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Linker User Guide
Conventions and feedback
Overview of the linker
Linking models supported by armlink
Image structure and generation
Using linker optimizations
Elimination of common debug sections
Elimination of common groups or sections
Elimination of unused sections
Elimination of unused virtual functions
About linker feedback
Example of using linker feedback
About link-time code generation
Optimization with RW data compression
How the linker chooses a compressor
Overriding the compression algorithm used by the l
How compression is applied
Working with RW data compression
Inlining functions with the linker
Factors that influence function inlining
Handling branches that optimize to a NOP
About reordering of tail calling sections
Restrictions on reordering of tail calling section
About merging comment sections
Getting information about images
Accessing and managing symbols with armlink
Using scatter files
About linker feedback
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| Home > Using linker optimizations > About linker feedback | |||
Linker feedback is a collaboration between the compiler and linker that can increase the amount of unused code that can be removed from an ELF image.
The feedback option produces a text file containing a list of unused functions, and functions that have been inlined by the linker. This information can be fed back to the compiler, which can rebuild the objects, placing these functions in their own sections. These sections can then be removed by the linker during usual unused section elimination.
The feedback file has the following format:
;#<FEEDBACK># ARM Linker,N.nn[Buildnum]: Last Updated:day mmm dd hh:mm:ss yyyy;VERSION 0.2 ;FILEfilename.ounused_function<= USED 0inlined_function<= LINKER_INLINED ...
The feedback file contains an entry for each object file. Each entry contains:
the object filename specified as a comment:
;FILEfilename.oa list of the functions in that file that are not used:
unused_function<= USED 0a list of the functions in that file that are inlined by the linker:
inlined_function<= LINKER_INLINED
To use linker feedback, specify --feedback on
the linker and compiler command lines.file
Note
The compiler issues a warning message if no feedback file
exists. Therefore, you might want to leave the --feedback option
off the first invocation of the compiler.file
Additional feedback options are provided by the linker:
If you are using scatter-loading then an executable ELF image cannot be created if your code does not fit into the region limits described in your scatter file. In this case use the
--feedback_image=command-line option.optionTo control the information that the linker puts into the feedback file, use the
--feedback_type=command-line option. You can control whether or not to list functions that require interworking or unused functions.type
See also- Tasks
- Concepts
- Reference
Linker Reference:
Compiler Reference:
| Copyright © 2007-2008, 2011-2012 ARM. All rights reserved. | ARM DUI 0377D |
| Non-Confidential | ID062912 |
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| Home > Using linker optimizations > About linker feedback |
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