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RealView Compiler User's Guide
Preface Introduction Getting started with the ARM Compiler Compiler Features Coding Practices Optimizing code
Optimizing for size versus speed Optimization levels and the debug view Selecting the target device Optimizing loops Using volatile Code metrics Measuring code and data sizes Measuring stack use Reducing debug information in objects and librarie Functions Minimizing parameter passing overhead __value_in_regs __pure Placing ARM function qualifiers Inlining How the compiler decides to inline When is it practical for the compiler to inline? Managing inlining Inlining functions across multiple files Debugging data and the --[no]_inline keyword Marking functions as static Setting breakpoints on inlined functions in ROM im Aligning data About data alignment The __packed qualifier and unaligned accesses to d __packed structures versus individually __packed f Using floating-point arithmetic Support for floating-point operations VFP architectures The --fpu option Floating-point linkage The --fpmode option Using the --fpu option VFP support Trapping and identifying division-by-zero errors Integer division (Software) Floating point division Support for ARM architecture v6 Instruction generation Alignment support Endian support Diagnostic Messages Using the Inline and Embedded Assemblers SemihostingEndian support
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| Home > Coding Practices > Support for ARM architecture v6 > Endian support | |||
You can produce either little endian objects or big endian objects using the compiler command-line options --littleend and --bigend respectively.
ARMv6 introduces two different endian modes for big endian objects:
the ARMv6 endian mode BE8
the pre-ARMv6 or legacy endian mode BE32.
By default, the compiler generates BE8 big endian objects when compiling for ARMv6 big endian. The compiler sets a flag in the object code object code that labels the code as BE8. Therefore, to enable BE8 support in the ARM core you normally need to set the E-bit in the CPSR.
You can link legacy objects with v6 objects for running on ARMv6 if you wish. However, in this case the linker switches the byte order of the legacy object code into BE8 mode. The resulting image is BE8.
To use the pre-ARMv6 or legacy BE32 mode you must tie the BIGENDINIT input into the core HIGH, or set the B bit (bit 7) of CP15 register 1 in your initialization code.
Note
You must link BE32-compatible code using the linker option --be32. Otherwise, the v6 attribute of the objects causes a BE8 image to be produced.
For more information see:
‑‑bigend in the Compiler Reference Guide
‑‑littleend in the Compiler Reference Guide
‑‑[no_]unaligned_access in the Compiler Reference Guide
--be8 in Specifying Byte Addressing mode in the Linker Guide
--be32 in Specifying Byte Addressing mode in the Linker Guide.
| Copyright © 2007 ARM Limited. All rights reserved. | ARM DUI 0375A |
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