ARM Compiler toolchain Using the Linker - ARM Information Center

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Reference Linker Reference: • --entry=location on page 2-58 • --first=section_id on page 2-71 • --info=topic[,topic,...] on page 2-80 • --keep=section_id on page 2-89 • --last=section_id on page 2-93 • --remove, --no_remove on page 2-134. Compiler Reference: • --split_sections on page 3-190 • __attribute__((used)) function attribute on page 5-55 • __attribute__((used)) variable attribute on page 5-75. Using linker optimizations ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 5-5 ID080411 Non-Confidential
5.4 Elimination of unused virtual functions 5.4.1 See also Using linker optimizations Unused section elimination efficiently removes unused functions from C code. In C++ applications, virtual functions and RunTime Type Information (RTTI) objects are referenced by pointer tables, known as vtables. Without extra information, the linker cannot determine which vtable entries are accessed at runtime. This means that the standard unused section elimination algorithm used by the linker cannot guarantee to remove unused virtual functions and RTTI objects. Virtual Function Elimination (VFE) is a refinement of unused section elimination to reduce ROM size in images generated from C++ code. This optimization can be used to eliminate unused virtual functions and RTTI objects from your code. An input section that contains more that one function can only be eliminated if all the functions are unused. The linker cannot remove unused functions from within a section. VFE is a collaboration between the ARM compiler and the linker whereby the compiler supplies extra information about unused virtual functions that is then used by the linker. Based on this analysis, the linker is able to remove unused virtual functions and RTTI objects. Note For VFE to work, the assembler requires all objects using C++ to have VFE annotations. If the linker finds a C++ mangled symbol name in the symbol table of an object and VFE information is not present, it turns off the optimization. The compiler places the extra information in sections with names beginning .arm_vfe. These sections are ignored by the linker when it is not VFE-aware. Concepts • Elimination of common debug sections on page 5-2 • Elimination of common groups or sections on page 5-3 • Elimination of unused sections on page 5-4. Reference Linker Reference: • --vfemode=mode on page 2-186. Compiler Reference: • --rtti, --no_rtti on page 3-182. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 5-6 ID080411 Non-Confidential
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® ARM Copyright © 2010-2011 ARM.
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Contents ARM Compiler toolchain Usi
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Contents 7.15 Creating a symdefs fi
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Chapter 1 Conventions and feedback
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Chapter 2 Overview of the linker Th
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Concepts • Demand paging on page
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2.3 Linker command-line options lis
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• --keep_protected_symbols on pag
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• --eager_load_debug, --no_eager_
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2.5 What the linker outputs 2.5.1 S
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Chapter 3 Linking models supported
Page 23 and 24: 3.2 Bare-metal linking model 3.2.1
Page 25 and 26: Linking models supported by armlink
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Page 29 and 30: 3.7 Concepts common to both BPABI a
Page 31 and 32: Image structure and generation •
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Page 35 and 36: 4.3 Load view and execution view of
Page 37 and 38: 4.4 Methods of specifying an image
Page 39 and 40: 4.5 Types of simple image 4.5.1 See
Page 47 and 48: 4.10 About specifying an initial en
Page 49 and 50: 4.11.2 Example 4.11.3 See also The
Page 51 and 52: 4.13 Section alignment with the lin
Page 53 and 54: Reference Linker Reference: • --a
Page 55 and 56: 4.16 Overview of veneers 4.16.1 See
Page 57 and 58: 4.18 Veneer types 4.18.1 See also I
Page 59 and 60: 4.20 Reuse of veneers when scatter-
Page 61 and 62: 4.22 About weak references and defi
Page 63 and 64: BL init_foo ;Rest of code END 4.22.
