RealView Compilation Tools - ARM Information Center

Compiler Command-line Options
• If you specify a processor for the --cpu option, the compiled code
is optimized for that processor. This enables the compiler to use
specific coprocessors or instruction scheduling for optimum
performance.
Architectures
• If you specify an architecture name for the --cpu option, the code
is compiled to run on any processor supporting that architecture.
For example, --cpu=5TE produces code that can be used by the
ARM926EJ-S ® .
FPU
• Some specifications of --cpu imply an --fpu selection. For
example, when compiling with the --arm option, --cpu=ARM1136JF-S
implies --fpu=vfpv2. Similarly, --cpu=Cortex-R4F implies
--fpu=vfpv3_d16.
Note
Any explicit FPU, set with --fpu on the command line, overrides an
implicit FPU.
• If no --fpu option is specified and no --cpu option is specified,
--fpu=softvfp is used.
ARM/Thumb
• Specifying a processor or architecture that supports Thumb
instructions, such as --cpu=ARM7TDMI, does not make the compiler
generate Thumb code. It only enables features of the processor to
be used, such as long multiply. Use the --thumb option to generate
Thumb code, unless the processor is a Thumb-only processor, for
example Cortex-M3. In this case, --thumb is not required.
Note
Specifying the target processor or architecture might make the
object code generated by the compiler incompatible with other
ARM processors. For example, code compiled for architecture
ARMv6 might not run on an ARM920T processor, if the compiled
code includes instructions specific to ARMv6. Therefore, you must
choose the lowest common denominator processor suited to your
purpose.
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