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diff --git a/tools/llvmc/doc/LLVMC-Reference.rst b/tools/llvmc/doc/LLVMC-Reference.rst index ec9098b90cd5..041aedf9e16d 100644 --- a/tools/llvmc/doc/LLVMC-Reference.rst +++ b/tools/llvmc/doc/LLVMC-Reference.rst @@ -18,17 +18,16 @@ 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 completely determined -by plugins, which can be either statically or dynamically linked. This -makes it possible to easily adapt LLVMC for other purposes - for -example, as a build tool for game resources. +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. @@ -36,8 +35,8 @@ need to be familiar with it to customize LLVMC. .. _TableGen: http://llvm.org/docs/TableGenFundamentals.html -Compiling with LLVMC -==================== +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, @@ -78,17 +77,13 @@ 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 -configuration libraries: +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. -* ``-load PLUGIN_NAME`` - Load the specified plugin DLL. Example: - ``-load $LLVM_DIR/Release/lib/LLVMCSimple.so``. - * ``-v`` - Enable verbose mode, i.e. print out all executed commands. * ``--save-temps`` - Write temporary files to the current directory and do not @@ -103,124 +98,90 @@ configuration libraries: precedence. * ``--check-graph`` - Check the compilation for common errors like mismatched - output/input language names, multiple default edges and cycles. Because of - plugins, these checks can't be performed at compile-time. Exit with code zero - if no errors were found, and return the number of found errors - otherwise. Hidden option, useful for debugging LLVMC plugins. + output/input language names, multiple default edges and cycles. Exit with code + zero if no errors were found, and return the number of found errors + otherwise. Hidden option, useful for debugging. * ``--view-graph`` - Show a graphical representation of the compilation graph and exit. Requires that you have ``dot`` and ``gv`` programs installed. Hidden - option, useful for debugging LLVMC plugins. + option, useful for debugging. * ``--write-graph`` - Write a ``compilation-graph.dot`` file in the current directory with the compilation graph description in Graphviz format (identical to the file used by the ``--view-graph`` option). The ``-o`` option can be - used to set the output file name. Hidden option, useful for debugging LLVMC - plugins. + used to set the output file name. Hidden option, useful for debugging. * ``--help``, ``--help-hidden``, ``--version`` - These options have their standard meaning. -Compiling LLVMC plugins -======================= +Compiling LLVMC-based drivers +============================= -It's easiest to start working on your own LLVMC plugin by copying the -skeleton project which lives under ``$LLVMC_DIR/plugins/Simple``:: +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/plugins - $ cp -r Simple MyPlugin - $ cd MyPlugin + $ cd $LLVMC_DIR/examples + $ cp -r Skeleton MyDriver + $ cd MyDriver $ ls - Makefile PluginMain.cpp Simple.td + AutoGenerated.td Hooks.cpp Main.cpp Makefile -As you can see, our basic plugin consists of only two files (not -counting the build script). ``Simple.td`` contains TableGen -description of the compilation graph; its format is documented in the -following sections. ``PluginMain.cpp`` is just a helper file used to -compile the auto-generated C++ code produced from TableGen source. It -can also contain hook definitions (see `below`__). +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_PLUGIN`` -variable in the ``Makefile`` to avoid conflicts (since this variable -is used to name the resulting library):: - - LLVMC_PLUGIN=MyPlugin - -It is also a good idea to rename ``Simple.td`` to something less -generic:: +The first thing that you should do is to change the ``LLVMC_BASED_DRIVER`` +variable in the ``Makefile``:: - $ mv Simple.td MyPlugin.td + LLVMC_BASED_DRIVER=MyDriver -To build your plugin as a dynamic library, just ``cd`` to its source -directory and run ``make``. The resulting file will be called -``plugin_llvmc_$(LLVMC_PLUGIN).$(DLL_EXTENSION)`` (in our case, -``plugin_llvmc_MyPlugin.so``). This library can be then loaded in with the -``-load`` option. Example:: +It can also be a good idea to put your TableGen code into a file with a less +generic name:: - $ cd $LLVMC_DIR/plugins/Simple - $ make - $ llvmc -load $LLVM_DIR/Release/lib/plugin_llvmc_Simple.so + $ touch MyDriver.td + $ vim AutoGenerated.td + [...] + include "MyDriver.td" -Compiling standalone LLVMC-based drivers -======================================== +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. -By default, the ``llvmc`` executable consists of a driver core plus several -statically linked plugins (``Base`` and ``Clang`` at the moment). You can -produce a standalone LLVMC-based driver executable by linking the core with your -own plugins. The recommended way to do this is by starting with the provided -``Skeleton`` example (``$LLVMC_DIR/example/Skeleton``):: - - $ cd $LLVMC_DIR/example/ - $ cp -r Skeleton mydriver - $ cd mydriver - $ vim Makefile - [...] - $ make +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/ - $ cp $LLVMC_SRC_DIR/example/mydriver/Makefile \ - $LLVMC_OBJ_DIR/example/mydriver/ - $ cd $LLVMC_OBJ_DIR/example/mydriver + $ 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 -Another way to do the same thing is by using the following command:: - - $ cd $LLVMC_DIR - $ make LLVMC_BUILTIN_PLUGINS=MyPlugin LLVMC_BASED_DRIVER_NAME=mydriver - -This works with both srcdir == objdir and srcdir != objdir, but assumes that the -plugin source directory was placed under ``$LLVMC_DIR/plugins``. - -Sometimes, you will want a 'bare-bones' version of LLVMC that has no -built-in plugins. It can be compiled with the following command:: - - $ cd $LLVMC_DIR - $ make LLVMC_BUILTIN_PLUGINS="" - Customizing LLVMC: the compilation graph ======================================== -Each TableGen configuration file should include the common -definitions:: +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. +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 -``plugins/Base/Base.td`` for an example) is just a list of 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">, @@ -245,43 +206,37 @@ The definition of the compilation graph (see file ]>; -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 in plugins 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. It is also possible to change the default weight of -an optional edge by using the ``default`` clause of the ``case`` +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 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 plugins are loaded, their compilation graphs are merged -together. Since multiple edges that have the same end nodes are not -allowed (i.e. the graph is not a multigraph), an edge defined in -several plugins will be replaced by the definition from the plugin -that was loaded last. Plugin load order can be controlled by using the -plugin priority feature described above. +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. +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 that the plugin supports are defined by using an +Command-line options supported by the driver are defined by using an ``OptionList``:: def Options : OptionList<[ @@ -290,11 +245,10 @@ Command-line options that the plugin supports are defined by using an ... ]>; -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. A plugin can define more than one option list (they are -all merged together in the end), which can be handy if one wants to -separate option groups syntactically. +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: @@ -306,7 +260,7 @@ separate option groups syntactically. sign: ``-std c99``. At most one occurrence is allowed. - ``parameter_list_option`` - same as the above, but more than one option - occurence is allowed. + 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 @@ -314,7 +268,7 @@ separate option groups syntactically. (``=file`` will be interpreted as option value). At most one occurrence is allowed. - - ``prefix_list_option`` - same as the above, but more than one occurence of + - ``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 @@ -380,42 +334,17 @@ separate option groups syntactically. Usage examples: ``(switch_option "foo", (init true))``; ``(prefix_option "bar", (init "baz"))``. - - ``extern`` - this option is defined in some other plugin, see `below`__. - - __ extern_ - -.. _extern: - -External options ----------------- - -Sometimes, when linking several plugins together, one plugin needs to -access options defined in some other plugin. Because of the way -options are implemented, such options must be marked as -``extern``. This is what the ``extern`` option property is -for. Example:: - - ... - (switch_option "E", (extern)) - ... - -If an external option has additional attributes besides 'extern', they are -ignored. See also the section on plugin `priorities`__. - -__ priorities_ - .. _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. +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:: @@ -439,20 +368,19 @@ Examples:: (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. +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. +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: @@ -526,72 +454,75 @@ use TableGen inheritance instead. 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 ``include/llvm/CompilerDriver/Tools.td`` file):: +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"), - (cmd_line "llvm-g++ -c $INFILE -o $OUTFILE -emit-llvm"), + (command "llvm-g++ -c -emit-llvm"), (sink) ]>; This defines a new tool called ``llvm_gcc_cpp``, which is an alias for -``llvm-g++``. As you can see, a tool definition is just a list of -properties; most of them should be self-explanatory. The ``sink`` -property means that this tool should be passed all command-line -options that aren't mentioned in the option list. +``llvm-g++``. As you can see, a tool definition is just a list of properties; +most of them should be self-explanatory. The ``sink`` property means that this +tool should be passed all command-line options that aren't mentioned in the +option list. The complete list of all currently implemented tool properties follows. * Possible tool properties: - ``in_language`` - input language name. Can be given multiple arguments, in - case the tool supports multiple