9.4.1 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, arm7tdmi-s, arm8, arm810, strongarm, strongarm1, strongarm110, strongarm1100, strongarm1110, arm9, arm920, arm920t, arm922t, arm940t, arm9tdmi, fa526 (Faraday FA526 processor), fa626 (Faraday FA626 processor), arm9e, arm926e, arm926ej-s, arm946e-r0, arm946e, arm946e-s, arm966e-r0, arm966e, arm966e-s, arm968e-s, arm10t, arm10tdmi, arm10e, arm1020, arm1020t, arm1020e, arm1022e, arm1026ej-s, fa606te (Faraday FA606TE processor), fa616te (Faraday FA616TE processor), fa626te (Faraday FA626TE processor), fmp626 (Faraday FMP626 processor), fa726te (Faraday FA726TE processor), arm1136j-s, arm1136jf-s, arm1156t2-s, arm1156t2f-s, arm1176jz-s, arm1176jzf-s, mpcore, mpcorenovfp, cortex-a5, cortex-a7, cortex-a8, cortex-a9, cortex-a15, cortex-a17, cortex-a32, cortex-a35, cortex-a53, cortex-a55, cortex-a57, cortex-a72, cortex-a73, cortex-a75, cortex-a76, cortex-a76ae, cortex-a77, ares, cortex-r4, cortex-r4f, cortex-r5, cortex-r7, cortex-r8, cortex-r52, cortex-m35p, cortex-m33, cortex-m23, cortex-m7, cortex-m4, cortex-m3, cortex-m1, cortex-m0, cortex-m0plus, exynos-m1, marvell-pj4, marvell-whitney, neoverse-n1, xgene1, xgene2, ep9312 (ARM920 with Cirrus Maverick coprocessor), i80200 (Intel XScale processor) iwmmxt (Intel XScale processor with Wireless MMX 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.

Multiple extensions may be specified, separated by a +. The extensions should be specified in ascending alphabetical order.

Some extensions may be restricted to particular architectures; this is documented in the list of extensions below.

Extension mnemonics may also be removed from those the assembler accepts. This is done be prepending no to the option that adds the extension. Extensions that are removed should be listed after all extensions which have been added, again in ascending alphabetical order. For example, -mcpu=ep9312+nomaverick is equivalent to specifying -mcpu=arm920.

The following extensions are currently supported: bf16 (BFloat16 extensions for v8.6-A architecture), i8mm (Int8 Matrix Multiply extensions for v8.6-A architecture), crc crypto (Cryptography Extensions for v8-A architecture, implies fp+simd), dotprod (Dot Product Extensions for v8.2-A architecture, implies fp+simd), fp (Floating Point Extensions for v8-A architecture), fp16 (FP16 Extensions for v8.2-A architecture, implies fp), fp16fml (FP16 Floating Point Multiplication Variant Extensions for v8.2-A architecture, implies fp16), idiv (Integer Divide Extensions for v7-A and v7-R architectures), iwmmxt, iwmmxt2, xscale, maverick, mp (Multiprocessing Extensions for v7-A and v7-R architectures), os (Operating System for v6M architecture), predres (Execution and Data Prediction Restriction Instruction for v8-A architectures, added by default from v8.5-A), sb (Speculation Barrier Instruction for v8-A architectures, added by default from v8.5-A), sec (Security Extensions for v6K and v7-A architectures), simd (Advanced SIMD Extensions for v8-A architecture, implies fp), virt (Virtualization Extensions for v7-A architecture, implies idiv), pan (Privileged Access Never Extensions for v8-A architecture), ras (Reliability, Availability and Serviceability extensions for v8-A architecture), rdma (ARMv8.1 Advanced SIMD extensions for v8-A architecture, implies simd) 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, armv6, armv6j, armv6k, armv6z, armv6kz, armv6-m, armv6s-m, armv7, armv7-a, armv7ve, armv7-r, armv7-m, armv7e-m, armv8-a, armv8.1-a, armv8.2-a, armv8.3-a, armv8-r, armv8.4-a, armv8.5-a, armv8-m.base, armv8-m.main, armv8.1-m.main, armv8.6-a, iwmmxt, iwmmxt2 and xscale. If both -mcpu and -march are specified, the assembler will use the setting for -mcpu.

The architecture option can be extended with a set extension options. These extensions are context sensitive, i.e. the same extension may mean different things when used with different architectures. When used together with a -mfpu option, the union of both feature enablement is taken. See their availability and meaning below:

For armv5te, armv5texp, armv5tej, armv6, armv6j, armv6k, armv6z, armv6kz, armv6zk, armv6t2, armv6kt2 and armv6zt2:

+fp: Enables VFPv2 instructions. +nofp: Disables all FPU instrunctions.

For armv7:

+fp: Enables VFPv3 instructions with 16 double-word registers. +nofp: Disables all FPU instructions.