Page 65 and 66: Image structure and generation 4.24
Page 67 and 68: 4.25 Specifying user libraries when
Page 69 and 70: 4.27 Use of the strict family of op
Page 71 and 72: 5.1 Elimination of common debug sec
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Page 77 and 78: • --scatter=file on page 2-142. C
Page 79 and 80: 5.6.1 See also Using linker optimiz
Page 81 and 82: 3. Creates the output image. 5.7.3
Page 83 and 84: 5.9 How the linker chooses a compre
Page 85 and 86: 5.11 How compression is applied 5.1
Page 87 and 88: 5.13 Inlining functions with the li
Page 89 and 90: Reference Assembler Reference: •
Page 91 and 92: 5.16 About reordering of tail calli
Page 93 and 94: 5.18 About merging comment sections
Page 95 and 96: 6.1 Linker options for getting info
Page 97 and 98: 6.3 Example of using the --info lin
Page 99 and 100: 6.4 How to find where a symbol is p
Page 101 and 102: • Load$$LR$$ load region symbols
Page 103 and 104: 7.2 Accessing linker-defined symbol
Page 105 and 106: 7.4 Image$$ execution region symbol
Page 107 and 108: 7.5.1 See also Accessing and managi
Page 109 and 110: 7.7 Region name values when not sca
Page 111 and 112: 7.9 Importing linker-defined symbol
Page 113 and 114: 7.11 Section-related symbols 7.11.1
Page 115 and 116: 7.13 Input section symbols 7.13.1 S
Page 117 and 118: 7.15 Creating a symdefs file 7.15.1
Page 119 and 120: 7.17 Reading a symdefs file 7.17.1
Page 121 and 122: 7.18.2 See also 0x0000814D T __argv
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7.22 Steering file format 7.22.1 Se
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7.24 Using $Super$$ and $Sub$$ to p
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Using scatter files • Images with
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8.2 When to use scatter-loading 8.2
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• --startup=symbol, --no_startup
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8.4.1 See also Concepts • About s
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8.5.1 See also } SRAM 0x8000 0x8000
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8.7 Specifying stack and heap using
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8.9 Creating root execution regions
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8.9.2 See also Tasks • Using the
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8.11 Placing functions and data at
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Using scatter files RAM 0x200000 (0
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Using scatter files • Using __at
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Developing Software for ARM ® Proc
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} } .ANY1(+RO) ; evenly distributed
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8.14 Examples of using placement al
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Using scatter files 8.15 Example of
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8.16 Examples of using sorting algo
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8.17 Selecting veneer input section
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Compiler Reference: • __attribute
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8.20 Restrictions on placing __at s
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8.21.1 See also Using scatter files
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8.23 Placing a key in flash memory
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8.25 Placement of sections with ove
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8.25.1 See also Using scatter files
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8.27 Example of placing code in a r
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8.29 Example of placing ARM C++ lib
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8.31 Reserving an empty region Usin
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8.32 About creating regions on page
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8.33 Overalignment of execution reg
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8.35 Expression evaluation in scatt
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8.37 Equivalent scatter-loading des
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Using scatter files Example 8-23 Po
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Using scatter files Example 8-25 Po
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Using scatter files • The ER_ZI e
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Using scatter files Example 8-29 Sc
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Chapter 9 GNU ld script support in
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9.2 Typical use cases for using ld
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Reference Linker Reference: • --l
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9.5 Recommendations for using ld sc
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.data : { __data_start = .; *(.data
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9.6.4 See also .got 0 : { *(.got.pl
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9.7.1 See also } .dynamic : { *(.dy
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9.8.1 See also { *(.bss .bss.*) . =
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Chapter 10 BPABI and SysV shared li
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BPABI and SysV shared libraries and
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10.3 Concepts common to all BPABI m
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10.5 Symbol visibility for BPABI mo
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10.6 Automatic import and export fo
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10.8 Symbol versioning for BPABI mo
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10.10 Linker options for SysV model
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10.13 Addressing modes in the SysV
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10.17 Linker options for bare metal
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10.21 Addressing modes in the BPABI
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10.23 About symbol versioning 10.23
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10.25 Example of creating versioned
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10.27 Linker options for enabling i
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Chapter 11 Features of the Base Pla
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Features of the Base Platform linki
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11.2 Example scatter file for the B
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Features of the Base Platform linki
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Change Topics affected Revisions fo
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