Customizing LLVMC: Reference Manual
-Note: This document is a work-in-progress. Additions and clarifications - are welcome.
+ +Contents
+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 @@ -25,46 +54,33 @@ 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. This makes it possible to adapt LLVMC for other -purposes - for example, as a build tool for game resources.
-Because LLVMC employs TableGen [1] as its configuration language, you +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.
+Because LLVMC employs TableGen as its configuration language, you need to be familiar with it to customize LLVMC.
--
-
- Compiling with LLVMC -
- Predefined options -
- Customizing LLVMC: the compilation graph -
- Writing a tool description -
- Option list - specifying all options in a single place -
- Using hooks and environment variables in the cmd_line property -
- Conditional evaluation: the case expression -
- Language map -
- References -
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: -$ llvmc2 -O3 -Wall hello.cpp +$ 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++ and -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:
+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:
-$ llvmc2 -x c hello.cpp -$ # hello.cpp is really a C file +$ # hello.c is really a C++ file +$ llvmc -x c++ hello.c $ ./a.out hello@@ -72,76 +88,163 @@ hello object files you should provide the --linker option since it's impossible for LLVMC to choose the right linker in that case:
-$ llvmc2 -c hello.cpp -$ llvmc2 hello.o +$ llvmc -c hello.cpp +$ llvmc hello.o [A lot of link-time errors skipped] -$ llvmc2 --linker=c++ hello.o +$ 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 -configuration files:
+configuration libraries:- -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. -
- --view-graph - Show a graphical representation of the compilation -graph. Requires that you have dot and gv commands -installed. Hidden option, useful for debugging. -
- --write-graph - Write a compilation-graph.dot file in the -current directory with the compilation graph description in the -Graphviz format. Hidden option, useful for debugging. -
- --save-temps - Write temporary files to the current directory -and do not delete them on exit. Hidden option, useful for debugging. +
- --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. 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. +
- --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. +
- --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.
- --help, --help-hidden, --version - These options have their standard meaning.
At the time of writing LLVMC does not support on-the-fly reloading of -configuration, so to customize LLVMC you'll have to recompile the -source code (which lives under $LLVM_DIR/tools/llvmc2). The -default configuration files are Common.td (contains common -definitions, don't forget to include it in your configuration -files), Tools.td (tool descriptions) and Graph.td (compilation -graph definition).
-To compile LLVMC with your own configuration file (say,``MyGraph.td``), -run make like this:
+Compiling LLVMC plugins
+It's easiest to start working on your own LLVMC plugin by copying the +skeleton project which lives under $LLVMC_DIR/plugins/Simple:
-$ cd $LLVM_DIR/tools/llvmc2 -$ make GRAPH=MyGraph.td TOOLNAME=my_llvmc +$ cd $LLVMC_DIR/plugins +$ cp -r Simple MyPlugin +$ cd MyPlugin +$ ls +Makefile PluginMain.cpp Simple.td ++
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).
+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:
++$ mv Simple.td MyPlugin.td ++
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:
++$ cd $LLVMC_DIR/plugins/Simple +$ make +$ llvmc -load $LLVM_DIR/Release/lib/plugin_llvmc_Simple.so ++
Compiling standalone LLVMC-based drivers
+By default, the llvmc executable consists of a driver core plus several +statically linked plugins (Base and Clang at the moment). You can +produce a standalone LLVMC-based driver executable by linking the core with your +own plugins. The recommended way to do this is by starting with the provided +Skeleton example ($LLVMC_DIR/example/Skeleton):
++$ cd $LLVMC_DIR/example/ +$ cp -r Skeleton mydriver +$ cd mydriver +$ vim Makefile +[...] +$ make ++
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 $LLVMC_OBJ_DIR/example/mydriver +$ 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:
++include "llvm/CompilerDriver/Common.td"-
This will build an executable named my_llvmc. There are also -several sample configuration files in the llvmc2/examples -subdirectory that should help to get you started.
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 Graph.td) is -just a list of edges:
+The definition of the compilation graph (see file +plugins/Base/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<"root", "llvm_gcc_c">,
+ Edge<"root", "llvm_gcc_assembler">,
...
- Edge<llvm_gcc_c, llc>,
- Edge<llvm_gcc_cpp, llc>,
+ Edge<"llvm_gcc_c", "llc">,
+ Edge<"llvm_gcc_cpp", "llc">,
...
- OptionalEdge<llvm_gcc_c, opt, [(switch_on "opt")]>,
- OptionalEdge<llvm_gcc_cpp, opt, [(switch_on "opt")]>,
+ 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,
+ 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))>,
@@ -150,28 +253,215 @@ def CompilationGraph : CompilationGraph<[
]>;
As you can see, the edges can be either default or optional, where -optional edges are differentiated by sporting a case expression -used to calculate the edge's weight.
