Most VFP and the shared instructions are available in all
versions of the VFP architecture. Where this is not true, the descriptions
of the instructions specify the applicable VFP architecture versions.
VFPv3 has variants that do not support all VFPv3 registers
and floating-point data types. VFPv3 with half-precision extension
and fused multiply-add extension is called VFPv4. There is a single-precision
only version of VFPv4, called FPv4-SP.
For details of the implemented VFP architecture and variant, you must always
refer to the Technical Reference Manual for your processor. To get VFP, you must specify the
FPU or have it implicit in the processor specified with
VFP instructions, including the half-precision and fused multiply-add
instructions, are treated as Undefined Instructions on systems that do not support the
necessary architecture extension. Even on systems that support VFP, the instructions are
undefined if the necessary coprocessors are not enabled in the Coprocessor Access Control
Register (CP15 CPACR).