marvell-doc/MARVELL_GCC_Dump_Optimization_Options_Plugin.txt

GCC Plugins
===========

1. Introduction
2. GCC Dump Optimization Options Plugin
3. GCC Function Optimization Options Plugin 
4. Miscellaneous



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1. Introduction
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    GCC plugins (or loadable modules) make it possible for us to add new functionalities
without modifying the GCC itself. It shortens the time needed to build and test. Only
the code needed to implement the new functionality needs to be compiled. The Marvell GCC
plugins are for internal use, therefore, not suitable for inclusion in the main GCC distribution.


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2. GCC Dump Optimization Options Plugin
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    For various GCC versions, different optimization options are provided. It is a difficult
and time-consuming task to monitor the difference manually, therefore, the "GCC Optimization Options Plugin"
is provided to resolve the issue. By the plugin, the optimization options of various GCC versions
can be displayed automatically.

    Then, GYM project uses those optimization options to find out the best options set to compile
the target program.


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3. GCC Function Optimization Options Plugin
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    With the help of attributes and #pragmas, a single function can be complied by GCC with
specific optimization options. But this will involve source code modifications. Without source
code modifications, the unit to apply optimization options by GCC is a single file. Due to
the complexity of target program, it is a difficult and time-consuming task to modify source
code to compile a single function with specific optimization options. By the plugin, various
optimization options can be applied to a single function without source code modifications.

    Then, GYM project can use the plugin to find out the best optimization options set based on
a single function to compile the target program.


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4. Miscellaneous
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    The GCC Dump Optimization Options Plugin source code is in marvell gcc 4.6 toolchain sources.
Follows the instructions in http://10.19.133.152/wiki/doku.php?id=marvell_gcc-4.6_toolchain to get
the toolchain sources and build that toolchain.

    The source code of GCC Dump Optimization Options Plugin is at "mcc4.6"/src/extra-src/gcc-plugins/dopts.
Enter the plugin source directory and build it:

	cd gcc-4.6/src/extra-src/gcc-plugins/dopts
	make
	Note:
		The gcc 4.6 toolchain has to be built first
		Makefile variables
			* GCC
				Current value is i486-linux-gnu-gcc, if necessary, change it according to
				your build environment
			* CROSS
				Current value is arm-marvell-linux-gnueabi-, if necessary, change it according to
				the marvell toolchain you built

    The following make targets are provided to simplify the execution:

	* make runm
		Dump minimum optimization options
	* make runc
		Dump minimum optimization options with configuration file conf/mincfg.txt
	* make runx
		Dump maximum optimization options
	* make runa
		Dump all optimization options
	* make runi
		Dump all optimization options initial values
	* make run0
		Dump all optimization options current values for -O0
	* make run1
		Dump all optimization options current values for -O1
	* make run2
		Dump all optimization options current values for -O2
	* make run3
		Dump all optimization options current values for -O3
	* make runs
		Dump all optimization options current values for -Os
	* make runf
		Dump all optimization options current values for -Ofast


    The GCC Function Optimization Options Plugin source code is in marvell gcc 4.6 toolchain sources.
Follows the instructions in http://10.19.133.152/wiki/doku.php?id=marvell_gcc-4.6_toolchain to get
the toolchain sources and build that toolchain.

    The source code of GCC Function Optimization Options Plugin is at "mgcc4.6"/src/extra-src/gcc-plugins/fopts.
Enter the plugin source directory and build it:

	cd gcc-4.6/src/extra-src/gcc-plugins/fopts
	make
	Note:
		The gcc 4.6 toolchain has to be built first
		Makefile variables
			* GCC
				Current value is i486-linux-gnu-gcc, if necessary, change it according to
				your build environment
			* CROSS
				Current value is arm-marvell-linux-gnueabi-, if necessary, change it according to
				the marvell toolchain you built

    The make target run is provided to demo the execution:

	* make run
		Apply the specific optimization options to the specified function according to configuration file
		conf/optcfg.txt