The AI Engine scalar unit supports signed and unsigned integers in 8-, 16, and 32-bit widths, along with some single-precision floating-point for specific operations.
The AI Engine vector unit supports integers and complex integers in 8-, 16-, and 32-bit widths. The vector unit also supports real and complex single-precision floating-point numbers. It also supports accumulator vector data types, with 48 and 80-bit wide elements. Intrinsic functions such as absolute value, addition, subtraction, comparison, multiplication, and MAC operate using these vector data types. Vector data types follow a naming convention that includes:
- the number of elements
- real or complex
- vector type or accumulator type
- bit width
as follows:
aie::vector<[c]([u]int|float)(SizeofElement),NumLanes>
aie::accum<[c](acc|accfloat)(SizeofElements),NumLanes>Optional specifications include:
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NumLanes - Denotes the number of elements in the vector which can be 2, 4, 8, 16, 32, 64, or 128.
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c - Denotes complex data with real and imaginary parts packed together.
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int - denotes integer vector data values.
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float - Denotes single precision floating-point values.
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acc - Denotes accumulator vector data values.
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u - Denotes unsigned. Unsigned only exists for int8 vectors.
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SizeofElement - Denotes the size of the vector data type element.
- 1024-bit integer vector types are vectors of 8-bit, 16-bit, or 32-bit vector elements. These vectors have 16, 32, 64, or 128 lanes.
- 512-bit integer vector types are vectors of 8-bit, 16-bit, 32-bit, or 64-bit vector elements. These vectors have 4, 8, 16, 32, or 64 lanes.
- 256-bit integer vector types are vectors of 8-bit, 16-bit, 32-bit, 64-bit, or 128-bit vector elements. These vectors have 1, 2, 4, 8, 16, or 32 lanes.
- 128-bit integer vector types are vectors of 8-bit, 16-bit, or 32-bit vector elements. These vectors have 2, 4, 8, or 16 lanes.
- Accumulator data types are vectors of 80-bit or 48-bit elements These vectors have 2, 4, 8, or 16 lanes.
The total data-width of the vector data-types can be 128-bit, 256-bit, 512-bit, or 1024-bit. The total data-width of the accumulator data-types can be 320/384-bit or 640/768-bit.
For example, v16int32 is a sixteen element vector of integers with 32 bits. Each element of the vector is referred to as a lane. Using the smallest bit width necessary can improve performance by making good use of registers.