Build option reference

This page lists the heliaRT integration options defined by the repository. Compiler flags, board configuration and options belonging to heliaCORE or upstream build tools have their own contracts. Start with Build configuration for the decisions behind these settings.

Root CMake options

Set cache options before add_subdirectory(helia-rt). The root CMake file and source manifest are authoritative.

Option	Default	Purpose
HELIA_RT_ENABLE_HELIA	OFF	Build helia_rt::helia; provide an ns-cmsis-nn dependency target.
HELIA_RT_ENABLE_CMSIS_NN	OFF	Build helia_rt::cmsis_nn; provide an upstream CMSIS-NN target.
HELIA_RT_NSCMSISNN_TARGET	Empty, discover target	Explicit kernel dependency target for HELIA.
HELIA_RT_CMSISNN_TARGET	Empty, discover target	Explicit kernel dependency target for CMSIS-NN.
HELIA_RT_BUILD_TYPE	release_with_logs	debug, release_with_logs, or release; controls assertions and error strings.
HELIA_RT_GLOBAL_KERNEL_OPTIMIZE	SPEED	Global HELIA profile: SPEED or SIZE.
HELIA_RT_CONV_OPT	Empty, inherit global	Convolution family override: SPEED or SIZE.
HELIA_RT_FC_OPT	Empty, inherit global	Fully connected override: SPEED or SIZE.
HELIA_RT_STATIC_MEMORY	ON	Export TF_LITE_STATIC_MEMORY.
HELIA_RT_USE_COMPRESSION	OFF	Export USE_TFLM_COMPRESSION; enabling the flag alone does not convert a model to a supported compressed representation.
HELIA_RT_DISABLE_X86_NEON	OFF	Export TF_LITE_DISABLE_X86_NEON for applicable host builds.
HELIA_RT_CORE_OPT	-Os	Compiler optimization option applied to common runtime sources.
HELIA_RT_KERNEL_OPT	-O2	Compiler optimization option applied to selected kernel sources.
HELIA_RT_THIRD_PARTY_OPT	-O2	Declared for third-party optimization; the root build does not apply it to a separate third-party source set.
HELIA_RT_CXX_STANDARD	17	Requested C++ standard; cache choices are 14 and 17.
HELIA_RT_EXTRA_DEFINES	Empty	Extra compile definitions exported by the runtime target.
HELIA_RT_PROVIDE_DEBUG_LOG	ON	Compile the default logging implementation; turn off when the platform supplies it.
HELIA_RT_ENABLE_RECORDING	OFF	Include recording allocators for arena auditing.
HELIA_RT_ENABLE_TEST_HELPERS	OFF	Include mock/test helper sources for test harnesses.
HELIA_RT_ENABLE_ETHOSU	OFF	Enable Ethos-U custom-op dispatch; the application must supply and initialize the driver.

helia_rt::reference is always available. Enabling multiple backend targets makes multiple libraries available; link the one selected for an application rather than linking duplicate runtime implementations.

Float inputs ARM_NN_ENABLE_F32/F16 belong to the kernel dependency. Set them before that dependency is configured. RT reads the resolved features; see Floating point.

neuralSPOT-X wrapper

The NSX wrapper supplies the application target nsx::helia_rt and owns several root settings.

Option	Default	Purpose
NSX_HELIA_RT_BACKEND	helia	helia, cmsis_nn or reference.
HELIA_RT_VARIANT	release-with-logs	debug, release-with-logs or release; maps to root build type.
NSX_HELIA_RT_ENABLE_ETHOSU	OFF	Wrapper-owned Ethos-U enable switch. Use this instead of the root option.
HELIA_RT_TFLM_ROOT	Resolved repository root	Override runtime source location for bundle layouts.
HELIA_RT_NSCMSISNN_TARGET	nsx::cmsis_nn when unset	HELIA dependency target.
HELIA_RT_CMSISNN_TARGET	Required for CMSIS-NN backend	An upstream-compatible CMSIS-NN target, not the HELIA kernel target.

The wrapper forces static memory on, disables the root default logging source and supplies platform logging glue. It selects the root backend and maps the build flavor. Root profile and recording settings remain useful source-build controls.

NSX_BOARD_FLAGS_TARGET and NSX_SOC_FAMILY are required board-provided integration inputs. HELIA_RT_FLOAT32_ENABLED, HELIA_RT_FLOAT16_ENABLED and HELIA_RT_TARGET_HAS_MVE_FP report resolved capabilities; they are not feature requests.

Zephyr Kconfig

The source module’s Kconfig exposes the following application settings. Generated prebuilt bundles have their own module configuration; do not assume source-module options can alter their archive.

Setting	Meaning
CONFIG_HELIA_RT	Enable the runtime source module and its C++ requirements.
CONFIG_HELIA_RT_BACKEND_HELIA	HELIA backend; requires Ambiq SoC family and ns-cmsis-nn.
CONFIG_HELIA_RT_BACKEND_CMSIS_NN	Upstream CMSIS-NN backend; requires Cortex-M and CMSIS-NN.
CONFIG_HELIA_RT_BACKEND_REFERENCE	Reference backend.
CONFIG_HELIA_RT_KERNEL_OPTIMIZE_SPEED	Global HELIA SPEED profile, the profile default.
CONFIG_HELIA_RT_KERNEL_OPTIMIZE_SIZE	Global HELIA SIZE profile.
CONFIG_HELIA_RT_ENABLE_RECORDING	Recording allocator sources.
CONFIG_HELIA_RT_ENABLE_TEST_HELPERS	Test/mock helper sources.

The backend choice defaults to HELIA for SOC_FAMILY_AMBIQ && NS_CMSIS_NN, then CMSIS-NN for SOC_FAMILY_AMBIQ && CMSIS_NN, otherwise Reference. Inspect the final configuration when depending on defaults. Float options CONFIG_NS_CMSIS_NN_ENABLE_F32/F16 belong to the dependency; HELIA provides weak implied defaults.

Make integration

These variables are consumed by the Makefile and HELIA extension.

Variable	Purpose
TARGET	Build platform, for example cortex_m_generic; a native build is a host build.
TARGET_ARCH	Architecture configuration such as cortex-m4+fp or cortex-m55.
TOOLCHAIN	Compiler path; the release builder accepts gcc, armclang, atfe.
OPTIMIZED_KERNEL_DIR	helia, cmsis_nn or empty/reference specialization.
BUILD_TYPE	debug, release_with_logs or release.
GLOBAL_KERNEL_OPTIMIZE	Global profile; default SPEED.
CONV_OPT, FC_OPT	Family overrides, each defaulting to global.
NS_CMSIS_NN_COMMIT	Kernel source revision used by the downloader; default is the pin in helia.inc.
NS_CMSIS_NN_PATH	Existing kernel checkout instead of the default download location.
NS_CMSIS_NN_LIBS	External kernel link libraries instead of compiling the dependency sources. Requires kernel and CMSIS header paths.
CMSIS_PATH	CMSIS header location; pass explicitly as a Make command-line assignment when using the external-library path.
CMSIS_NN_USE_REQUANTIZE_INLINE_ASSEMBLY	Optional kernel requantization implementation switch; the HELIA extension forwards a non-empty value to C/C++ compilation.

Float definitions in the HELIA Make path are derived by helia.inc from the target. They are not the CMake feature-selection interface. External libraries must match those definitions.

For profile examples, see Kernel profiles. For compiler/ABI selection and the release script’s flags, see Toolchains and artifacts.