is used to unset all spurious ``-O`` options so -that they are not forwarded to the compiler. If no optimization options are -specified, ``-O2`` is enabled. - -``OptionPreprocessor`` is basically a single big ``case`` expression, which is -evaluated only once right after the driver is started. The only allowed actions -in ``OptionPreprocessor`` are ``error``, ``warning``, and two special actions: -``unset_option`` and ``set_option``. As their names suggest, they can be used to -set or unset a given option. To set an option with ``set_option``, use the -two-argument form: ``(set_option "parameter", VALUE)``. Here, ``VALUE`` can be -either a string, a string list, or a boolean constant. - -For convenience, ``set_option`` and ``unset_option`` also work with multiple -arguments. That is, instead of ``[(unset_option "A"), (unset_option "B")]`` you -can use ``(unset_option "A", "B")``. Obviously, ``(set_option "A", "B")`` is -only valid if both ``A`` and ``B`` are switches. - - -More advanced topics -==================== - -.. _hooks: - -Hooks and environment variables -------------------------------- - -Normally, LLVMC searches for programs in the system ``PATH``. Sometimes, this is -not sufficient: for example, we may want to specify tool paths or names in the -configuration file. This can be achieved via the hooks mechanism. To write your -own hooks, add their definitions to the ``Hooks.cpp`` or drop a ``.cpp`` file -into your driver directory. Hooks should live in the ``hooks`` namespace and -have the signature ``std::string hooks::MyHookName ([const char* Arg0 [ const -char* Arg2 [, ...]]])``. They can be used from the ``command`` tool property:: - - (command "$CALL(MyHook)/path/to/file -o $CALL(AnotherHook)") - -To pass arguments to hooks, use the following syntax:: - - (command "$CALL(MyHook, 'Arg1', 'Arg2', 'Arg # 3')/path/to/file -o1 -o2") - -It is also possible to use environment variables in the same manner:: - - (command "$ENV(VAR1)/path/to/file -o $ENV(VAR2)") - -To change the command line string based on user-provided options use -the ``case`` expression (documented `above`__):: - - (command - (case - (switch_on "E"), - "llvm-g++ -E -x c $INFILE -o $OUTFILE", - (default), - "llvm-g++ -c -x c $INFILE -o $OUTFILE -emit-llvm")) - -__ case_ - -Debugging ---------- - -When writing LLVMC-based drivers, it can be useful to get a visual view of the -resulting compilation graph. This can be achieved via the command line option -``--view-graph`` (which assumes that Graphviz_ and Ghostview_ are -installed). There is also a ``--write-graph`` option that creates a Graphviz -source file (``compilation-graph.dot``) in the current directory. - -Another useful ``llvmc`` option is ``--check-graph``. It checks the compilation -graph for common errors like mismatched output/input language names, multiple -default edges and cycles. When invoked with ``--check-graph``, ``llvmc`` doesn't -perform any compilation tasks and returns the number of encountered errors as -its status code. In the future, these checks will be performed at compile-time -and this option will disappear. - -.. _Graphviz: http://www.graphviz.org/ -.. _Ghostview: http://pages.cs.wisc.edu/~ghost/ - -Conditioning on the executable name ------------------------------------ - -For now, the executable name (the value passed to the driver in ``argv[0]``) is -accessible only in the C++ code (i.e. hooks). Use the following code:: - - namespace llvmc { - extern const char* ProgramName; - } - - namespace hooks { - - std::string MyHook() { - //... - if (strcmp(ProgramName, "mydriver") == 0) { - //... - - } - - } // end namespace hooks - -In general, you're encouraged not to make the behaviour dependent on the -executable file name, and use command-line switches instead. See for example how -the ``llvmc`` program behaves when it needs to choose the correct linker options -(think ``g++`` vs. ``gcc``). - -.. raw:: html - - <hr /> - <address> - <a href="http://jigsaw.w3.org/css-validator/check/referer"> - <img src="http://jigsaw.w3.org/css-validator/images/vcss-blue" - alt="Valid CSS" /></a> - <a href="http://validator.w3.org/check?uri=referer"> - <img src="http://www.w3.org/Icons/valid-xhtml10-blue" - alt="Valid XHTML 1.0 Transitional"/></a> - - <a href="mailto:foldr@codedgers.com">Mikhail Glushenkov</a><br /> - <a href="http://llvm.org">LLVM Compiler Infrastructure</a><br /> - - Last modified: $Date: 2008-12-11 11:34:48 -0600 (Thu, 11 Dec 2008) $ - </address> |