SVE2

The Armv9 Scalable Vector Extensions verision 2 (SVE2) provide a variable-witdh SIMD capability for AArch64 systems.

Resources

• Arm Armv9-A A64 Instruction Set Architecture - https://developer.arm.com/documentation/ddi0602/2021-12/
• Introduction to SVE2 - https://developer.arm.com/documentation/102340/0001/?lang=en
• Intrinsics - Arm C Language Extensions for SVE (ACLE) - https://developer.arm.com/documentation/100987/latest
• SVE Coding Considerations with Arm Compiler - Note that this documentation is specific to Arm's own compiler, but most of it will be applicable to other compilers including gcc - https://developer.arm.com/documentation/100748/0616/SVE-Coding-Considerations-with-Arm-Compiler

Building SVE2 Code

C Compiler Options

To build code that includes SVE2 instructions, you will need to instruct the complier or assembler to emit code for an Armv8a processor that also understands the SVE2 instructions; this is performed using the -march= option (which is read as "machine architecture"). The architecture specificaion for this target is currently "armv8-a+sve2":

gcc -march=armv8-a+sve2 ...

Remember that in order to invoke the autovectorizer in GCC version 11, you must use -O3:

gcc -O3 -march=armv8-a+sve2 ...

Using SVE2 Intrinsics Header Files

To use SVE2 intrinsics in a C program, include the header file arm_sve.h:

#include <arm_sve2.h>

Running SVE2 Code

To run SVE2 code on an Armv8 system, you can use the QEMU usermode system. This will trap SVE2 instructions and emulate them in software, while executing Armv8a instructions directly on the hardware:

qemu-aarch64 ./binary

Running AArch64 code on x86_64
The QMEU user mode software can also be used to run AArch64 code on an x86_64 system (albeit slowly). However, this requires a full AArch64 userspace (applications and tools, such as ld) to be installed on the x86_64 system.