RealView Compilation Tools - ARM Information Center

Compiler Command-line Options
• --gnu_defaults on page 2-68.
2.1.149 --signed_chars, --unsigned_chars
This option makes the char type signed or unsigned.
When char is signed, the macro __FEATURE_SIGNED_CHAR is defined by the compiler.
Note
Care must be taken when mixing translation units that have been compiled with and
without this option, and that share interfaces or data structures.
The ARM ABI defines char as an unsigned byte, and this is the interpretation used by
the C++ libraries supplied with RVCT.
Default
The default is --unsigned_chars.
See also
• Predefined macros on page 4-198.
2.1.150 --split_ldm
This option instructs the compiler to split LDM and STM instructions into two or more LDM
or STM instructions.
When --split_ldm is selected, the maximum number of register transfers for an LDM or
STM instruction is limited to:
• five, for all STMs
• five, for LDMs that do not load the PC
• four, for LDMs that load the PC.
Where register transfers beyond these limits are required, multiple LDM or STM
instructions are used.
Usage
The --split_ldm option can be used to reduce interrupt latency on ARM systems that:
• do not have a cache or a write buffer, for example, a cacheless ARM7TDMI
• use zero-wait-state, 32-bit memory.
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