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-munaligned-access, -mno-unaligned-access

Enables or disables unaligned accesses to data on ARM processors.

The compiler defines the __ARM_FEATURE_UNALIGNED macro when -munaligned-access is enabled.

The libraries include special versions of certain library functions designed to exploit unaligned accesses. When unaligned access support is enabled, using -munaligned-access, the compilation tools use these library functions to take advantage of unaligned accesses. When unaligned access support is disabled, using -mno-unaligned-access, these special versions are not used.

Default

-munaligned-access is the default for architectures that support unaligned accesses to data. This applies to all architectures supported by ARM Compiler 6, except ARMv6-M and ARMv8-M.baseline.

Usage

-munaligned-access

Use this option on processors that support unaligned accesses to data, to speed up accesses to packed structures.

Note

For ARMv6-M and ARMv8-M.baseline architectures, compiling with this option generates an error.
-mno-unaligned-access

If unaligned access is disabled, any unaligned data that is wider than 8-bit is accessed one byte at a time. For example, fields wider than 8-bit, in packed data structures, are always accessed one byte at a time even if they are aligned.

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