If the target has hardware support for NEON technology or an FPU, the highest performance is achieved by passing NEON and FPU parameters and return values in NEON and FPU registers. This is called hardware floating-point linkage. In some situations, using the general-purpose registers for parameter passing might be preferred, to simplify software compatibility between platforms with and without hardware floating-point support. This is called software floating-point linkage.

You cannot mix objects with different floating-point linkage in a single image. Any dynamic libraries loaded while the application is running must also use the same linkage.

Any system that supports both NEON and VFP instructions uses a common register bank for these instructions, therefore configuration options that affect the floating-point calling convention also affect how NEON parameters are passed and returned.