ARM Software Development Toolkit Reference Guide 2.3.7. Specifying the target processor and architecture

2.3.7. Specifying the target processor and architecture

The options described below specify the target processor or architecture for a compilation. The compiler may take advantage of certain features of the selected processor or architecture, such as support for halfword instructions and instruction scheduling. This may make the code incompatible with other ARM processors.

If neither a -processor or -architecture option is specified, the default is -processor ARM7TDMI.

The following general points apply to processor and architecture options:

If you specify a -architecture option, the compiler compiles code that runs on any processor that supports that architecture.
- To enable halfword load and store instructions, specify one of the architecture 4 options, or specify an appropriate processor using a -processor option such as ARM7TDMI, ARM9TDMI, or StrongARM1.
- To enable long multiply, specify -architecture 3M, -architecture 4, -architecture 4M, or -architecture 4T, or specify an appropriate -processor option such as ARM7DMI.
If you specify a -processor option, the compiler compiles code and optimizes specifically for that processor. The code may be incompatible with other ARM processors that support the same architecture.
For example, a -processor option may imply the presence of specific coprocessors, or allow instruction scheduling for optimum performance on the specified processor.
Specifying a Thumb-aware processor, such as -processor ARM7TDMI, to armcc or armcpp does not make these compilers generate Thumb code. It only allows features of the processor to be used, such as support for halfword instructions. You must use tcc or tcpp to generate Thumb code.

The following options are available:

-architecture n

Specifies the ARM architecture version that compiled code will comply with. Valid values for n are:

3
3M
4
4M
4xM. This is architecture 4M without long multiply instructions.
4T
4TxM. This is architecture 4T without long multiply instructions.

It is not necessary to specify both -architecture and -processor. If a -architecture option is specified and a -processor option is not, the default processor is generic.

-cpu , name

This is a synonym for the -processor option.

-fpu, name

Select the target FPU, where name is one of:

none: No FPU. Use software floating point library. This option implies /softfp.
amp: Attached Media Processor
fpa: Floating Point Accelerator. This option implies /hardfp.

-processor, name

Compiles code for the specified ARM processor where name is the name of the ARM processor. It is not necessary to specify both -architecture and -processor. The -processor option is specific to an individual processor. The -architecture option compiles code for any processor that conforms to the specified architecture. Valid values are:

ARM6: Implements architecture 3.
ARM7: Implements architecture 3.
ARM7M: Implements architecture 3M.
ARM7TM: Implements architecture 4T.
ARM7T: Implements architecture 4TxM.
ARM7TDI: Implements architecture 4TxM.
ARM7TDMI: Implements architecture 4T. This is the default if no -processor and no -architecture options are specified. If -architecture is specified and -processor is not, the default processor is generic.
ARM8: Implements architecture 4.
ARM9: Implements architecture 4.
ARM9TDMI: Implements architecture 4T.
SA-110: Implements architecture 4.
StrongARM1: Implements architecture 4.
SA1500: Implements architecture 4. Selecting this processor option implies -fpu amp and -APCS /softdoubles.
generic: This processor name is used when compiling for a specified architecture and no -processor option is specified.

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