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Compiler User Guide
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Overview of the Compiler
Getting Started with the Compiler
Compiler Features
Compiler Coding Practices
The compiler as an optimizing compiler
Compiler optimization for code size versus speed
Compiler optimization levels and the debug view
Selecting the target CPU at compile time
Optimization of loop termination in C code
Loop unrolling in C code
Compiler optimization and the volatile keyword
Code metrics
Code metrics for measurement of code size and data
Stack use in C and C++
Benefits of reducing debug information in objects
Methods of reducing debug information in objects a
Guarding against multiple inclusion of header file
Methods of minimizing function parameter passing o
Functions that return multiple values through regi
Functions that return the same result when called
Comparison of pure and impure functions
Recommendation of postfix syntax when qualifying f
Inline functions
Compiler decisions on function inlining
Automatic function inlining and static functions
Inline functions and removal of unused out-of-line
Automatic function inlining and multifile compilat
Restriction on overriding compiler decisions about
Compiler modes and inline functions
Inline functions in C++ and C90 mode
Inline functions in C99 mode
Inline functions and debugging
Types of data alignment
Advantages of natural data alignment
Compiler storage of data objects by natural byte a
Relevance of natural data alignment at compile tim
Unaligned data access in C and C++ code
The __packed qualifier and unaligned data access i
Unaligned fields in structures
Performance penalty associated with marking whole
Unaligned pointers in C and C++ code
Unaligned Load Register (LDR) instructions generat
Comparisons of an unpacked struct, a __packed stru
Compiler support for floating-point arithmetic
Default selection of hardware or software floating
Example of hardware and software support differenc
Vector Floating-Point (VFP) architectures
Limitations on hardware handling of floating-point
Implementation of Vector Floating-Point (VFP) supp
Compiler and library support for half-precision fl
Half-precision floating-point number format
Compiler support for floating-point computations a
Types of floating-point linkage
Compiler options for floating-point linkage and co
Floating-point linkage and computational requireme
Processors and their implicit Floating-Point Units
Integer division-by-zero errors in C code
About trapping integer division-by-zero errors wit
About trapping integer division-by-zero errors wit
Identification of integer division-by-zero errors
Examining parameters when integer division-by-zero
Software floating-point division-by-zero errors in
About trapping software floating-point division-by
Identification of software floating-point division
Software floating-point division-by-zero debugging
New language features of C99
New library features of C99
// comments in C99 and C90
Compound literals in C99
Designated initializers in C99
Hexadecimal floating-point numbers in C99
Flexible array members in C99
__func__ predefined identifier in C99
inline functions in C99
long long data type in C99 and C90
Macros with a variable number of arguments in C99
Mixed declarations and statements in C99
New block scopes for selection and iteration state
_Pragma preprocessing operator in C99
Restricted pointers in C99
Additional <math.h> library functions in C99
Complex numbers in C99
Boolean type and <stdbool.h> in C99
Extended integer types and functions in <inttyp
<fenv.h> floating-point environment access i
<stdio.h> snprintf family of functions in C9
<tgmath.h> type-generic math macros in C99
<wchar.h> wide character I/O functions in C9
How to prevent uninitialized data from being initi
Compiler Diagnostic Messages
Using the Inline and Embedded Assemblers of the AR
Compiler User Guide
Compiler optimization levels and the debug view
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| Home > Compiler Coding Practices > Compiler optimization levels and the debug view | |||
The precise optimizations performed by the compiler depend both on the level of optimization chosen, and whether you are optimizing for performance or code size.
The compiler supports the following optimization levels:
-O0Minimum optimization. The compiler performs simple optimizations that do not impair the debug view.
When debugging is enabled, this option gives the best possible debug view.
-O1Restricted optimization.
When debugging is enabled, this option gives a generally satisfactory debug view with good code density.
-O2High optimization. This is the default optimization level.
When debugging is enabled, this option might give a less satisfactory debug view.
-O3Maximum optimization. This is the most aggressive form of optimization available. Specifying this option enables multifile compilation by default where multiple files are specified on the command line.
When debugging is enabled, this option typically gives a poor debug view.
Because optimization affects the mapping of object code to
source code, the choice of optimization level with -Ospace and -Otime generally
impacts the debug view.
The option -O0 is the best option to use
if a simple debug view is needed. Selecting -O0 typically increases
the size of the ELF image by 7 to 15%. To reduce the size of your
debug tables, use the --remove_unneeded_entities option.
See also- Tasks
- Concepts
- Reference
- Other information
ARM ELF File Formathttp://infocenter.arm.com/help/topic/com.arm.doc.dui0101-/index.html
| Copyright © 2007-2008, 2011-2012 ARM. All rights reserved. | ARM DUI 0375D |
| Non-Confidential | ID062912 |
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