ARM Compiler armasm User Guide : 11.3 --apcs=qualifier…qualifier

11.3 --apcs=qualifier…qualifier

Controls interworking and position independence when generating code.

Syntax

--apcs=qualifier...qualifier

Where qualifier...qualifier denotes a list of qualifiers. There must be:

At least one qualifier present.
No spaces or commas separating individual qualifiers in the list.

Each instance of qualifier must be one of:

none

Specifies that the input file does not use AAPCS. AAPCS registers are not set up. Other qualifiers are not permitted if you use none.

/interwork, /nointerwork

For ARMv7-A, /interwork specifies that the code in the input file can interwork between ARM and Thumb safely.

For ARMv8-A, /interwork specifies that the code in the input file can interwork between A32 and T32 safely.

The default is /nointerwork.

/nointerwork is not supported for AArch64 state.

/inter, /nointer

Are synonyms for /interwork and /nointerwork.

/inter is not supported for AArch64 state.

/ropi, /noropi

/ropi specifies that the code in the input file is Read-Only Position-Independent (ROPI). The default is /noropi.

/pic, /nopic

Are synonyms for /ropi and /noropi.

/rwpi, /norwpi

/rwpi specifies that the code in the input file is Read-Write Position-Independent (RWPI). The default is /norwpi.

/pid, /nopid

Are synonyms for /rwpi and /norwpi.

/fpic, /nofpic

/fpic specifies that the code in the input file is read-only independent and references to addresses are suitable for use in a Linux shared object. The default is /nofpic.

/hardfp, /softfp

Requests hardware or software floating-point linkage. This enables the procedure call standard to be specified separately from the version of the floating-point hardware available through the --fpu option. It is still possible to specify the procedure call standard by using the --fpu option, but ARM recommends you use --apcs. If floating-point support is not permitted (for example, because --fpu=none is specified, or because of other means), then /hardfp and /softfp are ignored. If floating-point support is permitted and the softfp calling convention is used (--fpu=softvfp or --fpu=softvfp+fp-armv8), then /hardfp gives an error.

/softfp is not supported for AArch64 state.

Usage

This option specifies whether you are using the Procedure Call Standard for the ARM Architecture (AAPCS). It can also specify some attributes of code sections.

The AAPCS forms part of the Base Standard Application Binary Interface for the ARM Architecture (BSABI) specification. By writing code that adheres to the AAPCS, you can ensure that separately compiled and assembled modules can work together.

Note:

AAPCS qualifiers do not affect the code produced by armasm. They are an assertion by the programmer that the code in the input file complies with a particular variant of AAPCS. They cause attributes to be set in the object file produced by armasm. The linker uses these attributes to check compatibility of files, and to select appropriate library variants.

Example

armasm --cpu=8-A.32 --apcs=/inter/hardfp inputfile.s

Related information

Procedure Call Standard for the ARM Architecture

Application Binary Interface (ABI) for the ARM Architecture

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