Compile for SVE

Compiling for SVE with GNU

Below are example commands to compile an application with support for SVE instructions using the GNU Toolchain:

C

For GCC, use the following command:

    

        
        
            gcc -march=armv8-a+sve myapp.c -o myapp_c.out
        
    

Fortran

For Fortran, use the following command:

    

        
        
            gfortran -march=armv8-a+sve myapp.f90 -o myapp_f90.out
        
    

Autovectorization

With GCC autovectorization is enabled with the -03 option. To disable autovectorization, use -fno-tree-vectorize compiler option.

Compare the disassembly of a simple program shown below with and without the use of autovectorization:

Note the use of double-word register d0, d1 instead of SVE registers z0.d and z1 when you disable vectorization.

Compiler insights

With GCC, the use of compiler option -fopt-info-vec returns which loops were vectorized. To return which loop failed to vectorize, use the -fopt-info-vec-missed compiler option.

In this example, the compiler reports the vectorization of loop line 3.

Use Arm Performance Libraries

The Arm Performance Libraries include generic and target-specific SVE optimizations of common math operations used in HPC. To link your application with these libraries and GCC, use the predefined environment variables ARMPL_INCLUDES and ARMPL_LIBRARIES. The environment variables are set by the Arm Performance Libraries module files.

Refer to the Arm Performance Libraries install guide for more information.

    

        
        
            gcc -O3 -march=armv8-a+sve -I $ARMPL_INCLUDES dgemm.c -o dgemm.out -L $ARMPL_LIBRARIES -larmpl
        
    

Compiling for SVE with Arm Compiler for Linux

Shown below are example commands to compile an application with support for SVE instructions using Arm Compiler for Linux:

Arm C/C++ Compiler

    

        
        
            armclang -march=armv8-a+sve myapp.c -o myapp_c.out
        
    

Arm Fortran Compiler

    

        
        
            armflang -march=armv8-a+sve myapp.f90 -o myapp_f90.out
        
    

Compiling for a specific SVE target with Arm Compiler for Linux

If you are compiling for a SVE-capable target, you can use the -march=native compiler option. For specific CPUs with SVE support, use the -mcpu option:

Autovectorization

With Arm Compiler for Linux autovectorization is enabled with the -02 option and above. To disable autovectorization, use -fno-vectorize.

Compiler insights

With Arm Compiler for Linux, the option -Rpass=vector and -Rpass=sve-loop-vectorize return which loops were vectorized. To return the loops that failed to vectorize, use -Rpass-missed=vector.

Use Arm Performance Libraries

To use Arm Performance Libraries with Arm Compiler for Linux use the -armpl=sve option. This ensures the SVE version of the library is used. Example command shown here:

    

        
        
            armclang -O3 -march=armv8-a+sve -armpl=sve dgemm.c -o dgemm.out