4.1 Compiler options

Describes the subset of ARM® Compiler command-line options most likely to be of interest to users developing code to take advantage of SVE.

See the armclang Reference Guide for information about the full range of supported options.

Options controlling compiler operation

-S

Outputs assembly code, rather than object code.

Produces a text .s file containing annotated assembly code.

-c

Performs the compilation step, but does not invoke armlink to perform the link step.

Produces an ELF object .o file. To later link object files into an executable binary, run armclang again, passing in the object files.

-o file
Specifies the name of the output file.
-std=lang

Compiles for the specified language standard, for example -std=c90 or -std=c++98.

See the armclang Reference Guide for details of the supported variants, and the differences between them.

--target=arch-vendor-os-abi

Generates code for the selected target.

ARM Compiler supports both AArch32 and AArch64 targets. However, SVE is an extension to ARMv8-A AArch64. Therefore the only supported target for this release is aarch64-arm-none-eabi

-Xlinker opt

Specifies a linker command-line option to pass to the linker when a link step is being performed after compilation.

When compiling binaries to execute on the AEMv8-A Base Fixed Virtual Platform (FVP) base model, use this option to specify the location in memory to load and run the binary. The RAM base address for this FVP is 0x80000000. You must therefore specify the -Xlinker "--ro_base=0x80000000" option for any armclang invocation that performs the link stage.

Options controlling compiler optimization

-march=name[+[no]feature]

Targets an architecture profile, generating generic code that runs on any processor of that architecture.

Append the +sve feature to enable SVE, or omit to disable.

For example, -march=armv8.2+sve enables the ARMv8.2 architecture profile plus SVE support.

Use -march=list to display a list of all the supported architectures for your target.

-Olevel

Specifies the level of optimization to use when compiling source files.

SVE auto-vectorization occurs only at the –O2 and –O3 levels. Auto-vectorization is identical at both levels, however –O3 results in higher general code optimization.

The –Ofast option is equivalent to -O3 -ffp-mode=fast, and can produce faster code if fast math optimizations are appropriate for your application.

The -Omax option is equivalent to -Ofast plus other aggressive optimizations. It specifically targets performance optimization.

-ffp-mode=fast

Enable aggressive floating-point optimizations.

The compiler can perform code optimizations and transformations that, although arithmetically correct, might not be in strict compliance with IEEE or ISO rules concerning mathematical operations.

This option can produce significantly faster code. For example, it allows the compiler to use the SVE FADDV instruction to perform fast parallel additions across a vector. The FADDV instruction is faster than the FADDA instruction because FADDA performs all additions across the vector in strict sequence. Take care to ensure that your algorithms do not depend on strict IEEE or ISO mathematical rules. The optimizations applied here are not guaranteed to produce bitwise identical results when compared with less aggressively optimized code.

Informational options

--help
Describes the most common options supported by ARM Compiler.
--vsn, --version
Displays version information and license details.
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