For armv7-a:

+fp: Enables VFPv3 instructions with 16 double-word registers. +vfpv3-d16: Alias for +fp. +vfpv3: Enables VFPv3 instructions with 32 double-word registers. +vfpv3-d16-fp16: Enables VFPv3 with half precision floating-point conversion instructions and 16 double-word registers. +vfpv3-fp16: Enables VFPv3 with half precision floating-point conversion instructions and 32 double-word registers. +vfpv4-d16: Enables VFPv4 instructions with 16 double-word registers. +vfpv4: Enables VFPv4 instructions with 32 double-word registers. +simd: Enables VFPv3 and NEONv1 instructions with 32 double-word registers. +neon: Alias for +simd. +neon-vfpv3: Alias for +simd. +neon-fp16: Enables VFPv3, half precision floating-point conversion and NEONv1 instructions with 32 double-word registers. +neon-vfpv4: Enables VFPv4 and NEONv1 with Fused-MAC instructions and 32 double-word registers. +mp: Enables Multiprocessing Extensions. +sec: Enables Security Extensions. +nofp: Disables all FPU and NEON instructions. +nosimd: Disables all NEON instructions.

For armv7ve:

+fp: Enables VFPv4 instructions with 16 double-word registers. +vfpv4-d16: Alias for +fp. +vfpv3-d16: Enables VFPv3 instructions with 16 double-word registers. +vfpv3: Enables VFPv3 instructions with 32 double-word registers. +vfpv3-d16-fp16: Enables VFPv3 with half precision floating-point conversion instructions and 16 double-word registers. +vfpv3-fp16: Enables VFPv3 with half precision floating-point conversion instructions and 32 double-word registers. +vfpv4: Enables VFPv4 instructions with 32 double-word registers. +simd: Enables VFPv4 and NEONv1 with Fused-MAC instructions and 32 double-word registers. +neon-vfpv4: Alias for +simd. +neon: Enables VFPv3 and NEONv1 instructions with 32 double-word registers. +neon-vfpv3: Alias for +neon. +neon-fp16: Enables VFPv3, half precision floating-point conversion and NEONv1 instructions with 32 double-word registers. double-word registers. +nofp: Disables all FPU and NEON instructions. +nosimd: Disables all NEON instructions.

For armv7-r:

+fp.sp: Enables single-precision only VFPv3 instructions with 16 double-word registers. +vfpv3xd: Alias for +fp.sp. +fp: Enables VFPv3 instructions with 16 double-word registers. +vfpv3-d16: Alias for +fp. +vfpv3xd-fp16: Enables single-precision only VFPv3 and half floating-point conversion instructions with 16 double-word registers. +vfpv3-d16-fp16: Enables VFPv3 and half precision floating-point conversion instructions with 16 double-word registers. +idiv: Enables integer division instructions in ARM mode. +nofp: Disables all FPU instructions.

For armv7e-m:

+fp: Enables single-precision only VFPv4 instructions with 16 double-word registers. +vfpvf4-sp-d16: Alias for +fp. +fpv5: Enables single-precision only VFPv5 instructions with 16 double-word registers. +fp.dp: Enables VFPv5 instructions with 16 double-word registers. +fpv5-d16": Alias for +fp.dp. +nofp: Disables all FPU instructions.

For armv8-m.main:

+dsp: Enables DSP Extension. +fp: Enables single-precision only VFPv5 instructions with 16 double-word registers. +fp.dp: Enables VFPv5 instructions with 16 double-word registers. +nofp: Disables all FPU instructions. +nodsp: Disables DSP Extension.

For armv8.1-m.main:

+dsp: Enables DSP Extension. +fp: Enables single and half precision scalar Floating Point Extensions for Armv8.1-M Mainline with 16 double-word registers. +fp.dp: Enables double precision scalar Floating Point Extensions for Armv8.1-M Mainline, implies +fp. +mve: Enables integer only M-profile Vector Extension for Armv8.1-M Mainline, implies +dsp. +mve.fp: Enables Floating Point M-profile Vector Extension for Armv8.1-M Mainline, implies +mve and +fp. +nofp: Disables all FPU instructions. +nodsp: Disables DSP Extension. +nomve: Disables all M-profile Vector Extensions.

For armv8-a:

+crc: Enables CRC32 Extension. +simd: Enables VFP and NEON for Armv8-A. +crypto: Enables Cryptography Extensions for Armv8-A, implies +simd. +sb: Enables Speculation Barrier Instruction for Armv8-A. +predres: Enables Execution and Data Prediction Restriction Instruction for Armv8-A. +nofp: Disables all FPU, NEON and Cryptography Extensions. +nocrypto: Disables Cryptography Extensions.

For armv8.1-a:

+simd: Enables VFP and NEON for Armv8.1-A. +crypto: Enables Cryptography Extensions for Armv8-A, implies +simd. +sb: Enables Speculation Barrier Instruction for Armv8-A. +predres: Enables Execution and Data Prediction Restriction Instruction for Armv8-A. +nofp: Disables all FPU, NEON and Cryptography Extensions. +nocrypto: Disables Cryptography Extensions.

