Toolchains#

heliaPROFILER builds firmware through NSX, which supports three Cortex-M cross-compilers. The choice of toolchain affects build time, binary size, and inference performance.

Supported toolchains#

Selection happens via:

hpx profile model.tflite --toolchain armclang

or in YAML:

target:
  toolchain: armclang

The default is arm-none-eabi-gcc, which is what gcc aliases to.

How heliaPROFILER drives the toolchain#

The selected toolchain flows through to NSX:

hpx profile --toolchain X
   └─► firmware build stage
       └─► nsx configure --toolchain X

GCC is special-cased: when arm-none-eabi-gcc/gcc is selected the profiler omits the --toolchain flag entirely so NSX uses its default GCC configuration. armclang and atfe are passed through explicitly.

The profiler also probes the toolchain for binary size analysis using fromelf (armclang/ATfE) or arm-none-eabi-size (GCC), so both binaries must be on PATH.

GCC (default)#

Free, widely available, well-documented.

Install#

# Download from https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
# Extract to /Applications/ArmGNUToolchain/<version>/
export PATH="/Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin:$PATH"

sudo apt install gcc-arm-none-eabi
# Or download a newer release from developer.arm.com

Verify:

arm-none-eabi-gcc --version
arm-none-eabi-size --version

When to use GCC#

• First-time setup or CI on machines without a paid Arm Compiler license.
• Cross-platform build reproducibility — works the same on all OSes.
• The default heliaRT prebuilt archive (libhelia-rt-gcc.a) is GCC-built, so no extra distribution download is needed.

armclang (Arm Compiler 6)#

Commercial Arm Compiler 6. Generally produces faster code than GCC on Cortex-M55 workloads, particularly for MVE-heavy kernels.

Install#

armclang ships with Arm Development Studio or the standalone Arm Compiler for Embedded. A license is required.

# Add the toolchain bin/ to PATH
export PATH="/path/to/ArmCompilerForEmbedded/<version>/bin:$PATH"

# Point at the license server (or an offline license file)
export ARMLMD_LICENSE_FILE="<port>@<server>"

Verify:

armclang --version
fromelf --version

When to use armclang#

• You have an Arm Compiler license available.
• You're optimizing for cycle count on Apollo510 / Cortex-M55.
• You want to validate that performance numbers replicate across toolchains before committing to one.

ATfE (Arm Toolchain for Embedded)#

Arm's newer LLVM-based toolchain. Free and open-source. Currently in preview within heliaPROFILER.

Install#

Download from developer.arm.com and add the bin/ to PATH.

export PATH="/path/to/atfe/<version>/bin:$PATH"

# ATfE binaries
atfe --version
fromelf --version

Caveats#

Toolchain comparison#

KWS reference model on Apollo510 EVB, 100 iterations, default counter set. Numbers come from results/results_*/summary.json.

armclang is consistently ~5–7% faster on this model. The exact gain depends heavily on the operator mix and how MVE-friendly the kernels are. Reproduce on your own model with the toolchain comparison example.

Switching toolchains mid-experiment#

# Same model, three toolchains, three result directories
hpx profile model.tflite --toolchain gcc      --output-dir results/gcc
hpx profile model.tflite --toolchain armclang --output-dir results/armclang
hpx profile model.tflite --toolchain atfe     --output-dir results/atfe

The work directory is not shared between toolchains — each run re-configures and re-builds from scratch.

Troubleshooting#