ARM Compiler toolchain v4.1 for µVision Using the Compiler

Compiler Coding Practices
5.30 Advantages of natural data alignment
The various C data types are aligned on specific byte boundaries to maximize storage potential
and to provide for fast, efficient memory access with the ARM instruction set. For example, the
ARM architecture can access a four-byte variable using only one instruction when the object is
stored at an address divisible by four, so four-byte objects are located on four-byte boundaries.
ARM and Thumb processors are designed to efficiently access naturally aligned data, that is,
doublewords that lie on addresses that are multiples of eight, words that lie on addresses that are
multiples of four, halfwords that lie on addresses that are multiples of two, and single bytes that
lie at any byte address. Such data is located on its natural size boundary.
5.30.1 See also
Concepts
• Compiler storage of data objects by natural byte alignment on page 5-43
• Relevance of natural data alignment at compile time on page 5-44.
ARM DUI 0375C Copyright © 2007-2008, 2011 ARM. All rights reserved. 5-42
ID061811
Non-Confidential