For armv8.2-a and armv8.3-a:

+simd: Enables VFP and NEON for Armv8.1-A. +fp16: Enables FP16 Extension for Armv8.2-A, implies +simd. +fp16fml: Enables FP16 Floating Point Multiplication Variant Extensions for Armv8.2-A, implies +fp16. +crypto: Enables Cryptography Extensions for Armv8-A, implies +simd. +dotprod: Enables Dot Product Extensions for Armv8.2-A, implies +simd. +sb: Enables Speculation Barrier Instruction for Armv8-A. +predres: Enables Execution and Data Prediction Restriction Instruction for Armv8-A. +nofp: Disables all FPU, NEON, Cryptography and Dot Product Extensions. +nocrypto: Disables Cryptography Extensions.

For armv8.4-a:

+simd: Enables VFP and NEON for Armv8.1-A and Dot Product Extensions for Armv8.2-A. +fp16: Enables FP16 Floating Point and Floating Point Multiplication Variant Extensions for Armv8.2-A, implies +simd. +crypto: Enables Cryptography Extensions for Armv8-A, implies +simd. +sb: Enables Speculation Barrier Instruction for Armv8-A. +predres: Enables Execution and Data Prediction Restriction Instruction for Armv8-A. +nofp: Disables all FPU, NEON, Cryptography and Dot Product Extensions. +nocryptp: Disables Cryptography Extensions.

For armv8.5-a:

+simd: Enables VFP and NEON for Armv8.1-A and Dot Product Extensions for Armv8.2-A. +fp16: Enables FP16 Floating Point and Floating Point Multiplication Variant Extensions for Armv8.2-A, implies +simd. +crypto: Enables Cryptography Extensions for Armv8-A, implies +simd. +nofp: Disables all FPU, NEON, Cryptography and Dot Product Extensions. +nocryptp: Disables Cryptography Extensions.

-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, vfpv2, vfpv3, vfpv3-fp16, vfpv3-d16, vfpv3-d16-fp16, vfpv3xd, vfpv3xd-d16, vfpv4, vfpv4-d16, fpv4-sp-d16, fpv5-sp-d16, fpv5-d16, fp-armv8, arm1020t, arm1020e, arm1136jf-s, maverick, neon, neon-vfpv3, neon-fp16, neon-vfpv4, neon-fp-armv8, crypto-neon-fp-armv8, neon-fp-armv8.1 and crypto-neon-fp-armv8.1.

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 assemble for VFP instructions; for earlier architectures the default is to assemble for FPA instructions.

-mfp16-format=format

This option specifies the half-precision floating point format to use when assembling floating point numbers emitted by the .float16 directive. The following format options are recognized: ieee, alternative. If ieee is specified then the IEEE 754-2008 half-precision floating point format is used, if alternative is specified then the Arm alternative half-precision format is used. If this option is set on the command line then the format is fixed and cannot be changed with the float16_format directive. If this value is not set then the IEEE 754-2008 format is used until the format is explicitly set with the float16_format directive.

-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. It also affects the behaviour of the ADR and ADRL pseudo opcodes.

-mimplicit-it=never

-mimplicit-it=always

-mimplicit-it=arm

-mimplicit-it=thumb

The -mimplicit-it option controls the behavior of the assembler when conditional instructions are not enclosed in IT blocks. There are four possible behaviors. If never is specified, such constructs cause a warning in ARM code and an error in Thumb-2 code. If always is specified, such constructs are accepted in both ARM and Thumb-2 code, where the IT instruction is added implicitly. If arm is specified, such constructs are accepted in ARM code and cause an error in Thumb-2 code. If thumb is specified, such constructs cause a warning in ARM code and are accepted in Thumb-2 code. If you omit this option, the behavior is equivalent to -mimplicit-it=arm.

-mapcs-26

-mapcs-32

These options specify 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 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.

-mfloat-abi=abi

This option specifies that the output generated by the assembler should be marked as using specified floating point ABI. The following values are recognized: soft, softfp and hard.

-meabi=ver

This option specifies which EABI version the produced object files should conform to. The following values are recognized: gnu, 4 and 5.

-EB

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

Note: If a program is being built for a system with big-endian data and little-endian instructions then it should be assembled with the -EB option, (all of it, code and data) and then linked with the --be8 option. This will reverse the endianness of the instructions back to little-endian, but leave the data as big-endian.

-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).

--fix-v4bx

Allow BX instructions in ARMv4 code. This is intended for use with the linker option of the same name.

-mwarn-deprecated

-mno-warn-deprecated

Enable or disable warnings about using deprecated options or features. The default is to warn.

-mccs

Turns on CodeComposer Studio assembly syntax compatibility mode.

-mwarn-syms

-mno-warn-syms

Enable or disable warnings about symbols that match the names of ARM instructions. The default is to warn.