RealView® Developer Kit Compiler and Libraries Guide 2.3.10. Specifying the target processor or architecture

2.3.10. Specifying the target processor or architecture

These options enable you to specify the target processor or architecture attributes for a compilation. The compiler can take advantage of certain extra features of the selected processor or architecture, such as support for halfword load and store instructions and instruction scheduling.

Note

Specifying the target processor might make the code incompatible with other ARM processors.

You can specify how the compiler is configured at start-up using either:

--arm: To target the ARM instruction set. This is the default.
--thumb: To target the Thumb instruction set.

For more details on these options, see Targeting the instruction set.

The following general points apply to processor and architecture options:

The supported --cpu values are all current ARM product names or architecture versions. There are no aliases or wildcard matching.
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 either the ARM926EJ-S™ or ARM946E-S™.
If you specify a processor for the --cpu option, for example --cpu ARM926EJ-S, the compiled code is optimized for that processor. This enables the compiler to use specific coprocessors or instruction scheduling for optimum performance.
Use only a single processor or architecture name with --cpu. You cannot specify both a processor and an architecture.
If --cpu is not specified, the default is --cpu 5TE.
Specifying a processor that supports Thumb instructions, such as --cpu ARM926EJ-S 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.

The following options are available:

--cpu list

Lists the supported architecture and processor names that you can use with the --cpu name option.

--cpu name

This option generates code for a specific ARM processor or architecture.

If name is a processor:

You must enter the name exactly as it is shown on ARM data sheets, for example ARM926EJ-S. Wildcard characters are not accepted.
Selecting the processor selects the appropriate architecture, Floating-Point Unit (FPU), and memory organization.
Some specifications of --cpu imply an --fpu selection. For example, when compiling with the --arm option, --cpu ARM1136JF-S implies --fpu vfpv2. Be aware that any explicit FPU (set with --fpu) on the command line overrides an implicit FPU.
If no --fpu option and no --cpu option are specified, --fpu softvfp is used.

If name is an architecture, it must be one of:

5TE: ARMv5 with long multiply, Thumb, interworking, DSP multiply, and double-word instructions.

--fpu list

Lists the supported FPU architecture names that you can use with the --fpu name option.

Deprecated options are not listed.

--fpu name

This option determines the target FPU architecture. If you specify this option, it overrides any implicit FPU option that appears on the command line, for example, where you use the --cpu option.

Valid options for name are:

none: Selects no floating-point option. No floating-point code is to be used. This produces an error if your code contains floats.
softvfp: Selects the software floating-point library (fplib). This is the default if you do not specify a --fpu option, or if you select a CPU that does not have an FPU.

To get a full list of FPU architectures use the --fpu list option.

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