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Technical Support
On-Line Manuals
Linker User Guide
Preface
Overview of the Linker
Linking Models Supported by armlink
Image Structure and Generation
Linker Optimization Features
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
Optimization with RW data compression
How the linker chooses a compressor
Options available to override the compression algo
How compression is applied
Considerations when working with RW data compressi
Function inlining with the linker
Factors that influence function inlining
About branches that optimize to a NOP
Linker reordering of tail calling sections
Restrictions on reordering of tail calling section
Linker merging of comment sections
Getting Image Details
Accessing and Managing Symbols with armlink
Scatter-loading Features
Scatter File Syntax
Linker Command-line Options
Linker Steering File Command Reference
Via File Syntax
Elimination of unused sections
| Non-Confidential |  PDF version | ARM DUI0377H | ||
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| Home > Linker Optimization Features > Elimination of unused sections | ||||
4.3 Elimination of unused sections
Elimination of unused sections is the most significant optimization on image size that is performed by the linker.
Unused section elimination:
-
Removes unreachable code and data from the final image.
-
Is suppressed in cases that might result in the removal of all sections.
To control this optimization use the
--remove,
--no_remove, --first, --last, and
--keep linker options.Unused section elimination requires an entry point. Therefore, if there is no entry point
specified for an image, use the
--entry linker option to specify an entry
point and permit unused section elimination to work, if it is enabled.Use the
--info unused linker option to instruct the linker to generate a
list of the unused sections that it eliminates.An input section is retained in the final image when:
- It contains an entry point.
- It is referred to, directly or indirectly, by a non-weak reference from an input section containing an entry point.
- It is specified as the first or last input section by the
--firstor--lastoption (or a scatter-loading equivalent). - It is marked as unremovable by the
--keepoption.
Note
Compilers usually collect functions and data together and emit one
section for each category. The linker can only eliminate a section if it is entirely
unused.
You can mark a function or variable in source code with the
__attribute__((used)) attribute. This causes armcc to generate the symbol __tagsym$$used for each of the functions and variables. A section containing a
definition of __tagsym$$used is not removed by unused
section elimination.You can also use the
--split_sections
compiler command-line option to instruct the compiler to generate one ELF section for each
function in the source file.Related concepts
Related reference
| Non-Confidential | PDF version | ARM DUI0377H |
| Copyright © 2007, 2008, 2011, 2012, 2014-2016 ARM. All rights reserved. |
| Home > Linker Optimization Features > Elimination of unused sections |
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