+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.
+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 +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 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.
To get a visual representation of the compilation graph (useful for -debugging), run llvmc2 --view-graph. You will need dot and +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 +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. 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.
+-
+
Possible option types:
++
+-
+
- switch_option - a simple boolean switch without arguments, for example +-O2 or -time. At most one occurrence is allowed. +
- 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 +occurence 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 occurence 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") +
+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 zero_or_one and one_or_more. +
- one_or_more - the option must be specified at least one time. Useful +only for list options in conjunction with multi_val; for ordinary lists +it is synonymous with required. Incompatible with required and +zero_or_one. +
- zero_or_one - the option can be specified zero or one times. Useful +only for list options in conjunction with multi_val. Incompatible with +required 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. +
- multi_val n - this option takes n arguments (can be useful in some +special cases). Usage example: (parameter_list_option "foo", (multi_val +3)). Only list options can have this attribute; you can, however, use +the one_or_more and zero_or_one properties. +
- init - this option has a default value, either a string (if it is a +parameter), or a boolean (if it is a switch; boolean constants are called +true and false). List options can't have this attribute. Usage +examples: (switch_option "foo", (init true)); (prefix_option "bar", +(init "baz")). +
- extern - this option is defined in some other plugin, see below. +
+
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.
+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. Example: (switch_on "opt"). +
- parameter_equals - Returns true if a command-line parameter equals +a given value. +Example: (parameter_equals "W", "all"). +
- element_in_list - Returns true if a command-line parameter +list contains a given value. +Example: (parameter_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 +equals to the argument. At the moment works only with cmd_line +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. +Example: (not_empty "o"). +
- empty - The opposite of not_empty. Equivalent to (not (not_empty +X)). Provided for convenience. +
- 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 binary 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 binary logical combinator that returns true iff any of its +arguments returns 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 Tools.td file):
+(taken from the include/llvm/CompilerDriver/Tools.td file):
def llvm_gcc_cpp : Tool<[
(in_language "c++"),
@@ -185,25 +475,35 @@ def llvm_gcc_cpp : Tool<[
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 lack explicit descriptions.
-The complete list of the currently implemented tool properties follows:
+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. -
- out_language - output language name. -
- output_suffix - output file suffix. +
- in_language - input language name. Can be either a string or a +list, in case the tool supports multiple input languages. +
- out_language - output language name. Tools are not allowed to +have multiple output languages. +
- output_suffix - output file suffix. Can also be changed +dynamically, see documentation on 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 -(via $ENV) and the case construct (more on this below). +(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).
The next tool definition is slightly more complex:
+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"),
@@ -211,96 +511,104 @@ def llvm_gcc_linker : Tool<[
(output_suffix "out"),
(cmd_line "llvm-gcc $INFILE -o $OUTFILE"),
(join),
- (prefix_list_option "L", (forward),
- (help "add a directory to link path")),
- (prefix_list_option "l", (forward),
- (help "search a library when linking")),
- (prefix_list_option "Wl", (unpack_values),
- (help "pass options to linker"))
+ (actions (case (not_empty "L"), (forward "L"),
+ (not_empty "l"), (forward "l"),
+ (not_empty "dummy"),
+ [(append_cmd "-dummy1"), (append_cmd "-dummy2")])
]>;
-This tool has a "join" property, which means that it behaves like a -linker. This tool also defines several command-line options: -l, --L and -Wl which have their usual meaning. An option has two -attributes: a name and a (possibly empty) list of properties. All -currently implemented option types and properties are described below:
+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 option types:
--
--
-
- switch_option - a simple boolean switch, for example -time. -
- parameter_option - option that takes an argument, for example --std=c99; -
- parameter_list_option - same as the above, but more than one -occurence of the option is allowed. -
- prefix_option - same as the parameter_option, but the option name -and parameter value are not separated. -
- prefix_list_option - same as the above, but more than one -occurence 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") -
-Possible option properties:
+Possible actions:
-
-
- append_cmd - append a string to the tool invocation command. -
- forward - forward this option unchanged. +
- 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!"). +
- forward - forward an option unchanged. +Example: (forward "Wall"). +
- forward_as - Change the name of an option, but forward the +argument unchanged. +Example: (forward_as "O0", "--disable-optimization").
- output_suffix - modify the output suffix of this -tool. Example : (switch "E", (output_suffix "i"). -
- stop_compilation - stop compilation after this phase. +tool. +Example: (output_suffix "i").
+- stop_compilation - stop compilation after this tool processes +its input. Used without arguments.
- unpack_values - used for for splitting and forwarding comma-separated lists of options, e.g. -Wa,-foo=bar,-baz is converted to -foo=bar -baz and appended to the tool invocation -command. -
- help - help string associated with this option. Used for ---help output. -
- required - this option is obligatory. +command. +Example: (unpack_values "Wa,").
