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NEON views of the extension register bank

NEON technology can view the extension register bank as sixteen 128-bit registers, or as thirty-two 64-bit registers, or as a combination of registers from these views.

The 128-bit registers are Q0-Q15. The 64-bit registers are D0-D31.

NEON technology views each register as containing a vector of 1, 2, 4, 8, or 16 elements, all of the same size and type. Individual elements can also be accessed as scalars.

In NEON technology, the 64-bit registers are called doubleword registers and the 128-bit registers are called quadword registers.