input languages. + case the tool supports multiple input languages. Used for typechecking and + mapping file extensions to tools. - ``out_language`` - output language name. Multiple output languages are - allowed. + allowed. Used for typechecking the compilation graph. - - ``output_suffix`` - output file suffix. Can also be changed - dynamically, see documentation on actions. + - ``output_suffix`` - output file suffix. Can also be changed dynamically, see + documentation on `actions`__. + +__ actions_ - - ``cmd_line`` - the actual command used to run the tool. You can - use ``$INFILE`` and ``$OUTFILE`` variables, output redirection - with ``>``, hook invocations (``$CALL``), environment variables + - ``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. + - ``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. + - ``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`` - 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:: +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"), - (cmd_line "llvm-gcc $INFILE -o $OUTFILE"), + (command "llvm-gcc"), (join), (actions (case (not_empty "L"), (forward "L"), (not_empty "l"), (forward "l"), @@ -599,18 +530,17 @@ illustrates this feature:: [(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 ``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 "join" property used in the example means that this tool behaves like a +linker. The list of all possible actions follows. @@ -656,10 +586,10 @@ The list of all possible actions follows. 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:: +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"]>, @@ -673,9 +603,7 @@ For example, without those definitions the following command wouldn't work:: llvmc: Unknown suffix: cpp The language map entries are needed only for the tools that are linked from the -root node. Since a tool can't have multiple output languages, for inner nodes of -the graph the input and output languages should match. This is enforced at -compile-time. +root node. A tool can have multiple output languages. Option preprocessor =================== @@ -686,7 +614,7 @@ 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 the built-in Base plugin):: +occasions. Example (adapted from ``llvm/src/Base.td.in``):: def Preprocess : OptionPreprocessor< @@ -705,7 +633,7 @@ 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 plugin is loaded. The only allowed actions +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 @@ -726,30 +654,28 @@ More advanced topics Hooks and environment variables ------------------------------- -Normally, LLVMC executes programs from 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 easily achieved via -the hooks mechanism. To write your own hooks, just add their -definitions to the ``PluginMain.cpp`` or drop a ``.cpp`` file into the -your plugin 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 -``cmd_line`` tool property:: +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:: - (cmd_line "$CALL(MyHook)/path/to/file -o $CALL(AnotherHook)") + (command "$CALL(MyHook)/path/to/file -o $CALL(AnotherHook)") To pass arguments to hooks, use the following syntax:: - (cmd_line "$CALL(MyHook, 'Arg1', 'Arg2', 'Arg # 3')/path/to/file -o1 -o2") + (command "$CALL(MyHook, 'Arg1', 'Arg2', 'Arg # 3')/path/to/file -o1 -o2") It is also possible to use environment variables in the same manner:: - (cmd_line "$ENV(VAR1)/path/to/file -o $ENV(VAR2)") + (command "$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`__):: - (cmd_line + (command (case (switch_on "E"), "llvm-g++ -E -x c $INFILE -o $OUTFILE", @@ -758,42 +684,21 @@ the ``case`` expression (documented `above`__):: __ case_ -.. _priorities: - -How plugins are loaded ----------------------- - -It is possible for LLVMC plugins to depend on each other. For example, -one can create edges between nodes defined in some other plugin. To -make this work, however, that plugin should be loaded first. To -achieve this, the concept of plugin priority was introduced. By -default, every plugin has priority zero; to specify the priority -explicitly, put the following line in your plugin's TableGen file:: - - def Priority : PluginPriority<$PRIORITY_VALUE>; - # Where PRIORITY_VALUE is some integer > 0 - -Plugins are loaded in order of their (increasing) priority, starting -with 0. Therefore, the plugin with the highest priority value will be -loaded last. - Debugging --------- -When writing LLVMC plugins, 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``. This command 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. These checks can't -be performed at compile-time because the plugins can load code -dynamically. When invoked with ``--check-graph``, ``llvmc`` doesn't -perform any compilation tasks and returns the number of encountered -errors as its status code. +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/ @@ -821,7 +726,7 @@ accessible only in the C++ code (i.e. hooks). Use the following code:: 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 ``Base`` plugin behaves when it needs to choose the correct linker options +the ``llvmc`` program behaves when it needs to choose the correct linker options (think ``g++`` vs. ``gcc``). .. raw:: html |