Register Move Functionality

Versal ACAP AIE-ML Architecture Manual (AM020)

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1.0 English

The register move capabilities of the AIE-ML are covered in this section (refer to the Register Files section for a description of the naming of register types.

  • Scalar to scalar:
    • Move scalar values between R, M, P, and special registers.
    • Move immediate values to R, M, P, and special registers.
    • Move a scalar value to/from an AXI4-Stream.
  • Vector to vector: Move one 128-bit V-register to an arbitrary V-register in one cycle. It also applies to the 256-bit W-register and the 512-bit X-register. However, vector sizes must be the same in all cases.
  • Accumulator to accumulator: Move one 512-bit accumulator (AM) register to another AM-register in one cycle. There is also register BM to BM accumulator register move (1024 bits).
  • Vector to accumulator: there are three possibilities:
    • Up shift path takes 16 or 32-bit vector values and writes into an accumulator.
    • Use the normal multiplication datapath and multiply each value by a constant value of 1.
    • Move between BM and X registers.
  • Accumulator to vector: Shift-round saturate datapath moves the accumulator to a vector register. There is also a direct register move from accumulator to vector register.
  • Accumulator to cascade stream and cascade to accumulator: Cascade stream connects the AIE-MLs in the array in a chain and allows the AIE-MLs to transfer an accumulator register (512-bit) from one to the next. A small two-deep 512-bit wide FIFO on both the input and output streams allows storing up to four values in the FIFOs between the AIE-MLs.
  • Scalar to vector: Moves a scalar value from an R-register to a vector register. Different from AI Engine where most operations were on the 128-bit granularity except for shift element operation, only operations on 512-bit registers are allowed in AIE-MLs.
  • Vector to scalar: Extracts an arbitrary 8, 16, or 32-bit value from a 512-bit vector register and writes results into a scalar R-register.