7.27 --cpu=name compiler option

Enables code generation for the selected ARM processor or architecture.


Where name is the name of a processor or architecture:
Processor and architecture names are not case-sensitive.
Wildcard characters are not accepted.

Table 7-3 Supported ARM architectures

Architecture Description Example processors
4 ARMv4 without Thumb SA-1100
4T ARMv4 with Thumb ARM7TDMI, ARM9TDMI, ARM720T, ARM740T, ARM920T, ARM922T, ARM940T, SC100
5T ARMv5 with Thumb and interworking -
5TE ARMv5 with Thumb, interworking, DSP multiply, and double-word instructions ARM9E, ARM946E-S, ARM966E-S
ARMv5 with Thumb, interworking, DSP multiply, double-word instructions, and Jazelle® extensions


armcc cannot generate Java bytecodes.
ARM926EJ-S, ARM1026EJ-S, SC200
6 ARMv6 with Thumb, interworking, DSP multiply, double-word instructions, unaligned and mixed-endian support, Jazelle, and media extensions ARM1136J-S, ARM1136JF-S
6-M ARMv6 micro-controller profile with Thumb only, plus processor state instructions Cortex-M1 without OS extensions, Cortex-M0, SC000, Cortex-M0plus
6S-M ARMv6 micro-controller profile with Thumb only, plus processor state instructions and OS extensions Cortex-M1 with OS extensions
6K ARMv6 with SMP extensions MPCore
6T2 ARMv6 with Thumb (Thumb-2 technology) ARM1156T2-S, ARM1156T2F-S
6Z ARMv6 with Security Extensions ARM1176JZF-S, ARM1176JZ-S
7 ARMv7 with Thumb (Thumb-2 technology) only, and without hardware divide -
7-R ARMv7 real-time profile with ARM, Thumb (Thumb-2 technology), DSP support, and 32-bit SIMD support Cortex-R4, Cortex-R4F, Cortex-R7
7-M ARMv7 micro-controller profile with Thumb (Thumb-2 technology) only and hardware divide Cortex-M3, SC300
7E-M ARMv7-M enhanced with DSP (saturating and 32-bit SIMD) instructions Cortex-M4


ARMv7 is not an actual ARM architecture. --cpu=7 denotes the features that are common to the ARMv7-A, ARMv7-R, and ARMv7-M architectures. By definition, any given feature used with --cpu=7 exists on the ARMv7-A, ARMv7-R, and ARMv7-M architectures.


armcc assumes --cpu=ARM7TDMI if you do not specify a --cpu option.
To obtain a full list of architectures and processors, use the --cpu=list option.


The following general points apply to processor and architecture options:
  • Selecting the processor selects the appropriate architecture, Floating-Point Unit (FPU), and memory organization.
  • The supported --cpu values include all current ARM product names or architecture versions.
    Other ARM architecture-based processors, such as the Marvell Feroceon and the Marvell XScale, are also supported.
  • If you specify a processor for the --cpu option, the generated code is optimized for that processor. This enables the compiler to use specific coprocessors or instruction scheduling for optimum performance.
  • If you specify an architecture name for the --cpu option, the generated code can run on any processor supporting that architecture. For example, --cpu=5TE produces code that can be used by the ARM926EJ-S® processor.
  • Some specifications of --cpu imply an --fpu selection.
    For example, when building with the --arm option, --cpu=ARM1136JF-S implies --fpu=vfpv2. Similarly, --cpu=Cortex-R4F implies --fpu=vfpv3_d16.


    Any explicit FPU, set with --fpu on the command line, overrides an implicit FPU.
  • If no --fpu option is specified and no --cpu option is specified, --fpu=softvfp is used.
  • Specifying a processor or architecture that supports Thumb instructions, such as --cpu=ARM7TDMI, 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, unless the processor is a Thumb-only processor, for example Cortex-M4. In this case, --thumb is not required.


    Specifying the target processor or architecture might make the generated object code incompatible with other ARM processors. For example, code generated for architecture ARMv6 might not run on an ARM920T processor, if the generated object code includes instructions specific to ARMv6. Therefore, you must choose the lowest common denominator processor suited to your purpose.
  • If you are building for mixed ARM/Thumb systems for processors that support ARMv4T or ARMv5T, then you must specify the interworking option --apcs=/interwork. By default, this is enabled for processors that support ARMv5T or above.
  • If you build for Thumb, that is with the --thumb option on the command line, the compiler generates as much of the code as possible using the Thumb instruction set. However, the compiler might generate ARM code for some parts of the compilation. For example, if you are generating code for a 16-bit Thumb processor and using VFP, any function containing floating-point operations is compiled for ARM.
  • If the architecture only supports Thumb, you do not have to specify --thumb on the command line. For example, if building for ARMv7-M with --cpu=7-M, you do not have to specify --thumb on the command line, because ARMv7-M only supports Thumb. Similarly, ARMv6-M and other Thumb-only architectures.


You cannot specify both a processor and an architecture on the same command-line.
Related reference
7.6 --apcs=qualifier...qualifier
7.26 --cpu=list
7.67 --fpu=name compiler option
7.149 --thumb
9.14 __smc
Related information
Non-ConfidentialPDF file icon PDF versionARM DUI0375E
Copyright © 2007, 2008, 2011, 2012, 2014 ARM. All rights reserved.