Chapter 13. ARM Dependent Features

13.1. Options

-mcpu=processor[+extension…]

This option specifies the target processor. The assembler will issue an error message if an attempt is made to assemble an instruction which will not execute on the target processor. The following processor names are recognized: arm1, arm2, arm250, arm3, arm6, arm60, arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm, arm7di, arm7dmi, arm70, arm700, arm700i, arm710, arm710t, arm720, arm720t, arm740t, arm710c, arm7100, arm7500, arm7500fe, arm7t, arm7tdmi, arm8, arm810, strongarm, strongarm1, strongarm110, strongarm1100, strongarm1110, arm9, arm920, arm920t, arm922t, arm940t, arm9tdmi, arm9e, arm946e-r0, arm946e, arm966e-r0, arm966e, arm10t, arm10e, arm1020, arm1020t, arm1020e, ep9312 (ARM920 with Cirrus Maverick coprocessor), i80200 (Intel XScale processor) iwmmxt (Intel(r) XScale processor with Wireless MMX(tm) technology coprocessor) and xscale. The special name all may be used to allow the assembler to accept instructions valid for any ARM processor.

In addition to the basic instruction set, the assembler can be told to accept various extension mnemonics that extend the processor using the co-processor instruction space. For example, -mcpu=arm920+maverick is equivalent to specifying -mcpu=ep9312. The following extensions are currently supported: +maverick +iwmmxt and +xscale.

-march=architecture[+extension…]

This option specifies the target architecture. The assembler will issue an error message if an attempt is made to assemble an instruction which will not execute on the target architecture. The following architecture names are recognized: armv1, armv2, armv2a, armv2s, armv3, armv3m, armv4, armv4xm, armv4t, armv4txm, armv5, armv5t, armv5txm, armv5te, armv5texp iwmmxt and xscale. If both -mcpu and -march are specified, the assembler will use the setting for -mcpu.

The architecture option can be extended with the same instruction set extension options as the -mcpu option.

-mfpu=floating-point-format

This option specifies the floating point format to assemble for. The assembler will issue an error message if an attempt is made to assemble an instruction which will not execute on the target floating point unit. The following format options are recognized: softfpa, fpe, fpe2, fpe3, fpa, fpa10, fpa11, arm7500fe, softvfp, softvfp+vfp, vfp, vfp10, vfp10-r0, vfp9, vfpxd, arm1020t and arm1020e.

In addition to determining which instructions are assembled, this option also affects the way in which the .double assembler directive behaves when assembling little-endian code.

The default is dependent on the processor selected. For Architecture 5 or later, the default is to assembler for VFP instructions; for earlier architectures the default is to assemble for FPA instructions.

-mthumb

This option specifies that the assembler should start assembling Thumb instructions; that is, it should behave as though the file starts with a .code 16 directive.

-mthumb-interwork

This option specifies that the output generated by the assembler should be marked as supporting interworking.

-mapcs [26|32]

This option specifies that the output generated by the assembler should be marked as supporting the indicated version of the Arm Procedure. Calling Standard.

-matpcs

This option specifies that the output generated by the assembler should be marked as supporting the Arm/Thumb Procedure Calling Standard. If enabled this option will cause the assembler to create an empty debugging section in the object file called .arm.atpcs. Debuggers can use this to determine the ABI being used by.

-mapcs-float

This indicates the the floating point variant of the APCS should be used. In this variant floating point arguments are passed in FP registers rather than integer registers.

-mapcs-reentrant

This indicates that the reentrant variant of the APCS should be used. This variant supports position independent code.

-EB

This option specifies that the output generated by the assembler should be marked as being encoded for a big-endian processor.

-EL

This option specifies that the output generated by the assembler should be marked as being encoded for a little-endian processor.

-k

This option specifies that the output of the assembler should be marked as position-independent code (PIC).

-moabi

This indicates that the code should be assembled using the old ARM ELF conventions, based on a beta release release of the ARM-ELF specifications, rather than the default conventions which are based on the final release of the ARM-ELF specifications.