Appendix D

NEON Intrinsics and Instructions

This appendix contains information on, and a list of instructions used with, the NEON engine. Data types, lane types, and intrinsics are listed.

DATA TYPES

Table D-1 lists the different data types supported on the NEON engine, and the corresponding C data types.

TABLE D-1: NEON Data Types

LANE TYPES

Table D-2 lists the different lane types per class, and the amount of possible types for each class.

TABLE D-2: Data Lane Types

ASSEMBLY INSTRUCTIONS

Table D-3 contains a list of NEON instructions, as well as a brief description of each instruction.

TABLE D-3: NEON Instructions

INTRINSIC NAMING CONVENTIONS

Intrinsics provide an elegant way to write NEON instructions using C. NEON intrinsics are created using the following structure:

v[q][r]name[u][n][q][_lane][_n][_result]_type

where:

• q indicates a saturating operation.
• r indicates a rounding operation.
• name is the descriptive name of the operation.
• u indicates signed-to-unsigned saturation.
• n indicates a narrowing operation.
• q indicates an operation on 128-bit vectors.
• _n indicates a scalar operand supplied as an argument.
• _lane indicates a scalar operand taken from the lane of a vector.
• result is the result type in short form.

For example, vmul_s16 multiplies two vectors of signed 16-bit values and is equivalent to VMUL.I16. Some examples in C include:

uint32x4_t vec128 = vld1q_u32(i); // Load 4 32-bit values
uint8x8_t vadd_u8 (uint8x8_t,
    uint8x8_t); //Add two lanes
int8x16_t vaddq_s8 (int8x16_t, int8x16_t); //Saturating add two lanes