It can be handy to have all information about options gathered in a -single place to provide an overview. This can be achieved by using a -so-called OptionList:
+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 Options : OptionList<[ -(switch_option "E", (help "Help string")), -(alias_option "quiet", "q") -... -]>; +def LanguageMap : LanguageMap< + [LangToSuffixes<"c++", ["cc", "cp", "cxx", "cpp", "CPP", "c++", "C"]>, + LangToSuffixes<"c", ["c"]>, + ... + ]>;-
OptionList is also a good place to specify option aliases.
-Tool-specific option properties like append_cmd have (obviously) -no meaning in the context of OptionList, so the only properties -allowed there are help and required.
-Option lists are used at the file scope. See file -examples/Clang.td for an example of OptionList usage.
+For example, without those definitions the following command wouldn't work:
++$ llvmc hello.cpp +llvmc: Unknown suffix: cpp ++
The language map entries should be added only for tools that are +linked with the root node. Since tools are not allowed to have +multiple output languages, for nodes "inside" the graph the input and +output languages should match. This is enforced at compile-time.
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 names -in the configuration file. This can be achieved via the mechanism of -hooks - to compile LLVMC with your hooks, just drop a .cpp file into -tools/llvmc2 directory. Hooks should live in the hooks -namespace and have the signature std::string hooks::MyHookName -(void). They can be used from the cmd_line tool property:
+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:(cmd_line "$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") +
It is also possible to use environment variables in the same manner:
(cmd_line "$ENV(VAR1)/path/to/file -o $ENV(VAR2)")
To change the command line string based on user-provided options use -the case expression (documented below):
+the case expression (documented above):
(cmd_line
(case
@@ -310,111 +618,73 @@ the case expression (
"llvm-g++ -c -x c $INFILE -o $OUTFILE -emit-llvm"))
The 'case' construct can be used to calculate weights of the optional -edges and to choose between several alternative command line strings -in the cmd_line tool property. It is designed after the -similarly-named construct in functional languages and takes the form -(case (test_1), statement_1, (test_2), statement_2, ... (test_N), -statement_N). The statements are evaluated only if the corresponding -tests evaluate to true.
-Examples:
+How plugins are loaded
+It is possible for LLVMC plugins to depend on each other. For example, +one can create edges between nodes defined in some other plugin. To +make this work, however, that plugin should be loaded first. To +achieve this, the concept of plugin priority was introduced. By +default, every plugin has priority zero; to specify the priority +explicitly, put the following line in your plugin's TableGen file:
-// Increases edge weight by 5 if "-A" is provided on the -// command-line, and by 5 more if "-B" is also provided. -(case - (switch_on "A"), (inc_weight 5), - (switch_on "B"), (inc_weight 5)) - -// Evaluates to "cmdline1" if option "-A" is provided on the -// command line, otherwise to "cmdline2" -(case - (switch_on "A"), "cmdline1", - (switch_on "B"), "cmdline2", - (default), "cmdline3") +def Priority : PluginPriority<$PRIORITY_VALUE>; +# Where PRIORITY_VALUE is some integer > 0-
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 option is -provided by the user. Example: (switch_on "opt"). Note that -you have to define all possible command-line options separately in -the tool descriptions. See the next doc_text for the discussion of -different kinds of command-line options. -
- parameter_equals - Returns true if a command-line parameter equals -a given value. Example: (parameter_equals "W", "all"). -
- element_in_list - Returns true if a command-line parameter list -includes a given value. Example: (parameter_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 language of the input -file equals to the argument. Valid only when using case -expression in a cmd_line tool property. 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. Example: `(not_empty "o"). -
- 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 - Another logical combinator that returns true only if any -one of its arguments returns true. Example: (or (test1), -(test2), ... (testN)). -
-
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.
One last thing that you will need to modify when adding support for a -new language to LLVMC is 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 is -located in the file Tools.td and looks like this:
+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:
-def LanguageMap : LanguageMap<
- [LangToSuffixes<"c++", ["cc", "cp", "cxx", "cpp", "CPP", "c++", "C"]>,
- LangToSuffixes<"c", ["c"]>,
- ...
- ]>;
+namespace llvmc {
+extern const char* ProgramName;
+}
+
+std::string MyHook() {
+//...
+if (strcmp(ProgramName, "mydriver") == 0) {
+ //...
+
+}
-| [1] | TableGen Fundamentals -http://llvm.cs.uiuc.edu/docs/TableGenFundamentals.html |
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 +(think g++ vs. gcc).
++ + +
+
++LLVM Compiler Infrastructure
+ +Last modified: $Date: 2008-12-11 11:34:48 -0600 (Thu, 11 Dec 2008) $ +
- -
- - Last modified: $Date$ -