From cTuning.org
Common page for GSOC09 and other developments in summer 2009: function cloning, fine-grain optimizations, program instrumentation:
Contents |
Fine-grain optimization project
Yuanjie Huang (ICT, China)
This project aims to provide fine-grain optimization selection and tuning abilities in GCC, and thus enable GCC to tune default optimization heuristic of the compiler or fine optimizations for a given program on a given architecture entirely automatically using statistical and machine learning techniques from the MILEPOST project.
ICI Events
ICI events added to the framework for fine-grain tuning are documented here.
ICI Features
ICI features added to the framework for fine-grain tuning are documented here.
| Feature name | Type of contents | Description |
|---|---|---|
| "main_input_filename" | array of strings, i.e., char ** | Name of the file which serves as the main input file of compiler . |
Known Issue on Current ICI Features
- "function_filename" can be empty for functions generated by IPCP optimization (cp pass).
ICI Parameters
ICI parameters now come with a type which should be declared when registering parameters in ICI, currently only a few basic C types are supported: void, char, unsigned char, int, unsigned int, long and unsigned long. A special type named EP_SILENT is introduced to pass parameters that is only used to pass status information to plugin; it's actually int, and is planned to be replaced by a elegant solution. The parameter type is defined in gcc/highlev-plugin-internal.h and gcc/highlev-plugin.h:
typedef enum
{
EP_SILENT,
EP_VOID,
EP_CHAR,
EP_UNSIGNED_CHAR,
EP_INT;
EP_UNSIGNED_INT,
EP_LONG,
EP_UNSIGNED_LONG
} event_parameter_type;
The representation of parameters is defined in file gcc/events.c:
/* Parameter structure. */
struct event_parameter
{
const char *name; /* Name for the parameter */
const void *value; /* Pointer to data */
event_parameter_type type; /* Type enumeration of value */
};
ICI API
register_event_parameter_type: get the type of an ICI event parameter
| Description
Define a new ICI parameter named name, with a pointer value to some data of type. Trigger an internal compiler error (failed assertion) if name is invalid. Prerequisites name can be neither NULL nor an empty string. <type> is a valid type defined in event_parameter_type. Outputs See also |
get_event_parameter_type: get the type of an ICI event parameter
| Description
Prerequisites Parameter hash table must have been initialized. Outputs Informational message if parameters hash table does not exists. See also |
Plugins
Plugins developed for fine-grain tuning are documented here. These plugins are developed to work with ICI-2.0 interface.
adapt
Description
Adapt plugin provides support for GCC pass sequence record/substitution, function-specific optimization tuning, function clone and instrumentation.
Use Scenario
This plugin behaves differently depending on the ICI_ADAPT_CONTROL environmental variable, which can be either set to 1 to record information of current compilation into XML files or to 2 to reuse passes from XML files to perform passes substitution, function clone and other functionalities.
Installation
Adapt plugin is depends on MXML library, which provides XML reading and writing ability.
To use adapt plugin with ICI, ICI_PLUGIN environment variable should be set to the path to the plugin library (.so), and invoke gcc with either -fici or ICI_USE environment parameter.
Events and parameters
- "pass_execution": this event is triggered when a GCC pass is about to run.
- "all_passes_manager":
- "avoid_gate":
State
This plugin now can record and reuse optimization passes without problem, with the following issues to solve:
- The compilation won't fall to default compilation process when no corresponding XML can be found.
- The plugin cannot handle interprocedual passes well.